fiberglass deterioration

[Reb Wallace]

does anyone know how to test glass for UV deterioration. I have just acquired a Q2 that has been out in the AZ. sun for about 6 years, where the paint has flaked off you can see the fiberglass, which has turned brown. Most of it is cosmetic, but was wanting to know if the spar can be tested to a point before failure, to know if it is structurally safe. any info would help thanks Rebel.

[AaronT]

I would like to know as well.   I have a line on a Lancair 360 kit that is 15 years old -- it still isn't started and has been garage kept in here in the Pacific NW.

Is there a shelf life on unprotected fiberglass?

[Rick Hall]

I'm gonna step out on a limb here...
I live at 7400', lots of sun, little air, lots of UV rays. Fiberglass (epoxy or polyester) has no real shelf life when exposed to the sun/weather. You may notice a bit of 'dusting' of the surface gloss though... Scotch-Brite and elbow grease is one solution.

The foams we use in building are not UV proof. Divinicell (H-45, H-100, ...) and Urethane (that real soft stuff) will degrade. Polystyrene (extruded, blue) will too, but takes a bit longer. Unprotected clear fiberglass will not stop it.

A brown epoxy may very well be Aero-Poxy, which cures with a brownish tinge

If me, I'd try to do a destructive test on a section of a foam/glass layup. Check peel, check to see if the foam has gone to dust. Especially if stored outside with no UV protection (final finish primer and paint)

My $.02, YMMV

Rick

[Reb Wallace]

Thanks Rick for info I have done some load test on the wings by putting double gross weight in the AC and had no failure, so looks like I may have a keeper.

[LongEZDaveA]

Reb,

You have me curious.  Are you saying that you supported the plane by the wings somehow and then loaded weights into the fuse?

It's very hard to do a proper static load test unless you understand the lift distribution on the wings.  One of the things you could do would be to look at the pictures in the Canard Pusher newsletters of how weights were distributed on the wings in Burt's static load tests in the early days.  Burt discouraged doing a static load test.  He did offer help on doing them properly to those building in other countries where the test was required.

If you're saying that you have left the plane on the gear and then added weight to the fuse, that would be hard to evaluate.  I won't eleborate until you care to give further details of your test.

If I only had confidence that my airframe was good for 2 Gs, I'd never fly.  I'm not saying this to be critical, I'm trying to help and I may have totally misunderstood your post.

My understanding of the way that fiberglass deteriorates is that the epoxy sublimates and leaves the 'dusting' that Rick mentioned.  I would inspect closely for that as a minimum.

Please keep us posted.