The Elements of Boat Strength: For Builders, Designers, and Owners [Archive]

Willallison

10-25-2009, 08:06 PM

I agree that Elements is a great book. I've used it and continue to do so. The scantlings it provides do err on the conservative side, but are none the worse for doing so. Structures built to the derived scantlings will, in my experience, be slightly 'heavier' than those derived from other common scantling rules - like ABS.
This book won't necessarily teach you the engineering that goes into the design of a well built boat, but everything in it is based on sound engineering principles.
There are compromises that must be accepted in using it, of course. The number of bulkheads and their approximate spacing, for instance, is governed. If this fits in with your design anyway, then there's no problem. If not, you will have to look elsewhere.

Ad Hoc

10-25-2009, 08:13 PM

Gonzo
I've heard of Gerr, his prop book is excellent. But not aware of any others by him.
The reason being a mix of tonyr's and Paul K's reply.

For tonyr, one assumes he is not a formally trained naval architect? He has a passion and/or interest in boats. Takes it to the next level and draws/designs boats. Without formal uni training what guidance is there for 'designers/draughtsman' who wish to draw up structure for build.....seems like this is a widely used book for guidance.

The reason why I'm not aware of the book is because i design from first principles and/or Class rules. Which Paul is eluding to. I estimate/establish the loads and then design a structure to suit the loads. The rules of thumb i use are based upon all the as-built designs i have designed which have all passed Class and been running successfully for years. BUT, the rule of thumb is just to establish the rough weights/structure in the preliminary design stage, to ensure the design works before giving it to the client. I'm not wasting endless time on details if the project doesn't go ahead. Proper analsyis/design is required post contract.

So perhaps you should reiterate and say it is like a someone who listens to music not knowing the Beatles, rather than a musician who knows them and how to play every chord of their music.

frank smith

10-25-2009, 08:26 PM

This is am informative site on construction

http://www.yachtsurvey.com/

If sometimes you are made to feel you are not up to it , read about some of the professional screw ups . I study all I can of the way good boats are built.
Read , and look at boats, go tour some boat manufacturers .

Paul Kotzebue

10-25-2009, 08:36 PM

This book won't necessarily teach you the engineering that goes into the design of a well built boat, but everything in it is based on sound engineering principles.

Does Gerr describe how his methods are derived from sound engineering principles? I have not read the book, but I might have an interest in it if Gerr is able to relate his methods directly to first principles.

daiquiri

10-25-2009, 08:54 PM

Does Gerr describe how his methods are derived from sound engineering principles? I have not read the book, but I might have an interest in it if Gerr is able to relate his methods directly to first principles.

I agree with you. Gerr's book doesn't contain any scientifically argumented explanation about how did he obtain his scantling equations and graphs. I have that book and did use it on several occasions, and in effect (as I stated in a similar thread here, plenty of months ago) all of us who are using it are actually relying on Gerr's word and professionalism.
On the other hand, each time we use prepackaged scantling equations provided by some classification society we do exactly the same...

Paul Kotzebue

10-25-2009, 09:21 PM

On the other hand, each time we use prepackaged scantling equations provided by some classification society we do exactly the same...

I do not agree. Class society rules such as ABS and Lloyd's are derived from first principles and do not represent one man's opinion. Shell plating thickness is usually based on flat panel theory and stiffeners are based on beam theory. The "prepackaged" scantling equations used by ABS and Lloyd's can be found in engineering textbooks not related to boat construction, and are the accepted means of calculating stresses from first principles.

Modern class society rules using design loads, accepted engineering stress formulas, and accepted engineering failure modes should not be confused with cookbook scantling rules. They are not the same thing.

Ad Hoc

10-25-2009, 09:32 PM

I'm agreement with Paul
"..Class society rules such as ABS and Lloyd's are derived from first principles and do not represent one man's opinion..."

Most Class rules, for scantlings, are based upon many many years of data collection and model testing and real life-size model testing too, not one bloke who has designed a few boats. All the data that is collated is then run through endless statistical methods for trends and "averages" to arrive at a set of formulae that can be used in many situations.

LR have gone slightly over the top with their latest SSC rules with formulae for formulae!!!...but they seem to take the view that everyone would just use their SSC software, ie punch in the numbers and out pop an answer...hmmm!

However, no matter how one derives scantlings that is just half of the picture. Numbers for minimum modulus require proper analysis for load paths and access for welding, ease of fabricating etc etc etc

MikeJohns

10-25-2009, 10:10 PM

I’d be cautious.
I checked the design of a steel boat for someone who had used this scantling guide and although in the main things were ok I had two concerns.
One was that much of his steel scantlings were on the heavy side for larger steel vessels. The other was that the designer had omitted the floors on the basis of his interpretation. He showed me the guide and I could see how he had been confused in the area of the keel.

I read parts of the book then and I’d consider it as a rough design guide early in the design spiral and before refining the design to class scantlings. These days you’d be well advised to adopt an ISO compliant free guide such as provided by GL.

I contacted Dave about his intended compliance and he said that several design aspects usually needed changing to meet various class requirements but that generally it was all robust enough in his opinion.

The proviso that I would add is that it would pay to get the resulting structure checked by a class society (as Dave Gerr apparently does himself) or by an experienced qualified designer to make sure you made no oversights.

My real moan with Dave’s otherwise informative books and articles is his ‘manglement’ of the SI system ….it’s truly horrible to behold (Sorry Dave :) ).

Alik

10-25-2009, 10:19 PM

Good book when it comes to details such as reinforcements, engine base, etc. Not really useful book for engineering, but maybe it will work with amateur designers designing limited range of craft...

Gerr says it covers boats from 10 to 120', and to 45kts. I am sure that 120' and 45kts are far beyond where rules of thumb can be applied.

Then, method for speed effect on scantlings is wrong - every knot above 10kts gives 1% increase of bottom thickness (p.30). This is nonsense - 10' boat at 10kts is already planning with hydrodynamic lift applied on bottom. But 120' at 10kts is still in displacement mode, mainly hydrostatic pressure is applied. One should deal with relative speed/Froude number to define whether loads are for planning or displacement craft.

Hope they do not use this book as single source for students in Wesltawn… At least they should give alternatives.

