Ou were lucky. Working at shops that sold pb boards, I've seen at least 20 examples of how hitting stuff doesn't work out with pb. Most were crushed back of pb, a couple ripped side to side, several crumpled bottoms adjoining the cracked box, a few incomplete tearouts, and a few I can't recall because all were pre 2000, when I switched shops away from Euro designs.
Of course I seldom dealt with just a lost fin.
Select to expand quoteLeeD said..
Ou were lucky. Working at shops that sold pb boards, I've seen at least 20 examples of how hitting stuff doesn't work out with pb. Most were crushed back of pb, a couple ripped side to side, several crumpled bottoms adjoining the cracked box, a few incomplete tearouts, and a few I can't recall because all were pre 2000, when I switched shops away from Euro designs.
Of course I seldom dealt with just a lost fin.
Nah, I think powerbox are designed to self-destruct this way. The base has a curve in it where it 'rocks' when hit by something and it only has to pivot around one part, the barrel nut.
On the other hand a tuttle fin attachment will be stronger than the tail of the board with nowhere to go. I am sure I have seen photos of the rear of boards absolutely destroyed from prangs with tuttle fins.
As you say, people that just 'lost a fin' are not going to come back with a perfectly fine powerbox equipped board with no damage and then ask you to take a look.
Select to expand quoteLeeD said..
If that's your main concern, use nylon breakaway bolts and a 1.5mm spectra leash.
Nylon bolts!
Surely that would ruin the sailing experience.
Though Formula and your average mug punter wouldn't pick the difference I suppose?
Hey Formula. You were on LHI that time Red dog went missing? We spotted him with binocs, flopping about, up to his thighs in the featureless ocean, 2-3 NM to the NW. After rescue Old Pete manned the dinghy. " We'll go find the fin". A needle in a haystack moment but somehow I got persuaded to man the bow with Old Pete at the helm. "Start looking now". "Yeah right, No , No , No fin, no, no, FFS a jp logo" Just poking out under a piece of coral . If Pete was catholic they'd have made him a saint.
Select to expand quoteFormulaNova said..
Something no one seems to have mentioned is the failures that happen when you hit something immovable like a coral-head.
in my sailing life I have hit coral heads, a concrete channel marker/reinforcement, and sand bars. The first two ended up in breaking the fins. They were powerbox so they broke and just dropped out. In the case of the concrete channel marker, I went back to find the fin at low tide.
They seem to break right through where the barrel nut is and then the fin drops out, leaving the box intact. I have not ever had a damaged fin box or board.
What happens with tuttle? Anyone care to share?
I've had two different experiences.
- one with a carbon fin - the fin sheared off at the point of impact with no damage to the Tuttle box
- two with G10 fins - the fin rotated and the fin head cracked the back of the tuttle box.
If you used one bolt with Tuttle you would have a nice empty hole to thread the 1.5spectra through you could tie one end to the rear strap and the other around the bass insert. Now when you hit something the bolt breaks not your board and you don't loose the fin.
im sold, powerbox is crap we all need Tuttle.
now do you leave the free net or rear bolt out?
Select to expand quoteIan K said..
Hey Formula. You were on LHI that time Red dog went missing? We spotted him with binocs, flopping about, up to his thighs in the featureless ocean, 2-3 NM to the NW. After rescue Old Pete manned the dinghy. " We'll go find the fin". A needle in a haystack moment but somehow I got persuaded to man the bow with Old Pete at the helm. "Start looking now". "Yeah right, No , No , No fin, no, no, FFS a jp logo" Just poking out under a piece of coral . If Pete was catholic they'd have made him a saint.
That's a good memory! Pete would have to be the best man for finding things, even without a metal detector 
That was a good trip, and a surprisingly good destination for that time of the year.
A bit different to my own story. I was sailing in Mackay and asked a local (kitesurfer) if there were any hazards to worry about. No, it's fine, just stay around the river mouth.
So I did, and clipped a fin against something submerged. I had no idea what it was. When I went back at low tide I found that the submerged object was one of dozens of huge concrete structures placed at the rivermouth to stop the rivermouth shifting each year, and each was higher than head height. I am so glad I didn't come off as hitting one of those and it would have been lights-out. The tide varies so much that they go from being high and dry on the sand to being completely submerged.
At least I found the fin easily, but it was a long long walk there and back as anyone that sails Mackay would know.
Select to expand quoteFormulaNova said..
A bit different to my own story. I was sailing in Mackay and asked a local (kitesurfer) if there were any hazards to worry about. No, it's fine, just stay around the river mouth.
So I did, and clipped a fin against something submerged. I had no idea what it was. When I went back at low tide I found that the submerged object was one of dozens of huge concrete structures placed at the rivermouth to stop the rivermouth shifting each year, and each was higher than head height. I am so glad I didn't come off as hitting one of those and it would have been lights-out. The tide varies so much that they go from being high and dry on the sand to being completely submerged.
And the moral of this story - never trust a kitesurfer
Select to expand quoteFormulaNova said..
