rec.models.rockets FAQ Part 04 - Born Again Rocketeers
Wolfram v.Kiparski
Rec-models-rockets-archive-name: rockets-faq/part04
Posting-Frequency: monthly
Last-modified: 1998 December 29
URL: http://www.ninfinger.org/~sven/rockets/rmrfaq.toc.html
Rec.Models.Rockets Frequently Asked Questions: PART 4 OF 14
BORN AGAIN ROCKETEERS
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4.1 What the heck is a 'Born Again Rocketeer'?
A Born Again Rocketeer (BAR) is a person who started out in model
rocketry in their 'younger' days, dropped out of the hobby for some
number of years, and then came to their senses and got back into it.
BARs are noted for re-entering the hobby with extreme enthusiasm and
much deeper pockets than they had during their first encounter with
the hobby. Actually, the length of time spent away from the hobby is not as
important as the extreme enthusiasm that BARs have when getting back into
rocketry. It's like, we have to make up for lost time or something.
The editor of this FAQ is a BAR (and proud of it :-).
Paul Wolaver <pwol...@sybase.com> wrote this BAR observation:
Be prepared for the BAR phenomenon. Open your wallet. Write off your
weekends. Set aside a room in your house to build rockets.
Buy epoxy.
An informal survey of 49 Born-Again Rocketeers on r.m.r. yielded the
following information:
- average number of years away from the hobby - 18.6
- Why did you get back into rocketry?
The answers varied greatly, but these three were at the top:
1. Involvement with children (33%)
2. 'discovered' rec.models.rockets (12%)
3. wanted to get into HPR after seeing how much the hobby has
changed. (8%)
- current 'mode' of flying rockets
1. model rocketry (49%)
2. high power (20%)
3. high power 'lite' (10%)
- what did you fly first?
Seems like everyone did something different. Estes kits were the
overwhelming majority, with the Big Bertha, Alpha, Alpha III, and
Phoenix all being mentioned more than once or twice.
- what were your old favorites, way back when?
Again, everyone liked something different, and everyone had more
than one single favorite kit. Estes kits figured prominently in
the memories of the surveyed. The Big Bertha, Mars Lander, and
Orbital Transport kits were most popular. A few folks were Centuri
fans, with the Orion kit getting the most votes (2). A few
eschewed the kit scene completely, and someone recalled fond
memories of building ZnS rockets.
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4.2 I have been out of model rockets for many (i.e. <nn>+) years now.
What been happening in the hobby over the past couple of decades?
What's new? What's gone?
4.2.1 Who's Left, Who's Not & Who's New
To sum it up...
Gone: Centuri/Enerjet
Rocket Development Corporation
Space Age Industries
MPC rocket kits
Coaster
'S' Series (short) 18mm motors
Competition Model Rockets (CMR)
AVI motors
Camroc/Cineroc
Flight Systems
Still here: National Association of Rocketry (NAR)
Estes
New: High Power Rocketry, with *BIG* rockets
Tripoli Rocketry Association
MANY new companies
Composite rocket motors are commonplace
Reloadable solid rocket motors
Hybrid rocket motors
Phenolic and fiberglass rocket components
Electronic altimeters, flight computers,....
Much improved rocketry simulation software
And a whole lot more.....
Basically, it's all pretty much the same, or totally different,
depending on your interests. Estes is still Estes. Most of their kits
are still the same materials, etc. The trend for the last 10 years has
been for Estes to sell simpler and simpler kits. There are lots of
plastic nose cones and fin units (already around when you were active
before). There are now kits with pre-slotted body tubes and plastic
fins (as in the Estes E2X series). Lot's of good stuff for beginners
and kids. Estes now makes engines in the 1/2A - D range, all black
powder. Estes has some Large Model Rocket offerings ready, as well.
Read below for details.
Flight Systems (FSI), another motor and kit manufacturer that got its
start in the late 60's, was reported in 1995 to have ceased its
model rocketry operations. They restarted production in 1996, but
within less than a year, Flight Systems appears to be no longer in
business.
Centuri, sadly, 'went away' in 1980. Damon Industries bought both Estes
and Centuri in the 1970's. They operated both companies as independent
units for several years. Finally, Centuri was dissolved and its products
absorbed into Estes. Every now and then an old Centuri kit surfaces
under the Estes banner. An interesting piece of trivia is that the tax
and incorporation laws were more favorable in Arizona (home of Centuri)
than Colorado (home of Estes). So, Damon, on paper, had Centuri acquire
Estes, even though it was Centuri's operations that were eventually shut
down. Damon sold off Estes to a group of investors in the early 90's.
Now for 'who is new'. First, in model rocketry there is a new kid
on the block: Quest. This is Bill Stine, some ex-Centuri people
and others. They are a direct competitor to Estes. They have a line
of kits and engines (A-C). Good quality. Less expensive than Estes.
There are many other smaller companies making and selling model rocket
kits. See Part 02 of the FAQ for addresses. Custom Rockets is another
company with rocket kits similar to those offered by Estes and Quest.
Custom offers quality paper tube/balsa finned kits in the A-D power
range.
Aerotech, LOC/Precision, Rocket R&D, Public Missiles, and North Coast
Rocketry are some new names in the business. These companies cater to both
larger model rocket and high power rocket markets. Estes bought manufacturing
rights to all NCR products in 1995. Estes has announced a line of F/G
rockets (based on NCR designs) to be released in 1996. Estes
may also release a small line of F and G composite motors by 1997. A
newer outfit, Rocket R&D, bought out THOY and another smaller HPR
manufacturer, Cluster R.
Aerotech manufactures both single-use and reloadable composite rocket
motors ranging from C to M total impulse classes. They also offer a few
kits designed for E to G engines.
A couple of outfits make kits using newer technology materials, including
phenolics, fiberglass, and composites. These include Public Missiles (PML),
Rocketman and Dynacom. Be prepared to pay more dollars for the more
advanced materials. A $60-75, 4" diameter, heavy paper tube based kit,
such as manufactured by LOC, might cost $100-125 in a phenolic based
kit, such as produced by PML. A Dynacom fiberglass kit of the same
size might cost closer to $350.
If you were into rocketry in the early 1980's then you probably remember
AAA Model Aviation Fuels. They're still here, with a line of HPR and
Large Model Rocket kits.
If you were into competing you might have been familiar with Competition
Model Rockets (CMR). They are now defunct but there are constant rumors
of a rebirth 'sometime in the near future'. Other companies have stepped
in to fill the space left by the exit of CMR. See the section
'Competition' for some names and addresses. Three new companies are
Apogee Components, Qualified Competition Rockets, and Eclipse Components.
Apogee was started by long-time rocketeer Ed LaCroix. QCR was started by
another long-time rocketeer, Kenneth Brown. Ed has now joined the Aerotech
team and Apogee is now run by Timothy Van Milligan. A new company,
Eclipse Components, has picked up some of the Apogee Components line, except
for the motors. Apogee is still selling those, as well as a new line of kits.
Pratt Hobbies has picked up some of the old CMR product line, and has already
made the CMR egg capsules and nose cones available again.
A lot of the 'neat' Estes kits of the 60's and 70's are no longer
available. However, Estes is bringing them back (one by one) in so-
called, 'limited run collector series'. The original 'Mars Snooper' and
'Maxi Honest John' kits have been re-issued, so far, along with the
Star Trek and Star Wars kits. More releases are supposed to be
forthcoming. WARNING: Be prepared to pay a much higher
price for these re-released kits. Remember that inflation has led to
some items having much higher prices now than in the mid 60's and 70's. No
doubt Estes will take advantage of the demand for the re-released kits,
as well, and charge an additional premium.
4.2.2 Changes in Motor Technology
The big changes have come in motors. Expendable composite fuel motors
are now available in B-G range for model rockets. These motors
use ammonium perchlorate for oxidizer and rubber as the fuel, similar to
the rocket boosters on the space shuttle, allowing them to pack two to
three times the power in the same space as a black powder motor. The B
motors from Apogee are the same size as Estes mini-motors (13x45mm).
The C motors (also from Apogee) are 18x50mm, while the D motors are the same
size as Estes A-C motors (18x70mm). The D is a full D (rated at 20
Newton-seconds versus the Estes 24x70mm D of about 17 N-s). E motors range
in size from 18x70mm to 29x124mm. All of the motors give Estes kits an incredible
ride, if the models hold together. These kits require stronger construction
methods and materials than typical model rockets. Put an Aerotech D21
in your old Big Bertha at your own risk!! You're might end up with a
model with no fins (i.e., a complete 'shred').
Another new trend is 'reloadable' motor technology. With reloadables
you have a metal motor casing that you manually reload with solid fuel
pellets, delay and ejection charge for each flight. The casing is
reusable. Reloadable motors are available in everything from 18x70 mm
(with D - E power), 24x70mm, (with D - F power), 29mm, 38mm, and much
larger. Again, you can get all the way up to 40,000+ Newton-seconds of
total impulse.
The latest technology to hit the High Power rocket scene is the hybrid
rocket motor. Hybrid motors use components from both liquid and solid
ful rocket motors. Two companies have currently certified hybrid motors
with Tripoli, Aerotech and Hypertek. The advantage of hybrid motors is
that they use totally inert fuel grains, such as a cast polymer plastic
or compressed paper pulp, which do not have any DOT or ATF restrictions.
With both motors, nitrous oxide is used for the oxidizer.
4.2.3 Competition
One notable difference between the time I left the hobby (late 1970s) and
today is that competition rocketry is not as popular as it once was. It
used to be that one would see 30 or more people at an NAR regional, but
today it sometimes seems like you are lucky if you get enough people to show
up. Because I got back in to the hobby to fly competition, I am concerned
about the apparent loss of interest in competition rocketry.
Still, competition is NOT dead, no way. Yearly NARAMs are still held,
and are well-attended. About half of the NAR sections still host meets,
or have members that fly competition. The rest fly sport and/or high power
rocketry only.
4.2.3 High Power Rocketry
Now there is also HIGH power rocketry (HPR). These are rockets with
motors up to type O (with greater than 40,000 Newton seconds of impulse).
There has been a lot of discussion about high power recently. You have to
be a member of either the NAR or Tripoli to fly rockets with H motors or
above. To fly with H or above both organizations require that you be
'certified' by safely demonstrating a successful flight with a high power
model in the presence of one or more 'qualified' members of the
organization. There is now a HPR safety code as well as the original
model rocketry safety code. There are expendable and reloadable
(discussed below) HPR motors available. They are increasingly
expensive as the power goes up ( $13 for a G up to hundreds of dollars
for a really big (O) motor). High power rockets start where model
rockets leave off (i.e., > 1500 grams). High power models weighing
more than 50 pounds are not uncommon. The record weight for a high
power flight is over 1000 pounds.