Ad Hoc

10-25-2009, 10:27 PM

"...One should deal with relative speed/Froude number to define whether loads are for planning or displacement craft.."

Rightly said. far too many people clearly read this and other similar books and hence influenced in the terminology/understanding and quote speeds in knots when talking about hull speed or planning etc. It is all about the Fn!

Alik

10-25-2009, 11:14 PM

Besides I really like last book from Dave Gerr - 'Boat Mechanical Systems Handbook'. In this format and scope of information it is always in use by our engineers.

'Propeller Handbook' - we don't use it too much for calculations of props becasue we use software for that. But when it comes it dimensioning of shaft and P-bracket - yes, we use it.

'The Nature of Boats' - I still use this book to dimension outboard engine mounts!

There are few good books from Dave, in some points we would disagree but anyway it is valuable opinion.

TollyWally

10-26-2009, 02:06 AM

Life is often divided into 2 spheres, the labratory or office and the field. There is a built in tension between the two. Champions of each can point to a long list of failures in the other. Conservative rules of thumb have a better track record than envelope pushing engineering. It is interesting to note that bleeding edge optimization typified by successful racing teams consists of trial and error efforts conducted in the field.

It's a good book, is it the last word? No, either is any other.

lukedh

10-26-2009, 04:47 AM

Hi.

Gurr's book may have some shortcomings but is a useful guide to put you in the right ball park. While this cannot replace sound design, a calculated figure is based on assumptions of the stresses a boat will encounter in use and include an additional factor for safety.

Gurr himself is an experienced Naval Architect, I quote "A graduate of the Westlawn Institute of Marine Technology, Gerr studied physics at New York University and industrial design at Pratt Institute. A Fellow of the Royal Institution of Naval Architects (RINA), Gerr is also the director of the Westlawn Institute of Marine Technology".

link: http://www.gerrmarine.com/dave.html

So I guess the book is based on his experience of boat design and knowledge of marine technology. There are of course other books to choose from.

I post this just in case anyone is under a missunderstanding that David Gurr isn't qualified.

Cheers
Lukedh

daiquiri

10-26-2009, 06:47 AM

However, no matter how one derives scantlings that is just half of the picture. Numbers for minimum modulus require proper analysis for load paths and access for welding, ease of fabricating etc etc etc
Absolutely true. :!:

As for classification societies' scantling rules, I was not implying that they have not been derived in a scientific way. That's more than obvious, considering the economic burden on them in case of eventual errors.
I was referring to the fact that they will generally give you a ready-to-use formula for anything, and you either know which engineering theory it has been derived from, or you just trust them and use it as it is (which you will do anyways). The same can be said about Gerr's method, albeit with much smaller degree of confidence (especialy now that I've read MikeJohnes' post above) - it might also be a method based on a sound engineering principles, it's just that we (or at least I) don't know anything about it.

Paul Kotzebue

10-26-2009, 10:45 AM

Conservative rules of thumb have a better track record than envelope pushing engineering. It is interesting to note that bleeding edge optimization typified by successful racing teams consists of trial and error efforts conducted in the field.

It doesn't have to be either/or. A good designer should have a solid engineering background and common sense experience. The tension we see in yacht design circles is between the amatuer hobbyist approach and the professionally engineered approach. This is not the case in commercial small craft design where most clients expect the engineering approach.

frank smith

10-26-2009, 11:07 AM

It doesn't have to be either/or. A good designer should have a solid engineering background and common sense experience. The tension we see in yacht design circles is between the amatuer hobbyist approach and the professionally engineered approach. This is not the case in commercial small craft design where most clients expect the engineering approach.

Very interesting discussion .

Just a few questions please. Would all engineering be done by an in house NA?
Do NAs use out side engineering firms ? Is some kind of certificate for an engineered product required ? Could I as a hobbyist get a certified as built plan from a NA or engineering co. .

Paul Kotzebue

10-26-2009, 11:16 AM

Gurr himself is an experienced Naval Architect, I quote "A graduate of the Westlawn Institute of Marine Technology, Gerr studied physics at New York University and industrial design at Pratt Institute. A Fellow of the Royal Institution of Naval Architects (RINA), Gerr is also the director of the Westlawn Institute of Marine Technology".

None of the above includes a mechanics of materials course as part of an ABET accredited engineering program. Mr. Gerr does not claim to have a degree in Naval Architecture or any other engineering discipline. He is not listed as a professional engineer in the state of New York. I recall that Professional Boatbuilder defined a Naval Architect as one who has a degree in Naval Architecture or holds a professional engineer's license to practice Naval Architecture.

We have to take him at his word that he is an expert on the elements of boat strength.

Alik

10-26-2009, 11:22 AM

The tension we see in yacht design circles is between the amatuer hobbyist approach and the professionally engineered approach. This is not the case in commercial small craft design where most clients expect the engineering approach.
Maybe there is a tension in US and some other countries where there are no formal structural requirements for small craft. In Europe compliance to ISO12215 is required - there is no space for amateur hobbyst approach anymore.

Paul Kotzebue

10-26-2009, 11:25 AM

Just a few questions please. Would all engineering be done by an in house NA?
Do NAs use out side engineering firms ? Is some kind of certificate for an engineered product required ? Could I as a hobbyist get a certified as built plan from a NA or engineering co. .

Frank,

Yacht designers use outside firms all the time. Companies like High Modulus and SP Systems provide structural engineering services, for example. Generally, states require a professional engineer's license to offer engineering services to the public. Most states exempt industry from this requirement, so boat builders do not necessarily have to be licensed to do their own engineering. A certified as built plan bearing the stamp of a professional engineer would have to be prepared by or under the supervision of a licensed professional engineer.

Paul Kotzebue

10-26-2009, 11:30 AM

Maybe there is a tension in US and some other countries where there are no formal structural requirements for small craft. In Europe compliance to ISO12215 is required - there is no space for amateur hobbyst approach anymore.

Now that ISO12215 is a requirement for ocean racing yachts built after June 2009, we are seeing the top U.S. sailing yacht designers implementing the European standards as well.

Tad

10-26-2009, 11:52 AM

We've been over this before.......

