So sick !!
Since the adjustable tuttle discussion. I always wondered if the spacer was creating fore/aft flex of the mast. So you said that you can’t feel the difference in the different plastic ones that you made. Have you tried other material ?
yes I tried several materials and put the mast in the middle of my long box. What I found is that the tuttle is wedged so tightly by the screws pulling it up into the tapered slot, there is significant preload pressure on the spacers. Once it is wedged in, it isn’t going anywhere. I didn’t measure stiffness by hanging a mass, that could be done, but just by riding I’m not noticing it. I’m a big guy 205lbs plus wetsuit and this is a 9’4" SUP board. And for these tests I’m riding waves and pumping back out, which puts plenty of stress on the link to the board.
So far I tried from least stiff to most stiff, 50% rectilinear fill PLA, solid infill PLA, solid infill PETG, solid infill PLA-CF. Those range in stiffness from about 1.5 to 4 GPa so a pretty wide range of stiffness.
In production these spacers would probably be made with either injection molding or bulk molding process in Nylon Pa6-6 with 20-30% glass fill which is more like 6-9Gpa, but can be as high as 16GPa.
Too much detail? maybe
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Never too much !
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Look super nice!Mabey can improve and create an angel inside?
From my experience plastic always compress in this high stress area
Perhaps making from G10 or carbon can solve
I had a chance to finally listen to the full Generic Foiling podcast with Dave Kalama, at the end he did NOT mince his words.
02:10:42,240 → 02:10:46,960
“But the efficiency of a tuttle system is superior to a plate, there’s no question.”
- Dave Kalama
Meanwhile I took a stab at calculating the additional drag associated with the Plate head on an Axis system.
A useful sanity check is that the plate face is 120 mm × 8.3 mm, or about 996 mm². A 19 mm mast has 19 mm² of frontal area per millimeter of length, so if the plate were as efficient as the mast airfoil, it would still equal about 5 cm of mast drag just from area alone.
The real plate is not as efficient as the mast. Even with the slots sealed, the rounded plate body is probably somewhere around 10–20 cm of equivalent mast drag, depending on how cleanly the flow stays attached.
The open slots are where things get ugly. They are only about 15% of the exposed face area, but because they face directly into the flow, they behave like little ram scoops and separation cavities.
That likely pushes the total plate penalty into the range of
→ 50–70 cm of equivalent 19 mm mast drag.
The above calculations were done considering that the slots act like scoops and have an enormous drag profile.
Vs an otherwise efficient Airfoil shape with a drag coefficient ~ 0.05. If the Mast Plate acted like a flat plat (e.g. no rounded edge) the effective 19 mm mast addition would be 1.3 meters.
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Yeah, won’t the plate only offer that resistance when going slow. Like when paddling up, getting speed up on a wing or parawing. Then you are out of the water and dealing with just the mast and foil.
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I don’t even know where to start here. This is pretty much useless information. If you’re gonna use an LLM to research this, use it to learn how to do it properly instead of spreading misinformation.
Even well setup CFD will probably struggle the difference in drag between tracks and a plate. Around the tracks/plate you will have aerated, highly turbulent flow, ventilation, complex geometry, and you’re operating at the water’s surface adding an additional challenge to calculation.
I don’t think anyone is arguing that there is no difference in drag between a plate and Tuttle as far as drag on the water.
Maybe someone with a foil assist can measure power required between a plate and Tuttle with the same board and foil?
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All foil assists only work with tracks, maybe except the Stoke, but more drag issues with that one.
I think this numbers are not realistic.
Pretty easy to test though, just fair those screw holes with plasticine putty and go ride…i predict the “felt’” difference will be zero.
The lack of scientific rigor in that dismissal is remarkable — and it ends up reinforcing the conclusion rather than challenging it.
Look at the attached graphic (“Shape Is Everything” - Reposted). The drag differential between an efficient airfoil and a cylinder is not subtle — it’s 26×. You don’t stumble into low drag by accident. Any deviation from that optimized shape is penalized immediately and severely. Additional curves, edges, cavities, and scoops don’t take you from good to mediocre. They take you from bad to catastrophic.
The math doesn’t require CFD or an LLM. It’s dimensional analysis with published Cd values — the kind of problem a freshman engineering student solves by hand as one question in a 20-question problem set. Frankly I’m kicking myself for not working through it sooner. And frankly, those in the industry who do have CFD capability should be asking why this was never called out.
Here’s the analogy that should reinforce the basics of shape and drag: look up why a cup anemometer is shaped the way it is. The hollow cup face has a Cd of 1.42. The convex back has a Cd of 0.38. That 3.7× asymmetry is what makes the shaft rotate — the drag difference between a concave scoop and a smooth convex surface is so large and so reliable that we’ve built precision scientific instruments around it for 600 years.
Now look at your bolt slots. Open cavities facing directly into the flow — ram scoops by geometry. Then consider that the trailing edge has the same slots facing rearward, acting as drag cups on the back side too. The anemometer doesn’t care whether the flow is aerated, turbulent, or near a free surface — the hollow face always wins. Neither do your slots.
