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Unsinkable

7K views 44 replies 28 participants last post by  whroeder 
#1 ·
To my understanding, mono-hulls sink if they flip. Are any mono-hulls made unsinkable? I never had sailboat and have to learn. During the "learning process"
it is good chance that I could flip the boat and I do not know if I can swim few miles to shore.
 
#2 · (Edited)
Most sailing dinghies have flotation compartments and won't sink if flipped. Smaller ones can be re-righted in the water.

Ballasted keel boats generally are not 'unsinkable', although the builders Elan or Etap does produce a line that makes the claim. A well designed keel boat should not "flip" except in extremely severe weather.
 
#3 ·
If a monohull keel boat is upside down, it probably means you've lost the keel in which case you are screwed anyway.

If you are sailing a small dinghy, and you flip it you have to right the boat but this isn't usually too impossible. I've never seen one sink unless it was holed. I capsized my granddads Sunfish loads of time as a small girl and never had to swim to shore. Struggle to right the boat, yes but abandon the boat? Never.

Wear a PFD.
 
#13 ·
Why mono sink and multi float? It is because bouyoncy of two hulls?

Traditional sailboats are monohulls, but multi-hull catamarans and trimarans
are gaining popularity. Monohull boats generally rely on ballast for stability, and usually are displacement hulls. This stabilizing ballast can, in boats designed for racing, be as much as 50% of the weight of the boat, but is generally around 30%. It creates two problems; one, it gives the monohull tremendous inertia, making it less maneuverable and reducing its acceleration. Secondly, unless it has been built with buoyant foam or air tanks, if a monohull fills with water, it will sink.

(Since multihulls don't have ballast they will usually not sink as quickly as a mono hull.)


Sailboat - Wikipedia, the free encyclopedia
 
#7 ·
You are not going to capsize a 30 foot keel boat under normal conditions. You can have the sails touch the water and the keel will cause it to right itself.

The cockpit is the open area in which you sit. You can not make an open air area water tight unless you use your special magical powers. If you are using special magical powers, every boat is unsinkable. ;)
 
#9 ·
Everyone has to start somewhere. No shame in not knowing something, which gives me great comfort as I don't know a whole heck of a lot more than I do. :)

I'm guessing you've not been sailing much. My husband paid for University by coming to the States every summer and teaching dinghy sailing at a camp in upstate NY. He started every sailor off the same way. He would sail the boat out into the middle of the lake, look the student in they eye and say "lets get this over with". Then he would intentionally capsize the boat and get the student to right it and climb on board. First lesson over.

He does the same thing with new sailors o our boat, only since its a keel boat you can't capsize it. "Lets get this over with" followed by catching the wind to heel as far over as possible. After the shrieks subside, he tells them "See? We are not going to Capsize". Then everything else is fun.
 
#10 ·
I once calculated to place enough reserve buoyancy in my Catalina 27 that would allow her to stay afloat if full of water that I would have to fill every storage space with floatation foam or airbags. Essentially I would turn her 27 foot dinghy. Obviously not worth it.

Dinghys are not necessarily unsinkable. They need to be designed that way. All of the dinghies I sail are unsinkable and fun to capsize. I recommend trying it once even if you sail keelboats to feel how these boats balance and keep them on the edge of control.

I believe some racing keelboats are more or less unsinkable but they are also light displacement hulls lacking lots of heavy items typically found on typical cruisers. Like bunks and cabins. :) But these boats are designed with reserve buoyancy built in. Such examples are really more big racing dinghies but do include boats like the Yngling. Not exactly what you're after.

The only boat I know of that would meet your requirements in a keelboat would be the Rhodes 22.

Matt
 
#15 ·
Sadler and Etap are two monohull manufacturers that manke "unsinkable" monohulls. The reason most monohulls are not UNSINKABLE is the fact that the materials they are made of are effectively denser than water overall—primarily due to having a large metal mass for the keel.

