Dam!
Naish 120 crossover 2018, it's a sup, windfoil etc...
Yesterday I set it up to try some prone surfing and after putting the foil in, I noticed a bit of movement of the foil. Gave it a few more harder wiggles from front to back and got a squeaking sound and I noticed the underside of the board, in front of the US boxes and even between the US boxes, was moving.
Further examination was that it was soft in front of us boxes and between.
I fixed up a soft deck a few years ago by sanding back the deck and then applying some fibreglass but I think I can't do that here. It just looks deeper. I took a video if you are interested. It is hard to see the movement though.

I see there is an interesting video of a guy who drills holes in the soft spots and then injects epoxy with some sort of expanding foam.

Really not sure what to do. Because it is a foil board I am sure that it is taking on a high level of load through that area so prevention and strengthening.
Has anyone had this problem and fixed it?

owwwww double damn Van Damn even.
If you wouldn't mind Mark, can I get all my questions ready and get back to you in a few days? That way my stupidity will come in one big blast. At the moment this project would be well out of my comfort zone but I am thinking it could be a great challenge.
Also, I think I found out how the water has been getting in. Do you think possibly poor construction?

Absolutely poor construction .

Mark is right. In early foil boards, tracks coming loose was a somewhat common problem, since nobody had experience. I strongly doubt that many (any?) companies used engineers to calculate loads; more likely, the shapers just reinforced the boxes some more, tested it for a few sessions, and then send the specs of to the factories.

When you do the repair, it would be great if you could post pictures of how the boxes were put in. Most likely, what is missing is a firm connection to the top of the board that prevents the front of the tracks to work loose over time. Without a solid connection, the box just floats on the compressible foam, and it's just a question of time until things start moving around.

Here's an image of a track install:
I had glued PVC to the sides and bottom of the tracks. On the back, the padded tracks attached to the existing foil tuttle box on the side, keeping the back from moving. Near the front, I dug a hole to the top layer, and filled it with poor foam. This kept the front from moving up and down on the foam. I've used another board with a very similar install for more than 110 foil sessions without any problems.

boardsurfr - I don't know if the pillar of polyurethane has the compressive resistance to make a difference there ...... but if its working, its working

Bonding to the deck has its disadvantages (sorta) and of course you then need to reinforce the deck lam. Like a good bottom hit to thruster fins - the inserts get damaged, pushed in, whatever. If they're bonded to the deck you might not get damage but its lifted the deck lam a little and you don't know. So you get a couple more sessions and then the repair is far more significant. Trade-offs.

Loads of info on standupzone about foil boxes. Mainly wing foil.
What seems to be working is a mixture of the 2 repairs above. A large HD foam block in the bottom. Then the fin boxes set into HD foam blocks a bit bigger than the box that go all the way through the board. Carbon over the 2 box inserts then put them in going all the way through the board. You end up with 2 pillars that go through the board. Trim them flush with the deck and laminate top and bottom.
Loads of pics and better explanation on standupzone.

Took it over to a mate who makes fins, foils, and repairs boards for a living. He likes the fins and foil stuff but hates repairing boards, so he is always very happy to impart info. There is a little bit of a language problem though.
Anyway, he reckons that the affected area goes right out to the fin inserts (maybe) and about 3/4 up the board.
Like all my stuff, I got it on the cheap but I am thinking of buying something new, hiding the board in my uncle in-laws garage and hopefully one day I have the time, patience ect.. to replace the foam. I am just a little bit time poor, at the moment, but on the other hand finally getting more "savings" (money that is temporarily not spent) through the door.
Then again I could fill the US boxes and use it as an SUP, or make a plate that runs the length of the US box and squeeze the US box to the fiberglass, preventing more water getting in.
I don't want to see a "good/newish" board go to waste but hanging out with the kids is also important and that would be the time that I would have to take from them to do this job.

I use a 90 kg pour foam for stuff like that.

