Making a Boat Unsinkable with Expanding Foam

[Adelie]

Originally Posted by AllezCat

I intend to rebuild the crash-boxes during this refit.
In another thread a poster mentioned the compartment was full of water due to leaking deck fittings.
Would it not make sense to fill them with foam(expanding or other)?
Surely lighter than being full of rain water - and better during impact/hull breaching...
At least have an inspection hatch.
In regards to the expanding bags - would the material be prohibitively heavy. Like a life raft...Maybe the foam would be lighter?...

The problem with foaming a crash box is you can't do maintenance inside afterwards. Water leaks in around deck fittings will now be in the box with no way out. Long term the foam won't stay completely bonded to the walls and hull of the box so the water will seep down and sit against the hull causing blistering maybe, or against bulkheads causing rot if they are wood.

Discrete removeable blocks that can be installed and removed thru the access hatch will allow maintenance.

[AllezCat]

Originally Posted by Adelie

The problem with foaming a crash box is you can't do maintenance inside afterwards. Water leaks in around deck fittings will now be in the box with no way out. Long term the foam won't stay completely bonded to the walls and hull of the box so the water will seep down and sit against the hull causing blistering maybe, or against bulkheads causing rot if they are wood.

Discrete removeable blocks that can be installed and removed thru the access hatch will allow maintenance.

Thx - good info

[Chrisgo]

Originally Posted by Adelie

It might float on its side, or more likely upside down unless the mast were gone.

Ahh, forgot about the mast. I do wonder if it would work though. Off shore, liferaft gone, etc...would you be able to hang on to a mostly submerged boat, (assuming dropping a couple of tons of lead would make it float somewhat). Lots of ballast with the water inside

[Adelie]

Originally Posted by Chrisgo

Ahh, forgot about the mast. I do wonder if it would work though. Off shore, liferaft gone, etc...would you be able to hang on to a mostly submerged boat, (assuming dropping a couple of tons of lead would make it float somewhat). Lots of ballast with the water inside

Assuming the boat has external bolted on ballast:

The bolts would need to be removed quickly, less than 30m, more like less than 10m, and do this while standing in rising water. The Ranger 26 I once helped replace bolts on had 8 or 10 3/4" bolts, so rate of removal would be tough.

Once most of the bolts are removed the last 1, 2 or 3 are going to break or rip thru the fiberglass they go thru.

Even if the bolts don't break the hull on the way out, all the bolt holes are open to the sea. Right side up they let more water in, up side down they let air out, the net result is the same the boat continues to sink.

I like the way you are thinking about this outside the box. Ditching the keel during initial stages of an emergency is a non-starter as far as I can see, but it made me think about later stages when water inflow has been stemmed if not stopped.

If you could stem the inflow then ditching the keel might provide you with a place to stay if:
1. The boat has enough form stability to remain upright with mast removed and keel dumped. If all the anchor chain and every bit of metal possible is placed in the keel sump before ditching the keel, and every bit of weight possible is removed from topsides, this may be possible.
2. Flopper stoppers and any other means possible are placed to maximize roll damping. Without the rig and keel AVS is going to go way down, as will roll moment of inertia so capsize becomes a much more likely proposition.

My feeling is that if you get things stabilized enough put the effort into dropping the keel, the same effort would probably be enough to completely stanch the water ingress and pump some of it back out.

My intention with my next boat is to:
1. add blocks of foam in the ends of the boat where I don't want to put weight anyway,
2. to used small odd shaped pieces of foam to fill parts of locker to make them more regular shaped, I fill all the little places that are hard to get storage item into anyway. (if the bottom of a locker is not flat, I put a wedge of foam down to make it flat, for lockers under seats along the hull I use triangular pieces to fill the top outboard corner that is very pointy and hard to get items into). By adding small bits of foam to 30, 40, 60, ...whatever number of lockers, I could add 10-30 cubic feet of foam with minimal impact on usable storage volume.
3. Seal up the back of the boat under the cockpit from the cabin by fiberglassing all the bulkhead edges. There would be a couple of limberholes with valves normally left open so water could drain to bilge as it should, but in the event of a holing these would be closed.
4. Seal up as many lockers as I can and put waterproof hatches for access. See photo or go to this link: Bomar Access Hatches

Here is a link to someone that went down this route: Atom Voyages | In Search of the Unsinkable Boat by James Baldwin

[boatman61]

What if one were to epoxy the crash box with slow cure epoxy then spray/pour on the foam while its curing... would it bond into the epoxy...
Our am I inviting chemical combustion here...

[n07900]

just a little update here on unsinkability, i finally got around to fitting foam flotation after a freind demolished her extension and there was about 1.5 cubic meters of polystyrene going to the tip. so that gave me the prod to getting it done, also my boat went aground in a tight channel sitting at 45 degrees backwards when the water left, leaving the back of boat below the water that was gonna come back in in 8 hrs. i filled all back cockpits with an inflated dinghy bouys and all my empty water bottles. both cockpit lockers were filled and tied them down. the boat floated but took a lot of water in the cockpit lockers. between my cockpit lockers and living quarters there is a 5mm hole for windgen wire to come forward, water came in that and entered main boat. i beleive that without my quick flotation placed in cockpit lockers, boat would have swamped from the rear, so free foam and that experience made me think its an absolute must to fit full boat flotation. so i have now put 1.3 cubic meters of foam divided equally behind a forward bulkhead occupying the front 2 berths under the fordeck and filled and sealed the cockit lockers. cost a couple of hundred pounds to do with epoxy and plywood and sundries. but i think well worth it for that surprise event, that we never want to happen. i miss the storage and space but feel it a better seamanship descion, thanks for all the above info

[nuku34]

I worked on a custom epoxy/foam cored 62ft monohull cutter here in Nelson N.Z. The owner designed it to be non-sinkable in the event of a major hole in the hull. He has a tilting/lifting fin keel and dagger boards. The tilting keel means less lead needed at the bottom of the keel. The hull core is very thick plus large areas in the bilge are foam filled and it has water tight bulkheads in bow and stern. Its been building in his backyard for 35 years and still not done. He's a doctor and has a diabetic son who would die in a liferaft without daily insulin shots, so that was the rationale.

[Bowdrie]

Back in ~'87 I inspected and tried to buy a 40ft hull/deck that was designed and built by Eva Hollmann, (yes, she laid-up the hull herself,) who also designed the FD12.
The hull, (IIRC,) was ~4>5in. thick, alternating glass laminates with layers of foam.
The design specs indicated that if the interior was open to the sea the boat would still float with enough freeboard to allow the crew to still have a reasonable "raft" with an operable rig.
Oh, it was quiet inside.