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Old 15-11-2016, 08:59   #1
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Why do monohulls sink in hurricanes?

So I was searching through these forums when I read something to the effect that it was impossible to design a monohull sailboat that could survive the most intense of hurricanes in open seas without sinking. But what I didn't understand is why. What is the actual thing that typically fails that lets the water get into monohull sailboats under extreme hurricane conditions like 12+ (Beaufort scale)? Lets assume that the sailboat is brand new, the sailor goes below to ride out the storm, and locks up the companionway and hatches properly. For example, is it that the waves are so strong that they breakthrough the companionway or is it that the portlights get smashed through by the waves or is it that the wave break through the hull itself or even something else like having the keel broken off?
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Old 15-11-2016, 09:15   #2
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Re: Why do monohulls sink in hurricanes?

I susgest you a good read , heavy weather sailing by Adlard Coles,, old school literature...one of my favorites...
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Old 15-11-2016, 09:27   #3
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Re: Why do monohulls sink in hurricanes?

I think you should step back and consider that many ships have been sunk in a hurricane much less sailboats. If you sail within the proper seasons it's highly unlikely you'd be put to the test. There are different devises that you can deploy that will really improve your odds and certainly sailboats have endured winds and seas of hurricane strength and lived to tell the tale but avoiding is the best strategy.
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Old 15-11-2016, 10:00   #4
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Re: Why do monohulls sink in hurricanes?

Mother nature finds the weakness.

If you have never been in a typhoon or hurricane, it's hard to have a sense of how much sustained raw power they have.

Barepole and rigging alone can be ripped from the hull. A boat may get smashed by breaking waves or be sent down a wave so quickly reinforcement bulkheads start cracking.

For perspective? Steel warships with bulkheads and design for battle damage from explosive shells have been seriously damaged by storms. Destroyers have sunk.
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Old 15-11-2016, 10:12   #5
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Re: Why do monohulls sink in hurricanes?

Quote:
Originally Posted by chhe View Post
...I read something to the effect that it was impossible to design a monohull sailboat that could survive the most intense of hurricanes in open seas without sinking.
Don't know where you read it, or who said it, but they are wrong. It is most certainly possible to design a monohull that cannot sink. In fact, it has been done.

(It might not sail very well, and it might not be all that comfortable to live on, but it most certainly can be done.)
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Old 15-11-2016, 10:28   #6
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Re: Why do monohulls sink in hurricanes?

If you read some of the books from the 1979 Fastnet Yacht race and "left for Dead" in particular the author describes a carving knife flying across the cabin and embedding itself in the bulkhead. A large lead acid battery came loose and moved from the stern to the forepeak during another knock down. Whilst it is possible to build something to survive (nuclear submarine) you also have to protect the crew inside or there is no point. Then there is the cost to produce something very few people will require because they just aren't going to ever face those conditions, so what is the point of all that extra cost and would it be nice to live on board.

Boats are built to meet customers needs.

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Old 15-11-2016, 11:03   #7
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Re: Why do monohulls sink in hurricanes?

Got nothing to do with number of hulls either, in fact I'd bet the average mono will resist more force before being torn apart than the average multi.
Just because it is a whole lot easier to design a very robust monolithic structure than it is to design multiples and tie them together, not because one is superior or any such nonsense.
But it would be interesting to know the cause of sinkings, I have a theory that some at least sink because of the Lazarette. I got to looking at mine the other day and thought how much water it would hold and in the event of a roll over unless the lid was very securely fastened it could come open and allow hundreds of gallons of water into the hull, all of the sudden like. I decided to replace the one easily broken latch with a couple of robust ones
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Old 15-11-2016, 11:51   #8
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Re: Why do monohulls sink in hurricanes?

The Doubloon, a 39 foot racing sloop, survived two 360 degree rolls in 1964 off Charleston SC. Those destroyers capsized from too much top hamper (added antiaircraft guns), being light on fuel (ballast), and taking in water through the engine vents that shorted out the electric pumps. In theory, if you can seal the cabin, keep the ballasted keel attached, and figure out a way to dispense with the standing rigging without a broken mast sticking a hole through the hull, a monohull will end up rightside up and floating at the end. Whether the design would sell, given what you would have to compromise in attractive features to achieve this, Pete7 addresses well above.

It's an issue of ultimate stability - they never lost a Flower Class Corvette to weather (unless you count a collision in fog), despite their willingness to roll on wet grass and water sloshing down the companionways. They were only 205 feet overall.
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Old 15-11-2016, 13:18   #9
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Re: Why do monohulls sink in hurricanes?

Welcome aboard, cche,

As to boats being sunk, I believe ultimately it is due to water ingress. Boats flex a lot when they're stressed, and certainly some boats have had ports fail. Cockpit lockers leaking on sailboats where the water can begin to fill the hull can be another, knew one boat, a Cheoy Lee Offshore 40, that took in water through the pedestal base during a storm. So I'm thinking Destiny Ascend above has it right, wherever the weak links are, that is what will fail. Boats that rely on glue- bonded in inner liners to maintain structural integrity are particularly imho; and if you're upside down for a while, tanks can come loose and break through the joinery, water streaming in from the Dorades. Pumps get overwhelmed, or clogged. Would be horrible, terrifying. Much the best avoided.

And, I'll second Adlard Coles' "Heavy Weather Sailing" as a reference, as well. It's always a good idea to try and see how someone elses ideas can be picked apart, or if they stay sound to you after trying to pick them apart. Those latter are the ones to store for future reference.

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Old 15-11-2016, 14:55   #10
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Re: Why do monohulls sink in hurricanes?

