Christavia Mk 4 Plans
Satcinc
designer is notr currently offeringthese plans for sale
Thanks
Rob
Charles K. Scott
sat...@aol.com (Satcinc) writes:
I'm building a Christavia Mk 4 and if I was starting again I'd just buy
the Bearhawk plans instead. Basically a similar aircraft but metal
wings and much faster cruise with almost as low a stall speed.
Maybe it won't lift as much but on the other hand I'm not going to be
hauling Moose out of the bush nor do I intend to bring the word of God
to jungle natives (Christavia means "Christ in Aviation", the designer
is a born again person and literally designed the airplane for
missionary work).
Corky Scott
Satcinc
Thanks for the reply on the Mk4, Could you tell me what your probelms are with
it?? I was looking for a 4-seat tube/fabric, and it seemed to fit the bill.
Nut Elmwood Av. isn't offering the plans for sale due to the unavailability of
spar stock (??)
Love to here any further comments you have
Thanks
Rob Staudt
highflyer
Good wood for spars has been hard to find for the last thirty years
or so. There are a number of viable alternatives. The easiest and
most foolproof is to merely laminate up the size you wish for the
spar from smaller pieces. If you carefully select the pieces and
laminate them accurately with properly made and distributed scarf
splices on the pieces that are too short you will wind up with a
spar that is stronger and better than a solid piece of selected wood.
The lamination process allows you to eliminate any small defects
you find, and ensures that any small compression failure or other
defect that you FAIL to find will not be nearly as serious.
That being said, the Bearhawk is a similiar airplane with no spar
material problems and excellent builder support. Give it a good
look.
HF
Charles K. Scott
sat...@aol.com (Satcinc) writes:
> Corky,
>
> Thanks for the reply on the Mk4, Could you tell me what your probelms are with
> it?? I was looking for a 4-seat tube/fabric, and it seemed to fit the bill.
> Nut Elmwood Av. isn't offering the plans for sale due to the unavailability of
> spar stock (??)
>
> Love to here any further comments you have
>
> Thanks
> Rob Staudt
I already replied to Rob via e-mail and didn't realise he'd posted here
as well.
Basically I have no problem with the Christavia 4 plans although I
thought I did once. There are some minor discrepancies in the
measurements and quantities of bolts and things but nothing serious.
There are some changes in the plans that are at the end of the
construction manual or separate sheets and it pays to read EVERYTHING
through several times in order to make sure you don't build something
to the wrong dimension because the correction is at the back of the
manual.
I didn't like the flap upstop design and modified it so that I could
make adjustments to where the flaps stop which allows me to
incrementally adjust them for best cruise setting (ground adjustment
only).
Other than that, as long as you bear in mind that you are building an
experimental category homebuilt, not a certified airplane and that
changes, as long as they do not affect the overall integrity of the
design are OK, no one should have any problem building the airplane.
The lack of Sitka Spruce for spar material should not stop anyone since
Douglas Fir is readily available and is considered a one to one
substitution by the FAA.
One thing people should understand about the Christavia Mk 4 though, it
is not a light weight puddle jumper. The wings are massive and cannot
be handled by a lone person. It's all my wife and I can do to flip it
over when necessary. Thank God she doesn't mind doing that. I'll take
that back, she minds but is willing to assist.
Corky Scott
Charles K. Scott
Charles.K.Scott@**NOSPAM**.dartmouth.edu (Charles K. Scott) writes:
> Other than that, as long as you bear in mind that you are building an
> experimental category homebuilt, not a certified airplane and that
> changes, as long as they do not affect the overall integrity of the
> design are OK, no one should have any problem building the airplane.
Another example of reasonable modification, something I haven't done
but may; a builder I know is using square tubing for the door opening
rather than the round tubing as specified. The builder did this
because it's a lot easier fabricating the stops for the door on the
square tubing than it is adding them to round tubing. I do not know if
the designer approved this substitution. The builder reported no
difficulties in using the square tubing and actually has the fuselage
finished and is well into the wings at this point.
My gut feeling, without any engineering input or consultation is that
given the tubing diameters and wall thicknesses of this extremely
robust fuselage, substituting the square tubing, as long as original
wall thickness is maintained, isn't going to cause any catastrophic
failures. But if there are engineers out there who would care to
comment, I think this is a worthy discussion.
Thanks, Corky Scott
Shelly
Christavia Mk1 and recently bought plans for the Bearhawk. I never cared
for the appearance of the Christavia Mk4, but the Bearhawk has a lot going
for it. By the way, the Christavia has been a wonderful airplane for 8
years! I will never sell it!
Bruce A. Frank
The door is not a structrual component. If the plans called for 1/2 inch
tube for the door frame and one substituted 1/2 inch square it would be
stronger than the original. Round tube is used for fuselage fabrication
because it is the strongest structrual shape for the amount of material
used. A fuselage built from square tube would be heavier if cross
sectional sizes were kept the same. Since there is more material in the
square tube then equiv. strength may be maintained with a slightly
smaller square tube, BUT there are other structrual considerations.
