Who here has worked with gelcoat?

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clutchdust

Millionaire Playboy
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I'm working on a mold for a project. The plug is a composite of fiberglass and filler, but I need to make a two piece negative of this plug. I'm using fiberglass for both sides of the mold but I understand I need to cover with gelcoat to get a final finish. I've already coated one part of my mold but it's still tacky and I need to get it to cure before I can cover it with release agent. The supply house told me it doesn't cure hard except under "anerobic" conditions, so they suggested covering the gelcoat with a film like Saran Wrap but I had my parts covered for about 4 days this week and it's still tacky. Is there a timeframe I have to work with the gelcoat?
 
CLUTCHDUST -- Hope I can help -- built a few molds and boats so lets see.

AS I get it, you have the following ( I Hope) And I appologize for this being üpside down --
But think of these as STEPS beginning with your "master" or PLUG as a male is called:

Mold Piece (The original) It will be on the BOTTOM, Next;
WAX - Several coats (Why several? -- you want NO VOIDS!) Follow with;
Release agent (PVA works very well) Spray it on. Let this all dry HARD NOW,
NEXT I'd continue by;
Spraying on TOOLING GEL -- its a hard finish gel coat designed for the surface of the mold not run of the mil gelcoat
(And yes it does cure ANEROBICALLY) -- Thats why you now,
Start carefully laying up your Mold fiberglass and resins - I'd begin
1. Surfacing Veil -- very fine -- like tissue paper,
2. Several layers of CSM (chopped Strand Mat -- Not too heavy)
3. Woven Mat for some strength You can use all sorts here but you're proly ok with run of the mill
4. CSM -- now start thinking a bit heavier - further from the master and more strength please...
5. WOVEN ROVING -- Thats the big fiber stuff, and alternate
6, 7, 8 CSM/MAT/CSM/Roving, add;
9. Some support suructure;
10. CSM to hold in place a bit;
11. Roving - to make it final
- and if the part is not to big -- you are probably there! If its epoxy your using and want to keep it from degrading -- remember it needs UV protection - so you can paint the backside of the mld -- but now youmay have guessed thats why a lot of molds are made of polyester!

A NOTE to consider - -You want to SPRAY -- or ROLL on the material products -- If youuse a brush -- you'll risk "scaring" the release (PVA and WAX) and have the mold stuck to the master!

SO let me know where you are and yes the plastic wrap oughtto help the cure -- but whats the next step in your layup? If it doesn't cure -- you may have to remove it and mark it as a lesson learned. :(

BTW make sure your fiberglass, resin and Tooling Gel are compatible. That is you want your "glass "sized"for Epoxy - or Poly and likewise the Gel needs to be compatible withthe resins. Many Gels are designed for Polyester - but you can (after a ploly interface over the gelcoat - lay up al the epoxy you want.) You're noy making 1000's of copies are you?

Good luck and,
Cheers - Jim

Sorry - My book is not finished - else I'd have a shameless plug for it....
 
clutchdust said:
I'm working on a mold for a project. The plug is a composite of fiberglass and filler, but I need to make a two piece negative of this plug. I'm using fiberglass for both sides of the mold but I understand I need to cover with gelcoat to get a final finish. I've already coated one part of my mold but it's still tacky and I need to get it to cure before I can cover it with release agent. The supply house told me it doesn't cure hard except under "anerobic" conditions, so they suggested covering the gelcoat with a film like Saran Wrap but I had my parts covered for about 4 days this week and it's still tacky. Is there a timeframe I have to work with the gelcoat?
Click to expand...
What are you making Gary? Is the mold something you plan to use a lot or just a couple of times?

Jim's put down some good info there but you could probably shorten your work a fair bit if you're not making something with a mega complicated shape or if you don't plan to make zillions of pieces from your mold.

Can you post some pics of what it is you're trying to mold?

Oh, I don't have much experience at fiberglassing, but I wouldn't be real happy if the gel coat hadn't cured after 4 days! How tacky is it?

Anyway, post up some pics...
 
clutchdust - "Wayne of Arabia" has a good point there.
I have assumed its a BIG Part and the mold would need to be rigid. If its something small, you could consider using a silicone mold -- split etc, but you'll need to solve the gelcoat problem first. For release I'd use spray PAM - or vaselene thin before the silicone layup/mold making.

