Any suggestions to not only repair the damaged boxes but strengthen the foil box set-up as well. No real damage to the surrounding foam but the high density foam is destroyed. Both stringer's are ok.
This is a 7'8" x 28.5" x 125 litres sup foilboard
cheers

Those boxes need to be attached to the deck.

How did it happen ? and what brand of board is it

Piros is right, when you cut out the HD foam and set in a new block, make sure at least the front and rear, but maybe the whole thing, goes through to the deck. Sand down the edges of the remaining glass, careful to get to where it's still attached to the foam as well. Then fill/level the rough foam where the foam was with epoxy and qcell or similar. (Or you could route that down and glue in a new layer of EPS and sand/reshape it.
Sorry this happened to ya, but you can fix this. Make sure and show the builder so they can learn as well. If you search the standup zone I have a build thread where I do an HD box install that has blocks that connect to the deck that might help you visualize.

Ive got a prone board in the finishing stages that has the boxes glued and glassed to the stringers. I can't tell but it looks like this might be set up that way. If so, be careful to get better adhesion. I used gorilla glue in my case and scratched up the surface of the box pretty well to give it some tooth.

Finally, for those of us building these things can you give us some info?

How old was the board? How much do you weigh? What were you doing when it failed?

That'll help us learn about how to make these stronger and why.

Has there ever been a production board with tracks that hasnt delaminated or completely failed? That extra carbon aint gonna stop you foiling but the tracks ripping out sure will! I put my tuttle boxes in with 3 layers of 400g carbon bi ax top and bottom (the box or tracks penetrating the deck laminte is essential, if you dont do this dont worry about the rest because it WILL fail) the first and largest patch atleast 500mm long and most of the board width. Never had a problem and those boardshave smacked the bottom or gone over the falls plenty of times

Saltydays, you're lucky the Axis didn't sink deep in the Sea...
Piros is 100% right, but this failure was probably caused by a insufficient adhesive connection between the SS finbox and yellow foam. If the finbox bond fails, a deck connection will not help you either.
I would say this is 100% a manufacturing fault.

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container said..
Has there ever been a production board with tracks that hasnt delaminated or completely failed?

Yes we have never had a box crack, delaminte of fail in any way at ONE and we treat them like ****. Have seen a lot fail over the years but I know this is one area I would want complete faith in, I would hate to lose my foil!!

Use one of these:
www.blueplanetsurf.com/foil-strongbox.html

It would help to tie the boxes to the deck by forming 4 fibreglass bolts by drilling through each end of the boxes right through the deck and then filling with wetted out rovings splayed out at each end. This would shorten the tracks length but make them a lot stronger. Would be nice if the tracks had room to drill through at each end without going through the slot.

In reality by the time you buy new strong boxes and repair the bottom of the board , you be up around the $600 mark for repairs , not really worth sinking that cash into a 7-8 , you be lucky to get that if you sold it fully repaired ,so good time to look around for another complete second hand board and drop down in size a bit. Look at this for 500 bucks.
www.seabreeze.com.au/Classifieds/Foiling-SUP-Foilboards/~ldkgg/2018-Starboard-2018-610-Hypernut-4In1-6-10.aspx?_page=2&search=t03ywWW5dNOb2H75fxyvOw%3D%3D

What a complete POS. I can't believe the contempt that many manufacturers have for their customers. Foiling has brought out the worst of the "get a product to market ASAP and let the customers do the R+D for us" mentality.

This requires more of a rebuild than a repair. A basic analysis of the forces involved will tell you where the reinforcement needs to go. If you have a friend who is an engineer or architect they should be able to talk you through the areas in tension, compression, shear and transverse load. Carbon, as Slingshot is obviously yet to learn, is only useful if applied in locations and with fibre directions that match the load. It's also only useful if both ends are laminated to surfaces and materials capable of handling that load (not styrofoam).

Is the mast or fuselage bent and how did you get it back , did it float.

Judging by the damage on front of foil I would guess impact. Either picked up the foil from very shallow water or they ripped the boxes out at home.

Yeah my angle as well Hilly. The installation isn't that bad , both boxes attached to stringers , set in HD foam and full carbon bottom , sure not attached to the deck but those boxes didn't fall out they were ripped out. The board is also really big (7-8) which also adds to the stress getting flogged in the shore break and bottom strikes plus leg rope wraps.

If i say it will everyone get upset? Made in China?

Maybe but I have never seen a Chinese double stringer board.

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djdojo said..
What a complete POS. I can't believe the contempt that many manufacturers have for their customers.

It is not as easy as it sounds. As weight is very important for the performance of a foil boards, and most customers are very sensitive to price, you have to find the best strength / weight / price compromise, on a domain where long term constrains on a boards are not well known, as the constraints differ for kite / wind / surf / SUP / wing ... boards. Add to this that unlike one-man shaping/glassing operations, which tend to not really count the hours (and are often greatly underpaid compared to the hours spent), time to build a board is real money for mass productions, and fancy reinforcements take a lot of time.

