'90 SJ Squarenose hull finish ??

[Rotor-Rooter]

OK, I have done the searches & still have some ?? on the SMC Yamaha used to build this ski. Polyester gel coat won't stick due to the SMC, but what will? Normally, I'd say do an epoxy primer/paint, but this thing is going to be hitting the shore - a lot. I like the durability of polyester gel coat, so is there a bonding coat I can put over the SMC that can be used to promote adhesion of the gel coat? Will vinyl ester stick to the SMC? You can shoot gel coat onto vinyl ester, but I don't want to experiment with unknowns. If the vinyl ester won't stick to the SMC, I'm probably back to epoxy paint or Imron.

First of many ?? to come on this total rework... and thanks for the help.

[WFO Speedracer]

man you would be looking at a massive undertaking even if it would work and it won't.with gelcoat the painting is the easy part its the sanding and polishing thats a biotchhh.just go with the epoxy primer and ppg deltron polyurathane very tough and very fixable if you do screw it up.

[Rotor-Rooter]

I agree for the most part, but I've gel coated enough runabouts that I'm not afeard of a little 'ol Super Jet! Use a little extra styrene on the last coat & finish it off with a good coat of PVA and you don't really end up with that much more work. This hull is pretty chipped up on the bottom, in fact I've been questioning whether to use this one at all. It's going to take a heavy filler coat of something. I thought of using vinyl ester with glass spheres as a filler/bonding layer and then gel coat, but the SMC concerns me.

I fell in love with Deltron years ago. My favorite thing to spray. Problem is, gel coat is tons easier to repair chips & nicks, IMO.

Thanks for the post.

[The Penguin]

and gelcoat is much more durable - right?

[Rotor-Rooter]

Well, I spoke at length with US Composites and Fiberglast today about this issue, and I'm not encouraged :banghead:

It seems you might be able to spray polyester over vinyl ester, but vinyl ester is questionable over SMC. You can spread epoxy surfacing compound over the SMC, but neither of the former 2 can go over epoxy. The techs at both companies were unable to come up with a solution that would get me to the gelcoat - and I sooo wanted to do this.:boggled:

Looks like a trip to the paint store for epoxy primer & Imron. Goodbye to my gel coat ambitions :sadwavey: SMC sucks:headache:

[WFO Speedracer]

Well Why Cant You Use Epoxy Fairing Compound On The Whole Bottom And Gelcoat Over That?for Sure The Fairing Compound Will Stick To The Smc And The Gelcoat Will Definatly Stick To The Fairing Compound

[Rotor-Rooter]

That's pretty close to one option I questioned both companies about. Both told me I shouldn't use a polyester resin over an epoxy resin. I've only got experience with spraying polyester over polyester, so I'm in unfamiliar waters here... USC told me it's OK to spray polyester over vinyl ester - but weren't sure about vinyl ester over SMC. FiberGlast told me epoxy resin (surfacing or fairing) was the only mat'l to use on SMC & that polyester & vinyl ester wouldn't adhere well to epoxy & that only epoxy-compatible paint should be used. :boggled:

[Rotor-Rooter]

And thanks for hanging in there...

[surfjetlouie]

I have used basic white gel coaton the bottom of "sfl" Kawasaki X2 about 2 yrs ago and I beleive it is still there in good shape. also styreen mixed at 10 to 15 % will do best for spray.

[WFO Speedracer]

When I worked at the ski nautique dealership all the repairs were done with west system epoxy resin with gelcoat sprayed over the top of it and also my thunderjet f15 is gelcoated and that is an epoxy glass resin hull,I really dont see the problem here

[Rotor-Rooter]

Real world experiences are good to hear. Sometimes manufacturers are a little too over-cautious.