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maxingout · 15-07-2011, 21:44

This looks like another flippin cat thread.

bill good · 15-07-2011, 22:56

I've felt "not happy" many times on mono's in heavy conditions but the cat seems to be more stable in similar conditions.

sailingaway221 · 16-07-2011, 04:04

Quote:

Originally Posted by S/V Illusion

The practical righting moment of any cat is zero. Any monohull is better than 0 and therefore an improvement. No gadget can change the above.

LOL .....

David_Old_Jersey · 16-07-2011, 04:32

If you have 80 odd foot of hull under you (whether a multi or a mono) you would need to be acting like a complete dick to flip either.............

niel12 · 16-07-2011, 04:46

Agreed, but wave power have made me shake and wee before and that was on 44' Cat!

SailFastTri · 16-07-2011, 05:04

Sorry to contribute to this "doomed" thread

but I will side-step the direct question of mono vs multi, except to make these points: The way to open anyone's mind is through experience and knowledge. They both have pros and cons, and every boat design involves trade-offs and compromise. A much higher percentage of multihull owners have had extensive monohull ownership experience than the other way around.

Instead I'll focus on the "flippable" question and state my view that probably 98+% of the cases of multihull capsize are a direct result of operator error carrying too much sail for conditions; not any different than driving a car too fast around a sharp bend. Monohull capsize is more likely as the direct result of being rolled by waves, but they are more forgiving of operator error related to steering and sail handling in overpowering winds.

I've never seen any statistics, but judging by experience and reading believe multihull capsize probably happens most often to racers who are deliberately pushing their boats to the edge. Most often it is when sailing downwind -- when a sudden slowing of the boat (whether by accidental round-up from unbalanced sail configuration or helm error, burying the bow or other accident) causes a sudden rise in apparent wind. Second most frequent is failure to reef or lower sails at the onset of a strong squall or weather front, and third is carrying too much sail in gusty conditions and failing to "reef for the gusts".

See my first post on this forum, which was how to avoid these errors. http://www.cruisersforum.com/forums/...tml#post138314

niel12 · 16-07-2011, 06:43

Thank you for the info, each and every contribution is apprechiated and i believe that if only one multihull or mono hull benefited from this gloomy dead thread we would have achieved something.

niel12 · 16-07-2011, 06:50

Quote:

Originally Posted by SailFastTri

Sorry to contribute to this "doomed" thread

but I will side-step the direct question of mono vs multi, except to make these points: The way to open anyone's mind is through experience and knowledge. They both have pros and cons, and every boat design involves trade-offs and compromise. A much higher percentage of multihull owners have had extensive monohull ownership experience than the other way around.

Instead I'll focus on the "flippable" question and state my view that probably 98+% of the cases of multihull capsize are a direct result of operator error carrying too much sail for conditions; not any different than driving a car too fast around a sharp bend. Monohull capsize is more likely as the direct result of being rolled by waves, but they are more forgiving of operator error related to steering and sail handling in overpowering winds.

I've never seen any statistics, but judging by experience and reading believe multihull capsize probably happens most often to racers who are deliberately pushing their boats to the edge. Most often it is when sailing downwind -- when a sudden slowing of the boat (whether by accidental round-up from unbalanced sail configuration or helm error, burying the bow or other accident) causes a sudden rise in apparent wind. Second most frequent is failure to reef or lower sails at the onset of a strong squall or weather front, and third is carrying too much sail in gusty conditions and failing to "reef for the gusts".

See my first post on this forum, which was how to avoid these errors. http://www.cruisersforum.com/forums/...tml#post138314

I WOULD CINCERELY LIKE TO THANK EVERY ONE BUT I BELIEVE EVERY MULTIHULL SAILOR SHOULD STUDY THOSE POSTS THEY ARE GOLD.

sabray · 16-07-2011, 06:57

Read "the race". Great story about big multis racing around and some of the design challenges

nautical62 · 16-07-2011, 07:07

Not all cats are built the same.

The Iroquois for example have many instances of flipping over. In contrast, the builder of the Catalacs has offered a reward for anyone who can document a hull even coming out of the water. Nobody has done so.

Event_Horizon · 18-07-2011, 00:56

Quote:

Originally Posted by niel12

About 3 years ago i designed a unit i called catbrake. I employed the services of a Architect/ Engineer who assisted me with the design and since i have been playing with a database of the various parameters of wind strength, wind direction, wave height, time of day, longatude/latetude and the various posistions of the catbrake when employed. The objective of this was to build a database of relative conditions so that when certain conditions are experieced catbrake will be automatically employed. The catbrake design will bring a catamaran to almost standstill on top of a wave without the use of a drogue or a parachute or ropes. To employ the catbrake you would need to upgrade your hydraulic capacity. This is not a selling stint as i have not yet produced it comercially but would like any input.

Hey Niel, this post has me a little...confused/concerned. Feel free to be as technical as you wish in your response to this.

You say we'd need to "upgrade [our] hydraulic capacity" which I take to mean we'd need to have a piping system on the boat able to pass large amounts of water. Since you're designing a brake, does this mean you plan to fire a jet(s) of water to "brake" the boat? This sounds...very hard to do even if you didn't have to make things practical.

Secondly, the database and auto-deployment sounds neat. Just not sure how it would be practical. I don't see how you will be able to measure wave height without a very expensive system on board. I mean, you could go with accelerometers placed all over with a very high powered computer modeling system chewing the data real time, which would be the poor mans way and inaccurate over long periods of time. Or you could use a topographical radar system mounted on the mast to measure the difference between itself and the crests and troughs of the waves directly adjacent to you. Either way it's big bucks.

niel12 · 18-07-2011, 02:37

The increased hydraulic capacity is hydraulic oil via a inline booster pump which will activate and drive the catbrake. The principle is actually so simple that we calculated that you can actually bring the cat to almost stand still position. No water jets are employed but more than that i can unfortunatly not reveal.

In terms of data base of condisions, was the idea to compile data over a period of time which could be measured against current condisions to determine activation mode thus hopefully implimentation time can be reduced. In terms of wave height yes, agreed that could be problematic as you pointed out that excercise might be costly. I think the solution here would be to allow the skipper to add certain data manualy.

I built a scale model at the time and fitted the catbrake pneumatically to test the implementation, set perameters and determine sensor placings. We had the model in water and created a current "per sae" (we did not measure the water speed of the current we created) We just wanted to determine if a cat will reduce speed and actually stop. The test was succesfull. We also determined that the bow remained on coarse and was not swayed in any way which confirmed to me that the application is correct.

Please understand that the catbrake is not patented and for this reason full disclosure is a problem. The reason why it was not commercially developed was that the South African economy could not afford it and i shelved it.