Steven Pearson <<Steve>>
writes:

I am always interested in anything that could improve sail life so
I asked Polyant to test AP 303 shortly after it was introduced more than 20
years ago.

1. There have been many claims that it can restore the structural properties of
the fabric and, believe it or not, this is widely accepted by pilots because the
fabric looks better after you apply it. Obviously not true.

2. The Polyant testing showed a significant deterioration of the fabric bias
strength and a corresponding increase in tear strength. Unfinished sailcloth is
not unlike polyester fabric that you might purchase at a craft store and you
might imagine what a sail made from that would fly like. All you have to do is
look at the difference in twist and loss of performance comparing an older woven
glider with a new one. That's what you are doing to your sail when you apply
AP303. Incidentally, the principle structural advantage of polyester laminates
over woven fabrics is improved bias strength.

3. I can't speak to the effectiveness of the UV inhibitors but I'm skeptical and
you'd need a long term test to evaluate that. As I recall, we did UV testing and
it didn't show any improvement but that was a long time ago and I could be
wrong. I'd be happy to send samples to Polyant for testing. I think you'd want 3
pieces, about a sq m each, from the same roll. One would be the untreated
reference, one would be treated several times but not exposed to UV, and the
last would be treated and exposed for at least 6 months in strong UV.

4. My recommendation is simply to break your glider down or shelter it right
after flying. Protective covers are very helpful but most are not completely
effective at blocking UV.