See my comments here http://www.boatdesign.net/forums/boat-design/plating-thickness-7881-3.html

TeddyDiver

10-26-2009, 12:29 PM

Good book for handy scantlings..
Please bear in mind what Dave states in the introduction "This book was not written for specialist looking for the latest arcane developments in structural engineering.."
My 2c

marshmat

10-26-2009, 12:47 PM

(Disclaimer: I'm not trained as an NA or boat designer, rather, I'm an engineering physicist.)

I find "Elements of Boat Strength" a useful starting point for figuring out, roughly, how a particular system of construction would work for a particular boat. Gerr's rule seems to yield quick, somewhat conservative estimates of appropriate scantlings for a boat of a given general size and configuration.

I'm really not that comfortable using it for much more than preliminary or comparative analysis, though. I would much rather get an estimate of the actual loads, apply a suitable multiplier ("factor of ignorance" as I call it) to those loads, and select materials and sections to withstand the resulting forces. If the engineering justification for a particular set of rules isn't presented before me, I'm reluctant to use them.

Having said that, if I were working on a fairly "normal" monohull design of "normal" proportions, I'd probably just use Gerr's rule, repeat with one or two "official" rules (BV, perhaps, or ABS), and use something a bit beefier than the most conservative of the results.

The design I'm working on now, a power trimaran, is not within the scope of Gerr's rule and is subject to slightly unusual service conditions, so the engineering there is from first principles with some guidance from ISO and BV standards.

Paul Kotzebue

10-26-2009, 01:26 PM

See my comments here http://www.boatdesign.net/forums/boat-design/plating-thickness-7881-3.html

Thanks for the reference Tad. Very well put and it does bear repeating.

dskira

10-26-2009, 02:51 PM

Ad Hoc: he is confused because for anyone in a marine design related profession to not know Gerr, is like a musician that doesn't know The Beatles

Yes it is true that Gerr is very well knowne in the US. The Beatles are known worlwide. I will not put Gerr (which I admire very much) on the same name recognition as let say Olin Stephens.
Gerr seams to write a lot and unfortunatly do not design much. It is a pitty.
I find some designer is more well knowne because of the amount of writing they do than their design.
But as usual it is my two cents. :)
By the way I prefer the Lloyd's for wooden yacht and wooden ships. The century of Lloyd's experience in wood construction can't be ignored and certainly very unic.
Cheers
Daniel

gonzo

10-26-2009, 03:47 PM

dskira

10-26-2009, 04:34 PM

A typical American design, shallow and beamy will be overbuilt by Lloyd's rules. They were developed for narrow deep hulls. I can't think of any rule not based on scantlings or tonnage. Critizism of Gerr because he has a scantling rule doesn't make sense. His dimensions are almonst identical as if you use Herreshoff or Skene's rules.

Gonzo, I respectufully do not see why a beamy hull and shallow hull will be "overbuilt" with lloyd's. And what you mean by "overbuilt'. A beamy and shallow yacht or fishing boat? Lloyd's take care of both in different categories.
I do not critisize (if you refer to me) Dave Gerr, I like is tutorial attitude, he knows how to share his knoweldge.
McNaugthon also has rules, but never read them.
As for the Herreshoff rules, interrestring but why so complicate. Skenes do not have rules to my knoweldge but Nevin yes. For Yacht and sailing yacht only.
Sorry for my disagrement, if I mistake please correct me. I like to learn, it is always nice, as a good discussion.
Cheers
Daniel

gonzo

10-26-2009, 06:23 PM

A sailing yacht built to ABS tends to be lighter than by Lloyds. I think they are overly conservative and taylored to local models. The interesting about Gerr is that the results are so close to Herreshoff's but easier to find. To me, that is a great vote of confidence. I believer that any designer would admit that Herreshoff was reputable and his scantling rules good.

Ad Hoc

10-26-2009, 07:50 PM

F.Smith
"..Just a few questions please. Would all engineering be done by an in house NA?
Do NAs use out side engineering firms ? Is some kind of certificate for an engineered product required ? Could I as a hobbyist get a certified as built plan from a NA or engineering co. ."

In addition to that good summary above by Paul, I speak from the commercial field.

The answer to your Q is 99% no. My colleague and I, at our previous company for example, did 99% of all the NA/engineering. That is what we are trained to do. By that i mean the obligatory degree and then btwn 5~10years minimum training. Then we can become "professional" NAs.

The 1% is when we have either not had the time to finish off a project, or a specialist does it better than we can and in less time, since not our area of expertise. We have done this on 2 occasions to my recollection, over the past 15 years.

Willallison

10-26-2009, 08:08 PM

The reason's for the move towards 'outsourcing' much of the scantling etc engineering are, I think, twofold.
The first, and foremost, from the designers point of view is to limit liability.
The second, which comes more from the builders perspective, is for marketing reasons. "...high-tech composite construction, engineered by H... M...", so the brochure reads....

dskira

10-26-2009, 08:30 PM

Now that ISO12215 is a requirement for ocean racing yachts built after June 2009, we are seeing the top U.S. sailing yacht designers implementing the European standards as well.

Interresting since al lot of these very trendy productions boat with all the ISO on the world loose their keel, and cost an arm an a leg to search and rescue.
Beside that I think we have two different discuussion, one for the commercial and one for yachts. The rules are not the sames, the ISO is a monumental stupidity for yacht under 24 meters. Now this EU rule is implemented differently in the different country of the EU. How beautiful. Irland is the most easy, Spain a torture. Go figure. You can even paid the VAT twice or three times. Grece has a new, illegal by the EU, taxe on yacht. They don't give a squat. The French don't accept the taxe paid in Irland, and so on. The ISO is even not knowne in Grece. They follow the rule of the drachme.
A disaster of imbecility of pushpaper in Bruxell. Don't talk about EU Standars, they don't exist.
For commercial it is more easy since we use a body of professional, with agencies. We know where we stand. Its is more easy in a way.
I don't like regulation or standards (Awful word for a boat) because they are regulation they don't mean they are right, and I don't feel more important because I follow them. A yacht is a little more that that.
Ok I am done with my rambling :D
Cheers
Daniel

frank smith

10-26-2009, 08:36 PM

Ad Hoc

10-26-2009, 08:48 PM

Frank
"..It seems to me that there are enough people around with the required credentials to allow a designer to put together a design and then have the necessary engineering done..."