So, you could say that many customers have contempt for the amount of time of effort manufacturers (of all sizes) put into their work by always demanding lower prices and/or rebates.

Also, mechanically, you want to dissipate the efforts. The reinforcements should have some kind of progressive (tiny) flex to dissipate and absorb the forces without suffering from stress fatigue in the long term. E.g. Just adding strong carbon pillars may just shift the failure point some inches away if this is not taken into account. It takes time to refine these kind of mechanical designs.
Disclaimer: this is my personal opinion, I am not speaking for anyone else here.

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Scotty Mac said..
If i say it will everyone get upset? Made in China?

Axis sup 6 8 at a guess, not 7 8, and made in China, Thailand or Vietnam.

Edit wrong it is 7 8, Axis Flying Dutchman. Never heard of it.

Hi Colas, agreed, all good points. Not many people know how much thought and work goes into something that is both light and durable. I used to design, build and and compete on high-end vacuum-sandwiched sailboards in the 90s, and yes, if I'd have been paid an hourly rate for building my personal boards they'd have been triple the price of a production pop-out. Still, I think more thought could be put into materials transitions between the extreme compression at the front of the foil mount, the tension and shearing at the rear, and the much lighter and more diffuse loads everywhere else.

I peruse the sup-foil forum as I'm interested in foil development, and the evolution of wingdings, but as a strapless kite-foiler, I have the luxury of dispensing with volume and so a sub 3kg board is easy to make completely bullet-proof. Incidentally, as I'm running boards thinner than 20mm, I mount with stainless t-nuts in the deck. Light, cheap, easy, and ridiculously strong. I sacrifice adjustability, but as a strapless rider I can move my feet to wherever they need to be.

Ah, it's an Axis, not a Slingshot - that font is super similar to what Slingshot have used. Either way, the construction is cheap and nasty.

In defence of the manufacturer and from someone who has built a few of these I would say that the manufacture looks pretty good for a production board. It has double stringers that haven't failed. It has good quality fin boxes with flanges that haven't failed. It has a HD foam insert glued between the stringers and the bond between the HD insert and the stringer is largely intact. It has a carbon and glass laminate of at least 2 if not 3 layers. It looks like the foil has struck something with a lot of force and ripped the whole construct from the board. It is not compression loading at the front of the boxes. If this was connected to the deck I'm guessing it would have ripped the deck too. If you put a 75 cm lever under a 7 foot board and roll it in the surf or hit something with force something is gonna give eventually. With a bit of time and effort invested that could be fixed at home for a hundy and live to foil another day.

Saltydays hasn't answered how it was done. Either way if the foil attachment box was glued or epoxied to the underside of the deck it would have been stronger. But the stronger the attachment the more damage to the foil. Take your pick.

I had an axis 6 ft 8 board with exactly the same damage. Both boxes and a big piece of the bottom came away in the surf with a 1600 size foil attached. Never hit the bottom or anything hard. I think that some damage occurred earlier though when we were towing behind a dinghy. I was in the boat and the guy on the foil was way out to the side when he did a big turn then fell off. There was enough force to yank the back of the boat and outboard sideways. After that you could see the line of the stringers on the bottom of the board. Before that the board had had at least a year of solid use by a previous owner. Board is going to be repaired by a guy with plenty of experience.
Pumping with a big foil will put a lot of force on the connection between mast and board

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Piros said..
Yeah my angle as well Hilly. The installation isn't that bad , both boxes attached to stringers , set in HD foam and full carbon bottom , sure not attached to the deck but those boxes didn't fall out they were ripped out. The board is also really big (7-8) which also adds to the stress getting flogged in the shore break and bottom strikes plus leg rope wraps.

I disagree. Its not high density foam, its foaming resin that is used for finbox /mast tracks on windsurfing boards and its barely sufficient there. It has not bonded to the stringers.
The tracks are clean with no glass around them, its a poor install with poor products.

The advantage is now its really easy to get a big block of corecell / d'cell or similar to bond to the stringers - its come out really cleanly

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Piros said..
Those boxes need to be attached to the deck.

Not so long ago you were saying that the stick on foil mounts were great

The original question was about suggestions to repair the board and make it better.

Are you doing it yourself? Or getting an experienced professional to do it?

Seems to me there are two basic options, buy a new box or salvage the tracks.

Either way, high density foam to bond to the deck. Extra glass on the deck to integrate with the high density foam.

A shedload of glass on the bottom. Maybe some carbon and away you go.

From the look of the photos the prep looks pretty straight forward. Everything came apart pretty clean.

What else would you do? According to the internet the board is only a year or so old. It seems a bit new to scrap. You could chuck it and buy a sub-6" latest greatest or something else.