# Beneteau Keel bolts



## Lazerbrains (Oct 25, 2015)

The keel bolts held. The structure failed.

Just saw this today on Facebook, posted by a salvage operation. This Beneteau apparently hit a reef and sunk in 5 minutes when the keel snapped off. What suprised me in the photos is that it doesn't look like keel bolts failed - instead it looks like the bottom of the boat ripped away with the keel. I would have thought the bolts would pull before the structure itself would fail.


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## celenoglu (Dec 13, 2008)

The safety factor for keel bolts is 7 or more. That means they can carry 7 times the load they are currently carrying. It is generally the body that is broken. You can see many images of keel bolts nearly half gone due to corrosion but still doing their work.


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## Lazerbrains (Oct 25, 2015)

Yes, but the bolts held in this case. What failed is the structure they were bolted to.

I probably should have used a different title to the thread.


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## JimsCAL (May 23, 2007)

I agree that it is good engineering to have a large factor of safety in the keel bolts to account for possible corrosion over the years. What I don't think is good engineering is these deep small cross sectional area blade keels with a bulb on the bottom. The forces applied in a grounding are huge and the small hull area that must carry that load is just not enough


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## deniseO30 (Nov 27, 2006)

Is that plywood in there???


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## Lazerbrains (Oct 25, 2015)

deniseO30 said:


> Is that plywood in there???


Kinda looks like OSB, but could just be torn fiberglass matt/roving. Hard to tell from the photo. I can see the structural grid in the photos.


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## Guyfromthenorth (Jul 2, 2015)

I'm not a GRP engineer by any stretch but I am surprised to see how cleanly the keel stub snapped off. You would think that (when properly engineered) the FG would have torn away up the hull a bit as it's supposed to be laid up in a way that disperses the load to a large area of the hull. I would picture it snapping off more like peeling a large sticker in any number of directions along the FG layers rather than snipping off almost cleanly like a matchstick.


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## deniseO30 (Nov 27, 2006)

Pics shows very small keel stub opening which makes me think it was a bulb keel and it was snapped off laterally. Guessing if a keel were wedge between two rocks, a few rocking actions port and starboard would probably snap it off in short order


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## Jeff_H (Feb 26, 2000)

As others have noted, this is a very unusual failure for a small keel root detachment failure. Normally, in these failures there is a large area of the laminate that is pulled loose, and often the hull is pulled free from the frame and pan. In this case the keel bolt washers (which are rectangular plates that span between each pair of bolts and are roughly 5/16" thick stainless steel which was compliant with the ABS standard at the time the boat was built but which should have been 7/16" under the current ISO 12215-9 standard) sheered through both the hull and pan, and sheered through the bottom of the transverse frame as well. I can't even visualize what directional force would cause that type of failure except fatigue at the edges of the plates taking a toll on the matrix and causing it to weaken to the point of failure.

The laminate in this area was all solid glass and was made up of uniaixial and biaxial fabric. The pan and frame structure is glued to the hull skin with an engineered adhesive. The tan color is probably that adhesive.

A hard grounding would have been expected to pull the forward bolts downward tearing them out of the hull and tearing the joint between the pan and the hull, and would have pushed aft edge of the keel up through the hull tearing the matrix back there. But in the photo there does not appear to be those kinds of compression marks aft the aft end of the keel. If the boat was run aground in a surf and was sideward to the waves, you would similarly expect one side to have sheered outward and torn the laminate outward and had a inward sheer failure on the opposite side of the keel. You would expect the transverse frame to be completely mushroomed on one side, but it does not appear to be the case. And if the boat was dropping vertically on hard bottom (similar to one of the contributing causes of the failure on the Cape Fear 38 some years ago) you would similarly expect to wide spread delamination and crushing of the frames.

To me the mystery here is the comparatively clean cut opening which almost suggests a failure mode where the boat was lifted vertically while its keel was held down some how. (I am not saying that actually happened just at first glance, that is how the damage looks).

But I am also interested in the fact that the boat in the picture looks like a 40.7. The construction and inspection during building of the keel attachment is outlined in the report on the sinking of the Cheeki Rafiki. https://assets.publishing.service.gov.uk/media/55408664e5274a157200005b/MAIBInvReport_8_2015.pdf

What was evident in the report was that the Beneteau 40.7's went through an extraordinary testing and inspection process compared to most production boats, with layup made up of precut laminate and the resin weighed. Hull thickness measured at each keel bolt hole on each boat, and each penetration on each boat with the coupons from through hulls tested for thickness and resin/reinforcing properties. And lastly the construction process is observed during construction by an independent testing company. That level of care just is not done on production boats.

And in the Annex C&D to the report, the Wolfson Unit, did a detailed analysis of the structure of these boats. https://assets.publishing.service.g...nnexesToMAIBInvReport08-2015_CheekiRafiki.pdf

There is a chart with their results of the analysis. The table summarises the results of assessing the structure design, and concluding that depending on the element the design was between 1.05 to 7.96 in excess of the requirements of the standards when the Cheeki Rafiki was built, and that only the washer thickness would not comply with current standards. It also noted that Cheeki Rafiki was built differently than the original design, (and alegedly other 40.7's) and as built one of the designed keel bolts was missing. While that would have met the ABS standard of the day, it would only meet 95% of the current EU ISO 12215-9 standard.

And yet, with all of this care in design, construction, and with values exceeding the standards of today, this is the second of these boats to lose a keel.

One other interesting item in the Cheeki Rafiki report is a table looking at boats which have lost keels since 1984, which are summarized in Table 4 below.
Table 4: Summary of ISAF data on keel failures
Cause of failure Number
Undefined 40
Welded fin failures 11
Grounding or collision 8
Hull/internal structure 8
Keel bolts 3
Keel cant system 2
Total 72

Its interesting to me that over 20% of the failures are due to grounding, collision, or hull/internal structure failure, while 4% is was actually caused by keel bolt failure. That said, there were a number of keel bolt failures last year in older boats that would skew that number quite a bit.

Lastly, while these small root footprint keels are definitely more difficult engineering problem, over my lifetime, boats have been losing their keels no matter how long their keel root and how they were built. My family's CCA era Pearson Vanguard lost its encapsulated keel in 1970 due to a hard grounding. A number of IOR era boats lost their keels (Drum being the most famous) despite having a comparatively large keel root, and yes, newer designs are losing their keels as well, which is why World Sailing (AKA the former IYRU) is studying this issue as we speak, and hopefully will come up with better standards.

Jeff


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## Jeff_H (Feb 26, 2000)

celenoglu said:


> The safety factor for keel bolts is 7 or more. That means they can carry 7 times the load they are currently carrying.


I have to ask, how did you come up with this statement?

