On Feb 19, 4:30*pm, Udo Rumpf wrote:
First mask off the canopy *inside and out.
remove remaining Gelcoat, sand vigorously with 180 grit paper.
Brush off plexi glass dust, wipe with alcohol.
Use small spray gun and spray either Gelcoat or Poly Urethane.
If you use Gelcoat you need an additive which make it more flexible and
paint like. Urethane can be sprayed as is.
Keep the layer as thin as possible just enough to cover any dark spots.
Udo

At 23:42 19 February 2009, chris wrote:



Help, I have a chronic problem with my canopy. *Years ago the
plexiglass was replaced on my canopy. *Since I have owned my glider
the "white painted edge" of the canopy has been flaking off. *The
gelcoat seems to just lift off and flake away, leaving a ragged edge.
Some areas have the gel lift up into the slipstream probably not
helping the airflow.

Every year or two I mask off the edge and hand paint layers of gelcoat
back, then sand smooth and even again. *Then a few short months later,
time to do it all over again.
My new gel seems to stick better than the older stuff but even some of
what I put there has come off. *This seems to be a problem on the
overpainted plexiglass transition area and not the frame portion.

I think part of the problem is that the smooth plexiglass does not
make a good adhesion to the gel. *I also assume that there may be
differential expansion in hot/cold cycles, sun that may make the gel
and underlying plex to work apart?

Yep, Udo is right! You have no adhesion, remove all the old then sand
the plexy till all the shiny is gone. I use 220 on the outside and 40
grit on the inside when replacing a canopy. Don't worry about creating
stress risers. Carefully mask with good tape (I like the blue stuff
from automotive paint stores) because you can make good tight curves
and it leaves a clean paint line. Carefully sand right up to the
masking line, paint and wet-sand with a small block( 600W then 800W)
right over the masking tape till the paint depth = the masking tape
depth, Then buff before removing the tape for a crisp professional
looking job.
Cheers,
JJ


So before I put on more gel, I'd love to hear some suggestions on
surface preparation or materials etc.
I have Simtec Prestec 2781 gelcoat.

I have been hesitant to really scratch/roughen up the surface of the
plexiglas, the shop before me did not do it and I would be afraid of
creating any kind of stress risers but maybe I'm just paranoid.

Should I use some kind of primer?

Chris- Hide quoted text -

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