I'd definitely like to see how that Radix box is constructed before sending the idea to my mental scrap heap.
Again considering that I sailed months on a shallow tuttle with zero taper engagement and a very dodgy DIY flange installed on a deep tuttle mast with absolutely no damage to the board makes me think twice about what actually breaks boxes.
Meanwhile I've got a formula board with a split deep tuttle that was used for a limited amount of time with a mast that has no flange using the maximum taper engagement method. That's a box which was tied into the deck as well FYI.
Yes, there was a model of Starboard formula that was famous for breaking its tuttle box with a foil. All over the world this happened. Well known problem. Most others have performed well.
Since about 2018 manufacturers have not only gone to extra-reinforced tuttle boxes (you can see them listed for builders), but North Pacific, for one, adds extra longitudinal stringers bonded to the tuttle box and buried in the foam to greatly reinforce the fore and aft rocking strength.
In the old days with formula fins, it was side forces that loaded tuttle boxes.
Now with foils it is the fore and aft rocking forces that dominate. Whether the box depends on inside roof contact or rounded taper contact, the box has to carry fore and aft rocking loads. Mostly fore, as you can see by the geometry of lifting wing in front of mast, and by the fact that it is always the front screw that comes loose.
Never had a tuttle screw come loose with good roof contact. Never had one stay tight without it, including on a foil box I installed where I decided to rely on the tapers.
Which is why the Sailworks crew used to instruct to rock-tighten-rock-tighten-rock-tighten...etc...until everything is completely tight. I never have the front screw come loose this way. 8 years of front and back rounded taper contact has been the ticket. Never needed, nor wanted, inside roof contact.
No need for that, just ensure contact where the manufacturers recommend: a flat surface inside or outside the box. Rather than grunting your foil on and off eventually splitting the box if you're putting any real force into it.
A slow freerider would probably go years before then but a performance foiler (if they were foolish enough to not follow manufacturer's instructions) it wouldn't last long being abused like that.
I don't know about that. The entire Sailworks crew has been doing this since 2016 with mostly Roberts and North Pacific boards. I have never heard of a failure for those guys/gals. Look at the Tuttle design drawing. It specifies width, taper angle, taper radius, but does not specify height. When the board guys buy reinforced boxes they come about 5" high. They install them into their boards then saw off the tops to make it flush with the top skin. Then glass and carbon it all in. The resulting inside height varies with the board thickness back there. You can then mount any tuttle fitting you want. As long as you seat the rounded tapers you don't depend on inside roof contact. The inside heights of my Mike's Lab, Roberts, and North Pacific boards vary from 2-3/4" to 4". I can mount the same Moses/SAB and AFS foils (no flanges) into any of them and ensure a tight fit with the rocking method. After 400 sessions (I'm a nerd--I keep a log), I have never had a failure. I weigh 200 lb.
By the way, rocking does not crack the foil-ready reinforced boxes. They are too strong for that.
The inside roof contact design is fine as long as you make sure you are matching the board with the correct foil. My Moses/SAB and AFS stuff does not match with any boards, so I depend on the rounded taper contact method. It works.
If it's not jamming on the tapered front and rear properly, and u rely on roof contact then it is loading the screws too much and they tear thru the rear chimney bottom. Same as with silly shimming.
Segler is correct. Tighten and rocking seats it correctly. I fix those problems often on IQ boards where people don't use the DT taper as intended
By the way, I also have an Exocet foilboard with a box that people use for inside roof contact, but ONLY IF THEY MOUNT A COMPATIBLE EXOCET FOIL. Since the box is tuttle anyway (they all are), I can mount my Moses/SAB and AFS (no flanges) foils into it just fine using the rock-tighten method. It works fine. No failures. No inside roof contact.
This board has those chimneys on top to accommodate the inside roof height they want for their own foils. I never depend on the chimneys. Instead I use a big aluminum sheet rectangular washer on top to spread the load onto the top skin, where it belongs. I got that idea from some of Sailworks' customers way backin 2017.
