Bavaria Keel problem - Who'd test their boat like this?

[savageseadog]

Re: Bavaria Keel problem - Who\'d test their boat like this?

What a depressing outlook. Do you really think there have been no technical advances in the last 100 years since that "rule of thumb" was used? Have there not been enough boats built to different design standards then used and tested at sea to demonstrate that the standards work?

Looking at modern computer designed boats they don't get it right all the time.

 

[Tranona]

Re: Bavaria Keel problem - Who\'d test their boat like this?

Looking at modern computer designed boats they don't get it right all the time.

Just the same as the old style builders!

Anyway if you know anything about the ABS/ISO standards for keel attachments you will know that there is a huge margin of safety in the bolts - and it is worked out scientifically rather than some old bloke sucking on his pipe and saying "I reckon....."

 

[savageseadog]

Re: Bavaria Keel problem - Who\'d test their boat like this?

Just the same as the old style builders!

Anyway if you know anything about the ABS/ISO standards for keel attachments you will know that there is a huge margin of safety in the bolts - and it is worked out scientifically rather than some old bloke sucking on his pipe and saying "I reckon....."

So what standard did the Bavarias adhere to then? Where was the margin of safety? There was Cheeki Rafiki, I've seen newish racing yachts with catastrophic damage to the keel and attachment due to relatively minor groundings. I know of a relatively recently built racing yacht that had to have the keel floors extensively re-engineered. I don't think keels and attachment are an exact science. My own belief is that forces in the keel attachment area are far higher than is generally thought by many in afloat conditions.

 

[mainsail1]

Re: Bavaria Keel problem - Who\'d test their boat like this?

I agree that the forces on a keel attachment area are far higher than generally thought by mass production builders, hence the substantial number of keel failures, many of which do not get reported to the public as no-one died, but ask any yacht surveyor.
The evidence of many keel failures shows that the 'standards' don't work and for builders to hide behind the smoke screen of 'must have run aground' is disingenuous.

 

[Tranona]

Re: Bavaria Keel problem - Who\'d test their boat like this?

So what standard did the Bavarias adhere to then? Where was the margin of safety? There was Cheeki Rafiki, I've seen newish racing yachts with catastrophic damage to the keel and attachment due to relatively minor groundings. I know of a relatively recently built racing yacht that had to have the keel floors extensively re-engineered. I don't think keels and attachment are an exact science. My own belief is that forces in the keel attachment area are far higher than is generally thought by many in afloat conditions.

The question was specifically about keel bolts, and in neither of the instances you quote did the keel bolts fail because they were not strong enough.

Anybody would think that structural failures are somehow new and the result of "modern" design, clearly ignoring all the failures in the past. The number of failures is tiny in relation to the number of boats in use, but some people take those failures to indicate a massive problem.

While it is useful to look in detail at the rare failures as there is always something to learn, but doing so ignores all those tens of thousands of boats where there are no failures. Invariably close investigation reveals a cause that is not typical, but specific to a particular set of circumstances, whether they be related to design, construction or use that cannot be generalised or transferred to other situations.

 

[savageseadog]

Re: Bavaria Keel problem - Who\'d test their boat like this?

The question was specifically about keel bolts, and in neither of the instances you quote did the keel bolts fail because they were not strong enough.

Anybody would think that structural failures are somehow new and the result of "modern" design, clearly ignoring all the failures in the past. The number of failures is tiny in relation to the number of boats in use, but some people take those failures to indicate a massive problem.

While it is useful to look in detail at the rare failures as there is always something to learn, but doing so ignores all those tens of thousands of boats where there are no failures. Invariably close investigation reveals a cause that is not typical, but specific to a particular set of circumstances, whether they be related to design, construction or use that cannot be generalised or transferred to other situations.

No
The question wasn't about keel bolts, it was about structural failure of keel/keel attachment structures

 

[Tranona]

Re: Bavaria Keel problem - Who\'d test their boat like this?

