Good afternoon to all,

I am building a female mold that will beused to make a carbon fibre marathon canoe (18’6”). I have good skills working with fibreglass but this is my first experience in making a femalemold.

The mold is based on wooden slats lined with 1” foam and  lined once more with fibreglass. The fibreglass  is then finished with the usual body fillerand mold primer/hi-gloss coats to make it a glass finish. As you may realise,the front and back end of the molds are extremely streamlined and I find itimpossible to sand down to a glass finish.

The alternatives that I have come up withwould be to 1) cut the mold in half and work on each side separately thenreassemble to lay the carbon fibre cloth. The disadvantage might be that Iwould not end up with symmetrical sides. Option 2 would be to lay the carbon fibrein the mold as is but finish the exterior of the canoe’s ends to a glass finishafterwards. Finishing the outside to a glass finish after unmolding seemsdifficult to achieve. Any comment and recommendation would be welcome. 

Manythanks.

Z

I have used expanding foam inside hollow CF gun-stocks .. it made no apparent difference in the stiffness of these, but it removes the "hollow" sounds, so makes the user feel a bit better ..

I suppose that in the case of a flat blade, it can help protect a bit against crushing the thinner parts of the hollow blade.

Always make sure that you leave at least one opening for the expanding foam to escape from --- the foam can create a very high pressure if the gasses can not escape.

And DO keep it in the mould ... the foam could easily deform the part, if its not supported.  What kind of mould have you made?

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