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Old Jul 20, 2011, 01:52 PM
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I think Phil use a custom teflon wedge , lucky him to have that
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Old Jul 20, 2011, 01:52 PM
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I cut the flaperons loose with just a single cut at the hinge line. For the spacer, I currently use some 1/32" thick teflon sheet material that Kevin Sharbonda gave me. I want a hinge gap a bit wider than 1/32" at the root end of the wing so I build up the thickness of the teflon sheet material a few staggered layers of thick packing tape. Imagine a 2" wide sheet of teflon, add a 12" long piece of thick packing tape to one end, then a 10" long piece of tape, etc. Now you have a sheet of material that is .050" thick at one and tapers down to .032". I then use a straight edge and a knife to cut small strips off that sheet that match the thickness of the foam core at the hinge line. For the Zone, this spacer strip ends up being about .175 x .050 at the root and about .032 x .032 at the tip.That is how small the hinge gap can be for a DLG wing and really shows why Drela's - hinge line prefacing method that involves using foam triangles at the hinge line - simplifies a bit when doing a smaller wing like a DLG wing. Drela's method was drawn up originally for a Supra wing where the hinge gaps would be somewhat larger and more closely resembling triangles.

The Drela prefacing method is attached below. This is where it all began for me. The system simplifies somewhat for DLG wings.
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Last edited by Phil Barnes; Jul 20, 2011 at 04:23 PM.
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Old Jul 20, 2011, 02:10 PM
Hey was that a Thermal ????
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.014 mylar is very close to 1/32" I wonder how that would work for this method...

I don't plan on dumping my tape hinges but this is still great info.

Paul
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Old Jul 20, 2011, 02:34 PM
G_T
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I used Mylar strips for bagging airfoiled balsa DLG tails some time ago. It works pretty well, but make sure you wax the Mylar well and don't buff it all off! I think the Mylar strips tend to curl up more than the Teflon ones.

Gerald
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Old Jul 20, 2011, 02:34 PM
Aurora Builder
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Phil,

Are you just overlapping a thin strip of cloth along the entire trailing edge of the wing for your face in that location?

Great info on the prefacing, I'm still not entirely convinced of its usefulness, like I mentioned the only wing I've done it on was a Zone v1.5 that had a root chord 0.5" shorter than anything else out there. I've gone to a carbon doubler on the aileron and I'm pretty sure this is more than stiff enough, although I may go back to glass for weight savings.
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Old Jul 20, 2011, 02:34 PM
Oleg Golovidov
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1/32 = 0.03125
which is 2.2 times more than 0.014
I think mylar will be too thin for wings
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Old Jul 20, 2011, 02:35 PM
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Forgot to mention: I think using 1/32" balsa sheet in place of the teflon would work about as well. Just put a layer of packing tape on both faces (as a mold release) and then build up the thickness on one end with thick packing tape if desired.

One other point: Rather than building up the thickness of the hinge line spacer at the root end, you can go with the constant thickness .032" thick spacer, but just sand a slight bevel on the root end of the core. That bevel really only needs to go out a few inches or maybe up to 12" long from the root, and it does not need to bevel off the entire thickness at the hinge line. Just knock off a tiny bit of foam to give few thousandths more clearance for up aileron travel.

Crude drawing attached showing what the root end of the foam core needs to look like to allow the use of just a .032" spacer when bagging:
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Old Jul 20, 2011, 02:40 PM
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Update ... we found some .040 teflon and it's a no brainer for prefacing gap material !
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Old Jul 20, 2011, 02:44 PM
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Quote:
Originally Posted by samc99us View Post
Phil,

Are you just overlapping a thin strip of cloth along the entire trailing edge of the wing for your face in that location?
Yeah. Just some 1.2oz or 1.6oz glass or even 0.75oz glass. That glass is only for the purpose of preventing hinge line delamination. The way it works: without prefacing, you are relying the bond between the wing skin and the foam to prevent delamination. That bond is not all that strong, but more importantly, the skin can easily peel away from the foam since the skin just ends at the hinge line. That is why you see hinge line delaminations whenever you abuse a solid foam core wing. By wrapping the aft edge of the wing (and the front edge of the flaperon) with any fabric material (light glass or Kevlar) you now have a bond between composite fabrics at the hinge line AND there is a continuous wrap of fabric around the core materials, so a peeling type of separation between the skin and foam cannot happen.
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Old Jul 20, 2011, 02:47 PM
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Yes, of course that is the purpose of facing. I thought you were taking about the very trailing edge of the flaperons, where the mylars come together again. Probably not very good.

Kevin, is the 0.040" teflon available on McMaster?
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Old Jul 20, 2011, 02:57 PM
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I don't put any extra fabric at the trailing edge of the wing, I just make sure that I run a lot of extra epoxy in that area when bagging. I think the addition of a strip of light glass or some other material would work as well but it is easier to just run a bead of epoxy on the mylar just before adding the wing cores and bagging. My methods were mostly all developed doing production work so I always tend to do stuff the fast way. It may be that using extra fabric at the trailing edge would work better (maybe lighter, maybe stronger?) but would be viewed as a big pain in the butt for a production guy, and so not done that way in that environment.
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Old Jul 20, 2011, 03:08 PM
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I agree with that, I've been doing the light epoxy bead and it works well enough.

Any tips on laying 0-90 carbon/kevlar on the LE? I had a big issue doing so with my current D-Box wing, basically the carbon bubbled in a number of areas and required heavy sanding post bagging. The 45-45 strips at the tip didn't have the same problem (and that's how I do all my glass LE's). I would switch to 45-45 but my plan is to put the D-box on the foam with 3M, aka, simply extend the LE strip by an inch on top and bottom. If I do 45-45 the back of the D-box will like have some waviness to it.

Thanks for all the help and sorry for the detour on questions from skins to facing to LE's.
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Old Jul 20, 2011, 03:37 PM
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Aren't dissapearing ink markers hard to find?? (sorry - couldn't resist )
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Old Jul 20, 2011, 08:15 PM
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Quote:
Originally Posted by samc99us View Post
kevin, is the 0.040" teflon available on mcmaster?
yes
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Old Jul 21, 2011, 11:11 AM
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Why not use 1/16" balsa and sand a taper with a long block? Might be quicker and easier than the packing tape method. Or if you have the right kind of balsa stripper maybe you can cut the taper in.
Quote:
Originally Posted by Phil Barnes View Post
Forgot to mention: I think using 1/32" balsa sheet in place of the teflon would work about as well. Just put a layer of packing tape on both faces (as a mold release) and then build up the thickness on one end with thick packing tape if desired.
snip
:
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