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Old 11-02-2013, 17:41   #61
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Re: Settle an argument

Wing shaped sails are all "bunk?" That's why racer's sails are all completely flat, right?

There are some boats, such as Sunfish, that basically have a flat sail but they are few and far between. Sunfish is a simple lateen design that sails pretty well for being a flat sailed lateen but if you put a marconi laser sail which has a win shape on a Sunfish hull it sails very much better to windward even though they have the same sail area.
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Old 11-02-2013, 17:47   #62
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Re: Settle an argument

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My all time favorite is the flying toilet seat!
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Old 11-02-2013, 17:52   #63
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Re: Settle an argument

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Ok, had a friendly argument with my father in law this weekend. Last time we rented a sailboat for a day the instructor commented on the importance of sail trimming due to the fact the sail is basically a wing. Later on that day my father in law brings up that he believes this is all mumbo jumbo and that the "wing effect" is basically oversold. He claims that a perfectly workable sail could be made out of a flat solid sheet of material with no curve and you would get decent performance out of it. Not as good a a curved sail, but almost as good. I told him it might work but would basically be crap and give little to no forward thrust. Who is right?

Tom
I think they are both right - or wrong. It depends what value you assign to the words "decent" and "crap".

The aerobatic aircraft analogy is not the best because even the symmetrical wings have a large radius leading edge. This helps tremendously in keeping flow attatched at higher angles of attack. Then again, If the father-in-law is assuming that the sailboat mast (large radius leading edge) is in place ahead of the flat sail, then he is a little bit more correct.

Plane is an early model of the iconic "Pitts Special". Wings are asymmetrical. Flies fine inverted although it loses about 20 knots if I do not add power.

Water in background is the Strait of Juan de Fuca.

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Old 11-02-2013, 18:04   #64
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Re: Settle an argument

I know from beans about airplanes!! My question is where do ya stand wirh Junk sails ?? flat? curved, in between? I just wonder?
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Old 11-02-2013, 18:20   #65
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Re: Settle an argument

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I know from beans about airplanes!! My question is where do ya stand wirh Junk sails ?? flat? curved, in between? I just wonder?
I know from beans about Junk sails!! I dont even know witch is better - mast on the windward side or downwind side?

In-spite of the stiff, full length batons, It seems there is still a fair bit of camber in between them.

Do the gaff rigged gazelles sail to windward better that the Junk rigs?

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Old 11-02-2013, 19:54   #66
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Re: Settle an argument

Tom Whidden, in the Art and Science of Sails, questions the "popular theory". I won't go through the whole chapter.
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Old 11-02-2013, 21:31   #67
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Re: Settle an argument

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Thinking of the latter as the application of the former. ...............................
I know this concern doesn't merit time on this post, but your description confirms my thoughts. Engineers are applying science and engineering is a scientific endeavor. Engineers are working at a level of understanding that is not rote application worker bee,- "hook the red wire to terminal B". Engineering is science, no less than a duck is a bird. Engineers are required to be physicist to a great degree. Scientists are not all in the "Irvory Tower". .......but this all comes down to a consensus that we are probably in total agreement.

Anyway, as with the other agreement, the sail is a "wing" and increasing behaves as a "wing" as the heading is closer to the wind.
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Old 12-02-2013, 05:18   #68
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Re: Settle an argument

Huh??.......I thought sails worked by magic.
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Old 12-02-2013, 05:32   #69
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Re: Settle an argument

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Huh??.......I thought sails worked by magic.
Oh, but it IS magic! I thought everyone knew this from the first time they saw burbling wake astern, felt the heel of the boat and the little tugs from the tiller and heard nothing but water rushing by, pausing to give a friendly slap to the hull now and then.
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Old 13-02-2013, 06:30   #70
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Re: Settle an argument

Wow, I had no idea a simple question would spark so much debate. I also had no idea the theory for the cause of lift was in question. Great information guys.

Thanks,
Tom
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