Minor damage to square tube may cause failure, under maximum loads,
whereas round tube of equal tensile strength better maintains its
integrity under the same maximum load. Stress to a section of dented
round more easily transfers around the defect that it does in a section
of square tube. Such a defect in a round tube may not lower its failure
point below the designs requirements. The same damage to square tube may
cause an overload situation in the surrounding material. Substituting
square for round in a non-structrual door likely will not cause a
problem. I have done exactly that in my project.
--
Bruce A. Frank, Editor "Ford 3.8/4.2L Engine and V-6 STOL
BAF...@worldnet.att.net Homebuilt Aircraft Newsletter"
| Publishing interesting material|
| on all aspects of alternative |
| engines and homebuilt aircraft.|
*------------------------------**----*
\(-o-)/ AIRCRAFT PROJECTS CO.
\___/ Manufacturing parts & pieces
/ \ for homebuilt aircraft,
0 0 TIG welding
While trying to find the time to finish mine.
Shelly
since I built a Hiperbipe, which used square tubing for fuselage, doors,
and generally throughout the entire project. It was a very strong airplane
and even though I never flew it, it came through the tornado in '85 in
better shape and with less structural damage than 21 other planes and
several hangars.
Also, square tubing makes window installing a whole lot easier and stronger
- gives you a flat surface to attach the lexan or whatever!!
Shelly
Charles K. Scott
"Bruce A. Frank" <BAFRANK@**MailBlockŽ**.worldnet.att.net> writes:
> Substituting
> square for round in a non-structrual door likely will not cause a
> problem. I have done exactly that in my project.
Not sure I made myself clear here Bruce, what I meant was that while
constructing the fuselage and cutting and welding the door opening, he
used square tubing for the door outline and butted the round tubing to
it to continue the fuselage construction. So this would be an integral
part of the fuselage structure, unless you're telling me that the door
opening itself, not the door but the opening, is not structurally
significant.
That's why I was asking, I was thinking that this part of the
structure.
Corky Scott
Robert McDonald
(Charles K. Scott) wrote:
>Another example of reasonable modification, something I haven't done
>but may; a builder I know is using square tubing for the door opening
>rather than the round tubing as specified. The builder did this
>because it's a lot easier fabricating the stops for the door on the
>square tubing than it is adding them to round tubing. I do not know if
>the designer approved this substitution. The builder reported no
>difficulties in using the square tubing and actually has the fuselage
>finished and is well into the wings at this point.
>
>My gut feeling, without any engineering input or consultation is that
>given the tubing diameters and wall thicknesses of this extremely
>robust fuselage, substituting the square tubing, as long as original
>wall thickness is maintained, isn't going to cause any catastrophic
>failures. But if there are engineers out there who would care to
>comment, I think this is a worthy discussion.
>
>Thanks, Corky Scott
Interesting idea. As an Aerospace Engineering student, (over 20 years
ago), I started working on a design for a biplane that was intended to be
quick and easy to build, (I was impatient to get back into the air). One
of my profs suggested that I design the whole thing around square tubing
to simplify fabrication - build the whole thing with a mitre saw and
oxyacetylene torches :-) Of course it would weigh more than an
equivalent structure built with round tubing.
Hmmm, come to think of it that may not be a bad idea...
Rob McDonald
P.S. I'm not an Aeronautical expert, I switched to Mechanical Engineering.
-
Bruce A. Frank
Sorry, sometimes reading late at night not all points are clear. But, I
did address this, if you replace the round with the same section (1/2"
round by 1/2" square) of square in a door frame you actually have a
stronger, but heavier, structure.
Bruce A. Frank
round tube ones.
--
Bruce A. Frank
ones? THe switch over would be easy in planes such as the Christavia
because the airframe and gross are similar to several in the Piper
series and other plans built such as the 2+2 Sportsman.
highflyer wrote:
>
> Satcinc wrote:
> >
> > Corky,
> >
> > Thanks for the reply on the Mk4, Could you tell me what your probelms are with
> > it?? I was looking for a 4-seat tube/fabric, and it seemed to fit the bill.
> > Nut Elmwood Av. isn't offering the plans for sale due to the unavailability of
> > spar stock (??)
> >
> > Love to here any further comments you have
> >
> > Thanks
> > Rob Staudt
>
> or so. There are a number of viable alternatives. The easiest and
> most foolproof is to merely laminate up the size you wish for the
> spar from smaller pieces. If you carefully select the pieces and
> laminate them accurately with properly made and distributed scarf
> splices on the pieces that are too short you will wind up with a
> spar that is stronger and better than a solid piece of selected wood.
> The lamination process allows you to eliminate any small defects
> you find, and ensures that any small compression failure or other
> defect that you FAIL to find will not be nearly as serious.
>
> That being said, the Bearhawk is a similiar airplane with no spar
> material problems and excellent builder support. Give it a good
> look.