So what standard did the Bavarias adhere to then? Where was the margin of safety? There was Cheeki Rafiki, I've seen newish racing yachts with catastrophic damage to the keel and attachment due to relatively minor groundings. I know of a relatively recently built racing yacht that had to have the keel floors extensively re-engineered. I don't think keels and attachment are an exact science. My own belief is that forces in the keel attachment area are far higher than is generally thought by many in afloat conditions.

All Bavarias (and all other production boats) comply with the RCD and therefore the relevant ISO. Racing boats do not have to comply and it is true that many are not strongly enough built. Most of the reported keel failures have been on racing boats. Trying to relate that to production cruising boats is like trying to say that a failure on a rally Focus means that things will break on a Fiesta. the failure of CR was a one off - and the bolts did not necessarily fail, although without the boat to inspect it is unclear how the failure actually occurred.

The Bavaria that caused the fuss 10 years ago was one particular model that was unrelated to the mass production boats they also sold at the time. This does not mean that other individual boats do not experience problems with keels, but it is not systemic - that is it occurs on some boats and not others, and is not confined to one builder. There is a usually a sound explanation for the problem, invariably involving a grounding, but as so little data is recorded - boats are just fixed, it is difficult to collect reliable statistical evidence.

You have to remember that if this conversation was taking place 60 years ago the "faults" under discussion would be corroded keels bolts, leaky garboards, broken ribs loose floors - etc. In other words the same issues but with different materials and construction. Not only that, but those issues were almost universal across all types of boats - just that they happened earlier in life in racing boats for the same reasons - inadequate structures combined with hard sailing (and bumping the bottom frequently).

 

[Tranona]

Re: Bavaria Keel problem - Who\'d test their boat like this?

No
The question wasn't about keel bolts, it was about structural failure of keel/keel attachment structures

While the original thread was wider, my observations about "rules of thumb" was prompted by the reference in post#28 to a way of sizing keels bolts that was over 100 years old and largely irrelevant to today's boats (as well as not being supported by any calculations).

 

[lpdsn]

Re: Bavaria Keel problem - Who\'d test their boat like this?

While the original thread was wider, my observations about "rules of thumb" was prompted by the reference in post#28 to a way of sizing keels bolts that was over 100 years old and largely irrelevant to today's boats (as well as not being supported by any calculations).

Forum Rules remember. Calculations are modern rubbish. They'll never catch on.

 

[Tranona]

Re: Bavaria Keel problem - Who\'d test their boat like this?

Forum Rules remember. Calculations are modern rubbish. They'll never catch on.

Sorry sir. Maybe the government is wasting money trying to improve education in maths and the sciences if the forum collectively thinks it is all rubbish!

 

[lpdsn]

Re: Bavaria Keel problem - Who\'d test their boat like this?

Sorry sir. Maybe the government is wasting money trying to improve education in maths and the sciences if the forum collectively thinks it is all rubbish!

Ah, but they're not spending it on pensioners.

 

[savageseadog]

Re: Bavaria Keel problem - Who\'d test their boat like this?

Sorry sir. Maybe the government is wasting money trying to improve education in maths and the sciences if the forum collectively thinks it is all rubbish!

You're missing the point. If keel "calculation"and design were a completely understood science then why do modern keels detach and become loose?

 

[lpdsn]

Re: Bavaria Keel problem - Who\'d test their boat like this?

You're missing the point. If keel "calculation"and design were a completely understood science then why do modern keels detach and become loose?

Which ones do you have in mind?

Hooligan V is probably the closest where the designer pushed the safety factor a bit below what others would do, but fundamentally it failed because of a very ill-conceived modification during fabrication.

Cheeki Rafiki was put down by many as simply operator error, although I still hold that a significant proportion of the blame lies on the builders for inadequate design for maintainability. No indications it was an inadequate strength calculation though.

They've been some where the layup was too thin. There was someone jailed in Oz for one of them. IIRC, that was a case of no calcs rather than wrong calcs.

