jp1961

I'm scratch building a 60" wingspan profile model that will have a 25cc gas engine. The wings will be foam core. I'm using a 1.25" diameter aluminum tube to join the wings. How long would you make it? I have a 20" long tube, but I'm not sure if that's long enough.

Jeff

sensei

If you have upper and lower spar caps and the tube is centered between them, there is no reason that won't work great for you, just make sure to bond tie it all together.

Bob

speedracerntrixie

My Feedback: (29)

I agree with Bob. I think that most manufacturers are running the tube into the wing too far. I have 2 airplanes that I scratch built with wing tubes. The first one is a 2M pattern airplane ( 11 lbs ) that uses a 7/8" CF tube that goes 8" into the wing. The second airplane is a 33% Laser that used a 1 1/2" CF tube that goes 11" into the wing. Whatever sleeve you use in the wing should be anchored at the root rib and a peice of ply at the other end that extends vertically to tie into the sheeting. For spar caps I use some 3K CF tow that extends at least 8" past the wing tube. This helps to avoid a stress riser.

jp1961

I wasn't plannning on using spar caps (not sure I know what those are), just foam, with a pine veneer covering. I did make a fiberglass tube for the sleeve.

Jeff

PatternPilot

My Feedback: (58)

The way we make our plug in wings is with a false rib at the end of the tube sleeve in the wing and then at the root of the foam we have a lite ply rib.... then we run a .75 inch wide by .007 thick carbon fiber tape from root to tip over the tube area.

see attached... sorry the drawing was quick.

sensei

If you are not going to run spar caps then do as pattern pilot illustrated, that works good as well.

Note: Do not just run the tube out into the foam alone and then sheet!

Bob