Gelcoat running on vertical surfaces

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#1

I am molding an upper radiator bracket using US Composites Orange Tooling Gelcoat. Last night I prepped the part (waxed + hairspray [didnt have a true PVA]) and for my first mold I’m kinda happy with the results. I knew going into this that this mold would be a learning tool so expectations were not high at all.

The side view of the part looks like the big dipper constellation, or a u with a handle.

The part was also painted with auto store brand primer, base coat and clear.

The problem are the two vertical surfaces and one high spot ran. The horizontal high spot left what looks like a small crack, one vertical part has no gelcoat remaining, and the other lost about a square inch of gelcoat.

I catalyzed at 2% per the manufactures instructions.

So, what did I do wrong? what can be fixed?

#2

If you sprayed your gelcoat, its important to lower the air pressure at the gun when doing tight or vertical passes. It helps to give ample flash time between in those areas too. Spray too much or too quickly and things can go south. Its also helpful to pre-warm the plug that you are molding.

#3

Nothing sprayed on, this was with a cheap HF 2 inch bristle brush.

#4

Applicator aside, think in the same steps as I mentioned.

#5

But how do you turn down the air pressue on brush! LOL Gotcha, I’ll pre-warm the plug with a heat gun then apply a thinner coat too.

#6

Its a little more complicated…you have to lower the blood pressure at the wrist to get the right finesse!

#7

The application of gel coat by brush instead of spraying is not as easy as it may seem to be, this being the reason why most of people spray it, you can use for taht if the Project is not large a polycon spray gun (search for it)and also, in regards to using cheap or available products like hairspray instead of PVA alcohol is asking for trouble, remember that the devil himself lives in the resin … :smiley:

#8

Add a bit of thixotrope, e.g. fumed silica

#9

Thanks for the feedback Jigger. Before investing in a gun I’d like to get familiar with the basics, and money is a bit tight right now.Trust me, I have my eye on a gun or two that I’d like to buy and will once I have a solid foundation.

As for PVA I received a few PMs recommending the Frekote sealer + semi-perm solution as a superior release agent and the added benefit that it doesn’t affect the finish of the part. Once I’m done with this business trip I will be ordering from Soller Composites.

Also, are you a true Spaniard? My family was either from Boada or Cordova and immigrated to Cuba in early 1900s.

#10

Thank you for the suggestion, what will fumed silica do to the gelcoat?

#11

Hi Burrito, yes spanish, living in the Canary Islands, many people from here migrated to Cuba including one of my grandfathers …
The POlycon gun I mentioned befor is quite cheap and useful, if you are on a budget, it should be of your interest. good luck.