woodenfeather Posted March 7, 2012 Report Share Posted March 7, 2012 Hi Guys, First time posting in the soft plastics forum, although I've enjoyed the reading in here for years. Thank you very much! Anyway, I was recently given some SMOOTH-ON MoldStar 30 rtv and I'm iching to try my hand at mold making. This rubber in pretty stiff compared to some I've seen and I was wondering how much under cutting I can get away with? When I say under cutting I mean shapes that would prevent a rigid material from demolding, like a slanted paddletail on a swimbait. I have a design I'm thinking about with a portion of the head (swimbait) that slopes down and into the mold. I also want it to be articulated with the connecting "hinges" to be relatively thin but the side profile to be about 1" at the belly. Do you guys think I would have problems getting this shape out of a single cavity hand pour mold? I just want to know what limitations I need to consider while I'm dreaming stuff up? Thanks for any advice! Dan Quote Link to comment Share on other sites More sharing options...
wchilton Posted March 7, 2012 Report Share Posted March 7, 2012 I've made several silicone molds and you can get away with a lot. The silicone is so stretchy you can remove rigid originals that have some undercut and removing soft plastics is even easier because they stretch. I made one little "shad" shaped paddle tail where the paddle is at least twice the width at the bottom as at the top. Baits don't fall out of the mold but a little pull/stretch and the tail pops right out. The thing I would advise being careful about is getting good adhesion of the top of your "master" to the bottom of the mold form. I use a sort of rubbery two-sided tape on the whole top surface. This prevents silicone from getting under the master and gives you a nice, clean edge on the mold. I've also gone around a master with a thin sealant of some type (thin epoxy or casting resin) and that gives a really clean edge to your mold. Quote Link to comment Share on other sites More sharing options...
quietfly Posted March 7, 2012 Report Share Posted March 7, 2012 I've used SMOOTH-ON MoldStar 30 with no problems at all.. Quote Link to comment Share on other sites More sharing options...
woodenfeather Posted March 7, 2012 Author Report Share Posted March 7, 2012 Guys thanks alot for the replies. hopefully I will have something worth sharing in the near future. Thanks again, Dan Quote Link to comment Share on other sites More sharing options...
HJS Posted March 9, 2012 Report Share Posted March 9, 2012 Jeez... I make molds from Durham Water Puddy (almost like PoP) that dries as hard as a rock. Many of them have at least a little bit of undercut (going past the center line). I have no problem extracting soft plastics that I just poured. On the other hand, I also make molds for lead jigheads. With those you'd better be right on the money with the center line or the jig will be locked in place. Soft Plastics are very forgiving. Quote Link to comment Share on other sites More sharing options...
