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Old 20-07-2007, 18:16   #16
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I've never come close to flying a hull and have done close reaches in flat water up to 20 knots under full sail. My boat doesn't have dagger boards and depends on boat speed to track when going to weather. When overpressed she just slides sideways. On the other hand, I'm lucky to tack through 100 degrees.

If you notice, it's mostly dagger boards cats which , when pushed, get into trouble when the boards are all the way down. It's called tripping. Dagger boards definately perform better, but you have to pay attention. We sail boats that don't lean and our rigs have to unload in some way when overpressed.
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Old 20-07-2007, 20:55   #17
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Quote:
Originally Posted by rickm505
I've never come close to flying a hull and have done close reaches in flat water up to 20 knots under full sail. My boat doesn't have dagger boards and depends on boat speed to track when going to weather. When overpressed she just slides sideways. On the other hand, I'm lucky to tack through 100 degrees.

If you notice, it's mostly dagger boards cats which , when pushed, get into trouble when the boards are all the way down. It's called tripping. Dagger boards definately perform better, but you have to pay attention. We sail boats that don't lean and our rigs have to unload in some way when overpressed.
When you are "pushing" the daggerboard should NOT be all the way down. The only time the daggerboard should be 100% down is close hauled in light winds. For reaching, or stronger winds, the daggerboard should be lifted to some extent.

Statistically you may be correct about it being mostly daggerboard boats that capsize, but that would be because it's mostly in RACES that cats capsize, and most race boats have daggerboards. I would be surprised if the majority of cruising boat capsizes were boats equipped with daggerboards.
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Old 20-07-2007, 21:14   #18
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On my boat when you sail faster than 7 knots or so you don't need the daggerboards. Even up wind. They can help in a race upwind but aren't required for good footing. The Hulls are aysymetrical. The shape is the same as a Hobie 16 but blown up to 33'. At high speeds the boat is safer with daggerboards up. It can slip sideways if need be. However the boat will fly a hull regardless of daggers up or down. This also relates to weight/sail area, as well as draft/beam. These ratios will directly effect how and when your cat will fly a hull.
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Old 20-07-2007, 21:16   #19
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Quote:
Originally Posted by rickm505
We sail boats that don't lean and our rigs have to unload in some way when overpressed.
The best way for the rig to unload is by pushing the cat forward! fast!
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Old 20-07-2007, 23:00   #20
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About 22 knots you're pushing things. You have a pretty high rig and lots of sail area. Reef before you get to 20 knots wind.

I can't give you a "capsize" wind speed; 22 knots is the wind speed where wind force on sails = righting moment due to hull beam and displacement.

Your real weight when loaded for cruising is probably heavier and thus the wind speed increases slightly, but you should sail your boat conservatively with a rig like that.

And yes, full sail in 50 or 60 knots on a beam reach and you're over.
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Old 21-07-2007, 06:37   #21
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There is a good article on catamaran stability at: James Wharram Designs -Home of the self-build Catamaran.

Using that formula and in addition to your numbers assuming the CE of your sails is at 35' above the waterline, I get a static stability of 38 knots and dynamic of 23 knots.
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Old 21-07-2007, 09:31   #22
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Quote:
Originally Posted by mark_morwood
There is a good article on catamaran stability at: James Wharram Designs -Home of the self-build Catamaran.

Using that formula and in addition to your numbers assuming the CE of your sails is at 35' above the waterline, I get a static stability of 38 knots and dynamic of 23 knots.

This is a great article for this question!! You da Man!

Keegan
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Old 30-07-2007, 18:54   #23
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Keegan,

You can go to this site and pay a little and get some information.

Multihull Dynamics, Inc. - Home
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Old 25-09-2007, 09:30   #24
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I sail a St. Francis 48 and I have had one hull out of the water but the keel was still halfway in, 28 knots of wind main and genoa up during a race round of Noord Holland
The moment the hull came out the boat slowed considerable because the leeward hull was digging in and we let the sheets go speed was 21.5 knots at that moment
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Old 25-09-2007, 12:41   #25
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we let the sheets go speed was 21.5 knots at that moment






After you let the sheets go in a sutuation like that how do you steer?

I know cats are different.

Round up?
Fall off?
Steady as she goes?
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Old 25-09-2007, 14:38   #26
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We first fell off and reduced sail area after that .
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Old 25-09-2007, 15:01   #27
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We first fell off and reduced sail area after that .
That is what I read.

But I have not found a good article about "how" to sail a cat with monohull background.

I suppose you try to remember it and if you don't, you either go over or are lucky and will remember it the next time!!
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Old 25-09-2007, 15:16   #28
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Just come and sail with me I will teach you , normally I never overpower my boat but with that race I could not resist. It takes a lot of wind and sail area to overturn a cruising cat and if you sail in a conservative way like I normally do and you have a performance oriented cat you will reach average cruising speeds of 8 to 11 knots for a 43 ft cat.
I can send you the ce sailing manual if you send your e mail addres and on page 19 I believe you will find the app. wind speeds thast tell you what sails to use and when to reef.

Greetings

Gideon
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Old 25-09-2007, 16:09   #29
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theres a bloke in aus called craig schionning who is putting out a 40 ft cat with a very big mast, i reckon therell be a few people sailing it that will get a few surprises in the hull coming up out of the water category
sean
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Old 25-09-2007, 17:01   #30
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Easing the sheets big time seems like a reasonable "emergency/instantaneous" response.
It is amazing how the flapping of sailcloth can freak out novice sailors though.

One thing though is to keep the end of the sheets under control so that you do not have to fetch them back along with getting the sail down.
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