moulding clam shell deflectors

[catalac08]

I need some grp clam shell type covers for the through hull fittings between my cat's hulls and I wish to make about half a dozen from grp or plastic.

One option is to make a mould from grp using a repaired, faired and polished one I have taken off. A fair bit of fiddly work but then should not be too hard to laminate som new ones with gelcoat and matting etc. Another way to make the mould would be to cast one mould from the faired vent using casting resin, and then again and again until I have a block of say 6 moulds. Another thought again is to heat a sheet of thin perspex/plastic and make a mould in this way. Yet another idea would be to make the vents themselves from heat mouldable plastic, heating and using the repaired vent as a former to heat sag plastic sheet onto.

The size I want is not available from chandlers and even if they were the cumulative cost i would rather avoid. - any thoughts on the best way of me making these clam vents.

 

[VicS]

You have answered your own question I think! If you use plastic to make a mould then be sure you use a plastic that is not affected by the resin you then use to make the final articles.

Personally I would make a mould with glass mat and resin from a polished original. You should be able to get the mould release agent from glass fibre suppliers.

Polystyrene sheet is a material commonly used for making heat moulded or vacuum formed articles. Glass mat and resin will I think make a stronger job, as you can lay it up as thick as you want

 

[Talbot]

IIRC, these were originally made as 1 mould for two pieces, with the resultant product being cut in half to get the correct shape and finish.

Alternatively John Lack might still have some in his shed.

 

[Mudplugger]

P38/Plaster of paris?

 

[William_H]

Have you considered making the deflectors out of sheet copper.
The advantage being you don't need to antifoul the deflectors.
As suggested make a dome shape out of wood and another female shape also of wood. Press together to make a stretched dome which when cut in half makes two deflectors. olewill

 

[Matrosen]

Have you seen the price of copper lately? Cheaper to buy ready mades. /forums/images/graemlins/smile.gif