My decks are cracking

Hello there. This post is part investigation log, part asking for advice, part ranting. I’ve been pressing my own mountainboard decks for a while, having great success with them and our modular mould that you may have seen around here:

Great success you say? Then wtf is that title, @thunkar?

Well, some of the boards are showing cracks, specially around the truck mounting holes and inserts

Why I don’t think this is a safety issue

  • There are no signs of delamination. I’ve had those issues in the past (not enough glue and/or pressure). This is not that
  • Only the exterior maple veneers are compromised, at most 2.
  • They go with the grain of the wood
  • I abuse the shit out of my decks. I’ve tried to break them on purpose, no dice. I’ve had my 110kg friend jump on them, nothing.
  • The flex/dynamics/behavior of the deck don’t change
  • The cracks don’t spread or become bigger after they appear

Why I think this happens

My decks are 9 layers of pure maple from roarokit (2 cross grain). I live in Spain, specifically in a very dry and hot region in the summer (we regularly hit 40°C). My theory is that the outer layers dry very quickly while the inside holds some moisture, causing the cracks along the wood grain

Things I’ve tried

  • Letting the wood acclimate before pressing. Not effective and also I cannot let it dry too much or it would be impossible to get 35° tip angles without breaking the veneers
  • Letting the deck blanks slowly dry in a semi-controlled environment for a few weeks before sanding and painting. Less cracks, but not enough.
  • Filling the cracks with epoxy, sanding and painting again. Works, cracks do not become bigger. A pain in the butt, a lot of work and ruins the finish for the decks I’ve chosen to stain instead of painting.

I’m starting to think my only option is to glass the decks, sealing them completely and reinforcing the outer layers. Maybe I’ll have to remove one veneer to keep the flex. What do you guys think? How would one go about adding the epoxy+fiberglass? (preferably not infusing/vacuum bag, but something simpler)


In my uneducated opinion, shave off a few mm off both sides of the press put a sheet of UHMW or similar on the press so the epoxy doesn’t stick, do fiberglass on the bottoms (maybe 1 fiberglass and 7 maple?), and trim the edge of the fiberglass so the wood edges are still exposed (it’ll probably end up all wrinkly without a vacuum bag and you can do all layers in the same step), also rough up the bottom layer of maple for the epoxy


The way the press is constructed, adding he UHMW should be pretty easy, but I fear that since the pressure is applied on each “rib” and relies on the wood to spread it out the end result would not be very good. I was initially thinking of just adding the fiberglass to the top and bottom the way some people add cloth skins to their decks, but I don’t know how effective that might be. Maybe thinner epoxy and some roughing of the wood as you proposed?

If you’re feeling bold and technical, remake all the wood pieces and miter the edges so it’s a closer fit

The UHMW will give you a smooth surface to work with and if you have a gel coat you can always sand it to make it smooth then paint on some low viscosity epoxy to seal it back up

I clicked because I read the title wrong, carry on :sweat_smile:


@glyphiks ?


Well, my dicks are certainly not cracking

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I would assume that the cracks are a result of the veneers getting wet and then drying out repeatedly.

To avoid it I would suggest as a bare minimum to try and seal the outer faces of the deck with a weather resistant coating, as well as trying to weather proof any holes or penetrations in the deck.

Fibreglass will more than likely stop it from happening as well, but I don’t think it’s 100% necessary if you can seal the deck really well with another method/product.

you could use sacrificial veneers outside the UHMW, just to distribute pressure. I’ve added fibreglass in the press with a similar method… I wouldn’t do it again. I just used vacuum film as the release layer and that worked fine.

This way is probably the most sure-fire way to a decent and effective result.


Thanks for the insights! I though I had sealed up the wood well with several layers of top coat, but it’s clearly not enough. I know there are specific products that seal wood, but I didn’t use any before painting/staining. Also the stains are all water based and very thin, which only compound the issue.

I’m gonna probably try the latter method with my next deck, or even seal the cracks on my current one with tinted epoxy (might yield an interesting result aestetically) and then apply the fiberglass to do a little test. Let’s see how it goes, I was pretty discouraged when this happened even though it’s only a “cosmetic” issue…pressing decks is a metric shitton of work (really don’t have to tell you of all people) and seing it ruined sucks big time.

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Is there possibly a bit of double curving going on in your mould? These cracks look like cracks due to the wood being stretched a bit in two directions which is possible when its moist, but when it dries out will crack. this is why its difficult to add concave to a mountainboard deck. its already curved in the X-axis. The reason why the top and bottom layers crack first is due to the moisture leaving first, having it shrink on the top/bottom and cracking as a result in the most stressful areas such as the bolts, inserts and foot well, where the stretching and tension is most.

Try gluing your decks with epoxy, it does not absorb/release water as much as wood glue which should make your deck more resistant to weather changes.

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I don’t think so, each rib is flat and that’s actually a limitation…our decks have almost no concave built-in. Only thing I can think of is that since the bottom of the rib is metal and the top is wood, there’s a little give on the top that could cause a curve (imperceptible to both eyes and feet). However that doesn’t explain why there are cracks both on the top and the bottom of the deck.

We tried once to make a hybrid wood/carbon fiber deck using epoxy as glue, but the result was disastrous (mad delamination). However that might be due to inexperience and a poor choice on the type of epoxy we used. Any recommendations?

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I have a deck with a similar issue. My deck that has proper sealing on the top and bottom (but maybe doesn’t in the holes) and yet it still has some small cracks similar to what he has happening. Although my deck is completely flat so not a perfect comparison

I could be wrong, but I think the proper steps are to paint/stain and then seal so I wouldn’t change that part at all.

I’d fill the cracks with stain-able wood filler and use the same stain on it and then put some more sealant to be safe.

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easy fix, local carbon cloth reinforcement

Any deck with any amount of camber, drop, curve, concave, is a real motherfucker to get perfect. I’d say it’s more of a grain location on certain shapes. Sometimes I will pull a big drop out of the press with no issues other times its a split nightmare. I keep all my veneer in a climate controlled room. You just gotta be one with the wood. :man_in_lotus_position: