I am reasonably well versed in analyzing wood and Aluminum aircraft structures. I have decided to try my hand at composite analysis now. The math is fine as I have advanced degrees in (non aero) engineering. However I would like to validate my approach with folks that have actually analyzed composite structures. As a start I am analyzing a fuselage structure. I realize that minimum gauge rules but I would like to calculate and get a feel for the margins involved. I am considering a 0.5inch core (styrofoam 2lbs) with 2 and 3 layers of rutan uni and bid. I am using flat plate theory to calculate maximum loads. Then I am checking buckling of the sandwich panels- for this I assume the sides top and bottom are simply supported on the corners. Finally I check for wrinkling. in general I have found buckling to be critical. I am assuming the width of the panels to be 36inches and no intermediate bulkheads between tail and wing attach (is this typical?), i.e. long panels. Assuming a layup of (0uni;45bid;0.5"foam;-45bid;0Uni) of rutan fabric and 2lbs/ft^3 styrofoam [TD="width: 73"]D11[/TD] [TD="class: xl66, width: 83, align: right"]8,427.15[/TD] [TD="width: 73"][/TD] [TD="width: 73"]Ec[/TD] [TD="class: xl66, width: 73, align: right"]1,500.00[/TD] D22 [TD="class: xl66, align: right"]3,606.83[/TD] Es [TD="class: xl66, align: right"]1,000.00[/TD] D12 [TD="class: xl66, align: right"]1,651.11[/TD] t [TD="class: xl66, align: right"]0.54[/TD] D66 [TD="class: xl66, align: right"]1,990.12[/TD] tf [TD="class: xl66, align: right"]0.04[/TD] I get the following results: N max -1100 lbs per inch (ultimate compression) N wrk 359.1226411 lbs per inch (Wrinkling) N bkl 169.741159 lbs per inch (Buckling) Hence buckling is critical and I can take at most 359lbs/inch in compression before the top buckles. Is this in line with expectation? In my old case I have a 1000lbs load on the stabilizer and a 10 ft tail lever arm. This results in about ~100lbs per inch of compression load on the top panel so I have significant (~70%)margin. Reasonable? I know this is a little technical but any comments are appreciated.