Cat Capsize Lake Macquarie

[Jim Cate]

Originally Posted by smj

This is the storm https://www.tcpalm.com/story/weather...ago/315723002/
It was almost 30 years ago so my memory has slightly faded but it was on our first cruise on our first catamaran. I’d come from a monohull background and was amazed at how easily the monohulls were flopping over. I can’t be sure their masts were fully embedded in the water but it looked to me like a couple went over 90 degrees. This is what’s embedded in my memory from almost 30 years ago

thanks for trying, but I can't get the link to work without either turning off adblock or paying, and I don't want to do either.

Sorry that your memory has no more detail, for without that we can't draw many conclusions about the event. I'm still convinced that it is damn hard to create a 90 deg knockdown with wind alone. Others are free to disagree.

I might add that we experienced a 90 degree job in our previous boat. Winds were only in the mid 50s, but the sea state was big and chaotic. We fell off the top of what must have been a peaky compound wave and landed on our beam ends. Blew out lexan glazing in the hard dodger on the leeward side, bent stanchions and broke off our aux rudder wind vane blade. Green water coming into a Dorade near the deck center line. Had been slowly fore reaching under backed storm staysail and triple reefed main, doing a couple of knots at something like 60-70 degree AWA, lots of leeway, but not really hove to. We had been at moderate heel angles prior to the event, and came back up immediately (seemed like a week, though). Point is that it was definitely NOT instigated by wind alone, but the results were kinda upsetting!

Jim

[GILow]

Originally Posted by ozsailer

Still asking - does anyone actually know what the cause of the capsize was.





Greg H

Lagoon 440

I really want to say it ran into a mono....

But I won’t.

[mark_morwood]

I found lots of photos with spinnakers as part of the equation, but only a couple with no spinnaker. They are also not quite 90 degrees, but getting close.

[GILow]

I think the original assertion was “bare poles.”

[Jim Cate]

Originally Posted by mark_morwood

I found lots of photos with spinnakers as part of the equation, but only a couple with no spinnaker. They are also not quite 90 degrees, but getting close.

I'm sure that the participants thought those situations were "mast in the water, near as dammit" but in fact they look nearer to 60-70 degrees, and that isn't all that uncommon. It is those last 20 degrees that are hard to accomplish by wind alone... and that has been my point all along.

And neither photo shows "flat water"... their transient heel angles were certainly affected by sea state. And that lower pic... not much control left with keel and rudder up in the air! Bet there were some big laundry bills that week!

Jim

[chrisr]

Originally Posted by Jim Cate

I'm sure that the participants thought those situations were "mast in the water, near as dammit" but in fact they look nearer to 60-70 degrees, and that isn't all that uncommon. It is those last 20 degrees that are hard to accomplish by wind alone... and that has been my point all along.

And neither photo shows "flat water"... their transient heel angles were certainly affected by sea state. And that lower pic... not much control left with keel and rudder up in the air! Bet there were some big laundry bills that week!

Jim

the top one looks like a sports boat (ie big dinghy) and the bottom looks like an old IOR sort. neither are really representative if arguing monohull stability.

might as well compare a hobi to a typical cruising cat...

cheers,

[Chotu]

Originally Posted by Jim Cate

. It is those last 20 degrees that are hard to accomplish by wind alone... and that has been my point all along.

Jim

A point that is completely valid. There isn't really a momentum involved in going to 90 without the seas involved. As such, the sail basically "self reefs" as the boat goes farther and farther over. There is absolutely zero sail presented to the wind at 90 degrees, so absolutely no wind force is holding it there at 90.
.

[Sos]

Originally Posted by Chotu

A point that is completely valid. There isn't really a momentum involved in going to 90 without the seas involved. As such, the sail basically "self reefs" as the boat goes farther and farther over. There is absolutely zero sail presented to the wind at 90 degrees, so absolutely no wind force is holding it there at 90.
.

The wind will spill from the sails but there could still be wind pressure on the hull, especially modern wide stern types?

[arsenelupiga]

there is no doubt keeled monohul is more stable than cat.

'light is always better' crowd finds hard to admit this is one of weaknesses of their philosophy. Heavy cats can withstand more wind on anchor.

