What is lift? Are you sure?

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What is lift? Are you sure?

A concept most important to sailing and hydrofoiling isn't as simple to explain as you might think. Most of the simplistic explanations you learned are incomplete and scientists are still struggling to come to a consensus.

https://www.scientificamerican.com/article/no-one-can-explain-why-planes-stay-in-the-air/

I imagine a couple of members here will enjoy discussing this. Biggrin

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Re: What is lift? Are you sure?

For regular flying, think happy thoughts. Helicopters are believed to maintain flight by beating the air into submission. Good

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Re: What is lift? Are you sure?

Also, for regular flying there's this. Helicopters also vibrate so bad the Earth rejects them.

Bill Herderich

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Re: What is lift? Are you sure?

Oh man. I may have missed it in the reading, but it seems there ought be some aspect and discussion of the air’s ACCELERATION over a foil’s topside that would help account and explain for some portion of the pressure drops on the top. I.e. 1) the angle of attack, alone, can and does create a relative vacuum somewhere on the top (and somewhat “back”) side of a foil, even if inverted, even if flat on both sides. And then 2) that relative vacuum, perhaps, in addition to contributing to a pressure differential on its own, also demands an acceleration of the air particles to fill it. And, significantly (!?) as those particles accelerate (get “sucked in”) to fill it, they do so in a manner that is relative to their proximity to that vacuum, thereby getting spread further apart from each other in the process...thereby becoming “less dense” ( and exerting less pressure) even at those points as well. Kind of like when cars come OUT of a traffic jam...the density of cars is reduced as each car gets “freed” and accelerates at staggered times, and not in one uniformly spaced collection. Heck. What do I know. I don’t even know if I know enough to feel confused. Newton blows on the bottom, while Bernoulli (or one of his not yet fully articulated but close relatives) sucks from the top, and voila! We sail, fly, and foil. But Blah blah blah. I’m sure my rough postulations have been well covered (refuted, confirmed, clarified) somewhere already. But my reading of the article, and contemplations about it and lift, may well have advanced my personal understanding, even if still pleasantly naive. Guess I’ll just hope no one was bored enough to read all this (my post, that is) ShokLol And thanks for posting, webguy!!

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Langdon
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Re: What is lift? Are you sure?

After studying the Horue stabilizer. I now know some of the reasons Webguy swam so much his first year.

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Re: What is lift? Are you sure?
Langdon wrote:

After studying the Horue stabilizer. I now know some of the reasons Webguy swam so much his first year.

It was okay when I finally had it set to the proper angle of attack which took a while. So many people back then had the conception that a flat stab meant you were faster thus a good thing. My board was a much bigger issue.

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Re: What is lift? Are you sure?

Pretty sure F=ma and Bernoullism are both at work. Stick a sheet of plywood out of a car window at highway speed and you'll get a lot of lift even at a stalled angle of attack. There is obviously less pressure on the lee side of a sail as we can plainly see by Taty Frans' expression below. Q.E.D. Good

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Re: What is lift? Are you sure?

'twas kind of a surprise to understand the distinction between a fin stalling at a high angle of attack vs one cavitating where water boils on the low pressure side. Shok

http://mauiultrafins.com/technology-2/fin-secrets/

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Re: What is lift? Are you sure?
FoilDodo wrote:

There is obviously less pressure on the lee side of a sail as we can plainly see by Taty Frans' expression below. Q.E.D.

ClappingROFL

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Re: What is lift? Are you sure?

Sweet mother of pearl. Chris just won the internet today. Everyone turn off their computers and devices and go home. Game over. Good

--- The Arrogant Jerk: Crabby and irritable since 1998.

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rgenet
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Re: What is lift? Are you sure?

It's not that complicated - this flys:

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Re: What is lift? Are you sure?
rgenet wrote:

It's not that complicated - this flys:

Ah, but why does it fly? Wink It's a simple toy but a the same time so complex that even the steam locomotive, Babbage's Difference Calculator and Maxwell's equations proceeded it.

http://www.rubber-power.com/history-of-aviation-rubber-power.htm

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rgenet
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Re: What is lift? Are you sure?

Why? Because of these two - this is the most awesome book / story / reality:

https://www.amazon.com/Wright-Brothers-David-McCullough/dp/1476728747/

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Re: What is lift? Are you sure?
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Re: What is lift? Are you sure?

very cool. (and I see the owl doesn't subscribe to the "winglet" approach)

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