While I'm not familiar with the Sadler method of providing buoyancy, the Etaps do this by effectively building a boat with nested hulls and a layer of foam between the two hulls. The volume of foam is sufficient to float the boat—but it does result in a loss in interior usable volume and stowage.

Most multihulls, not having the heavy metal keel and often being made of cored fiberglass laminates, will tend to be less dense than water overall, and will float, even if holed. Many multihulls also have multiple hulls which are watertight to each other and may also have multiple watertight compartments within each.

A modern trimaran has two amas which are independent of the main hull and each usually provides at least 150% of the displacement of the boat in buoyancy. On my boat, the amas are separated into three watertight compartments, so even if holed, they are likely to have some buoyancy beyond the materials they're made of. Likewise, the main hull on my boat has three buoyancy compartments—one forward at the front of the bow and two aft, under the cockpit. If the boat is involved in a frontal collision, the water intrusion will likely be limited to the forward buoyancy compartment and not affect the rest of the boat's water tight integrity.
 
#17 · (Edited)
I think Dupek is putting us on.

I'm only a beginner, but I know that a boat will float. Now if it has flipped on to its side and water is going in the cockpit and cabin, the weight of the water would definitely bring it down a bit, but it would take a lot of water to sink it, and I don't know if there would be that much water in it if the boat was on its side. Now, hypothetically, if you take a dry boat and place it in the water with the keel directly up in the air, would it float? I say yes. The reason why a boat floats has nothing to do with its shape; it only has to do with density. Please correct me if I am wrong. The density of the boat, including what is inside of it -- most importantly the space inside of it -- needs to be a lot less than the density of the water. That's why it floats. By flipping it fully around, the water would come out along with you and some of the luggage, and so I think it should actually float better than upright.
 
#18 ·
Taking a different tack from the responses you have had: If a boat is properly closed up - companionway(hatch) boards in place and closed, portholes closed etc. - you can roll or flip a monohull and it generally won't sink - unless the hull is pierced in some way, or a porthole/window fails. In offshore (also called blue-water) boats all the possible openings are made especially strong to reduce the risk of such a failure. But it takes a lot to roll a 30' monohull.

Wind alone won't flip a 30' keelboat - unlike a dingy, the keel helps keep it upright - and the more you heel (lean over), the more wind spills off the sails, and so the pressure lessens.

And if it does flip, you won't have to right it - the keel (that big heavy weight under the boat) will roll it up the right way all by itself.

When will a 30' boat flip? Either if the keel falls off (very rare, but does happen), or if it is hit broadside by a wave greater than approximately half your boatlength in height - so in a 30' keelboat, you would need 15' high waves breaking on you sideways to risk a roll.

Many blue-water keel boats have been rolled by massive waves, righted themselves, and kept going. A friend of mine had a 54 foot boat delivered from Australia to the US - it pitch-poled (bow went in, flipped over forwards - 54 feet! - just imagine that!). Then righted itself - fortunately (somehow) no injuries - and they kept sailing.

However, regardless of how well you close up the boat - however unsinkable it is - there is always the risk of sinking. Pipes burst, windows smash, icebergs tear holes half the length of your boat. Sometimes boats burn down and even blow up - in which case any flotation foam won't help either!

However, a well-maintained modern monohull keelboat is tough to sink. Even if it flips over, it should roll back again all by itself. It will lean over a lot, though....
 
#20 ·
Thanks Paul323. The big, sudden waves and unexpected weather change makes me worry about sinking the boat. That means, if the cabin is watertight, the amount of water on deck will not sink the boat. I like the "space ship" look of trimarans.
 
#23 ·
I would not want to be on a 54' boat that truly pitchpoled. There's almost no way the mast would've survived or the people without injuries. I've been on boats (skiffs and small multihulls) and the forces in a pitch pole are impressive. Pitching a 54' boat would take a large breaking wave and it would be truly horrible. Broaching however is very possible and can occur after you stuff a wave hard, been there, done that, and while slow, a well found mono should be fine.