After all, when you say that keel bolts are designed to safety factor of 7 do you mean that in all loadings (static, steady-state and impact- whether vertical, lateral and from fore and aft) the keel bolts are designed to take 7 times the expected load?

Or are you saying that keel bolts are simply designed to carry 7 times the weight of the keel, regardless of the induced forces due to heeling and dynamic loads?

Are you saying as a fact that the keel bolts on this boat were designed to be 7 times stronger than the any of these loads?

Are you saying that ABS (which this boat was designed to) required a safety factor of 7 for the keel bolts (ABS didn't) or that the ISO standards require a safety factor of 7 for keel bolts (they don't)?

So what is it that you are trying to say?

Jeff


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## Lazerbrains (Oct 25, 2015)

Jeff -

Looking at the photos it seems that the antifoul around the keel area flaked off.

Possible sign of flexure near the keel before it broke off?


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## Jeff_H (Feb 26, 2000)

Lazerbrains said:


> Jeff -
> 
> Looking at the photos it seems that the antifoul around the keel area flaked off.
> 
> Possible sign of flexure near the keel before it broke off?


Good point, I had seen the bottom paint flaked off around the keel. You may be right that there was flexure near the keel before the failure which led to the paint failure.

I actually has blown up the close up photo trying to get a better sense of what could have caused this. When I did there were a few more oddities visible. For example if the failure resulted from a lot of flexing of the hull, you would expect to see a lot of spider cracks in the gelcoat and barrier coat, I don't see those.

When you blow the picture up, it looks like you can see the second and third from the stern keel bolt washers in place and intact. That would suggest that this was in part a keel bolt failure, but if this was a keel bolt failure, then what would have caused the hull to tear away.

The shoal draft version of this boat had an iron keel with iron keel bolts, and perhaps they rusted and dropped the keel, but I still have to wonder what then would have caused the comparatively clean cut that is visible in the picture.

It will be interesting to see what is figured out. Anyone know where this occurred and what happened to cause the keel to separate?

Jeff


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## Lazerbrains (Oct 25, 2015)

Found out a little more information. The boat is a 2006 Beneteau First 36.7 per the salvager who pulled her up.

Freshwater boat.


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## zedboy (Jul 14, 2010)

Those French guys are dang good engineers. Lots of math, finite element analysis, safety factors.

But that's not how you attach a high-aspect, bulbed keel. This is how you attach a keel.

(the keel bolts to the bottom. the sides bolt to the longitudinal stringers. posted earlier today, from Francis Lee)


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## hellosailor (Apr 11, 2006)

"I would have thought the bolts would pull before the structure itself would fail."
And in fact, just aft of center, it appears that one of the keel "stud bolts" that B inserts into the top of their cast iron keels, is still attached to the hull on the starboard (down) side of the keel mounting area.
Is the saildrive normal on that model? Or does it reflect a boat in the EU market?


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## timangiel (Sep 8, 2006)

It just seems strange to see a sunken boat pulled up with the main still covered and the jib furled up like that, almost looks like it sank at a dock. The tear does look a little more jagged on the forward side. Can’t wait to hear more details on the circumstances leading up to that.


Sent from my iPhone using Tapatalk


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## midwesterner (Dec 14, 2015)

timangiel said:


> It just seems strange to see a sunken boat pulled up with the main still covered and the jib furled up like that, almost looks like it sank at a dock.... Can't wait to hear more details on the circumstances leading up to that.
> 
> Sent from my iPhone using Tapatalk


It could have happened while motoring and they ran it into something.


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## Lazerbrains (Oct 25, 2015)

According to the salvager, it "hit a reef".


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## Lazerbrains (Oct 25, 2015)

Another photo. Apparently they made a quick plywood/5200 patch and pumped out the water to get it back in.


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## RobertFarrell (Aug 28, 2018)

I wonder if they had a depth finder?


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## celenoglu (Dec 13, 2008)

The keel bolts are3 designed to carry 7 times the weight of the keel.


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## zedboy (Jul 14, 2010)

Lazerbrains said:


> According to the salvager, it "hit a reef".


At 5-6 knots that 2m keel makes one hell of a lever arm whacking into a bommie.

Depth everywhere else coulda been fine.


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## Lazerbrains (Oct 25, 2015)

They recovered the keel. Pics attached.

The bolts are still intact. Fiberglass ripped apart. Not much backing for the bolts.


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## Minnewaska (Feb 21, 2010)

The backing plates look bent up on the port side, giving the appearance of failure due to leverage from the side. Are there any pics of the keel that show where it was impacted? I wonder if it drove up onto a ledge, with the boat falling off to one side. Jury is out on whether this is a manufacturing issue or just a freak failure scenario. It will be very interesting to find out.

p.s. those keel bolts look better than mine (which are being replaced this Fall.


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## deniseO30 (Nov 27, 2006)

zedboy said:


> Those French guys are dang good engineers. Lots of math, finite element analysis, safety factors.
> 
> But that's not how you attach a high-aspect, bulbed keel. This is how you attach a keel.
> 
> (the keel bolts to the bottom. the sides bolt to the longitudinal stringers. posted earlier today, from Francis Lee)


Is this picture relevant to the boat that sunk at all??? I sure do like this amazing structure. In wooden boat construction you would see this type of construction, those "beams" in a wooden boat would are called floors not to be confused with a floor, as you some of you may know a floor in a boat is called a sole.


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## Morild (Mar 31, 2013)

Lazerbrains said:


> They recovered the keel. Pics attached.
> 
> The bolts are still intact. Fiberglass ripped apart. Not much backing for the bolts.


What?
Shouldn't there have been some stringers across?
It couldn't just have been bolted through the laminate with backplates?

:eek


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## Jeff_H (Feb 26, 2000)

celenoglu said:


> The keel bolts are designed to carry 7 times the weight of the keel.


That is just plain silly. Where did you come up with that idea? It makes absolutely no sense at all and bears no resemblance to reality. When dropping off a wave while heeled the side force on a keel and the sudden deacceleration can result in a tensile load on the bolts that can approach a range that is 20-40 times the weight of the keel. Or to look at this from another approach, each of those bolts has roughly a 50,000- 55,000 lb tensile strength and the keel only weighs 3748 lbs that is something in the range of 14 times the weight of the keel for each bolt.



Morild said:


> What?
> Shouldn't there have been some stringers across?
> It couldn't just have been bolted through the laminate with backplates?
> 
> :eek


If you look at the first set of pictures you can see that there are transverse frames (what Denise rightly calls floors) that are sheered off where they turn down into the bilge. The photos of the top of the keel show gaps where these frames were located and there torn fibers which are probably from the biaxial cloth used as reinforcing in this area of the boat and which were withdrawn from the hull and frames . Having the bolts through thickened laminate between the frames is pretty typical construction for a glass boat with a bolt on keel, but the failure mode is not very typical at all.



