Author Topic: Boat building  (Read 27463 times)

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Offline tim_unerman

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Re: Boat building
« Reply #15 on: May 25, 2008, 11:11:23 AM »
Just to explain a bit more, prepreg is when the fibre /cloth has a set amount of resin put on it by a manufacture. This is then cooled to either room temp or more sometime 0 degrees thus you have a shelve life of how long till you have to used by. The prepreg is then placed on the mould as you would with any other material then you have to vacuum bag and heat up for up to 10 hrs. The temperature is from as low as 60 degree upto over 200.  So main advantage:
1) low resin content
2) constant resin distribution
But the disadvantages:
1) You can have distortion in the panel due to differences in thermal expansion between resin and fibre
2) You need an oven to cure it
3) Can be more expensive to buy see note later
4) Depending on the type you may need a freezer

So in general use of prepregs to build the main hull shell can be difficult and expensive, but for flat areas such as bulkheads it can be a good option as reaching 60-70 degrees with building insulation and fan heaters is quite easy.

Cost of prepregs: in general the cost of prepregs is more than for the separate resin  / fibre but you can get hold of either out of date prepreg which when you are talking aerospace stuff is still usable for up to a year after or out of spec stuff, this can be slightly high on resin but still good for cherub building. cost wise i know people who bought 200 gsm uni carbon for less than £8/sqm which when you compare it to £15+ for just dry cloth.