Foilmount failure

[sharksupper]

Well, the board didn't fail, but the mount itself broke!  My foil went to the bottom of the ocean.  I will give this thing credit, it lasted quite a while and abuse in some big waves... but next time, if there was going to be one, which there isn't going to be, I'd tie a safety line to my leash plug... live and learn!

[PonoBill]

Your new GoFoil sank? I thought they floated.

[sharksupper]

No it was my Lift foil unfortunately, I wish I had the GoFoil on!

[jrandy]

That is bad news. How deep of water? Know any SCUBA divers?

[sharksupper]

Hard to say, it's a sandbar and right near a steep shelf that flows heavy as the tide changes.  I might take big board out with a few leashes together to make a long one and troll with a line and weight to listen for a hard hit sound and then free dive if it's 20ft or less.  Visibility is crap, 2-3ft maybe.

Even if I do find it, one side of the plate mount is broken... as my Foilmount only broke on one side.. which means the plate broke on the other to get free...

[Dialy]

I am thinking about a conversion from M6 to M8 bolts on my Takuma and Naish base plates to make the foilmount attachment stronger.

https://youtu.be/voZKDmkDkHI

[Piros]

That's really strange how it left go. I see some sanding marks on the plate did you have a slight concave in the board , were you packing the base plate to offset this , were the T-nuts still in the other side that didn't break.

Re finding the foiling I have lost 3 and got all 3 back , longest being in the water 2 weeks. They are like an anchor and do not shift plus the aero shape seems to stop it being buried in the sand. I guarantee you it's still sitting on the bottom a few yards from where you lost it , don't give up on it.   

[sharksupper]

I was using M8 hardware.  The weak link appears to be the surface contact area of the T-nuts was too small and it loaded up the foil mount too much in a small area of the track.  If there were longer T-nuts around it would help distribute the load better to the track.  I have been unable to find anyone how makes a larger one than Chinook/etc.  I think I'd have to buy some raw brass plate and make my own rectangular ones and lose a little adjustability in the track length.

The board did have a slight V at the mounting location.  At first I started to sand down the middle of the mount, but then realized I didn't want to weaken it, so I just used very large and thin rubber washers to keep the foil from bottoming out on the center V on the mount.

The waves have been 10ft+ at 15sec+ for a few days, with 10kt current during tide swings.  I very seriously doubt it is findable at this point, but I might go drag a metal pipe on a rope around and feel for anything solid hitting when the water calms down.

[Piros]

The waves have been 10ft+ at 15sec+ for a few days, with 10kt current during tide swings.  I very seriously doubt it is findable at this point, but I might go drag a metal pipe on a rope around and feel for anything solid hitting when the water calms down.

Hell of a place to foil hope you find it....

[Newps]

The board did have a slight V at the mounting location.......so I just used very large and thin rubber washers to keep the foil from bottoming out on the center V on the mount.

Not sure if this was the cause of your failure but I stopped using rubber washers.  With so much leverage being applied to the foil, the rubber washers distort.  Now you are putting all the loads on two bolts instead of four. 

I was using them between the wings and the fuselage as shims.  Sometimes by themselves or in conjunction with metal washers.  I could feel the additional play they were causing.  I started experiencing lose bolts, cracks and water ingestion around the mounting holes.  I thought they would help the transition of the angle when shimming and spread out the loads more evenly.  I was wrong, they did the exact opposite and concentrated the loads into a smaller area. 

I now only use metal or very hard plastic washers.  The play, lose bolts and cracks have stopped. 

[PonoBill]

I thought the same thing when I read it, mounting something tied down in multiple places with flex in the system always adds to load, though I doubt the design of the stick-on foil mounts is really up to the job. When I look at the thickness of the material around the T-bolts compared to a Chinook part it looks downright flimsy. Can't be sure from a photo, but the material in a chinook box looks nearly twice as thick. Obviously, they needed to trade off the thickness of the edges to how much the mount would stand off from the bottom. Probably a reasonable compromise, but for something as expensive as a foil it's not a compromise I'd make. This does have me thinking about a leash for foils, but GoFoils DO float--I tossed mine into the pool to be sure. I'm not sure about the Kai, but my M200 floats pretty high in the water.

[sharksupper]

The board did have a slight V at the mounting location.......so I just used very large and thin rubber washers to keep the foil from bottoming out on the center V on the mount.

Not sure if this was the cause of your failure but I stopped using rubber washers.  With so much leverage being applied to the foil, the rubber washers distort.  Now you are putting all the loads on two bolts instead of four. 

I was using them between the wings and the fuselage as shims.  Sometimes by themselves or in conjunction with metal washers.  I could feel the additional play they were causing.  I started experiencing lose bolts, cracks and water ingestion around the mounting holes.  I thought they would help the transition of the angle when shimming and spread out the loads more evenly.  I was wrong, they did the exact opposite and concentrated the loads into a smaller area. 

I now only use metal or very hard plastic washers.  The play, lose bolts and cracks have stopped.

Yea, there's a lot going on, hard to say what happened.  Something is always the weak link when stressed to the limit, and no doubt the conditions I was in was pushing it.

I do believe the washers helped, otherwise the bolts would be trying to bend the foil's mounting plate around the V in the board while at the same time trying to pry the FoilMount "sticker" off the board.  They were about 1/2mm thick, so not a lot of movement.  They never got loose for a few dozen times I had gone out.  I think I just found the physical limit of what the FoilMount can take.

I just hope the RideEngine box I have coming has thicker rails, otherwise it will be a waste of time to put it in the board.  Does someone make a cassette using Chinook boxes?

[sharksupper]

Removed the FoilMount today to prep for the full box install coming soon.

I used a 1/2" router bit set at just the thickness of the plastic part and used a piece of wood to keep the router at the right height off the board.  Hell of a mess afterward! 

I then soaked the adhesive part in toluene a few times, covered with soaked towels for 30min at a time,  with scraping off gunk between soaks.  Came off pretty easy overall.

I can see the board's skin is stressed where the bolts were broken out of the FoilMount, but the skin is still pretty resilient overall and the board is in good shape.  So long FoilMount!