Hey windsurf crew

Kite interloper here! Some of the crew are batting around options for attaching foil mast plates to surfboards. Options include glassing in fin/mast tracks or various through hull options. Each has pros and cons, with the possibilities for catastrophic failure.

This seems pretty similar to the forces involved in attaching windsurfing masts, so maybe we can learn from your painful lessons. EG how often do fin/mast tracks fail and why? Any lessons learned for how to avoid this happening?

For example, I've read some reports lately of people's foil masts ripping off from the brass t-nuts actually breaking ... some seem to suggest stainless t-nuts are better.

Any tip and tricks appreciated.

John/juandesooka

Surfboards are too weak, even the old glass windsurfers, had many more layers of glass than a surfboard, and extra around the mast base, with a layer of glass between the mastbox and poly. And were prone to breaking down over time near the mast track or ripping out of the deck.

I would look at comp-sand construction techniques. Almost all of the foil windsurfers, and formula, slalom boards etc, use a deep tuttle box, that runs through the board entirely, distributing forces on the top and bottom. And i suspect the foil boards use extra fabric and larger blocks of closed cell foam reinforcement around the box.

I can see how a mast track / fin track would fail over time....cracks/delam, water gets in, weakens the glue holding it in place, track starts to move a little, then the leverage rips off the whole deck, with track attached. That about right?

Though here's a catastrophic failure of a tuttle box:
https://www.standupzone.com/forum/index ... #msg357653
Only top and bottom coat holding it in place I guess. I hadn't considered failure up through the deck! But I guess that's how it might go in windsurfing, the pulling force is upward.
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juandesooka wrote:I can see how a mast track / fin track would fail over time....cracks/delam, water gets in, weakens the glue holding it in place, track starts to move a little, then the leverage rips off the whole deck, with track attached. That about right?

Though here's a catastrophic failure of a tuttle box:
https://www.standupzone.com/forum/index ... #msg357653
Only top and bottom coat holding it in place I guess. I hadn't considered failure up through the deck! But I guess that's how it might go in windsurfing, the pulling force is upward.
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Pretty much, the old boards would look like a pealed banana around the mast track.

Looking at that foil sup failure, looks like only eps, and glass. A larger block of a-cell around the tuttle box, along with d-cell (or balsa) sandwiched in the top and bottom deck would have prevented that. The idea is to distribute the forces, modern windsurfers have d-cell covering the entire deck and bottom, so the forces are distributed, and double layers of d-cell sandwiched, with glass, carbon and Kevlar in key areas.

Seems like if attaching to an existing beater kitesurf board then the through bolt method with added glass patches woul be fine for a while if the board has a stringer.
But yeah I was building from scratch I would use some of the methods and materials windude described. Even sawing the blank and adding a stringer on each side of both mast track boxes and then glazing it super heavy in the right areas would work and maybe save some bucks on the exspensive reinforcements.
It seems like there would be way less force on a foil than a mast or even fin boxes for that matter.

I heard kayakdoc suggest using a used carbon shaft golf club. Cut 4 sections to support the bolts between the reinforced deck & bottom

JL wrote:I heard kayakdoc suggest using a used carbon shaft golf club. Cut 4 sections to support the bolts between the reinforced deck & bottom

+1

Without these you'll crush the core in a matter of hours or less. I recommend installing them using polyurethane (white gorilla glue is good stuff) rather than epoxy. Then glass over the top and bottom of course.
Sometimes archery stores will have long and wide enough off cuts of arrows to get the job done.

I would defer to my learned friend DavidM in regard to the epoxy and laminated matts repairs/installs. He has done a number of these.

Looking at the picture I would suggest that a board repair might have been the least of your worries, holy cajones hazard!! Something else going on there....bottom impact maybe

I have never heard of or had a windsurf mast track ("A" boxes) fail, I had only one leak on an old fiberglass board.

I have had several "A" ... for American (or AKA Chinook) fin boxes fail under load, I would not use these of course for foils. I have not had a power (single bolt) or tuttle box fail, tuttles are deemed the strongest as they are deeper and have two bolts. Both of these penetrate via bolts the upper deck. I prefer power boxes due to shorter length bolts and quicker fin changes, much better and the only choice if you run longer/wider fins....hate A boxes and won't buy a board with them unless they are quads....even then they suck but sometimes you have to cuz there is insufficient depth in the board tail to accommodate a power box.

If a power box fails, I would suggest that a tuttle would also fail! But tuttles have the advantage of washers and bolts sitting on the top of the board usually, the power boxes have them recessed and perhaps it would therefore be a bit weaker....not much. You could also use a stainless bar over top of a longer powerbox screw and get the same deck securement. Rubber washers can help to absorb some deck shock in case of impact.

