Capsize Prevention Devices

[brian eiland]

I seldom sail with the main up at night and if I do it is with two reefs, regardless of wind forecast.

I think that just about describes my aftmast design with the genoa sail rolled up, and just my 'main-staysail' deployed.

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[BlueBell]

Auto inflate PFDs operate with a spring loaded pin that is held by a salt ring. When it is submerged the salt dissolves and the pin makes a hole in the CO2 canister.

This is essentially correct, however, the preferred trigger uses a pressure sensor releasing the CO2 after 4" - 6" of immersion in water.
The salt pellet design can be triggered inadvertently by splashing water, leading to miss-fires.
If purchasing an auto-inflate PFD, it is well worth the added cost to buy a pressure release version.
I used to sell inflatable PFD's.

Hydrostatic (Hammar) System: This design uses water pressure rather than simple surface moisture to activate. It only triggers when submerged to a specific depth (usually about 4 inches or more). Water pressure pushes a diaphragm inside the valve, which releases the firing mechanism. This prevents accidental inflation from heavy rain, humidity, or wave splashes

 

[brian eiland]

At one time I had a gentleman show interest in my aftmast concept, and doing some forum discussions this came up.

Then check out what the owner of Anna had to say in that link of his posting.

Anti-Capsize

It appears that HTMO9 is very concerned about the subject of capsize,...as have many multihull sailors since multihulls became increasing popular. I have been away from direct involvement with multihull design for a number of years now, so I am unaware of developments in anti-capsize hardware that likely has been in the works for a number of those years, particularly considering the large number of big foiling multihulls that have been racing the oceans. Surely these guys pushing these boats right at the 'edge' have developed some systems?....particularly the French sailors that seem so involved?

So I thought I would see what google had to offer, and this came up most immediately.

Anti-Capsize Technology and Systems
The purpose of this thread is to post systems available, discussions of the technology and reviews. This is a serious subject. Please back up statements with facts. Some systems monitor rigging structural condition as well so while most of these discussions might concern catamarans, owners of monohulls could be interested.

This one really caught my attention as it was somewhat like a rotating cleat system I employed long ago on the kick-up centerboards on the Lousiane 37 cat I imported, and our Firefly trimaran's centerboard.
ACS system
ACS, an anti-slip system for multihulls https://www.boatnews.com/story/29460/acs-an-anti-slip-system-for-multihulls
"Even today, multihull skippers still admit that they cannot do without it. At the start of this 2018 Route du Rhum, there are 9 boats equipped with ACS: both Ultimate and Multi50 (where this type of system is even made mandatory by the class). But ACS is also present on some boats entered in the RhumMulti category"
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This posting I started to agree with, BUT when I reread it a second time, I had problems with it.
"If you do get caught out, the least stress solution is to depower the boat completely, stop and quietly drift. Unfortunately, this is impossible with stayed rig multis. Dumped headsails and their sheets flog, shaking the whole boat, the mainsail gets pinned against the shrouds or flogs and steering becomes difficult as you have no speed, but must keep control. Any extras become a nightmare, especially if they don't furl properly.
These scenarios usually happen at 3 am with associated rain, change of wind direction and half asleep crew. They are rare, but only have to happen once to spoil your trip. What is not rare is worrying about them, which really should not be a part of an enjoyable cruise when the solution is so obvious."

You don't have to depower it totally,.. just reef it down to a safe size that is still balanced. That is what my 'mainstaysail' does. In the first place my aft mast rig is designed to carry the same sail area as a sloop that requires a considerable taller mast. My rig can be shorter to begin with, and even shorter at night, with just the simple act of rolling up that big genoa and sailing with the smaller, lower 'mainstaysail'.
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"I think the capsize of Anna is really instructive because it is an example of a large (57ft) well designed and built (Chris White) catamaran. The crew were doing things well up to the point they capsized. They were monitoring the weather by radar and using Mk1 eyeball. The great thing is that the skipper was gracious enough to write a journal about the capsize. I think the sailent points are in the paragraph attached."
https://www.cruisersforum.com/forum...hnology-and-systems-267200-3.html#post3663939

 

[brian eiland]

My rig on a much bigger cat,

a ultimate MotorSailer idea, Dynarig motorsailer

I did some quick doodles of the rigging based on your scale model. Of course the measurements need to be adjusted, this is just to get an idea of the rigging concept on a large catamaran design.
The rigging concept is growing on me.

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  Mr E.jpg​

 

[gonzo]

On the really beamy foiling catamarans, a floating device on the mast would need to have the buoyancy of almost one of the hulls. Even then, it would only keep the boat knocked down.

 

[brian eiland]

On the really beamy foiling catamarans, a floating device on the mast would need to have the buoyancy of almost one of the hulls. Even then, it would only keep the boat knocked down.

That would apply to even a non-foiling cat. I had thought of posting something like that,..but I wanted to avoid that subject and concentrate on PREVENTING capsize as much as possible.

 

[brian eiland]

Just ran across this posting by a fellow with a wishbone boom on his traditional mainsail,..

As to sheet release systems. Some of the highest loadings I get are when I am in beam sea (I try and avoid them but often can't - around an island or headland this can get very bad) and the windward hull drops into a trough and rips the rig to windward. Very shaky and massive acceleration and therefore force but hard to engineer a release system for.