Oh, yes, HPR requires a duly authorized, signed-in-blood (in triplicate,
etc.) FAA waiver for each day you wish to fly. It is ILLEGAL to fly
high power rockets without a proper waiver. See Part 10 of this FAQ for more
information on FAA waivers.
You will also need to get a Federal Low Explosives Users Permit from the
BATF. More on this below, and a lot more in Part 1 of this FAQ.
4.2.4 Electronics Advancements
Advances in electronics technology have created many opportunities for
new ideas in consumer rocketry. Electronic ignition of upper stages of
multi-staged rockets is now common. Several altimeters more recording
maximum altitude are available. Electronic deployment of recovery
devices, as well as deployment based on altitude, is now practical.
The FAQ section on High Power Rocketry has more to say about this.
See Part 02 of this FAQ for addresses of some companies selling
rocketry electronics.
4.2.5 Regulations, Regulations, Regulations
There is some good news and some bad news concerning rules and
regulations relating to consumer rocketry. On the positive side, you
can now buy up to G power motors in most states. Also, some states, such
as New Jersey, have recently relaxed restrictions on model rockets.
California still has some of the most restrictive regulations in the country.
The BATF and DOT have both become quite interested in high power rocketry and
have begun enforcing shipping and explosives regulations. Read the current
regulatory summary in Part 1 of this FAQ.
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4.3 Are my old rocket kits worth anything today?
With all of the BARs coming back into rocketry, many wanting to rebuild
their favorite kits from the days of their youth, models rockets
have become 'collectable'. In fact, the demand for some classic kits has
gotten quite high. The explosive growth of the internet has helped
fuel several recent 'classic kit' auctions. Model rocket kits from the
late 60's and early 70's can still be found, but be prepared to pay
quite a premium. It isn't unusual to see what was a $5 kit from the early
70's going for $50 or more in an auction. Remember the 1/70 scale Estes
Estes Saturn 1B? It cost $11 in 1970, $15 in 1977. If you bought one
today at a model rocket auction, it is doubtful that $200 would get it.
How about the Maxi Brute Pershing 1A, which sold for $17 in 1977?
That kit, in good condition, might bring over $150 today.
Old kits that are still in their unopened, original packaging, might be
worth something. Once you open the package, the value drops. Missing or
partially constructed pieces lower the value even further.
So, all you BARs with old kits up in the attic might want to think
twice before ripping open the boxes and finally building that
Orbital Transport you got on your 12th birthday.
Opinions about the collectibility of old kits varies on r.m.r. Some frown
on collecting kits, and feel the rocket should be built and flown for
maximum enjoyment. Some would consider building the old kit a great loss.
Others take a middle road, and "clone" the kit - produce a duplicate, and
keep the original. Still others create scaled-up versions of old kits for
HPR flying fun. Regardless of what you do with it, old kits can be a lot
of fun, and there is even a magazine devoted to collecting old kits
(see Part 2 of this FAQ under books and magazines).
Those interested in cloning an old kit should check out JimZ's website:
http://www.dars.org/jimz/rp00.htm
Plans for old kits not in this archive are out there, usually just for
the asking. Post a request Chances are someone has plans for that
favorite oldie.
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4.4 Where can I find plans of old kits?
Plans of old kits are available. The r.m.r. sunsite archive has a few
old kit plans, and hopefully, there will be more in the future.
Old kit plans available on the sunsite archive are:
Estes Avenger (2 stage model)
Estes Cherokee-D (first D motor kit for many)
Estes Cobra (3 engine cluster)
Estes Drifter (competition parachute duration model)
Estes Farside (big 3 stage model)
Estes Gyroc (gyro-recovery model)
Estes Mark (classic model, essentially the same as a Mark II)
Estes Nighthawk (canard boost glider)
Estes Pegasus (scale-up plans)
Estes Ranger (3 engine cluster version of a Big Bertha)
Estes Scout (classic, one of Estes first models)
Estes Sprite (ring tail, mini-model)
Estes Starlight (unique design)
Estes Trident (old timer favorite)
Estes X-Ray (classic payloader)
Centuri Payloader II (classic beginners kit)
To get to the r.m.r. plans archive, try:
http://sunsite.unc.edu/pub/archives/rec.models.rockets/PLANS
http://www.cmass.org:8000/sunsite.unc.edu/PLANS
Other sources:
Doug Holverson scanned the paper shrouds of:
Centuri Vulcan
Centuri X-24 Bug
You can find them on his web site:
http://www.probe.net/~dholvrsn/fanghome.html
Estes Mars Lander plans online:
Richard Pitzeruse <rmpi...@mailbox.syr.edu> tells us:
OK folks, I FINALLY got the Mars Lander plans on my webpage.
They are scanned in at 300 dpi, 1 bit/pixel. They are saved as
tiff files (uncompressed) and then zipped into 2 different files.
Feed back is welcome and encouraged!
To get directly there, point your browser at...
http://128.230.82.205/RocketPics/plans/lander.html
List of every Estes kit ever made:
Tom McAtee <m21...@SL1001.mdc.com> wrote:
OK! I uploaded it to Sunsite...
The file is called ekdir.txt (for Estes Kit Directory)...
http://suniste.unc.edu/pub/archives/rec.models.rockets/LISTS/ekdir.txt
Jim Zalewski's site:
http://www.dars.org/jimz/rp00.htm
Estes Andromeda plans online:
Lemeul E. Bryant <bry...@swbell.net> scanned the Andromeda decal sheet:
A scan of the Decal sheet for the Estes Andromeda is available at
http://www.geocities.com/CapeCanaveral/4491/index2.html
It's not best scan in the world but it is better then nothing.
The decal sheet measures about 3 1/2 by 13 1/2 inches.
The colors are red and white with a yellow background.
Estes Bomarc (Citation Series) plans online:
Ed Bertschy <bert...@azstarnet.com> put plans for the Bomarc online:
Complete full size templates of the Citation BOMARC wings, fins,
pods, ramjets, and re-engineered spine will be posted on my site
in .dxf and .bmp format for downloading. These measurements and plans
were drawn up from xeroxes of all the original parts. A color scan of
the decal sheet will be posted as well. You will find them at:
http://www.directfx.com/~ed.
---------------------------------------
Copyright (c) 1996, 1997, 1998, 199, 2000 Wolfram von Kiparski, editor.
Refer to Part 00 for the full copyright notice.
Wolfram v.Kiparski
Rec-models-rockets-archive-name: rockets-faq/part05
Posting-Frequency: monthly
Last-modified: 1998 November 16
URL: http://dtm-corp.com/~sven/rockets/rmrfaq.toc.html
Rec.Models.Rockets Frequently Asked Questions: PART 5 OF 14
MODEL ROCKETRY
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5.1 Can I legally fly model rockets in my state? What are the restrictions?
Several states still require some type of permit to fly model rockets.
The requirements vary greatly between the states. Also, local
municipalities are free to impose additional restrictions beyond those
defined in NFPA 1122 and any state laws. Check with your local fire
marshal for restrictions in your area. For example, the states
of Rhode Island, and California have stricter regulations than NFPA 1122.
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5.2 When do I need to notify the FAA before flying a large model rocket?
Large Model Rocket (LMR) is an FAA designation for a model rocket that is
between 454 grams (16 ounces) and 1500 grams of mass, including propellant,
-OR- contains more than 113 grams (4 ounces) but less than 125 grams of
propellant (all motors).
Please note that this definition is different from the definitions of a
model rocket found in NFPA 1122 and 1127-94. Some rockets may be defined
as LMR by the FAA, but are actually HPR according to the NFPA.
If you are planning to fly a Large Model Rocket as defined by the FAA, you
must notify the "FAA ATC facility nearest to the place of intended operation"
24-48 hours before launch.
FAA notification requirements appear in FAR 101, and all of the pertinent
regulations appear in Part 10 of this FAQ.
A sample FAA notification form is available at the sunsite archive at:
http://sunsite.unc.edu/pub/archives/rec.models.rockets/FAA/FAR101.22.notice
From Bob Kaplow (robert...@hccompare.com)
"you need to find the right FAA office to notify. If you don't know
where they are, call 1-800-WX-BRIEF, and ask a briefer for the
proper place to call. Get an FAA map of your area. From that you can get
latitude/longitude, and radial/distance from your launch site to a nearby
VOR. Call 24-48 hours before the launch and give them the information.
I usually write a letter and mail/fax it to the folks first. That way
they have everything in writing. As a courtesy, I also call the closest
flight service station (FSS - ask the folks at 1-800-WX-BRIEF where they
are) and ask them to issue a locak NOTAM.
Get the "L" number as proof that you called."
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5.3 I have a son/daughter that is (less than 9) years old. Is this too
young for model rocketry? If not, are there any tips for helping
to keep their interest in the hobby?
Model rocket manufacturers all recommend adult supervision for young
children (usually, those under 12). Many parents have had great success
introducing these children to model rocketry. Here are a few of the tips
and suggestions posted to r.m.r:
From c...@rocket.sw.stratus.com (C. D. Tavares):
Children under 10 or 11 do best in the hobby when a parent participates
actively with them. Introduce them to simple, skill-level-1 kits with
plastic fin units. Build yourself a rocket at the same time, then go
out and fly them together.
From ja...@rml.com (Jack Hagerty):
My own experience with my son (now 5 1/2, we've been flying since he
turned 4) is not to expect too much sustained interest at a time. Even
though my son has a longer-than-normal attention span for his age
(he'll watch a whole two hour movie!) and loves the whole idea of
building and flying rockets, after 4 or 5 flights (approx. 1/2 hour)
he'd rather go play on the monkey bars at the adjacent school.
This is magnified if there are any kids his own age around (such as his
cousins that sometimes come with us).
From dw...@jarthur.Claremont.EDU:
Watching they should enjoy. Pressing the button they should enjoy.
Prepping with serious supervision. Building simple kits with some
supervision and a pre-launch check. There's a huge difference in
responsibility between kids. One thing to stress is that a lot of very
careful kids will get bored or get pressured by bored friends to do
stupid things when you're not around. I might not let kids have any
access to motors when unsupervised -- and there's no real reason why
that should cause them any trouble. It is possible to make safety fun,
you know. I think that's something that a lot of people miss -- if you
present things that way, it seems to work out. I don't have kids, but
I've got rocket launching friends who do.
From J.C...@ens.prime.com (Jim Cook):
I've successfully built an Athena and an America with a 7 year old.
The body tube is pre-painted, the decals are self-adhesive, and they
like the gold or silver chrome nose cone. You can build it in an hour
or two - just let them run around and call them over to help periodic-
ally - "glue here", "cut here", "hold this". They feel it's still
their rocket and that they helped. Estes new E2X series may also be
similarly suitable, but I haven't tried, yet [ed. note: the E2X
series go together with plastic model cement, such as Testors, not
white glue].