As to worrying about whether a boat will sink - first off get some sailing lessons in a dinghy. Don't go straight to the keel boat class - get in a dinghy and spend a season sailing - you'll know a whole bunch more and have many different questions.
 
#24 ·
I would not want to be on a 54' boat that truly pitchpoled. There's almost no way the mast would've survived or the people without injuries. I've been on boats (skiffs and small multihulls) and the forces in a pitch pole are impressive. Pitching a 54' boat would take a large breaking wave and it would be truly horrible. Broaching however is very possible and can occur after you stuff a wave hard, been there, done that, and while slow, a well found mono should be fine.

As to worrying about whether a boat will sink - first off get some sailing lessons in a dinghy. Don't go straight to the keel boat class - get in a dinghy and spend a season sailing - you'll know a whole bunch more and have many different questions.
It's been suggested in other threads. :)
 
#25 ·
. My husband paid for University by coming to the States every summer and teaching dinghy sailing at a camp in upstate NY.

I tought sailing at a Boy Scout camp in up-state NY . I should say I knew nothing about sailing when I started , but was the only one that volunteered to teach the classes. I would like to think out of the 40+ scouts that a few are out sailing still.

I think my C-22 is an Etek boat and is why the 1st mate gave sailing a try.

You don't want to be in conditions that will sink a 30', and don't be fooled multi hulls have sank in the same conditions.:puke
 
#26 ·
It still seems odd to worry about sinking before having a grasp of the fundamentals of how to sail. Statistically, dupek, you're very very very unlikely to sink any boat if you follow basic safety practices, understand how to read weather files and reports, know how to navigate, keep up with your boat maintenance, know how to sail, have good basic seamanship skills/practices, etc.... As we tap on our key boards, there are thousands of boats out sailing in the oceans and lakes of the world. Interestingly enough, reading about a sinking isn't something that happens much, even on sailing web forums. Personally, I think a monohull boat, while slower, is safer. If you flip a catamaran at sea, it might not sink, but you're really going to be in a lot of trouble. There are many ways to die on a boat even if it doesn't sink. In our area, the water is very cold. Hypothermia is what we're generally most worried about. Falling off the boat is a much more real danger than sinking. And like Mario says, conditions that pose a real threat to a mono hull can certainly flip or sink a cat as well. Again, IMHO, it seems you'd be much better off taking some dingy or beach cat sailing lessons than worrying about sinking either. If you can't swim, it's always a good time to learn.
 
#27 ·
Are "all" production catamarans "unsinkable"? I have a Lagoon 35ccc, it doesn't look like there are any "watertight compartments" (at least that I can see). Can I assume with the hulls filled with water my boat has positive buoyancy. Is there a way to find out for sure (without holing her)?
 
#29 ·
The Lagoons are cored construction for the hull, cabintop and bridgedeck. As such, it is probably positively buoyant overall, since it has no keel.
 
#28 ·
I had the opportunity to peek inside of an Etapp that I raced against about a month ago. the interior wasn't drastically smaller and it was a pretty nice boat. (Being well maintained helped)

I was on a C&C 35 MkIII and he was able to stay within hailing distance, so they seem to sail well. (or we're lousy racers on the C&C, take your pick)

I don't know if the OP is even paying attention anymore, but knockdowns happen. It's not a big deal. Keep the cabin top shut, and the washboards in. Dump the traveler and the main sheet if you're getting pushed over.
 
#34 ·
You might consider them unsafe, but I don't. I don't require a big keel to consider a boat seaworthy. :D
 
#35 ·
Don't worry about capsizing a 30 footer. Except in extremely rare circumstances, the boat will come back upright in the very unlikely case that you get knocked down.

The reason cruising cats don't sink is that they have no need for a lead keel. They have their width to keep them upright. They are muck lighter for their size, and a few watertight compartments make them float.
 
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