Loss of yacht - lessons to learn

[Twister_Ken]

I was asking if the majority of builders using tray/frame construction went with GRP over ferrous metal.

The majority of builders use one form or another or GRP engineering to beef-up the keel attachment area.

 

[Mark-1]

The majority of builders use one form or another or GRP engineering to beef-up the keel attachment area.

That's what I suspected.

I'm now really keen to know the correct generic marine engineering term for tray/frame construction. I smiled at "beef up the keel area" but it doesn't acknowledge that the frame/tray also supports the shrouds.

There's a book on my shelf called something like "Desirable features in Ocean Cruising Boats" which should provide all this that but instead it's a bit like listening to a drunk pensioner on a bar stool endlessly listing why his Hilliard is the only viable design rather than a serious book examining the pros and cons of different designs.

 

[maby]

Before we get too worked up over AWB design practices, it is worth remembering that there are a lot of them out there and structural failure is pretty rare. Whether or not they are appropriate for blue water crossings is a valid question - mine is never likely to be more than 100 miles off-shore and anything over a force 6 or 2m waves would ensure that it was safely moored in some protected harbour.

 

[doug748]

There is an interesting overview of the of the new Salona 36, here:

http://www.salonayachts.nl/files/new Salona35.pdf

The skeletal view of the stainless steel grid (P5) looks, on the face of it, a strong and considered form of construction.

 

[snooks]

Some mouldings/reinforcement are "inner tray" moulding so the lattice work is all connected in one "tray" this is then bonded to the hull using squidgy GRP paste which is strong - so I'm told. Some mfg also laminate this tray in position, others don't. Sometimes the central panels in-between the stringers are cut out, this is makes the tray more of a grid, other times they aren't it varies so much between mfgs.

Basic bit...feel free to skip...If the stingers are all attached together they are known as a grid if they are individual they are either longitudinal (running for/aft) or athwart ships (across the boat from port to stn), usually in a "top hat" section, shaped like the section of top hat if you cut them in a section, with the brim of the hat glued/laminated to the hull.

Some laminate wooden or foam stringers into the hull as a second process.

Some lay up the hull dry with the foam stringers in place and covered with woven rovings and then vacuum infuse the whole hull in one go.

Some like Arcona and Salona IIRC use a metal grid, galvanised steel in the former stainless in the latter.

Edit: looks like I did remember correctly - Thanks Doug

 

[flaming]

Before we get too worked up over AWB design practices, it is worth remembering that there are a lot of them out there and structural failure is pretty rare. Whether or not they are appropriate for blue water crossings is a valid question - mine is never likely to be more than 100 miles off-shore and anything over a force 6 or 2m waves would ensure that it was safely moored in some protected harbour.

This is a very good point.

There are a lot of 40.7s out there racing hard, and quite a few that do the ARC, Caribean circuit and then transit home every year. A number of 40.7s finished the 2007 Fastnet in very tough conditions.

The fact that one loses a keel in unexplained circumstances after many years in hard charter use does not, necessarily, make it a badly designed or built boat. If it was then we would have been talking about 40.7 keels dropping off for many years now.

What I, and others who race hard on boats whose underwater profile looks very similar, want to know is this.

Do these boats have a lifespan after which we should expect the occurrence of issues such as these to be more common? And if so, how do we know when we're reaching it?

In the Elan we have had a few heavy groundings, including one that was a full stop from about 8 knots. (I wasn't on board...) After every such incident the keel has been inspected professionally, and if anything worrying is found is dropped so that the hull join can be inspected and if necessary beefed up. For this reason I am very confident that our keel is not going to fall off.

However, dropping the keel is not exactly a cheap process. How many owners are going to think "I'm sure it's fine..." when the other option is a hefty yard bill to, in all probability, be told that it was all fine anyway?

 

[alant]

Before we get too worked up over AWB design practices, it is worth remembering that there are a lot of them out there and structural failure is pretty rare. Whether or not they are appropriate for blue water crossings is a valid question - mine is never likely to be more than 100 miles off-shore and anything over a force 6 or 2m waves would ensure that it was safely moored in some protected harbour.

How does that help, if the keel falls off?

 

[alant]

This is a very good point.

There are a lot of 40.7s out there racing hard, and quite a few that do the ARC, Caribean circuit and then transit home every year. A number of 40.7s finished the 2007 Fastnet in very tough conditions.

The fact that one loses a keel in unexplained circumstances after many years in hard charter use does not, necessarily, make it a badly designed or built boat. If it was then we would have been talking about 40.7 keels dropping off for many years now.

What I, and others who race hard on boats whose underwater profile looks very similar, want to know is this.

Do these boats have a lifespan after which we should expect the occurrence of issues such as these to be more common? And if so, how do we know when we're reaching it?

In the Elan we have had a few heavy groundings, including one that was a full stop from about 8 knots. (I wasn't on board...) After every such incident the keel has been inspected professionally, and if anything worrying is found is dropped so that the hull join can be inspected and if necessary beefed up. For this reason I am very confident that our keel is not going to fall off.

However, dropping the keel is not exactly a cheap process. How many owners are going to think "I'm sure it's fine..." when the other option is a hefty yard bill to, in all probability, be told that it was all fine anyway?

Prior to this incident, I would be more concerned, about the bloody great cockpit on a 40.7, if I was bringing it back accross.

 

[Mark-1]

mine is never likely to be more than 100 miles off-shore

How does that help, if the keel falls off?

Within helicopter range, less likely to be out in bad weather in the first place if it's forecast.

 

[maby]

How does that help, if the keel falls off?

