Armour-all on Dacron?

[Guest Baphomet]

Fabric info: In the interests of safety and general knowledge, I'll make the following observations.

 

1. I have at every pre-flight performed a 'test' of the fabic, demonstrated to me by my instructor. The 4-finger test involves applying pressure to the top surface of the fabric adjacent to a rib, and is a pass/fail test i.e if the fabric tears don't fly. I'm sure everyone who has a fabric aircraft uses it. I recently purchased a 'bettsometer' fabric tester, and after a morning flight performed a test according to the instructions that came with it. The fabric failed the test at just over 1/2 the recommended minimum figure. Alarmed by this I then performed the test again on another section of 'exposed' fabric, and got the same result. I then tested a piece of fabric that had been in 'shadow' its entire life, and it passed the test easily.

 

Conclusions: The four finger test is at best only a guide, and at worst dangerous. I'm not sure what safety margin is built into the fabric test pass/fail figure, and I presume it allows for the 'usually' +4 -2 'G' structural integrity rating on these types of aircraft, but it is probably a good idea to get the fabric tested before you perform steep turns, pull-ups etc.

 

Re fabric treatment, there is a product sold by Aviaquip called "Aerothane" made specifically for the protection of Dacron from UV. It is a two-pac product that is sprayed on. The only down side is price, $400+ for a thruster type.

 

Hope some of this helps.

 

 

[jordy]

Many thanks Nick, you've given me hope