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LeeD said..
Perhaps we need less feedback from engineers and theorists, and more from windsurfers with experience.

But that's not how seabreeze works.

Problem is there aren't 2 identical boards with different fin boxes fitted to try back to back. The screws aren't doing anything to stiffen up the connection it's depth and surface area that gonna make it stiff and both Tuttle and powerbox have pretty much the same surface area in the Box.

Try sailing with loose finscrews, and tell us it don't matter.

I suppose there are two questions here .
1 , what is ultimately the strongest box before failure and ,
2 , which box creates the tightest fit so you dont get fin wobble .
I would think both boxes are similar in resistance of getting ripped out of the board . Possibly less chance of splitting a PB box when hitting something . Stripping one nut would need less force to let the fin come out than having to strip two nuts ???
The tuttle fin only wedges in on the ends so if there is any gap on the sides it will wobble .
The PB fin wedges on all sides and sits on the bottom so if the bottom mating area is a bit high it will also wobble .
A deep tuttle probably wins because it has a lot longer side to side mating area that holds the fin reducing wobble for the same amount of gap . A normal tuttle should be similar to a PB.
From an engineers point of view , and , someone who uses both boxes

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LeeD said..
Try sailing with loose finscrews, and tell us it don't matter.

The screws only hold the fin in the box they don't add to stiffness. At least they shouldnt if the fins a good fit

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Imax1 said..
I suppose there are two questions here .
1 , what is ultimately the strongest box before failure and ,
2 , which box creates the tightest fit so you dont get fin wobble .
I would think both boxes are similar in resistance of getting ripped out of the board . Possibly less chance of splitting a PB box when hitting something . Stripping one nut would need less force to let the fin come out than having to strip two nuts ???
The tuttle fin only wedges in on the ends so if there is any gap on the sides it will wobble .
The PB fin wedges on all sides and sits on the bottom so if the bottom mating area is a bit high it will also wobble .
A deep tuttle probably wins because it has a lot longer side to side mating area that holds the fin reducing wobble for the same amount of gap . A normal tuttle should be similar to a PB.
From an engineers point of view , and , someone who uses both boxes

The deeper the box and the more mating area the better. But how stiff does it really need to be. What sort of load really get put into the fin box, guessing it's not that much, 50kg?

^^^
I think it could be more . Heavy me pushing extra hard between swell gulping for upwind with a 52cm fin . Thats a lot of leverage .

Has anyone broken any box from just sailing with sideways force ?

I've repaired a few chinnook US strong boxes that snapped the peg, then rolled. But not sure if that was just sailing load.

How big a fin can a US box take? 30 cm max?

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philn said..
How big a fin can a US box take? 30 cm max?

I run a 42 cm in my Race-board US box and i do wonder about it . But i only use it in under 13 kts and its not the kind of board to really push on the fin. I have no idea how strong it is . The fin does flop from side to side about 2cm at the tip .

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Imax1 said..
^^^
I think it could be more . Heavy me pushing extra hard between swell gulping for upwind with a 52cm fin . Thats a lot of leverage .

Has anyone broken any box from just sailing with sideways force ?

Yes, years ago about 1993 on a barry Taylor thruster with a hand made fiber glass slot fin, mast high steep perfect bowl section, felt a bit of slide on a big bottom turn which was strange for that board then went to do a big slash off the top and it just went crunch it was the most hardcore spin out over the falls to snapped mast I've ever done! Fin and box were laying flat still attached.

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Imax1 said..

philn said..
How big a fin can a US box take? 30 cm max?

I run a 42 cm in my Race-board US box and i do wonder about it . But i only use it in under 13 kts and its not the kind of board to really push on the fin. I have no idea how strong it is . The fin does flop from side to side about 2cm at the tip .

2 cm of wobble might be ideal? Who knows? The assumption being made here is that 90 degrees is the optimim angle. 90 degrees does decouple the lifting force of the hull from the lateral force of the fin. This simplifies control but at any instant the net hydrodynamic force on the hull is all that matters and generating this with two lifting elements at 90 degrees is not the most efficient. Years ago I boxed a fin with a 17 degree tilt. It sailed OK on both tacks. I thought relieving the hull of a little work might be advantageous.

