Indeed Josh, I have admired your handiwork from your early days with FW. The pictures you’ve posted on Sway’s of the concave decks still inspire me. I’ve not had the opportunity to properly thank you for sharing your expertise so freely. Thank you, sir.
durbs, I’m still using an EPS core, so I bagged the corecell to the core with 2 oz eglass and RR epoxy. I do most everything with epoxy now, even when I can get away with Polyester. I’d like to fiddle with some Vinylester if I ever do a Dcell skimmer.
Aww shucks surfdad…
But, “sir” is a bit much!
Anyway, your pourfoam rail (and Johns link to the velo spoon-guy,) got me thinks, so…tit for tat mister!
Josh
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I am in the process of making two more molds and thought I would share my process. As I mentioned earlier, I save the offcuts to make the buck. I roughly draw the outline and then use a jigsaw to cut generously on the outside. If the mold will be for a hand shaped blank, I only allow about 1/4", if the blank will be for a CNC, I allow 1" extra. I then lightly glue the offcuts down to a piece of plywood to keep it in place as I make the mold.
Next I liberally apply mold release to the foam and plywood.
I use TAP Latex mold builder and paint 2" around the base, to as as a flange, and then the entire surace of both offcuts. It will take several layers - typically 20 or so to get a good solid mold surface. This is what it looks like at this point, including the TAP product.
When I am done, this is what it will look like. CSM reinforcement, soft latex mold and in the background a completed part.
A picture of one of the finished parts. When I am hand shaping the blanks, I try to keep the shaping of the polyu pour foam to a minimum, so I hotwire the rocker before creating the mold.
Hey Surfdad,
I’ve done some molding before, making molds in both silicone and Latex. I found the shrinkage factor of Latex to be restrictive, affecting accuracy of the cast object, and silicone to be expensive.
I have an idea for using pourfoam for another application, and I wonder:-
This Molding latex as in your picture…does it shrink?
Josh
Hey Speedneedle,
I haven’t noticed any shrinkage on my latex molds. They are all over 5’ in length and I have to wrestle them back into the rigid supports. Also, with the pour foam, it expands so much, that IF there was shrinkage, the expansion would no doubt push the latex back out to the rigid support.
In terms of cost, the gallon pictured above set me back $40. I’ve made 14 parts out of one mold and it’s still in place, but I feel like I’m living on borrowed time with it! The other real disadvantage of this stuff is that building the mold takes ages. I seem to only be able to manage 3 coats of latex a day, so it can take me a full week just to brush the latex on.
