makin moulds

[probert_nova]

i spent the day copyin my m8s sideskirts with fibreglass and
theyv come out alright. just wonderin if anyone knows a website that tells ya how to make moulds coz i was thinkin of makin a few up and sellin em.
also any tips anybody has got would be helpfull.
cheers.

[-tucny-]

i assume youve just taken a cast off your mates skirts? to reproduce them just follow the same process again- clean, wax, gel coat, resin + matting. if you make large objects or objects with complex shapes then you may need to make the mould in parts that can be fastened and unfastened together. if you then make an object using a complex mould then where the joins were in the mould will leave sections that will need sanding on your final cast.

Theres a link to a website that can give you more information on here, may be in the fibreglass speaker pod post in sticky.

[ade]

yeah - as above - for large parts with "undercuts" (the bits that are usually the buggers to remove) you'll need a 2 part mould. Usually for big parts, you make the mould in fibreglass and then reinforce it to stop it bending (using wooden struts).

For a bumper, so you can do the arch area properly (theres usually a lip that wraps round the front wings), put a dividing line in the middle of the bumper. When making the mould, use a piece of wood cut to the exact profile of the bumper so the fibreglass can butt up against it and form a lip about 6" big. You need to smooith this so it perfectly jins to the bumper. The idea being that when you remove the wood and then do the other side of the mould (remembering to wax the mould lip), you can bolt the 2 sections together getting a perfect join - limiting the amount of sanding. Remember to wax the "master" (item being copied).

see pic below -

http://img.photobucket.com/albums/v13/danga/mould.jpg

The grey line is highly exagerated obviously and indicated the wax - it would be about a hairs width in reality - All you do is bolt the 2 moulds together (they should be perfect fit ), wax, paint on gel coat (best to spray it for perfect even finish as gel coat can crack if too thin and shatter if too thick). Allow gelcoat to harden for a couple of hours (as per manuufacturers instructions) and then lay up fine tissue fibreglass cloth, followed by woven roven fibreglass (which isnt cheap but is the best for reinforcing bumpers) - then a layer of standard csm fibreglass, then tissue fibreglass for a smooth finish and allow to set. Allow a small amount of cure time between layers and dont slap it all on at once - the heat generated will warp the mould. Also - make sure the resin is fully worked into the fibre using a rolling tool or stippling motion with a suitable brush. Once it starts to cure, truim away the overhangs of fibreglass.

After 24 hours unbolt the mold and remove carefully. Smooth the join line in the middle and sand back the edges for a proper finish.

Make sure you wear a proper air filter spray mask - fibreglass is nasty sytuff and if inhaled can cause cancer/bronchial infection (it sticks in the lungs and makes them bleed) - its glass at the end of the day.

Ade
:wink: