Rail problems.

I’m having a problem with my rails now…

This is a kiteboard I’m making, and my layup was H80 bottom, EPS core, H80 top and on the sides I just made up some epoxy and hollowglass microspheres. Now, my vacuum didn’t pull hard enough (piece of crap venturi vacuum, getting a thomas soon maybe) So the microspheres didn’t really do their job in spreading out (maybe I didn’t use enough?) So the rails just kept popped up with air inbetween. I just mixed up some more mush, deciding I’m going to just use this as the rails and not wrap them at all. Well, the mush was hard as hell to work with (Microspheres, cabosil, very fine carbon fiber and very fine eglass) so I take it this should be fine, but I ended up clamping some parts of the rails too just so it’d spread better too.

Looks like I didn’t mix enough and I couldn’t clamp enough either… So now I’m moving onto plan C… just going to handshape the rails (lots of sanding :() then I’m going to just wrap them I guess… what a pain this whole process was.

On my next board I’m just going to have to find somewhere to get some premade ABS rails so I can lay it up easier.

Now I smell of epoxy (did this in a non ventilated area and no respirator YIKES!), am kinda aggrivated, and have to go to sleep…

Oh well, this’ll all turn out fine… it’ll be fixed tomorrow, early.

Here are some pics before the rail process just to hold some people over incase they’re really interested.

EDIT: Can anyone guess how old I am to be doing this?


I’ve never worked with sandwich core materials but, from what I’ve seen in this forum, a kiteboard seems too thin to allow PVC core to bend around its rail (no matter how good your vacuum pump is).

In fact, some people just glue PVC+inner glass to bottom/then glue PVC+inner glass to deck/then cut rails vertically/then glue PVC stripes+inner glass to both rails/then shape rails.

Like this

So, go on. Take a handsaw or a jigsaw and cut vertically about 1" of rail or what you need to get a flat surface.

Wakeboard rails, just handlay the top extending 1" past the rail, let it droop.

When that cures, handlay the bottom, so it meet the top.

Trim with sureform down to 1/4" past your airex…

Flip board on rail, fill the gap with mix of microballons and epoxy, or chopped glass…

You mean to handlay the glass right?

That’ll work… I was trying to get away from the wakeboard style rails… but then again I really do like them.

I have got to trim off some of my rails then and just do it that way… looks like I will be sanding :frowning:

And about having the Divinycell wrap the rails, that was never the idea. I just wanted them to join up together… not wrap. Then I was going to fill that gap with microspheres.

So then I can’t vacuum on my top laminate can I?

I was planning on vacuuming both laminates at the same time… but I’d rather get the rails done right.

Thanks LeeDD, you’ve been a great help with all my questions.

I’ll make sure to update this with either a New post or probably a new thread (those get viewed more) of when it’s done.


EDIT: Can anyone guess how old I am to be doing this?

Well knowing my generations attention span between 14-16.

You’re doing good!

Pic you posted tells me it’s wakeboard rails, thin, and fill is the easiest approach.

Are you using concave bottoms yet? Most guys here, from JonahLepak to LMG uses that bottom for lift, upwind, smoothride, and stiffness.


A couple of things you might consider for your next attempt:

Epoxy mixed with fillers is heavy. If you end up using lots of filler to get things to fit together then you probably will be better off just using solid divinicell for the core and don’t bother with the eps.

If you don’t like that idea, then try one of these:

Divinycell is thremoformable. If you heat it up to around 200 degrees F. It will be very easy to get it to bend. You could use an oven made out of a plywood box and a lightbulb or a hairdryer for the heat source. Use a thermometer and keep an eye on the thing if you try it - you don’t want to start a fire. I recommend you heat the divinicell and use your vacuum bag and rocker table to form it, then let it cool in the desired shape before you try to epoxy it.

I’m not sure what happens to eps when you heat it to those temps, maybe you would need to make a mould out of something other material for the thermoforming.

A second (and probably the simplest) option for bending the divinycell to that kind of shape is to use LOTS of clamps. A long time ago, I actually did the exact same thing you are trying to do except I used 1/8" plywood instead of the divinycell and xps foam instead of the eps. Plywood is much stiffer than divinycell so this should work for you: What I did was use a bunch of ratcheting tie-downs to clamp the parts to the rocker table, at least one tie-down every 12 inches, then use thin wood wedges (wood shims that carpenters use) to get the deck foam to bend down to the bottom. Just slide the wedges in under the tie-down straps where you need them (near the rails).

Sounds more complicated than it really is - If you do a “dry run” in the clamps before you start gluing you will be able to spot potential problems and have time to solve them before you mix any epoxy.

I have cut-up parts from one of the boards I made that way, i’ll see if I can post a photo for you.


this one’s mine! No concave for me.

I don’t like concave… But I plan on making another with concave soon.

Just these rails have always been a B#$%^ for me to do… last one the rails kinda worked, kinda didn’t.

This one I was going for a different approach, and it didn’t work well at all.

I like the EPS divinycell layup because it’s lighter and flex’s better (in my own opinion) then plain divinycell or then 3 layer of divinycell (I’ve rode boards made both ways and this really flex’s a LOT better while still maintaining strength)

My last board ended up weighing 3.6lbs complete. It was 124cmx44cm and it was quite thick, much thicker then this one. So this one I believe will weigh about the same if not less.

It’s looking pretty good this board, maybe a bit too wide… 40cm… and I kinda want to take 2-3 cm’s off… but that’s a lot of sanding :eek:

I’m doing more testing on fins on this board… making many different designs, see which works best. I’m just coming off an injury and I’m stoked to get out and ride! Picking up a 9m Slingshot Fuel this friday too!

Next project I think will be a new surfboard… we’ll see though.

EDIT: I shape the EPS beforehand which should’ve clamped down better, BUT! my vacuum didn’t pull hard enough…

Last board I handshaped some Divinycell rails and it took two times in the bag to get where I am now… so I think I’ll keep doing it this way, just do the wakeboard rail layup idea. No need for the divinycell to wrap the rails… they’re supposed to just join together and not really form the rail… I don’t know, it’s hard to explain.

Next board I think I’m going to try ABS rails… even though I’ve been trying to stay away from that option.

Then again, if the wakeboard rails turn out really nice, I’m staying with those.

Here’s 2 pieces cut out of a board I made in spring 2001. Piece lying on the floor is cut off one of the tips. Piece in clamp is center section of board.

Imagine that the 2x4 it is clamped to is really the surface of your rocker table.

Note the location of the wood shims.

The deck ends up with compound curves - taper towards the rails plus the rocker curve in the board. Wood really does not like to make compound curves- with foam it should be much easier.

I cut the deck skin a bit oversize compared to the bottom because you need more material to make the curves. after it’s glued up shape the rails, then one layer 6oz glass on each side with extra glass tape on the rail seam. With divinycell skins you would need more glass, but probably don’t need extra tape on the rail seam.

These boards actually came out lightweight (for a kiteboard at that time), fairly strong, but a little too stiff at 3/4" thick and way too much work to justify using such cheap materials.

Oh yeah, with clamps like this you can apply way more pressure than is possible with a vacuum bag - its just more difficult to apply the pressure evenly so you need lots of clamps.