Keel failure - how to stay upright

[Tin Tin]

These guys had a bit of time to figure out how not to capsize - any thoughts - my 2 cents - tie two dyneema lines to the side cleats around the keel so when broke off it would still be under the boat - would this work?


https://www.sailingscuttlebutt.com/2...pacific-ocean/

[StuM]

If you've got plenty of warning, it's a bulb keel and sea conditions are OK, that would make sense, but I suspect that those circumstances will occur very rarely.

[LittleWing77]

Originally Posted by Tin Tin

These guys had a bit of time to figure out how not to capsize - any thoughts - my 2 cents - tie two dyneema lines to the side cleats around the keel so when broke off it would still be under the boat - would this work?
https://www.sailingscuttlebutt.com/2...pacific-ocean/

Really good read, TinTin, thanks for posting.

No, unfortunately, your improvised method of saving the keel wouldn't have worked in the particular, nor in the general. The sea exerts tremendous force on structures when they fail. Like wiggling a loose tooth, but with much more force. Just consider yourself alone, abovedecks. How many micro-adjustments do we constantly make underway just to stand upright? That same motion and movement is continuously happening below the waterline at sea. Not to mention the dynamic forces of counterbalancing sails. Once that attachment point had given way, the shape of those keels (like a pencil with a big bulbous eraser at the end of it), meant that it went go straight to the bottom - aided by all the weight in that end-bulb. Wouldn't matter how many lines you wrapped around it.

Ran Tan had a highly specialised racing keel and once you read the entire article (click on the "Read Full Report" ) including technical analysis, you can see that it was a case of fatigue exacerbated by the fact that canting keels are regularly subject to knockdown loads - and the boat was 13 years old.

I never liked canting keels much when I still chose to race and now that I've read the technical analysis in that article, I can see there was a rationale behind my unsubstantiated unease...

<Sigh> But I always hate to read of the loss of a gorgeous boat! So glad the crew was smart - and ultimately, saved.

Thanks, Tin Tin!
Warmly,
LittleWing77

[Tin Tin]

A picture in the full report towards the end shows a bulb keel with some sort of strap arrangement around the bulb.
https://www.sailmagazine.com/cruisin...zed-ran-tan-ii

[LittleWing77]

Originally Posted by Tin Tin

A picture in the full report towards the end shows a bulb keel with some sort of strap arrangement around the bulb.
https://www.sailmagazine.com/cruisin...zed-ran-tan-ii

Yes. Very pretty picture of a healthy-looking bulb keel in a non-canted postion, not in the ocean and with no forces whatsoever on it. The strap shown has nothing to do with being used to keep the keel attached to the boat - and wouldn't work even if it were employed to attempt it.

Sorry you don't understand. I did try to explain it as simply as possible, with alternative images to assist in your visualizing.

Maybe if you read the technical keel analysis at the end of the article by the guys who actually fabricate these wild keels, it might help in wrapping your mind around the concepts.

Kind regards,
LittleWing77

[Sailmonkey]

Originally Posted by Tin Tin

A picture in the full report towards the end shows a bulb keel with some sort of strap arrangement around the bulb.
https://www.sailmagazine.com/cruisin...zed-ran-tan-ii

That strap is there for a righting test. The boat is set in the water, the crane then takes hold of the strap that’s around the keel and lifts until the hull is either 90 degrees or inverted.

Like this

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

[Tetepare]

It would work on a Sunfish.

[MicHughV]

I believe the picture towards the end in the above article is on another boat.

This is an interesting topic for me.

As a retired structural engineer, this topic has always held an interest for me.

In the three boats I've owned, the keel/hull connection was always an area of prime interest to me, knowing the forces involved.

It's not that uncommon to see keel/hull separation when looking at boats that have been hauled out. Failure at this joint can be caused by a variety of things, but a standard keel is usually attached to the hull along a reasonable long length, distributing the load.

Not so a modern racing keel, which is predominantly a long thin blade with a massive weight on the end, providing a monster moment arm with little structural area to spread the load. The earlier singlehanded round the world races can attest to the problems in this area, especially were one to hit some or other submerged object.

Additionally, a canting keel is a different animal in that it is often forced out to the side at extreme angles in order to balance a usually towering rig. In addition to the sideways angle, the boat is also jumping around.

All told, that keel/hull joint has to take some serious loads. Now add in some exotic materials in order to keep the hull as light as possible and yes, I can see where fatigue is a likely culprit. Modern exotic hull building materials is not my forte, but I can easily see where a basic unforgiving and exotic material coupled with an equally massive, yet thin keel would give me thought to shudder. Those older racing boats still had not quite dialed in the scantlings yet as exotic building materials were still in the earlier years..

A total loss of keel, on that boat, in my opinion, would result in an immediate capsize under sail, so they did the right thing, in lowering the sails and reducing anything that might promote an unbalanced boat. Even after abandoning the boat, the boat could have been capsized by a wave, but as no-one was there to witness it, pure conjecture on my part..

These things usually happen at night as well, adding more drama to an already perilous situation.

I take my hat off to the modern IMOCA class sailors that are willing to zip around the globe at 30 knots with one of those keels.

I sure wouldn't do it.

[Minggat]

Originally Posted by MicHughV

It's not that uncommon to see keel/hull separation when looking at boats that have been hauled out.

I sure wouldn't do it.

I know of more dismasting stories than I do of lost keep stories..... by exactly one. Maybe 3 if you count broken mast. Zero lost keel first hand stories, but we all know that it does happen.

