Comparing Upwind Performance / Tacking Angles - Page 2 - SailNet Community

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  #11  
Old 05-23-2011
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Forget the rest. You have plotted the course of the boat. What I am talking about is about the angle on that plotted course. It appears directly on my plotter so I use it to see how well I am doing regarding going upwind.

Assuming there are no significant current what that plotted course shows is that you are doing a bit worse than 90º. You are doing 80º or something like that. That gives a 50º angle to the true wind.

You say you were sailing with only 7 to 10K of wind with short waves so that are far away from ideal conditions. With more wind you should be able to make a 90º angle that is what sailakm is talking about. I say that in ideal conditions I can get a bit better than that and Barry is saying that racing with a crew and good sails he can do 100º and that is pretty good. It means an angle to true wind of 40º. To do that the boat has to be pointing closer to the wind to compensate drift.

Regards

Paulo
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Old 05-23-2011
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thanks Paulo. What it also does'nt show are the two ships I had to dodge on the next two tacks. One even gave me a long blast with his horn. You would think a 600 ft ship should know that power gives way to sail

Ilenart
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Old 10-11-2012
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Re: Comparing Upwind Performance / Tacking Angles

One real-world data point:

I recently analyzed upwind GPS data for my GS 41 from two different races in Chesapeake bay. Best overall tacking angle (true, based on COG, so including leeway, etc., not 'pointing angle') was 110.6 degrees. average more like 115 degrees. The two race average helps remove effects of current.

A lot of this result is based on wide sheeting angles on the GS, with sails cut for that. But, I was racing in a mixed fleet of similar era boats. Only a few were able to significantly outpoint us.
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Old 10-11-2012
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Re: Comparing Upwind Performance / Tacking Angles

Those figures don't add up with a course over ground difference of 107 plus on the next leg on the plotter. 80 is not a bit worse than 90. The diagram Paulo did is not right. It shows an upwind tack and a downwind tack and the difference between them. So if each is at 30 to the true wind the difference between the two angles sailed is given as 120. That is not the tacking angle however. The tacking angle upwind would be 60 meaning one would be sailing at less than 30 to the apparent wind, which is unlikely except in an extreme machine.
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Old 10-11-2012
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Re: Comparing Upwind Performance / Tacking Angles

Quote:
Originally Posted by chris_gee View Post
Those figures don't add up with a course over ground difference of 107 plus on the next leg on the plotter. 80 is not a bit worse than 90. The diagram Paulo did is not right. It shows an upwind tack and a downwind tack and the difference between them. So if each is at 30 to the true wind the difference between the two angles sailed is given as 120. That is not the tacking angle however. The tacking angle upwind would be 60 meaning one would be sailing at less than 30 to the apparent wind, which is unlikely except in an extreme machine.
On my new boat that is very good upwind (comet 41s) I can make 27º to the apparent wind with 18k of ap wind and 1.5m/2.0m short waves. That was a wet ride with the boat doing about 6.5K. I could go faster If I bear away but I was just trying the boat and want to see what the boat could make.

At the time I have posted about that in the interesting sailboats thread. In perfect conditions without waves and much less wind the boat can make about the same angle and 7.5k speed.

With the Bavaria on optimal conditions I could make 30º to the ap wind but the boat could not make that with 2.0m short waves on the bow. On those conditions the speed was just about 3.5K and if the angle was not too bad but the boat drifted a lot due to the lower speed.

Regards

Paulo

Last edited by PCP; 10-11-2012 at 06:43 PM.
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Old 10-11-2012
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Re: Comparing Upwind Performance / Tacking Angles










Zzzooom which is a 1970 C&C 35 the PO hired Britton Chance to design a series of keels and rudders and the double spreader bendy mast and 42 years later it still rates 111 and hangs UPWIND with J 105s and comparable boats

It completely destroys any current cruising boat in JAM racing with the weak point being the modern bow sprit boats like the 105 have a huge OFF-WIND speed advantage as were are stuck in displacement mode
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