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Oct 26, 2020, 10:47 PM
Entropy is happening!
Jim.Thompson's Avatar
Quote:
Originally Posted by cityevader
....................................
Then again, my interests are heavy slopers, so my perspective is likely biased...................
Then I suggest you use my wood insert method.
(I think I described it above).
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Oct 26, 2020, 11:22 PM
IT'S NOSE HEAVY!!!!
cityevader's Avatar
I've done that before, but it is fiddly as you said. I like the concept of a foam wedge but am confident i cannot cut a perfect one.
Oct 27, 2020, 12:57 AM
Entropy is happening!
Jim.Thompson's Avatar
Quote:
Originally Posted by cityevader
I've done that before, but it is fiddly as you said. I like the concept of a foam wedge but am confident i cannot cut a perfect one.
Ok.
Then you are stuck deliberating between the two...........until you decide on an alternative.
Keep us posted on what you come up with.
Oct 27, 2020, 08:50 AM
Barney Fife, Vigilante
tom43004's Avatar
I think the key to making sure your hingeline is solid is to keep the support structure for the hinge material as close to the mechanical hinge pivot as possible.

I'm not sure how to calculate the stresses exactly because I don't know the loads / speeds involved, but I would say that if they're THAT extreme, you may want to consider making the wing and control surface separately, then hinging with silicone.
Oct 27, 2020, 11:58 AM
Everything is broken
JimZinVT's Avatar
I've tried both Jim's and Tom's way. Both are fiddly in their own way. Fitting the wood strip accurately is a challenge. Joe Mach1 details his method for this on one of his recent build threads. With Tom's way I struggle to get the little strips of facing fiberglass positioned right, the foam strip back in place, then wet out and bagged without things sliding out of position. That was with the 3m77 mist method; I'll have to try it with transfer tape. The cutting of the hinge line actually is not too hard Chad....you don't actually 'cut' the triangle out. The foam strip is rectangular. You make a vertical slice through the center of the foam strip down to the kevlar, fold open the hinge, then use a sanding block to create the bevel.

I have some worry about the skin/hinge pulling away from what's left of the foam strip on a slope plane that lives a rough life. Typical slopers have a thicker wing than a DLG so the strip/bevel needs to be wider. In that situation it seems like actually cutting a triangle (so the facing comes right to the hinge line) would be stronger. And like Chad says, cutting that triangle accurately can be a challenge.
But I usually wreck them long before weak hinge design becomes an issue
Oct 27, 2020, 01:13 PM
IT'S NOSE HEAVY!!!!
cityevader's Avatar
I saw an older dlg thread where a triangle was cut out, versus Tom's rectangular strip.
I like the idea of Tom's way better for construction ease.
If worried too much, i guess a carbon doubler could be added over the hinge line.
Oct 27, 2020, 04:10 PM
Entropy is happening!
Jim.Thompson's Avatar

Silicone hinges.


Quote:
Originally Posted by tom43004
..................... then hinging with silicone.
I have also used silicone hinges very successfully on foam, built up and composite wings.
In this case...........EPP tape covered...............I have built in a timber (Pauwlonia.......but what ever you have) drag spar and control surface LE spar. Tape up, cover, then last of all run the silicone hinge.
I have an instructional video on silicone hinges somewhere. If you want, I will find it.

Silicone hinges are good!

Jim.


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