Epoxy mould or tooling gelcoat mould?


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Kacordy
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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
antonkov
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I just posted a similar question. Never tried spraying epoxy but from what I read it is not a very good idea. If I had to, I would look for some military-grade bio-hazard suit to not worry about the exposure. When it is in liquid phase, all you need is an apron and gloves, having it airborne takes the game to a different level. Other than spraying, I totally agree, epoxy surface coat seems to be a good idea. Now wonder whether it really is when looking from practical experience.    


Kacordy
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antonkov - 9/27/2020 7:05:19 PM
I just posted a similar question. Never tried spraying epoxy but from what I read it is not a very good idea. If I had to, I would look for some military-grade bio-hazard suit to not worry about the exposure. When it is in liquid phase, all you need is an apron and gloves, having it airborne takes the game to a different level. Other than spraying, I totally agree, epoxy surface coat seems to be a good idea. Now wonder whether it really is when looking from practical experience.    


Why not brush the epoxy onto the plug, take a heat gun to slowly float any air bubbles out, let it tack, then layup enough reinforcement to make the mould?   I’m going to start another thread on gel-coat but I ran into this issue yesterday. What causes Gelcoat to Crinkle like this? 

antonkov
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That'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)


Edited 4 Months Ago by antonkov
torsten Ker
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Hi
I had the same with the tooling gelcoat after the first infusion,
It turned out that I was not paying attention enough when putting the laminate on top of the tooling gelcoat having airvoiuds between the gelcoat and the supporting laminate

After my first vacuum infusion I had exactly the same and had to repair the mould
Hope that helps
T


torsten Ker
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torsten Ker - 9/28/2020 9:30:04 AM
Hi
I had the same with the tooling gelcoat after the first infusion,
It turned out that I was not paying attention enough when putting the laminate on top of the tooling gelcoat having airvoiuds between the gelcoat and the supporting laminate

After my first vacuum infusion I had exactly the same and had to repair the mould
Hope that helps
T



PS:
and I had small soft areas in the tooling gelcoat because I did not mix it properly

Hanaldo
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antonkov - 9/28/2020 5:49:10 AM
That'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.
GO

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