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schoonerdog · 04-03-2010, 15:04

I think the thought of the foam making the boat unsinkable is a common misconception. It takes a lot of bouyancy to compensate for batteries, engines, mast, rigging, etc. The foam doesn't even have a fraction of what's needed. To make something unsinkable you need to have structural watertight compartments. The lower these compartments are, the faster they submerge, and the more lift they provide more quickly. So below the sole of the cabin is ideal. Of course, the lighter the boat, the less space you need in these compartments, so foam does help a lot there.

Quote:

Originally Posted by downunder

Schoonerdog,
I don't currently have a vessel but am researching what is available and your point is great re sinking cats.
One of the vessels I am considering is the new FF46 the 1st of which is underconstruction due in water around October 2010. follow the website link here Picture Gallery - FreeFlow 46 Construction
New pictures available. As you see there will only be the possibility for water ingress into the motor and shaft compartments as the tank and other compartments are sealed. Lightly loaded or 1/2 tank capacity I imagine the sole will be above waterline.

With hulls and all vessel infused foam construction it will be unsinkable. As vessel construction continues I will watch this. Lightly loaded I don't doubt the sole will be above waterline. As you suggest shereline could be raised to ensure this. Will raise this with builder at Santuary Cove boat show.
cheers

H2OHOBO · 11-04-2010, 05:40

Not true schoonerdog, I have seen Privilege 482's that filled with water and did not sink, two filled one hull due to through hull problems and went around in circles with one motor running for as long as 24 hours, two went over reefs and lost keels and filled completely yet floated with bridge deck sitting on the surface, one was towed 10 miles and one 30 miles in this state with rig intact and a person in the cockpit.

schoonerdog · 14-04-2010, 14:20

I wouldn't expect a Privilege to sink easily. Privilege is an example of a boat that has a lot of structural bouyancy, the bows are water tight, their engine compartments aft are water tight and their extended nacelle will act as a water tight compartment when it gets to the point where it's submerged. There are many types of very popular cats (perhaps the most popular cats) that wouldn't do that, I have pictures of scuba divers sitting on their bows as they were being refloated. Basically it's pretty easy to figure this out. If your forward bow compartment doesn't have a water tight bulkhead that extends up over the water line, it's not going to help in a breach. If you can walk to the back of your hull and see the transom without a bulkhead in the way, water will flow back and forward throughout the entire hull until the hull sinks and brings the catamaran down sideways. Prout 45s have water tight access doors to prevent this, FPs have bulkheads in the back, some catamarans don't have any of this because they wanted that space for charters.

schoonerdog · 14-04-2010, 14:42

this is one that's being raised by some divers

muskoka · 14-04-2010, 21:17

Our FP has a 2m crash compartment in each bow, a flotation chamber underneath the aft bunks and separate watertight engine compartments. The cockpit deck is supported on a large rigid foam block. Plus I'd imagine the water & fuel tanks provide some flotation. I'd classify it as 'hard to sink' rather than 'unsinkable'.

I think without dedicated flotation compartments and watertight engine compartments any boat will sink**. Which the above picture confirms!

**The possible exception being something like an Etap which has foam flotation built in and will float when completely flooded.

downunder · 14-04-2010, 23:25

Attached is some photos of cats after the recent Cat 3 Cyclone in the Whitsundays, Australia.

You can notice a Seawind being refloated as well as the bows only floating of what I think is a Lagoon. Both these appear to be charter cats run by Whitsunday rent a yacht (WRAY) These are the only cats I know that sunk most others were driven ashore as follows.

Factor, perhaps your industry connections can track down more info.

This info helps grafically in the choice of a catamaran and the need for adequate watertight compartments as mentioned by schoonerdog.

More photos in my album.

Joli · 15-04-2010, 03:05

Downunder, I'm curious, if they weren't driven ashore and holed, how did they sink? If they simply flipped over you would think they would have large amount of entrapped air? Did they possibly stand on end, bow up and flood? The same goes for the Lagoon in the earlier picture.

The boats must have been oriented in a way that allowed water to flood the hulls. Did anyone see them flip/sink?

The boat on the beach must have been on a mooring. The bridle is still tucked under the tramp.

Quote:

Originally Posted by downunder

Attached is some photos of cats after the recent Cat 3 Cyclone in the Whitsundays, Australia.

You can notice a Seawind being refloated as well as the bows only floating of what I think is a Lagoon. Both these appear to be charter cats run by Whitsunday rent a yacht (WRAY) These are the only cats I know that sunk most others were driven ashore as follows.