If it (the gel) won't harden - I'd proly strip it (chemically - acetone, mineral spirits, etc -- hope the part is not one you borrowed), then clean it up mechanically - and re do the 'glass and bondo.

If its a secret part - or you havent any pics - a general size idea would help.

Cheers - Jim
 
The part I'm working with is not very big, nor is it very complicated. Sorry, but right now, let's just call it "proprietary". I'm beginning to think the gelcoat is a bad idea. I think I'll just paint the surfaces of my mold and wax the snot out of them. Speaking of wax, is there any reason I can't just actually take wax (like from a candle), melt the crap and brush/flow it onto my mold??? Why all the hoopla with release agent and stuff?
 
clutchdust --

No -- not candle wax - not PAM or Vaselene for a fiberglass mold! While cheap enough - it may cntain carbons and other burnt ash to screw it up. And it may not "level" to your satisfaction.

The Hoopla - -its what works. There are shortcuts - but not always predictible, repeatable, or worth the redo when they don't turn out. And best left after you have had a chance to understand the process a bit.

"If you haven't got time to do it right the first time..."

You can use Brown Packing Tape, plastics, mylar, etc over the part you are molding -- if it fits well -- but will it still need wax. Car wax -- High Carnuba in a pinch -- but if you want to avoid a problem - then use wax designed for the job. Its not expensive. And McMaster gets it to me nearly overnight.

You mentioned a 2 part mold - is that inside and outside - or does the draft reqire the 2 parts. Will you be doing this open mold -- or vacuum aided layup -- or vacuum infusion - or a variant of RTM? I have done all of the above (have much of the gear on hand) and I a few ideas that could help you get a good product. As examples I have done silicone resin molding of stick grips, a variety of boat parts in resin, fiberglass, and carbon fiber. I built boats for over 40 years, hang gliders and even a moldless fiberglass construction of a 56 foot catamaran. My next project -- something simple I think, flares.

I'd be happy to sign a non-disclosure agreement - legaly binding, and work with you offline -- REAL CHEAP (like free), if you want. If interested PM me.

Some stuff for you to think about.

Cheers - Jim
 
I will defer to your experience. This is really uncharted territory for me so what I'm doing is making the two halves of my mold, then bolting them together and pouring in a two part plastic I got from TAP. That's been my plan anyway. If you have a way to make this go faster, I'm all ears. This stupid little project has take about 100x longer than it should have mainly because I'm learning (and not always the right way) as I go.
 
Grasshopper, the hill may be steep, but by one step at a time --we reach the mountain top!

So, On the plus side, your plan sounds good.
If you are inclined to starting over, and the piece/product is fairly small, I might suggest that you use a silicone mold. I have done some Aircraft stick grips using this method -- and just as you have planned -- it was poured into the mold (also a 2 part split), using a plastic like you are suggesting.

BUT, that you may have already started a fiberglass mold, you can do the same kinda thing. You'll need a want a vent and pour hole (and a plug to fill the hole). If the plastic you have is slow reacting and a single hole is ok then only one required. Another approach (I am plannig and may soon build a tool for it) is rotomolding.

This is what you might consider for your prioject. You can get by without the special tool.
1. Build the mold.
2. Wax, prep etc and bolt together
3. Now you pour the plastic in (remember waxed prepped etc) AND CAP IT!
4. Rotate the mold, twist turn, move slowly, in a 360 degree path until plastic/resin hard,
5. Now, open the mold-- VOILA!

Just think of all the cool stuff you're learning along the way! Well, thats what I kept telling myself ~~
Let me know - I could send you a small "glob"of wax if you wanna play with it - and a lot of sources for bits, silicone, resins etc if interested.

Cheers - Jim

BTW -- that you have TAP Plastics -- may I guess Left Coast? Hell didn't seem that close when I was last there!
 
Do you already have a piece your trying to duplicate Gary - ie, a plug?

If you're making it two piece, there's a bit of messing around but you could probably simplify it a fair bit.

You'll first need to wax the crap out of it! I couldn't find mold release wax out here so I just used carnauba wax when I made my C5 "Corvette" script. I know that wasn't a two piece mold but the following is what I did years ago when I was messing around with something:

You'll need to mark half way on your plug where you'll make the two halves of the mold meet. You'll need to take into account any odd shapes or protusions when you do this.

Cut a hole in some board, the same shape as the cross section of your plug. You'll need to then mount the plug in this board so that the board lines up with your halfway mark you already drew. You'll then need to fill in any gaps where the board doesn't quite meet the plug with some non-hardening clay or plasticine.

