Musings on fixing crushed and/or delam decks

I’ve been doing some thinking on this subject lately.

It’s a bummer when your board’s deck starts caving in or gets the cloth bubbling up, eventually cracks form and water starts to get sucked in, all the while picking up weight hindering performance and prompting eventual death for your stick.

Some people think throwing a little cloth on top of the delam will take care of it…but that is only a band aid solution that seldom works for any real length of time.

Some people slice the bubbled area, carefully lift it up and pour resin or a slurry or resin, Q cell, cabosil and or milled fibers into the void then press down…this really isn’t much of a thermoweld. Years ago I tried drilling holes and injecting slurrys into the delam areas. The results were just okay.

Another popular method is to cut out the infected area, let it dry out, then mix up a batch of Q cell (microballoons) and fill the area up…sand it out and glass it. This sometimes results in adding a lot of weight and definitely changes the balance of the board.

If you have a board that has a lot of the deck pulvarized…and by this I mean the foam under the glass you remove is just smashed and spongy, you have to start thinking what is the best approach if you want this board around for much longer. Sometimes the foam will just flake off because it is so deteriorated. You might have to sand down quite a ways to get to undamaged foam cells.

I repair boards for people (amongst doing new ones), and I have a Yater longboard that someone gave me that is currently in this unenviable position. The guy wants to keep it, and he has charged me with revamping the beast.

So I started thinking about alternatives for doing boards that have half or 3/4’s of the deck destroyed. This board also had a previous delam on the middle of the deck that had been fixed with Q cell and glass over.

So in my ramblings, I started thinking…well, if you use pour foam to replace the destroyed foam the density won’t really be up to par. However if you use pour foam with a skin of PVC or luann, or some thin pretty wood then you can save a helluva lotta weight vs. microspheres and resin. Then I started thinking of other ‘down and dirty’ ways for filling the voids and it took me off to wondering if anyone knows the compressive strength of spackle or vinyl spackle? There is even a very lightweight spackle but it says “not to be used as a skim coat”. Hmmm.

I could try pour foam compressed under, say, luann (you could use sandbags for weight on top of the skin instead of having to get a vaccum bagging setup)…but I don’t have a tremendous amount of confidence in the quality or consistency of pour foam. I could argue with myself that it is just there to help fill the void from the old damaged foam, but if I am going to go that way, why not consider usings EPS instead? That would keep it lighter yet and if I put a skin over the EPS then I can go ahead and close the board up with polyester instead of epoxy. Wait, maybe I wanna use epoxy because of superior strength…uh, maybe I don’t want to use epoxy due to cost or if the guy wants to fix a minor ding later in the area and gets incompatibility…

…oh boy…now I’m making it too complicated!

You could also create vertical stringers for a skin to skin connection…almost like taking he insert of an icecube tray and inserting it into the foam, or grooving the foam with a sawtooth trowel if the foam is hard enough. If you only insert a few vertical supports the glass will undoubtedly crush and crack right next to those supports. Maybe try that route and put some Astrodeck or the equivalent over the finished deck.

Ultimately…it comes down to if you want to just pour a bunch of resin and micros in there, or bondo for that matter (they have lightweight glass reinforced bondo for that matter) and just leave it at that. It can be an obvious repair, or you can paint or pigment over for looks. You could even lam fabic if you want to get fancy, but then you need glass on top of that and the weight goes up…no biggie if ya don’t mind heavy.

…or you could do a nice wood reinforced inset deck with a pinline or whatever. Or you could paint the deck white or something and glass over it.

I’m sure someone will write in and say, what about changing the flex pattern and performance of the board…to which I would reply:

what about the changed performance the board has already undergone by it’s degraded condition?

Wow…guess I made the coffee stronger than usual…DS

Yes weird stuff does work out some times.

The bag cost $15 pump cost under$40.

PU broken boards glued together with EPS-balsa deck patch.It made a nice looking neat fish.

Have fun,

Dang Deadshaper, that really must have been strong coffee!

I actually just finished resurrecting (I did not say restoring) a Yater too. It was a real basket case - in 3 pieces, all the glass & some of the foam missing off the nose, and at least a dozen other dings that needed attention elsewhere. But I called Renny who said it was 20+ years old, and I’d never had one before, and it was (almost) the right size, so I just couldn’t resist. :slight_smile:

And, just like you’re working on, the knee-resting area when prone paddling was really mushy. Especially along the right side - it had made spiderweb cracks in the glass right where the lap from the bottom probably ended and was mushy on the deck from there.

My solution was to run the sander along that trough until the weave of the original glass was evident and the surrounding area was roughed up. I filled it with a smear of epoxy, microballoons, and a tiny bit (a 3d nail tip) of yellow pigment to match the old glass on the deck. I worked it in just like taping a wallboard joint. Then sanded it flush, glassed, hotcoated, and sanded fine (just like the whole rest of the board). Its really strong now, and I don’t think it added much weight. In fact, considering how much weight the whole process could have added to the board, it still feels about the same. Just control your resin use and everything is fine…

The dark spots next to the rails are where I glued it back together in the middle break with foaming PU glue - something that also saves a ton of weight over resin + fillers. That was after I’d fixed the nose:

You can see the snap in the stringers at the back of the repair, and a couple foam chunks I had to replace & reshape near the front…

But after glassing the bottom, I decided to make the deck look better, so I did the same epoxy/microballoons/pigment fix on the deck at the nose… it came out fine, especially since it’ll be covered with wax.