Foil boarders are leaning towards generating the required hydrodynamic lift with one element. They crank it quite a ways to windward. The tan of the angle times the total lift on the foil would be close to the 25kg sideways force needed to counteract the sail. It's likely that the windward attitude of a serious windfoiler allows them to use very little angle of attack on the mast.

As materials get higher tech we might find the masts on foils get thinner with shorter chords. They only need to have a structural function.

Anyway my conclusion after sailing a 17degree leaning fin was don't worry if it wobbles a degree or two due to a loose fit. You'd not pick the difference.

Nobody has mentioned it yet, unless I missed it, so I will.
I hate both Tuttle and Power boxes for one reason only, the board manufacturers who install those assume that everybody who uses that board, likes to have the fin in the exact same place. No need for forward or back adjustment, because we know best.
BS, we don't all weigh the same, and we don't all have the same sailing style, or needs.
So I've always considered it a form of arrogance on the part of the board builder, who uses those for mass consumption.

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LeeD said..
Try sailing with loose finscrews, and tell us it don't matter.

Sail with one tuttle screw in vs two and tell us it matters (assuming screws in each case are snug and sound)

Totally matters to a good sailor. Fin shifts held with one screw and spinout can occur.

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LeeD said..
Totally matters to a good sailor. Fin shifts held with one screw and spinout can occur.

Um... how? All of us who have to hammer our foils out of our tuttle boxes are wondering... (And remember that my precondition was that the single screw remaining was snug and sound.)

And why doesn't this happen with the other one screw systems Power and Trim box?

Less engineer, more windsurfer is required to answer your question. Ask any good windsurfer to use ONE bolt on his tuttle box.

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LeeD said..
Less engineer, more windsurfer is required to answer your question. Ask any good windsurfer to use ONE bolt on his tuttle box.

So give me the windsurfer answer to why it's different from other one bolt systems? I'll listen. I was a liberal arts major any way.

If the bolts are adding to the stiffness then the fin doesn't fit right.

That's where actual windsurf experience comes in, over useless theoritical think tanking.
Power and Meritex is centered single screw. Centered meaning no shift and balanced loading.
Trim is 1 screw and holding tab, for 2 points retension.
Did you know Tuttle is actually designed for 2 screws, 1 back and one front? Like any other part designed for TWO screws, using ONE compromises strength and holding power allowing shift/movement causing excessive point loading which stresses the system. Why do you think Tuttle systems are generally a tight fit? And TWO screws are used by all good sailors..except you?

agree that due to the placement of the screws Tuttle needs 2 to fit the fin but they dont add to stiffness once the fin is in. One bolt in the centre would work just as well.

Only advantage with 2 bolts on Tuttle is it allows you to pull the fin in more at one end than the other to get is to sit flush.

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Mastbender said..
Nobody has mentioned it yet, unless I missed it, so I will.
I hate both Tuttle and Power boxes for one reason only, the board manufacturers who install those assume that everybody who uses that board, likes to have the fin in the exact same place. No need for forward or back adjustment, because we know best.
BS, we don't all weigh the same, and we don't all have the same sailing style, or needs.
So I've always considered it a form of arrogance on the part of the board builder, who uses those for mass consumption.

This only makes sense if you want to move the fin, as a priority over strength.No way a USBox is as strong as a powerbox , so the reason the powerbox is installed is a longer fin is required. USBox fins are limited to around 30cm, due to strength in the box.

The fin box placement by the manufacturer, is but one of the items they place , mast track, footstrap inserts, and of course the shape, so a certain amount of trust is necessary.
From your neck of the woods, Mike Ziecek AFAIK uses tuttle on near everything

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LeeD said..
That's where actual windsurf experience comes in, over useless theoritical think tanking.
Power and Meritex is centered single screw. Centered meaning no shift and balanced loading.
Trim is 1 screw and holding tab, for 2 points retension.
Did you know Tuttle is actually designed for 2 screws, 1 back and one front? Like any other part designed for TWO screws, using ONE compromises strength and holding power allowing shift/movement causing excessive point loading which stresses the system. Why do you think Tuttle systems are generally a tight fit? And TWO screws are used by all good sailors..except you?

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.

Well, keep sailing your boards with one screw tight, the other loose or missing, and good luck to you.
Now if you do decide to snug BOTH screws, well, welcome to the real world, away from the think tank world.

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forceten said..

Mastbender said..
Nobody has mentioned it yet, unless I missed it, so I will.
I hate both Tuttle and Power boxes for one reason only, the board manufacturers who install those assume that everybody who uses that board, likes to have the fin in the exact same place. No need for forward or back adjustment, because we know best.
BS, we don't all weigh the same, and we don't all have the same sailing style, or needs.
So I've always considered it a form of arrogance on the part of the board builder, who uses those for mass consumption.

This only makes sense if you want to move the fin, as a priority over strength.No way a USBox is as strong as a powerbox , so the reason the powerbox is installed is a longer fin is required. USBox fins are limited to around 30cm, due to strength in the box.

The fin box placement by the manufacturer, is but one of the items they place , mast track, footstrap inserts, and of course the shape, so a certain amount of trust is necessary.
From your neck of the woods, Mike Ziecek AFAIK uses tuttle on near everything

I never said that US boxes are stronger, not my point, but I only ride on the ocean, so those are what I prefer, even though some wave boards come with no fin adjustments (Power box usually).
Also, those other items on a board, that you mentioned, all have some adjustment, mast track, not mast hole mount, multiple footstrap inserts, not just one set. One of my JP boards has footstrap plugs, not just forward or back, but also inboard or more outboard by the rails.
The more adjustments that any given board has, the more I will be attracted to it. The same with sails, the wider the range thru tuning, the better I'll like it.

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philn said..
How big a fin can a US box take? 30 cm max?

I asked Francisco Goya if i could use a 35cm US slalomfin in my Goya One Freewave 116 with a 7.2 sail, 90 kg rider.
He told me it will work and the box will be strong enough.

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Mastbender said..

forceten said..

Mastbender said..
Nobody has mentioned it yet, unless I missed it, so I will.
I hate both Tuttle and Power boxes for one reason only, the board manufacturers who install those assume that everybody who uses that board, likes to have the fin in the exact same place. No need for forward or back adjustment, because we know best.
BS, we don't all weigh the same, and we don't all have the same sailing style, or needs.
So I've always considered it a form of arrogance on the part of the board builder, who uses those for mass consumption.

This only makes sense if you want to move the fin, as a priority over strength.No way a USBox is as strong as a powerbox , so the reason the powerbox is installed is a longer fin is required. USBox fins are limited to around 30cm, due to strength in the box.

The fin box placement by the manufacturer, is but one of the items they place , mast track, footstrap inserts, and of course the shape, so a certain amount of trust is necessary.
From your neck of the woods, Mike Ziecek AFAIK uses tuttle on near everything

I never said that US boxes are stronger, not my point, but I only ride on the ocean, so those are what I prefer, even though some wave boards come with no fin adjustments (Power box usually).
Also, those other items on a board, that you mentioned, all have some adjustment, mast track, not mast hole mount, multiple footstrap inserts, not just one set. One of my JP boards has footstrap plugs, not just forward or back, but also inboard or more outboard by the rails.
The more adjustments that any given board has, the more I will be attracted to it. The same with sails, the wider the range thru tuning, the better I'll like it.

Nobody said you did say PB VS USBox strength .My point is USBox is only useful for smaller fins, ergo PB or tuttle are needed for longer fins. Most slot box have no adjustment , those that install ,PB in a wave board are nuts.
Your point on movement , I did not consider, you are correct .

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?

If that's your main concern, use nylon breakaway bolts and a 1.5mm spectra leash.

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LeeD said..
If that's your main concern, use nylon breakaway bolts and a 1.5mm spectra leash.

or a powerbox