Minnewaska said:


> The backing plates look bent up on the port side, giving the appearance of failure due to leverage from the side. Are there any pics of the keel that show where it was impacted? I wonder if it drove up onto a ledge, with the boat falling off to one side. Jury is out on whether this is a manufacturing issue or just a freak failure scenario. It will be very interesting to find out.
> 
> p.s. those keel bolts look better than mine (which are being replaced this Fall.


I noticed the bent plates as well. It looks like there was a blow from the port side that pushed the keel towards the starboard. The port side of the base plates appear to have sheered downward through the laminate and were bent in the process. I still don't understand what happened have created such a clean cut. After all, even if the plates sheered down through the laminate, you would have expected the adjacent laminate to be peeled apart. Similarly, if the keel sheered upward from through the laminate on the starboard side you would have expected the transverse frames to be crushed on that side which they don't appear to be.

This looks like a lead keel and the paired bolts on a lead keel of this model are actually one U-shaped rod that is threaded on both ends to take a nut. The single bolts are J-bolts and you can see how well they faired with the aft bolt literally being torn out of the keel. Compared to many of the newer race boats, that is actually a pretty big root area.

It will be interesting to hear what is learned as the story develops.

Does anyone know if everyone on board was okay?

Jeff


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## Lazerbrains (Oct 25, 2015)

Jeff_H said:


> I still don't understand what happened have created such a clean cut. After all, even if the plates sheered down through the laminate, you would have expected the adjacent laminate to be peeled apart. Similarly, if the keel sheered upward from through the laminate on the starboard side you would have expected the transverse frames to be crushed on that side which they don't appear to be.
> 
> It will be interesting to hear what is learned as the story develops.
> 
> ...


The keel hit a reef while under motor power. I don't think it is hard to understand why it failed. Occams razor = inadequate construction to sustain hitting a reef at 5kts. The fiberglass ripped cleanly away as it was not strong enough to sustain such an impact. Backing plates are woefully undersized - not much better than washers.
Other boats can wash ashore after a hurricane and keep their keel without the benefit of floatation. This simply looks bad for Beneteau, no easy way around it. 
No one was injured, fortunately.


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## MastUndSchotbruch (Nov 26, 2010)

Lazerbrains said:


> This simply looks bad for Beneteau, no easy way around it.


D'accord


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## deniseO30 (Nov 27, 2006)

It's amazing to me that we don't hear about keel loss even more, the way people zip around without charts or knowing how to use electronics. Or even a basic of understanding how to read a chart.


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## Jeff_H (Feb 26, 2000)

Lazerbrains said:


> The keel hit a reef while under motor power. I don't think it is hard to understand why it failed. Occams razor = inadequate construction to sustain hitting a reef at 5kts. The fiberglass ripped cleanly away as it was not strong enough to sustain such an impact. Backing plates are woefully undersized - not much better than washers.
> Other boats can wash ashore after a hurricane and keep their keel without the benefit of floatation. This simply looks bad for Beneteau, no easy way around it.
> No one was injured, fortunately.


Do we know it hit reef under power? Do we know if anyone was hurt?

To me, if your conclusion is correct, this is far more serious than a Beneteau problem. The thing is that the 36.7 and 40.7 were not normal production racer-cruisers. Farr's office engineered these boats to be beyond the standard of the day, and an independent structural analysis of the 40.7 concluded that the both the engineering and the actual construction of the laminate and framing were capable of withstanding loads that are nearly 8 times those required by the current European standards, and which are much higher than the older ABS and D. LLoyds standards, which had been the previous standard.

Beyond that, these boats were subjected to a higher level of inspection and quality control than almost any production boat that I ever heard of, and higher than many if not most high quality limited production boats ever receive. And independent lab supervised the construction of the boats. The resin was weighed. Laminates were precisely cut and had placement and alignment patterns marked on the reinforcing. The pan/framing adhesive material and placement method was tested extensively before being used, and was machine placed and checked to assure proper coverage. Once the hull was laid up, actual samples of the hull were measured for thickness, layup and were burn tested for resin to reinforcing ratios. That just is not done even on extremely expensive limited production or custom boats.

So if you are correct that, " The fiberglass ripped cleanly away as it was not strong enough to sustain such an impact. Backing plates are woefully undersized", then that has serious implications for the vast majority of boats out there which are only designed to meet the basic structural standards and which are not the result of this high level of engineering, and or produced under the high level of supervision during construction.

But the other part of this is that these boats had a very sophisticated and complete framing system as compared to the vast majority of boats that are out there. That kind of framing should have been able to handle the service loads without allowing much flexure. (In fact when I sailed on 40.7's I was amazed at how little these boats flexed under heavy load in a steep chop.) The result of that stiffness is that by minimizing flexure these boats should lose less strength over its service life due to fatigue as compared to the vast majority of boat that are out there and which flexes more than these do.

So if your conclusion is right, the implication of all of this is huge on the industry as a whole. To put a finer point on this, since these boats were structurally designed well in excess of the current standards, which in turn are well in excess of the older standards, and when you consider that few older boats had anywhere near the rigidity, engineering and quality control of these boats, you would have to wonder about the safety the vast majority of boats out there, especially the older boats where the laminate materials and layup schedules were no where near what was used on these boats and which have been further weakened by a lifetime of fatique.

Jeff


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## zedboy (Jul 14, 2010)

deniseO30 said:


> Is this picture relevant to the boat that sunk at all??? I sure do like this amazing structure. In wooden boat construction you would see this type of construction, those "beams" in a wooden boat would are called floors not to be confused with a floor, as you some of you may know a floor in a boat is called a sole.


Quite right: this picture is from Bob's wooden _Francis Lee_ - it's what he posted as an example of the right way to attach a keel.


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## Lazerbrains (Oct 25, 2015)

I dunno what you mean, Jeff, by "designed in excess of standards." What I see (quite clearly) is a keel bolted to a fairly thin,flat area of fiberglass with no sump nor much reinforcement, and woefully small backing plates that do not look to be up to the task of distributing the load very well. In fact, it is no suprise to me that the fiberglass ripped away right at the edges of the backing plates. This simply looks like weak engineering and most boats I have inspected seem better engineered than this. The pictures tell the story.


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## paulk (Jun 2, 2000)

Saw on another site (Cruiser's Forum) that this occurred in Wisconsin, Door County(?) in Green Bay (the bay, not the city) with the boat, under sail in a 15-20 knot breeze, being run into Hanover Shoal. A Reef Encounter - Cruisers & Sailing Forums

If it was blowing that hard it's possible they were doing better than 7 knots when, WHAM!

