DIY: foil track mount on a polyester shortboard

[reyrivera]

So I have this favorite shortboard of mine that I have been re-glassing every few years, used primarily for surfing and as a backup kiteboard. It is an old Clark foam fiberglass polyester surfboard.

Now, I don't surf as often as I used to, especially with shortboards, so this board is used primarily as a kiteboard.

Its time to re-glass the board, and got some inspiration on kiteforum on installing a sliding foil mount on my old board:

http://kiteforum.com/viewtopic.php?f=199&t=2391901

I have plenty of experience with polyester resins and light weight divinycell foams, but not this type of build where you need additional strength to prevent board buckling under pressure. The kiteforum post should give me the knowledge needed to get my build started. I also have a pair of 10" Chinook fin boxes.

For local DIYers out here in our neck of the woods, where can I find local shops that can sell high density foam pieces? Any recommendations on what foams you guys use and which reputable shop to buy it from?

Thanks much,
Rey

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[NorCalNomad]

I just did exactly what you're doing but put my boxes into a FW vanguard that I snapped. I skipped the HD foam (well see how that goes) and just put carbon reinforcement top and bottom since I was already fixing the buckle.

Not sure where locally to get HD foam...I know TAP doesn't have it. MAYBE http://www.douglasandsturgess.com/ has it.

If not I found this website https://www.freemansupply.com/

[reyrivera]

Thanks for the info.

I'm thinking if I can't find HD foam, I will just use plywood, sandwich the foam area where the rail is gonna be installed, and then add a pair of stringers up to where I would be theoretically standing on the board to accommodate my weight and forces acting on the mast collar.

I'm gonna paint the board anyway so all the changes and ugly sun damage will be covered.

This will probably a slow build but will continue to post my progress as necessary.

[Yoda]

First pic shows what happens when done incorrectly. There may be some useful info for you in this thread. Check it out!
https://www.standupzone.com/forum/index ... #msg357653

[sflinux]

I like the idea of plywood, baltic birch is my favorite.
I would be mindful of the rocker line of the Clark foam board, as it may have more rocker in the tail then the LF fish. I would look at the slope of the rocker at the LF fish insert, and make sure the slope of rocker is similar to the Clark board. I.e. you may want to slide the insert slightly more to the nose if there is more tail rocker.
I just mounted a diy hydrofoil build and it was initially mounted a little too far back, so I have to move it forward. Remember that a longer board will be more likely to pearl, another reason to have the mount plate further forward on the board.

[reyrivera]

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Thanks for the heads up sflinux. Thankfully the rocker is more at the nose, than the tail. This was my go to board when I used to ride regularly at OB a long time ago. The tail is flatter compared to the nose.

Here is my a first mockup on how I plan on doing this. I created a cardboard template for the piece of wood. I think this will be strong enough, I don't want to get the board too heavy. My goal is to make it strong but light. The masking tape is where the fcs fins are located. This is what I'm guessing to be the ideal spot to install the pieces.

Steps:
1) The plan is to bolt and glue the tracks to the plywood as seen in the mockup
2) Dig out the foam on top, including cutting through the bottom to accommodate the rails. Still not sure whether to replace some of the section with high density foam because the wood should be strong enough to keep the build together.
3) Sand and reglass the whole board with polyester resin. I still got enough fiberglass resin to run three layers. Epoxy might be better, but I need to use what I have at home. I got to use what's in my garage or stuff will keep piling.

One drawback I see is the rail mounts might loosen up and cause to leak from use. Maybe surround the rails with wood as well to keep this from happening?

Damn, now I can't wait and see if this is surfable with a short mast and test it at Linda Mar. baby steps ....

[reyrivera]

Got some free time today, went ahead and got some plywood, made my measurements and cuts.

Now the board is ready. Time to break out my router and dremel, and start digging out the foam and embed the plywood and rails.

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[NorCalNomad]

That is some thick looking plywood

[reyrivera]

Yeah, that was the only thickness they had at OSH, they ran out of thinner plywood. I figured its only gonna add about a pound to the final build. The board will still be lighter compared to production ones.

[Erik]

I added inserts to my poly board about a year back. I ran carbon stringers "T" shaped carbon stringers where the foil contacts the board, and additional carbon under the inserts. I also added an additional layer of glass top and bottom. It's held up to a fair amount of abuse. The caveat for sure is that I did not care so much for the board. I'd double check the location of the foil on your board. My understanding is that the centre of lift is about in line with the front wing, so you want to place the insert so it puts the front wing between your feet. Your's looks quite far forward.

https://photos.app.goo.gl/26NOfdq2JYJNYniA3

https://photos.app.goo.gl/3AeA7uteEFQpLwY13