Factor, perhaps your industry connections can track down more info.

This info helps grafically in the choice of a catamaran and the need for adequate watertight compartments as mentioned by schoonerdog.

More photos in my album.

44'cruisingcat · 15-04-2010, 05:23

Possibly hit by another boat which had broken free of it's mooring

Palarran · 15-04-2010, 06:06

Quote:

Originally Posted by muskoka

Our FP has a 2m crash compartment in each bow, a flotation chamber underneath the aft bunks and separate watertight engine compartments. The cockpit deck is supported on a large rigid foam block. Plus I'd imagine the water & fuel tanks provide some flotation. I'd classify it as 'hard to sink' rather than 'unsinkable'.

I think without dedicated flotation compartments and watertight engine compartments any boat will sink**. Which the above picture confirms!

Mine is almost exactly the same. One thing I haven't checked is how good the sealing is between the engine compartments and the main cabin. All the electrical and refrigerant lines penetrate the bulkhead about 2' above water line. If they are fairly well sealed, I would also classify it as hard to sink. If they allowed free water flow, not good. I also have 5 bilge pumps per hull, two in the main hull section, two in the engine compartment, and one in the transom compartment.

My own personal fear on cats is being overrun by a breaking wave. My cockpit absolutely will not drain that much water which leads to the next wave filling it also until something gives. I've thought about just cutting the whole floor section out below my sliding door. That may be excessive and as yet, I have only heard of one cat taking a wave which partially flooded it.

schoonerdog · 15-04-2010, 08:51

it's really hard to poop a cat, I've seen waves so high because of a Bahamian rage I couldn't see their top due to my bimini and the boat simply lifts up and very little water got in. I'm surprised to hear about your cockpit drainage. My PDQ and my St Francis both had excellent drainage (holes so big you can stick your arm through them). That's a key advantage of a cat is water can drain directly down from your cockpit to the ocean.

schoonerdog · 15-04-2010, 08:58

I think that some cats with no structural bouyancy (or little structural bouyancy) fill the breached hull, gradually moving more and more sideways until finally they are pulled in sideways. I wouldn't be surprised if they flipped upside down or bobbed with their bows up. Of course the point of structural bouyancy is to prevent this. A PDQ 44 for instance will sink that hull only about a foot or so, a PDQ 36 will do about the same. I'd expect a FP to be pretty good, a Prout 45 to be very good, and an African Cat to also be excellent. The St Francis 50 will do well, the SF 44 (mine) will have the bow standing above the water in a mid hull breach but aft it will probably be awash. Not great, but not sunken.

SeaKing · 15-04-2010, 12:57

Hey schoonerdog, look at that, you are at 999 posts . Just one more and you qualify as really spending too much time on here!

What's up, Are you sailing this year?

downunder · 15-04-2010, 15:15

Joli,

I am not sure yet as to what happened to the sinking cats. I think they may have been hit by other vessels as suggested by 44 crusingcat.

Most of the vessels that washed up broke their moorings and there were four ashore in the area by those flooded sinking cats. Most damaged were mot proberly prepared, sails not taken down or moorings not checked or strengthened by divers.

Certainly the watertight integrity of those concerns me and will be a factor in my selection of a vessel.

I was hoping Factor with his industry contacts may be able to persue the matter.

**Cotemar** · 21-04-2010, 19:09

YIKES! It had no mast, the salon door was open; it was swamped. Clearly a Fontaine Pajot, French-built cat in the upper thirty to lower forty foot range. You don’t see this everyday!

I inquired around the island the next day to learn the cat was abandoned in terrible weather somewhere near the Bahamas and was left dismasted to its own devices. It had just been found the day before, seventeen miles north of San Andres in the open sea, drifting westward in the currents and trade winds.

However disturbing the scene, the incident is a testament to the “unsinkable” rating of European-built catamarans. Brands such as Lagoon, Fontaine Pajot, and Catana utilize watertight bulkheads, foam sandwich construction, and other buoyant materials that actually qualify their cats to be certified unsinkable.

When you think about it, that’s pretty darn nifty! Not all cats are created equal and some catamaran brands are not certified to meet unsinkable standards and will not remain floating if totally swamped. Those “Brand X” cats will plummet to the bottom if they take on too much water. It’s a good question to ask when shopping for a cruising catamaran.

And the proof is in the pudding. The Fontaine Pajot full of water drifted across the WILD and rough central and western Caribbean and there she sits, still on the surface.