Another keel goes astray...French sailor survives 16 hours in an air bubble inside his capsized boat off Spain

Howler

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I couldn't remember what dropped Drum's keel so I just looked it up; looks like it was a builder failing to follow the designer's specification about heat treating some welds?
 

SloopJonB

Super Anarchist
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I think that's right - IIRC the original reports said they hadn't "J'd" the bolts and the lead just slid off but the photos didn't show any bolts sticking way up over the capsized hull.

Whatever the reason - those or the bottom ripping out or the bolts snapping off or whatever - it should be uncommon to the point of freakishness.
 

Howler

Member
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Whatever the reason - those or the bottom ripping out or the bolts snapping off or whatever - it should be uncommon to the point of freakishness.

Given that we've all heard of Cheeki Raffiki, it appears to be uncommon to the point of newsworthiness if not freakishness.
 

SloopJonB

Super Anarchist
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I don't agree.

"The facts: surely everybody remembers the keel that some years ago fell off a Bavaria Match 42 and recently all know that an almost new 90ft Oyster lost the keel. Some know about two First 40.7 but less know about a Bavaria 390, a Jeanneau 37, a Vand den Stadt 45, a Sweden yacht 42, a Fast 42 a Maxi 110, a Max Fun 35 or more recently a Comet 45 and some days ago a Davidson 50.

Nor many know that since the mid 80’s more than 75 boats have lost the keel with the loss of 28 lives.

Probably the numbers of keels lost or boats abandoned offshore with problems on the keel are way bigger and much bigger the number of boats that were found with keel problems before actually a disaster would occur. These are only the numbers regarding the cases that were found by a work group formed by World Sailing to study the problem and most of them were high profile cases.

Some of the keels were lost due to the contact with the ground or submerged objects, some due to poor design or poor building like the cases of the Match Bavaria 42, the modified Oyster 825 or the Max Fun 35. Others due to the weakening of the structure as a result of bad maintenance, groundings whose damage passed unnoticed or were improperly repaired while others, like the recent case with the Comet 45, remain a mystery."
 
Prior to Drum it rarely to never happened (I can't recall a single incident) and fin keels had been the norm for 15-20 years at that point.
I work as a mechanical engineer though not on highly loaded structures but my feeling is that all these software simulation programs every engineer uses these days are partially to blame.

Almost nobody does hand calcs anymore. You ball park the design based on your experience and run it through FEA, tweak a few things to hit your design target and send it. This leads to a false sense of security because you trust the software but don’t do as much agonizing over your assumptions of the max loading conditions.

When we were not as good at designing things to the limit before all the fancy software existed, a lot higher factor of safety was baked into the design that helped with lack of perfection in construction or installation.
 

12 metre

Super Anarchist
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English Bay
I agree in principle, but in reality hardly anyone is willing to incur the weight, performance, and financial penalties of specing a keel that will withstand a collision at speed with a semi-submerged shipping container. Maybe you could get away with it in a heavily built full-keel boat, but hardly anyone reading this site sails those.
Except that a grounding or collision seldom if ever results in the keel falling off (which is what we are talking about here). The damage from such a collision is more usually a puncture of the hull near the trailing edge of the keel, or destruction/delamination of the keel grid.

Keels falling off are more likely a result of large righting moments in modern craft combined with poor: design/construction/maintenance.

My guess is that most of the time it is due to the last 2 factors.
 
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ExOmo

Best Anarchist Ever
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I work as a mechanical engineer though not on highly loaded structures but my feeling is that all these software simulation programs every engineer uses these days are partially to blame.

Almost nobody does hand calcs anymore. You ball park the design based on your experience and run it through FEA, tweak a few things to hit your design target and send it. This leads to a false sense of security because you trust the software but don’t do as much agonizing over your assumptions of the max loading conditions.

When we were not as good at designing things to the limit before all the fancy software existed, a lot higher factor of safety was baked into the design that helped with lack of perfection in construction or installation.
Well hopefully you justify and defend your loading assumptions.
 