This is how i currently get a lot of my work. I am called up by "others" to design for them. I just don't have the network or resources to go out and get the work myself....now I/we are independent.

Daniel

The ISO is an EU standard, it is just the enforcement and method of enforcement that makes it difficult. Just as in the US, each State has its own rules and method of enforcement for each State, which are different to the 'whole' country.

Paul Kotzebue

10-26-2009, 11:31 PM

Interresting since al lot of these very trendy productions boat with all the ISO on the world loose their keel, and cost an arm an a leg to search and rescue.

Daniel,

I don't think the ISO standards for keel attachment have been adopted yet. Designers have been relying on the ABS guide for offshore racing yachts for keel attachment standards. Following the standards does require some engineering knowledge and skill. It's not just a matter of plugging in numbers.

The boats I'm aware of that have lost their keels and the cause has been investigated, the Cynthia Woods and Hooligan, did not meet the ABS guidelines. There was loss of life in both instances. This tells me it is important to have engineering standards for boats and they need to be followed. The problem may be more with those who use the standards than with those who create them.

You mentioned using Lloyd's scantling rules. Lloyd's 1979 rules for yachts and small craft is an excellent source for scantlings of traditionally built sailing yachts. It is still accepted by the USCG for passenger vessels.

Ad Hoc

10-26-2009, 11:40 PM

ISO, section 11.9 Structural Support for Sailing Craft Ballast Keel

TeddyDiver

10-27-2009, 12:40 AM

Keels are still under evaluation by ISO I believe..

Alik

10-27-2009, 01:18 AM

Part of ISO12215 standard for sailing boat keels attachment is not in force yet.

MikeJohns

10-30-2009, 06:01 AM

............... did not meet the ABS guidelines. There was loss of life in both instances. This tells me it is important to have engineering standards for boats and they need to be followed. The problem may be more with those who use the standards than with those who create them..................

The 1986 ABS scantlings for GRP construction were inadeqaute and lead to the detachment of a keel and two deaths that I know of.
They were revamped in 1994. Following a coroners inqust.

How did that occur when the engineering is relatively simple? LLoys register was criticised for being overly strong at the same time these lethal designs were being knocked out under ABS. The word at the time was that ABS was too weak but it took deaths to get them to change.

Current ABS rules appear to be quite inadeqaute for their assesment of small boat fore-deck loads in heavy weather. So now they dopped the whole scantling and everyone is supposed to migrate, either to Lloyds register or G.Lloyds or BV or ISO but ISO is a compromise so I'd stick with one of the others if you don't check your own engineering.

How many pre-1994 boats were built with fin keels to ABS and are falling apart?

Dave Gerrs scantlings should be more than adeqaute in this regard but even reasonable scantling rules can be screwed up by non-engineering background designers , witness the Maxfun 35 debacle and death when the designer confused the keel bolt Ultimate Tensile with yield as well as other very poor errors.

Most NAME types will check the structural side of the design for a few hundred dollars. Many boat designers use engineers to do this, some like Ted Brewer employed engineers in his design office.

Ad Hoc

10-30-2009, 06:21 AM

Mike
I can't say for 100% certainty, but I have a few friends who are yacht designers that use ABS constantly, almost exclusively. The reason why they have been using ABS for many years, since the 80s, is a you point out
"..ABS scantlings for GRP construction were inadeqaute.."..in other words, lightly built. Light structure = cheaper...ie less material costs.

"...LLoys register was criticised for being overly strong at the same time these lethal designs were being knocked out under ABS.."
Correct, as this was their reply to me, whenever i mentioned LR or even DNV as an alternative to ABS, that they are "over built". Hence the preference for ABS. They also said ABS rules were 'easier' to use too.

I've only recently used ABS, first time for 20 years. It was on a 51m steel patrol boat. Oddly enough, the scantlings are far far higher than LR and DNV...most odd. Too much 'over engineering'....

MikeJohns

10-30-2009, 06:46 AM

John
The ABS I was reffering too was for offshore racing yachts known as ABS ORY while you would be using the commercial rules which are very robust and are fully supported.

I should have added that to properly comply with any rule the design should be submitted and approved which acts as a design review.

The problem with pleasure boats is that the construction is only regulated if they are to be used commercially. For private use anything goes and it's buyer beware, in this regard the RCD is a step in the right direction.

DNV is very well supported around the world too , I forgot to mention them, they even have an office here.

Paul Kotzebue

10-30-2009, 09:37 AM

ABS scantlings for GRP construction were inadeqaute and lead to the detachment of a keel and two deaths that I know of.

Which boats were these? I'm not defending ABS, but I am interested to know which boats had keel failures that met ABS ORY.

Dave Gerrs scantlings should be more than adeqaute in this regard

How do you know this?

Most NAME types will check the structural side of the design for a few hundred dollars.

Who?

MikeJohns

10-30-2009, 05:48 PM

Paul

It concerns me that many people including both surveyors and designers in the USA are quite ignorant of this.

I'll try and dig one of the coroners reports for you. I don't now how old you are but it was all well documented when ORY was beefed up signigicantly in scantlings by way of the keel for GRP boats.

Everyone should check the hull thickness in this area of pre 1994 GRP boats built to ABS 1986 minimums. Of even more concern is people using scantling programs and nice old bound books they have been given which are not up to date.

All scantling rules are a bare minimum and designers used to be more conservative, many had engineering training and they used scantling guides as starters for weights and still engineered the hull or copied another robust design. The need to shave every bit of shavable mass lead to the minimums being adopted and scantling societies are not infallable although they get there in the end by a process of constant rule revision.

How do I know Dave Gerr's scantlings should be adequate?

I don't, it's just an opinion I formed, as I said I read his book after checking someones design based on his scantlings and I thought he erred on the heavy side but you would still always check against a current class society guide.

If you want your design checked you'll need to ask around but since you are in Ca and I'm in Tasmania it's probably of no use for me to give you NAMES. I'd suggest that any independant will do a structural check of frame moduli spacing and skin thickness against one of the rules they have a spreadsheet or scantling program set up for. When we did it we sent them a spreadsheet form which they filled in then we checked the scantlings, looked over the construction drawings and signed off.

You'll get the same service (Plan approval) from any of your local societies and their design surveyors are often independant and may be prepared to check against another rule for you.

Paul Kotzebue

10-30-2009, 06:18 PM

Mike,

As a registered professional engineer in California and Washington, I'm one of the few yacht designers in the U.S. who can legally offer engineering services to the public. One of the things I do for a living is to review scantlings of small craft for submittal to the USCG or classification societies. It usually costs more than a few hundred dollars. I'm just curious who the "NAME types" are that will "check the structural side of the design for a few hundred dollars". I don't think there are any in the U.S.

I'm capable of checking my own designs, but thanks for the suggestions.

MikeJohns

10-31-2009, 01:23 AM

Paul
What license do you hold? And anyone can be a 'yacht designer' of course.

Surely every and any suitably licensed engineer can do this legally.
I do see some dubious claims in the US where someone claims to be a PE 'yacht designer' and they are licensed for example as a civil (non structural) engineer. Not even mechanical.

I know several mechanical engineers who offer design assistence to boat designers. Maybe you have just never had the need to search for such a service.

I just wonder why it should cost so much to review a boat design if it is from a designer who has already done the work particulalry if it's to a standard that you are familiar with and have computerised. I usually find the scantlings are fine but the errors are in omissions of things like not achieving required end fixity one way or another.

Bit if you are talking a cutting edge FEA study not to any standard... yes I do that too but then its several thousand dollars. But I don't go there to check scantling compliance.

But I'm really curious if you are a PE and also a yacht designer how come you are not aware that the eralier ORY was deficient ? If you ever see a GRP keelboat built to ABS before the 1994 the first thing you should ask is whether the laminate is sufficient in the way of the keel. There was a big public info campaign here and lots of boats had laminates added to strengthen the hull.

But it would be more fun to talk about engineering.

frank smith

10-31-2009, 01:48 AM

Alik

10-31-2009, 02:10 AM

Even with rules, correct interpretations and engineering experience helps to make right decisions. In case of ABS - they are developed for high-quality construction, no allowance is given to reduced properties of laminates. In ISO12215 there is an allowance, unless particular laminate test data is used.

Question: does anyone have a link to LR's special craft software, including structural? Would like to buy.

MikeJohns

10-31-2009, 05:52 AM

How is it that these boats were produced . Surly they had the science to spec.
the laminate schedule at the time . Is it that the engineering at the time did not take into acount certain factors , or were they not tested enough?
How much is a result of economizing in construction ?

As this may be of interest to others besides myself , would it be possible to post location for info on keel attachment failures.

No it was just an oversight, I'm not sure that some of the people at ABS were ever all that happy with ORY.

To properly put the dates on things:

The 1986 ABS ORY had inadequate hull shell thickness to prevent shear failure at the keel attachment backing plates. This was corrected in the 1994 version.

The coroners recommendation (Australi) following a fatal keel separation was that all light displacement boats built to pre 1994 ABS ORY should be contacted with a view to checking the laminate schedule and where appropriate upgrading to the 1994 requirement.

ancient kayaker

10-31-2009, 10:32 AM

Since keel separation is dramatic, easily recognizable, and a localized failure it catches the attention.

I'm not sure if it is a particularly common cause of loss of life and property, but I would find that surprizing. It seems a much simpler matter than most other aspects of boat design. The static and dynamic loads are accessible to analysis. The material characteristics are known, manufacturing variables are controllable by inspection, and material degradation with age and use can be determined with tests.

And yet, even discounting individual cases of boats that are not built to design, it is not the rare phenomenom that it should be. Is it simply a question of racing craft being built and operated to -or beyond- the limits, or does it also plague commercial and recreational craft to a significant degree?

As a retired engineeer, some posts in this thread leave an impression of a cookbook approach to boat design similar to the build-to-code approach used for housing construction. That is not necessarily a bad thing except there is a lack of confidence being expressed in the various standards. Perhaps I am naive, but I was expecting something closer to aircraft design practice.

gonzo

10-31-2009, 10:41 AM

Getting the voodoo out of boat scantlings, it is a cookbook approach in many ways. Scantlings are simply dimensions required for different parts of the boat. You get the minimum standards by whatever rule you use. Other parts of design, whether naval, aircraft or home, requires experience and common sense. Also, a sense of aesthetics, which is another subject of endless debate.

TollyWally

10-31-2009, 11:22 AM

Not to state the obvious but nearly all failures in this modern world have been engineered by fully qualified licensed engineers. At it's core, modern engineering relies on opinions backed up by lengthy equations that "prove" mathmatically that the opinions are valid, usually after extrapolating the data from a limited series of laboratory testing. It does not always represent real world best practices which are often "overbuilt, over budget".

Elegant engineering is a beautiful but rare creature, solitary individuals in a herd of medicrosy. I don't wish to offend any engineers here but rules of thumb that result in moderately overbuilt structures certainly have their place in the world.

ancient kayaker

10-31-2009, 03:44 PM

Not to state the obvious but nearly all failures in this modern world have been engineered by fully qualified licensed engineers ...

Rubbish! Where on Earth did you get that statistic?

My point, which seems to have been missed, is that the keel attachment is one of the simplest, as well as most important tasks in boat design, no big challenge to determine the forces at work, the properties of the materials used, and the effects of age and use.

My question did not get answered either: is it a real problem or are there just a very few isolated cases that get attention precisely becaue of the perceived simplicity?

TeddyDiver

10-31-2009, 04:26 PM

Just my opinion but on this TollyWally nailed it..
The difference with aero and naval engineering comes from the fact that in the naval environment the max loads met and their frequency are merely estimated with educated quessing, or known also as rules of thumb (or adequate safety factor in a scantling rule). For aeroplanes landings and pressure loads which are a couple of the main stresses for the construction are very predictable.. Thou a boat can be built to take the worst possible pounding for 30 years but then it's defineatly overbuilt..

MikeJohns

10-31-2009, 06:15 PM

........ a boat can be built to take the worst possible pounding for 30 years but then it's defineatly overbuilt.....

Unless it's a Tasmanian coastal fishing boat, in which case it will be underbuilt :)

Rick Willoughby

11-01-2009, 03:27 AM

...
As a retired engineeer, some posts in this thread leave an impression of a cookbook approach to boat design similar to the build-to-code approach used for housing construction. That is not necessarily a bad thing except there is a lack of confidence being expressed in the various standards. Perhaps I am naive, but I was expecting something closer to aircraft design practice.

Terry
Small commercial and pleasure boats are a long way behind aircraft in terms of the engineering detail in the design.

High speed cats built in Australia as recently as the 1980s were under continual repair. In some examples boiler makers were doing repairs whenever they were not at sea.

I have seen crack interception in aircraft frames but not daily crack repairs. I have also seen some corrosion in galley and toilet framing but these areas are known problems and subject to timely inspection - at least in most instances.

The only large ships I have seen closely during construction were submarines and the detail on these were very good. Even to the point of weighing the butts from welding rods so they knew the weight of everything that went into each assembly. I expect large bulk carriers are designed in considerable detail as any weight saving usually reduces cost. I know they have tight limits on loading to prevent hogging.

I do know the maintenance on some large ships is deplorable - way behind most commercial aircraft. I know of instances where ships have not been permitted to sail because bulkheads are rusted through.

Rick W

Ad Hoc

11-01-2009, 07:10 AM

AK
".As a retired engineeer, some posts in this thread leave an impression of a cookbook approach to boat design similar to the build-to-code approach used for housing construction.."

This is because most of the design/structural design is done by non-structural engineers/naval architects. It is as you say, a cook book approach. But on a 5m run about...in reality one doesn't really need to be, but the desire to go bigger or to say "I can now design", after designing/drawing a 5m boat/model, is overwhelming to many.

Since, your comment about:
"..is that the keel attachment is one of the simplest, as well as most important tasks in boat design, no big challenge to determine the forces at work, the properties of the materials used, and the effects of age and use.."
is spot on. If one is a professional trained structural engineer/naval architect, these things are a doddle. This is a simple calculation that would take just a about half an hour or so checking and validating.

But, in the small boat market (which is ostensibly 'private' not public), there has been no call for "professionalism" with regards to what is being designed or built. Since why bother..it is only a 5m boat after all...However, it is only the increasing numbers of accidents and sadly the occasional death, that has lead to the every slowly increasing need for this "market" to be come more accountable and ergo professional. That is why codes like the ISO and RCD etc are being introduced and becoming mandatory.

The "rules/regulations and methodology/practices" that are slowly being adopted, are nothing to "us" in the commercial market. It is the only way we can design boats. It is very strict...doesn't eliminate all errors/mistakes though (nothing can since most accidents are human error), just mitigates a high percentage of them. Which is why you get the likes of me, and a few others, cringe when amateurs sprout XX YY and ZZZ saying they know so much, just because they they have drawn/built a small 5m boat, they think they know design!

A 5m boat, is as you rightly point out...just cooking by numbers. But one doesn't need a nuclear warhead to crack a nut!..ergo, it ain't difficult to do on a 5m boat. But try taking that same approach, cooking by numbers, on a 50m HSC 40knots 400 passenger boat.....what is that about the elephant in the room???!!!!

idkfa

11-01-2009, 08:57 AM

"Not to state the obvious but nearly all failures in this modern world have been engineered by fully qualified licensed engineers ..."

so true, yet funny how the engineers seem oblivious to this!

dskira

11-01-2009, 09:28 AM

"Not to state the obvious but nearly all failures in this modern world have been engineered by fully qualified licensed engineers ..."

so true, yet funny how the engineers seem oblivious to this!

And all the wonder they did which we use everyday and make our life easier and more safe and comfortable.
It is funny how peoples seams oblivious to this
Cheers
Daniel

Crag Cay.

11-01-2009, 09:32 AM

However, it is only the increasing numbers of accidents and sadly the occasional death, that has lead to the every slowly increasing need for this "market" to be come more accountable and ergo professional. That is why codes like the ISO and RCD etc are being introduced and becoming mandatory.
That is factually incorrect. At the outset of the introduction of the RCD, we repeated ad nuseum at all the DTI / RINA / trade association sponsored conferences, that concerns about boat safety were NOT the driver for the RCD. The legislation was enacted to allow free trade within the EU and nothing has changed since then.

The most oft-cited 'structural' issues with boats have been with race boats that are specifically excluded from the requirements of the RCD. Their structural requirements have not changed in that these were either race specific (eg Whitbread / Volvo) or more generally by the requirements of the ISAF OSR. The complication was the termination of the ABS plans approval scheme for smaller boats. The only workable replacement has been (will eventually be) compliance with the ISO structural requirements, but this is driven by self regulation within the racing world and it's wrong to muddy the water by suggesting this has anything to do with the RCD. Obviously if you have a production cruiser - racer that is RCD compliant, it's an easy way to prove you are OSR compliant.

Ad Hoc

11-01-2009, 10:46 AM

C.Cay

Can you state what you mean by "factually incorrect"..???
What facts are these??..I am on one of the MCA committees, these "facts" are new to me..please explain?

Since the RCD states:
"..these guidelines are intended to promote the free movement of goods in the EU/EEA internal market having been presented to Member States’ government experts, industry, notified bodies, users and other parties for comment..."
ok, but goes on to say
"...but it is not binding in the same sense as legal acts adopted by
the Community...The legally binding provisions are those transposing the directive into the national legislation of the EU/EEA Member States."

A very detailed report was conducted to evaluate all these rules, and the findings all point to increasing safety and risk management, even though hard factual evidence did not always wholly support it.

The report starts by noting from the outset:
"..Perhaps unsurprisingly, therefore, this research identified wide variations in the detail of mandatory safety standards applied. However, within this variation there is evidence of a move internationally towards tighter regulatory control on the maritime recreational sector. In many cases, it appears the individual regulator is becoming increasingly prepared to intervene through legislation, this possibly reflecting changing societal values towards recreational vessel safety risk..."

And quotes a few examples, such as:
"..Spain, for example, suggests regulations introduced in 2002 were needed to address the impact of increasing numbers of recreational vessels, increasing power and the risk this presented to other marine users, particularly swimmers..."

and also

"..This would appear to be equally true of the Eire Maritime Safety Act 2005, whose purpose is to strengthen the law against improper use of mechanically propelled personal watercraft (e.g. jet skis) and other recreational craft. The Dáil Éireann debate as reported had little supporting technical detail, though it had near unanimous cross-party political support for the legislation: “Everyone agrees there is a need for improved legislation on maritime safety.”..

then notes:
"..However, the UK is apparently alone amongst the countries reviewed in not using nationwide regulation as part of a recreational vessel risk management strategy.....In individual cases the data may be imperfect, but given that fatalities are generally supported by Coroners' reports in all countries considered by the research, as a body of evidence, it does provide a strong message for the UK to evaluate and similarly utilise this as a data source."

and then summarises with:
"..Some countries can record a net reduction in recreational risk, even in locations where sea conditions may (roughly) correspond to those of UK. The research has though identified that some local decision-makers in the UK see the need to directly intervene in recreational vessel activity, and are doing so..."

The RCD began as "risk" of movement between member states of boats, in terms of commercial costs etc. BUT, when the rules were slowly being adopted, as noted above, the risk to the commercial market argument was being outweighed by the risk management systems and procedures of using the boat, by those that ahve to enforce the legislation...

This is borne out in one of the conclusions:
"..The evidence suggests nations which regulate recreational vessels primarily through legislation, do secure a reduction in risk.."

So while to some these codes may appear to to allow free movement between member states, the ground swell of opinion is that it is to "enforce" a more risk based approach to recreational boating by the use of legislation to counter any increase in accidents, real or otherwise..

gonzo

11-01-2009, 10:48 AM

The thread being about Gerr's book, I think it is good. He clearly limits the application of his method, and within its limits no one has pointed out any major shortcomings. The scantlings are conservative, and there is nothing wrong with it.

Crag Cay.

11-01-2009, 01:32 PM

Factually Incorrect?

Okay, here goes. The discussion is about design and the engineering of boats. You said (admittedly whilst contradicting yourself):

"But, in the small boat market (which is ostensibly 'private' not public), there has been no call for "professionalism" with regards to what is being designed or built. Since why bother..it is only a 5m boat after all...However, it is only the increasing numbers of accidents and sadly the occasional death, that has lead to the every slowly increasing need for this "market" to be come more accountable and ergo professional. That is why codes like the ISO and RCD etc are being introduced and becoming mandatory"

and I highlight " . . it is only the increasing numbers of accidents and sadly the occasional death, that has lead to the every slowly increasing need for this "market" to be come more accountable and ergo professional. That is why codes like the ISO and RCD etc are being introduced and becoming mandatory"

I believe you are suggesting that the introduction of the RCD was driven by "the increasing numbers of accidents and sadly the occasional death" and therefore the design and construction in the small, recreational craft market was in need of being "more accountable and ergo professional".

Well, this was not so. The was at the time no mechanism within the EU for a directive to address this issue, even if those reasons had been cited (which there weren't). The only mandate for the initiation of the RCD was normalisation of trade.

There were regulations brought it around that time, that were indeed in response to deaths and accidents, but these were 'Codes of Practice' and related to charter boats and Sail Training Vessels in particular, but these have all been within the commercial, not leisure arenas. The difference between to two types of legislation can be seen by who has authority over their implementation; the MCA inspect and pursue non compliance of Codes of Practice, whereas it's the Trading Standards Officers at council level that are responsible for the enforcement of the RCD.

At national level within the EU, the RCD has indeed been drawn into local initiative around marine safety. But whether Ireland has seen a decrease in Jet Ski accidents since they have enacted controls has nothing to do with the RCD. I have yet to see any research that has attributed any increase in boating safety SOLEY by the enacting of the RCD legislation. That is, an increase in safety that is directly attributable to their design and construction and subsequent Categorising of recreation vessels as A-D at the moment they are first placed into the market.

Ad Hoc

11-01-2009, 07:06 PM

C.Cay

It is a contradiction that i highlight, as also noted by the report.

I have sat on endless MCA meetings where a new piece of legislation under the EU banner for "harmonisation" and ease of "cross border" movement has been brought in. Is the first thing that we debate, well, i can now sell my boats to Italy with no problems, or go an buy a cheaper boat in Greece??

No.
Always it has been able, risk and mitigation of the perceived risk, not from a financial position of ease of movement either. Often the committee, have had to investigate the implications of the new piece of legislation sometime expending unnecessary amounts of money, just to gauge the implications of the risk. One i recall a few years ago was the "Vibration" directive, 2002/44/EC, the debate on the implications for HSE, amazing!!!

It does not matter whether there has or has not been a decrease in accidents, even though some states report a down turn once implemented. It is the social and public perception of such.

For example. When the MCA finalise their endless reports and various bits of new code with statements thus:
"..The purpose of the Marine Equipment Directive is to enhance safety at sea and the prevention of marine pollution through the uniform application of the relevant international instruments relating to marine equipment for which EC type approval safety certificates are issued..."

You still think it is about the notion of "ease of cross border movement"..????. That is what it may says on the cover, but in reality it is far from the truth.

Crag Cay.

11-02-2009, 04:47 AM

I'm sorry, but this is very muddled.

The Vibration Directive has nothing to do with the RCD, it's a act to protect 'workers' across all industries. It was indeed driven by compensation concerns as the payouts for coal miners / road workers and other pneumatic drill users with white finger syndrome is (IFAIK) still to be determined, but will be vast! That's why the HSE was involved, because it relates to people 'at work'. The HSE has no involvement whatsoever with the RCD.

Again the MED is a commercial 'work' directive. Completely separate from any requirements of the RCD. Admittedly, charter yachts are included, but they are now considered commercial craft.

The underlying premise of much of this thread has been that, in the past, non NA boat designers used 'cook books' like Gerr's to produce boats that have caused a "number of accidents and sadly the occasional death". And this sad situation has been rectified by the introduction of the RCD and similar (ie, standards pertaining solely to the design and construction of recreational craft).