If by separated, do you mean the keep came off? Or simply showed signs of movement?

OK.

I see that the OP did not list a boat. Is this really a worry, or just a "what about pirates and sleeping whales and lost/floating containers?"

I'd say, don't play with such vulnerable boats.

I have an old boat with a bolt on keel that showed signs that it was not as tight as it was new. It was a serious worry for me... for years.

I like peace of mind. I found this guy and paid for the peace of mind.
https://www.keelboltrepair.com/
It cost a fraction of what I feared it would.
Maybe it's a false sense of security, but it's better than what I had before.

Now the pirates and sleeping whales and even the containers fear me.

And I feel more secure with a keel stepped mast than a deck stepped one.

[morribabes]

I'd have been very tempted to bring the mast down. Without it, I would expect a keel-less hull would be quite stable.

[Minggat]

Originally Posted by morribabes

I'd have been very tempted to bring the mast down. Without it, I would expect a keel-less hull would be quite stable.

Assuming the keel didn’t leave any holes in the bottom.

Sorry, I can only relate to what I have.

[waterman46]

Originally Posted by Minggat

I know of more dismasting stories than I do of lost keep stories..... by exactly one. Maybe 3 if you count broken mast. Zero lost keel first hand stories, but we all know that it does happen.

If by separated, do you mean the keep came off? Or simply showed signs of movement?

OK.

I see that the OP did not list a boat. Is this really a worry, or just a "what about pirates and sleeping whales and lost/floating containers?"

I'd say, don't play with such vulnerable boats.

I have an old boat with a bolt on keel that showed signs that it was not as tight as it was new. It was a serious worry for me... for years.

I like peace of mind. I found this guy and paid for the peace of mind.
https://www.keelboltrepair.com/
It cost a fraction of what I feared it would.
Maybe it's a false sense of security, but it's better than what I had before.

Now the pirates and sleeping whales and even the containers fear me.

And I feel more secure with a keel stepped mast than a deck stepped one.

.

But wouldn't you would feel even more secure if you had ballast encapsulated in the hull?

[MicHughV]

Minggat, that is a tough question to answer.

Different boat and keel manufacturers use different type of bolts, different diameters, different thread, different depth of embedment, different methods of anchoring the bolts in the keel, different bolt layout, etc, etc.

Then you get the earlier keel manufacturers and the later one's...

Keel material also varies.

...and then there is the actual hull material to which the keel is attached.

Keel failure is not as uncommon as you might think. You can go online and read several stories about boats parting with their keels..

Lift the floor boards of any vessel and you will likely see some rust stain around the keel bolts or retaining washers.

It is not the first time I've seen a keel re-bedded on a boat during a haul out.

My first boat was a home built steel ketch...it had a poured-in-place lead into the keel cavity, probably as safe a keel as you can find.

Some earlier fiberglass boats had a keel shoe which was attached to fiberglass stub...most modern boats have the bolt on type keel.

Regardless, an inspection of the hull/keel joint at a haul out is probably warranted for any boat. It can start with just a hairline crack.

Most bolt on keels also have a healthy layer of 5200 sealant between hull and keel to keep seawater from penetrating to the keel bolts, but quality control is sometimes an issue here.

No definitive answer to your question..

[tilostahl]

The Imoca 60 Hugo Boss in the 20196 Transat Jaques Vabre provides an interesting story. In mid-Atlantic they hit a UFO and their canting keel was damaged. It started flopping around under the boat so they cut it loose, which you would think would lead to a capsize. Instead they filled their water tanks, dropped both daggerboards (neither are options on your typical cruising boat), reduced sail and headed toward a downwind port. They were lucky because wind and waves were benign, and they brought the boat home.

The moral of the story is: you don't want a big, heavy keel flopping around under your hull. Better to cut it loose than try and strap it in place.

[nortonscove]

Originally Posted by MicHughV

Minggat, that is a tough question to answer.

Different boat and keel manufacturers use different type of bolts, different diameters, different thread, different depth of embedment, different methods of anchoring the bolts in the keel, different bolt layout, etc, etc.

Then you get the earlier keel manufacturers and the later one's...

Keel material also varies.

...and then there is the actual hull material to which the keel is attached.

Keel failure is not as uncommon as you might think. You can go online and read several stories about boats parting with their keels..

Lift the floor boards of any vessel and you will likely see some rust stain around the keel bolts or retaining washers.

It is not the first time I've seen a keel re-bedded on a boat during a haul out.

My first boat was a home built steel ketch...it had a poured-in-place lead into the keel cavity, probably as safe a keel as you can find.

Some earlier fiberglass boats had a keel shoe which was attached to fiberglass stub...most modern boats have the bolt on type keel.

Regardless, an inspection of the hull/keel joint at a haul out is probably warranted for any boat. It can start with just a hairline crack.

Most bolt on keels also have a healthy layer of 5200 sealant between hull and keel to keep seawater from penetrating to the keel bolts, but quality control is sometimes an issue here.

No definitive answer to your question..

Practical Boat Owner looked into this issue after the Cheeki Rafiki incident. In searching the available reports it was found that keel failure is indeed rather rare. Almost all cases were precluded by a hard grounding or some other impact. The exception to this was in metal boats, which by the way had the most failures by a considerable amount. Those simply seemed to fail due to poor build quality and made up the majority of the reports. It's counter to what most people believe but reasonable when given consideration.