HumanPoweredDesigner
Well-Known Member
I want glue together two highly loaded wood pieces to make a longer piece. I read that scarfing is the way to do it, but I don't want to sand the angle just right, risk damaging the wood with the sander, or get dust in my face.
Is there an equally strong alternative to scarfing for airplane spars? I don't mind a small weight penalty as long as it is easy to build.
I was thinking of putting the two short pieces together end to end, and then then gluing much shorter over lapping pieces on to each side of them, kind of like a mini fish joint or gusset but in one dimension. I'd use the same kind of wood, same grain orientation, with at least the same total width as the spar, and the "gussets" would be at least 15 times as long as they are thick. Would this be at least as strong and safe as scarfing? My intuition says yes, but I wonder if there is some way the joint can peel horizontally or shear vertically, differently than a solid piece would.
Edit:
I suspect the main difference would be tensile strength in the bottom of the spar. I might need 30:1 instead of 15:1, depending on the shear strength and tensile strength of the wood.
Is there an equally strong alternative to scarfing for airplane spars? I don't mind a small weight penalty as long as it is easy to build.
I was thinking of putting the two short pieces together end to end, and then then gluing much shorter over lapping pieces on to each side of them, kind of like a mini fish joint or gusset but in one dimension. I'd use the same kind of wood, same grain orientation, with at least the same total width as the spar, and the "gussets" would be at least 15 times as long as they are thick. Would this be at least as strong and safe as scarfing? My intuition says yes, but I wonder if there is some way the joint can peel horizontally or shear vertically, differently than a solid piece would.
Edit:
I suspect the main difference would be tensile strength in the bottom of the spar. I might need 30:1 instead of 15:1, depending on the shear strength and tensile strength of the wood.
