I am having some issues with one particular brand of PU foam at the moment. After glassing the boards with epoxy the foam shrunk. I’ve only had about five of them and three have had this issue. Never had this problem with the PU blank manufacturer I normally use. Is there something funny with the foam that is reacting to the epoxy?
Deanbo
Where has the foam shrunk and how much? Were the blanks all the same size , density and from the same batch ? How long after manufacture did the shrinkage occur ? Did they all shrink at the same time ? Did they all shrink in the same place ? Who is the blank manufacturer ?
I doubt it has anything to do with the epoxy.
So many questions
Maybe you can post some photos of these boards so we can see the shrinkage
Cheers
Mooneemick
All the boards in question have shrinkage on each side of the tail and one has shrinkage around the middle of the bottom where the foam has receded around the stringer. Each board was done one after the other and I first noticed the shrinkage in the first board after about a month.
I thought the sun had got to it and didn’t think about keeping an eye on the rest. Two of the boards have not seen the sun at all however, (one stock board and one cancelled order) and have now shrunk anyway. But there was certainly no shrinkage when I sanded each board and it takes me about two weeks to get to that stage so shrinkage happened some time after that.
South Coast Foam was the manufacturer but I haven’t really been in touch with them over the matter yet. Most people who make PU blanks wouldn’t have a bloody clue when it comes to using epoxy on polyurethane anyway so I’m pretty sure I’m going to have the finger pointed at me for using epoxy on PU to begin with, even though I’ve had have no issues with using epoxy on Bennetts!
Now that I’m using South Coast all of a sudden these issues show up. I know ResinX can have issues with PU blanks from certain manufacturers which makes me wonder if epoxy can be the same. I’ve spoken to other people about South Coast and they reckon they’ve had no problems but they all use polyester resin, not epoxy.
Most epoxy guys don’t use PU at all so they don’t have a clue on this one either. Hopefully some chemists out there can jump on here and confirm if my suspicions are right or wrong. Just strikes me as strange when I’ve got people telling me they’ve had no issues with South Coast and here I am with blanks that I have purchased separately over the space of several months all shrinking now.
Kind of rules out a bad batch wouldn’t you say?
**HEY DEAN **
** HERE IS MY E MAIL SEND ME SOME PICS& SOME DETAIL I WILL MAKE SOME ENQUIRES FOR YOU**
** huieshapes@bigpond.com
**
Well I managed to get one photo off before the camera died. There is more shrinkage on top and bottom of the tail but I will have to wait until I get some batteries before I can take some more pics. I have shrinkage on two other South Coast blanks as well and I’ve only had five of their blanks altogether…
If you’re having problems with your PU, maybe some bran will help??
Sorry couldn’t resist!
Kellogs All Bran? Or should I try Special K?
Right, here’s two clearer photos to update this thread. Shrinkage should be fairly obvious on the first photo. Shrinkage is around the stringer on the second photo. The board with the square tail (first photo) hasn’t even been out in the sun. Is this a regular thing with South Coast?
A while back I left a newly ordered, custom polyurethane board laminated with epoxy resin in my car for a couple hours and the same thing happened. I know my board was baking in there and the hot car probably created a low air pressure vacuum or some shit, but I couldn’t help but be reminded by it when I read your post. The foam was literally shrunk–especially around the rails and stringer. This is weird. If it’s not a defective blank, I hope someone can share some science with us.
I feel your pain! After the Clark Closure we had plenty of blank companies producing shrinking foam. It’s not from the Epoxy they would have shrank if they were glassed in Polyester.
Stay with the proven manufacturers. Experimenting is costly! South Coast owes you a refund for the blank your labor and the glass job! Play you pay. Sucks!
Sucks alright. I’ve only had about five blanks from them in total and there’s now issues with a third one I got from them.
Dean
It looks like you have a good case for replacement blanks. Do you deal with South Coast directly ?
If not you should give Carl McCarthy a call 0755221600 at South Coast Foam or email him with regards to your issues carlm@southcoastfoam.com.au I’ve found them good to deal with and have had no problems with their foam but recently I did have foam shrinkage in the nose area of two 6’9" fish blanks from Bennetts .
Good luck and let us know how you get on.
Dean,
The shrinkage of PU blanks that I’ve been exposed to, has been due to the use of WATER as the ‘‘blowing agent.’’ Too much of it, while allowing a very light weight blank to be produced, will impart a reduced structural integrety. Collapse of the cell structure can occur in as little as a few days, months, or even years later. While some may be good, more is not necessarily better. Seen it many time with Clark Foam, during the rush to lighter and lighter blanks, in the early 70’s. Allowing an uncut blank to ‘‘age’’ for a period of time, before glueing, may allow the blank to stablize, and not exhibit later catastrophic shrinkage.
Thanks Bill. I’ve heard of blanks collapsing due to having been blown too light but never knew why it could happen, so I think you’ve nailed the root of my issue.
Bill’s exactly right. If the pressure inside the blanhs cells are not given a chance to equalize with atmospheric pressure BEFORE the laminate, then this will cause shrinkage. Aging for just a couple days should achieve this.
It took several days at least before I got to glassing each and every one of those boards. Thanks for the warning though.
Dean, can you get surfblanks? My fish is over 2 years old, and the deck is just about flat still. It has a 66 deck, but still, it still in top shape, even though i often whack me knee/head/elbow into it.
My kids play with a cut up shaped blank. They leave it out in the rain. I can ( all 85-90kg of me ) walk on it, and even if i put my weight all on one leg, it still doesnt wanna dent. I have to jump on it to get a small indent.
Just a thought.
Thanks Beerfan.
Hey Dean,
Its a clear case of dud foam. I have’nt seen as bad since the time I witnessed an honourable major blank manufacturer personally pledge to not only replace the blanks in question and to get to the bottom of the problem, but to re-imburse the shaper for the glass and resin.
That was a long time ago…since then I have had another, less experienced manufacturer personally deny that shrinkage ever happened to his product…that is, whilst holding an otherwise beautiful board…
I hope your man is more like the former. If not, all thats to be salvaged is that those boards did’nt get into the public hands?
Josh
I have used surfblanks PU foam with epoxy quite often. Never had any problems.
Entity uses them as well with poly and epoxy
Midget has been creating top quality PU foam for quite a long time now.
I highly recommend them.
Cheers