>
> HF
--
Owen Davies
>Interesting idea. As an Aerospace Engineering student, (over 20 years
>ago), I started working on a design for a biplane that was intended to be
>quick and easy to build, (I was impatient to get back into the air). One
>of my profs suggested that I design the whole thing around square tubing
>to simplify fabrication - build the whole thing with a mitre saw and
>oxyacetylene torches :-) Of course it would weigh more than an
>equivalent structure built with round tubing.
Might need some fairing strips, so the fabric wouldn't have to bend around
those sharp corners. Other than that...
How much more expensive is square 4130 tubing than round? I'd expect
a significantly higher price in light of the smaller market.
Owen Davies
highflyer
You might want to look in the Wicks catalog or some similiar reference
with attached prices. Not only is the square 4130 more expensive, but
it is also available in fewer sizes.
On the other hand, in mild steel welded tubing, there are a wide variety
of sizes and shapes of square and rectangular tubing for a host of
purposes. They even have sizes that are designed to nest such as they
use for a "receiver" type trailer hitch.
Of course, any sequence of .049 wall round 4130 tubing where the
diameters differ by 1/8 inch, will nest nicely also. You normally
use the next size tubing for splice gussets on tubing splices.
HF
Bruce A. Frank
4130 tube. But, the sizes needed for the main structrual members such as
longerons and and truss bracing are the ones that are common. These are
the areas where effort can be saved with the square tube. The sizes I
find readily available in 4130 square are 1/4", 1/2", 3/4" and 1"(wall
thickness running from .049" to .065" and thicker). For a full size
fuselage I think there are few parts that I could not build with these
sizes.
--
Charles K. Scott
"Bruce A. Frank" <BAFRANK@**MailBlockŽ**.worldnet.att.net> writes:
> HF is correct that the sizes of square tube is limited compared to round
> 4130 tube. But, the sizes needed for the main structrual members such as
> longerons and and truss bracing are the ones that are common. These are
> the areas where effort can be saved with the square tube. The sizes I
> find readily available in 4130 square are 1/4", 1/2", 3/4" and 1"(wall
> thickness running from .049" to .065" and thicker). For a full size
> fuselage I think there are few parts that I could not build with these
> sizes.
This is just great news to hear. There's no question now that I'll be
using square tubing for the door opening. It just makes fabricating
the door stop and everything attached, including the hinges, SO much
easier.
I can't wait to begin the fuselage, I just have this pesky wing to
modify and finish up.
Corky Scott
highflyer
When I go through my plans collection, or even look at the nude
fuselages around the hangar, I do see quite a lot of square tubing
used in those places where hinges go or complicated fitting would
result from round. Framing openings is a good place to use the
square tubing.
I used square tubing ( 4 inch square, 14 gauge mild steel welded )
to build the framework for my hangar door. It worked quite well,
even if Oysterhouse promptly branded it a "kludge."
HF
Bruce A. Frank
>
> > HF is correct that the sizes of square tube is limited compared to round
> > 4130 tube. But, the sizes needed for the main structrual members such as
> > longerons and and truss bracing are the ones that are common. These are
> > the areas where effort can be saved with the square tube. The sizes I
> > find readily available in 4130 square are 1/4", 1/2", 3/4" and 1"(wall
> > thickness running from .049" to .065" and thicker). For a full size
> > fuselage I think there are few parts that I could not build with these
> > sizes.
>
> This is just great news to hear. There's no question now that I'll be
> using square tubing for the door opening. It just makes fabricating
> the door stop and everything attached, including the hinges, SO much
> easier.
>
> I can't wait to begin the fuselage, I just have this pesky wing to
> modify and finish up.
>
> Corky Scott
Uh, Corky, I have another suggestion. Find a basket case TriPacer or
Colt and use it as the "kit" for your Christavia. You can find
engine-less fuselages for $2000 or less then take a hacksaw and modify
it as much as you desire to emulate the Christavia. All the time
consuming detail, such as pulley mounts, gear mounts, trim mechanism and
a bunch of alignment proceedures are already done. And, the biggest
saving is that you will spend as much if not more for the tube to build
the Christavia (plus several years of your time).
Charles K. Scott
"Bruce A. Frank" <BAFRANK@**MailBlockŽ**.worldnet.att.net> writes:
> Uh, Corky, I have another suggestion. Find a basket case TriPacer or
> Colt and use it as the "kit" for your Christavia. You can find
> engine-less fuselages for $2000 or less then take a hacksaw and modify
> it as much as you desire to emulate the Christavia. All the time
> consuming detail, such as pulley mounts, gear mounts, trim mechanism and
> a bunch of alignment proceedures are already done. And, the biggest
> saving is that you will spend as much if not more for the tube to build
> the Christavia (plus several years of your time).
Too late Bruce, I already have an 800 lb. box of 4130 tubing I bought
from a guy who didn't want to start his Skybolt. I saved too much
money not to use it. Besides, I've got this deal going with me, I
don't charge me for labor. :-)
Corky (what's the use of owning a joint jigger if you don't use it)
Scott
Bruce A. Frank
That is a good start. Eight hundred pounds! You may have all the tube
you need. Oh, BTW, pick up an extra set of bushings for that Joint
Jigger. They wear very fast.