Something no one seems to have mentioned is the failures that happen when you hit something immovable like a coral-head.
in my sailing life I have hit coral heads, a concrete channel marker/reinforcement, and sand bars. The first two ended up in breaking the fins. They were powerbox so they broke and just dropped out. In the case of the concrete channel marker, I went back to find the fin at low tide.
They seem to break right through where the barrel nut is and then the fin drops out, leaving the box intact. I have not ever had a damaged fin box or board.
What happens with tuttle? Anyone care to share?
All the tuttle box failures I have had (3) have resulted in board or box damage. My powerbox experience was like yours (2), no damage except to the fin head. In my experience the US/E box is the best for running into things without damage.
The Tuttle head wont rotate out of the box cleanly because of its shape. You can shave a few mm off the top half of the front edge so that it can rotate backwards with a good chance of leaving the box intact. But then the job of fin retention goes more to the sides of the box rather than the front and back edges. If you were anal about it you could put some packing in the box to compensate.
I only did that to one fin many years ago and never hit anything with it anyway, but when I tested it by hitting it with a shoe it worked as designed.
Select to expand quotePaducah said..
First off, what Ben said. Because of the straight fore and aft edges and high friction of the sides of the tuttle design (unlike the conical sides of the Powerbox), it's easier to align with two screws.
I'd write more but your ego is getting in the way of actually having a constructive discussion. Ad homimen attacks prove nothing and are childish. Nothing you've written disproves my points other than saying a crappy fitting tuttle fin will be prone to spin out. Because of my foiling misadventures, I've learned more about tuttle box construction, dimensions (I can quote most of them from memory) and characteristics than I would have preferred.
Maybe sit down and actually think about what loads are on the tuttle box, their direction and their magnitude. It requires zero think tank. It does require your looking down at your feet when you sail, your sheeting angle and body position regarding the sail. Then think about what forces the deep tuttle was meant to address by it's increased height over the regular. After all that, I'm happy to listen why you think that the fore/aft loading on a conventional finned tuttle box is significant. If any of this requires a think tank, just stick with being a better windsurfer than me.
- signed, Paducah. Happily sailing tuttle boxes in lakes and oceans for 26 years.
PS, I'm well aware of how a trim box works as I dropped a trim box fin into a deep lake having forgotten to tighten the single bolt 20 years ago.
This text reminds me a manager on typical engineering meeting at my work. The manager has no understanding on engineering specifics but always talks the most. The management talk has no specifics, but only generic basswoods.
I looked other comments of Paducah and got an impression that he/she/? is actuality working on this forum since Dec 2016 while taking care of his old mother and 8 siblings from home. I did not see a single post with specifics to add value to the issues posted. All his/her/? comments are generic an mostly in a form of giving a strong suggestion or critics without any demonstrated practical knowledge in the subject. I want to think that I am mistaken. But I still want to see any comment from this person that was informative and interesting to read or a practical windsurfing related question that would be interesting to discuss.
In regards to 2 screws in Tuttle.
I used one screw in small Tuttle, just because I did not have the second screw. It worked ok for my level, short time and light wind. I put the one screw to the front so it hold the fin better when it hits the ground. But the bottom flat of the fin head is not flash with the board surface. It may be not so good for someone who can feel the difference in drag. An my fin fits very precise into the box. But I have seen people using tape to get a better fit. For the loose fin two screws are indeed the must. One time I did not have the right screw length of Power Box. The screw was too long. The fin was little wiggling. I lost the fin - never found. One time I witnessed Tuttle fin failure from side load. It sounds like a gun shoot, while the board was a mile away. The rider says it was more awesome than a spinout experience. With offshore wind it was difficult to return.
Tuttle box has two tapered surfaces: on the front and on the back. It needs two screws to mate the box on these tapered surfaces. It means that tightening the both screws makes the assembly more stiff.
But poor skill windsurfers like myself (35 years) and Paducah (20 years) can safely use only one screw without noticing the difference on lakes or in the sea.
In regards to US Box. I have known surfers (wave surfers without sail) using small foils attached to the fins for US Box. US Boxes are very common on SUPs and surfboards. I have even seen Futures boxes using fins with foils.
It is interesting why is it even discussed. Use one screw or two screw if you like. There is a fin design with a rotating connection to the box on another forum. Apparently, some people like fin to be very loose and see advantages in it.
Welcome to the world of management.
Promoting /or whatever it is, using 1 screw , thereby reducing the % of tightening/ secure force to 50%.
Would the engineer in you use 50% of the lug nuts on a wheel ?
The Fanatic Blast originally had a powerbox, as is typical for freeride boards. However, the Blast works perfectly fine with race sails, and can be sailed quite fast. Some guys who did so found that the fins broke off at the base, without hitting anything. I've seen it happen once myself. A slalom sailor that this happened to said it was the torque that caused it. Last time I tried a Blast, I was quite amazed how easy it was to get the board flying on the fin - easier than slalom boards, at least for me. So there can definitely be a lot of pressure on the fin.