That’s my point, you can come up with whatever loading assumptions you want…….. but they all depends on perfect construction and assembly. With hand calcs you calculate the tensile, shear and bearing stresses separately. That gets you thinking about how bad any voids in the laminate there would be or if you over torque a bolt what would happen. With old fin keels, you had a lot of surface area and there was little weight penalty for doubling up on the minimum number of bolts and you had the space to do it. Assuming the hull laminate was ok…… it took a lot for one to fail enough to actually fall off and would likely have leaking keel bolts before that or have noticeable wag and hull flex like the old Cal’s have when the framing rots out.

With this one and the recent X2 that are high aspect ratio fin/bulb keels that fit up into a pocket in the hull, you have minimal area for bolts so large redundancy becomes a space issue. The keel fin is easier to pull and replace without messing up the paint and the keel fin doesn’t have a big stress riser where it meets a perpendicular flange but all the strength of the joint depends on a good fit with the hull. If the pocket has any structural or fit issues that allow the keel to wag at all, the bolts that were designed just to hold it onto the pocket now get seriously overloaded.

Had this issue with a race car. Aftermarket control arms that post crash analysis revealed a poor surface finish on the ball joint pin taper. They never seated properly in the upright and 8 hours of track time later the retention stud/nut popped of, the ball joint fell out of the upright, wheel locked up against the inner fender and the car left the track at 105mph and went into the wall at Laguna Seca at 70mph after crossing the grass and gravel.

Aftermarket company owned up to their mistake and gave us one of their race cars to flip so we could fix ours.

All the strength in a tapered fit depends on the fit being perfect.
 
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It's been 37 years since Drum.

For a supposedly conservative group, yacht designers seem to be pretty slow learners.
One without knowledge about sailing as sport would think this is more common than what it is:
yandy284875.jpg

19264514_823558467830600_6905101242847971113_o.jpg
 

longy

Overlord of Anarchy
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San Diego
Prior to Drum, keels had much larger roots and the racing rules frowned on too much keel derived stability. I'd look to bulbs with small struts as a bigger contributor than UFU's. The drive to achieve more stability/lower CG with less weight (both in keel & structure) have whittled away at safety margins. With the tiny attachment footprints of modern racing keels I don't think one can achieve a 100% safe keel without countering all the reasons one designs a keel like that to start with
 

Grande Mastere Dreade

Snag's spellchecker
I don't agree.

"The facts: surely everybody remembers the keel that some years ago fell off a Bavaria Match 42 and recently all know that an almost new 90ft Oyster lost the keel. Some know about two First 40.7 but less know about a Bavaria 390, a Jeanneau 37, a Vand den Stadt 45, a Sweden yacht 42, a Fast 42 a Maxi 110, a Max Fun 35 or more recently a Comet 45 and some days ago a Davidson 50.

Nor many know that since the mid 80’s more than 75 boats have lost the keel with the loss of 28 lives.

Probably the numbers of keels lost or boats abandoned offshore with problems on the keel are way bigger and much bigger the number of boats that were found with keel problems before actually a disaster would occur. These are only the numbers regarding the cases that were found by a work group formed by World Sailing to study the problem and most of them were high profile cases.


Some of the keels were lost due to the contact with the ground or submerged objects, some due to poor design or poor building like the cases of the Match Bavaria 42, the modified Oyster 825 or the Max Fun 35. Others due to the weakening of the structure as a result of bad maintenance, groundings whose damage passed unnoticed or were improperly repaired while others, like the recent case with the Comet 45, remain a mystery."
how come small boats don't lose their keels ?
 

nota

Anarchist
so why the big orange square if the keel is only bolted up it a stupid narrow line along the thin center bit

if my amateur ideas were used the whole square bit would be the attachment points area to spread the load over an area that allows the keel to stay in place
 

longy

Overlord of Anarchy
7,011
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San Diego
Small boats have smaller mass - so any impact can be can throw the whole boat around, spreading the impact forces around more of the structure. And being smaller, have less chance of running aground or hitting any UFO's

Some racing rules require a ceertain sq footage of orange paint on the underbodies for rescue visibility. Has nothing to do with structures.
 


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