Visit our Popular Forums

ErnestV · 14-02-2020, 07:40

Quote:

Originally Posted by chrisr

but a cat like that should never flip in flat water just due to wind pressure. should be impossible...the force needed should be more than sails / rig can bear

i wondering if these spirited 380s have a design issue to maybe nose dive..bury the leeward hull ?

cheers,

Cats are different.
Monos depower with every degree they tilt, so it should be near to impossible to lay a mono flat by wind power alone.

A cat, when heeled, lifts it weather hull and presents the underside of the bridge to the wind, and thus does not reduce the attack area a lot. Actually as soon as a cat lifts its weather leg its getting dangerous really fast (valid for bridge deck cats only, not sporty cats with a trampoline). You need to have quite some experience to depower before it is too late - tacking makes the situation worse as the centrifugal forces further increase the heel.

Simon B · 14-02-2020, 10:40

Yep, my father aways sail cats are the most stable upside down with the mast in the water!

conchaway · 14-02-2020, 13:33

OMG! ANOTHER catamaran going over and staying over. ( I thought you weren't allowed to say that on this forum; did I misunderstand?)
In order to avoid castigation, let me here and now state that I do not believe such a thing could ever happen!

Firstbait · 14-02-2020, 14:52

you guy's have got to remember this is the lake where the monos try to do cart wheels like the windsurfers. monos only lay flat. bah

catsketcher · 14-02-2020, 22:21

Really? Why are these old chestnuts still in circulation?

Sorry to break it to you but your dad is wrong - very wrong - at least in the instance of large cats. The Spirited 38 was righted with the pull of a medium sized outboard boat pulling it hard. It turned back upright with its mast still up. You can right a cat this size with a line leading to the inverted waterline.

If you pull my cat (which is also 38ft) with a line on the waterline water when upright and dry in the bilge it will speed along behind your boat. If you pull it sideways the line will probably break and we will go sideways before that occurs. Put the line 2 metres up and the same will happen.

What people don't get is the huge difference between Hobie cats and bridgedeck cats. The huge amount of water inside the hulls lessens the stability of any vessel. This is why sinking ships roll over and tankers have lots of baffles in the tanks. It is called the Free Surface effect. The free surface effect massively reduces stability. (If you want to see it for yourself, play with your kids in the dinghy. Capsize it and it is really easy to roll back upright when totally full. It's a fun game)

End result - an inverted bridgdedeck cat is much much LESS stable upside down than right way up.

Be careful with hearsay from people who are not experts in their field. There are lots of things people say about multis that were untrue when I first heard them in the 80s and still are today.

**Jim Cate** · 14-02-2020, 22:59

^^^^^

Nicely explained, Phil, but I doubt if any of the folks who promulgate these old chestnuts are listening... and there seems to be an infinite supply of them!

As you know, I'm a happy mono sailor, but even I get tired of reading that particular fable or its doppleganger of monos on the seabed.

Jim

catsketcher · 15-02-2020, 01:50

Gday Jim

The mono being most stable on the seabed is pretty wrong too. Especially composite boats have lots of flotation embedded in the structure. To pull a mono off the seabed is not terribly difficult. Getting it above the water (when full of water) is almost impossible without breaking the boat.

6 minutes into this video,

https://www.youtube.com/watch?v=OFlGdiWQzco&t=804s

it shows that you can raise a mono from the seabed by just pulling on the mast. Then when it gets to the surface, you need to sling it. It requires more effort to lift when far OFF the seabed. The amount of effort required to lift it up, off the seabed is much lower than the effort required to sink a mono by pulling it down with a force. So monos are not more stable on the bottom. They are more stable floating.

Even though a mono can sink, many cats come pretty close too. And due to the free surface effect, this can cause them to capsize. So all boats can take on water, some will sink, and some will capsize when holed. Not a heap of difference really.

conchaway · 15-02-2020, 15:19

On this site, you are not allowed to say that a catamaran will go over and stay over. WATCH YOURSELF, buddy!

GBR134 · 16-02-2020, 11:02

As a monohull cruiser sailor and ex Hobie 16 racer I appreciate I’m not competent to answer. I have no knowledge but the idea that you can’t capsize any cat by windforce alone seems unlikely to me given the right ‘inputs’. The idea that the mast would fall down or sails blow out first also seems unlikely and certainly would put me off buying that model.

I have no idea of the stability of or righting problems for a bridge deck cat - however for all practical purposes I assume once turtle it stays turtled without outside assistance.

All boats have the potential to get into mega strife and to a certain extent need a modicum of skill and understanding in the soft link between helm and mainsheet.

ozsailer · 16-02-2020, 14:27

From reading the posts and comments made by some posters that they either know the owners or know someone who knows them. Lots of info about the boat, recovery etc but not one on why the capsize occurred. Just from a safety side of things I would like to know what happened to ensure I dont do the same thing.

Greg H
lagoon 440
Oz

Mr B · 16-02-2020, 14:48

Quote:

Originally Posted by catsketcher

Gday Jim

The mono being most stable on the seabed is pretty wrong too. Especially composite boats have lots of flotation embedded in the structure. To pull a mono off the seabed is not terribly difficult. Getting it above the water (when full of water) is almost impossible without breaking the boat.

6 minutes into this video,

https://www.youtube.com/watch?v=OFlGdiWQzco&t=804s

it shows that you can raise a mono from the seabed by just pulling on the mast. Then when it gets to the surface, you need to sling it. It requires more effort to lift when far OFF the seabed. The amount of effort required to lift it up, off the seabed is much lower than the effort required to sink a mono by pulling it down with a force. So monos are not more stable on the bottom. They are more stable floating.

Even though a mono can sink, many cats come pretty close too. And due to the free surface effect, this can cause them to capsize. So all boats can take on water, some will sink, and some will capsize when holed. Not a heap of difference really.

Thats a good description of build up on the anchor lines after floods,
It will sink your boat from the weight on the anchor chain,

In the 2011 floods after the cyclone went thru, In the Burnett river at Bundaberg,
The Boats that werent sitting in the tops of trees,
The 140 odd boats that were lost were pulled under with the Hyacinth and logs and trees that came down the river and piled up on anchor chains and just pulled the boats under,
You do need to move your boat out of a river before the floods come down, usually a day or two after a cyclone has gone thru,
Thanks for the informative video,

GILow · 16-02-2020, 15:09

I think the important point is being missed here.

It is clear that Lake Macquarie is too dangerous for sailing boats of any kind and everyone should give it a wide berth.

(Thus leaving the best anchorages for me.)

**Jim Cate** · 16-02-2020, 17:45

Quote:

Originally Posted by GILow

I think the important point is being missed here.

It is clear that Lake Macquarie is too dangerous for sailing boats of any kind and everyone should give it a wide berth.

(Thus leaving the best anchorages for me.)

Uhh, Matt, what is your draft again? The entrance channel may just keep you from enjoying those anchorages... does for us!

Jim

44'cruisingcat · 16-02-2020, 18:10

Quote:

Originally Posted by conchaway

OMG! ANOTHER catamaran going over and staying over. ( I thought you weren't allowed to say that on this forum; did I misunderstand?)
In order to avoid castigation, let me here and now state that I do not believe such a thing could ever happen!

Probably much that you believe isn't true.