Forums Splitboard Talk Forum Question about sealing inner walls with epoxy. How thick should i lay it on?
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  • #823576
    Mr_Orange
    76 Posts

    Hi, i just did a DIY split on a furberg 160.

    When sealing the inner walls with epoxy, how is this supposed to work?

    1) Do you actually pile on a thick protective coating layer (0.5mm to 1mm thick)?

    2) or does the epoxy actually penetrate and alter the wood itself?

    The reason i ask is because i might have screwed up my order of operations. I went ahead and drilled and attached all my Spark crossbar clips first. I probably should’ve done the epoxy seal first. Those crossbars are currently set up in a way that allows the two board halves to just barely fit. If you do actually have to pile on a 1 mm thick layer of epoxy on each inner wall, i’m worried those 2 halves won’t fit anymore.

    The Spark crossbars do have that slight bit of side to side adjustment with that set screw feature. If i’m sanding away some of the inner wall (as opposed to piling on epoxy thickness), this side-to-side adjustment can compensate for some of that. So I’m hoping that if the epoxy does actually penetrate into the wood, even if i sand away the top layer of epoxy, the wood itself is already impregnated/protected.

    I guess, worst comes to worst, i can just shift those crossbars down an inch and reattach them.a

    #823577
    Mr_Orange
    76 Posts

    Oh and by the way, this is the epoxy protocol i’m following. Did some reading on these forums and this one seems like a pretty thorough process:

    Remember: your entire board is layed up with epoxy; quality epoxy will flex perfectly well, and a properly, epoxy coated sidewall will be more durable than just abot any other approach, short of laying in an inside edge and true sidewall.

    Here is what I would do: Use high quality stuff for this, the thicker viscosity epoxies you mention here are not the best choice for doing this, you want an epoxy which is thinner, and formulated for doing layups. My favorite is WEST System 105. Then, get some WEST 423 Graphite Powder (this is basically carbon fiber powder). Sand your sidewall perfectly square and true, using a 90 degree sanding block, and about 60 or 80 grit paper. Do not sand it using finer grit, as the epoxy needs the rougher surface to make a really good bond with, but make sure it is true and square. Then spread on 4-5 coats of 105 epoxy mixed with 423 Graphite powder. Read and follow the instructions from WEST Systems, they have a really good manual available for download from their site (also some informative videos, watch them). You can put following coats on without sanding, if you do it before a full cure of the previous coat happens (see WEST manual).
    Then let everything cure really well, a couple of days at 70 degrees F or higher. After you get a full cure, sand the new sidewall smooth with 220 then 400 then 600 grit sandpaper. 600 is fine for final sanding, which should be done wet. Do not try and coat this surface with any other treatment, urethanes and such do not bond well, or cure well to this surface. But do rub some wax into it before riding.
    The epoxy/graphite sidewall will be absolutely bombproof when done right, will look pro, and, is super slippery and will not ice up ever. This approach is a bit more work, but the results can be something you are really proud of, will protect your core from damage, and will offer superb performance.

    I used this approach on my furberg to cover the uni carbon I added to the inner edge, and it came out great.

    Remember: your entire board is layed up with epoxy; quality epoxy will flex perfectly well, and a properly, epoxy coated sidewall will be more durable than just abot any other approach, short of laying in an inside edge and true sidewall.

    Here is what I would do: Use high quality stuff for this, the thicker viscosity epoxies you mention here are not the best choice for doing this, you want an epoxy which is thinner, and formulated for doing layups. My favorite is WEST System 105. Then, get some WEST 423 Graphite Powder (this is basically carbon fiber powder). Sand your sidewall perfectly square and true, using a 90 degree sanding block, and about 60 or 80 grit paper. Do not sand it using finer grit, as the epoxy needs the rougher surface to make a really good bond with, but make sure it is true and square. Then spread on 4-5 coats of 105 epoxy mixed with 423 Graphite powder. Read and follow the instructions from WEST Systems, they have a really good manual available for download from their site (also some informative videos, watch them). You can put following coats on without sanding, if you do it before a full cure of the previous coat happens (see WEST manual).
    Then let everything cure really well, a couple of days at 70 degrees F or higher. After you get a full cure, sand the new sidewall smooth with 220 then 400 then 600 grit sandpaper. 600 is fine for final sanding, which should be done wet. Do not try and coat this surface with any other treatment, urethanes and such do not bond well, or cure well to this surface. But do rub some wax into it before riding.
    The epoxy/graphite sidewall will be absolutely bombproof when done right, will look pro, and, is super slippery and will not ice up ever. This approach is a bit more work, but the results can be something you are really proud of, will protect your core from damage, and will offer superb performance.

    I used this approach on my furberg to cover the uni carbon I added to the inner edge, and it came out great.

    #823578
    Snurfer
    1448 Posts

    FWIW A thin coating of epoxy should be fine for most people – I’ve done this on swallowtail cuts and inner edges and its fine. In my case I wasn’t trying to create a tough surface as much as creating a moisture barrier for the core. I’ve re-coated the edges every couple of seasons or when I bad ding occurs and had no problems.