Mark _australia said..
Yes poor construction. I think in the first couple years all the companies scrambled to get foil stuff out and the box (track) installs were crap. The one I'm looking at is same as a windsurf US box install with foaming resin and a bit of token glass, and they figured more glass patches over top would do it - but clearly not. It handles side load of a 30cm fin, not a metre of foil torque and the engineer bloke should be sacked for allowing it.

The secondary problem is once it moves, the glass rapidly separates from the edges of the box as glass doesn't stick well to the Chinook style plastic boxes (tracks). They needed to rough it up more, but factory will never do that they just bung it in.

I think the solution is carbon moulded tracks on PVC foam to solve the moving issue and the skin adhesion issue. I'm making some now in between other jobs

if you are making/selling carbon US / PB / SB boxes i'd be keen to talk.

Mark _australia said..
So - bit more


After block was sanded off to bottom countours, lots of carbon and glass.






Then noticed the top wanted to delam where old tracks had pushed upwards, so top bonded back on (as only minor) and a nice long stringer of 10mm x 30mm divinycell with uni carbon each side was inset:








Then a carbon uni strip on top, 2 x glass over and front foot glass patch:








Bung some tracks in, carbon and glass over, bit of router work then paint:





Then same with deck, red in clear = candy apple, couple black stripes.

Done, Bob's ya aunty.

Great repair job, but honestly seems like a waste of money from the customer's perspective!, unless the entire board top/rails/bottom was covered with a water tight outer-layer cause whatever you did not cover up is going to delaminate and then leak sooner or later based on the known construction problems.

Sandman1221 said..

Mark _australia said..
So - bit more


After block was sanded off to bottom countours, lots of carbon and glass.






Then noticed the top wanted to delam where old tracks had pushed upwards, so top bonded back on (as only minor) and a nice long stringer of 10mm x 30mm divinycell with uni carbon each side was inset:








Then a carbon uni strip on top, 2 x glass over and front foot glass patch:








Bung some tracks in, carbon and glass over, bit of router work then paint:





Then same with deck, red in clear = candy apple, couple black stripes.

Done, Bob's ya aunty.

Great repair job, but honestly seems like a waste of money from the customer's perspective!, unless the entire board top/rails/bottom was covered with a water tight outer-layer cause whatever you did not cover up is going to delaminate and then leak sooner or later based on the known construction problems.

Geez, in one thread you're telling everyone they can just use handyman thickened epoxy to bog things up. Now you're telling us you need to re glass a whole board if there's a ding !
Make up your mind will ya !!

Nothing of the sort happened - and you would not have a clue what the discussion was with the owner or quoting process!
So WTF??!!!

For the record it was $250, and I stuck by that when I needed to put a bit more work into it. That sometimes happens after you cut into it and discover more. At that point I sent pics and videos to the owner and said its worse than we thought, it will take a lot longer but I will not charge more, what do you want to do? He said please proceed.


You're outa line man.

Mark _australia said..
ummm, no.

all the bad stuff is gone, new stuff put in. You do not need to wrap the whole board in glass to make it water tight... but there are a lot of steps not shown here

Beautiful job Mark.

Mark _australia said..
For the record it was $250

What ??

Tell 'im he's joking.

He could have tossed the board and got two sets of jousting sticks for that.


Looks an incredible repair for $250.

Next time I need something done I'm paying the post and sending it to ya.

i agree. but.

i have a lot of boards of varying weights and the light ones are way more fun for blasting and jumping. so i guess its swings and round abouts.

I seem to think it's about brochure weight . That is what sells .
15 years ago it was acceptable for a 125 litre freeride board to be 9.5 kg . A lot of those boards are still alive today .
Now a 125 litre freeride has to be under 8.0 kg and is lucky to last it's warranty .
Apart from fancy material names , construction hasn't changed .
Skimping is the new cool.
Some of those earlier plastic coated composite boards were light and indestructible . Before vent plugs were needed . Maybe the sun was different then ? Also before deck grip was needed . A bitch to repair , but never needed it .