How to salvage a capsized cruising catamaran

[Cotemar]

RIGHTING A SMALL CAPSIZED MULTIHULL?

Righting a small capsized multihull at sea, unless outside help is available, is probably not a feasible option with current technology. Best to leave the craft as it is, where the crew is safe, and await rescue.

Modern satellite position indicating systems now offer very quick and easy location for a floating, but disabled multihull, whereas a sunken monohull has no such option.

When the opportunity arises, and outside assistance is available, the most successful righting system for any small multihull, is to tow the capsized boat fore and aft, attaching a bridled tow line to the end that is floating the highest.

Which end depends on how the boat is floating.

As the boat begins to move, the lowest end, be it bows or stern, will begin to sink, and even more so as the water inside rushes to the low end.

The boat should then flip back upright, bow over stern or visa versa.

If the above procedure does not work, then try flooding the end that needs to sink, by adding some crew weight which should be ready to abandon ship once the end concerned starts to go under.

If this fails, try towing the other direction. Some controlled flooding may also be required.

Towing sideways will not work - fore and aft is the easy and only way to do it.

[KJThomas]

Originally Posted by Cotemar

RIGHTING A SMALL CAPSIZED MULTIHULL?

Righting a small capsized multihull at sea, unless outside help is available, is probably not a feasible option with current technology. Best to leave the craft as it is, where the crew is safe, and await rescue.

Modern satellite position indicating systems now offer very quick and easy location for a floating, but disabled multihull, whereas a sunken monohull has no such option.

When the opportunity arises, and outside assistance is available, the most successful righting system for any small multihull, is to tow the capsized boat fore and aft, attaching a bridled tow line to the end that is floating the highest.

Which end depends on how the boat is floating.

As the boat begins to move, the lowest end, be it bows or stern, will begin to sink, and even more so as the water inside rushes to the low end.

The boat should then flip back upright, bow over stern or visa versa.

If the above procedure does not work, then try flooding the end that needs to sink, by adding some crew weight which should be ready to abandon ship once the end concerned starts to go under.

If this fails, try towing the other direction. Some controlled flooding may also be required.

Towing sideways will not work - fore and aft is the easy and only way to do it.

As a big ship as well as a catamaran driver. I do not see any reason why righting bow over stern using the ship to tow wouldn't work. Although there is no example of it being done that I am aware of. The hardest part would be convincing the Master to try it. Container ships have very good control with VP props. A bulky will be more difficult.
One capsized GBE in Auckland harbour was towed upright using a tinny. Small aluminium dinghy.

[UpOnStands]

the G4 was righted laterally by what appears to be 2 bridles on the starboard chain plates. Believe they used their chase boat to do the towing.
Logical as the inverted hull provides significant height and acts as a useful fulcrum.

[Comix Bay]

Originally Posted by donradcliffe

Ccruising catamaran capsizes are rare events, but they do happen. After the survivors have been rescued, what do you do with an upside down cat in the open ocean, which shows no inclination to sink.

I've given the matter some preliminary thinking, but would love to hear from anyone who has successfully salvaged one.

My plan would be to use a power boat and a diver.

First, the diver would get rid of any sails that are deployed. Second, dive down to the tip of the mast and attached a lift bag(s) with 1000 lb capacity. The bag would be inflated to about 25%, to allow for fourfold expansion from 60 ft to the surface. Finally the diver attaches a long line where the shrouds attach to the mast, and to the rescue boat.

The next phase is for the rescue boat to pull sideways to the hulls until the boat heels about 20%. After that, the bag should take over and you should end up with a stable boat with the mast tip near the surface and about 105 degrees of heel.

The rescue boat is then attached with a long line to the upper hull, and pulls until the boat is about 80-85% of heel. At that point, nature should take over and the boat should go fully upright.

Looking at the loads involved, a 35,000 lb Lagoon 450 cat with a 25 ft beam has a righting moment of 35,000 x 25/2 = 440,000 ft lbs, roughly the same whether it is right side up or upside down. The pull you will need on the mast (say 44 ft from the pivot point) is 440,000/40 = 10,000 lbs. To get that pull, the rescue boat will need 500+ hp, and you will need a line and attachments with a breaking strength of 50,000 lbs to get a 5:1 safety margin. You would need at least 5/8 inch spectra or 1.5 inch dacron/nylon to avoid line partings.

Once you are pulling on the upper hull, the righting arm is down to 25 ft, but the righting moment you have to overcome is much lower. I would expect that you will need less than half the earlier maximum pull in this phase.

I doubt that you will break the mast or rigging, as they are sized to fly a hull (440,000 ft lbs righting moment) with some safety margin.

