yclui

My Feedback: (1)

Hello everybody,

I wonder if anyone know what kind of gel coat materials are used in all-mold epoxy-glass gliders like the Nemesis 60" slope racer. the wing servo cover of my Nemesis got damaged and I am planning to made a replacement by myself. The original cover is dark blue in color and the gelcoat was sprayed on as I can clearly see dotted patterns when holding it against strong light. What amazes me is that although the gelcoat is extremely thin, the opacity is very high.
I have tried to make the gel coat by mixing color pigment ( in paste form ) into West System epoxy 105 resin/206 hardener but before the original opacity is attained, the dosage of color pigment is already so high that the cured resin becomes unacceptably soft.\

Can anyone offer some suggestions on materials that I can try ?

Thanks in advance ,
Y C Lui

ptxman

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The color coat you are seeing is more than likely paint sprayed into the mold prior to glass layup. If you want to replicate those results, that is the method of choice. Paint is basically a high concentration of pigment minerals in a carrier/binder base made of urethane, epoxy, enamel, lacquer etc. It is heavier than epoxy but the coat is very thin. Higher end auto 2-part catalysed paints will give you the toughest & lustrous finish but you can also get away with spray bomb type paints (unless you require fuel resistance). The big advantage of pre-painting is that your layup can be very lean in resin concentration without worrying about pinholes or related epoxy surface defects.

Adding pigment to the layup epoxy gives only yields a translucent color & is further affected by the color of glass/kevlar reinforcement cloth. Gel coat is less preferrable for flying components IMO because it is heavy & adds little strength. Gels are used for minimizing cloth print-through but you can control that aspect with a light cloth like 0.7 - 1.4 oz against a pre-paint surface with negligible surface effects. Furthermore, the painted surface can be wet sanded & polished carefully for an outstanding finish.

yclui

My Feedback: (1)

Thanks ptxman.

winship

Ok! what type of mold release is used when painting into the mold?

ptxman

My Feedback: (2)

Prepainting molds & related (wax) releasing agents have been discussed here on rcu. Check the link below which gives some background & a link to H&M Racing. They supply a super wax for this application which I use & works great. There is nothing else like it that Ive found.

http://www.rcuniverse.com/showthread...hreadid=278002]

rjmods

My Feedback: (7)

HI,
If you are trying to make an epoxy gel coat you must add a thixotrophic additive otherwise all you get is colored resin. Not sure where you would get it in the US though.