Are there any core materials suitable for use during mold production to to provide bulk/rigidity with wet lay process? Are they compatible with epoxy or VE?
It would be great to make molds a bit quicker and need fewer layers of glass to get the same rigidity.
balsa, soric,
PVC foam, plain sheet or contour.
thanks guys, do any of these cores soak up lots resin?
Soric sucks up resin.
balsa sucks up quite some resin too. soric has different versions. cork is a possibility too ,I suppose, but takes up some more resin than foam too. very easy to work with, on the other hand.
I use 16 lb A/B pour foam for many of my molds for structure, it is superior in strength and can be added to the back side of the mold after the initial layup. You will still want to build up a frame off the back of the mold during the later stages of initial layup, the foam can be added later. Many may feel 16 lb is excessive, you can use a lighter foam. The 16 lb foam is basically the density of wood when it cures and it can be poured as thick as you like.
Interested in the 16lb PU as backing. Got any pics or link to the brand you use ?
Thanks
Tim
Some of the RC guys have started using homemade Corian (the table top material) out of epoxy and Aluminum Trihydrate. They actually don’t use any glass at all with this method. Just gelcoat and then pour the Corian in. Of course, some mold shaped lend themselves to this method much better than others.
[b]https://www.youtube.com/watch?v=jfImUJJm3yc&app=desktop
http://www.rcgroups.com/forums/showthread.php?t=2165394&pp=50
[/b]
I’ve also seen people mix resin with a lot of chopped strand fiber (not the matte, but just finely chopped loose fibers) to make a paste that you can then spread onto the mold to beef it up.
[oops, what a goof - I just saw the poster before me was Tim who is the guy posting about the Corian method in the rcg link… I guess, you have been over the Corian subject here as well at some point]
All good gecko. No haven’t done anything on the DIY corian on here. Thanks for posting 
IllStreet stocks the various densities of expanding foams. The higher density foams will have less expansion and be more rigid, the 16lb pour foam has a great balance of strength, yet it can still be sanded and shaped. the 16 lb is comparable to a soft wood in density, easy to mix 50/50 and it sets up fast.
You can also use a combination of milled glass or chopped strand (1/8-1/4"), 3M glass micro balloons, and polyester resin to make a thick filler similar to fairing compound, add aerosil to get the desired thickness. I found the glass micro balloons make a great putty for mold backing and reinforcement, it can also be sanded fairly easily.
The core material I would consider would also need to withstand post cures of ~250F
I tend to do a thin skin, then a couple of layers of 450 or 600 csm, then get stuck in with a heavily ATH loaded resin and csm just to add mass to it.
unless its a really big mould I tend to avoid core. not that im against it, just don’t see the need most of the time.
I sometimes use cardboard tubes cut in half and lay glass over that, or rigid foam cut into strips, anything to give added dimensional change and thus more rigidity.
that video of the guy using epoxy slurry is good though, how much resin would that take…? I’ve used epoxy with aluminim filler and those work great. If you’re gonna go down that route and you’re only making a few dozen parts, you can also use plastic faced plaster molds which are much much much cheaper than pouring all that resin. You wouldn’t even know it was plaster if you build it right, until you pick it up. It’s good for small molds.