The perils of Stabilizers

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Flatswing

Flatswing

Guru
Joined
Sep 21, 2016
Messages
658
Location
United States
Vessel Name
River Girl
Vessel Make
2004 DeFever 49 RPH
This beautiful KK 42 apparently got a little out of position in a narrow rocky channel near Lock 42 on the Trent Severn Waterway 2 days ago. I didn't witness it personally but the pics were given to me by a professional boat captain who was driving another boat travelling with them. Apparently, she tore off a stabilizer and sank within 10+ minutes. Fortunately all aboard were able to get to safety. The flow rates are high in the TSW this year and as the river /canal accelerates through narrow rock cuts, or merges with barrage dam outflows, the currents and boat reaction especially for those of us with keels can be dynamic. It's still safely navigable but one hand on the wheel with the other on the throttle(s) & highest level of concentration required in a few but fortunately predictable areas.

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Wow, I hate to see that.

Wonder if this could have been an installation issue? My understanding is that stabs are usually designed to break before the hull does.
 
Some years ago there was an article in PMM about a KK that had a similar fate due to a stabilizer grounding and vessel going down in shallow water. This incident was near Yucatan as I recall.

I'm not so sure this indicates the perils of active stabilizers as much as after market install design and hull integrity. It would be interesting to know more details. Regardless, so sad.
 
I've seen the hull damage to a KK42 when she hit the rocks. The stabilizer fin did not break away, it bent up splitting the hull open. I don't know if it is a KK42 structural problem, an after market installation problem or a general design problem with fin stabilizers.
 
I don't understand how these stabilizers aren't attached to protect the integrity of the hull. Sounds like a high risk problem at times.
 
Portage_Bay said:
I've seen the hull damage to a KK42 when she hit the rocks. The stabilizer fin did not break away, it bent up splitting the hull open. I don't know if it is a KK42 structural problem, an after market installation problem or a general design problem with fin stabilizers.
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Not saying this was a factor--there's still too many unknowns. Our Naiads have a detente in the shaft to supposedly allow the stab to break away, assuming the supporting blocks on the hull are strong enough. Hope never to put that to the test. ;)
 

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That raises the question about installing fins on cored hulls. I think KKs have balsa cored hulls so if sufficient reinforcement were not installed the hull might fail when the fin strikes a rock.
 
There are so many factors at play. It would be really educational to learn exactly what failed and how.

But before we get too far down the path of "stabilizers are bad", consider thruhulls for toilets, air conditioners, water makers, etc. They fail all the time for a wide range of reasons, and sink boats. Some aren't installed correctly, or degrade over time, or are of the wrong material, or have bad clamps, or have bad hoses..... Yes we still keep them all so we can enjoy those conveniences.

Everything on a boat is managed risk. There will always be failures, and just because there are isn't a reason not to take on a calculated and managed risk.
 
I think the key may be cored hulls and who installs the stabilizers.

Tio many times I have heard of Small yards taking on projects they really didn't research enough.

Cant say for certain in this case. But sure sounds like an engineering flaw in support.
 
This tells us more about Kady-Krogen than it does about fin stabilizers........
 
No it doesnt.

An issue resulting from an after market item without the results of a thorough investigation means nothing.

A KK 42 is much of tbe way through a circumnavigation, not a testament to its full capabilities or liabilities 100 percent, but so far so good.
 
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Woodland Hills said:
This tells us more about Kady-Krogen than it does about fin stabilizers........
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About 22 years ago (KK owners chime in) KK transitioned from cored to solid FRP below waterline. But as has been previously noted, details and facts regarding this incident would prove interesting.
 
I agree with PS. IMO if it was fin caused hull failure then it is probably an installation issue.
 
bayview said:
That raises the question about installing fins on cored hulls. I think KKs have balsa cored hulls...
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As far as I know, the KK42 till late in the production years, pvc was used as the core material before they did away with any coring below the water line. All of Krogens maketing literature confirms that.

Also, active stabilizers were not a factory option on the KK42s so the quality of the installation could vary.
 
psneeld said:
A KK 42 is much of tbe way through a circumnavigation, not a testament to its full capabilities or liabilities 100 percent, but so far so good.
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Not sure if that proves much about its construction.

But I do agree there is not enough information to make any kind of judgment either way.
 
IMO - And, although there is more info needed to assess the actual reason for sinking.


If it was due to a fin stabilizer tearing hole in the hull then the stabilizer design or the installation details were not as should have been.


Seems to me only common sense that an appendage hanging off hull bottom such as a fin stabilizer should have a "break-away" feature for if/when severe stress occurs no severe water ingress is result.


PODs do... as far as I understand they simply break off and sink if too hard a collision with underwater object happens... without leaving gaping hole in boat bottom. It's up to the owner to have salvage team retrieve the pod if desired.
 
Capt.Bill11 said:
Not sure if that proves much about its construction.

But I do agree there is not enough information to make any kind of judgment either way.
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It seems to me that we're even jumping to a conclusion by saying it was the stabilizer. I question how that was determined or if that was an assumption.

Assuming the only issue was the stabilizer, then absolutely it's an installation issue, regardless of the way the boat was constructed as the installation should take that all into consideration.

I recently heard a boater complaining that a yard refused to install fin stabilizers on a boat but told the owner they would install a Seakeeper. The owner thought they were just wanting to sell the more expensive Seakeeper. Their reasoning was they without doing a lot of structural reinforcement to the boat, it lacked the strength for a fin to be safely installed. He found someone else to install fins and was badmouthing the yard that refused. Perhaps the yard was right.
 
Art said:
PODs do... as far as I understand they simply break off and sink if too hard a collision with underwater object happens... without leaving gaping hole in boat bottom. It's up to the owner to have salvage team retrieve the pod if desired.
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That's the way it's supposed to work, but doesn't work that way 100% of the time.
 
yikes. That will ruin your day.

Not familiar with typical installation techniques but guessing since they are designed to keep maybe 10+ tons at 1.0G in heavy seas guessing there's not a real good way to engineer "break away" into that system. That's a lot of force to transmit under normal circumstances.
 
What it does is reinforce the need for good marine insurance with full coverage for environmental issues.
 
mbevins said:
What it does is reinforce the need for good marine insurance with full coverage for environmental issues.
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Yes, the payout for the loss of the boat is going to be small compared to the expense for salvage and for environmental.
 
BandB said:
Yes, the payout for the loss of the boat is going to be small compared to the expense for salvage and for environmental.
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I was just thinking that. Terrible place for a fuel spill - downstream is narrow and slow moving for 20 miles through prime cottage real estate.
 
We have no idea how much salvage and environmentsl might be, I jave worked on jobs like this that have come in under 50 grand.

Depending on how much diesek, which is hard to clean up so the authorities just might rewuire a boom, no real cleanup.

And a simple plywood patch might be all thats necessary and some float bags. A days salvage.

But of course we dont know all the details.
 
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