Plug finish

All,

I have always preferred the open cockpit tunnel look and I am making a plug for a tunnel cowl. I carved the plug from clear pine and I sprayed several coats of Krylon auto primer with Bondo underneath. I am pleased with how the plug turned out.

In the past, I sprayed a couple of coats of epoxy paint over the primer before waxing the laying up the mold. However, I have been told that the primer finish works better and I could start waxing the plug. Can you share your experience? I spent several weeks making the plug and I want to make sure I will not ruin it.

Thanks,

kez

Kez,

I have made plugs with foam then apply a couple of light layers of fiberglass and epoxy resin then primed multiple times with Krylon primer wet sanded to 600. I then wax the plug with Partall Paste Wax three times. Then spray or brush a layer of PVA or Partall mold release film.

I never had a problem with separating the plug from the mold.

Good Luck,

Bert Dygert

Bert Dygert said:

Kez,

I have made plugs with foam then apply a couple of light layers of fiberglass and epoxy resin then primed multiple times with Krylon primer wet sanded to 600. I then wax the plug with Partall Paste Wax three times. Then spray or brush a layer of PVA or Partall mold release film.

I never had a problem with separating the plug from the mold.

Good Luck,

Bert Dyger

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+1!

I've had problems with mold release wax even after 10 coats but with PVA it will come right apart. it's water soluble also so if it is real stubborn some hot water in a pryed up corner will dissolve it and help it come apart . Then you can polish the mold to a shine .

Inexperienced composite molders should use a proven mold wax AND PVA. Partall wax is a well proven choice.Some waxes bead up the PVA. Anything with silicone in it (like some auto waxes) will only cause problems. Do not use an applicator that has been used to wax the car, use a clean, new one. A few composite people I have talked to have removed anything silicone from their shop. There are many very cool mold releases out there, they are for the production people, the internet is littered with people who have stuck a mold by not using PVA. I prefer using only two part paints and only epoxy primer on my plugs. If I am in a hurry, I will only use flow out coats of epoxy applied with a foam brush and sand it to 600 grit. Striving for perfection in your plug will only serve to drive you nuts. You are going to prime and paint the final part anyways?? I am not a fan of rattlecan paints in plug work or for that matter anything else.

Been using Partall #2 wax and Partall #10 PVA for years, work very well together.

http://www.rexco-usa.com/

Terry Keeley said:

Been using Partall #2 wax and Partall #10 PVA for years, work very well together.

http://www.rexco-usa.com/

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Good link ! always good info from actual makers of parts . I have several cowling molds that i have spent the time to polish and now with a light app of release wax after the part is made they literally blow out of the mold with air .

no advice KEZ

but sure would like to see the open cockpit cowl

when you get them done

marty

Using a rattle can primer to me is risky, as I have had the primer get gooey under the heat of the gel coat and layup. I only use duratec surfacing primer for plugs, which is highly sand-able, and will buff to a very high shine, then I use Freekote NC-770 semi permanent mold release. Paste wax caused so many issues in the past (complete failures as well), but the Freekote products are excellent, and once the mold is done, the Freekote'd mold, if taken care of, can have multiple pulls before a recoat is needed...The nice thing, is a recoat is painless, just spray it on with their aerosol style can, or wipe it on if you buy it in the can, let it flash, then wipe it lightly off...I do 4 coats of the Freekote on the initial "waxing", and that takes me maybe 20 minutes to do, and 20 minutes for the part to "rest/ fully cure", then you are ready to lay up. Just my 2 cents. Kentley Porter is a sales rep for Freekote, and will gladly sell you what you need, and give advise on how to use it. Heck, he showed up at my door and taught me initially!

Mike

Tom Foley said:

Terry Keeley said:

Been using Partall #2 wax and Partall #10 PVA for years, work very well together.

http://www.rexco-usa.com/

Click to expand...

Good link ! always good info from actual makers of parts . I have several cowling molds that i have spent the time to polish and now with a light app of release wax after the part is made they literally blow out of the mold with air .

Click to expand...

Hi Tom,

Are these new waxes able to be used as a release agent with epoxy? Years ago we could use waxes when using polyester resin but not epoxy, we always used pva with epoxy other wise we had a part that never came out of the mold and usually ended up having make a new mold.

Thanks, John

Thanks all for your reply. I am attaching a picture of the cowl plug I am working on plus a couple of other plugs I have successfully made parts with. You can see I sprayed a final coat of epoxy paint in my previous attempts including a .21 size deep vee hull. But I am going to try this time with just a primer finish.

Because I use the plug only once (hopefully I can make many parts out of the mold), I am too lazy to use epoxy primer. I have been using the Krylon primer only because no clean up is necessary. If I will be using the plug to make multiple molds, I will probably go with epoxy for a durable finish.

I have always used PVA on top of wax whether I use polyester or epoxy resin to get that extra insurance that I will not lock up the plug.

Marty, the cowl will go on a WOF tunnel with an open cockpit. I know an open cockpit may add more drag but I think it looks better.

Thanks,

kez

Guys,

Here is a shot of a cowl plug all wet sanded and waxed. I spray PVA on the plug. I then use White Epoxy Tooling Gel and laminating resin from Resin Services is Sterling Heights, MI.

Enjoy,

Bert Dygert

Freekote is probably the most popular permanent mold release used in RC modeling. It does have an expiration date though. It is not perfect and has been known to fail. https://www.rcgroups.com/forums/showthread.php?t=1971273 A couple people have reported it doesn't like Klasskote or auto two part paints sprayed into the mold as a surface coat on parts. I have found rcgroups composite forum a great source of info and like to surf by there regularly.

A tip from an Aussie modeler was to sprinkle your waxed mold or plug with talc then lightly blow off.( he used an old flour sifter) Then spray your PVA. seems to help the PVA lay down and not bead. I usually have to put the PVA on with several very light mist coats to keep it really smooth.

I used to have fish eyes when I sprayed PVA using a Prevail sprayer. Then I found that if I lay down a heavy coat with a foam brush, the PVA will flow out nicely. If fish eyes start to develop, I just run the foam brush over it again. My experience with PVA is that a slightly heavy coat works better than a thin coat. Kind of counter intuitive.

kez

Bert Dygert said:

Guys,

Here is a shot of a cowl plug all wet sanded and waxed. I spray PVA on the plug. I then use White Epoxy Tooling Gel and laminating resin from Resin Services is Sterling Heights, MI.

Enjoy,

Bert Dygert

Click to expand...

Nice work!

I use a small air brush to spray on PVA. It will not bead that way. I have use the brush technique as well, but tends to add texture to the surface. So I usually go with the air brush.

Years ago I used automotive primers to finish plugs. Once I used Duratec I have never used anything else. It has a propietary formula that makes it sand easy but yet come up to a deep shine, something that the auto or rattle can primers will not do. Because it requires catalyst, it will not fail from being soft or uncured. Tooling gel is a waste of money building rc molds. It is designed to withstand high resin heat in mass production heavy lay ups. A color agent added to finishing resin makes a great surface. As long as it is polished and waxed properly nothing will stick in it.