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jj94

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How do you properly set your fins so they are spaced apart equally with LOC and PML tubes? I know that most kits come with wraps and Estes came out with the fin guides, but I don't know how to do it with tubes intended for mid power.
 
a calibrated eyeball, and an engineering square, and a plumb bob.

Your mileage may vary.
 
Ooh, the Starter Kit looks nice to me, with the 24 and 29mm center posts. Although I really, really, really want the Starter Kit, is there any cheaper way to do it with some stuff readily available at a hardware store like Lowes?
 
Can't you just measure the tube and divide by the number of fins?
 
Originally posted by jj94
How do you properly set your fins so they are spaced apart equally with LOC and PML tubes? I know that most kits come with wraps and Estes came out with the fin guides, but I don't know how to do it with tubes intended for mid power.
LOW TECH 4-FIN METHOD
  • Wrap any body tube with a rectangular piece of paper, tape to itself snugly making sure top and bottom edges line up
  • Remove paper sleeve you've created
  • Press paper sleeve flat on table
  • Reopen sleeve
  • Roll the sleeve so the two creases you've created line up together
  • Press paper flat on table again
  • Reopen sleeve and put on body tube again.
This results in a creased sleeve with perfect measurements for 4 fins on any tube,

I have a trick for converting that to a 3 fin, too.

LOW TECH 3-FIN METHOD
  • Number the creases in the 4-FIN sleeve created above in order from 1 through 4
  • Carefully bend crease 2 onto crease 3 and press paper flat
  • The crease you just created is crease 2A
  • Carefully bend crease 3 onto crease 4 and press paper flat
  • The crease you just created is crease 3A

Now, this sleeve has markings for 3 and 4 fins. For 3-fin birds, use creases 1, 2A and 3A.

Jerry
 
Thanks guys. I never thought of creasing paper like that. That'll come in handy pretty often now. Thanks again.
 
Well, the Kaplow clips are named after their designer. I created my Fin Marking method on the fly, so anyone have any complaints about naming it the:

Beaucaire Folding Fin Technique ??

Hehe, (bows to the masses)
 
Originally posted by jj94
How do you properly set your fins so they are spaced apart equally with LOC and PML tubes? I know that most kits come with wraps and Estes came out with the fin guides, but I don't know how to do it with tubes intended for mid power.
Getting the fin placement points on the body tube is the easy part -- getting the fins perpendicular to the body tube at that location is the hard part.

Many have pointed out good solutions -- the easiest is cutting a wrap of paper that goes around the tube, marking where it overlaps and cut it off. Four fins: fold in half twice. Three fins: fold it in even thirds. Mark on the creases.

Now that you have your tube marked where the fins go, how do we get the fins on at the right angles?

The best thing to do is get a sheet of cardboard about 18" square. Using a compass and a protractor, lay out a circle in the center of the square that is about 1/4" larger in diameter than your body tube. From the center point, using the protractor, lay out the fins angles: three fins - 120 degrees, four fins - 90 degrees. Draw a line from the center point up each of the fin angles, then cut a slot along that line the width of your fins. Cut out the center circle and you now have a fin jig.

finjig.gif


Trim the corners where the fin jig comes in contact with the fin fillet area. Slip the fin jig on the body tube, apply epoxy to the fin root edge, taking care not to get it on the jig. Slip it in place, align it and set it so that fin is pointing up until the epoxy sets. If you laid out your fin jig like the illustration, it will rest on the bottom edge with the fin you are working on pointing straight up. Once the fin sets, then attach the other fins one at the time, placing the current fin pointing upward. The jig will hold them at the right angle until they set, then you fillet the fin joints.
 
Originally posted by JBeau
I have a trick for converting that to a 3 fin, too.

LOW TECH 3-FIN METHOD
  • Number the creases in the 4-FIN sleeve created above in order from 1 through 4
  • Carefully bend crease 2 onto crease 3 and press paper flat
  • The crease you just created is crease 2A
  • Carefully bend crease 3 onto crease 4 and press paper flat
  • The crease you just created is crease 3A

Now, this sleeve has markings for 3 and 4 fins. For 3-fin birds, use creases 1, 2A and 3A.

Jerry
I don't believe that's correct. What you end up with is crease 2A at 135 degrees around from crease 1, not the desired 120 degrees. Similarly, crease 3A ends up 225 degrees around in the same direction, not at 240 degrees. Creases 2A and 3A end up 90 degrees apart, while crease 1 ends up 135 degrees from each of the other two.

Putting it another way, if crease 1 is at North (0 degrees), and crease 2 is East, then 2A ends up halfway between 2 (East) and 3 (South), or Southeast (135 degrees). Crease 3a ends up Southwest (225 degrees). You actually want 0, 120, and 240.
 
Originally posted by TWRackers
I don't believe that's correct. What you end up with is crease 2A at 135 degrees around from crease 1, not the desired 120 degrees. Similarly, crease 3A ends up 225 degrees around in the same direction, not at 240 degrees. Creases 2A and 3A end up 90 degrees apart, while crease 1 ends up 135 degrees from each of the other two.

Putting it another way, if crease 1 is at North (0 degrees), and crease 2 is East, then 2A ends up halfway between 2 (East) and 3 (South), or Southeast (135 degrees). Crease 3a ends up Southwest (225 degrees). You actually want 0, 120, and 240.

That's exactly what I found when I tried that method...More of an airplane tail than a rocket...
 
Originally posted by TWRackers
I don't believe that's correct. What you end up with is crease 2A at 135 degrees around from crease 1, not the desired 120 degrees. Similarly, crease 3A ends up 225 degrees around in the same direction, not at 240 degrees. Creases 2A and 3A end up 90 degrees apart, while crease 1 ends up 135 degrees from each of the other two.
(pout) I know, I'd already discovered my miscalculation and was working (not fervently) on another quick method, hoped to have it worked out and posted before anyone noticed. Nice catch.

So far, the only quick method I've come up with so far involves unfurling the sleeve, something I'd really like to avoid.
  • Wrap paper around BT and mark where the overlap occurs
  • Remove sleeve and cut paper at mark
  • Fold the sleeve lengthwise into thirds, letter style (this may take a couple of tries to get the thirds exact, but doable)
  • Unfold and mark the crease edges to verify the points
  • Place sleeve back on rocket and mark BT at points
I'd like a method that involves wrapping the BT, taping the sleeve, then removing it and doing some magic resulting in folds in the right place.

Jerry

EDIT: Now, this is really just fun for scratch building, because the Estes Fin Marking Guide (yellow tube stand) marks BTs perfectly in all basic tube sizes, so...
 
Am I the only one still using VCP? It has a fin alignment guide tool that creates a template and then prints it. You glue it to a piece of cardboard and then cut it out. You can specify every dimension - BT diameter, fin span and fin thickness.
 
Originally posted by BARX2
Am I the only one still using VCP? It has a fin alignment guide tool that creates a template and then prints it. You glue it to a piece of cardboard and then cut it out. You can specify every dimension - BT diameter, fin span and fin thickness.

Nope, I've been a happy VCP user since '03. VCP was instrumental in building my upscale Commanche-3 last year. A very useful piece of software for scratch building!

I see BobH48 is a VCP user as well. :)
 
I'll make it real easy and for different size tubes

BSD Fin Guide

print it, save it, I have mine under Glass to keep it pretty

try it you'll like it!!

:)
 
Thanks for the guide...Now I have at least 2 sets of fins to re-do!:(
 
I'll just stick with some of the methods here. I'm not sure about the bmiBay jig anymore. It seems easier (and cheaper) to use VCP or some other technique. Thanks.
 
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