I've just finished cutting cores for a couple of sailplane
wings. I need to know what type & size spar I need for a
2m wing, and exactly how to join the wings on the Std. Class
wing.
I've constructed plenty of built-up wings, but the spar (or
joiner tube) was always attached to the d-tube spars, which
provide a smooth transition of stress from the joiner spar
or rod to the rest of the wing. I don't plan to use a full
span rigid spar on either wing.
 I need to know:
     A. On the 2M, (wing halves permanantly joined), how long
        should I make the spar, and of what size & type material?
     B. On the Std. Class wing, (two piece), I plan to insert
        a ply "capture box" to hold the joiner tube. It seems
        like the joiner rod & tube wouldn't extend far enough
        spanwise to be a strong enough spar. I plan to reinforce
        the wing with either carbon fiber or fiberglass strands,
        but I'm concerned about stress in the area at the end
        of the tip of the joiner rod. Can any of you share some
        info about this?
BTW, neither plane will be winch launched, and both will be sheeted
with balsa & heat shrink covering.
Thanks,
Bruce
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