sig lt-40 wing joining
 

Hi, I'm building my first kit, an LT-40, and will be coming up on joining the wings soon. I've read that some people use epoxy instead of thin CA for added strength. Has anyone done here done this? If so, how? Is epoxy thin enough to use the same procedure that is in the manual or would i have to do things differently? I figure if its too thick, I would have to epoxy the MADBs to the main spars on one wing, let it sit, then epoxy the MADBs and the gap on the other side all at once instead of two separate steps like in the manual. Does this make sense?


Thanks,
Rob

RE: sig lt-40 wing joining
 

You'll find that 99% of kit's and ARF's have their wing joined with Epoxy, why the SIG recommends thin CA I don't understand.
Epoxy is stronger, but most importantly, more flexible and will make the joint stronger.
Use 30-minute epoxy, not the 5-minute version, this gives you plenty of time to adjust the wing and tape it together before the glue cures.

Dry fit all pieces and make a "plan" in your head how you gonna join the wing, practise the steps a few times so you're sure everything fits good before gluing.

I'd recommend you finish both wing halves, then you try fit the wing joiner and slide both halves together, make sure there' s no gaps and everything looks ok.
Then smear epoxy in the holes where the joiner goes in both wing halves, brush generously epoxy on the wing joiner itself and finally join the wing halves to the joiner, making sure it's straight and tight.
Tape together and leave for a few hours to dry.

On more aerobatic, high stress models you can strenghten this joint further by wrapping the center section of the wing with fiberglass and "glass" it with thinned epoxy. Not needed on a trainer though IMHO.


/T5

RE: sig lt-40 wing joining
 

Use epoxy, not CA! Use 30 minute as suggested and leave it overnight to setup properly. I place a small weight on the left side of the wing to hold it flat against my freezer(put wax paper down on the freezer first) and make a small piece of balsa to hold the right side of the wing up to get the correct dihedral. In the morning turn the wing over. You will see a gap or 2 from the dihedral angle. Make another batch and fill this up with epoxy. then you will have a solid wing. :D

RE: sig lt-40 wing joining
 

Thanks to everyone. I was out of town for a few days and decided not to start anything more until I got back. I did a bunch of sanding and dry runs. I then tried out the epoxy on scrap balsa to see what i was working with and tonight, I applied the epoxy and joined my wings. I'm going to let them dry until tomorrow. Thanks, here is a picture of the wing halves, not glued together yet.

Rob

RE: sig lt-40 wing joining
 

Looks good!

RE: sig lt-40 wing joining
 

IMHO.... put the CA away... use it on your foamies and for a repair at the field.... I refuse to use it while building.....
to brittle....I think....

but I don't claim to be an expert builder....