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Gullwing Doors - How to Build Them Update

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wsimpso1

Super Moderator
Staff member
Joined
Oct 18, 2003
Messages
12,181
Location
Saline Michigan
Ok, I have built my female mold for the doors and roof, laid out the edges of the door, built a rack under the mold to hold it for building the first door, and built my first test piece to make sure that I have my process together.

The design for the door will assure that the seals will stay loaded (less than 1/8" of lift dflection) to 6g at Va and Vne, have a factor of safety of 2.0 or more in all lamina, and support door hinges, latches, windows, gas spring struts to hold them open, etc. As it turned out, once the design met the deflection requirement, strength is a no brainer.

The cores are 1 1/2" wide and 1" thick in the front and rear bows and tapers to 5/8" thick in the top and bottom legs. Unidirectional glass tape makes up the caps and most of the weight, with Bidirection cloth and tapes making up the rest.

I had checked out carbon. The doors alone would have cost another $600 and I was going to get about a 6 pound weight save. Hardly worth it, and I would have to figure out how to ensure that everything was wet out and bonded together...

Making test parts has confirmed that this method will work:

First Layup is against the mold:
One dacron peel ply, one nylon perforated ply, one peel ply;
Two BID over the whole part as a skin;
Multiple plies of UNI tape as skin side spar caps on the jamb side -Pieced to 3.75" wide in the top and bottom legs, trimmed to 2" wide in the bows. The number of plies is greater on the forward part of the top and bottom legs, less on the bows;
Peel ply; perforated ply, peel ply, and three layers of batting;
Bag film.

Second Layup is merely attachment of the PVC foam cores and high density cores at places like the hinge and latch points:
Bond cores in place with thickened epoxy and vacuum bag. Support pieces are hot glued to the mold to keep the cores from moving;
Peel ply, perf ply, peel ply, batting, and bag film.

Third Layup is inner caps:
More UNI tapes forming the inner caps at 3.25" and 1.25" widths in upper/lower legs and bows respectively, with varying numbers of plies depending upon position;
Peel ply, perforated ply, peel ply, three layers of batting, and bag film.

Fourth and Last Layup:
Three plies BID over the entire thing to serve as shear web;
Peel ply, perforated ply, peel ply, batting, and bag film.

I have tried to do the inner caps and inner skin/shear web together, and it just does not work. Peel ply ends up trapped in the BID cloth and imbedded in excess epoxy. It works better when we do not try to take too big of a bite.

I am thinking of experimenting with hot gluing the cores in place and let resin migration and vacuum bagging move enough resin under to bond them inplace while the inner caps also cure, but it does not sound promising.

While I now have a plan, I have yet to build one, although I am setting up for one next week.

Does anyone see a fatal flaw before I actually try to build this? Any other comments?
 
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