Have subsequently seen comments saying boat was under power, not sail, when it hit. Photo on Cruiser's Forum shows what looks like an unfurled jib floating in the water, but others do show jib tightly furled on the forestay.


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## overbored (Oct 8, 2010)

I am not sure that making a supper stiff structure is a good thing for a fiberglass boat. stiffer is not necessarily stronger. they my have made the surrounding structure so stiff that it limited any flexing to a very small area which caused the fiber glass to break down from flexing fatigue just under the keel bolts. they caused a stress riser around the keel mounting area and when the keel hit something it let go all at once. a hull that flexes a bit will spread the load over a bigger area and not just snap off along a straight line. any time you have a stiff structure you will find the weakest link sooner the later.


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## Lazerbrains (Oct 25, 2015)

paulk said:


> Saw on another site (Cruiser's Forum) that this occurred in Wisconsin, Door County(?) in Green Bay (the bay, not the city) with the boat, under sail in a 15-20 knot breeze, being run into Hanover Shoal. A Reef Encounter - Cruisers & Sailing Forums
> 
> If it was blowing that hard it's possible they were doing better than 7 knots when, WHAM!


That report is incorrect. Boat was under motor power, as evidenced by the foresail being furled and the mainsail cover still on.


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## overbored (Oct 8, 2010)

there is pic on the last page of this ad of the internal support structure of a 36.7 
http://www.curtisstokes.net/pdf/sailboat-for-sale-beneteau36-southern-cross.pdf


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## Jeff_H (Feb 26, 2000)

zedboy said:


> Quite right: this picture is from Bob's wooden _Francis Lee_ - it's what he posted as an example of the right way to attach a keel.


While I personally would never question Bob Perry on any aspect yacht design, and that is a very robust way to attach a keel and may be the exact right way to attach a keel on a 60 foot wooden boat with a slender keel, its not the only "right way" to attach a slender keel. Now that Bob is working with carbon fiber, I assume that he would have a composite method of attachment if the hull was composite. And beyond that, the framing system used on the 40.7 and 36.7 are essentially composite versions of the keel attachment used on Francis Lee

Jeff


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## Lazerbrains (Oct 25, 2015)

What is nice about Bob's design is that it spreads the load out over a wide area - if this Bene had comparative area of backing to support the keel, it would not so likely have ripped away the fiberglass so easily as it did. Those backing plates aren't any wider than the keel.


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## Jeff_H (Feb 26, 2000)

Lazerbrains said:


> I dunno what you mean, Jeff, by "designed in excess of standards." What I see (quite clearly) is a keel bolted to a fairly thin,flat area of fiberglass with no sump nor much reinforcement, and woefully small backing plates that do not look to be up to the task of distributing the load very well. In fact, it is no suprise to me that the fiberglass ripped away right at the edges of the backing plates. This simply looks like weak engineering and most boats I have inspected seem better engineered than this. The pictures tell the story.


Its not what I mean, since its not my conclusion that this boat was designed in excess of the current standards. It was the conclusion of a post construction analysis by the Wolfson Unit. In post #9 I posted links to Annex C&D which was the analysis done by the Wolfson Unit on the structural system on the 40.7's. Annex C & D speak for themselves. But that is what I was quoting when I made that statement. (You might take a look at that since its very well written and discusses many of the points in more detail than I am summarizing here.)

The one area that the report said was deficient under current standards was the keel bolts on that particular 40.7 built. The aft most centerline keel bolt was omitted on the boat in the report. (That is the bolt which failed on the subject boat of this thread as seen in the pictures of the top of the keel). Without that bolt, the bolts only achieved 95% of the current standard but still met the prior standard. This boat obviously had that last bolt present. But this was clearly not a case of a keel bolt failure (except that arguably may have been a bolt failure in the case of the aft most centerline bolt)>

In any event, whatever you think you see, the report in that link analyzed both the original engineering and construction of a 40.7 as it was actually built and concluded that the internal structure of the keel was 7.96 stronger than required under the current standards. And while those backing plates may seem small to you, they are larger than required by the standard and certainly larger than those that I have observed in many popular production boats, as well as on some higher end limited production boats. (i.e. Swan or on a similar sized Hallberg-Rassey)

To be clear, I am not saying that the structure was adequate for the loads that this boat encountered. Assuming that this keel was not in some way compromised by some other set of circumstands, obviously it wasn't.

But what I am saying is that what makes this model a little unique is the level of care that this model had in its design, building, and post construction analysis. My key point is that based on the post construction analysis by arguably the most advanced yacht structural engineering lab in the world, that the 40.7 and 36.7 were designed to be well in excess of the current design standards. So to the core of my point, if this boat has failed as badly as it has, what does this say about the majority of boats out there that were designed to barely meet this same standard, or worse yet, designed to barely meet some earlier standards which were less stringent than the current standard.



Lazerbrains said:


> What is nice about Bob's design is that it spreads the load out over a wide area - if this Bene had comparative area of backing to support the keel, it would not so likely have ripped away the fiberglass so easily as it did. Those backing plates aren't any wider than the keel.


But if you look at the photos of the internal structure of the 36.7 in the photo linked in Post 37, you can see that there is a very similar structure to the one shown for Francis Lee, only rendered in composite instead of steel and wood as was the structure on Francis Lee. In the case of the 36.7's there is a dense structural grid around the keel, that is integral with a grid that extend the length of the boat, and which also includes glassed in place longitudinal stringers in the hull. That combination would similarly spread the loads quite effectively in much the same way as Bob's design. My bigger concern is that this type of structure is absent in the majority of boats out there, so if this one failed so dramatically, what does it say about the boats produced to a lesser standard of care.

Jeff


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## Lazerbrains (Oct 25, 2015)

Jeff_H said:


> In the case of the 36.7's there is a dense structural grid around the keel, that is integral with a grid that extend the length of the boat, and which also includes glassed in place longitudinal stringers in the hull. That combination would similarly spread the loads quite effectively in much the same way as Bob's design.
> Jeff


Looking at the photos of the boat in question, it appears that the structural grid (which is hollow, not dense) in no way attaches to the keel - it provides structural form strength for the hull, yes, but does not attach in any way to those small backing plates - it simply tabs into the hull. Furthermore it can clearly be seen that the fiberglass bottom easily tore away from the one section of grid that was above the keel. As evidenced from the photos, it quite obviously did not "spread the loads quite effectively" as the hull broke quite cleanly at the small backing plates.


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## overbored (Oct 8, 2010)

the structural grid u channels are attached to the hull via a flange which is glued to the hull. the flange is part of the structure that is under the keel bolt backing plates, you can see in the pics the layers of hull, glue and structural grid if you what you are looking at.