Estes' new E2X series is similar in construction to the Athena and
America - they can be built in an hour or two with kids.
Demo a range of motors. Go from 1/2A to A to B with a model to
show kids the difference.
Kids will invariably talk about launching them out of sight or
sticking a fireworks in them. Answer with, "yeah, but I wouldn't
want to wreck my model that I spent so much time building." Making
the kid answer forces him [or her] to think and teaches him [her]
to value his [her] possessions.
From bmcd...@ix.netcom.com (Buzz McDermott):
When my 10 year old son and I started building rockets together about
2 1/2 years ago, we started with some of the level 1 Estes kits with
plastic fin units and nose cones, such as the Athena and Alpha III.
He has also built a couple of the Estes E2X series, which requires use of
plastic cement. He also likes the Quest Falcon (plastic fins) and Estes
Big Bertha (balsa fins) because they are both big enough to use C
motors and not loose the models.
My 7 year old daughter and I started building rockets about a year ago.
She prefers the Quest models with the colored parts. She also finds the
Quest parachutes, with their large adhesive connections for shroud
lines, easier to build. The Quest Falcon is a large, easy to build
model. Now she likes building some of the Level 1 kits with balsa fins.
She has built the Estes Alpha and Quest Sprint.
From jste...@software.mitel.com (John Stewart):
My daughter loves rocketry. She started when she was 3. Get colorful
rockets, build them yourself (e.g. the plastic Alpha III), and don't
fly them too high. (50-100' is more than fine) Let the child count to 5
(or try to!!) and push the button. Let them recover the rockets. Have
say, 5 to 10 rockets loaded, ready to go when heading out. Launch them,
and untangle/fix them either at the field, or at home later, depending
on the child's mood. My 4-3/4 year old daughter is looking forward to
launching, possibly this weekend. We spent a year in New Zealand, but
she still knew all about the rockets, the parachutes, the streamers...
From r...@cyclops.micr.Virginia.EDU (Robert Sisk):
People interested in easy to build model rocket kits for the younger
crowd should check out QUEST models. Some of the parts are color
coded (centering rings, engine blocks, engine mount tube) and the fins
of some models are plastic. Some of the fins are supplied as a single
unit that you glue into place. Fast, easy, and with little or no
sanding!
From wa...@pen.k12.va.us (Tony Wayne):
I reconstructed my launcher so that me 2.5 year can
launch the rocket. The launcher is homemade and uses a shorted
out 1/8 mini plug for the safety key. For my son, I attached an
8 foot loop of wire with each end attached to the poles of the
mini plug. In the middle of the wire loop is a film canister
with a push button. To launch the rocket I have to push the
button on the launcher and my son has to push his button too!
(When connecting the igniter to the launcher, I carry his
launch button with me.)
He practicing counting by leading the countdown. (Q: Is
"bi-leven" greater than or less than 4?) He checks the airspace
as well. ("Look boss! De'plane.") Also when we go to the field,
my rockets are ready launch. For about 20 minutes things
happen fast. When we are done there are rockets littering the
field. We then fetch them. (He "flies" a few of them back to
the pad.) His mom has to come too as diversion after fetching
so I can prep and go again.
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5.4 Is there any way I can buy model rocket kits, parts and engines at less
than full retail?
Three mail order houses have been recommended several times by posters to
r.m.r. They are Belleville Wholesale Hobby, Magnum Rockets Hobbies and
More, Commonwealth Displays, and Discount Rocketry.
Belleville sells MRC at 40% off list, Custom Rockets at 35% off list,
and Estes at 30% off list. There is a minimum order requirement.
Magnum and Mountainside sell most all of the
major model and high power rocket lines. Both Estes and Aerotech model
rocket motors and reloads are sold. They both advertise Estes at 28-33% off
of list. Magnum will also discount educational sales (such as to schools,
Scouts, YMCA, etc.) at up to 40% off of list.
Another potential source for a large discount, if you are buying several
hundred dollars worth of parts at one time, is America's Hobby Center.
They offer discounts of up to $160 off of Estes' list price on orders of
over $400.
There are several other mail order sources that sell at discount. Some of the smaller
manufacturers/suppliers of model rocketry kits and supplies are a substantial bargain.
For the addresses of the sources listed above, and addition sources, refer to the
'Names and Addresses' section of this FAQ (PART 2). Shop around.
There are bargains to be found.
If you do a fair amount of flying, Estes sells a 24-pack of engines called
the Flight Pack. It comes with 6 A8-3, 6 B6-4, 6 C6-5, 6 C6-7, recovery
wadding and igniters. It generally retails between $32-36, which is less
than the list price of the materials included. This can also be purchased
at an additional discount from some mail order houses. Estes also sells
'bulk packs' of 24 A8-3 or B6-4 or C6-5 motors.
Quest motors have been recommended by several r.m.r posters. At the
present time, they retail at less than the Estes equivalents. They can
also be purchased direct from Quest 'bagged' in quantities of 10 or more.
'A' motors can get to less than $1 ea. when bought 50 or more at a time.
'C' motors get down to around $1.25.
You might also investigate your local NAR section, if one is located
convenient to you. Clubs such as NAR sections often arrange discounts
with local hobby merchants. Several of the clubs also have at least
one member selling parts and supplies at discount, mostly to the
club members.
----------------------------------------------------------
5.5 I've had a large number of motors CATO recently. The engines are only
about 2 years old. I've had them stored in my (attic/garage/basement).
From J.C...@ens.prime.com (Jim Cook):
Black powder motors tend to suffer catos when they are temperature
cycled. If you expose them to heat, be it storing them in the attic,
on your car's dashboard, or in your metal range box in the hot sun on
the launch field, you may have problems. The engine expands with the
heat, but when it cools, the propellant separates from the casing
inside This causes the propellant to burn faster due to burning on the
side generating more pressure than was designed for, and ...boom...
Storing black powder motors in a damp basement can cause the compressed
clay nozzles to soften and also blow out. If you must store your motors
in a damp/humid area, put them in a zip lock plastic bag.
[Note: There is an excellent article by Matt Steele in the May/June 1992
issue of Sport Rocketry. This article goes into the
theoretical reasons why black powder model rocket motors fail]
----------------------------------------------------------
5.6 Is it safe to use my old rocket engines from <nn> years ago?
From J.C...@ens.prime.com (Jim Cook):
I've had properly stored engines from 1972 and 1975 work just fine.
If you suspect a motor, fire it by burying it in the ground with just
the nozzle showing, pointing up and use your launch system to ignite it
as usual. [Note: be sure and stand at least 15-20 feet away from the
motor when you fire it: Buzz]
----------------------------------------------------------
5.7 What's a good way to find other rocket enthusiasts in my area? How
can I found out about local rocket clubs?
Post a message on r.m.r. You might find someone there who lives close to
you, or knows someone who does. Check out Part 03 of this FAQ.
A list of NAR sections (clubs) is kept at the NAR web site: www.nar.org
The NAR sends a complete list of its local sections (NAR sanctioned
clubs) with each new member's information packet. If there isn't
a sanction near you, they can send members a list of other NAR members
in your area, so that you can form your own section.
----------------------------------------------------------
5.8 Are the Aerotech composite motors the same size as Estes/MRC/Quest
motors?
Aerotech makes the following 'standard' retail motors in -4 and -7
second delays. The first two motors are the same size as Estes A-C motors.
The next two are the same size as Estes D motors. There are some other
24mm motors that are available from Aerotech that are longer than
Estes D motors. Some of these 'non-standard' Aerotech 24mm motors are listed
after the four 'standard' ones. The F and G motors may be obtained from
some dealers and mail order sources, but are not packaged for retail sale.
Motor Size Power Same Size As
D21 18x70mm 20NS Estes/Quest/MRC A-C
E25 18x70mm 22NS Estes/Quest/MRC A-C
E15 24x70mm 40NS Estes D motor
E30 24x70mm 40NS Estes D motor
F32 24x124mm 80NS Non-standard size
F44 24x101mm 70NS Non-standard size
G42 24x144mm 90NS Non-standard size
G55 24x177mm 125NS Non-standard size
Aerotech makes and sells reloadable motor casings and reloads in 18,
24 and 29 mm sizes. The 18mm is the size of an Estes C motor. The
24mm is the size of an Estes D or Aerotech E motor. The 29mm is the
size of an Aerotech G motor. Aerotech High Power, formerly ISP Consumer
Rocketry division, makes a 60NS F and 100NS G casing, both 29mm in
diameter.
----------------------------------------------------------
5.9 Can I use Aerotech or other composite motors in my Estes rockets?
Yes and no. They are the same size. Composite motors have 2 to 3 times
the power of comparably size BP motors. Balsa-finned 18mm powered models
tend to loose body parts in quantity when launched with a D21 or E25.
The ejection charges seem to be hotter, as well (IMHO). The same holds
true for Aerotech 24mm motors. Care should be taken before launching a
24mm-based model on an E15, let alone an E30. I have an old MegaSize that
I fly on E15-10's. Works great. The Estes Saturn V flies well on E15's,
too. E30's tend to shred all but the strongest D models, though. E30's
also tend to relocate motor mounts to someplace OUTSIDE of the rockets, as
well. If I plan to use E's in an Estes model I make it a point to reinforce
the motor mount, especially for EM-2060, EM-2070 and EM-5080 mounts.
You also want
to use an engine block (a 2050 adapter ring works great) in addition to
the metal clip. IMO, I would also reinforce fin/body tube joints. Five
minute epoxy fillets work great. Generous cyano fillets also seem to work
well. White glued fins don't seem to survive E15/E30 launches with any
consistent success (i.e., the failure rate tends to be > 50% :-). Many
modelers also recommend that stronger 24mm motor tubing, such as that from
LOC or Aerotech, be used for models flying with composite motors. The
stronger tubing holds up better to the ejection charges of the composites.
There are now several D and E reloads available for the 18 and 24 mm
casings that might not over power 'standard' model rockets. The RMS
motors have a variety of reloads available, some with fairly low average
impulse.
----------------------------------------------------------
5.10 Will my Estes launch system work with Aerotech composite motors?
The classic Estes, Quest and MRC 6 volt launch systems will not reliably
ignite the Copperhead (TM) igniters that come with Aerotech motors, and
Estes Solar Igniters (TM) will not ignite a composite. These motors need
12 volt systems for reliable ignition.
----------------------------------------------------------
5.11 Can I use Aerotech composite motors as boosters in my multi-stage
rockets?
