Are butt joints in balsa strong?

[FlyByMike]

Just was wondering if building a butt joint in balsa is a strong enough joint ? Does anyone do this ?

I am building a Guillows NeuportII to learn how to stick build (I don't expect this one to fly) and at one point I couldn't figure out how to join the upper wing spars (simple 3/16" square lengths) to make them long enough, so I just butt jointed them together with thin CA. Is this a bad thing to do if it was going to fly? It seems to have at least the same strength as the wood itself. (I realize the wood itself may need to be beefed up but that's a question for later.)

tia,

[Gerald]

A butt joint is the least strongest type joint. It may still be OK depending on the situation, but generally you should make a 'scarf' joint when joining the wing spars as in your situation. You cut each stick at an angle to increase the surface area of the joint like this ======/ /======. About a 30deg angle is best.

[FlyByMike]

I didn't do the scarf joint the plans called for 'cause the wood was too short given the angle they showed. 30 deg. might have worked OK tho. Or maybe I'm lazy and don't like making scarf joints.

Is that the Neuport's pilot in your atavar -he looks almost identical to mine -leathers and 'stache :D

[Viper Pilot]

I try to put a few strands of CF on each side of a butt joint. This seems to add some strength.
I also cut each end 45 degrees before gluing.

VP

[Gerald]

Originally posted by FlyByMike

Is that the Neuport's pilot in your atavar -he looks almost identical to mine -leathers and 'stache :D

He's the pilot from the SE5A kit. I'm pretty sure it's the same mold as the Neuport's. The facial features in the vacuum molded part are mostly indistinct, it's all in the paint :).

[Sparky Paul]

A butt-joint with added side supports; plywood or CF would be OK. But then again, even a scarfed joint should have that extra insurance.
.
If the wood in the kit (or whatever) is too short.. get a longer piece... outside the box..:)