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Old 16-11-2015, 05:24   #556
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Re: Why Do Catamarans Motor Nearly 100%

Quote:
Originally Posted by Dockhead View Post
I think Polux has far too much faith in polars, which in my experience often have little relationship to reality.

However, I agree with his point here. Upwind at 10 knots in 10 knots true? I think that cat should be entered in the next America's Cup.
I am grateful that my boat move in 10 knots true.
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Old 16-11-2015, 05:28   #557
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Re: Why Do Catamarans Motor Nearly 100%

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Originally Posted by Polux View Post
We were talking about sailing upwind. Any data to support that? Polars from your boat?

Upwind with 10K wind doing 10K speed wind is a much better performance than doing 4K with 4K wind. Here you have the polar speed of a Outremer 45, a very fast performance cat:
As you can see it is needed 23K true wind for the Outremer 45 to be able to sail at 9K speed at 70º of the true wind and even at 90/100º the speed is only a bit over 10K. Is your boat so much faster then an Outremer 45 to be able to sail at 10K with 10K wind? That is truly the performance of a carbon top racing boat, not the one of a cruiser racer.
it s actually 14-15kn to sail 10kn at 70 deg.

However at 24 kn progress towards wind is 7.71 kn which is better than pogo 12.5.Higher winds difference would be even larger.

I have seen video outremer doing 10+ in 10 kn true. No idea of angle.

Polars are pretty and useful for lake sailing only. They quickly lose its value in real ocean conditions under autopilot.
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Old 16-11-2015, 05:44   #558
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Re: Why Do Catamarans Motor Nearly 100%

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Name:	Light-Winds.jpg
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ID:	113128

Who needs to motor?
Example of my Condo Cat in light air doing 4.3 kts (GPS) in 4.2 kts of true wind going "upwind".

Well, "upwind" at 80 degrees TWA (which is actually 39 degrees AWA with 6.5 kts AWS)

True/Apparent Wind Calculator: Apparent Wind Calculator | Hyde Sails Direct
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Old 16-11-2015, 06:13   #559
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Re: Why Do Catamarans Motor Nearly 100%

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Attachment 113128

Who needs to motor?
Example of my Condo Cat in light air doing 4.3 kts (GPS) in 4.2 kts of true wind going "upwind".

Well, "upwind" at 80 degrees TWA (which is actually 39 degrees AWA with 6.5 kts AWS)

True/Apparent Wind Calculator: Apparent Wind Calculator | Hyde Sails Direct
I don't understand those numbers. The Raymarine wind is set to apparent (arrow on the bottom). Using that data on the calculator you provided what comes up is:

VMG to wind -2.79 ..... True Wind Angle 131.6°..... Apparent Wind Angle 80° .....True Wind Speed 5.3... Apparent Wind Speed 4 ....Boat Speed 4.2 Boat speed as % of true wind speed 79.6 .... VMG as % of true wind speed -52.8

So in fact you are not sailing upwind and your VMG upwind is a negative one.
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Old 16-11-2015, 06:20   #560
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Re: Why Do Catamarans Motor Nearly 100%

The wind instrument is set to True - look a little bit carefully....
The little black LED box in the display just above the word true .....
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Old 16-11-2015, 06:37   #561
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Re: Why Do Catamarans Motor Nearly 100%

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Originally Posted by Dockhead View Post
I think Polux has far too much faith in polars, which in my experience often have little relationship to reality.

However, I agree with his point here. Upwind at 10 knots in 10 knots true? I think that cat should be entered in the next America's Cup.
Yes, it is 10k true and yes the data is reliable since it is not taken from a performance provided by the manufacturer but from a ORCI rating file and any sailor would want those numbers and speeds as low as possible to be able to sail the boat to them and have a good classification on compensated racing (ORC).

ORC is at the moment the more accurate rating system but it could be on a particular case (that one) not true with the reality, but that would be a very small difference and anyway the Comet 41s is a competitive boat in ORC having won many races on compensated.

Also those speeds at 10k on the ORC file are similar to the speeds of similar boats at those wind angles, for instance the ones of a First 40, a Salona 41, a X-40 or a Arcona 400/410.

Here you have some examples:
A X-40:
http://www.avomeripurjehtijat.fi/mit...013/L40105.pdf
A First 40:
http://www.avomeripurjehtijat.fi/mittakirjat/L11329.pdf
A Arcona 400
http://www.avomeripurjehtijat.fi/mit...012/L-0100.pdf
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Old 16-11-2015, 06:49   #562
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Re: Why Do Catamarans Motor Nearly 100%

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Originally Posted by 2Wind View Post
The wind instrument is set to True - look a little bit carefully....
The little black LED box in the display just above the word true .....
Sorry about that. It was not intentional. On my wind instrument it is an arrow that shows if it is set on apparent or true and it seemed to me that on the right there was an arrow.

Anyway taking into account what the instruments show, now with true wind and true wind angle, you are almost not making any way upwind, just a VMG of 0.71k (again using the calculator you linked).

VMG to wind 0.71....True Wind Angle 80°.... Apparent Wind Angle 40.6°... True Wind Speed 4.2 ....Apparent Wind Speed 6.4
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Old 16-11-2015, 09:53   #563
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Re: Why Do Catamarans Motor Nearly 100%

Quote:
Originally Posted by Polux View Post
Yes, it is 10k true and yes the data is reliable since it is not taken from a performance provided by the manufacturer but from a ORCI rating file and any sailor would want those numbers and speeds as low as possible to be able to sail the boat to them and have a good classification on compensated racing (ORC).