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## JimsCAL (May 23, 2007)

This has been an interesting thread. Thanks Jeff for your lengthy and detailed posts. I think there is more to come out on this failure. I am an engineer (but NOT a structural one) and I really have never liked the small attachment area of these kinds of keels. Yes the grid may stiffen the hull in the area where the keel is attached, but it just seems to me that keel needs a much larger flange to spread the load where it attaches to the fiberglass hull.


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## Jeff_H (Feb 26, 2000)

JimsCAL said:


> This has been an interesting thread. Thanks Jeff for your lengthy and detailed posts. I think there is more to come out on this failure. I am an engineer (but NOT a structural one) and I really have never liked the small attachment area of these kinds of keels. Yes the grid may stiffen the hull in the area where the keel is attached, but it just seems to me that keel needs a much larger flange to spread the load where it attaches to the fiberglass hull.


Jim,

Thank you for the kind comment. I agree with you that I am not a huge fan of these high aspect, small footprint keels (or their tendency to stall out at slow speed). One of things about this particular design is that there is a flair to the top that spreads out the root footprint compares to many of the designs that follow it, and the center of the weight of the bulb is not a cantilever fore and aft.

Obviously as designers press the limits on high aspect keels this will only get worse. World Sailing has commissioned a major study on keel structure with a heavy focus on reducing failures. But it really does need to be looked at.

One of the bright spots is using 'cassette' type connections with these high aspect keels. These are essentially very heavily reinforced and completely integrated dagger board trunks that the end of the keel slots into. They are being used on race boats, and hopefully as high aspect keels move into the more mainstream, some form of cassette or other form of robust attachment method will be used.

Jeff


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## deniseO30 (Nov 27, 2006)

I want to toss this into the mix. 

Fin keel boats are not blue water boats. 

When a full Keel boat runs aground what happens? "Full Keel boat runs a ground" 

Same scene; fin keel, "boat ran a ground, lost keel"


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## hellosailor (Apr 11, 2006)

"Fin keel boats are not blue water boats. 
When a full Keel boat runs aground what happens?"

Okay, I think you're radically missing a point here. In "blue water" you are not going to run aground, unless your fin keel is many hundreds or thousands of feet deep.

You know, there are very few hard bits that just protrude unseen within six feet of the surface, unless you count Iceland and Hawaii and a few others where new rocks do sometimes climb up.

And yes, the bottom gets closer in some few areas of the Pacific and Carib, but then again, those are fairly well known shoals and reefs, and there's no reason a blue water boat should have a problem there. That's a pilot error problem, not the boat's fault.

If you want to take "doesn't mind groundings" as a criteria, then your blue water boat can't be a fin keel either. It needs to be bilge keels, plural, so it can park anywhere. (and good luck getting it back off that reef.)


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## deniseO30 (Nov 27, 2006)

I'm sure there are lots of beneteau sailboats on sale. And it is not a new news that they lose keels. 

Nope, boats also are lose their keels in the open oceans. some of the things weread and hear about make the ocean seem more full of obstructions and some of our harbors! 

But I do agree, just about everything can be blamed on the nut holding the wheel


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## JimsCAL (May 23, 2007)

deniseO30 said:


> Fin keel boats are not blue water boats.


There are plenty of well respected bluewater boats with fin keels. Consider the Bob Perry designed Passport 40, Passport 41 and Valiant 40. Are these race boats with deep bulb keels like the Bene 36.7 being discussed in this thread? No. But fin keels, not full keels, just the same.


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## deniseO30 (Nov 27, 2006)

I love how y'all get so worked up on this issue, although you're all glad it wasn't your boat.

I don't think I'd ever go "out there" without a full Keel under my feet but that's just my personal feeling which, I'm allowed to have.


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## hellosailor (Apr 11, 2006)

Denise-
Even if you were sailing a brick, with an integral full keel and steel hull, I suspect that if you ran it into a hard rock reef at seven knots, the mast and rigging would snap from the impact.
There's just no reason to design any typical boat to survive crashing into rock at hull speed. That would be like the DOT ordering car makers to build cars that can crash into highway abutments at highway speed, and still get back on the road with no harm to the cars or their occupants. 
It probably COULD be done, but I don't think you'd want to build, buy, or operate one. That boat was severely abused. I'm reminded of the Porsche service manager in "Risky Business", after the car is dragged out of the lake: i.e. "And who was the u-boat commander?!"


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## deniseO30 (Nov 27, 2006)

But that is what is happening! 80% of them were Clueless! I've saw the remarks that the boat went down with main sail covered headsail furled. obviously they were using it as a powerboat, what do Power boaters do? they go fast as possible oblivious to everything else. (Not all, but it seems like it)

Manufacturers are going to start losing a lot of boats to this upcoming generation, I'm subscribed on YouTube to a young Millennial couple that picked up a catamaran, launch day they didn't know and the marina assumed the plug was in the bottom, the boat filled up in nearly sunk in place. 

Time to start building bumper boats!


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## hellosailor (Apr 11, 2006)

"Manufacturers are going to start losing a lot of boats to this upcoming generation,"
Well, other than the question of whether there's a sales opportunity in building bumper boats...
I don't see a problem with upcoming customers sinking boats. It consumes the old boats, redirects disposable income into the boating industries, keeps the salvors and repair yards busy...All being good for business.
Now, in the short term, insurers are going to take a hit, if they were foolish enough to sell insurance to those folks. Either we'll all pay slightly higher rates, or they'll learn to lessen their exposure and, wait, don't they already refuse to pay claims based on "I forgot to put the drain plug in" ? 
Here's one First 36.7 less in the world, that incrementally raises the value of all the rest, and similar boats. And in six or eight months, that boat might be back on the market, with a patched up hull and some lucky newbie buying it cheap with a salvage title. (Ahem.)
I was on a friend's Olsen(sp?) 911 ages ago, when some nice man t-boned us with his Pearson. The "only" damage to us was a six inch chunk knocked out at the deck joint, but the insurer totalled out the boat. The impact had broken the bulkhead tabbing all over the boat. Hitting a hard rock reef...yeah, right, that'll buff out.


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## Lazerbrains (Oct 25, 2015)

hellosailor said:


> Denise-
> Even if you were sailing a brick, with an integral full keel and steel hull, I suspect that if you ran it into a hard rock reef at seven knots, the mast and rigging would snap from the impact.


You might be suprised. Interesting video here:


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## hellosailor (Apr 11, 2006)

All well and good, but hardly the same thing as ramming it into a solid rock reef, is it? Or did they do that later on in the show?

