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Has anyone tried making lost foam moulds?


k80rum

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I'm thinking of making a carbon intake scoop for the seven. I had been thinking of making it in aluminium but making a lost foam for c/f doesn't look a great deal more effort.

 

Once I've checked with a cardboard template whether it's worth going ahead with, the actual process seems to be:

 

i) Carve and sand (using a 60/80 grit) a mould from dense styrofoam

ii) coat the foam in epoxy and allow to dry,

iii) impregnate any lay up some fibre (200g 2x2 twill seems a good choice), making sure to squegee out the excess resin and allow to dry

iv) dissolve foam with cellulose thinners

v) paint with epoxy and allow to dry.

 

I was just wondering whether anyone has had a go at this and if they've got any tips? It's not at the level of vacuum-bagging and obviously RiF will be my first port of call for most things, but this seems like an interesting project for a one-off.

 

 

Darren E

 

K80RUM Website and Emerald maps library

 

Superlight R #54

 

 

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I've done it for scale r/c plane fuselages and it's pretty much as you describe. What's worked for me is:

 

Carve/cut the plug from dense foam, I normally use blue foam. I use a template each end of the foam and use a hot wire cutter to get an accurate shape. I then cover/wrap it in packing tape to give the inside surface a smooth finish. Then go over the tape with a release agent so the epoxy doesn't stick, believe it or not I use floor wax! I then use a couple of layers of heavy glass cloth as C/F really doesn't like a wet lay up on complex shapes, best with vac bagging. The cloth I use from memory is a good quality 2x2 twill, plain weave's no good on tight compound curves. To save some sanding time after the resin's set wrap the whole thing in cling film as it dries. Once done, sand, a quick coat of resin to fill any holes from air bubbles and a final sand and polish. It sounds quite rudimentary but has turned out some good results for me. I've got some foam, cloth (I think) and 3 sizes of foam cutters if you get stuck. Petrol also works well to dissolve the foam. Shout if I can help but be prepared for a lot of work, it's no where near as simple/quick as it sounds.

 

VX HPC - Loud and proud here

Watch out, whatever hits the fan will not be distributed evenly

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Thanks Ric, there lots of helpful tips and tricks there. I think I'll follow your lead and try the packing tape and floor wax. I'll also try petrol as the dissolving agent as I've got some sitting in the spare fuel can *smile*. The cling film tip is well worth knowing!

 

I'm keen to give it a try. Since the scoop's not going to be on display, it's probably a good thing to start with.

 

Darren E

 

K80RUM Website and Emerald maps library

 

Superlight R #54

 

 

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