How do you get gelcoat on the inside and outside?

[Jleworth]

Hey guys, this is something that have been contemplating for quite some time but cannot figure out. I have been working with fiberglass for quite some time, making consoles, leaning posts and such in my shop. Recently, I have been thinking about making an overhead electronics box to attach to a hard top or t-top, Im sure you are all familiar. I want to make a mold so it can be reproduced but I cannot figure out how it could be done so there is a finished gelcoat surface on the inside and the outside. Is this possible? Is this typically done with vacuum bagging? I hope someone can give me some guidance. Thanks

[gonzo]

You make two boxes and glue them together. The outside has gelcoat on the exterior and the inner one in the inside.

[tunnels]

Originally Posted by gonzo

You make two boxes and glue them together. The outside has gelcoat on the exterior and the inner one in the inside.

you would make a outer mould and inner mould gel coat each one /lay them up then stick them together !! Simple !!

[Jleworth]

Thanks for the replies, I have thought about making two molds and pressing them together, which seems to be the only way to do it. Wouldn't there be an issue with getting air trapped in between the two pieces therefore getting improper adhesion?

[jim lee]

I think they are telling you to make the box in two pieces. Not using a two sided mold.

You can do a two sided mold, but those typically need to be vacuum tight. On the ones I've seen, you put in your material dry, close the mold, vacuum it down then shoot in the resin. Makes wonderful lookin' parts speedy quick, but the parts are not the best for strength to weight ratio. And making the mold is a real art.

-jim lee

[Herman]

Do a search for "RTM Light". But simple boxes can even be made with press-molding. Make 2 moulds (inside and outside). Gelcoat them, apply glass on the inner mould, pour resin in a X pattern in the outermould, press together, done.

Edge design of the mould is critical, though. But even a make-shift mould can produce nice parts.

[yellowcat]

You guys may have some suggestions .
Here is the picture:
My friend has problems with a car wash concrete floor, salts and sands etc (oils, gas, glycol, bird craps ...), i suggested to him to check out with a marine supply and they suggest a composite on top of the concrete and raise the floor with a dbgrating galvanized steel for the dirt and water to go thru. A composite with urethane blonwed under because they want to insulate and radiant heat (water) for melting ice from car washing in winter. The sands will be washed to the sides with horizontal springklers, all that is refiltered so no city water is wasted.
On top of the urethane, they suggested eglass and gel coat. I dont know all about gelcoats, but isnt epoxies better ? and for later repairs an epoxy paint could be an easier deal. Is there gelcoats tuff enough ? generally i always thought that gelcoats were more fragile than epoxies, i know it keeps chipping and hard to repair on my boats .
Thanks for your help.

[tunnels]

gel coat both sides ! Can also have all the way through just pigment the resin you are using and the color is total every where !.