BT Marking
bob fortune
>
> Hello
> I'm upscaling a Loc Lil Nuke. I need to mark a 4 inch body tube for a 3 fin
> rocket. What is the best way to mark the bt for the 3 fins?
> Thanks
> Mike
hey mike,
i draw the circle and fin locations up on a computer program which has
scalable rulers, print it out, set the bt on the paper then mark the bt but i
don't know if you have this available to you.
the only way i can think of is kinda clunky but it should get pretty close. if
the bt is 4" in diameter the circumference would be pi times diameter or
3.1416 etc. times 4 or 12.5664. (you can check with a piece of paper by
overlapping it on the tube, marking the paper and measuring on a ruler)
divide this by three to get 4.188.
take the piece of paper you measured the tube with and mark it at 0", 4.188"
(the fraction is going to be a bit bigger that 1/8 maybe 3/16"), and 8.376".
put the paper on the tube and transfer the points et voila'.
i've found that for drawing the axial fin marking lines on a bt an aluminum
sliding patio door has a nice fat straight edge, often straighter and taller
than a door casing.
another thing i've found is (this is for smaller diameter rockets that have a
fin marking guide on the instructions) if i put removable scotch tape over the
guide i can mark the tape, peel it off, stick it on the tube and transfer the
marks. no fussing around with cutting the guide or taping the guide to the bt.
are you going to fly this tomorrow? : ) have fun!
bob fortune
Steve Piette
>
> Hello
> I'm upscaling a Loc Lil Nuke. I need to mark a 4 inch body tube for a 3 fin
> rocket. What is the best way to mark the bt for the 3 fins?
> Thanks
> Mike
Use VCP to print a fin placement guide. Tell it the number of fins, the
BT diam,
root lenght and thickness, and cant ( fin angle from the centerline ).
For a
4" BT if you only have 8.5x11 paper, you'll have to cut and tape two
sheets
together. After a while you'll have a set for the tubes you use.
For those without computers, remember that you can use a compass set to
the
radius of the BT to draw a circle and divide the circle into 6 equal
parts
by placing the compass center on the circle and marking the arc where it
intersects the circle. Move the compass center to that point and repeat.
For a three fin rocket use every other point for the fins. Make a big
circle
and draw a line between the points and you get a hexagon, great for
parasheets.
--
Steve Piette Applied Computer
Technology
st...@simon.chi.il.US. 7N852 Phar Lap Drive
(630) 513-6920 St. Charles, IL
60175-6868
-------------------------------------------------------------------------------
Shick68
Gordon S. Hlavenka
> I need to mark a 4 inch body tube for a 3 fin
> rocket. What is the best way to mark the bt for the 3 fins?
Here's a nifty way to mark fin spacings on BTs:
Wrap a piece of paper around the tube, and draw a line at the overlap
point.
Lay a ruler on the paper so that the zero mark rests on the edge of the
paper, and aome number divisible by the number of fins is exactly on the
overlap line. This will be a diagonal of some sort, but it doesn't have
to go corner-to-corner.
Mark the paper at the appropriate divisors.
Wrap it around the tube again, and transfer those marks as fin
positions.
For example, let's say I want to put 5 fins on a BT-60.
When I wrap and mark the paper, I end up with a length of just about
13cm (41.6mm * pi = 13.11cm). Now, I lay my ruler down so that the zero
point is on the edge of the paper, and then rotate it until some number
divisible by 5 is just touching the line. OK, 15cm. Now I mark at 3,
6, 9, and 12cm. Then, wrap that paper around the BT-60 again, and
transfer those marks plus the edge and voila! Five evenly-spaced fins.
It may sound complicated, but it's pretty simple if you once _see_ it
done. This technique can be used to mark off any arbitrary length into
any arbitrary number of equal divisions. Its accuracy is limited only
by the accuracy of your ruler, and by your ability to mark the paper
precisely. There's no measuring so there's no rounding error.
--
Gordon S. Hlavenka www.crashelex.com nos...@crashelex.com
Grammar and spelling flames welcome.
Yes, that's really my email address. Don't change it.