I've sailed on boats with bendy masts and boats with tree trunks. Some where the builder openly says "If you're gonna jump on the deck, of course you're going to have spider cracks" and those boats are built for speed--not victory dancing. Others you can whale on all day, but you're not going anyplace in two knots of wind.

My friend (who was old enough to know better!) went down to the garden store and loaded a batch (6? 10?) of bags of crushed rock in the trunk of his Honda, planning to make his wife happy in the garden. Woops, he broke the suspension. he couldn't understand, the car really had a load limit, and a trunk full of rocks exceeded it. Now, does that make Honda a bad car? Or, should the guy have known it was built to limits? (Which are also published in the owner's manual, but forget that.)

Beneteau? OK, so it isn't an icebreaker. There's no news here. You ram anything into a rock wall, and usually, that's because you WANT to break something. Quarterhorses, Clydesdales, mules, they all have their purposes.

Now that would make a funny video, someone trying to teach a Clydesdale to use a litter box.(G)


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## dinosdad (Nov 19, 2010)

Question for Jeff H. , do designers/engineers design today's boats to perform/survive any , I guess lack of a better phrase , crash tests? I mean is there a standard like automotive crash tests ? Or Perhaps that a boat should survive a keel to solid object at x speed? I've never heard of anything like that , but I'm a neophyte to boating . It does seem though that no matter how idiot proof they make something, society simply builds a better idiot ......


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## Minnewaska (Feb 21, 2010)

Not quite the same, Dino, but Yachting Monthly did a Crash Boat series, including everything from thru hull failures to holing the boat to capsize and gas explosions. You can find them all on YouTube. I recommend every boater watch them all. Beyond a great education in techniques for dealing with these, you’ll find that our boats are a bit more durable than these isolated incidents suggest. Certainly not bullet proof.


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## Lazerbrains (Oct 25, 2015)

hellosailor said:


> All well and good, but hardly the same thing as ramming it into a solid rock reef, is it? Or did they do that later on in the show?
> .(G)


If you watch the whole thing they repeatedly ram it into the solid rock wall at 6.5kts. I always found this video suprising to watch as well as the Yachting Monthly crash testsb Minnewaska mentioned.


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## Jeff_H (Feb 26, 2000)

dinosdad said:


> Question for Jeff H. , do designers/engineers design today's boats to perform/survive any , I guess lack of a better phrase , crash tests? I mean is there a standard like automotive crash tests ? Or Perhaps that a boat should survive a keel to solid object at x speed? I've never heard of anything like that , but I'm a neophyte to boating . It does seem though that no matter how idiot proof they make something, society simply builds a better idiot ......


These days, the boat design process has become much more sophisticated in terms of the engineering side. When I worked for a yacht designer in the early 1980's or designed boats myself, the calculations were done by hand and were simple static calculations done in house by the designer. The assumed loads were surrogate loadings which came out of various scantling rules and were assumed to be adequate. These loads were often back calculated out of wooden boat scantling systems. They only looked at simple bending and axial loads, with no attention to deflection, and only focused on the service loads of the boat (i.e. service loads are only the normal loads experienced by a boat underway with no concern for impact loads from grounding or hitting an object.)

The first scientific studies of the loads on a hull were done in the years after the Fastnet Disaster. The early results of those studies led to a huge jump the published magnitude of the loadings on a hull, rig and foils at some point in the late 1980's. Again, these new loadings were focused mainly on service loads and not impact loads, but one of the drivers of the increased loadings were several large scale failures where topsides were buckled after falling off of a wave, or hull to deck joints were sheered in a similar condition.

During the development of the standards in the EU Recreational Craft Directive (RCD), there was an effort to look at the various structural studies that were out there and evaluate the standards. These were the types of studies that could not be done before the advent of small fast computers, cheap digital sensors, and the kind of funding that something like the EU could bring to bear. To give you a good example of the type of things that they were doing, one of the RCD studies constructed a full sized race boat and inserted a free floating rigid frame into it so that all of the stresses and deflections could be measured. Digital accelerometers, inclinometers, wind instruments, knotmeters, strain gauges, and deflectometers were providing simultaneous input that was recorded on a computer over a period in which the boat was sailed and the data crunched so that they could pretty accurately develop a numerical understanding of the causes and structure effects of normal sailing due to wind and wave action. Other studies of the era looked the reduction in strength in fiberglass due to the fatigue that results from the the effects of flexure, and so on.

The net result was a further increase in the service loads that are used for design, requirements to reduce flex, higher quality control in the mixing of resin, placement of laminate and control of resin ratios.

But none of these studies or standards ever looked at the impact loads from striking an (almost) immovable object. The physics to evaluate that impact is pretty easy to calculate without a study, and developing the actual loading on various components, and adding a safety factor would also be a pretty easy calculation to do as well. But no matter how easy that calculation might be, except in rare cases. engineering for that kind of impact never has been a part of the design process, and nor is it done today.

Going back to the days of wooden boats, they were never engineered to withstand a hard grounding. In a hard grounding it was likely that frames would be damage, maybe the keel (timber at the centerline of the hull not the foil that we call a keel today) sprung(joints separated), planking cracked and seams opened.

Certainly early fiberglass boats with long keels were not designed for a hard impact grounding. I cite my family's less than 5 year old Pearson Vanguard as an example. In 1966, she hit a rock at less than 4 knots with the leading edge of the keel and jumped up and over the rock without fully stopping. The roughly 1/2" to 3/4" thick (it varied between the centerline and sides) fiberglass encapsulation of the ballast sheered through on impact and drove the ballast upward through the bilge membrane dislodging the water tank. That boat did not sink but was taking on water. It later did sink when driven onto rocks in a storm (broke free from a mooring with no one on board) and the ballast was lost through the bottom of the keel encapsulation. Similarly I saw a Luders 33 of that same era which had the edge of the encapsulation pierce the hull skin at the turn of the bilge after dropping on a rock in big waves. I have seen IOR era boats that have damaged the sump where the keel attaches in a hard grounding, a good example of that was the late, great Jon Eisberg's Chancy, which lost its keel (similar failure with the hull ripped out to the boat in this thread) after running hard aground on a sandy beach. And certainly this boat and the many images of similar failures splayed across the internet on a pretty broad range of boats demonstrates that this kind of catastrophic failure still can and does happen today.

But your question also raises a valid question....Should boats be designed to withstand a major collision or hard grounding with minimal damage? That is a hard question to answer. It would be pretty easy to design a bolt on keel boat for that kind of force, expensive but doable as evidenced by the videos of Dehlers hitting hard objects during the brief period that Dehlers were engineered for those kinds of major crashes. Its much harder to design an encapsulated keel for that same kind of impact since the impact is to the fiberglass portion of the boat. It can be done using a resilient vinylester resin (as used in military and motorcycle helmits) with kevlar reinforcing, and an energy asborbing core material that had a 'memory'. Similarly, few boats are designed for a major point load impact to the above or below waterline hull. It can be done in a similar manner to the keel encapsulation with resilient vinylester resin, kevlar reinforcing, and an energy asborbing core material.