Basically, NO. Black powder booster motors will not ignite composite
motors. Therefore, you cannot use a composite upper stage in a traditional
multi-stage, black powder rocket. Also, there are no composite booster
motors currently in production. They all have delays (4 seconds being
the shortest current delay from Aerotech, for example) or are plugged.
Typically, you cannot (and should not) use these as boosters in standard
black-powder multi-staged rockets.
If you want to use composite motors in multi-stage models then you have to
use other methods of igniting the upper stage (whether black powder or
composite) than are used with black-powder-only rockets. One method is
to electronically ignite the upper stage motor using a mercury switch to
complete an electrical connection to a capacitor at first stage burn-out.
This, in turn, sets off a flash bulb/thermalite fuse combo which ignites
the upper stage motor. Another method is to ignite lengths of thermalite
fuse at the time the booster is ignited. The length of fuse determines
the delay before the upper stage is ignited. Refer to the 'Other Sources
of Information' section in Part 1 of the FAQ. The NCR High Power technical
reports on staging composite motors is applicable to multi-staged,
composite motor powered model rockets as well.
Bob Weisbe uploaded plans for a mercury switch-based staging system that he
used in a converted Estes Terrier-Sandhawk kit. The URL for these plans
is:
http://sunsite.unc.edu/pub/archives/rec.models.rockets/PLANS/terrier_sandhawk.ps
----------------------------------------------------------
5.12 How can I tell the age of my Estes motors?
Estes uses a date code on their rocket motors. It's of the form XXYZZ
(example, 25T9) where the first number is the day of the month of
manufacture, the letter is a code indicating year of manufacture, and the
last number is the month (1 = January, 12 = December). Date codes
run progressively through the alphabet, as follows:
T 1989
U 1990
V 1991
W 1992
X 1993
Y 1994
Z 1995
A 1996 - Estes cycled back to the beginning of the alphabet
In the early 70's, Estes motors had the actual date stamped on them.
----------------------------------------------------------
5.13 Are reloadable model rocket motors shippable the same as disposable
model rocket motors?
The Aerotech RMS line of model rocket reload kits (of B through G power
levels) has been certified by the DOT for shipment as Class C Flammable
Solids. This means that the reload kits may be shipped the same as
other model rocket motors, such as those made by Estes and Quest.
There are no shipping restrictions of any kind on the motor casings and
closures.
----------------------------------------------------------
5.14 My flying field is so small I keep losing my rockets. What can I do?
DON'T GET DISCOURAGED. Everyone loses rockets. It's part of the hobby.
There are ways to minimize this when you're forced to fly in smaller
fields, though. The following is a consolidation of tips posted to r.m.r
by numerous individuals:
Recovery Modifications:
1. For smaller rockets, use a streamer instead of a parachute. This
can be done with rockets of up to BT-50 body tube size and up to
18" long. Be sure and check rocket weight, though. If the model uses
heavy plastic fins you might still want to use a parachute.
2. Reef the chute lines to reduce the effective surface area. Tie or tape
the shroud lines together 1/3 of the way from their end. This reduces
the shroud lines to 2/3 of their original length and prevents the chute
from fully opening. The rocket will come down faster and drift less.
3. Cut out the Estes or Quest logo from the center of the chute. This lets
more air spill through the chute and reduces its drag. Be careful to cut
out the whole logo. Cutting only a small whole (say, less than 2" in
diameter) can improve the chute's stability and actually make it lift
better and drift further.
4. Use a smaller chute. Try cutting down an 18" chute to a 15" chute, or a
12" chute to a 10" chute.
5. Use longer ejection delays. If a B6-4 ejects the parachute right at
apogee, use a B6-6 to let the rocket come down a little before popping
the chute. Less time chute is open equals less drift. Take care in
making the chutes and recovery attachments extra strong, though, as
the descending model will put more strain on the recovery system than
if it were to deploy at apogee.
Other Suggestions:
1. Find a different field. If you fly alone, try and find a local rocket
club. The odds are the club will have found a better field in which
to fly.
2. Fly larger rockets. A Big Bertha on a B6-2 will drift a lot less
than a Sky Hook or other small model on a B6-4 or B6-6. Larger models
have more impressive liftoffs, as well. Larger diameter rockets
don't fly as high and come down faster than the really small ones. The
big ones are also easier to spot in high grass, weeds, trees, etc.
3. Use smaller motors. If the recommended motors for a rocket are, for
example, A8-3, B6-4 and C6-5 or C6-7, try it on A8-3's first. If
the model lands well within the recovery area you can then decide if
the larger motors will allow the model to be retrieved.
4. Launch rockets at a slight angle into the wind. The rockets will
weathercock and deploy recovery systems upwind. If all goes well, they
will land closer to the launch site.
----------------------------------------------------------
5.15 Are Jetex engines still available? Where can I get them?
Although, technically, jetex type products are NOT model rocket motors and
do not fall under NAR/NFPA guidelines and safety codes, a number of
questions do pop up about these on r.m.r. The following sources have been
quoted on r.m.r as selling Jetex products:
Peck Polymers
P.O. Box 2498
La Mesa, CA 92041
Doylejet
P.O. Box 60311
Houston, Texas 77205
(713) 443-3409
----------------------------------------------------------
5.16 BT-20, BT-50, BT-55. What the heck do the numbers mean on Estes
body tubes? Is their any special meaning in these numbers?
From: Pete...@aol.com (Peter Alway)
Estes tube numbering seems to have progressed like the numbering
of steps in a BASIC program. The very first Estes Catalog had
numbers unlike the BT-20..BT-50... etc. system they use now.
Sometime in the early 60's they gave numbers 10, 20, 30, 40, 50
to their tubes in order of size. 10, 20, and 30 were almost
identical in diameter (though 10 could be coaxed to fit into
30) All were meant to hold 18 mm rocket engines. BT-10 was
an ultra-light spiral-wound mylar, BT-20 was essentially as it is
today, and BT-30 was a parallel wound heavy-duty tube. BT-40
was also a parallel wound heavy tube that fit over BT-20. (rather
like Quest T-20, but thicker and parallel wound.) BT-50 was as it
is today, as was BT-60. BT-5 came along later, I believe created
for the top of the Aerobee 300, and numbered halfway between 0 and 10.
BT-55 came along after BT-60 and was numbered to fit in. PST-65 egg
tubing came after the much larger BT-70 (originally used just for the
Sprite tail ring) BT-100 and BT-101 first appeared in the 1/70 scale
Saturn IB. BT-80 was created for the Saturn V. It is interesting to
note that two standard HPR diameters, 2.6" and 4" began as scale
model components. Estes also created BT-3 for the Saturn IB, and BT-51
for the tanks. BT-52 was produced for the BT-60 Semi-Scale Saturn V, and
this tube still appears as a hook-retaining sleeve on some Estes D engine
mounts. The sleeves are still correct for a 1/242 Saturn V. Many BT-5
clone kits still use the length for an Aerobee 300.
----------------------------------------------------------
5.17 I've seen mention of all kinds of rocket motor types and sizes. Could
you give a brief history and summary of the main marketing names for
model rocket motors?
From: msjo...@WichitaKS.NCR.COM (Mark Johnson)
The original hand-loaded motors made by Orville Carlisle and sent to Harry
Stine in about 1956 were 0.5 in dia. (13mm) x 2.25 long (55 mm). These
were used in early testing up until the time Model Missiles Inc (Stine's
company) began to produce commercial product in sufficient quantities
that Carlisle could no longer make motors fast enough. These had total
impulse roughly from today's 1/2A to about the middle of the B range.
Stine contracted with Brown Fireworks Co. of Missouri in 1958 to make
mass-produced motors. Brown could have made them in the same size as the
Carlisle motors, but it would have meant costly new tooling. Mr. Brown
offered to produce a low-cost motor for MMI using his "Buzz Bomb" case
size - 0.7 x 2.75 in (18 x 70 mm) - the Buzz Bomb had a small aluminum
blade on one side of the case and a nozzle drilled into the side of the
case opposite, where a fuse was inserted. Strictly a fireworks piece.
In about 1959 or 1960, Vern Estes entered the picture, having offered to
produce motors for less than whatever price MMI was paying Brown. G. Harry
took him up on the offer, and Vern began making motors in the now-standard
18 x 70 mm size. He quickly automated production with the first of several
"Mabel" machines and was able to make far more motors than MMI needed.
That's when Estes entered the model rocket business himself.
The short motors were 1/4A and 1/2A motors which came about in around 1963
or 64 when somebody at Estes realized that the upper 1" of the casing had
nothing in it, and was just dead weight. So Estes started producing the
"S" series, with a case size of 18 x 45 mm (0.7 x 1.75 in). These
continued in production until 1970 or so.
In about 1970 or 1971, Stine (whose MMI had gone out of business somewhere
around 1962) reentered the hobby as a paid consultant to Model Products Co.
(MPC), which later spun off its rocketry business as AVI (Aerospace
Vehicles Inc). Stine persuaded Mike Bergenske that there was a market for
the "classic" 13 x 55 rocket motors as a high-performance motor, in sizes
from 1/4A to B. These were the Mini-Jet motors, which quickly resulted in
rewriting the NAR altitude record books. Estes followed suit with its
mini- motor line, originally trademarked "Mini-Brutes" with the 13mm
diameter but choosing to go with a length compatible with the old "S"
series at 45 mm (so they could use the old "S" series engine hooks, I
presume). Centuri's "M" motor series, in sizes from 1/4A to B, were
released at about the same time. These were 13 x 50 mm (0.5 x 2 in)
The other "standard" motor type which emerged about this time was the
Estes "D" motor, which was sized to fit easily in the BT-50 or 25mm tube,
while keeping the 70 mm length constant (save the engine hook tooling
again, I guess). These first hit the marketplace about 1969; I still
have the original announcement flyer somewhere in all my old files. The
24 mm diameter has become the "small high power" standard for D, E, F,
and even a few G motors, mainly from AeroTech. Estes chose to keep the
existing standard diameter and extend the length on their new E15,
introduced during 1993.
The 29 mm standard motor emerged from the Enerjets. The original
Enerjet-8, a fiberglass-cased motor developed and produced by Rocket
Development Corp. of Indiana (RDC, later acquired by Centuri as
Enerjet, Inc) was an external-delay, 29 mm diameter motor with about 35
N-sec of total impulse (8 lb-sec). The Enerjet-8's external delay was
too cumbersome for unsophisticated users, and was replaced by a
conventional internal delay when the Enerjet E24, F52, and F67 were
introduced in 1973 by Enerjet and Centuri, its parent. The F67 was the
first full 80 N-sec F motor produced in the US.
FSI is a bit of a cipher in all this. They chose to go with a 21 x 70 mm
motor for A, B, C, and small D motors, beginning in about 1966 or so.
