casting a change out head

I had hell with my gel coat when i tried using one. Much better luck with just fiberglass. I had a thread when i did my first one. Search ibex in this section and it will probably come up.

 

If you start making them ill be interested in a couple, not much out there for sitka blacktail anything

 

Mike,
You can make a fiberglass mold without gel coat. Gel coat is a polyester resin too, made to pick up the finest detail. I use white gel coat for one main reason: When you laminate the fiberglass layers the white color shows through well so you can see where your coverage is thick or thin. Here's the routine:

1. First seal the surface of the model with fast drying clear lacquer or paint, or whatever to seal the surface against the clay coming into contact with the separator. Cover the foam areas too for the same reason.

2. Paint a separator over the 'painted' surface so the resin won't stick to the model. PVA, polyvinyl alcohol, is the best thing to use. I never tried wax in any form, because it will blur the detail. PVA forms a thin plastic sheet not even bondo will stick too. I go 4 coats because it's thickness makes cleaning much easier when you de-mold.

3. Now thicken a batch of gel coat (or plain resin) with Cab-O-Sil or Aerosil just enough so it won't run when you paint it on. Paint it on thin. When it is set to the touch....

4. Make a resin 'butter.' Just regular resin thickened as above, mix the catalyst in then stir in short chopped pieces of fiberglass.

5. Using a small spatula or butter knife, apply the butter where the dam meets the model so that it no longer makes a 90 degree angle. Fiberglass strands or mat doesn't lay well into sharp angles. Butter in the eye and nostrils, the crease of the mouth and any other sharp detail. When the butter has set, check it for sharp peaks and sand them off.
6. Now you're ready to laminate.

I use 8 layers of 1 1/2 ounce matt applied in two stages. It's too difficult to tear and otherwise manage 8 layers at the same time so I do 4 layers twice, allowing the first 4 to set before adding the second 4. I use a 'wetting board', that is I pre-wet pre-torn and shaped fiberglass on a disposable surface (Cardboard is good) with a paint brush, then lift the pieces onto the mold (with very large tweezers. Tamp out all the air bubbles using a stiff paint brush or special roller. Also the thicker the applications the greater the chance that the resin will get real hot or kick off too soon.

This is very brief, but if you're already familiar with molding techniques, I think I've answered your basic question and then some.

 

noted

 

If you are going to use this as a production mold, just use tooling resin. No gel coat needed, and is made just for production molds