To advance this premise you need to give evidence of the rate of these accidents before the RCD and the percentage reduction which can be solely attributed to its introduction and not any other factors that may have been introduced concurrently, such as restrictions on use of vessels (Spain), licensing of jet skis (Ireland) or speed limits (UK), for example.

Ad Hoc

11-02-2009, 05:40 AM

It is becoming muddled, because that is what all these laws are, muddled, ill conceived and ill implemented. The whole EC directives ahve been forced down because of a spat between a woman on the EU parliament that was snubbed by the "boys" committee.!! There was no IMO or maritime review at all.

I didn't say the Vibration directive has anything to do with the RCD. I used that as an example, since i sit on one of the MCA committees. So i know how the "process" works, and where these directives, commercial or pleasure, are coming from. If you think this is not the case, then fine, but this is not from the experience I have. Do you sit on any of the MCA committees?

"..To advance this premise you need to give evidence of the rate of these accidents before the RCD and the percentage reduction which can be solely attributed to its introduction and not any other factors..."

As I've tried to explain and also the MCA report does stress this note this too..this data is sketchy and from various sources, some reliable some not, and often with not enough sample history. But the "perception" is that.....it needs regulating, because the "perception" is that there is an increase in accidents, generally made very public by the media (which always distorts the views). Which is exacerbated by any minor incident, with a pleasure boat, that has an accident. Ergo...about time it is regulated, etc etc. It is a self fulfilling prophecy. No one really knows what the true figures are, perhaps never will, other than Spain and Ireland. I'm not advancing any premise at all,...just stating the current position.

The introduction of the 'wheel mark' for equipment, as all RCD boats must comply with...as i noted, nowt to do with harmony to sell in member states, as is the common belief; it is totally risk/safety driven. Why is this then, if your assertion of 'cross border only' for the code, is the premise?

But if you think otherwise, fine..clearly you're not convinced and remain in the belief that the RCD is purely for "ease of cross boarder selling" only.

TeddyDiver

11-02-2009, 11:12 AM

Have to remember the difference btw the political motives in the EU (common market and standardisation etc) and the more case sensitive goals in the specific committees and the fact that they are not contradicting each other..

Crag Cay.

11-03-2009, 06:34 AM

I'm perfectly aware of the 'politics' in the committees formulating the various parts of the RCD, but I was hoping an allegation that a "number of accidents and sadly the occasional death" being caused by shoddy design practices prior to the introduction of the RCD might have been based on more than perceptions and self fulfilling prophecies.

It's also worth remembering when quoting the MCA, that much of their output is to advance their commercial aims. They are semi autonomous agency and need to continually develop new operations to either generate revenue streams or justify continual increases in Government funding. As they say: "Our vision is to be a world-class organisation that is committed to preventing loss of life, continuously improving maritime safety, and protecting the marine environment: Safer Lives, Safer Ships, Cleaner Seas". They are quite open in recognising that increased legislation and licensing helps them meet all these aims. Understandably, they therefore produce 'reports' to advance their ambitions. No one's suggesting they're 'untrue' in any way, but the authors have no responsibility to consider any other issues because if they can find someone to fund their cracking of an egg with a sledgehammer, so be it. As long as it's their sledgehammer.

A good (albeit small) example of their expansionist tendencies, is their provision of 'rescue facilities' on the major Lakes in the English Lake District. Up to now, this has been done entirely by volunteers with no problem whatsoever. However, after some lobbying by the MCA of politicians using the 'what if' scare mongering scenarios, a large amount of government money was found for the MCA to take over, with new boats, buildings, 4x4 vehicles, etc, etc. A small example, but typical of the mindset of the MCA at present. (This is not unique to the UK; in fact it pales into insignificant compared the the US 'Department of Homeland Security!)

Interestingly, when the MCA was established, the most admired and professionally recognised part, the Marine Accident Investigation Branch (MAIB), was kept separate from them and under full public control at the Department of Trade. It's the MAIB's reports (often at the behest of Trading Standards) into things like Hooligan V's keel loss, the swamping of Mollyanna off Anglesey, etc, that have given real insights into problems that need to be addressed. If you combine the insights from the MAIB, the training and education (and Notified Body work) done by the RYA and the protection of young novices by the Adventure Activities Licensing Authority, you can see why most people in the UK think this is a satisfactory way to ensure a very good safety record in the recreational boat world. They can also see that the MCA's ambitions are unnecessary and unwanted - but that won't stop the MCA lobbying for them. We just need to recognise much of their output for what it is; propaganda.

gonzo

11-05-2009, 02:15 PM

VIVA Gerr

dskira

11-05-2009, 02:54 PM

VIVA Gerr

Viva Che Gerr-vara you mean? :D

gonzo

11-05-2009, 03:44 PM

I would not call him a communist terrorist, ever. It means hurray Gerr.

dskira

11-05-2009, 04:06 PM

I would not call him a communist terrorist, ever. It means hurray Gerr.

Yes, I know what you meant. I speak Spanish fluantly.
Gonzo, Gonzo, you take life to seriously, I was just kidding, I thought you will get it. :p

Cheers
Daniel

gonzo

11-05-2009, 04:12 PM

Your photo looks suspiciously alike with Fidel's. I thought maybe you were him in disguise.

dskira

11-05-2009, 04:52 PM

Gonzo, You make my day. :)
It is true, now you told me I find some some similarity with him, althought I have the whole set, and they say he as a missing piece :P
Cheers
Daniel

gonzo

11-05-2009, 05:48 PM

So, viva señor Gerr

Timm

11-08-2009, 11:33 PM

I use Gerr's book for double checking my calcs on small wooden boats. I also use it to help size things like chine logs and stems as I have never found any really good method of calculating these items. Most times my calculations are more conservative than similar successful boats, making me wonder how that boat is holding together.

I was taught that blindly following ABS rules when designing is cookbook engineering. The proper way to do it is to calculate the structure and then check to see if it meets the applicable standard.

As for ISO rules, I always thought categorizing boats as to how large a sea they could be used in was the height of foolishness. I can see some beginning boater getting killed because the sticker on the boat said it could go out in 10' seas, when the captain was only qualified to run a boat in a mill pond.