Coring questions, getting ready to do the core on the viper

**mrcrsr** · 04-30-2018, 08:27 AM

I'm going to use 1/2" divincel and have some questions. I hear about using core bond and other similar stuff, but then hear about using vinyl ester resin. Isn't core bond polyester based, which would mean that you would have a compatibility issue?? I know you can put vinyl on poly, but not the other way around. So if you ground the hull once the coring is removed, put down a layer of 1708 with vinylester, how could you put core bond over it? Personally I'd rather use epoxy because of being able to control the cure time with hardener used, but if I did what could I use to bond the core?

**XstreamVking** · 04-30-2018, 09:33 AM

http://www.arjaytech.com/index.php/v...le-vinyl-ester This stuff is vinyl based and should be very compatible with the vinyl resin. With epoxy you can use the resin with some fumed silica added to thicken it, or you could use the arjay pre made bonding putty posted above. Use the divinnycell HS-80 density for the Viper's hull....

**FUJIMO** · 04-30-2018, 04:24 PM

What core thickness was the boat built new with? 3/8", or?

**XstreamVking** · 04-30-2018, 04:34 PM

1/2'' balsa set into wet resin and mat.

**nitro_rat** · 04-30-2018, 05:49 PM

Haven’t I read about several issues with vinyl failing to cure adequately when used to bed core? I always thought GP poly/corebond was the magic bullet for core in a ‘Stream...

**XstreamVking** · 04-30-2018, 08:08 PM

That is only when it is used in very thin applications. I have made my own bedding compound with reichold 100 vinylester resin and had no problems. This vinylester stuff from adtech is made to be a bedding compound and can be activated as low as .5%

**mrcrsr** · 05-01-2018, 07:26 AM

I'm learning towards just using epoxy, I can't stand the smell anymore of the poly/vinyl, let alone being able to Taylor the cure time with epoxy. Is there any downside to using epoxy?

**XstreamVking** · 05-01-2018, 07:43 AM

Little more expensive, but that is the only bad thing I can see....It is very strong and more flexible, resists cracking better. Just remember that once you put down epoxy, no other resin but epoxy will stick to it. There has been some success with poly gellcote sticking good on sanded, fully cured epoxy. Primers and paints will also stick to cured, sanded epoxy. Mas epoxy seems to be a good and slightly less expensive brand. I would steer clear of west marine because of price. Do some shopping and you will see a big difference in retailers pricing.

**Radiant** · 05-01-2018, 08:32 AM

Raka epoxy is my favorite. Very reasonably priced and it is the thinnest I have found

**mrcrsr** · 05-01-2018, 08:35 AM

I get mas from our wholesale fiberglass supply shop, so it isn't bad. As far as the divincel, do I need to use the one with the cuts in it or can I use the regular divincel and just drill a bunch of holes in it so the resin can come through?

**rjdubiel** · 05-01-2018, 08:38 AM

When using corebond you must use GP poly resin for it to kick. Once you get the corebond down and it cures that you can use vinylester all you want. Do some searching on here, Riverman detailed lots of his rebuild of his viper from start to finish. He even used vinylester resin with his corebond first try and it did not kick and he had to scrape it all out and start over I remember reading. He posted links to the corebond directions as well in many posts.

**mrcrsr** · 05-01-2018, 09:03 AM

If I do the epoxy route I'll stay epoxy as mentioned above and mix it with silica to make the bonding slurry. So basically get the old core out, grind it, layer of 1708 with Matt side facing down to the hull. Then the epoxy/silica, divincel over that, then another layer of 1708 over that matt side facing down. Please correct me if I'm wrong with this.

**W2F a V-King** · 05-01-2018, 09:05 AM

I used epoxy and 1/2"- Divinycell H-80 scored and scrim backed on my V-King restore, and made my bedding compound from the epoxy mixed with cabosil. Also drilled the holes you mentioned to allow excess bedding compound to come up, and it did come up in places. Hand laid it all, no bagging.

Best price when I bought mine was ... http://www.lbifiberglass.com/CORING/coring.html

I used a medium 3:1 epoxy and 1708. Worked very well. Got mine from US Composites. Good prices and fast shipping. There in Florida too. West Palm Beach...

http://www.uscomposites.com/epoxy.html

**W2F a V-King** · 05-01-2018, 09:07 AM

Originally Posted by mrcrsr

If I do the epoxy route I'll stay epoxy as mentioned above and mix it with silica to make the bonding slurry. So basically get the old core out, grind it, layer of 1708 with Matt side facing down to the hull. Then the epoxy/silica, divincel over that, then another layer of 1708 over that matt side facing down. Please correct me if I'm wrong with this.

That's exactly how I did mine.