But it isn't routinely done; Cores are rarely carried below the waterline, Kevlar is hard to work with, and harder still to repair. Vinylester has been brought into production boat building but is limited to less ducile formulations and is mostly used in exterior layups to eliminate blisters.

So that is the long answer and I am afraid, its not all that detailed either.

Jeff


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## Lazerbrains (Oct 25, 2015)

I have always liked this video of the Hobie 33 with its DROP KEEL repeatedly grounding into rocks at 6kts with no damage. Hobie 33's are lightweight race boats. Certainly keels can be engineered to take this type of impact. It obviously holds up much better than the Beneteau did.






As for the "long keel" comment - a Pearson Vanguard is hardly a good example. By your own admission, they were built with broken fiber cloth and brittle resin prone to cracking and breaking. Westsails, for example, have gone aground all over the world without damage - but they are built worlds better than a Vanguard. Build quality aside, a long keel has much more attachment area, and much less lever arm. I've never heard of a long keel snapping off like this Beneteau.


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## Jeff_H (Feb 26, 2000)

Lazerbrains said:


> I have always liked this video of the Hobie 33 with its DROP KEEL repeatedly grounding into rocks at 6kts with no damage. Hobie 33's are lightweight race boats. Certainly keels can be engineered to take this type of impact. It obviously holds up much better than the Beneteau did.
> 
> Hobie 33 Crash Test - YouTube
> 
> As for the "long keel" comment - a Pearson Vanguard is hardly a good example. By your own admission, they were built with broken fiber cloth and brittle resin prone to cracking and breaking. Westsails, for example, have gone aground all over the world without damage - but they are built worlds better than a Vanguard. Build quality aside, a long keel has much more attachment area, and much less lever arm. I've never heard of a long keel snapping off like this Beneteau.


The Hobie 33's are an example of the direction that I mentioned earlier that the high aspect keels are heading for their attachment. Typically daggerboards have a portion of the board that is up in the trunk that increases the lever arm resisting the moment from an impact as compared to the narrow bolting pattern on a keel root. This helps resist the transfer of side loads into the boat. It really does not help with a fore and aft impact, but that can be engineered around. This is also the structural concept of a 'cassette' attachment method, in which the head of the keel is inserted into what is effectively a dagger board trunk, and which is gaining popularity in the racing community and may filter into cruising boat designs. It is also one of the reasons that the boats that I design for myself are designed with daggerboards with a bulb rather than a fixed keel. 







[/URL]My Version- Proposed Accommodation plans R-4_Page_1 by jeff_halp[/IMG]

Navypointprofile by jeff_halp, on Flickr

I mentioned the Vanguard for several reasons. First, these were very typical production boats of that era, built with very much the same methods, materials, quality control, and engineering of the majority of production boats of that time (i.e. Columbia, Morgan, Islander, Ericson, Coronado, Irwin and so on) and I took the question to be about standards for production boats. But I also mentioned the Vanguard because it is a boat and an accident that I knew personally and in detail. I also mentioned the Allied built Luders 33. Allied was considered to be one of the better quality boat builders of this era. I mentioned the Luders 33 because it suffered damage that was similar in effect to the the damage on the Beneteau in this thread in that the entire turn of the bilge was delaminated in a hard grounding. Cooincidentally, Allied also built Jon Eisberg's Chance 30-30 which was designed in another era by another designer, but which had a near identical keel detachment due to a hull structure failure as is seen in the photos of the Beneteau.

Regarding your last point, no where do I say boats cannot be designed to withstand a hard grounding or a point impact. In fact in my earlier post I note that I believe that boats can be designed to withstand a hard grounding, is simple physics to calculate the loads, and mention one type of construction that has been shown to be superior in resisting high load, small area impact.

Nor do I say whether I believe that boats should or should not be designed to withstand a hard grounding or a collision with floating object. In reality, I am not sure that I have a clear universal opinion on that. I think that boats making long passages need to be robustly constructed to withstand collisions and hard grounds with minimal damage and to be repairable should the hull be breached (which is why I am opposed to boats with full liners). But I am not sure that is the correct standard for coastal cruisers or race boats.

The point that I was trying to make in response to the question that was asked is that except for a limited number of boats out there, the vast majority of boats that we all sail were not designed to withstand either a hard grounding or point impact without incurring serious damage. My other point is that even if it is agreed that boats should be designed to withstand a hard grounding or point impact without major damage, then the current standards are inadequate to provide that protection. At this point, the most stringent standards for small sailing craft is the RCD, and the RCD does not establish construction standards that would prevent the kind of damage that occurred on the Beneteau in question. In fact, as documented in the link that I provided earlier, internal structure of the keel was 7.96 stronger than required under the current standards. If in the end, it is agreed that a boat should stand up to that kind of a hard collision without damage than those standards need to be so altered to assure that.

Respectfully,
Jeff


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## Lazerbrains (Oct 25, 2015)

Jeff, I like that design. Neat detail for the life-raft storage.


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## hellosailor (Apr 11, 2006)

If a boat is designed and built to be "crash resistant", it will of necessity be built more heavily (slow) and more expensive than the competition. And there goes the mass market, down the drain.

If this boat costs 1% more than that boat and more 1% slower as well? Folks are gonna buy the cheaper faster boat. "But this is more rugged!" only interests a small niche of the market. I don't think that tail can wag that dog.

"Honest, honey, I don't know how I got that tatoo!"
Ahuh, and that rock was never seen, reported, or charted before. What boat buyer is going to concede that *they* are not able to avoid rocks?


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## Lazerbrains (Oct 25, 2015)

Hellosailor - look up the specs for the Hobie33 for the video I posted above. Very fast and lightweight boat, yet survives repeated grounding of the keel into the rocks - so it can be done. (As a matter of fact, a Hobie33 last year was beating most of the larger boats on actual time in the Transpac). Strong doesn't mean heavy.


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## Jeff_H (Feb 26, 2000)

hellosailor said:


> If a boat is designed and built to be "crash resistant", it will of necessity be built more heavily (slow) and more expensive than the competition. And there goes the mass market, down the drain.
> 
> If this boat costs 1% more than that boat and more 1% slower as well? Folks are gonna buy the cheaper faster boat. "But this is more rugged!" only interests a small niche of the market. I don't think that tail can wag that dog.


