Sinking Avoidance,

[Mr B.]

After learning the hard way about sinking a Boat,

I was looking at ways to stay afloat after being holed in any way,

I was looking at high speed, high volume pumps,

If you knock out a thru hull, Thats a 3 inch hole in your boat, Thats a huge volume of water entering your boat, Very quickly,

You dont have very long before every thing down low is submerged, Electrics start shorting out, So, No Power, No pumps, Etc,

So I have now looked at just keeping the boat afloat till I can repair the hole, or sail it to some where I can beach it and repair it,

To do this, I have come up with the Idea of inflatable bags, Like the ones they use to jack up cars in sand,

My boat weighs 5 ton Approx, I need 5 cubic metres of Displacement with my inflatable bags,

One Cubic metre bag in each of the four corners of my hulls will keep me afloat,
They inflate very quickly, take up no space whatsoever when packed flat,

I can have them layed out under the beds, Then its just a matter of plugging them into the air pump and inflating them,

No. I dont intend on getting sunk again, But I do like to be prepared for what ever is thrown my way, And for getting my butt and my boat out of trouble,
Single handing is being resourcefull enough to cover all eventuallitys,

One cubic metre displaces one ton of sea water, So it can work on all size boats,
A nice bit of added security,

[HappyEnding]

are you just planning on tieing it to a cleat to keep your submerged boat just buyont enough to float around? Otherwise your in the water securing them low hose going to one you have to disconnect to fill another? Or maybe just foam fill some compartments on yur boat?

[Talbot]

You are better off having separated zones on the boat, so that a hole in the hull only fills up a part of the boat. This reduces the flotation requirement - and may even remove it unless more than one zone is holed. The biggest problem with the standard cat design of engines under a rear bunk, is that the engine room is part of the main hull zone, and this is an area that is more likely to flood than elsewhere. You may well be able to seal the dwarf bulkhead at the front of the engineroom, but a close look on most designs reveals that there are lots of holes through that bulkhead. It would be an error to seal most of these as it would make replacement of pipes or electric cables very difficult. I have got neoprene stuffing into these pipes, not with any expectation that it will seal the engine room - but with the hope that this will slow down the ingress of water sufficient to allow my pumps to work.

[Mr B.]

The bags are for inside the boat, Emergencys only, They dont need tying off,

My boat is just one big hole, it does not have sealed sections that are worth worrying about,

I dont know if it would sink by itself or would float, The air bags take that worry away,

I cant sink with the air bags inflated, , so I have time to think on what I can do, A lot of variables here,

The crucial part is staying on the surface, Half sunk is not an issue,

You can work on your boat, and or get it to shore to repair the damage,

4 or 5 air bags take up the same room as 4 Auto inflatable, PDF 1's. Deflated,
The pump is about the same size as a 12 volt Bilge pump,

I pumped out my water tanks, When I sank, But they weren't bolted down and floated up with the water ingress, But would have kept me on the surface if I had not been sitting on the beach at the time,

Water tanks X 2 = one cubic metre, = one ton of displacement,
Black tank, empty X 1 - aprox one cubic metre, = One ton of displacement,

So I only need two cubic metres extra to keep the boat afloat, But four airbags, gives me a good extra security and will keep the boat well and truly on the surface,

[Zero Gravity]

Water tanks X 2 = one cubic metre, = one ton of displacement,
Black tank, empty X 1 - aprox one cubic metre, = One ton of displacement,

1,000 litres of fresh water and 1,000 litre holding tank in a Gemini? I suggest a remeasure and recalculation.

As for the inflatable idea, I think it may have merit with a smaller target in mind. Do you think the Gemini would sink or just be fully awash? I thought it had enough flotation to stay at the surface.

Even then, the hulls would need to be fully awash for the bags to be effective, so you wouldn't really be achieving a lot. If you think it would actually sink, then a mix of foam filled sections, small inflatables and emptied water tanks would at least ensure the boat stays on the surface, and provide a survival platform until help arrives.

[Talbot]

1,000 litres of fresh water and 1,000 litre holding tank in a Gemini? I suggest a remeasure and recalculation.
.

1000 litre holding tank - That has to be good for nearly a year of cruising.