I have a 17 year old 10’6’’ that I shaped for myself shortly after Clark released the wonderful 11’3’’ Downing/Velzy blank.

It has two huge oil-canning sections on the deck, I’ve gone through the same musings. I’ve asked the best ding repair

guy I know to fix it, but he says it’s hopeless and I should just ride the damn thing and pour the water out of it when I’m


Your fix on that Yater looks nice but I don’t quite understand what you did to the existing deck glass in the delammed

area. Did you sand it thin and then cut it out, or did you put your slurry over the existing glass?


I sanded it thin - gloss & hotcoat gone. Then the fairing is over the remaining latent glass, and the new glass over that. Then hotcoat, sand, and cut & polish without another coat of gloss. Hotcoat polishes up well enough when its going to be waxed. :slight_smile:

I think the key is that it’s epoxy instead of poly resin as the binding agent in the filler. Epoxy is lighter, more flexible, and sticks to stuff better (in scientific language) without cracking out. Both above & below. And then the layer of glass over the fill bonds to the original exposed glass on both sides of the fill, and the resulting compound curve - with cloth shaped like an eyeball in cross-section - is strong enough to span the weakened foam, where simple glass or a new skin, or fill foam, would not. So basically, I’ve made an invisible sandwich skin over the compromised foam, with epoxy & microballoons as the core of the skin. Very strong, yet flexible enough not to create problems in the adjacent areas.

I’ve filled mushy spots like this before, even big dents from my own heavy knees where I knee-paddle. No problems afterwards at all, as long as the foam underneath wasn’t totally pulverized prior to the repair.

i’ve done several delams lately. current technique (?) is this:

use a router with a 1/8 x 3/8 bosch straight bit. mark an outline outside of and completely around the delammed area, using a pencil or a sharpie or a posca pen or whatever does the job. set the bit depth to maybe 1/16 inch. follow the outline and remove. i usually throw this away, but it can be saved and reused. the glass outside of the cut is usually adhered firmly to the remaining deck foam.

there will be an area of “dead foam” and a narrow band of “good” foam around that. i scrape out the dead foam using the little ace hardware surform with the concave blade, or with a razor blade, or with sand paper or whatever else would work. this leaves a depression of good foam, a raised band of good foam and the glass of the deck around that.

i then use DAP fast and final spackle to fill the depression. if you use a vinyl spackle, it will not work. the DAP is water based. the vinyl is not. the first one of these i did was on my board with vinyl spackle. the delam re-delammed almost immediately. (poly repair). i usually thin the DAP with distilled water and spread it on with a brush or a spackle blade. when dry, i sand even with the ring of good foam.

using 4 oz cloth i laminate but do not overlap the glass on the deck. then i laminate a 2nd layer of 4 oz lapping out onto the deck. apply sanding resin and finish to taste.

this is what i call a functional repair. it is not a restoration technique, as the newly restored area is usually quite a bit whiter and brighter than the rest of the board. haven’t had any complaints…yet.

the DAP seems to bond tightly with the foam. it’s much lighter than resin and qcell/microballoons.

FWIW, this is a technique I completely support as well.

There’s been a lot said about spackle (“creeping evil!”) and how water-based materials don’t belong in watercraft.

However, spackle is silica, latex, and water… and it dries when the water evaporates out. So that leaves silica - then same exact stuff as cabosil - and latex. Sounds pretty waterproof to me :slight_smile:

Nobody freaks out about painting their houses with latex paint. If “water-based” paint were a problem, we could only use it until the next rain. But the water is only there as a carrier & solvent; the paint works because the water leaves. Same as spackle.

Good call, PeterG.

Hi Benny,

Just thinking one step further, isn’t it an option to fill latex paint with micro balloons or is the latex carrier in spackle different from latex paint.

This can even weigh less…

Do you know what other carrier would do this trick?

Thanks, Soul

Mix acrylic paint into your spackle before use. Thins it out and adds adhesion to the mix. Spackle out of the jar can still be wet out after thorough drying and turn back into a slurry. If you’ve ever left the lid slightly loose on the can, you know how dry it can become. If you mix with a fair amount of Liquitex white, it doesn’t wet out as readily. My $.02.

Thanks for the reply, Benny, but I fear that my board is too far gone for that kind of fix.

Interesting that it works though, always thought about trying something along those lines

on smaller crushed areas before they delam severely.


The worst delams I’ve ever had that I fixed successfully were with balsa inserts, 1/4" thick. I’m talking about when the foam is all mashed down under the oilcanning, with a lot of space to fill…you can shape it back down to the deck profile, then glass over - and although it may look a little bizarro it is bulletproof.

I have tried lots of other methods too but for a really bad delam, that’s what I’d do.

