On Jan 6, 3:24*pm, " wrote:
Having done several of both, I do not see a clear answer for a
refinish.

One issue I do see clearly:

The root cause of essentially all the finish problems observed in
gelcoated gliders lies in the criminally substandard "modern"
materials used by most of the manufacturers.

*There is abolutely NO reason the gelcoat finish on gliders should
fail. *Gelcoated sailboats are subject to high humidity, salt water,
huge structural loads, and a lack of care by their owners yet do not
display the problems we see in our aircraft. Libelles that are 30
years old still have nearly perfect finishes. I have a gelcoated
camper shell on my pickup that has been essentially ignored and
outside for 17 years old and shows no sign of crazing or failure. *I
know of several Grob products that have been out in the western USA
for 20+ years with little or no finish care and they have not
crazed.

If $100K gliders were Dodge pickups, there would be a class-action
suit filed against the manufacturers for shoddy materials.

Rant Off. *Back On Topic.

"Gelcoat" Refinish (catalyzed polyester paint): *Poly-Lux, Prestec,
Simtec, Vorgelat, Schwabellac (sp), Ferro, and many others

Pro's: Less skill and facilities required to apply and end up with a
good finish. *Far less hazardous to work with. *Easier to fix nicks
and dings. *Can be profiled/contoured years after application.
Typically this can be done at least once and usually twice before
significant sand-through of the finish occurs. Less expensive than
PU

Con's: *All things being equal it is not as durable as 2-pack PU,
especially if the ship is subject to environmental abuse (tied out
full-time) *Requires more waxing/polishing. Subject to stress cracks
when applied thickly to floppy wings but this can be mitigated. Can
yellow with time.

2-Part Paint: *PPG, Dupont, Glasurit, Imron, many others

Pro's: *Very durable, shiny finish that can withstand the elements.
Does not yellow.

Con's: *Very hazardous to apply (especially isocyanate catalyzed
types), Requires very good equipment, good facilities, and superior
skill to apply well. *Very expensive paint systems (as much as $400
per gallon). *More expensive and time-consuming to repair nicks and
dings, *Cannot be profile/contour sanded after application without
repainting due to thin topcoat film thickness.

Someone mentioned that PU refinishes weight significantly less. *That
has not been my experience. *The PU topcoat is very thin but the
amount of primer-surfacer required to contour the surface and fill all
the pinholes in the fiberglass seem to negate any weight savings over
gelcoat. This is especially true when individuals have piled on the
primer and not sanded enough off and/or not removed all of the
previous finish.

Moisure (vapor) migration in and though epoxy composites can lift PU
topcoats due to their impermeability. *Polyester coatings are porous
and allow migration.

For racing-class ships that will be taken care of, my vote is
"gelcoat".

Hey Mark,

Very thoughtful post. Quick question for you. Assuming you used
Simtec (Prestec) gelcoat, do you remember which of their formulations
you used? We (meaning glider pilots who are stupid enough to fiddle
with this stuff) seem to use the 2381 formulation, but their
literature suggests they have a formulation with additives designed to
make the finished product more flexible. Just curious whether anyone
has experimented with the various flavors of the polyester-based
products.

Thanks,

P3