Philip Doolittle
also means that I have to get my lazy butt up from my rocket studio (dining room
table). Go to Home Depot, Lowes, etc.. and get a 3' piece of 1/4" thick angle
aluminum (or steel if you prefer) for $1.99. Works great and can even be used to
line up the launch lugs you forgot to mark until AFTER the fins are on. For small
birds, Estes sells a fin marking tool (BT-70 and lower), an fin alignment tool
(24mm and lower), and a tube marking tool (1ft max length) that are really
fabulous. The tube marking tool has a slide stop, and a pencil hole for drawing
perfect rings around a tube at the precise length you desire. If anyone every
markets them for big stuff, I'll be the first in line.
Philip
bob fortune wrote:
> Shick68 wrote:
> >
> > Hello
> > I'm upscaling a Loc Lil Nuke. I need to mark a 4 inch body tube for a 3 fin
> > rocket. What is the best way to mark the bt for the 3 fins?
> > Thanks
> > Mike
>
> hey mike,
>
> i draw the circle and fin locations up on a computer program which has
> scalable rulers, print it out, set the bt on the paper then mark the bt but i
> don't know if you have this available to you.
>
> the only way i can think of is kinda clunky but it should get pretty close. if
> the bt is 4" in diameter the circumference would be pi times diameter or
> 3.1416 etc. times 4 or 12.5664. (you can check with a piece of paper by
> overlapping it on the tube, marking the paper and measuring on a ruler)
>
> divide this by three to get 4.188.
>
> take the piece of paper you measured the tube with and mark it at 0", 4.188"
> (the fraction is going to be a bit bigger that 1/8 maybe 3/16"), and 8.376".
> put the paper on the tube and transfer the points et voila'.
>
> i've found that for drawing the axial fin marking lines on a bt an aluminum
> sliding patio door has a nice fat straight edge, often straighter and taller
> than a door casing.
>
> another thing i've found is (this is for smaller diameter rockets that have a
> fin marking guide on the instructions) if i put removable scotch tape over the
> guide i can mark the tape, peel it off, stick it on the tube and transfer the
> marks. no fussing around with cutting the guide or taping the guide to the bt.
>
> are you going to fly this tomorrow? : ) have fun!
>
> bob fortune
--
---------------------------------------------------------
Philip Doolittle
pdoolittle...@mindspring.com
Note: Remove SPAMBLOCK from email address to reply.
SOAR #0074
---------------------------------------------------------
Mark B. Bundick
<nos...@crashelex.com> wrote:
>Shick68 wrote:
>> I need to mark a 4 inch body tube for a 3 fin
>> rocket. What is the best way to mark the bt for the 3 fins?
>
>Here's a nifty way to mark fin spacings on BTs:
>
>Wrap a piece of paper around the tube, and draw a line at the overlap
>point.
>
>Lay a ruler on the paper so that the zero mark rests on the edge of the
>paper, and aome number divisible by the number of fins is exactly on the
>overlap line. This will be a diagonal of some sort, but it doesn't have
>to go corner-to-corner.
For three or four fins, it's simpler than that. If you just take the
paper you wrapped around and fold it into thirds or fourth, then you
have the marking points all laid out without using a ruler or
computer.
============================================================================
Mark B. Bundick 1350 Lilac Lane !7015...@nospam.compuserve.com!
NAR President Carol Stream, IL 60188 http://www.nar.org
bob fortune
>
(snip of a clever solution)
>
> For three or four fins, it's simpler than that. If you just take the
> paper you wrapped around and fold it into thirds or fourth, then you
> have the marking points all laid out without using a ruler or
> computer.
hey mark,
yep, that is extremely easy, best i've heard. to me, what's fascinating about
rocketry is there are so many ways of "skinning the cat" the challenge is
often remembering the simplest way to skin it. : )
thanks
bob fortune
The Silent Observer
Well, unless you happen to be the cat... B)
--
WARNING!! This area has been designated an official DOPE FREE ZONE!!
If you're going to be a dope, please do it somewhere else!
Donald Qualls, aka The Silent Observer NAR # 70141-SR Insured
Rocket Pages http://members.aol.com/silntobsvr/launches.htm
Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.
Des Bromilow
menu. You simply give it the diameter of the tube, fin root length, and
fin thickness and it does the rest for you. Worst thing you'll face is
finding a printer that can print it fullsize for you.
Des Bromilow
QRA
Brisbane
OZ
Shick68 wrote:
>
> Hello
> I'm upscaling a Loc Lil Nuke. I need to mark a 4 inch body tube for a 3 fin
> rocket. What is the best way to mark the bt for the 3 fins?
> Thanks
> Mike