Their full D and small E motors are in 21 x 95 mm cases. (D18, D20, and
E5). The larger FSI motors are in 27mm cases of various lengths. The E60
is about 95 or 100 mm long, and the F7 and F100 are 125 mm. FSI started
producing 18 x 70 mm A, B, and C motors in about 1985 or so.
----------------------------------------------------------
5.18 Why don't I just make my own model rocket motors? Shouldn't I be able
to custom-make better, more powerful motors, at a cheaper price?
This subject has been hotly debated on r.m.r. It is one of those
'emotional' subjects that find people either firmly for or against.
The following post from Lawrence Smith probably says it all best.
From: thes...@mv.mv.com (Lawrence Smith)
In our pre-made, factory-produced society there is a bit of nostalgia
for doing things the "old-fashioned" way - "home made" carries with
it the feeling of being somehow "better". It could be tastier, more
durable, easier to maintain, or cheaper, it is some quality that we
don't find in mass-produced items. It is therefore natural for fans
of rocketry to look at the prices of the ingredients of an engine and
think to themselves that such engines really can't be all that difficult
to make - and that "home made" might be not only cheaper, but
just as good as factory engines in other ways.
There is a grain of truth here - _just_ a grain - but that is enough
to make the idea pretty dangerous. Most readers of this will not be
old enough to remember the "Basement Bomber" headlines from the late
fifties and early sixties. Making solid-fuel rocket engines _is_ a
pretty dangerous proceeding, unless you do it _right_. And even if
you do it _right_, you must be _consistant_ in following the safety
precautions. It really won't matter whether it is the first or the
fiftieth engine that blows your hand off in the long run. It is the
need to watch the safety precautions that is your first "hidden cost",
something that most people dreaming of home-made engines seldom add to
the calculation.
You need _room_, you can't do it in your basement, nor, indeed, in
your house at all. Nor in your apartment, nor in your school chem
lab, nor anywhere else there is something you don't want blown up.
You must _assume_ the engine _will_ blow up, and ask yourself where
it would be okay. Maybe an outbuilding on your property, maybe out
in some field. You need _space_ to build engines. You either need
to own that space or have the permission of people who do, too.
In most places in the country, you need some sort of _license_.
Rocket engines are first cousins to pipe bombs, and there are
few municipalities that would care to have you building those. On
the other hand, there are many municipalities that don't care if you
reload spent shotgun shells, even without a license. You need to
know and understand the local regulations. You are not building a
class "C" toy propellant device. Even if you _think_ you are. That
is a legal name, not a descriptive one.
You _can't_ reuse Estes or other maker engine casings. Spent casings
have undergone considerable stress, they can no longer be guaranteed
to hold if reloaded and fired again. Yes, they have a fairly consider-
able safety margin. It isn't enough to reload them.
You _can't_ use the same stuff Estes uses, nor can you easily obtain
composite fuel. Estes uses black powder - gunpowder - but they are
using a special formulation, not just mixing the usual ingredients.
In fact, it's pretty dumb to use any powder at all. Powder must be
rammed to make it solid enough for "solid fuel" - that means you have
to pour the powder into the casing and then take a stiff rod and ram
it up and down, like one of those old-time muskets. Ramming will
compress the powder - which is the objective - and will also heat it,
which will also make it more shock-sensitive, not to mention the heat
from the friction of the rod itself moving up and down in the casing.
It can also raise dust, which is also more easily ignited than a solid
slug. A fellow by the name of Jim Flis posted a commentary on creating
such engines, I recall. If anyone saved that post, I'd like to see to
see it inserted here.
Even if you manage to pull off all the above, the engine may not perform
like you expect. Your ingredients may not be up to snuff, or maybe you
didn't ram enough, or maybe something else got mixed in by mistake, or
maybe you forgot to add the final layer to the casing - whatever. There
is a real good chance any home-made engine is going to do serious damage
to your rocket, even if it didn't do any to you. One of the things you
pay for from Estes and Quest is _quality_control_. And even with professionals
with years of experience with A, B, and C engines, Estes has
problems with D and E engines. Can you really do better?
Estes, Quest, and the others have _time_, they have _equipment_, they
have _space_, they have _quality_control_ and lastly, they have _liability
insurance_ for when something happens with one of their engines. _That_
is what you are paying for, not just a couple teaspoons of black powder
and a bit of clay and cardboard. As you can see, there is more than meets
the eye in an Estes or Quest engine. The fact of the matter is this: a
premade, off-the-shelf engine _is_ cheaper, more reliable, and far, far
less effort to obtain. There is really no reason to try to duplicate a
standard engine.
That said, there will remain a small core of people who still want to
roll their own. Maybe they need a non-standard size, or they just are
more interested in the engine than in the rocket. Before you proceed,
you will need a copy of "Rocket Manual for Amateurs" by Bertrand R.
Brinley, Capt. It's out of print, so you'll have to do some looking.
If you aren't patient enough to track down a copy then you aren't
patient enough to build engines. Take the hint.
Brinley gives a good overview of propellant technology up to the mid-
sixties or so, which is good enough for you, since the advances have
mostly been in the realm of "real" rockets with incredibly exotic
chemistry. He concludes that amateurs should stick to zinc and sulfur.
Zinc and sulfur can send rockets high enough to need an FAA waiver, so
this is really not limiting. Also, though zinc and sulfur can be ram-
med, they can also be mixed with acetone or alcohol to form a putty
that can be inserted into a casing and cast into shape. This he terms
"micrograin". I won't go into detail on proportions or other infor-
mation, you'll have to find the book. _I_ not telling you how to
build an engine, _I_ won't do it, and I don't think _you_ should, but
if you are anyway I want you to be aware of what you need to do to
succeed, for if you fail the consequences will be horrible.
While Brinley is helpful for fuel, he is more valuable for the kinds
of safety precautions you need to take. You are going to need sand-
bags. Take the hint.
One thing Brinley assumes, though, is using metal cases, including CO2
cases for small engines. This will _definitely_ make your rocket require
an FAA waiver, and the metal content will make it easy to spot your
rocket on radar, so you better not try to mickey-mouse it. Of course,
the FAA will _not_ be forthcoming with a waiver for an experimental
free-flight rocket, unless you are launching from someplace in the
southwest desert area, and maybe not even then. In a way, this is an
advantage. A metal-encased engine will fragment when it explodes, and
is far more dangerous that one in fiberglass or carbon fiber. Also,
metal is far more likely to cause a spark somehow than are non-metallic
components, and so are safer to handle. This limits the size and
materials you can use.
You will need to improvise on Brinley and develop a fiberglass or
carbon-fiber casing and clay or other material nozzle. I have an
ulterior motive for mentioning this, and I admit it freely. Making
a casing like that is not trivial to begin with, and you will find
it's pretty expensive, both monetarily and in terms of time. If
that still does not deter, at least you will be encouraged to make
your engines _small_ - which will make the process safer, for there
will be less to explode. I have no idea how thick the casing needs
to be, nor would I say if I did. Again, you need to do your home-
work.
If you take the advice in this post to heart, you will not make a
rocket engine. If you take only some of it, you will build a much
smaller engine, in a casing less likely to become deadly shrapnel
(not _un_likely, just _less_ likely), and with techniques less likely
to cause an explosion. You will be doing it with the advice of a
professional (Capt. Brinley, not me) and hopefully will succeed, and
then either give it up or go legit and start a career with Morton
Thiokol. Who are, of course, the makers of the shuttle SRB's used on the
last flight of the Challenger, just in case you thought being a
professional meant that you had everything figured out.
---------------------------------------
Copyright (c) 1996, 2000 Wolfram von Kiparski, editor.
Wolfram v.Kiparski
Rec-models-rockets-archive-name: rockets-faq/part06
Posting-Frequency: monthly
Last-modified: 1997 January 6
URL: http://dtm-corp.com/~sven/rockets/rmrfaq.toc.html
Rec.Models.Rockets Frequently Asked Questions: PART 06 OF 14
MODEL ROCKET CONSTRUCTION AND FINISHING
This section includes tips and suggestions on various topics having to do
with construction and finishing techniques. These have been posted to
r.m.r or mailed to the moderator by way of r.m.r request. Refer to the
High Power Construction section for additional tips, oriented towards high
power and advanced rocketry requirements. Even more construction tips can
be found in the Scale Modeling section.
[Note: This part of the FAQ is maintained by Robert C. Santore
(san...@ibm.net)
Any additions or corrections should be sent to that address]
-----------------------------------------------------
6.1 Cutting, Sealing, Attaching Fins
From: JC...@Epoch.COM (Jim Cook)
Skip using glue W/ balsa dust, dope, or any other junk for filling the
grain in balsa fins or nose cones. Use Elmer's "Fill 'n Finish" diluted
with water to a thick paint (like white glue is) and paint it on.
Non-toxic and a coat or two will do. Use Elmer's "Carpenter's Wood
Filler" thinned similarly to fill the spiral in body tube. Both come
in a white plastic tub with an orange lid. Note - the latter is
harder to sand, so don't make the mistake of using it on balsa as it
will require a lot of sanding.
From: c...@pdp.sw.stratus.com (C. D. Tavares)
Fill your fins BEFORE attaching them. (Don't fill the root edge).
From: utid...@remarque.berkeley.edu (David M.V. Utidjian)
[To hold fins in place and aligned while drying I bought an Estes
fin alignment kit]. At 15-16 bucks it seems a bit
expensive but is well worth the aggravation and time it saves. You
can even make your own if you are handy. I just set up my body tube
in the jig and then check the alignment of all of the fins to the body
tube. Then I use a thin bead of 5-min. epoxy. and in ten minutes I am
done. When I do the fillets I can do them all at once but don't have
to worry about the softening the glued on fins so they droop. You
still have to lay the model on its side though but only for 5 minutes.
From: kapl...@hccompare.com (Bob Kaplow)
The Estes Fin Alignment Kit has now been discontinued for '96. You can
use the newer Rocket Builder's Marking Guide ($5-8) to do one fin at
a time. [Editor's note: This is a HIGHLY RECOMMENDED item to purchase.
It provides everything needed to mark BT-5 through BT-60 body tubes
for 2, 3, 4, 6, or 8 fins.]
-----------------------------------------------------
6.2 Body Tubes (Cutting, Joining, Filling)
From: c...@pdp.sw.stratus.com (C. D. Tavares)
[On cutting Estes-style body tubes]
The simplest and best I ever used was Howard Kuhn's jig from the old CMR.
It's a simple piece of wood L-angle molding, with a notch for a razor
blade cut into one side (from the wing toward the elbow) at one end.