[dmmbruce]

Following Zero Gravity's points, it would seem to be more practical to have several smaller bags, secured below the level of the bridgedeck. Some big loose ones would just come up to the ceiling and not be very helpful.

Also, you said the Gem weighs 5 ton. However, when semi-submerged, the weight to be supported would only be some proportion of the air-weight of the submerged part, plus the weight of top deck and rigging.

Mike

[Mr B.]

one metre X 500mm X 400mm X 2, Close enough to one cubic metre,

Its 60 US gallons to be precise. in two tanks.

This was only a suggestion, Nice and easy to carry, Takes up no extra room,

Will save you in a desperate situation, Like sinking,

On point you must keep in mind if your sinking, You wont have the time,

Thats if you are in contact with anyone, anyway, To look up all your favorite

Internet Hero's to help you out, as your boat sinks,

Too be honest, I dont know if a Gemini would sink or not, I am not about to find out either,

But with my air bags on board, I can go any where I like with out the worry that if I did get another hole, I wont be going to the bottom,

The air bags are 1000 litres, or one Ton, if filled with water, One cubic Metre,

Folded up, they are about 6 inches by 6 inches by about 1 inch thick,

Made of thick rubber, So cant easily be puntured against sharp points inside the boat,

My black tank is enclosed, So it was only a Guess as to its size, 18 gallons,

My small holes are already filled with the essentials I need for sailing, Parts, Food, Fuel, oils, tools,

It will probably be awash, But afloat, Thats all I am intending to do, Keep it on the surface,

Its still cheap insurance for any boat, It will work with any boat, Regardless of size.

[Mr B.]

Following Zero Gravity's points, it would seem to be more practical to have several smaller bags, secured below the level of the bridgedeck. Some big loose ones would just come up to the ceiling and not be very helpful.

Also, you said the Gem weighs 5 ton. However, when semi-submerged, the weight to be supported would only be some proportion of the air-weight of the submerged part, plus the weight of top deck and rigging.

Mike

Unless I do structural additions to the boat to hold the bags down, They will just be floating up against the ceiling,

The big ones are easier to use, You have four holes to worry about, not 20 or 30,

Like I said before, Its just one big hole, There are no partitions to fill,
But two big ones in the back bedrooms, They cant move, they are locked into the room,
Its not pretty inside when your full of water, There is food, scraps, paper, towels clothing, Bedding, oil, containers everywhere, everything is floating around,

Every thing you want or need is under water, Pumps, Etc, You have to feel for it, You need to know where everything is stored, without lights, in the dark, Howling wind, large waves, Your up to your Bum in water,
Time is running out fast,

Fibreglass floats, But you have to weigh that up against all the dead weight on board, The motor and drive leg will drag it to the bottom very fast, The mast and rigging are very heavy, Plus chain and anchor, Spares, tools,

Its only a safety factor, It will keep you on the surface while you do the repairs, or keep you afloat till you can beach the boat safely,

Or can be picked up by The rescue service if it gets to the extreme stage when your boat has sunk and your sitting in the ocean in your dinghy,

[Zero Gravity]

one metre X 500mm X 400mm X 2, Close enough to one cubic metre,

Well 20% of a cubic metre actually .... which roughly matches your stated capacity of 60 US gallons = 240 litres.

My black tank is enclosed, So it was only a Guess as to its size, 18 gallons,

18 (US) gallons is about 70 litres.

Add them together and you only have bouyancy to displace about 300kg. As for the bags, I can't imagine the material being very strong if they fold up so small. Again, I suggest smaller bags and secure them low down.

[Gringo]

Carry a half a dozen REALLY big inflatable fenders?

[Mr B.]

Damn it, I lost my post,

I have decided to get water bed Bladders, or Camping air bed mattresses,

Very heavy duty rubber, My Kingsize water bed has 2 cubic metres of water in it and weighs 2 Tons,

I can use two mattresses in each of the back bedrooms and an air bag in the Dunny and shower cubicle, and an Air bag stuffed into the cupboard which is all the right Bow,
That leaves me the whole boat clear to work in, full access to all tools and spares,

[dmmbruce]

Ok.

Just remember to tie them down, strongly, or they won't give any lift!

Mike

[Mr B.]