Canting Keels on Volvo boats etc - well to be honest they're really still experimental designs pushing the limits and in a way failures are at least included in the planning and seem routinely survivable.

Westerly Centaur bilge keels. OK, you might have a point there.

 

[Resolution]

Re: Bavaria Keel problem - Who\'d test their boat like this?

You're missing the point. If keel "calculation"and design were a completely understood science then why do modern keels detach and become loose?

It's the same science as in effect in air travel, where planes break up and crash.









Once in a very blue moon.

 

[dom]

Re: Bavaria Keel problem - Who\'d test their boat like this?

Which ones do you have in mind?

Hooligan V is probably the closest where the designer pushed the safety factor a bit below what others would do, but fundamentally it failed because of a very ill-conceived modification during fabrication.

Cheeki Rafiki was put down by many as simply operator error, although I still hold that a significant proportion of the blame lies on the builders for inadequate design for maintainability. No indications it was an inadequate strength calculation though.

They've been some where the layup was too thin. There was someone jailed in Oz for one of them. IIRC, that was a case of no calcs rather than wrong calcs.

Canting Keels on Volvo boats etc - well to be honest they're really still experimental designs pushing the limits and in a way failures are at least included in the planning and seem routinely survivable.

And don't forget the Oyster 825 Pollina Star III who lost her keel in benign conditions (I understand Oyster eventually accepted it was a design/construction problem). Then there was the Halberg Rassy de-keeled by a whale earlier this year, Rambler 100's keel which fell off in Aug 2011 Fastnet and didn't some old Westerly's suffer from wobbly keels?

There we have it; technology improves, some folk push the envelope, we all learn, boat design improves and with time the old designs become obsolete and die out.

As Resolution points out, the same process can be seen in aerospace; "Oh the aching nostalgia of a DC3!", true, but the A320neo and 737 MAX's are better. It's funy how pilots can recognise this, jump at the chance of flying a DC3, but still choose a modern aircraft for a fully-booked flight on a grottty day.

Us yotties, eh?

 

[savageseadog]

Re: Bavaria Keel problem - Who\'d test their boat like this?

It's the same science as in effect in air travel, where planes break up and crash.









Once in a very blue moon.

There's a great deal more analysis of failures and a lot more resources to fund research and development in aircraft design. Investigations of most structural failures become public knowledge.

 

[lpdsn]

Re: Bavaria Keel problem - Who\'d test their boat like this?

There's a great deal more analysis of failures and a lot more resources to fund research and development in aircraft design. Investigations of most structural failures become public knowledge.

But much of the same information is used by yacht designers.

You'd be pretty miffed if your rudder fell off if you used full lock one way then the other but you wouldn't want to try it on some popular commercial airliners.

 

[lpdsn]

Re: Bavaria Keel problem - Who\'d test their boat like this?

Then there was the Halberg Rassy de-keeled by a whale earlier this year...

Although to be fair to HR most airliners would come out of it quite badly if they hit a whale.

 

[TangaraToo]

Re: Bavaria Keel problem - Who\'d test their boat like this?

But much of the same information is used by yacht designers.

You'd be pretty miffed if your rudder fell off if you used full lock one way then the other but you wouldn't want to try it on some popular commercial airliners.

Also fair to say there is no restriction on amount of rudder used as speed increases the force applied to the control as there is with aircraft.

 

[dom]

Re: Bavaria Keel problem - Who\'d test their boat like this?

Although to be fair to HR most airliners would come out of it quite badly if they hit a whale.

No empirical evidence (I think) but suspect you're right!! ...same applies to the bottom-strikes in CR's case, overly aggressive design in Rambler's case and poor QC on Hooligan's keel. In the same way poor QC was to blame for the BA windscreen that popped out a few years back, and a combination of poor design and poor QC for the 1954 Comet crash.

I feel suddenly overwhelmed by a sense of deja vu: gosh it was only a couple of months back!
http://www.ybw.com/forums/showthread.php?483050-Keel-Integrity-Thread&p=6140528