My plane with me in it is under 500lbs. I has 26ft*5ft=130 sq ft wing area or 18,720 sq in.

I need strength of at least 500lbs / 18,720 sq in = .027 lbs/sq in. or 4lbs/sq ft.

74lbs/sq in for oracover /5 strength ratio = 14.8 lbs/sq in for shrink wrap. I should be good by a wide margin.

do the calculickulations make sense to you?

No, what you're calculating is wing loading. Fabric strength is generally measured in lbs / lineal inch, i.e. the breaking strength of a strip of fabric 1" wide. For standard aircraft covering fabric, the limit is 46 lbs/inch, which is 70% of the strength of new fabric. Using the 3000 psi strength in the link you posted, that would be 18#/inch, which is a

*lot* weaker than aircraft fabric. Then there is the elongation or "stretchiness" as proppastie mentioned... it might not actually fail, but it may stretch and balloon out under air loads, altering (possibly dangerously) the airfoil. For some very back of the envelope calculations, Dacron has 15-20% elongation at break (at it's 46#/in breaking strength) whereas the shrink wrap has a

*650%* elongation at its much lower 18#/in breaking strength. This means that polyester aircraft fabric is

**83 times** less stretchy than .006 shrink wrap. Put another way, if standard aircraft fabric balloons out, say, 1/8" in flight (a made up but not unreasonable guestimate), then the shrink wrap will balloon out

*ten inches* under the same load. Not very aerodynamic...

Dana