Would it have sunk completely if I had not had the Bow sitting on the beach,

Just hit a container out at sea, punching a hole into it, would my boat sink, I just dont know,

You dont go outside in bad weather, out at sea if you can avoid it, Do the repairs inside and wait for the weather to ease off,

My Air bag idea will make sure I dont sink,

I wonder how long I would have floated after I got holed,

[Tabs]

Fibreglass floats, ,

No, it doesn't!

[44C]

It's not a bad idea, but I'd suggest you might need a faster way to inflate them than the electric airbed pumps you can buy. Same reason you gave as for why bilge pumps won't keep you afloat. Flooded batteries= no power.

A CO2 cartridge like on PFD's or liferafts might be better.

The airbed pump might be quick enough for a damaged seacock or relatively small hole like that, but in those cases a set of tapered wooden bungs and a mallet might be a better solution.

[Gringo]

SCUBA tanks?. You could plumb it to all your airbags, with a central valve where you could reach it. Or you could automate it. wire it to a float switch with a solenoid. But with a straight SCUBA inflation system you don't have to rely on your electrical system being operative.

Inflate all your bags at once, or put a valve in for each bag. That's a good idea about heavy duty waterbeds. I've seen some with fabric reinforced rubber. You don't want something that chafes easily, or will split with age.

I was thinking of taking old RIB tubes and making them into cylindrical bags. Could cut end pieces with built in grommets to secure them to the deck or hull. You want them lifting, not pushing up against the overhead. Industrial strength, manually controlled, marine air bag system. Stops a slow motion collision between your hull and the sea floor.

Whaddaya think? SCUBA bottles are a good thing to have on board, anyhow, and you can get them filled at the kinds of places a sailboat naturally goes to. Any town with marinas will likely have a dive shop. You don't wanna be messing with four individual bags while you're trying to control the boat and just knocked a hole in it, and the poop is hitting the fan.

Each standard SCUBA tank holds 80 cu ft. of air. 2.26 cubic meters.
instantly available.

[Captain Bill]

Damn it, I lost my post,

I have decided to get water bed Bladders, or Camping air bed mattresses,

Very heavy duty rubber, My Kingsize water bed has 2 cubic metres of water in it and weighs 2 Tons,

That is one heck of a water bed. My king size waterbed only holds 31.5 cubic feet of water and weighs slightly under 1 US ton whch is 200 pounds less than a metric tonne.

[Mr B.]

Aluminium air tanks would be a great idea, They would be easy to stow away, and quick to inflate any bags with air, Have a long enough hose on it to reach the bags, and just turn on the tap, So simple and easy, Very quick in that moment of haste,
Takes the worry of sinking out of the equasion,
So leaving you with total control and time to fix the leak,

Capt Bill, Sorry, It was only a guess from a water tank size I had here, I went and measured my bed, Same size as yours, 6 X 7 by 8 inches, And a ton in weight,

Kingsize wont fit in the boat, Hahahaha

Tying the mattress down will be a problem, Wait and see on that one,

I have the round tapered plugs, But you have to find the hole first, If its a fair sized hole you can see it,
But if it is small and below the floor, its hard to find the hole Submerged under water,
The way my floor is, I could only stuff a rag in a hole in there, No access,

I am moving my thru hulls to a safer place as well,
They were in the middle of my hulls, right where it sits on the beach,

Fibreglass does not float, Well, there is bugger all else in my boat to keep it afloat,
Makes me glad now that I was sitting half on the beach,

It Definately would have gone under, now that I think about it, There are no pockets of air to get trapped, No foam any where, other than foam mattresses, No idea on how they would float,

[therapy]

1,000 litres of fresh water and 1,000 litre holding tank in a Gemini? I suggest a remeasure and recalculation.

As for the inflatable idea, I think it may have merit with a smaller target in mind. Do you think the Gemini would sink or just be fully awash? I thought it had enough flotation to stay at the surface.

Even then, the hulls would need to be fully awash for the bags to be effective, so you wouldn't really be achieving a lot. If you think it would actually sink, then a mix of foam filled sections, small inflatables and emptied water tanks would at least ensure the boat stays on the surface, and provide a survival platform until help arrives.

Here is how a Gem floats once filled with water.