Scott Smith

My Feedback: (4)

Destroyed my plug getting it out of the mold today. Apparently ten coats of wax and two coats of PVA wasn’t enough.[:@]

Molds overall look great except were the lacquer primer stuck. I was thinking of dissolving the paint out with some MEK. I can’t afford to damage the mold however with the plug in the trash! Any other ideas or thoughts?

Thanks,

Scott

davidfee

Start with something gentle, like denatured alcohol or mineral spirits (paint thinner). Save the MEK for when you need to soften and remove the epoxy itself! [X(]

I've seen this happen with primer before. It happened to me once when I had several coats of primer over a soft balsa plug, with no glass to harden the surface.

Once you have the molds cleaned up and well waxed, then lay up some really heavy parts, including the flanges. These will be your new plugs, should you ever need to make new molds.

Good luck,
-David

sayno2glo

My Feedback: (2)

I've had this happen to me many times. It's not necessarily because lack of release agent but just bad adhere between paint and plug. I would just scrape it off with Slowflyer prop or similar. With solvents you could damage the surface.
/Antti

Scott Smith

My Feedback: (4)

I did try scraping it with soft plastic but it wouldn't touch it. Acetone took it right off and didn't affect the mold. Under the paint was a nice layer of PVA that had to be washed off.

Thanks for the replies guys...time to make some parts!

sayno2glo

My Feedback: (2)

Glad you solved the problem. I'm surpriced that PVA didn't help.

troyhm

Hi Scott

havent spoken to you for a while are finally on track and buildint my patriot again are those molds of the patriot 3d. You did metion that you were building a set a while ago. Can I buy a set of you if they are ?

Thanks

Troy

Scott Smith

My Feedback: (4)

Hi Troy,

Yes, they are Patriot 3D parts. I'll send you a PM.

Scott

buttuh

Next time try a polyester based primer to coat your plug. Duratec makes excellent primer that can be polished specifically for the composite industry.

Spaceclam

I'm a beginner at making molds, but now i am pressed for time and need to make some molds for some fiberglass intake ducts. what is your guys's procedure, what do you use to make the molds? what do you use to keep it from sticking? what resin do you use? I do not mean to hijak the thread, just PM me a reply, but i really need some help here. what would you tell a beginner to get started off making thier own parts?

Scott Smith

My Feedback: (4)

The CST [link=http://www.cstsales.com/HTFiberglassMold.htm]tutorial[/link] is a good place to start.

I found a local fiberglass distributor [link=http://www.mertons.com/]Merton's[/link] that sells System Three resins so that's what I use.

Five (or more) coats of mold release wax and three light coats of sprayed PVA has worked well for me (except for that one time when the primer coat failed)

If you’re pressed for time...that's a problem. It's a long process from plug, to mold, to final parts and you need a lot of patients waiting for each step to properly cure.

Speaking of curing, a “hot box” is essential if working in cool conditions. Use foil lined foam and light bulbs to easily create a 100-degree environment. The resin set time is cut in half for every 10-degree increase over the stated temperature. It still takes weeks however to fully cure.

For the mold lay-up, start with a gel coat (resin/graphite powder/colloidal silica.) just as described by CST. Allow this to set for about an hour then brush on a thick coat of resin and start applying the cloth. 1 ½ oz cloth is good to start with so you don’t end up with any air bubbles in the corners. Then follow with a layer of 4 oz. Allow this to set for an hour and repeat with 4 to 6 layers of 6 oz cloth. You want about a 1/4 inch mold thickness when you’re done. The most important thing is to prevent any air bubbles so I believe it’s ok to use small, overlapping pieces of cloth (rather than one large piece) to prevent wrinkles and voids.

Spaceclam

what is mold layup? in the last paragraph, are you talking about making the actual part or the mold? what do you mean by the plug? also, in the turotial it shows a parting board. is that two pieces or one? wouldn't there be a gap where the parting board is?