In article .com, Monty Graves
says...


Chuck Slusarczyk CSG HAWK uses 2.25 inch front spar, and so does the
Rans S-4. Both high wing single place planes..... Chuck S. can
verifiy his own max gross on those 2.25 inch spars, and how that was
derived..... Both planes use max Rotax 503 engines weights some 60 lbs
lighter than the direct drive VW.


That's correct,our Single seat Hawk has 2 1/4" dia spars and our 2 seaters have
a 3" dia spar. Back when the original was designed we first designed the wing
and sized the spars based on a plus 6 g ultimate load factor.We then
substantiated the designed wing with actual load tests.We used a lift
distribution for a rectangular wing to determine the loads spanwise .Then since
it was a 2 spar wing the load was divided chordwise at 70% on the front spar and
30% on the rear spar. After the sandbag tests we found we were within about 3%
of the designed load.

In my humble opinion the reason we don't see many wing failures with wings that
I consider under designed. Is the fact that the light wing loading and inability
of these planes to maintain energy prevents them from pulling more then about 3
g's before they stall. But that's just my opinion I don't want to start a "spar
wars" episode :-)

See ya

Chuck S