rotccapt

hi all i am about to jump head first into my first mold as to date i have made 3 one off lost foam simple cowlings now i am going to be making a fiberglass half cowl for my 1/7 scale mustang. i have done lots of research and have the just of what i need to do. my question is if i make my mold out of polyester and my parts out of epoxy will i have any problems? this will not be a production mold just enough to make a couple cowls

Ron S

My Feedback: (2)

You should not have any problems. I make my molds out of polyester resin to keep the cost down, and lay up my parts in the mold with epoxy. Just make sure the new mold is waxed thoroughly - you might even want to add a coat of PVA also, on top of the wax, before laying up the resin/cloth.

Ed Smith

The trouble with polyester molds and parts is that as the layup cures it is susceptible to distortion.

Ed S

SCALECRAFT

My Feedback: (13)

As Ed mentioned along with distortion, the mold will also shrink considerably after a few years. But for your application, you have no problem. To limit distortion problems with polyester resins, make the cure time slow, less of its hardner.

Good idea for saving money if you, or your family can stand the smell.

Steve

TeamSeacats

The only time I had problems with polyester mold distorting, was when I used a cheap polyester resin. Using a good isophthalic polyester resin (about $34-$40 per gallon), will yield good results over time. I've got a mold that is two years old that I just put the plug (epoxy over balsa) back in to make some unrelated repairs...it fit perfectly.

However, I agree with the others - you will not experience warpage or shrinkage with the epoxy based molds.

Magne

If your plug is of the "hard" type, then I would recommend storing the plug inside the mold, this may prevent distortion of the mold.
Screw the mold flanges together for storage.

Magne