Picked up a Great Planes Super Stearman kit that was partially built. In the kit as designed it had three pieces of 1/8 plywood glued together to make a 3/8's joiner. The kit was missing the ones for the top wing which are straight so it makes it easy to reproduce. Question is would the three 1/8 pieces glued as called for be stronger or would one 7 ply 3/8 piece work just as well? I have material to go either way just wanted to get some other opinions.

Thanks!

I suspect 3 pieces will be stronger. Who knows what the inside ply’s are made of or how they are glued together.

The single piece of seven ply is stronger plywood is laminated in a press
The kit uses three pieces to reduce cost

Use the plywood for the outer pieces and some 1/8th aluminum for the inner. Use JB Weld to glue them all together.


No more issues concerning strength.

Using epoxy on three pieces of ply would be a little bit stronger.

I might suggest, since you have the material... make a few spars, using each technique, and put them to the test and see which one is stronger.

Honestly, I would think either one would suffice for the plane... but since the question came up, give the test a try.

Originally Posted by boothg-3

The single piece of seven ply is stronger plywood is laminated in a press
The kit uses three pieces to reduce cost

+1


A lot of the matial selection, laminations etc are to use cheaper materials and make it easier to ship the kit.




If you use 3/8 ply - make sure its real aircraft ply, not the light stuff.

Thanks guys. Lot's of good ideas here. Material I have is Birch , 7 ply for the 3/8 and 5 ply for the 1/8, aircraft grade plywood from Balsa USA so it should be the good stuff. I cut out the 3 pieces last night and got them epoxied together. Maybe tonight I'll try the 3/8 and go from there. Had not thought about the 1/8 aluminum sandwiched between to pieces of ply!

Originally Posted by Fly4funn

Thanks guys. Lot's of good ideas here. Material I have is Birch , 7 ply for the 3/8 and 5 ply for the 1/8, aircraft grade plywood from Balsa USA so it should be the good stuff. I cut out the 3 pieces last night and got them epoxied together. Maybe tonight I'll try the 3/8 and go from there. Had not thought about the 1/8 aluminum sandwiched between to pieces of ply!

Anything you’re suggesting to use will probably be far better than what came with the kit. 👍