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Old Jan 25, 2002, 12:51 PM
psbowen is offline
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Cutting tapered foam wings?


I'm building a F-111 for dual EDF50's, and I need to cut tapered foam wings. How do you folks keep the taper nice and straight using a hot wire? I've tried a couple of times, and I keep getting sagging leading edges. I get the root way out of sync with the tiny wing tips.

Thanks All,
Sean
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Old Jan 25, 2002, 01:23 PM
CenTexFlyer is offline
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Hope you work it out Sean, I would like to see what you end up with when you're done. I was with the 48th TAC Fighter Wing, RAF Lakenheath in the 70's so I've seen the subject up close and personal
Old Jan 25, 2002, 02:43 PM
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For what it's worth...


I actually have never cut a foam wing, so what do I know, but I did have an idea....

Why don't you cut wing sections, rather than trying to cut half a wing at one cutting? Say divide each wing half into 2 or 3 segments, and then join them later with glue, and use a root to tip spar for spanwise strength.

That makes it easier for you since there's less disparity between the chord/airfoil at the root and the tip of each section.

Not sure if this is practical or not. I have noticed that some kits with bizarre wings tend to cut them that way.

-ZagiZagi
Old Jan 25, 2002, 02:56 PM
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The one link that had it all for me was ;

http://www.scalecombat.com/sections/...techniques.htm

Thanx again Kit basher for that one

Good luck
Old Jan 25, 2002, 04:45 PM
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wings.


Cutting tapered wings is tough because the wire moves more slowly at the tip, so the foam tends to melt away faster there. Some tips that help for me are:

Cut from the leading edge back to the trailing edge. The leading edge is the tougher part to cut because generally the angle of the templane is sharper there. Also, the wire will "lag" (bows) in the foam somewhat and it seems the farther into the cut, the more the wire lags. If you cut the leading edge first, the wire will be straighter while cutting the more curved part of the wing. Wire lag won't distort the wing as much on the straighter part of the airfoil from the "spar" location back. I think your "sag" is coming from the lag in the wire.

Your templates have to have a lead in area on both the front and the back, to support the wire at the start of the cut and when cutting through the trailing edge.

I also find a fixture is easy to make up of a ply base to hold your templates (since your making templates anyways) and makes for cutting great looking wings.

Here is a picture of a fixture for foam wings for my Giles G202. Its a flat bottom so no need to cut the flat side. Note the lead in /out on the template. I have made fixtures for symetrical and semi symetrical wings too. If you want to know how, let me know and I'll fill you in on it. Its easy too.
Old May 08, 2002, 10:20 PM
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For semisymetrical, split the profile, add for foam thickness and make the templates. Attach them to a ply base, put in the foam block, cut the top, put the foam block, with the scrap from the first cut into the template for the bottom, and cut the bottom. Here is a picture of a jig to cut a wing for my BAT airplane. It uses one ply base for both the top and bottom cut. I cut one side, flip the template, stick the foam back in and cut the other side.

Its more work then just making the templates and sticking them to the foam block, but I have had better luck this way. I find the templates move from the pressure of the bow when they are double sided taped, glued etc. This way, nothing moves. I make many wings for the BAT, so the extra time on the templates is worth it.

BTW, you need to make a left and right if the wing has taper.
Last edited by balsaman; May 08, 2002 at 10:22 PM.
Old May 08, 2002, 10:59 PM
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template


here is a drawing for the template I use
Last edited by balsaman; May 09, 2002 at 08:08 AM.
Old May 09, 2002, 05:35 AM
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If you keep getting bad (tapered)wings, make markings from 1 to 10 on tip an root template. Call a friend an do cut each one end.
Works !
Old May 09, 2002, 06:12 AM
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Hi


Can somone tell me how to get aerofoils for ZAGI/RAZOR/JAZZ or other flying wing planes, as i wouild like to make a mini one???

Are there any programs that i could use to make them???

Please Help me

Josh L
Old May 09, 2002, 08:33 AM
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Josh,

Do a search for a program called "Profili". Its an Italian program but it does have english menus. It also comes with hundreds of profiles .... including some Zagi-like ones as well.
Old May 09, 2002, 11:41 AM
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I have found that using a longer bow and setting up a dead point to pivot from works well. The dead point is the spot that the LE taper and TE taper lines meet out from the wing tip. Even if its just close it seems to make a big difference in the quality of the core. I made jigs out of particle board. the board was cut to the planform shape and then screwed down to a larger piece of board. Then made some round cam locks with the hole drilled off center. then you place your template at each edge, rotate the camlocks up tight and you are ready to cut. on some of the later jigs we built in the dead point so there was less work involved on the next core to be cut. The pivot could be as simple as a wood block with a hole drilled into it. put your tip end of the bow and pull from there in a sweeping motion through your templates. Its easier than it sounds.

Regards
Bill
Old May 09, 2002, 07:36 PM
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Cutting tapers


After all the years of cutting foam I found it is best to start on the LE and come out the TE. The wire will lag and the TE has less of a contour. If you do a hands on cut, two people one on each side works good. If you go with the hands off way go with a Feather Cutter.


www.mmglidertech.com
Old May 09, 2002, 10:33 PM
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If your getting sagging, the wire Isn't tight enough, not hot enough, or going to fast. Tocut tapered wings, cut block to root and tip lengths. With fine tipped magic marker. With ruler find centre of root chord and mark. From this mark to leading edge find halfway mark again. Do the same to trailing edge. Keep splitting the lines till they're about1/2 in apart. Starting at LE, number the lines 1,2,3,4 etc to TE. do the same at the tip with the same number of lines. Tip should end up about1/4 in apart.I do this by myself Just keep the numbers lined up as you go along. Been doing it this way for last 40 yrs. At the speed wire goes, I'ts not hard to follow. Try it on scrap first.


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