More on leeway and sail trim (tom's video)

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havliii
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Boat Make/Model: SuperCat 19, Modded SC20
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More on leeway and sail trim (tom's video)

Post by havliii »

Tom P. forgive me for using your video, but it is the most terrific illustration that one could have.

Find Tom's video link in his previous post. Go to 59 sec mark and watch the boat crab, the wake is nearly 30 degrees to the heading. Watch the next 16 secs, OVER AND OVER, at the 1:15 mark Tom turns the boat onto the proper heading for the trim of the sails, the hull flies, the boat takes off and the wake straightens out. The wake goes nearly dead aft at the 1:16 mark.

No criticism is suggested here, it's just a great illustration of 'trimming for the point of sail' or 'sailing the trim.'
Bill Roberts
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Re: More on leeway and sail trim (tom's video)

Post by Bill Roberts »

havliii,
I looked at the video at one minute. What I see is a wake aimed off to leeward of an extended hull centerline in the aft direction. This means the boat is working its way to windward, to windward of the way the boat is aimed ,at a large angle. WOW, this boat is sailing to windward like crazy. Its path through the water is much higher than the way the boat is aimed. This a a major technology breakthrough! If the boat were crabbing, it would be slipping to leeward and the wake would be to windward of an extended hull centerline in the aft direction.
In this picture, one minute into the film, the wake appears to be to leeward of an extended hull centerline. The boat is turning to the right in a smooth curve. The boat is turning to the right in a transient path, a curving path to the right. In this condition an aft extended hull centerline will appear to be above or to windward of the path, the wake, the boat is making or leaving in the water behind the boat.
As soon as the boat stops turning, it accelerates and spray appears at the bow as the boat sails in a straight line with wake straight behind.
havliii
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Re: More on leeway and sail trim (tom's video)

Post by havliii »

Without boards going to windward imagine that! What kind of breakthrough we talking here shared lift.

Excellent illustration eh?
Bill Roberts
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Re: More on leeway and sail trim (tom's video)

Post by Bill Roberts »

havlii,
We, you, are talking about a physical impossibility. There is no force that will make a sailboat crab to windward. The side force in the sail can only make a sailboat crab, slide, to leeward. The video of the SC17 appears to show it crabbing to windward which is a physical impossibility. In the video the boat is not crabbing at all, it is turning to the right slowly, bearing off and then going straight. While it is bearing off, while it is turning to the right, it appears as though the boat is sailing higher into the wind than the boat is aimed because the wake is trailing off downwind, to leeward. If the boat was sailing in a straight line and the wake was trailing off to leeward, it would be MAGIC.
havliii
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Re: More on leeway and sail trim (tom's video)

Post by havliii »

Please re-read my initial post I never stated that the boat was going to windward. I'm guessing here, but I think your first answer was full of sarcasm and ridicule. Maybe the second answer also.
Bill Roberts
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Re: More on leeway and sail trim (tom's video)

Post by Bill Roberts »

havliii,
I'm sorry our discussion fell off the tracks. Some of the words I used were for emphasis
to explain what was happening in the video as I saw it. I also used some of the laws of physics.
If you have any questions or further interest in what you saw in the video, I suggest you do the "tow a string test".
See what you have to do to the boat to make the string hang straight behind the boat.
See what you have to do to the boat to make the string hang to windward of an extension of boat centerline.
See what you have to do to the boat to make the string hang to leeward of an extension of boat centerline.
All the best to you.
Bill
T Peterson
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Re: More on leeway and sail trim (tom's video)

Post by T Peterson »

Hi folks - glad to be of help! None of us is perfect and the more we learn from each other the better we get. In fact, just two weeks ago, after sailing cats for 40 years, and tipping over a LOT, I learned a new technique from Bill about hopping on to the bottom hull after the boat hits the point of going over and riding it up like a horse. I just did that last week after a guest skipper dumped the boat over with me as crew...but I had the crew ride the hull over because they usually have a harder time getting back on than I do.

Anyway, the drone owner wanted me close to shore so I tried to sail close to shore but then started to trim the crew and sails early for more upwind sailing so I could do a quick turn in front of his house and take off upwind for some better aerial shots. So at times the boat was trimmed properly and at times, not.

The other thing I notice on this lake, and maybe most, is that when the wind gets close to shore, it sweeps along the shore and changes direction. Once you get clear of shore, and the trees, the wind is more normal.
Bill Roberts
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Re: More on leeway and sail trim (tom's video)

Post by Bill Roberts »

Thanks T. Peterson, "ride'm cowboy'!
That technique is about 40 years old.
How did it get Lost?
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