So Fanatic decided to change the box to a tuttle box. In the larger sizes, it's a foil-ready box, so that probably was another reason for the change. But I think the tuttle is also used for the smaller sizes that don't have foil boxes.
The only fins I ever had breaking at the base in the middle of a run were also powerbox fins. But they were rental fins at a place were ground contact at speed was quite common.
Select to expand quoteboardsurfr said..
The Fanatic Blast originally had a powerbox, as is typical for freeride boards. However, the Blast works perfectly fine with race sails, and can be sailed quite fast. Some guys who did so found that the fins broke off at the base, without hitting anything. I've seen it happen once myself. A slalom sailor that this happened to said it was the torque that caused it. Last time I tried a Blast, I was quite amazed how easy it was to get the board flying on the fin - easier than slalom boards, at least for me. So there can definitely be a lot of pressure on the fin.
So Fanatic decided to change the box to a tuttle box. In the larger sizes, it's a foil-ready box, so that probably was another reason for the change. But I think the tuttle is also used for the smaller sizes that don't have foil boxes.
The only fins I ever had breaking at the base in the middle of a run were also powerbox fins. But they were rental fins at a place were ground contact at speed was quite common.
So is the point here that Fanatic installed the wrong box ? Or that tuttle is much stronger ?
And hitting the ground at speed is bad ?
No winners in that old war, we even have more different box types to choose from now days.
Ahh! Just use what you like and get on with it.
I have all Tuttle.
But I do need to build a very strong and also adjustable fin box for my planned new Tandem Slalom type board. And that presents a challenge.
It has to be very strong, to handle the load of two sailors driving hard with around 13-15sq m of total sail. So it will be deep and parallel sided for strength. This suggests a Tuttle box. But it will have to be adjustable through a range of about 3 Tuttle base lengths.
Why, because in past Tandem projects we found that (a) it was impossible to accurately determine the best position for the fin before sailing the thing. (b) The best position for the fin changed with the wind strength, position of the sailors and angle of course to the wind (for a speed tandem) (c) The position was also different depending on the rake of the fin. (raked weed fin has to go further forward)
The main reason this is quite critical is that with two sailors, the balance of the drive can't be altered when sailing as much as a single sailor can do it through sail rake, foot and mast pressure.
In the current (1991) speed tandem we used a very heavily reinforced Chinook US box. But that won't cut it for this project.
testing when new in 1991:
Add another forgotten trimbox into the tandem... a trimbox. Made to be adjustable, and you can make you own version to have as many positions as you want!
I think some sport of tuttle finbox inside a finbox would be better though with spacers, but sounds like there will be a bit of work in any solution you go with.
Adjustable fin box, speed tandem ?
How do the screws line up from the top deck to the fin..when its moved in they box ?
Select to expand quoteforceten said..
Adjustable fin box, speed tandem ?
How do the screws line up from the top deck to the fin..when its moved in they box ?
Slot... not holes. Or multiple-holes.
Select to expand quotemathew said..forceten said..
Adjustable fin box, speed tandem ?
How do the screws line up from the top deck to the fin..when its moved in they box ?
Slot... not holes. Or multiple-holes.
Or, becase the fin and packing pieces are doweled together, then multiple holes in the packing pieces and fin, so that any configuration suits the fixed location of the bolts, preferably at the ends of the slot.
Select to expand quoteFormulaNova said..
Add another forgotten trimbox into the tandem... a trimbox. Made to be adjustable, and you can make you own version to have as many positions as you want!
I think some sport of tuttle finbox inside a finbox would be better though with spacers, but sounds like there will be a bit of work in any solution you go with.
Yes, we had thought of both of those solutions.
Trimbox would be a good one, but unfortunately, trim box based fins are very hard to get these days, and we don't already have any. 
Box within a box is still on the cards. But you are correct. Both solutions will be time consuming to build. I think the long Tuttle is the simpler to build though.
I just pulled up the GPS file for the 2006 tandem speed run. Craig Hollins and I actually got 37.08 Knots 2 second in that Video, with not a lot of wind (maybe 26-27 knots?). 35.4 Kts for the 10 second. Both of us on 5.8's. Thanks to Tim from the MI crew for the video. 
Makes me think about maybe building a more modern speed Tandem as well. 
Unfortunately, the dune build up at Sandy Point would make sailing it a lot harder, which is also why we want to build the larger 'slalom' tandem, (70-75cm wide instead of 50cm wide!) but LG would be a great possibility with the right fin. We tried the old speed tandem a couple of times at LG recently, but lack of being able to fit a 'Delta' type fin in the US box was a huge problem.
Select to expand quotemathew said..forceten said..
Adjustable fin box, speed tandem ?
How do the screws line up from the top deck to the fin..when its moved in they box ?
Slot... not holes. Or multiple-holes.
Slot would have to be in the board deck . Additional fittings in the fin or packing pieces , could work, with care as to position .
Neither sound very peachy .