ORC is at the moment the more accurate rating system but it could be on a particular case (that one) not true with the reality, but that would be a very small difference and anyway the Comet 41s is a competitive boat in ORC having won many races on compensated.

Also those speeds at 10k on the ORC file are similar to the speeds of similar boats at those wind angles, for instance the ones of a First 40, a Salona 41, a X-40 or a Arcona 400/410.

Here you have some examples:
A X-40:
http://www.avomeripurjehtijat.fi/mit...013/L40105.pdf
A First 40:
http://www.avomeripurjehtijat.fi/mittakirjat/L11329.pdf
A Arcona 400
http://www.avomeripurjehtijat.fi/mit...012/L-0100.pdf
But you didn't claim to make 10kn in 10kn of wind. You claimed 4 in 4, and you said that this is much easier than 10 in 10. I was agreeing with you.

According to these ratings:

The X40 makes 4.8 knots VMG in 10 knots of true wind. You can't tell the boat speed because you don't know the tacking angle. "Beat angle" is 42.8 degrees. I guess that is TWA. So with leeway that would be a tacking angle of about 92-95 degrees I guess. So boat speed must be about 1.5x VMG or about 7.2 knots. That seems like extremely good performance to me.

The First 40 makes 4.89 knots VMG in 10 knots true. "Beat angle" is 40.4. I guess that could be a tacking angle of around 90 degrees. Boat speed about the same as the X40.

The Arcona is slightly slower -- 4.72 knots VMG in 10 knots true; "beat angle" 42.5.

This all seems much better than what my boat achieves; yet I have had many upwind duels with Bene Firsts of different kinds, including the First 40, and have never lost one, even with my old sails and my old big RIB (since retired) hanging off the back. I think real life and ratings are going to be different in most cases, even ratings like these.
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Old 16-11-2015, 12:10   #564
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Re: Why Do Catamarans Motor Nearly 100%

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but with the one of my own boat.
Generating those pretty polar diagrams from raw data collected from your own boat must have been a lot of work for you.
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Old 16-11-2015, 12:28   #565
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Re: Why Do Catamarans Motor Nearly 100%

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Generating those pretty polar diagrams from raw data collected from your own boat must have been a lot of work for you.
It doesn't have to be. I have several apps that continually collect boat and wind data and plots them on polar curves. All you have to do is sail around for a while in a lot of different conditions and directions and then use the provided tools to statistically clean up the data and voila.

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Old 16-11-2015, 13:18   #566
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Re: Why Do Catamarans Motor Nearly 100%

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Originally Posted by colemj View Post
It doesn't have to be. I have several apps that continually collect boat and wind data and plots them on polar curves. All you have to do is sail around for a while in a lot of different conditions and directions and then use the provided tools to statistically clean up the data and voila.

Mark
I like to have some apps that can do this, Names please.

and the Polars for L380, it is no problem to sail better then the polars.
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Old 16-11-2015, 14:18   #567
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Re: Why Do Catamarans Motor Nearly 100%

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Originally Posted by Polux View Post
Sorry about that. It was not intentional. On my wind instrument it is an arrow that shows if it is set on apparent or true and it seemed to me that on the right there was an arrow.

Anyway taking into account what the instruments show, now with true wind and true wind angle, you are almost not making any way upwind, just a VMG of 0.71k (again using the calculator you linked).

VMG to wind 0.71....True Wind Angle 80°.... Apparent Wind Angle 40.6°... True Wind Speed 4.2 ....Apparent Wind Speed 6.4
Why suddenly bring in VMG. You weren't interested in it when you claimed your "upwind" speed. 2Winds has just shown that he too can get the same boat speed v TWS upwind which you said couldn't be done in his type of boat.
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Old 16-11-2015, 14:46   #568
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Re: Why Do Catamarans Motor Nearly 100%

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I like to have some apps that can do this, Names please.

and the Polars for L380, it is no problem to sail better then the polars.
On the PC Nobeltec has an add-on pack for doing this. PolarManager is another, as is Optima. Someone has also published an Excel-based script that does this (forgot the name- PCsail?). If you can work in French, there is Polaires Auto. GVPP is an open-source one.

On the iPad, there is EDO Instruments, Boat Instruments, iRegatta, and probably several more.

There are probably many more I don't know about.

All of the above range from free to several hundred dollars.

But here's the thing - you will be sorry you went down this road! Manufacturer VPP calculated polars are great. Real world ones not so much.

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Old 16-11-2015, 14:53   #569
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Re: Why Do Catamarans Motor Nearly 100%

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I think Polux has far too much faith in polars, which in my experience often have little relationship to reality.

However, I agree with his point here. Upwind at 10 knots in 10 knots true? I think that cat should be entered in the next America's Cup.
I did say that it was by the same token as Pollux's claim of 4 knots in 4 knots, and tacking through <90'.

ie. They didn't happen at the same time. (Just like his 4 in 4 and tacking through <90) We have sailed at OVER 10 in 10 knots true, at around 80' true. That's upwind, slightly.

And we've tacked through <90' when sailing in 20 knots true, pointing high, and probably doing less than optimum VMG.

BTW 10 in 10 upwind might have been OK for a 12 metre AC boat. With the cat's you'd get slaughtered.
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Old 16-11-2015, 15:02   #570
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Re: Why Do Catamarans Motor Nearly 100%

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We were talking about sailing upwind. Any data to support that? Polars from your boat?
Like you, I didn't say what angle I was sailing upwind...

And the fact is, I'd be quite surprised if our boat couldn't outsail an Outremer 45, all things being equal ie good sails and similar loads...

We have a higher Bruce number than a Gunboat 48.
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