If sailors were willing to pay more and give up performance for safety then Etap would be outselling Beneteau, Hunter, Hanse, and Catalina. On the flip side, Boston Whaler still thrives, and the big car makers swore no one would buy vehicles if they were required to be safer, get better gas mileage, and pollute less. Somehow most of us got used to paying the cost to meet these standards.

Jeff


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## hellosailor (Apr 11, 2006)

Lazer-
I would suggest that regardless of what the Hobie33 does, the boat could be faster and lighter and less expensive if it was NOT built to survive repeated hard rock impacts. (And the keel-killer was not simply a gentle grounding, but a severe impact.)

Then there's the question of comparable price. When similarly equipped to other boats of a similar speed and capacity, trim quality, etc., what's the cost penalty to the Hobie? That's a hard one to compare, I suspect, given the variations in boats.

Good design, a fast hull, seakindliness, balanced sails...as one respected nautical architect said of one of his boats "I got lucky with that one." 3D CAD helps tremendously with analyzing the never-ending effects of heel and other variables, but when all is said and done, strength costs more than weakness. A really good designer and builder may be able to hide that in the overall cost, but it still has to be there. Whether it means "three more layers of cloth" or whatever.
The cassette daggerboard design may have some inherent advantage over a fixed keel, but then there's the tradeoff of a trunk in the middle of the cabin, isn't there? Unless you keep it short enough to hide in the salon table. And then, you've still got to get in there and clean out the trunk from time to time, I'd expect.


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## hellosailor (Apr 11, 2006)

Good points, Jeff.

"If sailors were willing to pay more and give up performance for safety then Etap would be outselling...On the flip side, Boston Whaler still thrives,"
I think Boston Whaler fills a certain market segment where the price of five gallons of expanding foam can be absorbed in the product, and it makes a nice incidental selling point. ("Honey, this one is safer, the kids can't sink")

Cars though are a different story. Very few seat belts were ever sold as options. Heck, very few cars had the optional passenger-side mirror, even when that was a $25 option of a $5000 car. Folks just didn't want to spend it. Those safety improvements were *mandated* and car buyers had no choice about paying for them.

And while I can attest that in some circumstances ABS brakes work peachy keen, and I find a grim irony in Takata airbag recalls (Would you buy a car with eleven explosive devices in the passenger cabin, built bu a former Axis power?), I'd really like to see cheaper more reliable cars that didn't have all those "safety" complications. Despite the fact that personally, I've always used the seat belts, even when I wasn't required to.


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## CaptainHyperjoe (Jul 7, 2012)

Jeff_H said:


> That is just plain silly. Where did you come up with that idea? It makes absolutely no sense at all and bears no resemblance to reality. When dropping off a wave while heeled the side force on a keel and the sudden deacceleration can result in a tensile load on the bolts that can approach a range that is 20-40 times the weight of the keel. Or to look at this from another approach, each of those bolts has roughly a 50,000- 55,000 lb tensile strength and the keel only weighs 3748 lbs that is something in the range of 14 times the weight of the keel for each bolt.
> 
> 
> 
> ...


I believe this boat ran into a whale. This keel was pushed off with continual pressure and force. This was not a keel failure but an accident of great force.


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## MastUndSchotbruch (Nov 26, 2010)

CaptainHyperjoe said:


> I believe this boat ran into a whale. This keel was pushed off with continual pressure and force. This was not a keel failure but an accident of great force.


A whale in the Great Lakes???


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## redgar (8 mo ago)

MastUndSchotbruch said:


> A whale in the Great Lakes???


C'mon, man! You've got to keep up with the times. There was a great article about whale watching on the Great Lakes published in early April 2016 in the Great Lakes Gazette:

WHALE WATCHING ON THE GREAT LAKES​







Whale Watching on the Great Lakes


SCROLL DOWN FOR AN EXCITING ANNOUNCEMENT! While the possibility of Asian carp invading the Great Lakes makes news, another phenomenon of the inland seas receives little attention: the presence of f…



www.greatlakesgazette.com




There is documented evidence of this migration going back to the 1800's!








​

~~ Red


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## MastUndSchotbruch (Nov 26, 2010)

redgar said:


> C'mon, man! You've got to keep up with the times. There was a great article about whale watching on the Great Lakes published in early April 2016 in the Great Lakes Gazette:
> 
> WHALE WATCHING ON THE GREAT LAKES​
> 
> ...


You nearly had me there, was hoping for a picture showing a whale jumping up Niagara Falls -- salmon style!

Until I read the last line of the piece


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## boatpoker (Jul 21, 2008)

I have to wonder if the grid was properly bonded to the hull ?
I was hired to determine why the V-berth door would not close after a Wednesday night race on 
this boat. It'll be easier to understand if you read these in order ... got some cool photos too


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## redgar (8 mo ago)

Wow! That is scary... Maybe someone at the factory was having a bad day? Lack of supervision and oversight?

Lawyers wanna know...


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## jeremiahblatz (Sep 23, 2013)

Well, since this old thread is back, I'll add that the folks at Expedition Evans on YouTube bought a keel-grid Beneteau that had run aground. I haven't watched their grid repair to the end, but in their boat, the glue bond between the grid and the hull was pretty tenuous in some areas. I'm not sure if the design accounted for imperfect gluing or not. 

Also, based on the old photos and what we've learned about Beneteaus few years, I wonder if the boat in this thread hadn't hit a rock several times before. Id the grid's internal structure starts to delaminate, it might look fine, but subsequent normal loads (from waves etc) might increase the level of delamination. Then, one fine day you hit another rock and *bam* the hull and grid just zipper open around the keel boats and the keel falls straight down.

One thing I suspect about this is that the keel grid design's fault is that _it can be damaged, but still look fine_. If the structure of a keel attachment ins compromised, one would hope that it would be very obvious, but it looks like the Benes can hide that damage.


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## JAREK22 (4 mo ago)

redgar said:


> Wow! That is scary... Maybe someone at the factory was having a bad day? Lack of supervision and oversight?
> 
> Lawyers wanna know...


Hm, this is a fairly complex issue. First we need to differentiate between structural and non structural liners I happen to have bought a Beneteau that has been grounded. Large parts of the internal, nice gelcoated liner were cut out to access the damage and judging by their thickness were not intended to be structural. They only make the interior of the cabin look nice. This interior liner is put into the hull with beeads of adhesive that are supposed to bond it to the outer shell of the hull. Invariably, there are areas where the bond less than perfect. But...this is not a structural liner. The liner thickness is only around 3/16", or even less, in areas where people do not walk. The structural layup of the hull, on the other hand, from the outside most fibre to the bottom of the keel bolt washer is around 1.5", so around 8 times thicker. In the boat in the three attached surveys, the inner liner layup seems to be thicker, but the designer certainly did not rely on the putty for the structural strength of the hull.


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