Hi all!
I love formula sailing. I have an old Starboard 2008 162l Wood. It has a deep tutle box. Is it possible to use it also with a foil? Does it need a reinforcement?

Thousands of formula boards in Europe have been used with foils with no problems.

Yes, there have been a few (very few) instances of failures in the finboxes. Formula boards generally have really strong finboxes in order to carry 70 cm long fins with really large fin loads. Yes, those loads are sideways while foils add a fore and aft component of force due to the lift of the main wing.

I have three formula boards that I use for foiling. Two have stock finboxes, while one has a relocated and reinforced finbox. All have performed flawlessly. I weigh 195 lb.

Go for it. You will find that the formula board is a really good platform for foiling. You will also find that you probably want to move the footstraps more inboard since your foiling stance is more upright. That said, you can always foil strapless until you figure out where to put your feet.

If you are nervous, use a leash from the top of the foil to a back footstrap.

Jgsev, I had the same board and it was good for 10 or so sessions before the foil mast eventually drove up through the deck of the board. If you really want to hang on to the board in the longer term you may wish to look at reinforcement.

Deep tuttle fin boxes are designed to tighten the fin in the box via the tapered front and back edges.

Fins do not load those edges up at all but foils place load on the front taper if they do not have a flange that spread's the load onto the bottom of the board and or they do not make contact with the top of the fin box. That load can chew out the front taper in a tuttle box if that front taper is bearing the brunt of it, race foils do this more so than other foils.

I have three formula board, used them with a foil with a flange with zero problems, changed to a race foil with no flange and instant problems. Two of those boards have now modified fin boxes to accomodate the race foils so that the load is now taken up by the top of the fin box and reinforced deck.

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cammd said..
Deep tuttle fin boxes are designed to tighten the fin in the box via the tapered front and back edges.

Fins do not load those edges up at all but foils place load on the front taper if they do not have a flange that spread's the load onto the bottom of the board and or they do not make contact with the top of the fin box. That load can chew out the front taper in a tuttle box if that front taper is bearing the brunt of it, race foils do this more so than other foils.

I have three formula board, used them with a foil with a flange with zero problems, changed to a race foil with no flange and instant problems. Two of those boards have now modified fin boxes to accomodate the race foils so that the load is now taken up by the top of the fin box and reinforced deck.

Good information to know.

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cammd said..
Deep tuttle fin boxes are designed to tighten the fin in the box via the tapered front and back edges.

Fins do not load those edges up at all but foils place load on the front taper if they do not have a flange that spread's the load onto the bottom of the board and or they do not make contact with the top of the fin box. That load can chew out the front taper in a tuttle box if that front taper is bearing the brunt of it, race foils do this more so than other foils.

I have three formula board, used them with a foil with a flange with zero problems, changed to a race foil with no flange and instant problems. Two of those boards have now modified fin boxes to accomodate the race foils so that the load is now taken up by the top of the fin box and reinforced deck.

Interested to know how people are measuring how much to pack the box to make the head have good contact at the ceiling and still hit the taper lock well? Plasticine to provide a visual after screwing it in?

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Mark _australia said..
Interested to know how people are measuring how much to pack the box to make the head have good contact at the ceiling and still hit the taper lock well? Plasticine to provide a visual after screwing it in?

Use Selleys Aqua knead it. It's plasticine until it sets. Bolt it up tight with glad wrap or mould release around the head. Don't put too much in. I only do the front corner where the compression under load will be. The back corner's not going to load up unless you hit a sandbar at speed. ( maybe do the back corner behind the bolt then). Keep winding the bolts back and forward a bit while the kneadit's setting. The kneadit can come loose after a season or so, so check it's still there every now and then. I've been able to chisel it out when fitting a new mast and start all over again.

Don't pack it. Like cammd says above, you want the DT fitting to fully seat against the front and back rounded tapers. That is the only way to ensure zero movement. Movement will destroy the box. You want a gap on the top inside to ensure full seating.

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Mark _australia said..

cammd said..
Deep tuttle fin boxes are designed to tighten the fin in the box via the tapered front and back edges.

Fins do not load those edges up at all but foils place load on the front taper if they do not have a flange that spread's the load onto the bottom of the board and or they do not make contact with the top of the fin box. That load can chew out the front taper in a tuttle box if that front taper is bearing the brunt of it, race foils do this more so than other foils.

I have three formula board, used them with a foil with a flange with zero problems, changed to a race foil with no flange and instant problems. Two of those boards have now modified fin boxes to accomodate the race foils so that the load is now taken up by the top of the fin box and reinforced deck.

Interested to know how people are measuring how much to pack the box to make the head have good contact at the ceiling and still hit the taper lock well? Plasticine to provide a visual after screwing it in?

How we made made a spacer was to put the foil in the box tensioned in to refusal, then removed the bolts and poured a silicone moulding material in through the bolt holes with the board on a slight back wards tilt (you have to plug up the rear hole so it doesn't flood out). you can then push it out when set and either take a female mould off of that to make a hard usable copy, or use it as a guide to make one up by hand.