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Go Back   SailNet Community > General Interest > General Discussion (sailing related)
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  #1  
Old 06-18-2007
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GZ curve

Hi every body.
Does any one knows were can I get a comparison chart on GZ curve for different types and models of sailing boats ( if any).
Thanks in advance
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Old 06-18-2007
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try boatdesign.net, there might be some help in there.

Good luck.
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Old 06-18-2007
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Thanks Starwindy for your info, it was the right place. By
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Old 06-18-2007
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Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice
Go here, this is all you need
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Old 06-19-2007
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Giuleta,
Thanks for your tip. Now, I did a comparison between two boats regarding Capsize ratio: one is 1.92 and the other is 1.99, Can you tell me how do I have to interpret this ratio?, the same in the Motion comfort: one is 25.77 and the other is 23.65 an the last, Hull speed one is 8.1 and the other is 7.77. I presume that this one is the average speed that the boat can give, is that right?.
Thanks in advance for you info.
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Old 06-19-2007
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Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice
Genesis, if you click in the white block with your right mouse button, where it says the things you want to know, you can read in the explanation of that.

Hull speed is the max speed a hull (displacement hull only), (not applicable to statre of the art planing hulls), can achieve, and its calculated based on lenght at the water line. The longer the LWL the faster that boat can go.

The formula is HS = (LWL) Power 1/2 X 1.34

It only works for boats that do not plane in the water.

Basically when a boat moves in the water it creates a wave that restriscts the increase of its speed. It will be trapeed in it own water displaced water.

When moving, a boat will create a wave in the bow and another wave in the rear, in the stern. When the boat gets near its hull speed the two waves will combine to make only one wave.

What happens is that the boat will be unable to go "over" its own wave, no matter how hard it is pushed, the wave just gets bigger and he can't go any faster.

That is when fine very good looking excellent nice sailboats like yours trully come to play...these very high effecient modern good looking hulls, called planing hulls, due to their flat appearance and low drag, are able to start "surfing" over the surface of the water, and once they do that, they start planing over the wave, then, no longer under the influence of the wave, they can accelerate further.....and fly as fast as the wind!!

Was that clear?

The photo bellow shows a boat that is going so fast the waves are really big. At this point, the Spi was hoisted and the boat starts to accelerate. The boat at this stage is not surfing yet. here is bellow 9 knots.



Once it starts surfing, the wave effect no longer apply all you have is a smooth wake, here it is going at around 17 knots.



I'll see if I have more

Last edited by Giulietta; 06-19-2007 at 02:39 PM.
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Old 06-19-2007
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Quote:
Originally Posted by Giulietta
Genesis, if you click in the white block with your right mouse button, where it says the things you want to know, you can read in the explanation of that.

Hull speed is the max speed a hull (displacement hull only), (not applicable to statre of the art planing hulls), can achieve, and its calculated based on lenght at the water line. The longer the LWL the faster that boat can go.

The formula is HS = (LWL) Power 1/2 X 1.34

It only works for boats that do not plane in the water.

Basically when a boat moves in the water it creates a wave that restriscts the increase of its speed. It will be trapeed in it own water displaced water.

When moving, a boat will create a wave in the bow and another wave in the rear, in the stern. When the boat gets near its hull speed the two waves will combine to make only one wave.

What happens is that the boat will be unable to go "over" its own wave, no matter how hard it is pushed, the wave just gets bigger and he can't go any faster.

That is when fine very good looking excellent nice sailboats like yours trully come to play...these very high effecient modern good looking hulls, called planing hulls, due to their flat appearance and low drag, are able to start "surfing" over the surface of the water, and once they do that, they start planing over the wave, then, no longer under the influence of the wave, they can accelerate further.....and fly as fast as the wind!!

Was that clear?
Mostly clear...at what point does the boom break?
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Old 06-19-2007
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Giulieta:Thanks very much for your VERY PROFESSIONAL AND CLEAR EXPLANATION.You answered all my doubts. Any other grafic information is very welcome.
Regards
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Old 06-19-2007
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Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice
what do you want to see?? A very very very good sailor??? or an ugly Exmoderator??

Here's a side view of a very pretty boat I saw once.

The first one, before she rides the wave...the second one riding the wave...look at the difference..the bow lifts off the water when surfing, and the difference in bow wake and water thrown out.





OK here are a few photos of a planing hull, these are from a very very very pretty ellegant good looking boat I found on the net. (The guy that owns is for sure a very very very good looking handsome extremely good sailor, also.)








CAN SOMEONE POST A PHOTO OF A DISPLACEMENT HULL?? PLEASE? i ONLY HAVE PLANING HULL PHOTOS.

Last edited by Giulietta; 06-19-2007 at 04:11 PM.
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Old 06-19-2007
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Hmm. Looks like a nice boat, but she have kind of fat ass.

P.S.
The only planning sailboat I ever had was a laser (and even that was my brother's). I can only try to imagine the thrill, excitement and joy of planing with a 40 footer...
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