Comments and suggestions are always welcome.

donradcliffe

Good question, and timely. After watching a video clip of the rescue of three people from an overturned cat the other night off DR (I think) I was wondering the same thing, "how would they get her upright again??" Do you just punch holes in her and let her go to the bottom, or let her drift and become a hazard to navigation?? I don't think the freighter was going to tow her into a port. If I remember correctly she was about 400nm off the FL coast.

[seabreez]

Originally Posted by Just Another Sa

"The next phase is for the rescue boat to pull sideways to the hulls until the boat heels about 20%. After that, the bag should take over and you should end up with a stable boat with the mast tip near the surface and about 105 degrees of heel."

When you wrote 20%, did you meant 20 degrees?
If not please explain what that means.

If yes, how many lift bags you intend to use?

I salvaged 2 sail boats, one was a monohull 37 foot and a catamaran 41. The monohull was in 35 feet deep and laying on it's side. It went down in a storm and a reefed main sail was still on. To lift it, we used 4 farm tractor inner tubes and a pvc flexible tubing. We got the used inner tubes from all tire shops in the area and more. We had a diver install the tubing end near the engine and the other ends have it come out of the vessel near the companionway. Then installed the inner tube to the forward end and inflated it until we had a response from the vessel. Then the second inner tube was installed in the engine room and inflated until there was a response. The response was that the forward end and the rear were moving or rocking up and down.The next two inner tubes were installed in the cabin close to the ceiling and inflated some. There was a long hose connected to this inner tube and routed to the outside. We closed all and started inflating the inner tube. We did not want to go too fast. The vessel started raising and we moved away as we did not know how fast it would go up and break surface. It did break surface faster than we thought but stabilized quickly. We then moved in and used the pvc tubing to pump out water and it floated on it's own and we towed it to shore. The inner tubes were only used to displace water. They inflated bigger because of expansion and with no damage to the vessel.

The second vessel was a 41 foot catamaran. It overturned in a storm and was still floating upside down. The mast was still on and touching bottom. We used the same principle. Water displacement. We placed 3 inner tube in the forward section of each hull, with long enough lines to inflate them from the outside. All hoses were tagged and grouped together. Then 3 inner tubes in the rear section of each hull. and 3 in the main salon. When we placed the inner tubes the hulls were full of air, keeping the vessel afloat. We were afraid that we were going to lose this air and the vessel would sink. We started by inflating the forward ones as we wanted to raise the bow and sink the rear. The bow came up some. The bubbles were also coming out to a point that we thought the inner tubes were busted. It was only air from the inside coming out. Then we inflated the main cabin a lot. The bow raised up almost 3 feet out of the water. Then we added a lift bag at the mast head. I do not remember the size. It was not that big. The air bag came right up to the surface. Then a slow tow a bridle to each hull to bring the forward end to right up. The mast started to lift and came out of the water. This did not take much effort. Then in motion we inflated the rear inner tubes and the vessel raised to the surface. Then we carefully came along side and started pumping. When the pumping started we stopped towing as we wanted to keep things stable. It was a success and the vessel was towed to shore.

This takes a lot of planning, a good plan, a group effort, and very good communications. And only one person in charge. Or two in control if you want to divide the work. You will have to STOP, Assess and Plan the moves as you see fit for the circumstances. Take your time and do not stress the vessel more than you need.

Work safe!

If you require additional information, just post on this forum and I can give you my email or phone number and I will try and answer all of your concerns. Regards,

[donradcliffe]

No two situations are going to be the same.

In the case of the recent Atlantic 57 capsize, it was 400 nm north of the DR. The first problem is finding the wreck again. You would need a waterproof GPS/satellite transmitter with a long battery life which you could attach to a rudder or something sticking up before you abandoned the boat. The Yellowbrick YB3 could work, as well as a Delorme InReach in extended tracking mode, but you would probably want them in a waterproof pouch.

While a Lagoon might, the A57 is not going to sink with a few holes in the hulls. It will be a hazard to navigation until it is towed in or hits shore somewhere. Since it has probably turned from an asset into a liability, it will probably join the rest of the floating derelicts wandering around the Bermuda Triangle. In a few weeks it will be stripped of anything valuable.

According to this thread, getting the cat upright at sea could be troublesome and expensive. I have to agree that my plan A isn't going to work. I watched the video in post #32 again, and pulling backwards by the bridle just made the boat slew off to one side. It sounds like the best plan would be to salvage what was left of the rig and tow the boat inverted to a crane in sheltered water.