The only other parts are a wood block and a large black spring clip (the
kind you hold really thick reports together with). If you want, say, a
6" piece of tubing, you set the block 6" away from the razor notch and
clamp it there with the spring clip. Now lay the tube down the L-angle,
butting it up against the wood block. Insert the razor blade, press
lightly, and turn the tube. (Put a dead engine into it if the tube is
the right size to fit one.) Three to six turns, and you have an edge
that looks factory-cut.
----
( ) <- spring clip | <- razor (edge on,
/ \ | sharp edge down)
____________---------___________________________|_______
| /_| |__/| | |
| | |_______| || angle molding | |
| | wood block || |
|----------|____________|/-------------------------------j
/ lay tube here and spin it /
/________________________________________________________/
From: soc...@vx.acs.umn.edu (Tim Harincar)
[On cutting Estes-style body tubes]
When I cut tubes, I always wrap the tube with about two
layers of drafting tape with the edge of the tape along
the cut line. This accomplishes two things: First the
thick tape edge providing a excellent knife guide. Second,
you can assure a straight cut. If the tape wrinkles when
you wrap the tube, you know it is not on straight; simply
remove the tape and try again until you know its down flat.
Drafting tape is better than regular masking tape because it
has almost the same thickness but is made to be removed.
This method is in addition to reinforcing the inside with
a stage coupler or spent motor. Also, always use a new
x-acto blade for the best cut.
From: Jim Bandy (NAR member not on net)
Use a piece of aluminum 'angle iron' for joining body tubes. Place one
tube in the angle, insert and glue the joiner, then insert and glue the
other tube. It give very straight joins. The angle can also be used
for marking fin lines on body tubes, etc.
-----------------------------------------------------
6.3 I'm fed up with tangled plastic parachutes with broken shroud lines. How
can I improve on the standard chutes, or make my own?
From: soc...@vx.acs.umn.edu (Tim Harincar)
Making your own parachutes is pretty easy. Start with the desired
material (usually mylar or a light plastic). Make a cutting pattern out
of cardboard by first drawing a circle that will be the maximum size
of the chute (i.e. 16"). Take a compass [or] something that will give
you an accurate radius of the circle. Pick a point anywhere on the
circle and using the radius as a length draw an arc that crosses the
circle. At the point where the arc crosses, reposition the compass on
that point and draw another arc. Keep doing that all the way around
the circle - you will end up with six points including the starting
point on the circle. Connect these points with a straight edge and
Presto! a hexagon. Cut out the hex from the cardboard (I use artists
matte board...) and this is your cutting template. Lay the template on
the material and using an EXTREMELY SHARP XACTO KNIFE cut along the
outside of the template. Make shrouds from a heavy gauge thread -
cut three equal lengths twice as long as the diameter of the chute and
connect the ends to corner points adjacent to each other.
From: Roger....@umich.edu
I usually build 12-24 line round chutes out of Estes material (just cut
around the outside of the red and white circle and attach at the red
/white boundaries) because they look more like real parachutes. I use
embroidery floss for shroud lines and separate the 6 strands (for 12
lines - use two lengths for a 24 line). This makes a strong chute.
With out crossing the lines over the top of the canopy, I've only had
one failure of a 12 line chute (an EL that tipped off dramatically -
i.e. cruise missile) and never had a 24 line fail. In the 10 years
I've been back in the hobby and using this technique, my shroud lines
have always come out the same length (within a couple of percent
tolerance).
From: h...@HQ.Ileaf.COM (Hal Wadleigh)
1. Use fisherman's snap swivels for your attachments. It lets you
store 'chutes separate from rockets and helps prevent fouling due
to spin at deployment.[Note...modelers have always reported mixed
results with snap swivels; they have been known to fail...Buzz]
2. Use nylon coat thread for shroud lines on homemade 'chutes (and
plastic bread wrappers are the best cheap 'chute material).
3. Pay special attention to the security of the attachment points.
Those standard stickers often look secure, but are actually not
attached. A small knot in the part of the shroud line under the
sticker serves as a good anchor point (with the rest of that part
looped around the knot, as per standard practice).
4. Very small 'chutes should be cross-form type. Cut about a 5" square,
then take out about 1.25" squares from each corner. Attach 4 lobes
of shroud across the flat ends and secure as above. Be careful to
use small stickers for the corner attachments. These make good
substitutes for streamers in .5" body tubes and can also be used as
drogues to help in the deployment of large 'chutes [A note from
c...@sw.stratus.com (C. D. Tavares): Either round off the inside
corner of that 1.25" square or reinforce the angle with something.
Otherwise, it's a really handy place for the parachute to rip
during a fast deployment.]
From: sm...@mrcnext.cso.uiuc.edu (Greg Smith)
Nylon coat thread is very good for small, lightweight competition
parachutes, but it's not real strong and does have a tendency to melt if
it encounters a bit too much ejection charge heat. For sport and
payload models with 12" - 24" plastic 'chutes, I use 15 lb. *braided*
nylon fishing line. It's thicker than the coat thread, similar in
diameter to the Estes cotton stuff, but tremendously stronger. In the
last fifteen years, of the plastic parachutes I have built using this
line (and always crossed over the top of the 'chute for reinforcement),
I have had *zero* shroud line or attachment failures. The braided line
has a hard, smooth surface that doesn't encourage tangling, and it
doesn't unravel where cut.
From: whi...@nssdca.gsfc.nasa.gov (Rusty Whitman)
I've tried about everything to keep shroud lines from pulling off of
plastic or mylar parachutes. Those little tape disks are just about
worthless. Tying knots and cyano'ing the ends helps but you still
have problems. I don't know why I never thought of this before but I
ran across a roll of duct tape in my closet and knew immediately that
was the answer. I cut out some little squares of duct tape and
attached some lines to a parachute and they won't pull free without
ripping the plastic. I don't know who invented duct tape but they
deserve some kind of statue, its got more uses than a paper clip.
From: kapl...@hccompare.com (Bob Kaplow)
1. Make shroudlines from Kevlar thread. This won't burn through. Tie
a knot 1/2" from the end and fray the end. Attach that end to
parachute.
2. Use the much stronger kite snap swivels instead of fishing swivels -
make sure they lock, and don't just clip like a safety pin.
-----------------------------------------------------
6.4 Alternatives to Recovery Wadding
From ja...@rml.com (Jack Hagerty):
Just go down to your local building supply store and get a bale of
cellulose wall insulation. This is just shredded newspaper treated in
the same fire suppressant [as Estes recovery wadding]. A $5 bag will give
you enough wadding to last years!
From MAS...@TRAVIS.llnl.gov (Warren Massey):
I have found crepe paper to be a must more cost effective alternative.
It comes in either sheets or rolls (I prefer the sheets) in a variety of
colors and is every bit as flame retardant at a fraction of the price. I
can even get several flights off a single ball of wadding. It is somewhat
stiffer than the tissue but I've never found that to be a drawback.
Unattributed:
A piston ejection system works well on rockets of BT-60 size or greater.
Pistons eliminate the need for recovery wadding of any type. Plans
for a D powered rocket using piston ejection may be found on sunsite.unc.
edu in the file 'pub/archives/rec.models.rockets/PLANS/dust-devil.ps'.
The rocket was designed and drawn by pfei...@nmsu.edu (Joe Pfeiffer).
From: kapl...@hccompare.com (Bob Kaplow)
Use a baffle system (I posted this to RMR a while back) to eliminate
the need for wadding. This also provides the benefit of a third centering
ring (see Pete Olivola article) as part of the baffle system. Stainless
steel mesh can be used to trap hot particles, but be careful that
ejection
caps don't plug it up.
-----------------------------------------------------
6.5 Are there any good tips when making my own nose cones?
From Chris Jennison
To keep nose cones from wobbling and coming out asymmetrical when using
an electric hand drill as a lathe...
Use a blank (dowel, broom stick or balsa block) 1/8 inch larger
(diameter) than the nose cone that you need. Drill a 1/4 in. diameter
hole
as close to dead center as you can and push in a 1/4 in dowel. Dowel
length should allow the nose cone end to seat against the face of the
drill chuck. Find dead center by running the drill clamped in a vise at
moderate speed & slowly move a soft pencil toward the end at what
appears to be the center of rotation. After a couple of tries you will
find the center because your misses will draw concentric circles like
a bullseye. Now remove the dowel from the drill, clamp the shoulder end
in the vise and rough shape the nose cone with a file or rasp using the
marked center as a guide. Final contouring and finishing is done in the
drill with progressively finer sand paper.
-----------------------------------------------------
6.6 Getting Paint to Stick to LOC and Aerotech Nose Cones
From: kwo...@interramp.com (Ken Wolfe)
VERY VERY important......WASH THE PLASTIC FIRST!
I had this problem until I started to wash the plastic before even
assembling anything. This solved most of the problems I was having.
From: Roger....@umich.edu (Roger Wilfong)
I have had success painting nose cones from both companies using Krylon
and Walmart paints. The technique I use is to wash the nose cone with
a Brillo pad followed by a thorough rinse. Fill the mold parting mark
with auto body putty and sand it smooth. I next use a coat of primer
(I've used Krylon's gray sandable, Walmart's gray and Black Baron - the
Black Baron was the best, but also the most expensive and took the
longest to cure). This is followed by a light sanding and another
coat of primer, followed by sanding. After the primer cures (a week, if
I'm in the mood to paint, a year if I'm not), paint it with some paint
that's compatible with the primer.
This technique works fine on the LOC nose cones, the only problem I've
had with the Aerotech nose cones is that the very tip tends to get
chipped off.
I have a LOC PNC-3.00 that has lawn darted into hard ground twice. The
original paint is scratched, but it shows no signs of flaking off.
From: sm...@mrcnext.cso.uiuc.edu (Greg Smith)
I rough up the surface of plastic nose cones with 60 grit paper, then
use my basic epoxy painting regimen as I've described earlier. After
the first coat of primer, the surface is *really* fuzzy; the paint
reinforces and thickens all the little plastic strands that are raised
by the sandpaper, and the surface feels like rough concrete. But a
little sanding knocks off most of it, and after the third primer coat or
so, the surface is as smooth as anything else on the model.
The only time I've ever damaged the finish on one of these nose cones
happened when a model fell off the workbench and onto the concrete floor
in my basement, which chipped the tip of the cone a bit. Normal flying
(including one or two landings on concrete) hasn't affected them at all.
From: js...@rc.rit.edu (J A Stephen Viggiano)
As I have said repeatedly, the most effective way to paint on these
plastics is to introduce carboxyl groups at their surfaces. This will
give the paints something onto which they can grab.
A carboxyl group, also known as a fatty acid group, consists of a
carbon atom, to which an atom of oxygen is doubly bonded, and also
a hydroxyl group is bonded. In order to convert the end of a polymer
chain into a carboxyl group, you need to provide oxygen and some
energy. The oxygen may, of course, come from the atmosphere.
