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Old 19-07-2007, 20:27   #1
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Flying A Hull on a Cruising CAT!!!

Anyone ever 'fly a hull' on their cruising cat? Or worse, flip it over due to wind forces? If so, what kind of cat and under what kind of conditions?

My cat is 46' long 24' wide and weighs 27,500lbs. It has a 195 sq. ft main at 167 sq ft Jib. About how much wind would it take to flip it over?

With full sail on a beam reach could I flip it over at 50knots? 60knots? Of course the rig could go first or the sails could blow, but assuming that this did not happen when would it go over? I dont know how to calculate it but it would be intersesting to know.

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Old 19-07-2007, 23:41   #2
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Not fly a hull, but go the windward one about 1/2 out of the water (i.e. lots of bottom paint showing). Full main and genoa, 25 knots of wind, 15 knots of boat speed. Fast enough to realize that the boat was being pressed way too hard.

Anyway your sail areas are totally too low. Are they in sq m? (then they would be too big).

I need to have a sailplan to figure out the heigh of the center of effort of the rig. If you really are considering such small sails (triple reefed main + storm jib??) then 50 or 60 knots is a good guess.
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Old 20-07-2007, 02:12   #3
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Quote:
Originally Posted by Keegan
With full sail on a beam reach could I flip it over at 50knots? 60knots? Of course the rig could go first or the sails could blow, but assuming that this did not happen when would it go over? I dont know how to calculate it but it would be intersesting to know.

keegan
Are you planning an insurance claim or something?
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Old 20-07-2007, 04:00   #4
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Keegan, did you mean to type sq meter? With the conservative sail plan you've indicated, you could pretty much sail through a hurricane(kidding). Seriously, my boat which is 2/3 the LOA of yours has more sail area than that!

It's so conservative, it just doesn't look right. Your boat has to have a mast height of around 60 feet. When I do the math, your head sail is somewhere around 400 sq feet and the main around 700 sq ft.
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Old 20-07-2007, 07:30   #5
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Quote:
Originally Posted by rickm505
Keegan, did you mean to type sq meter? With the conservative sail plan you've indicated, you could pretty much sail through a hurricane(kidding). Seriously, my boat which is 2/3 the LOA of yours has more sail area than that!

Yeah, I was way off on my sail area. It was really late when I posted last night. Here are the numbers:

MAST HEIGHT 17.60 m (57' 7")

Main Sail Area 72 m / 775 sqft
Head Sail 45.1 m / 455 sqft





Anyway, with full sail, where is the point when one if the hulls comes completely out of the water?

On cruising cats that are about 35' to 40 ft' I would guess it would happen much easier depending on beam, weight and sail plan.

Keegan
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Old 20-07-2007, 08:50   #6
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It depends on a lot of things, including the hull shape I would think. I believe most modern cruising cats (at least the production kind I've seen) are built so parts break before the boat itself would tip over. The most likely scenario for tipping over, in my opinion, is breaking waves not wind. Of course, I'm not saying it couldn't happen, what do I know.
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Old 20-07-2007, 09:32   #7
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Hello Keegan,

You can go here to see/read about a cat that flipped - Sailing diving charter Thailand Burma Myanmar

I think it's a 36'er or so. I also remember reading about one of the bigger alloy cats lifting a hull gently somewhere on one of the Langkawi Regatta sites.

I'm no expert in anything, but having full sails up in anything over 30-35 knots is just asking for trouble! If you try it let us know how it goes!!

Best - J
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Old 20-07-2007, 09:39   #8
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The reading that I've done on the subject indicates it's usually wave action which flips cruising cats. I would guess start reefing at 20~23kts true wind and get everything down by about 50-55kts assuming that you're downwind. I would imagine that the boat will let you know that she's unhappy about the sailplan a long time before disater strikes.
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Old 20-07-2007, 11:23   #9
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Here's a 52ft Wharran trying hard.


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Old 20-07-2007, 11:40   #10
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FLYING HULL

I was sailig the boat to Trinidad two weeks ago and we had full sail up and 26-27 knot gusts. The hull was nowhere near flying at that wind range.

Dont get me wrong, I am not trying to fly a hull just trying to understand where the hairy edge is.

Keegan
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Old 20-07-2007, 12:02   #11
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Maybe the best read on this subject is Chris White's "The Cruising Multihull". White goes in depth on the impact of wind and wave on multihulls, and tactics for avoiding capsize from either. In real situations, either CAN cause capsize, just as they can flip a monohull, and it's the dynamic of both that must be watched closely!

A flying hull does not necessarily mean you're going over, but it DOES mean sails need to be reefed! Yikes! It's like getting knocked over past 45 deg on a mono and not reefing afterword. Not good.
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Old 20-07-2007, 12:08   #12
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Quote:
Originally Posted by Brandywine
Maybe the best read on this subject is Chris White's "The Cruising Multihull". White goes in depth on the impact of wind and wave on multihulls, and tactics for avoiding capsize from either.

Yes, I have read Chris Whites book and that actually made me want to know where the hairy edge is for my own cat. I think that alot of Crusing Cat owners beleive that their cat cannot be blown over by wind and that is not a correct belief. The question is how much wind, for a particular boat design?

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Old 20-07-2007, 12:15   #13
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Originally Posted by Keegan
I think that alot of Crusing Cat owners beleive that their cat cannot be blown over by wind and that is not a correct belief.
I do believe, for example, that my Cat was designed to break (boom, mast, fittings) before she will tip over due to wind alone. Of course, that's almost as bad and dangerous so who would want to sail like that...

Wave action, like breaking waves, is a whole nother ballpark. As is pitchpoling.
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Old 20-07-2007, 14:40   #14
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capsize

There have been two recent capsizes of big cats recently. One in the Atlantic, and one in the Pacific. I believe they were both captained by a delivery crew. There was an article about the one in the Atlantic in the print version of Soundings. I think it was April 2007 issue, but I wasn't able to find anything about it on the internet.

Here are some other cat-astophes...

COAST GUARD RESCUES 2 FROM CAPSIZED CATAMARAN **Video Available**

OREGON / Intense search for sailboat's missing crew / Large catamaran left S.F. last week, was found Friday

I have personally seen the Gunboat fly a hull past us in the Chesapeake, in only 20 knots of wind, with a reef in the main. Exciting to watch, but I'd rather have a little more positive buoyancy than that.

Susan
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Old 20-07-2007, 17:58   #15
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I have flown the hull a couple of times on my 33' csk cruising cat. It's not that big of a deal if you know what you are doing. It is not a common practice however. On a close reach in 15 knots the boat will fly the hull at 15 knots hull speed or so. This will only happen if you are sheeted in too hard. You get the same speed with the hull in the water. Obviously you do not have this amount of sail area up if you are cruising.
When you start flying a hull on any cat you enter the "red" zone. Some cats really shouldn't do this and will flip very soon. Some are more comfortable operating near the "edge" I.E. Gunboat
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