By Kacordy - 9/16/2020 6:23:56 PM
I’m new to vacuum bagging and have a few questions. I just finished a couple plugs. I just made my first mould by spraying orange tooling gel-coat and 15% Duratec. I used carnuba wax and then sprayed PVA. I had to sand the new mould with 1500, 2000 and then polished with rubbing compound to bring it to a high luster. I had to go through this process because the PVA left an orange peel textured finish in the mould. Now I’m dealing with porosity in the gelcoat, very small holes over the entire surface. Not bad but a few holes per square inch. Now when I vacuum bag my part and pull it out it’s now going to have a nice finish. I can see that I will have to sand the part and clear it with 2K clear. What a hassle. So my big question is why not layup the mould by spraying an epoxy surface coat, and lay up the mould in epoxy and glass? The nice thing about epoxy is a person can slow down the cure rate when laying up the cloth etc. Is the epoxy surface not hard enough to endure a few part pulls? Thanks for your help, Allen
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By Hanaldo - 9/28/2020 10:49:24 AM
+xThat's right, sounds like a good, idea. There must be a reason why most go with the gelcoat, I can only think of the gealcoat hardness that helps in polishing and the easy of spraying.
That being said, PVA should not have left orange peel.
Here is a good guide on how to apply it: https://www.boatdesign.net/threads/a-pva-mess.41668 (second post down, by tunnels)
Gelcoat is just a significantly easier way of making moulds. Epoxy moulds are a different animal entirely, and take much more skill to make to the same standard.
As for alligatoring, it is an indication of under-curing of the gelcoat. Number of causes for that, temperature, catalyst %, gelcoat thickness, proper mixing, etc. All critical to get right when applying gelcoat.
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