In the packaging industry, when polypropylene and polyethylene must be
printed, they are given either a "corona discharge treatment," in which
the surface is passed beneath a high-potential device called a coratron,
or a "flame treatment," in which a gas flame is allowed to impinge
on the surface for an instant. For historic reasons, the second treatment
may be referred to as a "corona treatment," even though no corona
discharge is involved.
I've used the gas flame from my kitchen range with excellent results.
Don't overdo it, for obvious reasons. Only an instantaneous contact
with the flame is needed.
Since using this treatment, I have had virtually no problems with paint
flaking from my polypropylene nose cones.
From: M Preddy <pre...@ucs.orst.edu>
I've had good luck with Rustoleum primer on LOC nose cones. Krylon
sticks to it fine.
From: kapl...@hccompare.com (Bob Kaplow)
Consider covering nose cones with econo-kote.
-----------------------------------------------------
6.7 Is it possible to get a high gloss, durable finish on a model rocket?
From: p_ham...@usa.pipeline.com (Paul Hamilton)
I put on a clear coat of dope or Krylon, sand with #600 wet-or-dry
sandpaper, and then buff with "Rotten Stone" or similar rubbing compound.
This is a fine abrasive that on mixes with water. I have used toothpaste
or silver polish as a substitute for rubbing compound when there has been
no hardware store around.
-----------------------------------------------------
6.8 Are there any good paints for silver details on scale models?
From: Orville ????
The Krylon silver paint looks very much like real silver, that's
because it's made of a clear coat plus real metal flakes.
The only problem is when you touch it the finish becomes dull.
The solution to this problem is:
Finish your surface as usually.
Spray a final coat of Krylon on and let dry 2 days, but don't
even think about touching it. After 2 days spray Krylon clear coat
over the silver with very light coats ,letting each coat dry 5 minutes
between sprayings. This will give you a very nice finish.
From: Peter "wondered if they had silver spray paint for the Tin Woodman's
axe in the Wizard of Oz" Alway (al...@pooh.physics.lsa.umich.edu)
I'm starting to get serious about silver paints, now that I am working
on 1930's rockets. I think it's worth getting a sense of several
metallic colors, all for different purposes. As near as I can tell,
most are either simply glossy (Testors Chrome, Dutch Boy silver) or
matte (Testors silver, and apparently Krylon.
As an experiment, I tried buffing some Testors siver on a nose cone
(it was still chucked up on the drill press wher I turned it) last
weekend. I found I needed to use dome #600 sandpaper to get a truly
smooth surface, then I just buffed it with ordinary paper. The result
was pretty convincing, but a darker shade than the original
paint. (unfortunately, on Goddard's rockets, the nose was usually
a lighter shade of Aluminum) I was impressed that the result looked
like real metal to me.
Testors has some buffable paints in their Metalizer line. I tried their
"Titanium" on a Glencoe 3-stage rocket ship (a von Braun design), but
when polished, I thought it looked more like hematite than actual
metal. I'm starting to believe that with silver paint, it's more
important that you represent the differences between silver shades
than get the siver just right. So for instance, on a Goddard
rocket, I would use the glossy Dutch Boy silver for the nose cone,
buffed silver paint for the nickel-steel propellant tanks, and
testors silver for the duralumin body. This should at least
suggest the differences between the materials that you can see
in the photos.
From: Bob Craddock (crad...@aol.com)
After building and re-building about a half-dozen Saturn V's, I have a
couple of recommendations to make:
For the Service Module color, I suggest getting a bottle of Micro Metal
Foil Adhesive and some Reynold's Wrap. Spread the adhesive on the
**shiny** side of the foil. The silver on the SM was somewhat dull, and
just about ANY silver paint sucks badly! The foil will give you the
look
you need, and the adhesive is extremely easy to work with. The white
raditor details can be added by using shroud line or Evergreen styrene
strips. White glue works well with the shroud line, but I would
recommend
fast epoxy for the strips. Mask of the radiator areas so you can paint
them white when you paint the entire rocket.
-----------------------------------------------------
6.9 How can I prevent a rocket painted white from yellowing?
From: cur...@telerama.lm.com (LarryC)
Future floor polish (it isn't wax) doesn't yellow. I find it useful for
rockets but...
1) It must be used over some kind of paint or over acrylic gesso. If it
seeps into cardboard or wood, the material will become brittle;
2) It will cause dope and (even permanent) Magic Marker color to run.
This effect can be used to advantage, but it can also ruin a model if
it's unexpected. Future does not cause enamel paint to run, and may
certainly be used to cover decals. Don't know if the decal will yellow
beneath the coating.
3) A glossy finish is not always desirable, and Future yields only a
glossy finish. Art stores sell equivalent mixtures that come in gloss
or matte finishes. The are called "Acrylic Gloss Medium," and "Acrylic
Matte Medium," respectiely. They are thicker than Future, but they can
be thinned with water.
4) Acrylic colors, available in art stores, can be used on rockets, as
long as acrylic gesso is laid down first. The colors should be thinned
with water or Future. Acrylic paints are normally labeled to tell you
how opaque they are and how toxic they are. Both qualities vary from
color to color. Even though the tubes seem expensive, the opaque colors
have excellent covering power and they turn out to be very good buys.
5) From my own experience, commercial acrylic model paints are to be
avoided. They are over-thinned, and they yeild undesirable, cracked
finishes.
From: kapl...@eisner.decus.org (Bob Kaplow)
Try adding a small amount of BLUE to the white paint (a few drops per
bottle). The faint blue tint hides the yellowing, much like bluing in
the white laundry.
-----------------------------------------------------
6.10 Which is better, white or yellow glue? Epoxy? Cyano?
From: buz...@netcom.com (Buzz McDermott)
Yellow wood glue, such as Elmers Carpenter's Glue or Titebond, is far
superior to regular Elmer's white glue for building wood and paper model
rockets. Built carefully, with proper fin fillets, yellow aliphatic resin
will hold together on rockets with up to G power. Yellow glue also dries
faster.
Three and five minute epoxy is often used for quick repairs. This quick
drying time does not allow the epoxy to soak into the wood and/or paper
very well, though. If epoxy is to be used, then use one with at least
a 15 minute, and preferably a 30 minute, listed 'drying' time. Thirty
minute epoxy will give a much stronger bond than yellow glue. However,
5 minute epoxy often yields a weaker bond than yellow glue.
Cyano is often used for quick building. It bonds strong, dries extremely
fast (especially when using an accelerator), and is relatively easy to
use. Regular cyano can also be used to bond plastic to wood or paper.
No matter which glue is used, the most important factor is to have a
properly prepared surface. Glassine coated Estes-stype body tubes should
be lightly sanded where the glue is to be applied. All bonding surfaces
should be clean and unpainted. You want whatever bonding agent is used to
be able to soak into the paper and/or wood.
From: kin...@sisko.dnaco.net (kingrat)
I've been using CA to bond fins to the tube and then a fillet of
epoxy. If you go this route I recommend thin CA and a fin alignment
guide. Make sure the fins are aligned properly before you CA and check
again before applying the epoxy. Unlike white glue, if you mess up it's
REALLY hard to fix. It's also REALLY hard to pop the fin off too. :)
This works just fine with balsa or plywood fins from what I've seen. CA
is good for tacking the lugs in place too, however I would never use CA
on a vital part of the rocket (ie. motor mount) CA just isn't strong
enough because it turns brittle. Epoxy will flex somewhat without
breaking
and you can add microballoons to allow it to flex even more. In
short, use
CA to tack and epoxy to bond.
From: san...@ibm.net (Bob Santore)
There is an easy test to tell if the glue you are using is strong enough.
A glue joint only needs to be as strong or stronger than the material it
is gluing together. To test for glue strength you need to test the
strength of the glue joint relative to the strength of the material you
are bonding. This test is very easy and can be used for any type of
glue.
Glue some scrap pieces of whatever you are gluing together in a
configuration similar to how you intend to use it (i.e., don't test a
surface mounted fin if you intend to use a TTW fin). When cured,
pull the
two parts apart. Did the glue bond fail? If it did, don't use that
brand
of glue. If the pieces you glued didn't fail, then this glue is fine.
If your rocket falls apart anyway, then you need stronger rocket parts!
The only exception I can see to this very simple test would be near the
motor mount where heat can weaken the glue. You could always heat the
pieces before destructive testing to see if heat changes the
properties of
the glue joint.
-----------------------------------------------------
6.11 Improving on the Estes Shock Cord Mount
There are a number of ways to improve on the old paper-and-rubber-band
shock cord mount used by Estes for the past 35 or so years. The
following suggestions have been repeatedly made in r.m.r.
1. Replace the rubber band or short elastic in the kit with sewing elastic
at least twice the length of the model. This will help to avoid
tube zippering or ripped out shock cord mounts when you have a 'hard'
ejection.
2. Epoxy the shock cord mount to the inside of the body tube rather than
using white or yellow glue. Thirty minute epoxy works best for this.
Be sure and lightly sand the inside of the tube where the shock cord
mount is to be placed. Also be sure and 'cover' the entire mount with a
very thin layer of epoxy. This method works best for models with BT-60
or larger body tubes.
3. Use a 'Quest-style' kevlar-and-elastic shock cord mount. This type
of mount uses a length of 50 to 150 pound test Kevlar (such as Stren
Kevlar fishing line or Kevlar kite string). The Kevlar is tied and
glued to the motor mount (motor block, centering ring, or around the
motor tube). It is sized to end just shy of the front end of the
body tube when a length of elastic shock cord is tied onto the free
end of the Kevlar. This method eliminates any shock cord mount on the
inside surface of the body tube. Estes-style shock cord mounts have
been known to interfere with parachute deployment. You can used this
method on any sized rocket. Size the Kevlar appropriately.
4. You can also use a 'LOC-style' shock mount for body tubes in the
1.5" and up range. With this you take a short length of Kevlar line,
fold it in half, and make a !-2" loop in the closed end of the folded
line. You then epoxy the loop to the inside of the body tube in such
a manner as to have the end of the loop extend a little past the open
end of the body tube. A shock cord is tied to the loop. The advantage
of this technique is that is allows damaged shock cords to be easily
replaced. It tends to work better on body tubes greater than 1.5"
in diameter.
-----------------------------------------------------
6.12 I've built several BT-80 based models. How can I strengthen future
models to take larger motors, such as Aerotech 24mm or 29mm reloads?
Estes recommends using just D motors in their BT-80 based kits, such as
the Broadsword (Super Big Bertha) and Shadow (Optima). There are a number
of steps that posters to r.m.r have done to strengthen these rockets to
fly with larger motors. Remember in doing this that you are modifying and
using the rocket kit in a manner NOT recommended by the manufacturer.
