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Stepped hull design in cats? #279706
07/01/15 09:27 AM
07/01/15 09:27 AM
Joined: Jul 2001
Posts: 1,253
Columbia South Carolina, USA
dave mosley Offline OP
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dave mosley  Offline OP
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Joined: Jul 2001
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Columbia South Carolina, USA
Anyone tinkered with or have reasons that a stepped hull design would or wouldn't work with our type of cats?
Sea Hunt and Glassmaster are claiming doubling of fuel efficiency and increase in speed with their stepped hull designs.
If that's true, then what would it do for us?
ps patent pending....!


The men were amazed, and said, "What kind of a man is this, that even the winds and the sea obey Him?" Matthew 8:27





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Re: Stepped hull design in cats? [Re: dave mosley] #279707
07/01/15 10:15 AM
07/01/15 10:15 AM
Joined: Feb 2007
Posts: 402
Punta Gorda, FL
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jkkartz1 Offline
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Punta Gorda, FL
Look for the ORMA cat, Region Aquitaine.

It was not very successful.

Re: Stepped hull design in cats? [Re: dave mosley] #279709
07/01/15 11:42 AM
07/01/15 11:42 AM
Joined: Nov 2011
Posts: 381
SE MI / NE IN
rehmbo Offline
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rehmbo  Offline
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Steps would be hugely draggy at less than planing speed = 95% of the time. Those big power boats can do it as they have 7 kazillion horsepower on the back that can quickly get them up on the step.


Jeff R

H18, C2 USA1193
cramsailing.com
crescentsail.com
Re: Stepped hull design in cats? [Re: rehmbo] #279711
07/01/15 02:20 PM
07/01/15 02:20 PM
Joined: Jun 2001
Posts: 12,310
South Carolina
Jake Offline
Carpal Tunnel
Jake  Offline
Carpal Tunnel

Joined: Jun 2001
Posts: 12,310
South Carolina
Originally Posted by rehmbo
Steps would be hugely draggy at less than planing speed = 95% of the time. Those big power boats can do it as they have 7 kazillion horsepower on the back that can quickly get them up on the step.


agreed...that's a high speed planing hull shape. We don't go fast enough to take advantage of that.


Jake Kohl
Re: Stepped hull design in cats? [Re: dave mosley] #279712
07/01/15 02:30 PM
07/01/15 02:30 PM
Joined: Jul 2001
Posts: 1,253
Columbia South Carolina, USA
dave mosley Offline OP
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dave mosley  Offline OP
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Joined: Jul 2001
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you do Jake!


The men were amazed, and said, "What kind of a man is this, that even the winds and the sea obey Him?" Matthew 8:27





Re: Stepped hull design in cats? [Re: dave mosley] #279715
07/02/15 12:32 AM
07/02/15 12:32 AM

S
Scarecrow
Unregistered
Scarecrow
Unregistered
S



Mattia back in 2003. Lets just say they only built one.

[Linked Image]

[Linked Image]

There are two issues stopping it working.
1. As stated above speed.
2. Venting. for the steps to make a difference you have to be able to get air to them. a normal cat (non foiling) would require vent cutouts to go almost up to the gunwales to achieve this. If you can't get air in the step actually sucks you down onto the water and adds drag.

Attached Files
bella,alzata sailing.jpg (110 downloads)
Mattia beach.jpg (108 downloads)
Last edited by Scarecrow; 07/02/15 12:33 AM.
Re: Stepped hull design in cats? [Re: dave mosley] #279743
07/03/15 01:58 AM
07/03/15 01:58 AM
Joined: Apr 2012
Posts: 190
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Bille Offline
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Bille  Offline
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Joined: Apr 2012
Posts: 190
That Tri , l'Hydroptere ; they use stepped hulls.

Here is a good shot of them ; it turtled after a 60K
run.

http://yachtpals.com/hydroptere-4036

Bille

Re: Stepped hull design in cats? [Re: dave mosley] #279745
07/03/15 06:36 AM
07/03/15 06:36 AM
Joined: Nov 2011
Posts: 381
SE MI / NE IN
rehmbo Offline
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rehmbo  Offline
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SE MI / NE IN
I think Hydroptère is one of those corner-case boats. Huge amount of sail power allows it to work in windy conditions.

You could probably do this on an 18' boat too, but would only be "fast" and up on the step when its blowing over ~20kts. In all lesser conditions I'm quite certain that normal style hulls would be faster.


Jeff R

H18, C2 USA1193
cramsailing.com
crescentsail.com
Re: Stepped hull design in cats? [Re: rehmbo] #279752
07/03/15 01:21 PM
07/03/15 01:21 PM
Joined: Apr 2012
Posts: 190
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Bille Offline
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Bille  Offline
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Joined: Apr 2012
Posts: 190
Originally Posted by rehmbo
I think Hydroptère is one of those corner-case boats. Huge amount of sail power allows it to work in windy conditions.

You could probably do this on an 18' boat too, but would only be "fast" and up on the step when its blowing over ~20kts. In all lesser conditions I'm quite certain that normal style hulls would be faster.


I Totally agree !
To make a stepped hull work ; you'd need Copious amounts
of power, to drive it.

The thing that impressed me most about Hydroptère ; is
the speed they'd get out of conventional sails !!

Bille


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