That’s great, I want to try it! The big floaty wing we all wanted.
Zero? What do you mean. The customer has to buy two foil setups. Twice as good!
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can the flaps be passive or must they be activated somehow?
There’s a PDF at the bottom of the page that gets in depth. But it’s just a hinge that’s activated by low pressure at the onset of a stall and held up until the laminar flow overcomes the circulating air at the trailing edge. One of the takeaway figures showed a 7% increase in lift with 61% of the wingspan having a covert flap.
Something that stood out to me was the idea that wingtip vortices help reenergize laminar flow at the wingtips - which is where the wing stalls first. I’ve been going down a rabbit hole lately about wingtip designs and airliners are designed for efficiency, not stall recovery. Reading this makes me wonder if a foil recovers from ventilation faster with a raked wingtip that reduces wingtip vortices compared to winglets which delays the vortex formation which reduces the stall recovery characteristics.
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The idea is they are passively activated by the reverse fluid flow during a stall.
Found an article with some video of them in action.
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Pretty much. These explanations on Stack answered a lot of the questions I’ve had about winglets. And this picture really blew my mind. The downward facing winglets probably help with vortices but their biggest contribution is that once the wing has flexed, they become an extension of the wing!!
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Something to remember about winglets is they only help reduce wingspan.
Wing would be way more efficient (and lighter) if said winglet was laid flat increasing the span and aspect ratio.
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This turned into a rambling knowledge dump I made while getting ready for Thanksgiving or else I’d have laid it out in a more coherent order of explanations….
Yeah, but that might be an abstract way of putting it. Wingtip devices extend the effective length and span wise pressure distribution of the wing without increasing its geometry, so it allows you to get more efficiency from a shorter wingspan. This is where I realized myself, and probably a lot of us, are losing the distinction between wingtip vortices and wake turbulence.
This picture shows areas of low pressure represented by “fog” and the small size of vortices made wherever an edge is presented that low and high pressures meet each other. You can see them on the wingtips, flap edges, and the rear stab. It’s a great visual for the difference between vortices on a square wingtip (the flap edge) and the effectively tapered edge of the wingtip.
If the result of a wing carving a trough through the air is shaped like a deep V, it creates stronger wake turbulence. If you flatten out that trough you get weaker wake turbulence because the trough is flatter and not pulling downwards and inwards. Think of it like comparing the wake behind a deep V hull and a flat bottomed boat. The bigger wake from a deep V hull is the result of stronger forces pushing displaced water back towards the center. Tall winglets help flatten that wake. That’s what raised wingtips are trying to accomplish by creating a wake turbulence that is even more flatter than a flat bottomed boat. It would probably be like a protruding rounded edge along the chine of a flat bottomed boat.
And here’s the relative size of wake turbulence. You can see the little wingtip vortices here too.
Older jets made for endurance have maxed out their wingspans so winglets have been the retrofit solution for better efficiency, but it’s not as simple as throwing a winglet on there.
Take a look at the 737 Max on the left with AT winglets. It becomes more efficient the faster you fly it because of the diagram I posted above - they transition into lifting devices as the wing flexes with more airspeed. They provide 2.5% more efficiency in cruise and are reserved for planes that usually fly for 9+hrs because the fuel saved during an efficient cruise outweighs the crappy climb performance.
The 737 NG on the right with split scimitar winglets gets 1.5% more efficiency in cruise but climbs much better because the winglet cleans up the wake turbulence, which is strongest during climb (clean, heavy, and slow with a high AOA) so they use that tip configuration on routes that are typically less than 6 hours.
Boeings longest range jets like the 747-8F, 777X, and 787-9 use raked wingtips while Airbus is using raked winglets on their A350-900 to get a combination of both advantages. So with two different methods to get the same end result, it opens up a deeper rabbit hole as to which version is better and why.
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How do they handle breaches?
Was that to me or the Boeing?
Mine breach great! Never ventilate unless too flat or going really slow. I think the recipe for tip breach performance is 80% section and twist and 20% tip shape and angle
Similar to the pumping in waves (whoosh) thread: pump drafting like geese in V formation. Could three good pumpers go farther by trading turns taking the lead while the other two pump on the vortexes of the leader?
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I’ve tried this, I think the possibility is there but there are some difficulties. The vortex doesn’t have water uniformly moving up at the same speed, so you really have a narrow target to get the extra lift centered under the second foil. Also, half of that vortex is moving down, and you’re working a lot harder if you get in it.
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Board mounted DW paddle holder 
https://www.instagram.com/p/DC9TkRPuGh6/
I like the idea of a few mounting points on the board to attach crap to keep it out the way. Need a lunch box on the tail to put supplies
surprised this works, the fact that he is getting millions of views on these videos is almost certainly going to have some impact on the flat water scene.
That’s great. Do you think that if the foil was larger say 50-75l volume, you could just bump really really slow, but forever?
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