I’ve done the microballoons/latex trick as a filler but using pva glue instead of latex paint. Seems to have a good strength to weight ratio, can vary it quite easily, and it’s a bit nicer than working with a water based glue than epoxy or poly resin. It does take a long time to dry out though, and I expect you’d want to use a waterproof PVA. I expect you could mix some housepaint or tempera powder in if you wanted to match a colour or add UV-brighteners.

Hi Muhleder,

Thanks, just thinking,

wouldn’t acrylic paint or floor lacker be a good medium to mix the balloons with?

I don’t know how epoxy bonds to latex paint, acrylic works fine.

Maybe some additive that conducts water would make it dry quicker, cotton maybe or hempfiber…


kia ora keith

how did you get the balsa down on the foam

do you use a vacuum and do you use glass or an adhesive on the inside

just wondering cuz im fixing a snapped poly longboard at the moment and was thinking to inlay some balsa into the deck

thanks in advance

Howzit Keith, Back when Clark sold sheet foam in different thicknesses I would just rout out the foam to the depth of the sheet foam and resin it in, then shape it down and glass it. Worked really well then Clark stopped selling the sheet foam.Aloha,Kokua

The surface seemed rough enough that you could get a good mechanical bond I would think. I think latex paint, acrylic paint and PVA glue are all types of acrylic binder(?). I did a bit of reading up on it when I tried this but it was a couple of years ago now so my memory might be off.

I’m pretty sure that latex paint is ok thinking a bit more, as I think PlusOne mentioned using a bit of brilliant white housepaint mixed in with spackle to get that UV-brightener bling. I’ve done the same trick with a board that’s now a year old and haven’t noticed any bonding issues so far despite mistreating the thing horribly.

Cotton fibres mixed in might help it dry quicker, that’s quite a good idea. I think the samples I tested were about an inch square and took 3 days to dry out properly.

I used PVa cos I remembered everyone at art school pouring a load of PVA into a mould with colour swirls and after it dried they’d get this big thick lump of translucent rubbery plastic. Cheap and cheerful. I think if you used any of the other types you mentioned you’d want something that dried thick, like the 3D acrylic paint. I think otherwise the stuff would shrink away and leave voids between the microspheres giving you a weaker solid. Only way to know is to test though, shear strength is the important one when working with composites, not just compressive. If you were doing thick fills you’d need to test that I imagine.

Just for the record…

My “campaign against spackle” is/was simply a reaction against what I (rightly or wrongly) perceived as overuse of the stuff. Like sealing compsand cores with it (there’s plenty of better alternatives). I just think that in many cases there are other better choices. Sometimes it might well be the best thing to use. And other times not.

In this application I can’t help wondering some things… Like “How strong is it when it’s dry? Does it crumble? Fall apart? What happens when you flex it repeatedly?”. I guess I’d generally prefer as similar a material as possible in a repair. If that can’t wornk then what choices are there? Maybe spackle is the best for application X, but I doubt it’s a panacea of repair and construction!

Since this board is PU I would have thought the best material would be PU foam. I might or might not be wrong. But at least I have started to get people thinking about alternatives.

I’ve used a thin layer of resin w/ microballoons to adhere the balsa to the foam; then shaped the balsa down to deck profile, then a light glass over it. The balsa is a lot stronger than the foam around it so it doesn’t need heavy glass.

Have you tried checking out these chaps?

hi doug.

well, i found that the vinyl spackle adheres well to the foam, but not to the poly/glass resin. the h2o based spackle also seems to bond very well to the foam as well as the polyglass/resin. i’ve used that on a couple of thruster delams, and no complaints about re delamming yet.

found out on a 9’ board of mine, that the vinyl spackle, by the way, is a bitch to dig out of the foam. i had 3 relatively large delams (football sized) on the deck of the board, right where my feet go (no i am not a tripod), when i turn. couple the delams with numerous run in with a local pier repairs, and finally decided to strip and reglass the whole thing. and wasn’t that fun. no.

filled all the delams with h20 based spackle, as well as filling in chunks on the rails where the stripping process didn’t go as well as hoped.

getting ready to glass in a day or so. report on the longevity of the DAP to foam to glass pending heavy usage in the next few months.

how strong when dry? more pressure resistant than foam. i can thumb crush the foam but not the spackle.

crumble? no. not after sanding/screening. just the irregular surface after the initial fill might be a bit crumbly.

flex? probably not much. but i don’t think on the deck of a fat wide longboard used on the e coast of fla, that flex is much of a factor. on the thrusters i repaired, the delams (from rail to rail) seemed to be combined with some buckling, so i think that the foam itself had some flex problems also. none of this stuff is perfect.

got the idea to use the spackle when i read on here that many epoxy builders used to use diluted spackle to seal their blanks before glassing. would that affect flex also?

a question about using foam inserts for large delams. you would rout out the delam to its greatest depth so the surface at the bottom would be even? then contour the plug to fit? glue in place? what glue? i find that gorilla glue leaves a lot to be desired.

i like the idea of balsa veneer inserts.