Does sealing a polyurethane blank make the lamination stronger.
I know you don’t have to seal a polyurethane blank but would doing so make for a stronger lamination.
I think some polurethane surfboards delaminate alot easier than others.
Gene Cooper seals his tow weights before lam, I seal EPS with an epoxy mix, but on poly I want the glass fibers right against the foam with as much contact as possible. Over the years I’ve found laminations with a heavy boundry layer of resin are more prone to showing shattering, not of the glass, but the resin breaking down, a tight drier lam will dent before shattering
If you do a thorough, clean seal job, on any foam, you can get a tighter lamination…which equals a stronger board.
Of the hundreds I did, the sealed laminations all dinged less and held up better.
An added bonus is the weight is then restricted more to the skin, so without heavy resin soaking into foam the boards performed noticeably better. I could easily feel this just flipping the boards while sanding.
Do your own thing…it’s your board.
So what would you seal a polyurethane board with if you were to seal it. Is spackle okay.
Also if you wanted to do a paint art job under the glass, can you just paint the polyurethane foam and then laminate over the paint? Can you paint the foam and laminate over it?
I prefer and recommend using resin slurry, but others have used water based spackle. (I use a mix of qcell or micro balloons, and a little cabosil makes it really smooth)
Paint over that just like you normally would. Good crisp tape lines compared to foam.
And if you’ve never laminated a sealed foam before you will love it…no draining, tight, accurate…
wildy, How thin is your mixure? and do you sand the sealer after it cures?
I spend this last year to work on EPS foam sealling in a lab test way. I was first sceptic about how sealling can improve durability. I m not know, some way can be a real bonus, but with some weight added. So for “strengh” let spackle down, even more with pu foam, go with blush free époxy resin, at least for this step. Let it full cure and key it well before lam
If working with polyester, I’m wondering if the following would work:
Brush a thin layer of UV catalysed polyester over the foam and let it gel in UV light.
Doing this quick enough would seal the blank before the resin has the time to soak deep into the foam.
Then start the lamination on the still tacky seal coat for an optimal chemical bond.
I haven’t tried this. I’m just wondering if this would be a good idea. As I believe it would make a great bond to the foam without any visual effect.
Opinions?
Polyester can’t give a “good bond” because of it’s low elongation to break, but in fact it’s not a real problem because it’s not bonding resin that break but foam near of it. Let some resin penetrate to reinforced foam is effective but it add weight and if you do it during lam can ended in a dry lam. So it’s a good idea to do it as a first coat. To be effective resin need to penetrate in foam so open pore foam, low fluidity low speed set resin. Weight increase can’t be reduce by using less fiber for skin because thinner skin will increase shear stress in foam end final product will not be “stronger”. The eps/epoxy builder know it well, if you do a good laminate (not too dry, with not extra fast resin) without sealing foam board weight more but be “stronger”.
I always prime coat poly blanks with epoxy&Qcell …the blanks are light Surfblanks pink foam , and its surprising how much the foam sucks it in , and how hard the skin becomes in a day…and even harder in a week…so yes , it does increase impact strength considerably…it needs to be an epoxy that’s compatible with poly resin , or better still go full epoxy.
Why don’t you seal with polyester if you’re going to glass with polyester? A polyester over epoxy is alway a bad binding even if the epoxy is “polyester compatible” because it’s meant the other way round to be compatible (epoxy over polyester)
It’s not too thick or it’s too hard to squeegee. That’s why I use a little cabosil…it makes the slurry smoother and easier to get on and off. Also I used to mask off around the wide point/rail apex to allow a quicker job, but not essential, just makes it neater and easier.
No, no sanding. With poly use laminating resin so it stays tacky…with epoxy it needs to be gelled. And use clear cello tape on your laminating rack…this way any flipping and curing pops off the stands when you are ready to flip. Even after lamination, if done with care, will only leave a couple of small shiny spots, and disappears after hot coat and sand.
Then it’s just a bit of care laying on the fabric. Dry squeegee from the center out sticks the fabric in place.
Glad you are having a go!
Polyester stick well to a prep fully cure époxy.
Kinetics Epoxy from ATL Composites…it’s a surfboard specific epoxy resin , that was developed as a surfboard laminating resin , to be filler coated with standard polyester surfboard resin…it has been proven for many years now to have NO bonding or delaminating issues with polyester…none.
I believe in it. When I seal I use a 10% styrene mix so the sealed blank doesn’t show any resin on the surface when done. When applying work it in with the squeegee then use quite a bit of pressure in the final pass. Very little resin stays in the foam but I think it forms a strong matrix on the surface as opposed having the problems with pooling (cracking) with thicker mixtures. I find less resin is used in the actual lam because you aren’t chasing the soak. My theory is that by doing the extra step you’re controlling how much resin stays in the lam and how much reaches into the foam to create a good bond. I always try to check out old boards of mine when I get a chance and compare sealed vs not sealed and findings seem to support my theories. The only down side I see is the extra work required up front. I also believe that when an lam (unsealed) kicks too slow that a plural space is formed where the bond should be and adds to the chance of a delam. There’s no drainage when a blank is sealed. So at this point I seal for double layers, big wood, any board built to flex, and when using flat weave cloth. I usually don’t seal normal single layers. Also, for tints and opaques I’ve found that using the same color for the seal give the best result as long as the seal isn’t sloppy. Lots of theory there, take it for what it’s worth.
…long time ago when there was not any premium fiberglass (chrome washes, etc), plus heavy weights like 7.5oz, et al and too “bread” type of PU foam, apply the resin before was a norm to solve problems.
But in the last 25 years, the foam is better (Aussie foam) and the fiberglass used in surfboards are premium and weight less (4oz, 6oz like a heavy one)
You really do not need any sealing to have a better bond between the fiberglass and PU.
If you have delamination, is due to an overshaped blank; more if the density is a light one and a BAD lamination (I see gobs of marketed brands with poor lamination and yes, ALL made in California, Hawaii, Thailand or Indonesia. Yes, is due to foam; an overshaped PU cannot hold the abuse of a radical rider. But in most cases you do not see too much of delaminations; even with 4oz.
Applying more resin to fine materials is a waste of time and brittle time and if you make HP surfboards is a no no.
The resin ratio should keep at the minimum possible; those stress marks in the longboards are there due to the brittle gloss resin (in big part of the world there s no any gloss resin so you need to do the gloss coats with lam resin and the results are that there s no stress marks)
Those stress marks behind the fins in the hot dog boards, etc is that the glasser applied too much hot coat resin, then more gloss coat resin; bad lamination man.
I have severe use in some small hot dog boards with the deck pretty beat up but without delamination.
I see some small delaminations in boards were the owners did not care and had water intrusion for months, even years.
The resin itself is nothing more like a glue.
hey kayu are you still keying the surface when doing a poly fill over kinetix ?
Gene wrote:
I seal…when using flat weave cloth.
Why do you seal for flat weave?
Stoney, one could or would seal a flat weave cloth if he felt that it would help the cloth saturate more evenly, for all intertices are not created equal.
Flat weave is really tight so I think less resin fills in as it cures, especially with double flat weave. For me it’s all about that point of contact between the foam and cloth and how sealing can enhance the bond.