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Here is info from Poly Fibre's manual on : "How to Cover an Aircraft", Appendix E: Inspection of Old Fabric, pages 98,99.
TSO C-15d/AMS 3806C "This is for normal aircraft , Vne of 160 mph and over with a wing loading of 9 pounds per square foot and over.:... minimum breaking stength of 56 pounds...
TSO C-14b/AMS 3804C "This is for aircraft with a Vne of under 160 mph and a wing loading of under 9 pounds per square foot. "..."So 46 pounds is the minimum at annual time."
"A minimum of 56 pounds is the magic number at annual time for most fabric covered airplanes."
"Today, most inspectors use a Maule fabric tester to measure resistance to breaking. Done correctly, a Maule tester does not damage the fabric. Older Seyboth testers actually punched a hole in the fabric when used. Don't let a Seyboth near your airplane unless you are fond of patching."
"Interestingly, Maule or Seyboth testers are not recognized anywhere in writing by the FAA as accepted frabic tests. The only recognized tests are the pull tests prescribed in the two TSOs mentioned above."
"IAs regularly use Maule testers to help them determine fabric strength. The Maule tester is not the last word., because it is not an approved testing instrument. But most importantly, IAs use their good judgement in inspecting fabric."
Hope this helps in understanding the test process...
Good coverage with silver protects the fabric from UV deterioration.....and failure of strength requirements.
Harry
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