Had exactly the same shrinkage on a Polyurethane TDI blank glassed with Poly. I didn't know what to think of it at the time. The blank was glassed in a Pro glass shop. I had several of the same blanks that I also shaped and had glassed by the same glasser. Only one shrunk.
Company was South Coast. Latest blank from them is several months old and no problems. Same blank manufacturer, same resin for glassing (RR) but the issue has disappeared. Did yellow a bit though.
Hey Guys
I glassed a reshaped PU windsurfer with kinetics about 18 months ago then sold it to a friend down the road.
Board is holding up well but it has yellowed quite a bit. almost a brown sugar color.
Might have something to do with the way he stores it though.
Every time I drive pass his house, I see it laying next to his garage which would probably get 6 - 8 hours sun a day.
Might have a lot to do with it.
Cheers
I think I know the colour you mean. I used Kinetix on polyurethane foam and then left the board on the roof of my car with no board bag for a couple of weeks. You could see where the strap marks were quite clearly. Rumour!!
Epoxy on urethane needs a UV absorber. The shrinkage does come from UV and from some other sources … heat being one. The yellowing of the foam is solved using this UV absorber as well. We used to sell the UV absorber separate but not everyone used it. I believe that back in 05 we suggested that anyone using epoxy on urethane needed to add UV absorber but that may not have been on every post. When we came out with CE we decided to include that because then the resin could be used on either one without additives. This is a better solution and it is even advantageous to EPS to have it. Sorry I didn’t bring that up earlier … 05 was a while ago and I’m getting old.
Did you use UV absorber with these?
Thanks dog. Ask Seabase. If the resin is clear that’s 2000 and IMO they should begin to bring in CE or KK. Pretty sure Seabase has gotten samples of all we make but I’ll check from my end too.
MD … they really want to know how you guys do it … don’t tell em. Make em work as hard as you have, that way they’ll respect you in the morning.
no UV absorber additive - didnt know anything about it....seems like something that should be in the resin without having to add it if it was necessary. Apparently it is now with the CE......
We didn’t sell much epoxy for urethane back then because of Clark’s anti epoxy poison pen letters in the 80’s so we didn’t include it until CE. EPS doesn’t really need it. We have sold that as an additive for 25 years for urethane foam and other UV sensitive substrates. Sorry you missed that … I did mention it on here often. This is probably why you got shrink and we didn’t. Yellowing as well. But like I said we did see some shrink in the lighter weights even with UV absorber.
Here’s a link to our web page about UV absorber:
From Jan. 2 2005. Not the only time it was mentioned either. Third post on the page.
I thought the kinetics had a UV absorber in it already.
Looked through there website and it says UV resistant.
Will have a look on the packaging when I get home.
Cheers
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There’s UV resistant, which means it isn’t effected by UV drastically
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There’s UV stabilized which means it’s got UV stabilizers in the resin to protect the resin from UV
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There’s UV absorbers which protect what’s under the resin.
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There’s optical brightners which make the resin look brighter.
2000 is #1 so it doesn’t need #2 and is fine on EPS which doesn’t need #3.
CE and KK are #1, #3 and #4. Doesn’t need #2 because its #1 and has #3 for urethane foam cores and #4 to look brighter.
Probably doesn’t have that.
What is RR CE? On the site I see Kwik Kick, Project 21, and Composite Pro. Where is CE listed? Thanks
Hi Greg,
are you still selling the UV absorber separate and is it the same blue dye(?) that you put in CE? Ordinary white pigment does not seem to tint epoxy that smoothly.
I have an old Clark foam longboard that I broke at Sand Dollar Beach during one of the Big Sur campouts. I glassed it with Resin Research and glossed it with polyester resin.
It has been outside the ENTIRE time since (several years) with a good amount of direct sun exposure EVERY day. No shrinkage or excessive yellowing has been noted. In fact, I would say it's less yellow than a standard polyurethane/polyester board would be after similar treatment. Some of you have seen it.
The foam was not the lightest of the Clark densities... I think it was supergreen - the heaviest of their stock densities.
I did use real gloss resin which is supposed to have UV inhibitors in it. This was also before Greg Loehr offered the UV inhibitor resin that is now available.
PS - Several years ago I posted the link to an epoxy resin test but none of the current crop of surfboard epoxies were included in the test.
CE is a package newly available in all the RR formulations. The package contains an optical brightener and UV stabilizer/absorber. UV absorber is available separately listed on the Additives and Modifiers page but not on the price list page. Read RR comments about the CE package in the script desription of the Project 21 formulation. All from the www.resinresearch.net site.
The gloss resin did the trick. Thanks John. BTW if your going to gloss with poly use the good ole Riechold polyester gloss resin. It stays stuck wayyyy better.
I was under the impression 2000 was surfboard specific. This is why I asked if you would be deleting this line from being sold. I guess 2000 is not just sold to just surfboard manufacturers/suppliers. No offence by the way, I was just under the impression 2000 was just for surfboards. I’m still under the impression that 2000 over polyurethane still yellows slower than polyester over polyurethane but the masses seem to disagree.