making a boat unsinkable.

[Old Harry]

This is quite the thread resurrection - the original post is over 5 years old!

Its PBO, its always re-cycled stuff in there

 

[Graham376]

This is quite the thread resurrection - the original post is over 5 years old!

Yes but it shows the poster has the sense to do a search whereas many just start new threads on subjects already with multiple threads and answers to the question.

 

[Daydream believer]

Watched a mini transat being commissioned in France some years ago & they were putting blocks of polystyrene on board that were cut roughly to the inside shape of the bows & stern of the boat. Chap said that it was class rules to have sufficient buoyancy. Not seen it since though.

You're all obsessed with not sinking. How many of you have ever sunk? You're insured, I hope.

Lot of good being insured if you are dead from drowning !!! Still your kids might be rubbing their hands
But thinking about it, we have had a few sink on the moorings over the years & in the Crouch they have had a couple of small cruisers go down, along with the odd Dragon & Squib. & Squibs are supposed to have buoyancy tanks!!! We lost one in a squall in a race in the Blackwater 4 years ago. Not been seen since, But we rescued the crew Ok

 

[Red Panda]

Does anybody sell inflatable bags that you could take out of a locker and pull the cord and inflate inside the boat - one forecabin-size and another similar to (say) fill a stern quarter berth? would it be enough?

Yes, small buoyancy bags like these are frequently used in kayaks and canoes to fill unused space that you don't want filled with water when swamped.
Some use empty wine bags - though for your purposes, you're gonna have to throw a BIG party!
EDIT - OK, so they don't self-inflate, but then I didn't properly read your post!

 

[chris dyer]

Chris, James Baldwin agrees with you totally re building water tight air filled spaces - he wrote an article about how he managed to make his Pearson Triton 28' sloop Atom very close to being unsinkable by adopting this approach.

The article is here - lots of other good voyaging info on his website as well.
Atom Voyages - In Search of the Unsinkable Boat

Excellent article. He seems to have covered all of my suggestions.

 

[john_morris_uk]

Excellent article. He seems to have covered all of my suggestions.

Sadly, much of the benefit he claims is psychological only.
If it was as easy as he thinks it is, naval architects and boat builders would be jumping on the ideas.
See my earlier comments from several years ago. It’s not just a matter of having a barely floating hull. It’s all about which way up it’s going to float and IMHO I don’t think replacing your standing rigging with dyneema so the mast can easily be cut free to aid stability is such a good idea either.

 

[Old Harry]

Sadly, much of the benefit he claims is psychological only.
If it was as easy as he thinks it is, naval architects and boat builders would be jumping on the ideas.
See my earlier comments from several years ago. It’s not just a matter of having a barely floating hull. It’s all about which way up it’s going to float and IMHO I don’t think replacing your standing rigging with dyneema so the mast can easily be cut free to aid stability is such a good idea either.

Have you tried to cut dyneema

 

[Daverw]

PBO arrived today and refers to self inflating buoyancy system that uses CO2 to inflate witching 5 minutes.

 

[Yellow Ballad]

A friend has a Rustler 31 which a previous owner had custom air bags made out of inflatable dinghy material (PVC?) to fit his cockpit lockers and I think Vberth. Obviously needed inflating pre voyage and you couldn't use the storage areas but on long trips you could have a "spring clean" and leave the unless stuff. I think it was a requirement to get the boat "rated" for the AZAB race.

 

[Old Harry]

PBO arrived today and refers to self inflating buoyancy system that uses CO2 to inflate witching 5 minutes.

stow the life raft below in a valise & pull the painter when req

 

[davidej]

Now that's a good idea.

Drive up and down the highways annd byway and collect all the discarded drink bottles you can find.

You will be doing the environment a favour as well.

 

[William_H]

Following on from what John Morris said the location of the buoyancy is important to the stability of the boat when flooded. ie not much help if boat is unstable to the point of capsize when flooded but still floating. Hence buoyancy in the bow and stern will not help stability. A typical boat gets its stability and intial righting moment from the buoyancy of the chine area. (even if chine area is curved. f this fllls with water you lose that stability. Hence for a typical sail boat the best location for buoyancy is along the sides at and below the normal water line. This is the area usually filled in for bunks and seats. So IMHO sealing these under bunk areas to make tanks is the best way to keep her afloat but also in a manner that it can still be sailed or at least sheltered in by the crew. If the hull is punctured from the outside in this area then yes stability will be lost but you will keep water out of the hull. If she is swamped from capsize etc then water will lie along the center bilge.
So just seal the area or fit the side seats/bunks with inspection ports to allow checking and drying out. ol'will