Full keel vs fin keel for offshore?

[kmacdonald]

The stability curves are for boats that don't have tons of water in them. A lot of boats, if not all, sink if inverted. Most sailboats are "knocked down" not inverted. The stories of 360's in sailboats are considered exaggerations of knockdowns by most rational people. I'm not saying it's impossible, just highly unlikely.

[robert sailor]

Originally Posted by newhaul

Question how many fin keel cruising boats are self righting in the event of a turtle?

If you compare a modern boat with a wide beam running to the stern and 30% ballast ratio... now if this boat is rolled it may very well stay inverted for quite some time. The very thing that added to the stability(wide beam) is now working against it making it very stable inverted. There have been examples of this happening in the past.. You may recall that the canting keel was brought in to allow the offshore racing boats to be self righting should it be rolled because with their wide beam they were also very stable inverted.
Now compare that to a Contessa 32 with a stability range of around 155 degrees and a high ballest to displacement ratio this little bugger is almost impossible to keep inverted as even the slightest movement would have it back on its feet.
So while I can't say it's self righting after it's gone turtle my guess would be with such a high range of stability that if rolled it would probably use it's momentum to continue rolling and come up the other side, just a guess.

[robert sailor]

Originally Posted by kmacdonald

The stability curves are for boats that don't have tons of water in them. A lot of boats, if not all, sink if inverted. Most sailboats are "knocked down" not inverted. The stories of 360's in sailboats are considered exaggerations of knockdowns by most rational people. I'm not saying it's impossible, just highly unlikely.

During the Queens Birthday Storm off of New Zealand one 44 foot cruising sailboat reportedly pitch poled and rolled 360 degrees. Now you might consider that an exaggeration but then you'd have to explain the aerial pictures taken from the NZ Air force showing the mast completely wrapped around the boat.

[newhaul]

Originally Posted by Don C L

I should have added though that narrow CCA boats typically do have a very small (or even none) "region of negative stability" in their curves. (Wish I could find the one for the Columbia 29; its curve does not drop down into negative stability.)

my defender has a cca rating of 19.9 likely due to the extra half ton of lead in the keel.
Full keel with cutaway forefoot .

[newhaul]

I have never experienced a knockdown ( I assume lots of lead lots of wetted surface ) they have just gone to about 30° and dumped the wind.

[kmacdonald]

Even if a boat righted after a 360 it would have enough water in it to make it very unstable and would roll to extremes, taking on more and more water until it sinks. I can't back that up with experience, thank God, so take it for what it's worth.

[newhaul]

Originally Posted by kmacdonald

Even if a boat righted after a 360 it would have enough water in it to make it very unstable and would roll to extremes, taking on more and more water until it sinks. I can't back that up with experience, thank God, so take it for what it's worth.

lock the drop boards and the hatch I'm sure would also help to have really big manual bilge pump as well as the electric ones

[kmacdonald]

Originally Posted by robert sailor

During the Queens Birthday Storm off of New Zealand one 44 foot cruising sailboat reportedly pitch poled and rolled 360 degrees. Now you might consider that an exaggeration but then you'd have to explain the aerial pictures taken from the NZ Air force showing the mast completely wrapped around the boat.

Did the boat survive or sink?

[Don C L]

This video is not the greatest because this is not a wave on the open ocean and the mast apparently hit the bottom keeping it from going all the way, but still you can see how eagerly it rights itself. If the sails had been up, it would have been different.

https://www.youtube.com/watch?v=blZswVXlTKg

and here is a canting keel boat:

https://www.youtube.com/watch?v=O4YKOAWk7kY

I'm pretty sure that if the boat still had its rigging and sails it would not come back up

[robert sailor]

Originally Posted by newhaul

I have never experienced a knockdown ( I assume lots of lead lots of wetted surface ) they have just gone to about 30° and dumped the wind.

The wind is never going to roll you but the sea certainly can with less effort than you might think. A breaking wave 1/2 the length of your boat on the beam is enough to do it in
most conditions. Depending on your boat design it may be as low as 30% of the length of the boat. If the wave is not breaking then it's a very low risk no matter the size.

[Paul Elliott]

Originally Posted by kmacdonald

Even if a boat righted after a 360 it would have enough water in it to make it very unstable and would roll to extremes, taking on more and more water until it sinks. I can't back that up with experience, thank God, so take it for what it's worth.

That's why we have hatches and washboards and strong portlights. If the boat is sealed up for heavy weather it's not going to take on much water. Sure, the cockpit will fill up, but that's not going to sink the boat. Of course if the mast rips the coach roof apart during a 360 rollover then all bets are off.

But if we sail conservatively and stay away from hurricanes, the chances of a rollover or even a knockdown are pretty minimal.

[robert sailor]

Originally Posted by kmacdonald

Did the boat survive or sink?

It survived but the following day the husband and wife were taken aboard a freighter as the husband was completely incapacitated during the roll, pitchpole.

[roland stockham]

Originally Posted by kmacdonald

Even if a boat righted after a 360 it would have enough water in it to make it very unstable and would roll to extremes, taking on more and more water until it sinks. I can't back that up with experience, thank God, so take it for what it's worth.

This is a very important part of 'seaworthiness' being rolled may be rare but waves sweeping the deck repeatedly is normal in storm conditions. You will never make the topsides totally watertight unless you sail submarine but good hatches, a small cockpit with BIG drains and pumps the are up to the job are essential. You must be able to clear any water before the next wavecrest hits even with the boat well heeled. My pump test is to remove the log and check the pumps will keep up with the inrush. (It's a great way to clean the bilge to) For me this sort of detail along with strength of deck fittings, grab handles etc are much more important to making a boat passage ready than basic design. Most boats designed for coastal sailing run into problems with the constant rolling and stress of a long passage.

[newhaul]

The op hasn't come on for a while but here is a good boat that I found on craigslist here
https://bellingham.craigslist.org/bo...375323403.html

[robert sailor]

You have to realize that if you turn a jar upside down and stick it in water it doesn't fill up because of the trapped air in the jar. A sailboat acts the same way for a period of time so as long as your not inverted for too long there is no reason a properly equipped boat with a seasoned skipper can not deal with it although that's the second best idea. Better to not put yourself in that position to begin with