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Old 25-11-2011, 12:42   #1
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Unsinkable Monohull - Why Not ?

I am constantly reminded on this forum that my mono is going to sink one day if I am not careful.

Has anyone tried to make their mono unsinkable with inflatable bags? I'm sure if you put one in the forecabin and one in the aft cabin that would give enough boyancy to keep us floating the right way up and quite comfortable in the saloon.
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Old 25-11-2011, 12:49   #2
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Re: Unsinkable monohull - why not?

I think Etap(?) made some unsinkable boats. Basically they added a lot of foam to the hull thickness all over. It does impact on the interior space though.

A friend of mine designed his own boat and did a similar thing, filled a lot of his storage spaces with foam. It worked, he holed his boat in a big way once but stayed afloat long enough to get a patch on the hull. he also had a very deep bulb keel which was retractible, so he could use less ballast.
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Old 25-11-2011, 12:58   #3
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Re: Unsinkable Monohull - Why Not ?

titanic????? oops-that was non water tight watertight bulkheads...oops....i read about yacht saver and their puff bag system in 1990. dont know what ever happened with that idea or company....
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Old 25-11-2011, 12:59   #4
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Re: Unsinkable monohull - why not?

Quote:
Originally Posted by Eleebana View Post
I am constantly reminded on this forum that my mono is going to sink one day if I am not careful.

Has anyone tried to make their mono unsinkable with inflatable bags? I'm sure if you put one in the forecabin and one in the aft cabin that would give enough boyancy to keep us floating the right way up and quite comfortable in the saloon.
From what I've read over the years is that bags don't work for a number of reasons. One being that they get punctured from objects inside the boat or they end up damaging the boat by trying to lift the boat by it's cabin top resulting in hull joint damage, and so on.

I think armor plate below the waterline is your best bet if worried about being holed. The Star of India had iron plate on her bottom.

I've seen some foam filled inflatables out there.
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Old 25-11-2011, 13:02   #5
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Constant vigilance is a good start sometimes called serenity. Otherwise get a LPG tanker hard to sink if kept in one piece.
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Old 25-11-2011, 13:24   #6
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Re: Unsinkable Monohull - Why Not ?

The Sadler 34 was designed to be "unsinkable". I recall reading that when it was first introduced at the London Boat Show in 1983, the builder opened the seacocks to to flood the boat to demonstrate this.

See:
Sadler 34 Yacht
Sadler 34 archive data - Yachtsnet Ltd. online UK yacht brokers - yacht brokerage and boat sales
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Old 25-11-2011, 13:26   #7
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Re: Unsinkable Monohull - Why Not ?

Also, Tania Aebi's Contessa 26 was made unsinkable by the builder (also using foam.)
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Old 25-11-2011, 13:30   #8
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Re: Unsinkable Monohull - Why Not ?

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The Sadler 34 was designed to be "unsinkable". I recall reading that when it was first introduced at the London Boat Show in 1983, the builder opened the seacocks to to flood the boat to demonstrate this.

See:
Sadler 34 Yacht
Sadler 34 archive data - Yachtsnet Ltd. online UK yacht brokers - yacht brokerage and boat sales
The Sadler is probably the most well known unsinkable boat. It has a layer of foam in the hull. Unfortunately this makes the interior somewhat smaller then if it wasn't unsinkable and I guess most people prefer space(which is a benefit all the time) to being unsinkable (which is a benefit on very rare occasions) so it hasn't taken on.
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Old 25-11-2011, 13:31   #9
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Re: Unsinkable Monohull - Why Not ?

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Originally Posted by Eleebana View Post
Has anyone tried to make their mono unsinkable with inflatable bags?
And I do recall someone marketing inflatable bag system a while back just for this purpose. I don't think that ever caught on, though, due to practical issues.
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Old 25-11-2011, 13:42   #10
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pirate Re: Unsinkable Monohull - Why Not ?

Got lottsa useless storage space under quarter berths and fore peak so planning on filling it with pourable foam...
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Old 25-11-2011, 13:59   #11
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Re: Unsinkable Monohull - Why Not ?

The FD 12 is advertised as unsinkable. They don't say how high it floats flooded though.

FD-12
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The company that made inflatable bags was called Yachtsaver. One of the problems encountered was that the deck on one boat they tested pulled out from the loads of supporting the boat.

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Old 25-11-2011, 14:08   #12
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Re: Unsinkable Monohull - Why Not ?

A combo of bags and foam may work...the touble is where to put the foam that it doesn't take up room or prevent access. Salvage bags are incredibly tough and would not puncture unless you really put them is a bad spot...then the question is foam and bags to keep the boat mostly afloat and usable...could be done but if you redo all the manufacturers ill placed seacocks into a small watertight area and have reasonable separation of compartments...progressive flodding should never sink you..only a capsize with all openings open or a horrific collision breaching several compartments.

Production boatbuilders are pretty clueless as to making a more seaworthy vessel....pricepoints keep it that way....but you can alter that equation if you want for not a lot of money.
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Old 25-11-2011, 14:34   #13
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Re: Unsinkable Monohull - Why Not ?

I wonder how much foam is required to keep a 36,500 lb FD12 afloat? You would lose a lot of storage space.

I think the better solution is a water tight bulkhead forward and another aft. As an example the Dashew designed Sundeers had this, and only 2 through hulls, none in the center section between the bulkheads. Paine's Apogee 50 has a crash bulkhead forward and a watertight door to that section.
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Old 25-11-2011, 14:39   #14
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Re: Unsinkable Monohull - Why Not ?

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Originally Posted by mitiempo View Post
I wonder how much foam is required to keep a 36,500 lb FD12 afloat? You would lose a lot of storage space.

I think the better solution is a water tight bulkhead forward and another aft. As an example the Dashew designed Sundeers had this, and only 2 through hulls, none in the center section between the bulkheads. Paine's Apogee 50 has a crash bulkhead forward and a watertight door to that section.
mostly depends on ballast as a lot of the rest of the boat is buoyant/close tobuoyant and doesn't need as much foam as you thimk.....
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Old 25-11-2011, 14:44   #15
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Maybe another thread. Imaging an event where I'm taking on water. Can't stop the waters or i cant keep up with the pumping. How many boats were ditched under these circumstance? Many float on I think. Certainly it's happened but it is in a cruising context very rare. Read moxie they were floating in a prior boat but it was not sustainable. Read survive the savage sea sustainable but no real boat. Old era stuff. Those compartments you are filling with foam are reserved for fuel filters tooth paste vinegar water filters. All sealed so maybe they will float. I am nit putting any effort into be flotation positive. Going with good tabbing sealed hatches, ventilators, intakes, tethers. More primary means of being safe. I could keep on spending infinite hours keeping my boat safe or I could start on a longer journey trying to figure how to make it be viable after it's been compromised.
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