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Old 27-03-2018, 11:39   #1
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Point of Sail Speed Difference ?

Hello

Beginner here and dont even know my point of sail speeds yet but hoping to figure out this weekend

What is your speed at each POS with the same wind speed ?
Make and Model of your boat might be useful for cruisers to compare
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Old 27-03-2018, 12:56   #2
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Re: Point of Sail Speed Difference ?

Rob,
There are charts that present this information for each (most) make and model of boat. They are called polar charts or polar diagrams, often referred to simply as the polar. They have curves representing different wind speeds and if you go to the appropriate wind angle on the chart you can read off the nominal boat speed for that wind speed and angle.

Google should find you plenty of examples.
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Old 27-03-2018, 13:25   #3
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Re: Point of Sail Speed Difference ?

Thanks I will check that out
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Old 27-03-2018, 13:43   #4
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Re: Point of Sail Speed Difference ?

Look at your polars, because every boat is slightly different.

In general, though, boats of medium performance or less tend to be fastest on a beam reach, and slower and slower as you approach either a dead run or hard on the wind. That is because on a beam reach you have maximum power from DRAG -- the wind simply pushing the boat without lift involved, without reducing the apparent wind speed with your own speed. You also get some lift on a beam reach.

Once you point closer to the wind than is optimum, speed falls off drastically.

Dead downwind you get no lift from the sails -- just drag. And your own speed reduces apparent wind 1:1. So this is slow.

The last two things is true of all sailboats.

Boats with better performance and with good sails in general sail fastest on a close reach. That is because a better performance boat with good sails has a better balance between lift and drag, and can use lift profitably at higher angles to the wind. With the wind ahead of the beam, your speed increases the apparent wind, and a boat with good sails can use that to sail even faster than on a beam reach.

Really FAST boats make a LOT of apparent wind. So you generally avoid ever sailing DDW in such boats. With enough speed, you can make your own wind and turn a deep angle into more of a reach, so this is fast making faster -- climbing up on your own speed. It's one thing which makes sailing fast boats more interesting, much more interesting, than sailing slow ones.
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Old 27-03-2018, 14:16   #5
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Re: Point of Sail Speed Difference ?

Quote:
Originally Posted by Dockhead View Post

Really FAST boats make a LOT of apparent wind. So you generally avoid ever sailing DDW in such boats. With enough speed, you can make your own wind and turn a deep angle into more of a reach, so this is fast making faster -- climbing up on your own speed. It's one thing which makes sailing fast boats more interesting, much more interesting, than sailing slow ones.
Yes it is
I sail a flying phantom catamaran for fun......just last weekend we went 19.8 knots with only 8-10 knots of wind. Takes a lot of work though.
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Old 27-03-2018, 14:27   #6
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Re: Point of Sail Speed Difference ?

Quote:
Originally Posted by RobD527 View Post
Hello

Beginner here and dont even know my point of sail speeds yet but hoping to figure out this weekend

What is your speed at each POS with the same wind speed ?
Make and Model of your boat might be useful for cruisers to compare
Here is an example of a Polar Chart for a cruising boat.
Search for one that is calculated for your specific boat.
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Old 27-03-2018, 15:00   #7
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Re: Point of Sail Speed Difference ?

Columbia 29
close-hauled, a little over 6 knots
close reach to broad reach a little over 7 knots
but I haven't been pushing her too hard yet or racing... I might embarrass the younger kids.
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Old 27-03-2018, 15:14   #8
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Re: Point of Sail Speed Difference ?

Two good mentions of polar diagrams above.

https://www.google.com/search?q=sail...grams&tbm=isch

Just be aware that sea state has a large bearing on boat speed and designer/builder produced polars are computer models of ideal conditions and they consequently tend to over estimate speeds, especially at higher wind speeds .
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Old 27-03-2018, 15:42   #9
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Re: Point of Sail Speed Difference ?

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Originally Posted by StuM View Post
Two good mentions of polar diagrams above.

https://www.google.com/search?q=sail...grams&tbm=isch

Just be aware that sea state has a large bearing on boat speed and designer/builder produced polars are computer models of ideal conditions and they consequently tend to over estimate speeds, especially at higher wind speeds .
because you are a newbie, this "beat cat cheat sheet" may be useful when competing with cruising cats.

Any cat will do better reaching and downwind than equivalent value mono regardless of wind strength, subject to helmsman commitment. So do not try to overtake them in these conditions.

For upwind below 12 kn true you will be beating most cruising cats, lowe better. Above 20 kn true, you will be staying behind.

Rougher the seas, better mono will do against cat upwind in any wind speed. Below 12 knots and rolly seas you will be beating cats a lot. That when engine turns on on average cat.

Go well, go SHELL !!
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Old 27-03-2018, 16:03   #10
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Re: Point of Sail Speed Difference ?

My purpose of the thread was not really to figure out my pos speeds or where to find them but to see what the speeds of others are but whatever I learned something about polar charts
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Old 28-03-2018, 09:51   #11
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Re: Point of Sail Speed Difference ?

More on the sea state. Different hull designs react to waves in different ways. When you compare the polars you may see 2 boats with closely matched speeds at all points. In reality they may be very different once you get in a chop if one cuts cleanly through waves while the other bounces and slams over them. This not only slows the boat it makes it much less comfortable. It is sometime estimated as some sort of measure of 'seakindlyness'. Difficult to quantify but very evident when experienced.
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Old 28-03-2018, 19:05   #12
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Re: Point of Sail Speed Difference ?

Get the ASA Sailing Challenge app. It's fun, educational, and will help you understand different points of sail with regard to different wind direction and wind speed, and eventually, will teach you how to get the most speed out of these conditions.

Really, it's a BLAST!

Aarrrgh!
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Old 28-03-2018, 22:56   #13
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Re: Point of Sail Speed Difference ?

Old boat won't have polars. So it's no use just saying go off and look at some polars.

I don't know about the OP's Hunter 33. A super quick google doesn't throw one up, but I'd challenge anyone to fine one for old 70s Prout.

The good news is that you make your own, it might take you a whole season though. OpenCPN has a polar diagram plugin.
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