Wow...

RussC

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Sep 11, 2015
1,578
Merit 22- Oregon lakes
Indeed they do. But we're not talking about a theory here, we're talking about a validated model.
At 68 I've lived long enough to see many things that I never would have believed were possible, therefore I now try really hard to keep an open mind in these things. but try as I might, to me, a "validated model" is still a theory until proven in a full size example. lets just say: I remain extremely skeptical :)
 
May 17, 2004
5,027
Beneteau Oceanis 37 Havre de Grace
At 68 I've lived long enough to see many things that I never would have believed were possible, therefore I now try really hard to keep an open mind in these things. but try as I might, to me, a "validated model" is still a theory until proven in a full size example. lets just say: I remain extremely skeptical :)
But there is a full sized model - the America's Cup boats achieved this performance routinely.
 
May 25, 2012
4,333
john alden caravelle 42 sturgeon bay, wis
never had two sails that were the same, always something new to learn. i love messing around with boats :)
 

walt

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Jun 1, 2007
3,511
Macgregor 26S Hobie TI Ridgway Colorado
Russ, you could experience this.. You are not that far from the Alvord desert and a few times a year a bunch of land sailors converge there and sail for a couple days. There is a fair chance that you could get a ride in one of those (most are single seat - someone would really have to trust you would not ruin their baby of sue them). It is very easy to get a land sailor going with a vector component in the direction that you know the wind is blowing (ie, you are sailing "downwind") but you are sailing with a head wind. Very easy to accomplish even with fairly simple lower tech land sailors because they have such low drag.

You still have to make the conceptual leap that its the difference or gradient in velocity between water (or land) and air that we extract the power from to sail in. You can get that difference if the water is stationary and the air is moving. Or you can get that same difference if the air is stationary and the water is moving.
 
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Feb 5, 2009
255
Gloucester 20 Kanawha River, Winfield, WV
The commentator in questions is Iain Percy, a 2-time Olympic gold medalist, the tactician on Team Artemis, and one of the world's best foiling sailors. Pretty sure he knows that he's talking about.
Iain may know what he's talking about, but his description in the video is nonsense. (Time limit, target audience, and so forth, I presume.) I can visualize how you might be able to sail on current power, but it's not “Drift until you get up to 10kt, turn around, and, presto, you go to the source of the Amazon at 30kt.”

Here's how I picture it. (First let me say I know almost nothing about sailing, and in the very likely event that I'm wrong, well, it won't be the first time.)

Having some aviation background, when I sail my boat I rationalize it as an airplane with one wing sticking up in the air and the other one down in the water. If I'm reaching or above, the wing that's up in the air is converting energy from the wind into motive force and the wing down below is using the water for leverage to make that energy move my boat forward instead of sideways. (I have a visualization that involves stalls and spins, but we don't need to go there for this discussion.)

I can't reverse the roles and make use of the energy in the current for propulsion because my sails can't get enough purchase on the air to effectively direct the force that my keel is not very effectively capturing and direct that force the way I want it to go. (I sail on a river all the time, and I'm pretty sure of this.)

Those AC boats are whole different kettle of worms, though, with their super efficient sails and foils. Turn your boat (or the world) upside down in your mind and imagine your keel slicing through still air and your sails filled with flowing water, and maybe you can see what I'm thinking.
 
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Aug 13, 2012
533
Catalina 270 Ottawa
You still have to make the conceptual leap that its the difference or gradient in velocity between water (or land) and air that we extract the power from to sail in. You can get that difference if the water is stationary and the air is moving. Or you can get that same difference if the air is stationary and the water is moving.
I think, this is the most succinct description of what is happening and the biggest issue most disagreeing have a problem with. If you understand that you sail if the air moves relative to water, then it does not matter which medium actually moves (air or water) - the relative movement between the two is the only thing that matters.
 
