Making a fibreglass mold Part 2
Trueno light bezels waxed minimum of 4 times, then sprayed with a few light coats of PVA mold release.
We are now ready to apply the tooling gelcoat. Tooling gelcoat is a special gelcoat that is designed for molds. It is harder and more brittle than ordinary gelcoat, which gives a
much better mold surface. Most tooling gelcoats are thin and need to be applied by spraying. This is a pic of a gelcoating gun I use for most of my gelcoating. Cost about $15.
Gelcoat can also be applied with a brush. Ordinary gelcoat can also be used, but is not as hard or tough. Ordinary gelcoat also tends to contain many fine airbubbles when sanded
or polished. Ordinary gelcoat can be used for small production runs if needed.
Gelcoat applied. Gelcoat needs to be applied evenly to a minimum thickness of 0.5mm. Any less, and you will have problems with tripe (wrinkles). Slightly more you are just wasting money,
more than 1.5mm, and your mold surface will be extremely brittle. Make sure you do not, for any circumstance, exceed the catalyst ratio recommended. Most gelcoats use a maximum of 3% catalyst
to gelcoat ratio for a normal reaction catalyst. Best to read specs from your supplier.
As the light bezel has some sharp corners, I am going to use glass tissue as the first layer. This feels a bit like tissue and ensures that the glass will conform to all the intricate shape,
guaranteeing no airbubbles. The biggest problem with fibreglass components is airbubbles as a result of incorrect application of the first layer of glass against the
gelcoat. The very first layer of glass on a mold or product is the most important in respect to strength and appearance. If there are any airbubbles in the first layer, you
will get those dreaded air bubbles. Normally the first layer on a less complex shape would be a 225 gram split strand matt. Anything thicker, or the use of woven cloth will
result in weave print through.
Tissue being applied with a brush. You can see how well the tissue fits into the sharp corners. Ordinary weight cloth would have no hope.
Both bezels complete. This took me about 30mins, including cleanup. You can clearly see how well the tissue works on these sharp corners
If you look closely, you may be able to see where I filled the holes with gelcoat to make layup easier