Martin Morgan wrote in message . com.au...
frank wrote:
Wouldn't the spruce fillers act as a lamination on the spar caps?

Yes but only where they are attached. Since "between the ribs" was
mentioned I'd say there was no benefit.

However, if the plywood skin is handling any loads eg. torque loads,
then the balsa may be a problem!!

Balsa is used in the Knight Twister (cantilever biplane). It has a
plywood torque box (probably a better term here), and uses the balsa to
fill in the leading edge and tips.

So yes, balsa (or foam) can be used in some places for lighter
structures. But I'd be wary of using it where it attaches two stronger
materials..

Regards

Yes, part of it calls for in between the ribs on the spars for a
filler. That is the front and back of the main spar and across the
rear spar as a filler. Also on the trailing edge of the flaps,
ailerons, and elevator control, (lets see if I can explain this) where
the trailing edge meets the structural pieces. On top of these areas
plywood will be glued, and then Dacron. At the part where the trailing
edge meets the structural pieces, it calls for a 45 deg. filler to
help round out the plywood. Now, have I confused everyone, or just
a few?
Lou
Martin Morgan