If you sail like me just get scared of high loads. When the ropes start to twang you reef. Kankama has never thought about lifting a hull. Sail with a coward or become one and install an easy to reef rig. That should do it.

cheers

Phil

 

[gonzo]

That would apply to even a non-foiling cat. I had thought of posting something like that,..but I wanted to avoid that subject and concentrate on PREVENTING capsize as much as possible.

Then slow down and have a shorter rig. However, you can reduce the possibility of capsize, but it will always be possible.

 

[portacruise]

Separately from wind, can big waves also cause capsize, (tsunami, rogue wave, etc) or is it so infrequent- as to not be a consideration?

Going to a proper mono should prevent sustained capsize, ( with the possibility of repeated rolls), is that worse than capsize?

 

[brian eiland]

Wave induced capsize MUCH lower than wind induced...

What we can learn from Anna's Capsize

Chris White Designs A57 A 57 Cerulean power reaching in Caribbean tradewinds. Chris White Designs Spindrift 14m. Spindrift 14m Powercat. New Design.

www.chriswhitedesigns.com

In the book titled The Cruising Multihull, I wrote extensively on the subject of capsize. At the time I drew a distinction between wind induced capsize and wave induced capsize. At the time, I judged capsize by wind to be the less likely of the two, because the risk could be controlled by the sailor by reducing or striking sail and altering course. On the other hand there is far less that the sailor can do to avoid wave capsize if the conditions are sufficiently bad to roll the boat over by wave action alone.


In retrospect, I did not adequately consider the risk from short duration violent wind gusts. There have been two capsizes of Atlantic catamarans in the 20 years since that book was published. Both capsizes were from strong winds. One was an Atlantic 42 on Lake Michigan in 2004, the other was Anna, which happened a couple weeks ago in the South Pacific. Even though the circumstances were different, there is a remarkable similarity in how the boats were capsized.

 

[montero]

How often do catamarans venture into higher latitudes ?

 

[trip the light fandango]

Complete capsize of a catamaran or tri can be avoided by using an automatically activated inflatable sturdy balloon of proper size securely anchored at the top of a strong mast. The activation would occur when the top is barely submerged and activated by water pressure, not moisture. Same Principle as water pressure Auto inflate life jackets. But there still has to be a method worked out beforehand to right the boat from the side stance position,.

What if there were 3 balloons ,one for each hull as well, they need to be able to be reset suggesting air lines to each, pressure and vacuum so automatically stowed when no longer required. Ideally the mast would also release a drogue or a specially made storm jib so that it wouldn't collapse that was prepared as a precaution for unstable weather. Once the mast is facing the wind it would be a choice to release the air bag to act as extra wind resistance on the high hull or inflate the one submerged or both.

 

[portacruise]

What if there were 3 balloons ,one for each hull as well, they need to be able to be reset suggesting air lines to each, pressure and vacuum so automatically stowed when no longer required. Ideally the mast would also release a drogue or a specially made storm jib so that it wouldn't collapse that was prepared as a precaution for unstable weather. Once the mast is facing the wind it would be a choice to release the air bag to act as extra wind resistance on the high hull or inflate the one submerged or both.

Thanks for posting, fandango.
I think that the multi-hull should have a safety system or bunker built in where it is possible for occupants to be safe while the boat is lying on either side, when using an automated tip of mast air bag. If it involves escape hatches, attached insulated survival pod, or something more ingenious, to make it safer than capsize- so be it. Clinging outside to a slippery smooth capsized hull splashed with cold water and high winds, don't myself understand how that works? Rescue during those winds by another craft, might be more dangerous than waiting for safer/ more controlled conditions and the survivors clinging outside may perish by then.

It doesn't make sense for the crew to right the boat until the winds that caused it to tip have passed. There may be ways for the crew to self right the ship using by using additional air bags, as you pointed out. Also possibly using water pumped into bladders in or outside of hulls and just above the sea surface might help with righting. The fastest/safest/simplest/panic proof method automated by easy means (like the push of a button) that proves itself by testing, might be the way to go. Contrasted to an overturned multihull where the options are much more limited for righting. I agree with Gonzo that capsize will always be possible. Even with a proper mast air bag that is working properly, which is the only capsize "prevention" I see so far- things could go wrong. Leaks, broken off mast tips, boat lying flat without safety adaptations, etc. JMHO, hope this helps. Have fun!

 

[brian eiland]

What if there were 3 balloons ,one for each hull as well, they need to be able to be reset suggesting air lines to each, pressure and vacuum so automatically stowed when no longer required. Ideally the mast would also release a drogue or a specially made storm jib so that it wouldn't collapse that was prepared as a precaution for unstable weather. Once the mast is facing the wind it would be a choice to release the air bag to act as extra wind resistance on the high hull or inflate the one submerged or both.

I would invite you to go experiment on a smaller cat,...say a Hobie 16. See if that works with your air bags ...good luck!

 

[brian eiland]

Perhaps for our CRUISING cats we don't always need to follow the PERFORMANCE designs ....(with their tall macaroni rigs)

Here is an interesting analysis,

Are Performance Cruising Catamarans Safe? Stability & Capsizing​