I suspect it would cost in the 6 figure range for a 1000 mile salvage operation, and fixing the boat would cost more. However if the insurance policy was anywhere near the $1.6 million cost new it might make sense.

[Ozifrog]

Two points that spring to mind.
WAVES capsize boats ( obviously associated with wind.)
Secondly, 60 feet underwater, that's about 20 meters. Three atmospheres of preasure... so the volume of the air bag will triple, not quadruple as suggested.
Cheers

[Kinta Ray]

Someone said that most large cats wouldn't have enough reserve buoyancy to be able to be righted but this will depend on the design, Schionnings, Gunboats and dare I say any performance catamaran will remain afloat and high in the water with the ability to be able to be righted but with designs like Lagoon, FPs or any other caravan style boat I think that recovery would be almost impossible unless in sheltered waters or close enough to shore to be towed in. In most cases that I have read about the performance boats that have been flipped(except if they break up) have been recovered while capsized cruising boats are usually abandoned. Please correct me if I am wrong.

[seabreez]

Originally Posted by Kinta Ray

Someone said that most large cats wouldn't have enough reserve buoyancy to be able to be righted but this will depend on the design, Schionnings, Gunboats and dare I say any performance catamaran will remain afloat and high in the water with the ability to be able to be righted but with designs like Lagoon, FPs or any other caravan style boat I think that recovery would be almost impossible unless in sheltered waters or close enough to shore to be towed in. In most cases that I have read about the performance boats that have been flipped(except if they break up) have been recovered while capsized cruising boats are usually abandoned. Please correct me if I am wrong.

I am not trying to correct you, however may I add that like everything if a salvage was done once and failed, I am sure that the salvagers learned from their experience. After a few tries you attack a problem from a different angle. The cat I salvaged was in excellent shape once ashore and I believe it is still operational. The first one I salvaged was a monohull and the second was a cat and I assure you the operation was similar but much different.

Where is this catamaran that that needs to be salvaged?

[JPA Cate]

Seabreez,

Its name was Leopard, and it was somewhere about 400 nautical miles north of Puerto Rico, it was not, afaik, left with an EPIRB or DeLorme Tracker on it, just somewhere out there in the Bermuda Triangle.

Ann

[tp12]

Originally Posted by Ozifrog

Two points that spring to mind.
WAVES capsize boats ( obviously associated with wind.) ...

I agree that waves can capsize a catamaran though I think it's much more likely to be wind. Hence all the information regarding avoiding capsize by reefing, dumping the traveller or mainsheet etc...

[seabreez]

Originally Posted by Ann T. Cate

Seabreez,

Its name was Leopard, and it was somewhere about 400 nautical miles north of Puerto Rico, it was not, afaik, left with an EPIRB or DeLorme Tracker on it, just somewhere out there in the Bermuda Triangle.

Ann

Thanks Ann for your quick reply. If the catamaran was a bit closer... I was seriously thinking of going down to assist with the salvage... Regards.

[leftbrainstuff]

Originally Posted by tp12

Thank you; where is this from? Do you know who authored it?

That's a pretty common static factor safety applied during design when actual in service loads are unknown.

The actual FoS will wary by designer and manufacturer. It's an empirical design limit only. Ie there is no warranty or guarantee offered or implied.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[tp12]

Originally Posted by leftbrainstuff

That's a pretty common static factor safety applied during design when actual in service loads are unknown.

The actual FoS will wary by designer and manufacturer. It's an empirical design limit only. Ie there is no warranty or guarantee offered or implied.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

Thanks mate. I understand the application for sizing rigging etc but I'm trying to find this evidence that production builders are applying these figures in sizing the mast/rigging to fail prior to capsize.

A mate of mine is a rigger, he races with us occasionally (he's a gun; pro sailor) and he's never heard of it either. He laughed at the idea.

I read the article linked above where it discusses doing that but it reads as more of a discussion paper for consideration rather than being a production requirement for anyone - I hope I'm making sense.

[SV DestinyAscen]

Originally Posted by tp12

Thanks mate. I understand the application for sizing rigging etc but I'm trying to find this evidence that production builders are applying these figures in sizing the mast/rigging to fail prior to capsize.

A mate of mine is a rigger, he races with us occasionally (he's a gun; pro sailor) and he's never heard of it either. He laughed at the idea.

I read the article linked above where it discusses doing that but it reads as more of a discussion paper for consideration rather than being a production requirement for anyone - I hope I'm making sense.

I'm skeptical that rigging design considers it. If it is the norm, we'll see more masts with designed breaking points about a foot above the deck with those rivet/joints. You find them in some older boats, but I can't think of a new boat with that.