The 167 ft Nadine sank off Sardinia in 1996 because a large wave broke over her bow and smashed a simple lapstrake wooden hatch to the bow crew's quarters. Ann makes a very good point - if you can't keep the water out, including quite small openings, nothing else matters. You don't even need a gale - a broken seacock in an inaccessible place will do quite nicely.
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Old 15-11-2016, 16:02   #11
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Re: Why do monohulls sink in hurricanes?

A tennis ball will survive, probably. Build in a sturdy hatch & there you go Seriously though (or somewhat) watch The Perfect Storm. But also, consider this. If a boat doesn’t survive a storm, who’s left to report what sank them? Plus, it's more common than not for radios to be knocked out in such storms. Besides who would you talk to? Not many boats are out there in such conditions.

Also, in addition to the books already mentioned, do some reading of the stories in the Drogue Device Data Base. It's a work in which tales of vessels in heavy weather, which deploy drogues or sea anchors in order to survive big storms, are studied. The stories don't involve hurricane per say, but you'll get some sense of what boats, & also people (usually the weak links) can handle. Victor Shane's Drag Device Data Base | Using Parachutes, Sea Anchors and Drogues to Cope with Heavy Weather – Over 130 Documented Case Histories
Oh, & do a few online searches using the “phrase drogue device database” too.

In addition to this, download (free) & read Surviving the Storm by Steve & Linda Dashew. They’re world renowned sailors who’ve written many books on most aspects of sailing. And in this one there are also after action reports of vessels caught in major storms. SetSail FPB » Free Books



PS: The best way to see waves that get generated by such weather, & live to tell of it, would be to fly to say Hawaii in the winter, & visit the North Shore, where pro surfers go for the huge ones. And to experience such winds, go to a ship's flight deck, or an aircraft flight line, & be tethered down when they're launching aircraft. As then you might get to experience 100kts, & the tethers are because you can't walk in winds much over 60kts. Even then it's supremely difficult.

Here's how you calculate wind force http://www.harken.com/content.aspx?id=9096

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Old 15-11-2016, 17:31   #12
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Re: Why do monohulls sink in hurricanes?

My post is not specific to a hurricane, but is more general to saiboats in a severe storm or heavy weather sailing. Certainly the extreme conditions of a hurricane or typhoon would be most dangerous, but boats do sink because of storms that do not reach hurricane wind strength, but due to wind and wave.

Short Answer: Water floods the boat and she founders and sinks.

Causes:

1. Breaking wave crashes on the deck, causing the boat's hatches and portlights to be broken or blown in, allowing water to enter quickly with each wave. Electrics fail, pumps no longer work, subsequent breaking waves flood the boat and she sinks.

NOTE: This wave (and ones in the following cases) does not have to be a "rogue wave," it merely needs to be large enough to break onto the deck or cabin of the boat.

2. The boat is struck by a following wave that "poops" the boat and floods the cockpit, and smashes in the companionway hatch, flooding the boat. She sinks.

3. The boat drops off a steep wave, smashing the cabin or the cabin top off the boat, flooding the boat. She sinks.

4. The boat has a sea anchor out off the bow, with bow to oncoming waves, yet slides backwards down a large wave and snaps off the rudder, possibly taking a large chunk of the stern with it or ripping a hole where the rudder post enters the boat. She sinks.

5. Strong winds cause a dismasting. The mast is still attached to the boat by shrouds. The mast impales the hull or stoves it in, causing fast flooding. She sinks.

6. A wave hits the boat's hull and blows off the hoses attached to thru hulls, due to water pressure, allowing water to pour in, flooding the boat. She sinks.

Those are just some of the causes that have been reported, and that I recall.

Also, most companionway hatches (typically thin hatch boards of thin wood, plexiglass or acrylic) and portlights or deadlights (windows) on typical coastal cruisers are NOT strong enough to stop a breaking wave from smashing them, some have a hard time just keeping rain out. Most are made of light or thin material without much support to hold them in and are a weak point in any boat. If the deadlights are large (big windows) the risk increases.
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Old 15-11-2016, 17:43   #13
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Re: Why do monohulls sink in hurricanes?

Some companionway hatches are heavy teak boards though, and some port lights are rather small, made from heavy investment cast 316 SS with the window itself from laminated safety glass exactly like a car windshield.
Some are all plastic, "glass" included.
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Old 15-11-2016, 18:00   #14
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Re: Why do monohulls sink in hurricanes?

Usually, I think there is a cascading chain of events. maybe a rudder breaks, water starts coming in through the rudder bearing. Rudderless, she can no longer be steered to a safer course.

Once you lose electricity, you're in a world of hurt.

From flexing, bulkheads sometimes let go.

Lots of stuff on a boat to break, actually. But the closest cause of death is water.

You can get in a situation where there are cross seas that give you extremely peaky waves, and get rolled down, mast in the water, windvane rudder breaks, and that was only in about 45 kn. Just saying. That particular wave, which bashed in the hard dodger window, was the least proximate cause of our dismasting in our first Insatiable.
It happened farther along in the journey, as we were seeking to return to Australia, when, hove to to rest, the mast fell down. Don't know whether the sheet plucked out the cotter pin, or it broke, but mast was over the side, and the clevis pin rolling back and forth between the chain plate and the toe rail, and no broken bits on deck.

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Old 15-11-2016, 18:30   #15
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Re: Why do monohulls sink in hurricanes?

Quote:
Originally Posted by neilpride View Post
I susgest you a good read , heavy weather sailing by Adlard Coles,, old school literature...one of my favorites...
Another good related read "Tallships Down" by Daniel Parrot. Analysis of tall ship loses in modern times (hey, they are all monohulls).

https://www.amazon.com/Tall-Ships-Do.../dp/007143545X
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