It does not specifically help if the keel falls off, but the structural failure is not the only area where there are lessons to be learned from the CR. It seems clear that at least two of the crew survived the initial incident but were not rescued, at least in part because they were unable to deploy the liferaft. We are always likely to be in range of SAR helicopters, so it may be the case that for us, at least, investing a lot of money in improving the liferaft provision of the boat may be less cost effective than upgrading our lifejackets and purchasing proper survival suits. For a boat crossing open ocean, this may not be the case.

 

[TimBennet]

What I, and others who race hard on boats whose underwater profile looks very similar, want to know is this.

Do these boats have a lifespan after which we should expect the occurrence of issues such as these to be more common? And if so, how do we know when we're reaching it?

I think this is an area that is going to receive an increasing amount of attention in the next few years. We have a lot of data about the failure of GRP and stainless after repeated load cycles, but little about the their behaviour when formed into structures.

I really hope one outcome of the CR incident, is that the MAIB or some university will try to identify other 40.7 with similar service histories, and take a good look at their structures with every investigative gizmo at their disposal. In aviation crash investigations, it's often examination of sister aeroplanes that gives the clues as to why one failed. With the 40.7 being a popular production boat, we have a perfect opportunity to do the same with their structures.

 

[Twister_Ken]

I really hope one outcome of the CR incident, is that the MAIB or some university will try to identify other 40.7 with similar service histories, and take a good look at their structures with every investigative gizmo at their disposal. In aviation crash investigations, it's often examination of sister aeroplanes that gives the clues as to why one failed. With the 40.7 being a popular production boat, we have a perfect opportunity to do the same with their structures.

I guess by now Beneteau has briefed its lawyers to the hilt.

 

[Mark-1]

I think this is an area that is going to receive an increasing amount of attention in the next few years. We have a lot of data about the failure of GRP and stainless after repeated load cycles, but little about the their behaviour when formed into structures.

I really hope one outcome of the CR incident, is that the MAIB or some university will try to identify other 40.7 with similar service histories, and take a good look at their structures with every investigative gizmo at their disposal. In aviation crash investigations, it's often examination of sister aeroplanes that gives the clues as to why one failed. With the 40.7 being a popular production boat, we have a perfect opportunity to do the same with their structures.

Can't fault any of that but I have a horrible feeling that all we'd learn is that deep keels with a heavy bulb and tiny foot print are highly desirable in terms of sailing performance and highly undesirable in terms of remaining attached to the boat in the long term, or after impact. Which is already known.

Maybe I'm wrong and Beneteau are doing something different to everyone else or maybe a lesson will be learned which applies to a large number of fin keelers.

 

[maby]

Can't fault any of that but I have a horrible feeling that all we'd learn is that deep keels with a heavy bulb and tiny foot print are highly desirable in terms of sailing performance and highly undesirable in terms of remaining attached to the boat in the long term, or after impact. Which is already known.

Maybe I'm wrong and Beneteau are doing something different to everyone else or maybe a lesson will be learned which applies to a large number of fin keelers.

Bavaria, Jeanneau and Beneteau have all suffered a similar small number of failures in recent years - probably attributable to impacts. The Bavaria and the CR both capsized with loss of life, but the Jeanneau continued to sail for weeks afterwards and the loss of keel was only discovered as a result of reports of disappointing performance - so it may be the case that the architypal fat-bummed modern AWB is less vulnerable to this mode of failure in normal use - the Bavaria and CR were both examples of lightweight racing AWBs.

 

[Mark-1]

Bavaria, Jeanneau and Beneteau have all suffered a similar small number of failures in recent years - probably attributable to impacts. The Bavaria and the CR both capsized with loss of life, but the Jeanneau continued to sail for weeks afterwards and the loss of keel was only discovered as a result of reports of disappointing performance - so it may be the case that the architypal fat-bummed modern AWB is less vulnerable to this mode of failure in normal use - the Bavaria and CR were both examples of lightweight racing AWBs.

It's a digression but I also wonder if using manufacturer brand names to categorize vessels that have suffered structural issues is too clumsy. I think categorizing boats by design type would be far more useful in this context.

So perhaps we could lump Maxfun 35 (Hooligan 5), Bavaria 35 and First 40.7 into a “deep bulb keel” category.

“Architypal fat-bummed modern AWB” is a good category name. I'm not aware of an Architypal fat-bummed modern AWB that's lost a keel for reasons other than poor maintainance or obvious impact damage.

I can't be bothered to make up any more category names but you get my drift.

 

[TimBennet]

So perhaps we could lump Maxfun 35 (Hooligan V), Bavaria 35 and First 40.7 into a “deep bulb keel” category.

Even that categorisation is meaningless: There is very little in common between the fabricated steel fin on the Maxfun and the keel on the 40.7 - neither material, construction method or attachment to hull. Although we know very little about the failure on CR, it's a fair guess it wasn't due to the same trail of shortcomings we saw with Hooligan V.

 

[Mark-1]

Even that categorisation is meaningless: There is very little in common between the fabricated steel fin on the Maxfun and the keel on the 40.7 - neither material, construction method or attachment to hull. Although we know very little about the failure on CR, it's a fair guess it wasn't due to the same trail of shortcomings we saw with Hooligan V.

I chose that classification because the thing these boats do have in common is the difficult job of attaching a deep bulb keel with a small footprint.

At first glance it seems a better way to group than manufacturer brand but I'm sure someone who knows a bit about boat design will suggest something better.

 

[Neil_Y]

I chose that classification because the thing these boats do have in common is the difficult job of attaching a deep bulb keel with a small footprint.

At first glance it seems a better way to group than manufacturer brand but I'm sure someone who knows a bit about boat design will suggest something better.

Ther are other variations in keel attatchement deisgn...My Bavaria had this design, which makes quite a bit of sense.