Foil Box Failure

[supuk]

personally I don't think the carbon is really all that necessary. The problem I see with this type of Tuttle box is you are relying on the end profile of the carbon Tuttle box to bond to which is very small and the failure will probably come when that point goes. What I like to do when bonding things like this is to create a internal fillet between the two parts by chamfering a small amount of foam from around the part and then using some epoxy/fiber paste as the fillet before laminating there quadrupling the amount of surface you are bonding too. 

[blackeye]

I can see how Supuk and Pono's methods add a lot of surface area to bond to. Note however that every photo on this thread shows minimal box to laminate contact area.

I am amazed that large fins, leash plugs and foil mounts don't fail more often. Maybe they do, but maybe better a leash plug than a leg, or a foil mount than a snapped board.

[Beasho]

I can see how Supuk and Pono's methods add a lot of surface area to bond to. Note however that every photo on this thread shows minimal box to laminate contact area.

This might be the case if the Tuttle were a standalone Carbon Fiber box shape.  However the Tuttle is mounted in a Divinycell cassette.  This ostensibly transfers load laterally to Divinycell that is much harder than EPS foam.  The Top and Bottom laminates can then be adhered to a larger surface area of Tuttle and Divinycell rather than just the lip of the Tuttle. 

In my case the entire Cassette sheared in half.  However the wave I got hit by could have broken a regular SUP.   There is only so much you can ask in heavy conditions. 

[blackeye]

I can see how Supuk and Pono's methods add a lot of surface area to bond to. Note however that every photo on this thread shows minimal box to laminate contact area.

This might be the case if the Tuttle were a standalone Carbon Fiber box shape.  However the Tuttle is mounted in a Divinycell cassette.  This ostensibly transfers load laterally to Divinycell that is much harder than EPS foam.  The Top and Bottom laminates can then be adhered to a larger surface area of Tuttle and Divinycell rather than just the lip of the Tuttle. 

In my case the entire Cassette sheared in half... 

I suppose it spreads out the load a bit, and keeps fibre aligned under higher loads better than styrene, but if the Divinycell was seriously strong, it wouldn't have failed there. You should have a mass of white foam firmly adhered to an intact high density foam box with a matching hole in the board.

EDIT - I just went back to the photos - and the mass of missing white foam is what you have on one side. The HD foam on that side is intact. I suppose we don't know whether it was the deck bond or the bottom bond that went first, but the failures of the foams are very different on each side. I also figure that there was some fore/aft force as the damage of the deck laminate is not even. EDIT 2 - the mast was forced backwards is my guess. Interesting that it took some glass with it, likely from the bolt/washer pulling it down. I suspect the fracture in the HD foam is from tension forces and the intact side is mostly compression. Maybe there was a defect too. Maybe there was some Z-axis force too.

... However the wave I got hit by could have broken a regular SUP.   There is only so much you can ask in heavy conditions.

I agree - it broke at its weakest point. After the bolt/washer pulled the deck laminate, likely the deck laminate to box bond second, then something on the bottom (I think you cleared away some of the damaged bits) then sheared through the rather brittle Divinycel with some sideways force on the mast.

Hence my suggestion that a fuse or breaker switch be designed in to the mast which could be easily repaired or reset, rather than the board. Belay that - a jagged stump of a mast could be lethal. Maybe a mount that could release sideways and fore/aft and be clicked back into place. I predict Hobie will be the ones to do this first.

[magentawave]

Good thread. Thanks.

[Surfside]

Mast tracks 4.5oz or fin boxes 3.8oz. Are the mast tracks that much stronger? I've busted mast tracks at Waddell Beach windsurfing. Just curious....

[SUPeter]

I've been making my own Tuttle boxes which up to this point have never failed.  Basically foam with carbon cloth stiffeners which also lock into both hull carbon and deck carbon.  white foam is EPS 2.5 lb, Yellow foam is 2 part polyurethane mixed and poured and shaped.  3K carbon twill.  all wrapped in 6 oz fiberglass x 3 layers.  Insert this cartridge into board. 

[clay]

Has anyone tried this:


or know of any other adjustable tuttle box?

[Beasho]

I've been making my own Tuttle boxes which up to this point have never failed.  Basically foam with carbon cloth stiffeners which also lock into both hull carbon and deck carbon.  white foam is EPS 2.5 lb, Yellow foam is 2 part polyurethane mixed and poured and shaped.  3K carbon twill.  all wrapped in 6 oz fiberglass x 3 layers.  Insert this cartridge into board.

This is crazy (good)!  Do you have any more detailed photographs of the "Tuttle Cassette?"

I can't picture what is going on from the photograph.  Are you building your own female "Tuttle frame" out of carbon somehow and then building the cassette all from scratch?   

[surfcowboy]

Yeah, between Peter and Surffoils the Zone has some pretty serious designers.

[Bean]

Has anyone tried this:


or know of any other adjustable tuttle box?

That's pretty slick, a plate adaptor without extending the mast height.

There are a couple of Tuttle to plate adapters around.  Even a GoFoil seems to be joining the plate camp.

https://blueplanetsurf.com/products/tuttle-to-plate-adapter-by-manta-foils/

https://gofoil.com/adapter/

[SUPeter]

For this Tuttle Box I used two solid sheets of 4mm? carbon sheet purchased from ebay.  This is a prefabricated and cured  gloss carbon layup.  I clamped these  two pieces to either side of the mast insert portion.  The sheets over hang the insert by approximately 1 cm. ie.- They are 1cm larger than the insert, front, back.  The length of the cut sheets is as long as you need to reach from the bottom of board to the top of board. About 5-6 inches for my board.   Use a generous amount of release agent on the mast insert portion.   I then used a mixture of epoxy resin, milled fibers and aluminum powder to fill the uncovered  gap in the front and back of the mast insert.  Once that cure I file to shape and then vacuum bag 3 layers of 3K carbon twill over the sanded  sheets and fill,   to lock it all together.  When done and removed from mast insert,  I then surround this piece in 2.5 lb EPS foam.  Square it up.  Cut v channels out of foam and lay 2 layers of 3K carbon into V channels.  I use separate small pieces for each channel.  I also use melamine boards with release agent to clamp to the sides to maintain a flat shape.   Once cured, fill the V channel gaps with 2 part polyurethane9 4-5 lb density.  Wrap the entire cassete or block in 2-3 layers of fiberglass or 1 layer of 3K carbon and its done.  Yes it takes time, but I find them to be bomb proof.

P.S.  when inserting this cartridge I use a dremmel tool to cut channels in the boards foam,   perpendicular to the cartridge insert, maybe 1-1.5 inches long by 4mm wide.  I then fill these channels with a mix of milled fibers and microballons to offer buttresses to the cassette.  I have always done the same to my side fin boxes and have had great results.  Maybe 5 channels per side.

[SUPeter]

Here is a picture of my 1st one without the carbon top and bottom cover cloth. Only used 3-4 layers of 6 oz glass, top and bottom.   Maybe this will make more sense.

[PonoBill]

Very cool design Peter. When I grow up I'll be that exacting and patient.

[surfcowboy]

Great work man. Really detailed design.