GRP Moulding - The Process

[Lakesailor]

These guys have some good videos on their site with the basics..

http://www.ecfibreglasssupplies.co.uk/

These are the people I bought my mat and resin from. And now some flowcoat

 

[30boat]

I would advise you to make a proper mould.Finishing the fiberglass is going to be a hell of a job especially with that kind of jelly mould shape.Making a mould is not very hard and even for a one off the savings in labour are more than worth it.Just make sure the plug is not porous at all and well finished.

 

[Lakesailor]

I can see what you are saying, but don't see the difference in making the plug well-finished and making the grp casting well-finished.

The people I bought the materials from (East Coast Fibreglass Suplies) sell various release agents, including beeswax and silicone spray!

 

[Vara]

Season first practice is 11 August so knowing Lakey, he will want it looking its best for then. Our first debate on this topic concluded that a washing up bowl would do the trick!

HF

Well with all the MMGW and CO2 levels, that will probably be winter, I predict snow.

 

[Elessar]

If size isn't critical but you wish to replicate shape, lay up GRP over the top, fair that, gelcoat that, polish then hack away the plug.

Thats's what I did for my dash - made the plug out of foam for easy hackability.

Saves the cost and effort of a mold, ideal for 1 off projects.

 

[Vara]

If size isn't critical but you wish to replicate shape, lay up GRP over the top, fair that, gelcoat that, polish then hack away the plug.

Thats's what I did for my dash - made the plug out of foam for easy hackability.

Saves the cost and effort of a mold, ideal for 1 off projects.

when you say foam can you be more precise, as one of my winter tasks is to make a new binnacle so this sort of thread is gold dust.

 

[Lakesailor]

You are just not paying attention, are you? Electric carving knife for sculpting. http://www.ybw.com/forums/showthread.php?366686-GRP-Moulding-The-Process&p=4276988#post4276988 Summary for you

 

[Lakesailor]

If size isn't critical but you wish to replicate shape, lay up GRP over the top, fair that, gelcoat that, polish then hack away the plug.

Thats's what I did for my dash - made the plug out of foam for easy hackability.

Saves the cost and effort of a mold, ideal for 1 off projects.

Yep that's the plan. I did say that but perhaps it doesn't translate.

 

[Avocet]

Just a thought, I've used stuff called Durabuild to fair plugs and fibreglass stuff. It's like a gelcoat that you can spray (in a gravity-feed gun). Relatively easy to sand and pretty high-build.

 

[Lakesailor]

I've just seen the price of Durabuild. I wanted this bulge to be the cheap bit to cover over the main job.

My gun is suction feed. 1 litre of Durabuild would coat the bulge about......oooo......err...... 10 times.

 

[Twister_Ken]

Do trials cars still use Austin 7 engines?

 

[Lakesailor]

The answer can be expressed with two letters.

 

[Twister_Ken]

So what do they use now? It was an A7 in my uncle's car when I was his bouncer, back in the late 60s.

 

[William_H]

Hi Phil it is good to see you out in the shed again. As said and I would reiterate it will be easier to make a mold then mold the final product. It will prove to be quicker and probably cheaper.
You can make the plug (I havn't heard the name you used) very smooth with palster and similar cheap stuff then as said lots of wax etc for aiding release. You might want a frame for stiffness of the mold. For boats they use a complex steel frame.
The fianl production of the cover should be quick and easy. The advantage of making a female mold is that the surface will be as perfect as the original plug (you can repair and claen up the inside of the mold if necessary) but mostly that you can easily add stiffening sections which end up on the inside so allowing the actual skin to be thinner.
In any case releasing the GRP is not so much of a worry as you can destroy the plug to release the mold then destroy the mold to release the final job. good luck olewill

 

[Elessar]

when you say foam can you be more precise, as one of my winter tasks is to make a new binnacle so this sort of thread is gold dust.

yep you can get boat building foam used in stringers, decks etc instead of balsa. The GRP shop should sell it. Lots of different densities, the dense stuff is very pricy, but the cheapest is fine.

Glue it together with a glue gun, carve to a pleasing shape with a surform.

sadly the pic with just foam pre GRP is missing but you can get the idea from the fairing process here

 

[Vara]

Cheers Mark, just what I needed to know.

 

[MYStargazer]

Looks fantastic. Is that flocoat on top? How well does it blend in with the original gelcoat?

 

[CreakyDecks]

Isn't all the polishing and waxing to achieve a perfect finish in a gel coat? Since you are moulding on the outside of your plug and presumably don't really care about the inside finish, can you not simply cover your plug in cling film and lay on top of that?

 

[30boat]

Isn't all the polishing and waxing to achieve a perfect finish in a gel coat? Since you are moulding on the outside of your plug and presumably don't really care about the inside finish, can you not simply cover your plug in cling film and lay on top of that?

Plastic parcel tape will work as well.Waxed paper tape even better.

 

[Lakesailor]

Yes, my thinking is that better the plug the less chance of transferring any bumps or hollows to the moulded "skin", so less fairing to do. The job on Elessar's binnacle above is exactly my chosen method. I need to be able to remove my plug easily, so the release agent will facilitate that.
I use parcel tape for epoxying joints and such but have never managed to lay it down in areas without creasing.

I'll try to photograph the laying-up stages, but need to remember to take gloves off before grabbing camera!