Spar web scarf joint

[Shay King]

On Leonard’s plans, with the spar web butt joint, he reinforces it with an extra piece of 3/4 X 1/2 spruce.
Of those of you who’ve scarf jointed your spar webs, has anyone bothered to reinforce the joint?

[jrbirdman47]

Not me. The scarf joint is an inch and a half long, (12:1) and more than sufficiently strong on its own.

[Kamcoman77]

Not me, either. Like jrbirdman47 says, the scarf is about 1-1/2" long.

[Shay King]

Thanks for the replies guys.
I’ve just realised while looking at your scarfs that all the 1/8” ply that came in my ’kit’ from the US has only 3 plys. It’s stamped Aircraft Plywood, Spec-Mil-6070,Birch face. Do you think this is ok? I’ve scarfed it, but haven’t glued it onto the spar yet.

[Kamcoman77]

Lots of 1/8" aircraft plywood is 3-ply. Since it has fewer glue joints than mine, you have more wood. Might be stronger than mine. I certainly would not be afraid to use it.

[Shay King]

Phew! Thanks again.

[Chuck in Indiana]

Mine was 3 ply, too. Not to worry..

I thought I had a picture of the router jig I made to do it, but can't find it. (scratching head) I already gave away all the tooling I made, so you'll have to use your imagination.