    With that in mind, if you drill more holes to move the hardware you’ll just end up creating more places for moisture that will need to be sealed. As well as unnecessarily creating possible points at which you might snap a board while in split mode (crossing downed timber, depressions in the snow, etc.)

    YMMV

    Shark Snowsurf Chuna
    Voile V-Tail 170 BC
    Voile One Ninety Five
    Spark R&D Arc

    #823581
    Mr_Orange
    76 Posts

    Thanks for the info.

    Ya, i actually screwed up on 2 holes on the rear. I think im going to have to plug them up with some short set screws to bring back some rigidity and close off the ends with epoxy.

    #823591
    Matt Wood
    328 Posts

    Spar Urethane is easier both to apply and touch up inmo and I do all my drilling before applying 3 coats (first one thinned for absorbtion). Tighter than a frogs ass

    #823603
    Snurfer
    1448 Posts

    ^ +1

    Shark Snowsurf Chuna
    Voile V-Tail 170 BC
    Voile One Ninety Five
    Spark R&D Arc

    #823606
    Mr_Orange
    76 Posts

    Thanks for the tip. I already ordered all my epoxy a month ago.

    Did a little more research into it and it seems like wood does absorb some of the epoxy.

    I think i’m going to just do some very minimal sanding (0.5 mm) off each wall first and then put on the epoxy. This should put me back right where i was. The cross bars seem to have about 4mm of side to side adjustment in case i go too far.

    #823614
    Scooby2
    612 Posts

    Agreed, epoxy will soak in, if it is left thick that part will crack if not reinforced with fibers. I recommend warming the sidewall with a hairdryer or heat gun before applying epoxy. Epoxy should be warm, not hot, not cool. It will flow into the wood better. I would recommend UV stabilized epoxy from Resin Research for surfboard repair over West Systems if you have not already purchased. If you use the West systems 105 by itself it will go pretty yellow in a couple seasons.
    Resin Research formula has been formulated with an eye towards fewer irritants in the recipe than most West Systems epoxies. The chopped fiber mix that Barrows was talking about will make a nice opaque edge, but might stand up thicker than you want since you already tuned your clips in. After an hour or so of curing, hit the epoxy again with heat around 170f for 15-20 minutes. The epoxy will be harder and tougher as a result.

    Spar urethane will penetrate and seal well too, but it is stinky if you are working indoors. especially if you thin it with solvent for more penetrating properties.

    #825060
    Mr_Orange
    76 Posts

    I just put on the 2 coast of epoxy and did one pass of sanding with 120 grit.

    I ran into an issue somewhat related to my initial concern.

    Because i added in graphite powder, the epoxy i used is black.

    Therefore, after some quick passes (about 10) of sanding, i can easily see that some areas of the black epoxy have been fully sanded away exposing the yellow wood color below.

    There’s 2 factors that could be related to this. 1) the initial cut was somewhat imperfect (band saw). 2) It was very difficult to spread the epoxy on evenly with a brush.

    So….. should i trust that those exposed (non-black) areas have been properly soaked/penetrated with the epoxy even though there clearly isn’t any thick layer of epoxy over them. Or should i just spread on 1 more full coat and re-sand.

    #825063
    Snurfer
    1448 Posts

    I’d just get a small 8oz can of urethane finish and brush it on – any wood that is exposed will be protected and where it isn’t needed it won’t penetrate the epoxy and will presumably just wipe off. Because it is a liquid it won’t build up and your sanding/smooth edge should be maintained.

    Shark Snowsurf Chuna
    Voile V-Tail 170 BC
    Voile One Ninety Five
    Spark R&D Arc

    #825080
    Scooby2
    612 Posts

    That’s an easy way to be done and will work fine. Apply again next fall or on any big dings that occur in the side wall. Call it tiger stripe finish.

    #825095
    Mr_Orange
    76 Posts

    Sounds good. This way my epoxy is almost used as bondo.

    Is this the spar urethane you guys are talking about?:

    https://www.lowes.com/pd/Minwax-Helmsman-Gloss-Water-based-Spar-Urethane-Varnish-Actual-Net-Contents-32-fl-oz/999914383

    https://www.lowes.com/pd/Minwax-Pro-Series-32-fl-oz-Satin-Water-based-Varnish/999918584

    Any difference between the two?

    And do i need to do any particular grit sanding before and after applying the urethane? Sounds like this stuff is much thinner than epoxy.

    #825111
    Snurfer
    1448 Posts

    I’ve exclusively used poly, non-water based

    Ex: Minwax® Fast-Drying Polyurethane

    Shark Snowsurf Chuna
    Voile V-Tail 170 BC
    Voile One Ninety Five
    Spark R&D Arc

    #825114
    Mr_Orange
    76 Posts

    Looks like they got that at Lowe’s too. Thanks!

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