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**boatman61** · 26-03-2021, 08:08

Quote:

Originally Posted by Talbot

I sailed a catalac for many years, and whilst undoubtedly the slowest boat to windward, their hull form allowed a great speed ability in the right conditions. Nobody has capsized a catalac (unmodified) but I do know of one 9m that pitchpoled.

The solution - sailing is serious, don't be unseamanlike. sail within your boat and your own capabilities.

That's a fact..

My top speed on a Catalac 9 running downwind with just 1/3rd jib out was 18.5kts as I surfed down a wave..
This was running down the W coast of Portugal.. hairy to say the least..

eaglemac · 26-03-2021, 08:45

1. Too much sail up for conditions... Follow the old rule of reef early and reef deep.

2. Lack of understanding of where the center of gravity and center of applied force are on a multihull vs a keel equipped monohull, and how these change with changing wind and sea conditions.

3. Failure to turn on the engine/engines and use them when faced with heavy seas, especially the nasty nearly vertical seas which can come when encountering a fast moving frontal boundary such as those that race across the Pacific at 20 to 30 kts with a wall of 10 ft breaking seas in front like a snow avalanche in the mountains. Never leave the autopilot to drive the boat without a human on watch. Heavy seas coming from the forward quarter, abeam or astern all can lift the center of gravity above the critical point where both hulls stay in the water. Use of engines can change the location of the center of force driving a cat and they can be most helpful in keeping both hulls in the water, even when the sails are the primary source of motive power.

4. Lack of experience "surfing" a cat in following ocean swells or breaking seas. One of the great advantages of a cat is the ability to surf waves in a variety of conditions. Experienced cat sailors can use open ocean swells and even large breaking seas to achieve high speed runs which along with the knowledge of course made good and average heading sailed can cut many hours and days off sailing time on long crossings, and surfing can quickly help move a cat out of the most dangerous side of approaching storms to the "safe" zone when tropical storms of hurricanes moving at 15 to 25 kts approach. On the other hand, surfing without understanding where the vessel center of gravity and center of forces are can result in pitchpoling and capsizing.

5... One can learn a lot about the art of not capsizing by sailing a 16 or 18 ft cat. Find someone who is good with such boats and learn well, do not think that because a small cat can be sailed with one hull out of the water that larger boats also can do that. that is the 5th way cruising cats and multi hulls capsize...

6... Paint the underside of your multi hull Coast Guard Orange, and put some reflective material on the sides and stern of the hulls. There be holes and moving mountains out there in the seas. A blue and white hull looks like the ocean to those searching... Coast Guard Orange can be seen by human eyes and video scanning equipment.

john manning · 26-03-2021, 12:30

Before buying a catamaran I researched this question. That was in 2008. The only real investigation I found was a report on catamaran stability by the RYA in England.

They looked in detail at every reported capsize they could find. The conclusion was that catamarans do not capsize. The only instances of catamarans ending upside down were all pitch-pole events. All had the same cause. The catamarans were travelling fast (faster than the wave fronts) downwind. All ended up burying a bow into the back of a wave, nearly stopping the yacht, and having the following wave lift the rear of the yacht.

This report was limited to cruising catamarans over 30ft long. Racing catamarans and over-rigged small catamarans are a different matter.

qwerme · 26-03-2021, 14:21

Quote:

Originally Posted by john manning

Before buying a catamaran I researched this question. That was in 2008. The only real investigation I found was a report on catamaran stability by the RYA in England.

Do you happen to have a link to the report? I am interested in reading it.

john manning · 26-03-2021, 14:59

Quote:

Originally Posted by qwerme

Do you happen to have a link to the report? I am interested in reading it.

Sorry cannot find my downloaded copy. It was two computers ago. It also appears that the RYA have taken it off their web publications. Possibly because they are now selling a book on the subject.

chrisr · 26-03-2021, 15:05

Quote:

Originally Posted by john manning

Before buying a catamaran I researched this question. That was in 2008. The only real investigation I found was a report on catamaran stability by the RYA in England.

They looked in detail at every reported capsize they could find. The conclusion was that catamarans do not capsize. The only instances of catamarans ending upside down were all pitch-pole events. All had the same cause. The catamarans were travelling fast (faster than the wave fronts) downwind. All ended up burying a bow into the back of a wave, nearly stopping the yacht, and having the following wave lift the rear of the yacht.

This report was limited to cruising catamarans over 30ft long. Racing catamarans and over-rigged small catamarans are a different matter.

one of the few sensible comments in this thread...

cheers,

conchaway · 26-03-2021, 15:30

I know that most people don't have a degree in physics, so let me try to illustrate: Take a football. Glue a weight along the bottom away from the strings. Roll it over in a tub of water. What happens?
Take a piece of 2x6 about 8" long. Flip it over in a tub of water? What happens. END OF CASE!

BigBeakie · 26-03-2021, 18:47

Quote:

Originally Posted by conchaway

I know that most people don't have a degree in physics, so let me try to illustrate: Take a football. Glue a weight along the bottom away from the strings. Roll it over in a tub of water. What happens?
Take a piece of 2x6 about 8" long. Flip it over in a tub of water? What happens. END OF CASE!

Let's amend that for clarity and to be more realistic:

Take a football shaped object with holes in the top ( like companionway, portholes, hatches etc) that can let water into the football. Glue a ( very heavy) weight along the bottom away from the mast, err I mean strings. Roll it over in a tub of water. What happens? >>> it SINKS!
Take a piece of 2x6 about 8" long. Flip it over in a tub of water. What happens? >>> it FLOATS! END OF CASE!

There, that's better

44'cruisingcat · 26-03-2021, 19:39

Quote:

Originally Posted by Cat_sailor

I have tried getting some thoughts on this article before in other forums, but often it turns into unconstructive fights over cats vs monos.

Im hoping the cruisers forum is different!

That would be a first!

barryglewis · 26-03-2021, 20:30

The article claims the centre of gravity will move vertically as the designs beam is increased or decreased.
How is that?

Automatic sheet gadget release that depends on angle of heel were tried in the early 60s and dumped because at sea cats can get quite a heel on the side of a wave

44'cruisingcat · 26-03-2021, 22:21

The simple answer to the question posed in the title:

In the vast majority of cases, they don't.

Seabeau · 27-03-2021, 01:56

Quote:

Originally Posted by Cat_sailor

I have tried getting some thoughts on this article before in other forums, but often it turns into unconstructive fights over cats vs monos.

Im hoping the cruisers forum is different!

I find the article interesting and I believe the information to be accurate. Thanks

https://www.catamaranfreedom.com/why...for-beginners/Attachment 234924

I suggest you review the excellence treatise , "Heavy Weather Sailing" by Adlard Coles who concludes that the shallower a vessels hull and appendages are, the safer that vessels will be from knockdown by breaking waves. Shallower drafted vessels simply slide sideways when stuck.
Subsequently, the number of hulls is immaterial.

aqfishing · 27-03-2021, 02:09

Quote:

Originally Posted by barryglewis

The article claims the centre of gravity will move vertically as the designs beam is increased or decreased.
How is that?

Automatic sheet gadget release that depends on angle of heel were tried in the early 60s and dumped because at sea cats can get quite a heel on the side of a wave

The wider the beam (of a cat!) the more stable, i.e. your centre of gravity moves down increasing your GM. The opposite is true the narrower the beam. Assuming everything else stays the same!

Well that is my basic understanding. I am not sure this will hold true in monohulls, but the author is specifically referring to cats.