Oct 19, 2017
7,732
O'Day 19 Littleton, NH
I can't reverse the roles and make use of the energy in the current for propulsion because my sails can't get enough purchase on the air to effectively direct the force that my keel is not very effectively capturing and direct that force the way I want it to go.
Doesn't it do that very thing even under normal conditions? If your sail isn't enough to get a purchase, it isn't enough to get a purchase with the wind blowing past it or with it blowing past the wind. After all, that big sail moves tons of real weight against the keel held water. Either way, that sail has purchase. In airplane terms, it keeps a plane from falling.
The biggest difference I see between a sail and an airplane wing is that the wing generates lift from the plane's movement through the air while a sail generates movement from the lift generated by movement across the sail, this movement generates even more lift. They are slightly different dynamics that are both reliant upon "lift", but not exactly the same.

in the very likely event that I'm wrong, well, it won't be the first time.
Excellent attitude, I whole heartedly embrace, as I'm sure there are plenty here on SBO who can attest to that.
It's hard to learn what you don't know you don't know if you don't throw what you think you know out there. :thumbup:

-Will (Dragonfly)
 
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RussC

.
Sep 11, 2015
1,578
Merit 22- Oregon lakes
Russ, you could experience this.. You are not that far from the Alvord desert and a few times a year a bunch of land sailors converge there and sail for a couple days. There is a fair chance that you could get a ride in one of those (most are single seat - someone would really have to trust you would not ruin their baby of sue them). It is very easy to get a land sailor going with a vector component in the direction that you know the wind is blowing (ie, you are sailing "downwind") but you are sailing with a head wind. Very easy to accomplish even with fairly simple lower tech land sailors because they have such low drag.

You still have to make the conceptual leap that its the difference or gradient in velocity between water (or land) and air that we extract the power from to sail in. You can get that difference if the water is stationary and the air is moving. Or you can get that same difference if the air is stationary and the water is moving.
I flew over the Alvold desert once (hang glider). does that count? :)
your last paragraph is persuading, and might almost kinda sorta make a convert out of me, in theory...... but there's that theory thing again :biggrin::biggrin:
 
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Feb 5, 2009
255
Gloucester 20 Kanawha River, Winfield, WV
If your sail isn't enough to get a purchase, it isn't enough to get a purchase with the wind blowing past it or with it blowing past the wind.
I don't mean that my sail gets no purchase on the air at all, just that it doesn't get enough to play the role of keel while my keel plays the role of sail. That and a few million dollars is the main difference between my boat and an AC72.
 
May 25, 2012
4,333
john alden caravelle 42 sturgeon bay, wis
simmon, i knew a man, Charles Brodhead, that sailed on the steel clipper Peking as a deckhand back in the 1920's. there where 365 lines to control the sails of the vessel. the bosun tested them daily on knowing each one. he and his buddy, both farm kids, shipped out together on a lark. his buddy was/became Captain Johnson who became famous as the captain of the brigantine Yankee that had many articles in the national geographic mag back in the 50's and 60's. he was a young pup when he sailed. i knew him as an old man. he was the assistant head master at the prep school i went to out east.
some of the old timers here prolly remember Capt Johnson. who sailed the world in a fashion we all dream of.
the Peking is now at the south street museum in NYC

 
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May 25, 2012
4,333
john alden caravelle 42 sturgeon bay, wis
love roasted duck. smeer with soy sauce then 400 degrees for 4 hrs, yummy

talk about thread drift ...............................................
 
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Jul 29, 2004
406
Hunter 340 Lake Lanier, GA
Yep! I walked her decks a couple of times at South Street Seaport years ago, so that news caught my eye when it was announced.
 

RussC

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Sep 11, 2015
1,578
Merit 22- Oregon lakes
Russ, you could experience this.. You are not that far from the Alvord desert and a few times a year a bunch of land sailors converge there and sail for a couple days. There is a fair chance that you could get a ride in one of those (most are single seat - someone would really have to trust you would not ruin their baby of sue them). It is very easy to get a land sailor going with a vector component in the direction that you know the wind is blowing (ie, you are sailing "downwind") but you are sailing with a head wind. Very easy to accomplish even with fairly simple lower tech land sailors because they have such low drag.
I see this one on local CL for only 150.. I think you should buy this to test the theory once and for all:laugh:
00D0D_l2vPmlH3AVb_600x450.jpg
 
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