From: Buzz McDermott (buz...@netcom.com)
Here's a summary of what I've done to strengthen my Shadow and Broadsword
kits to fly on 24mm reloads and up to 24mm G42 motors. You will need
a LOC-style 2.56 inch tube coupler, 3/4 oz fiberglass, 15-30 minute
epoxy, and 20 minute 'coating' or 'finishing' epoxy:
1. If the kit comes with the 'plain' BT-50 type motor tube, replace
that with LOC-type, thick-walled 24mm motor tube. You will only
need about 6".
2. Reinforce each body tube section with 3/4 oz fiberglass. Apply it
using
one of the methods discussed in the section on High Power Construction
Techniques. Be sure to completely sand off the glassine coating of
the
body tubes prior to applying the fiberglass.
3. Also fiberglass-reinforce the thick paper centering rings supplied
with the kit. Glass both sides of the rings. If you want to build a
payload section in the Shadow, then leave the center cut-out in one
of the rings and glass over it.
4. If you plan to use only 24x70 disposable motors (including Aerotech
E's) and/or 24mm reloads, then yellow glue or epoxy a motor block
2.5" into one end of the 6" motor tube. If you install the motor hook,
file down the part that sticks into the tube. This will let you
fit in 24mm reloads. Be sure and lightly sand the motor tube prior
to installing motor hook. [NOTE: If you plan to use non-standard 24mm
Aerotech motors than skip this step.]
5. Epoxy one fiberglass-and-epoxy-reinforced centering ring 1/2" from the
rear end of the motor tube. Be sure there is a notch in the ring to
allow some movement of the motor hook. Epoxy a second centering ring
in the middle of the motor tube. Epoxy a third ring 1/8" from the
front of the motor tube. Install the motor tube into the main
body tube with the motor tube flush with the bottom of the main body
tube.
6. Fiberglass-reinforce all of the fins. Apply the glass to both sides
of the fins. Be sure that the fins are completely sanded (and any
airfoiling/rounding completed) before applying the cloth. An optional
step is to apply some 1/2" wide strips of glass along all of the
fin edges EXCEPT the root edge.
7. Rough up the epoxy on the main body tube along the lines where the
fins will attach. Use 220 or coarser sandpaper. You really want the
smooth epoxy coating roughed up. You can also drill a few 'rivet'
holes along the fin attachment lines.
8. Apply epoxy where the fins will attach and attach the fins. Do not
fillet at this time.
9. When the fins are dry, apply 1/2" strips of fiberglass cloth along
each fin root edge, with 1/4" on the body tube and the other half of
the width along the fin side. Coat this will coating epoxy. When
dry, YOUR FINS WILL NOT COME OFF.
10. Couple the bottom two body tube sections together. An option step
is to make a payload section out of the third body tube section that
comes with the Shadow. Use the LOC coupler to make a payload section.
You can sand down the solid centering ring to slide inside the LOC
coupler to form a bulk-head. Epoxy a 2"x 2" piece of scrap 1/16"
plywood or 1/8" balsa to the inside surface of the bulkhead to add
strength. Install either a large screw-eye or small eye-bolt to the
center of the bulkhead, to be used to shock cord and parachute
attachment.
The end result of the above is a model which is really too heavy to
fly on a D12. My modified Shadow came out to about 14 oz (I built it
VERY heavy and added the payload section). My modified Broadsword came
out to about 12 oz. Both have been flown on motors as small as composite
D's (D21-4, D13-4R). The Shadow has flown on E15-4 (perfect), E30-4
(a -5 is really needed), F24-7R, F39-7R, and G42-8. The Broadsword
has just been test-flown on the D21-4 and E15-4. It WILL be flown on
G42's, though.
If you want to use 29mm motors in BT-80 based models, I would recommend
either switching to plywood centering rings or sticking to low-thrust
motors, such as the F14. In the end, if you want to fly 29mm, you would
really be better off getting a kit designed as a Large Model Rocket from
the start.
---------------------------------------
6.13 How can I prevent balsa fins from breaking off on landing (especially
for models with swept fins)?
From: Bob Craddock (crad...@aol.com)
Take your fin pattern, reduce it by ~90% on a xerox machine, and make
as many copies as you need to glue one pattern on both sides of each
fin. Put about two coats of sanding sealer on the new paper surface,
sand, and then paint the fins all over again. A friend of mine was
having the exact same trouble on his Super Big Bertha, and the paper
reinforcement was his solution. It worked great, but next time I
say use
bass wood on everything.
From: The Silent Observer (sil...@ix.netcom.com)
There's a variation on this technique, that needs to be applied during
building, that can make balsa fins stronger than bass (and still
lighter).
What you need to do is simply to cover the fins before painting.
I used silk tissue (like model airplane tissue made from silk
fibers) on my
Big Bertha, and in a dozen flights (before it lodged high in a tree)
never
had so much as a crack, even when flown on a D21 (and including one
"plastic wad" recovery when the rocket hit the ground fairly hard).
You
could use ordinary Japanese tissue, or Silkspan (R), or you could
even use
something like nylon cloth or very light fiberglass (attached with
epoxy or
CA in this case).
With tissue, you need to cover the entire surface -- I simply
wrapped it
over the rounded leading edge, and trimmed it off at the tapered
trailing
edge, leaving the square "bottom" edge and the root uncovered. You can
attach Silkspan with almost any glue, but silk tissue (as I found)
"fuzzes"
if you get it damp and handle it, so something like Testor's model
airplane
glue or thick, clear nitrate dope might be a better choice; it won't
soften
the binder that holds the fibers in the tissue together.
Any of these, done after sanding (and filling, in the tissue cases)
will add
significantly to the strength of the fin, while adding very little
weight.
Making fins out of basswood or ply is probably okay with a Bertha
derivative
-- they tend to be overstable in any case -- but may lead to an
unstable
model if you have a design with less margin.
From: David Bucher (dbu...@mcn.org)
There are two things you can do, both of which lower the rocket
in a "fin up" attitude. The first works by making a "yoke" or
harness for
lowering the rocket body horizontally ( if you choose). Install an
anchor
(screw eye, inch worm shaped brass wire clip etc.) through the body
tube
wall between the fins at the rear end of the body. Attach a squid
line or
kevlar thread to the anchor and run it up the outside of the body
(tightly)
and attach to the nose cone or 'chute. Configure it to lower rocket as
above.
The other (and better!) way for the rocket you describe is to use rear
ejection. This will not help you with the present rocket, but any other
rocket with sufficient body width will work just fine. When making the
motor mount assembly. substitute a longer motor tube (29mm LOC
tube for instance) and make up some ply or G10 centering rings
including
two with a fair spread between where you can wrap the 'chute around
the motor tube. Install a solid bulkhead with cable lanyard to serve
as a thrust ring and pressure block. Make sure the motor mount unit
slides well in the body and attach elastic to the cable lanyard and now
you've got a rocket that ejects to the rear. Just cut a small notch
in the
farthest forward centering rings to allow the shock cord to pass.
This me-
thod works great and if you're confused by what I just wrote (a not un-
heard of possibility!) just think of the internal "power pod" in some
BGs. It works the same way except you must make provision to conn-
ect ALL parts together. There are two things you can do, both of which
lower the rocket in a "fin up" attitude. The first works by making a
"yoke" or harness for lowering the rocket body horizontally ( if you
choose). Install an anchor (screw eye, inch worm shaped brass wire
clip
etc.) through the body tube wall between the fins at the rear end of
the
body. Attach a squid line or kevlar thread to the anchor and run it up
the outside of the body (tightly) and attach to the nose cone or
'chute.
Configure it to lower rocket as above.
---------------------------------------
6.14 I just lost my favorite rocket and the kit is discontinued. How can I
make another one just like it?
From: <sil...@ix.netcom.com> and <bmcd...@ix.netcom.com>
I don't know if everyone else already does this, but I've started
saving the
kit card, instructions, and a copy of the fin shape or shapes for
every kit
I build -- rockets have a way of getting lost or broken, and model
rocket
companies have a way of discontinuing my favorite kits. Getting a
color copy
of the decal sheet (or better yet, a color scan) is also a good idea.
---------------------------------------
6.15 How can I reduce damage to the booster stage of two stage models caused
by the engine exhaust of the second stage?
From: phu...@numill.com (Perry Hunter)
Try scotch tape instead of masking tape. It should release fractionally
faster and >might< reduce scorching of the lower stage.
In some cases, it's possible to line the inside of the top of the lower
stage with 20lb xerox paper, and it will take the damage rather than
the exposed section of the stage. It's not possible to cover everything
(slip fit couplers , etc. prevent lining all of it) but it can help.
---------------------------------------
6.16 Is there a way to increase the stability of a model with near
neutral stability?
From: Peter "My views are not to be confused with those
of a rabbit librarian" Alway (al...@pooh.physics.lsa.umich.edu)
Sounding rockets that are aerodynamically stable are often spun at a
slower rate that insures that any off-axis thrust will cause the
rocket to corkscrew, rather than follow an arc. The corkscrew may
be subtle--but it beats an equally subtle arc. A sounding rocket
that naturally describes an arc with a 20-mile radius due to its
asymmetries cannot reach higher than 20 miles. But if the rocket
is spun through 360 degrees every few hundred feet, the
20-mile-radius arc turns into a very suble corkscrew.
Imageine the modeler puts a very slight misallignment between the
forward and rear fins of a sidewinder. Suppose it's just one degree.
also suppose the fins are 1 foot apart. the rocket will naturally
arc in a circle with a 360-foot circumference and a 57-foot radius.
That's instant doom! make the error half as bad and you are in
trouble. But if the rocket spins every 10 feet, the path will be
a generally upward corkscrew, less than ideal performance, but
a safe flight.
So with model rockets, a spin on ascent is a good way to make a
marginal or asymmetrical model safe. Estes used to sell a space
shuttle orbiter kit that had a spin tab for this reason, and the
old Astron Space Plane had spin tabs as well.
---------------------------------------
6.17 How can I build a rocket with less wind resistance?
From: John DeMar (smd...@mailbox.syr.edu)
The best thing you can do is to NOT use launch lugs. Use a
launch tower instead. A polished, smooth finish makes a big
difference too. If the design allows, use a boattail and make
sure all transitions are smooth (from nosecones/payload sections,
etc.). Fin shape is a minor affect if they are relatively thin,
otherwise make sure the edges are at least rounded.
Here are some numbers for comparison:
Standard finish, no transitions, with lug: Cd = 0.88
Standard finish, no lug: 0.68
Polished finish, no lug: 0.61
Standard finish, no lug, 2:1 boattail: 0.52
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Copyright (c) 1996 Wolfram von Kiparski, editor.