applying mulitple layers of glass

[weissmarine]

Desiring multiple coats of glass. Do you wait for first layer to setup and cure completely before applying second layer of glass, third, so on and so forth? Also when working high temp and humid conditions is 209 Hardener (West Systems) the way to go?

[the1much]

i have no isea bout epoxy,,,,,well i have ideas,, but i dont work with it, so i dont know about the 209,,,,BUT,,,when you glass,, you need(SHOULD) do all layers at once,,that way you have the strongest bond possible. if you wait between layers,,you need to grind between layers,,,with poly and vinyl you need to grind after 24 hours,,,,,,,,is MUCH easier to do it ALL at once,,,,, unless your 1 of those freaks that loves grinding glass,,hehe

[tinhorn]

Like the1, I've never worked with epoxy, but my standard practice with polyester and vinyl ester was to apply the first layer (thin mat) against the gelcoat, let it cure, knock off the "needles and spears", then apply the remaining layers (light mat, cloth, more mat) together. One reason for the first "skin" is because excessive heat from a thick layup may cause sections of the gelcoat to prerelease from the mold, creating a permanent dent. Another reason for the skin layer is so you can really focus on rolling out ALL of the air bubbles that would otherwise show up as chips in the finished product.

If you're using laminating resin (no surfacing agent), complete cure at the surface will be impeded, making a superior bond with the subsequent layer. (I don't know if epoxy performs differently.)

[lesburn1]

Hi, the standard procedure when working with epoxy is to let the first layer "mostly" cure (ie. wait until it is just tacky) then wet out the surface and add your next layer. You must be very careful not to disturb the first layer. After the second layer is on you can add a third... If you let the first layer fully cure you will need to sand off the surface. If you can, get yourself a copy of "The Gougeon Brothers on Boat Construction" it covers wood and composite construction processes. My copy was printed in 1980, but it covers the use of carbon fiber and a newer edition may be up to date in the use of composites.