The complexity raised — aeration, ventilation, surface effects — affects the precision of the number, not the direction.
The plate is not close to the mast in drag. It isn’t close to close. The only question is whether the penalty is 40cm of equivalent mast drag or 70cm. Either answer makes the Tuttle case.
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Reminds me of these shirts at Univ of Chicago: “That’s all well in good in practice … but in theory!”
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you’ve modelled it with empty slots, they have screws?? Moot point here
What you can feel is the big thumb screws
Agree, and my take for AI: it’s good at code, it struggles with physics, it is telling you what you want to hear. Get it to write code to do physics. Incl CFD, stretches of imagination become explicit
Share the code, we can see the assumptions. We can empirically validate assumptions.
Around the tracks/plate you will have aerated, highly turbulent flow, ventilation, complex geometry, and you’re operating at the water’s surface adding an additional challenge to calculation.
It is kind of fun to debate stuff like this on the internet. I tried to make some calculations myself, and I tried to talk to a few different people who really know about how to run CFD about it. All of them said basically the same thing Kane says: the flow at the base of the mast is almost impossible to model because it is developed complex turbulent and aerated flow.
Beasho, I do appreciate your advocacy of tuttle. I’m a tuttle champion as well. I think we want the same thing - for manufacturers to start supplying boards and masts with tuttle. I don’t think that the math is going to be compelling. I think more people riding them and feeling an improvement is the way.
To that end, I want to help more handy do it yourself type people get going on this. It will trickle into the industry bit by bit. And I’m guessing there will be a breakthrough once more people start to take notice of the best riders in the world preferring this system.
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I’m starting to wonder how much Big Tuttle is paying @Beasho
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I have a wide range of boards and foils, and they all need adjustments. I do not feel like I am riding a marshmallow, except on inflatable boards, so I’m ok with plate masts. However, less drag is cool, and less weight is cool, and cheaper masts are cool.
Why not add spacers that keep the entire track locked together to prevent side to side wobble that could likely come from the extreme pressure of a mast in the center of the adjustable track. I imagine this would eventually loosen and damage the board in a long adjustable track. I could be way off in my estimates, but something like this would make me feel better.
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Your obsession with the plate mast drag tells me you spend a lot of time off foil trying to get on foil. Most of us have our plates out of the water for 99% of our session.
I think nearly all of us on here appreciate the fact that someone of Kane’s standing in the sport and industry, is willing to post how he sees things every now and then, without being made to think we are just all a waste of time.
The conversation started well enough but you ignored so much along the way why would you expect someone of @KDW 's standing to unpick so much gibberish.
You undid your own credibility.
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Like raindrops from heaven. Despite all the acrimony — push forward.
Here is the nightmare math, now with pictures.
Look at Image 1. Two tracks, 9mm wide × 30mm deep. That’s 540mm² of frontal area — open ram inlets facing directly into the flow. Now look at the recessed bolt heads sitting inside those tracks. Countersunk into the slider nut. A perfect concave cup face. That is not incidental geometry. That is an anemometer, installed in your mast base by the manufacturer.
The cup face drag coefficient is 1.42 — 31.5× the drag of an efficient airfoil.
The math: (or the code that was asked for feel free to double check your aeronautical engineering textbook, CFD or LLM of choice).
540mm² ÷ 19mm mast thickness = 28.4mm effective length
28.4mm × 31.5 = 895mm
~90cm of equivalent 19mm mast drag. From the bolt heads and track inlets alone.
That doesn’t count the 120mm wide base plate, the skin friction, the blunt trailing edge, or the matching track recesses on the rear — which are the same geometry, now acting as base suction cups pulling backward.
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So I did what any self-respecting builder would do. I cut XPS foam inserts, pressed them into the tracks, and faired the leading and trailing edges flush to the plate with a razor. Then I went to Mushroom Rock — inside Mavericks — in typical soupy cross-chop that two kayakers had already pronounced terrible. Here is what happened:
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Paddling speed to the break increased. Glide and tracking both noticeably better. Not surprising in retrospect — reduced drag is reduced drag whether you’re paddling or foiling.
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Setup speed on takeoff was higher. On a low-volume board that previously had the nose diving 12–18" underwater, the speed increase added stability. Two data points in one.
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Drama factor dropped from ~80% to ~30%. I was comfortable laying down power on takeoff instead of managing chaos.
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Takeoff conversion went from “I’m not sure I can get that” to “my superpowers are nearly back.”
Call it a 10% improvement. In terrible conditions. With foam and a razor blade.
On the aeration argument — I foil 300+ sessions a year. SUP Foil Downwind style boards engage the foil at roughly 7mph on the face of a breaking wave or behind a bump. Clean blue water, not whitecaps. Aerated turbulent flow is the barn-door crowd’s problem. The drag penalty we’re discussing happens in exactly the clean-water conditions where performance foiling actually occurs.
The math said there should be a large benefit. The water confirmed it.
Feel free to try it out, no Tuttle base needed.
8’ x 18" ~ 100 liters that I got from the local pro that found it potentially too low volume for the local ocean conditions.
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