Now wax the half of your plug that's exposed as well as the board it's mounted in.

You should be able to buy PVA mold release, but I couldn't find any out here so I didn't bother with it and went straight to gel coat.

Carefully brush on a layer of gel coat over the exposed half of the plug and the board - go out far enough on the board to make the mold flange.

When the gel coat gets "draggy" (sticky to touch but without it coming away on your finger tip) apply another layer of gel coat.

Once the second layer of gel coat becomes "draggy", mix up some resin and brush some over the gel coat then start layering on pieces of fine glass mat(the tissue paper type that Jim mentioned). I Used a paint brush and kept dabbing it down into any tight areas, making sure all the air bubbles are gone. Make sure you also go out far enough on the board to cover the gel coat on what will be the flange.

When you've put on a couple of layers of the fine mat, let the resin get "draggy", then mix up some more resin and start layering on normal weight glass mat. Make sure you do the flange too. When you've put on a few layers of that mat, and before the resin goes off, glass in a piece of metal or something to give the mold some rigidity.

Leave it alone until the resin is partially cured but still soft enough to be trimmed with a Stanley knife or something. Trim through the glass down to your board to give you your flange - 1 inch, 2 inches - up to you.

Leave it now until it's fully cured.

Use a wedge or something to get under the edge of the flange on your mold and carefully lift up the mold and plug in one.

Now repeat the whole process with the plug still in the mold half you've already made. When you've got all the glass laid up, trim the flange to match the first half (before the resin fully cures) and once it has fully cured, drill some holes through the flange so that you can bolt it together later when you're using it.

Once fully cured, use some wedges to pop the mold halves off the plug. Once you've got them off, polish the surfaces of your new mold halves to a high sheen, which will make future molds from it easier to release.

I would suggest you tried this method on something you can afford to throw away, before molding your real thing!

I hope this has been some help mate...
 
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Real good fill-in there Saudivette! You've given him some nice details to work with -- and have shown how steep the mountain can be!
I'll add again - if you can, spray on the gelcoat -- or use a foam roller(compatible with your resin of course). As it gets tacky then feel free to use brushes. You want to try and keep from scaring the waxed/PVA release agents. DABBING Action as recommended is always best - not pulling the brush.
A cheap (disposable) alternative to a spray rig -- a toss it -- don't clean it (not ecollogically sound but thats not the discussion here) are the Prevailers (Home Stores usually have them). Work like a small airbrush/custom spray can. You can reuse the bottle but not the propellant once its gone - buty a replacement. Work great for laying down the gel coat, or the PVA. Again - for molds the best choice is tooling gel - its a harder surface and designed for multiple use. Again, still cures anerobically.

Get Sticky and have fun! Maybe I'll shoot the flares project as a guide, if I can remember.

Cheers - Jim
 
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Thanks guys. That's a whole lot of info there. My problem now is that I'm so far into what I've already done, I'm not willing to start over. Unless this one ends up in total failure. So right now, I have my plug made and one half of my mold. I just need to get the second part made and prep the surfaces for release.
I may have to discard the other part of my mold that was gelcoated as I'm not sure I can salvage that thing, but it won't be hard to make a replacement.
I appreciate the help though. Like I said, this has been a project a long time in the making and it's killing me that it's taking so long. I hope the prototype I'm making gets a positive response and I can manufacture these things, and maybe make a couple dollars. I especially hope I can get it done before someone else makes a competing product!
 
Ok a good product to market without any form of protection? Hope you get the fast bucks you want before some else splashes and undersells ya! Not much hope in ways of protection -- trademark, copyright, all cheaper that a design patent, let alone a utility patent. And even so, they're only good to use in a lawsuit - which costs YOU money too, so good luck and hope that you have some Honest competetion at best.

Best of luck, and

Cheers - Jim

BTW, if you're going to make the final as a solid resin casting -- be careful for shrinkage, and exotherm cracking. If you can make it as a shell, try the approach I suggested - manual roto-molding.
 
As soon as I have a presentable prototype, I'll post pics. I don't really know if this is something I can patent per se. It's just cosmetic do-dads. Everybody's got something, so I'm making one too.
Besides, I could spend the money and time to get a patent (if it would even apply) and then the damn Chinese would just import something under me and there's hardly anything I could do about it.
 
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