However, i find it tricky when mono laid down with sail or not, forces from keel (couple tons i guess) must be significant on hull and likely there is some giving going on and possibility of dislocation. Picture couple posts back - how could that keel survive mast in water event with couple bolts ??? Looks more like french joke.

[DefinitelyMe]

I've seen a couple of J24s go over with mast in the water, while sailing under White sails, due to wind alone. On one occasion an expert dinghy sailor was on board. He jumped onto the keel and helped to bring it up again. Another one had their chute up, got pinned down, cabin filled and they sunk. But J24s are notoriously under-ballasted. I think Adlard Coles mentions them specifically in his book 'Heavy Weather Sailing'.

I can't be sure, but I think our 36-foot heavy-displacement cruising yacht must have been laid on her ear during our last hurricane. The wind shifted very suddenly from S to W and picked up to over 110 knots sustained (measured by the weather station). The scale of the chart I was looking at stopped at 135kts so I don't know what the gusts were. Boat was on her mooring. We have shelves on both sides of the cabin, behind the setees. Stuff from the starboard side shelves ended up behind the books that were on the port side. One of the books ended up in the headliner of the deck head. Would have been choppy but no swells.

[mglonnro]

Originally Posted by Sos

The wind will spill from the sails but there could still be wind pressure on the hull, especially modern wide stern types?

There surely would be wind pressure on the hull. Also, at 90 degrees the mainsail would be in the water and I guess that would add some resistance as well.

[jmh2002]

Even when the mainsail is at 90 degrees (or thereabouts) the wind will be flowing horizontally over the sail and still exerting a 'force'. This is of course what can keep the boat pinned down in this position.

That is no different to the wind bending a tree. The tree or the branches bend down with the force of the wind, and this force keeps them bent down in this position until the wind reduces or stops.

[catsketcher]

Actually it is usually not the thing, to produce a force when the fluid flow is parallel to the object. Even plane wings have small angle of attack to create lift.

It may be possible to create enough force from the windage of the upper hull, when near 90 degrees, and for the immersed gunwale to produce enough lateral resistance to produce a torque sufficient to push a mono to 90 degrees. But there may be other effects too, that limit this. Someone would have to do the tank test. The windage of the hull structure causing rotation is a thing in multis and so there should be some effect in monos, much reduced however.

As to the thread, a friend said the cat that was the subject of the thread was sitting on its mooring last week, looking as good as new. So all good in the end.

[chrisr]

Originally Posted by catsketcher

Actually it is usually not the thing, to produce a force when the fluid flow is parallel to the object. Even plane wings have small angle of attack to create lift.

It may be possible to create enough force from the windage of the upper hull, when near 90 degrees, and for the immersed gunwale to produce enough lateral resistance to produce a torque sufficient to push a mono to 90 degrees. But there may be other effects too, that limit this. Someone would have to do the tank test. The windage of the hull structure causing rotation is a thing in multis and so there should be some effect in monos, much reduced however.

As to the thread, a friend said the cat that was the subject of the thread was sitting on its mooring last week, looking as good as new. So all good in the end.

that's good to know...but it would be even better to know what happened. how come the owner / skipper hasn't told all ?

if it was me, i'd be embarrassed as hell...but i like to think i'd do the right thing...

cheers,

[catsketcher]

Originally Posted by arsenelupiga

there is no doubt keeled monohul is more stable than cat.

'light is always better' crowd finds hard to admit this is one of weaknesses of their philosophy. Heavy cats can withstand more wind on anchor.

If you count the area under the stability curve, then this is not always the case. Even performance cats have tremendous stability as measured by the torque required to rotate them.

As to being light, all boats require weight to make them stable. That is because weight is part of the stability equation. A designer has to make the judgment as to when to stop adding weight. Even the heaviest boat could be more stable if someone added more weight to it. So no designer would like to make their boats lighter ad infinitum. To do so would reduce the boat's stability to zero. They design the hulls to cope with a certain weight, usually boats, like people, find it hard to keep the weight off. Hence the striving to keep the weight down. If you build a boat, there is always the pre-occupation with weight saving, so that the structure is light and you can carry more stuff.