Yes, the brass nuts are designed to tear out under load to save the box, they actually fail over time as they do corrode..... you use stainless at your own peril They also make stainless with plastic inserts so they fail under too heavy load...such as when striking an object like a log

Yes +1 for Gorilla Glue, awesome. I haven't used the white stuff, maybe I will try that. Brown stuff even calls for some moisture to properly adhere which in a board failure/repair is likely. Can be trimmed, cut, somewhat sanded, and epoxied over nicely....turns a bit sticky sometimes if sanded/heated, just scrape/shave with razor....

As to the rods, I would use old racesail carbon battens (on flat) or tubular carbon battens, tons of old sails around Also I would suggest that Plastics and Paints will likely have rods for purchase.

Thanks all.

Sounds like for mast/fin tracks and tuttles, as long as the installation method is sound, the likelihood of pulling it out is not high. Meaning you aren't hearing about it happening all the time, would be considered rare. Though maybe more likely in fibreglass boards like surfboards maybe. Still, risk of failure seems low enough to not worry about too much -- a viable option for foil installation.

For through hulls, I've used the golf club shaft method, worked well. Other options are to drill a larger hole in board, fill with epoxy (with glass strands), then drill bolts holes through the epoxy. Similarly is using G10 rods or equivalent, then drill through those. But then you have holes through your board, should you want to surf it! :-)

I would not trust any plastic fin box (all Chinook boxes) windfoiling unless it was tied into the top surface lamination (fin bolts not countersunk). This pretty much rules out any Cobra board. Even then only with a foil that has a flanged head like slingshot.
Actually I wouldn't use a non-flanged foil in any board that wasn't specifically made for it after seeing how much force it took to remove a Starboard foil from the matching board after just a mellow session. My slingshot just pulls out with zero force.

P.S. the white gorilla glue functions the same, it's just visually nicer to glass over. Pretty sure you don't even "need" glass to make it watertight. Also sticks to the ABS skin on old boards nicely. It's my preferred way to fix soft spots since it creates new foam in a way.

grantmac wrote:I would not trust any plastic fin box (all Chinook boxes) windfoiling unless it was tied into the top surface lamination (fin bolts not countersunk). This pretty much rules out any Cobra board. Even then only with a foil that has a flanged head like slingshot.
Actually I wouldn't use a non-flanged foil in any board that wasn't specifically made for it after seeing how much force it took to remove a Starboard foil from the matching board after just a mellow session. My slingshot just pulls out with zero force.

P.S. the white gorilla glue functions the same, it's just visually nicer to glass over. Pretty sure you don't even "need" glass to make it watertight. Also sticks to the ABS skin on old boards nicely. It's my preferred way to fix soft spots since it creates new foam in a way.

Of the few boxes I've taken out of cobra boards, none were stamped chinook, the chinnok boxes are about twice as thick as the boxes from cobra boards. Cobra has serious quality control issues, IMHO.

Use a tuttle box and set it in last-a foam, or lots of d-cell, the deep tuttle/tuttle is designed to run through the deck and bottom of the board, so should the last-a foam . The advantage of a chinook box, it's not already set moulded into foam, so you can add extra easier. <a href="/https://www.youtube.com/watch?v=i7PfoZW_Ivo"> Here's a video of a tuttle install in a surfboard for a foil</a>, I would use a Chinook deep tuttle box and maybe double the size of the last -a foam around it compared to what's used in this video, closer to what it was before he chopped it, this would help distribute loads from the foil more.

I still wouldn't trust a regular Chinook box to stand up to foiling with a non-flanged foil.
The exception might be if you add material to the top of the box to prevent the foil from wedging it's way up inside the box, but I'd still worry about it.

Of course if you have the skills to install a box then just building a carbon one from scratch isn't all that tough.

Grant, this should almost be another thread lol. Can you expound upon this Gorilla Glue thing? Prefer over two part epoxy aka West System? Sure sounds ideal, can it be used to install fin boxes, or is it back to epoxy for that?

Yeah its drifted a bit.

No I wouldn't install fin or mast boxes with it. It's main strength is when you need to repair the core material and you don't want to remove the outer laminations. The GG expands and creates a sort of closed cell foam that binds the crushed core together. But it definitely doesn't have the strength or rigidity of epoxy and it doesn't work with glass cloth at all.

Back to foil mounting:

The BIG thing in my mind is to make sure the core and bottom lamination transfer as much load to the top as possible. Even with a kite style plate there is a lot of force going through a very small area. Like putting a brick under your board on dry land then jumping on it.

On my recent through bolt conversion i was going to use the golf club method like jaundesooka but they wanted 9.99 for each carbon driver at value village which seemed waaaay over priced by at least 5 bucks so I opted for drilling 4 oversized holes and filling with a mixture of chopped strand and epoxy and then adding many layers of oversized glass patches to each side for a couple reasons.
One reason was obviously to beef up the board and help spread the load but the second reason was that I needed to level out the bottom concave so the mast plate would be sitting completely on a flat surface due to the concave. I also ended adding a fair bit to the deck as it was pretty kicked in.
I have no intention of using this board for anything but a foil platform so not too concerned about altering its wave shredding capabilities. It has held up for 10 sessions so far and was just a cheaper option for me than buying a real foil board.