On Oct 24, 1:42 pm, Matt Keast
wrote:
Does anyone know of someone in North Carolina or the
surrounding states that could do a professional gel
coat inspection? Preferably someone who has experience
with glider refinishing and old gel coats. I've been
unable to find any sailplane repair (refinishing) facilities
in the above area.

Hi Matt,

Not directly answering your question, but...

There are usually at least a few people in every club who are
competent to assess the state of gelcoat. I'll use myself as an
example. Though I'm not a "professional", I've done several sanding
and minor refinish jobs over the last 20 years. Having done that, I'm
certainly able to look at a wing and tell you whether:

- The crazing you see is "significant"
- Whether a light finish sanding would buy you some time
- If there was a refinish job, whether it was done well

It's really not rocket science. The tools of the trade a

- Your eyes
- A 4x or 6x loop magnifier
- Your fingertips

Just a quick and incomplete primer but:

- Start with the wings
- Examine for any obvious crazing with the naked eye. If you can see
this, it's really only a matter of time before a refinish will be
required. How long? If you can feel cupping (ie. the edges of the
cracks are lifting) or the crazing is in a checkerboard pattern (think
dried up lake bed), then a refinish is iminent. You might get away
with a full finish sanding to buy yourself a couple of years, as long
as you keep the ship well waxed and out of the wet. But, get the
checkbook ready.
- Next, take the loop magnifier and check a little closer. Can you
see fine cracks developing? If so, you have the onset of crazing.
If you do a finish sand and comprehensive wax job, you might have 5
years or more left. The trick is to again be sure to keep the wings
coated and dry. There are no guarantees, as I've seen some crazing
stay stable for 10 years and others progress very rapidly. Storing
the ship in a ventilated trailer in a hangar would be a good bet at
this stage.
- If the ship was refinished, the first thing is to find out who did
it. There are shops with a very good reputation (e.g. Gherleins in
PA) and others with a so-so or poor reputation (won't mention names
here).
- Take out the loop and look at the scratch patterns on the new
gelcoat. All sanding leaves scratches; the trick is for each pass to
totally eliminate the scratches from the prior grade. On the wings,
you should be able to see only very fine surface scratches with the
loop magnifier, and they should all be in one direction. Typically,
they will be on the diagonal to the chord line. If you see cross-
hatching or a checkerboard, it usually means that the sanding passes
weren't thorough. Also, the surface may look "milky" instead of
"glossy", even after spot-buffing. That would worry me.

Anyway, that's a quick overview. As I said, anyone who is serious
about maintaining their own glass ship would know this stuff. Hope
this helps.

Erik Mann
LS8-18 (P3)