Steelboats

[sarabande]

Quote Originally Posted by Brent Swain
What centreboard ? Did I mention centreboard?
The keel breaks the surface, increasing 'its righting moment.
Your suggestion that having a friend check my drawings, can give predictions on how it sails, which are more accurate than cruisers' experience on how it actually sails, is ludicrous.
Search Silas Crosby ,and Tagish, for info on how she sails, which is far more accurate and reliable than armchair predictions.


As usual from you, a partial, selective, answer evading in this case, reasons for the spike in the curve, the odd AVS and showing that you arr not accurate in your terminology. In #542 YOU say "the lifting of the keel takes effect." A lifting keel is a centreboard. YOU make no mention of the keel breaking surface. "Lifting".

And yes, the whole purpose behind the science of naval architecture and the science of modelling (not just making 'models' for you to use "to double check displacement, LCB and prismatic coefficient") is that one can by force of reason predict how a boat will behave in the water. If you believe that boat builders just build a hull, plonk it in the water, and then say, "Ooops, my prismatic coefficient looks a bit wrong" or "Ooops, I have got the buoyancy too far aft" or "Ooops, she's rather low on the planned waterline" then you are stuck in the naval middle ages.

Sure, feedback loops from people who take the boat out and sail it are useful in developing the knowledge and skills of a shipbuilder or naval architect, but boat building has evolved and gone beyond the empirical "lines by eye" of yesteryear. That's the whole purpose of science and using computers with cheap - even free - programs. You can predict how a boat will sail, you can predict how she will respond to varying wind strength, you can predict righting lever moments and AVS.

That's all part of the intelligent design function and you are rejecting the science of numbers in design. Sure, you have lots of experience putting bits of steel together to make a boat, and lots of ideas about preventing rust, making anchor winches, blocks, self-steering, but it's all done without the depth of knowledge that comes from understanding the principles, the science and the application of naval architecture.

You persistently fail to answer the questions, So I'll try again. That stability curve is an oddity. How was it derived ? What's the cause of the spike at around 100^o. Why on earth is the AVS at 160 rather than a more normal 120^o ish ? Why is the stability ratio so skewed ?

Numbers matter, Brent.

 

[SlowlyButSurely]

Quote Originally Posted by Brent Swain
What centreboard ? Did I mention centreboard?
The keel breaks the surface, increasing 'its righting moment.
Your suggestion that having a friend check my drawings, can give predictions on how it sails, which are more accurate than cruisers' experience on how it actually sails, is ludicrous.
Search Silas Crosby ,and Tagish, for info on how she sails, which is far more accurate and reliable than armchair predictions.


As usual from you, a partial, selective, answer evading in this case, reasons for the spike in the curve, the odd AVS and showing that you arr not accurate in your terminology. In #542 YOU say "the lifting of the keel takes effect." A lifting keel is a centreboard. YOU make no mention of the keel breaking surface. "Lifting".

And yes, the whole purpose behind the science of naval architecture and the science of modelling (not just making 'models' for you to use "to double check displacement, LCB and prismatic coefficient") is that one can by force of reason predict how a boat will behave in the water. If you believe that boat builders just build a hull, plonk it in the water, and then say, "Ooops, my prismatic coefficient looks a bit wrong" or "Ooops, I have got the buoyancy too far aft" or "Ooops, she's rather low on the planned waterline" then you are stuck in the naval middle ages.

Sure, feedback loops from people who take the boat out and sail it are useful in developing the knowledge and skills of a shipbuilder or naval architect, but boat building has evolved and gone beyond the empirical "lines by eye" of yesteryear. That's the whole purpose of science and using computers with cheap - even free - programs. You can predict how a boat will sail, you can predict how she will respond to varying wind strength, you can predict righting lever moments and AVS.

That's all part of the intelligent design function and you are rejecting the science of numbers in design. Sure, you have lots of experience putting bits of steel together to make a boat, and lots of ideas about preventing rust, making anchor winches, blocks, self-steering, but it's all done without the depth of knowledge that comes from understanding the principles, the science and the application of naval architecture.

You persistently fail to answer the questions, So I'll try again. That stability curve is an oddity. How was it derived ? What's the cause of the spike at around 100^o. Why on earth is the AVS at 160 rather than a more normal 120^o ish ? Why is the stability ratio so skewed ?

Numbers matter, Brent.

Why would you think an AVS of 160 strange? A Contessa 32 has an AVS of 157. High ly desirable for a cruising boat one would have thought.

 

[NormanS]

When I read about the increase in righting moment "when the keel lifts" it was perfectly clear (to me) that it meant the keel no longer being partly supported by its water displacement, but then I see life in reality, and not as strings of numbers.

 

[SlowlyButSurely]

When I read about the increase in righting moment "when the keel lifts" it was perfectly clear (to me) that it meant the keel no longer being partly supported by its water displacement, but then I see life in reality, and not as strings of numbers.

Ditto.

 

[GHA]

and it only takes a few minutes to weld stuff to the deck (later he admitted you have to remove the interior epoxy).

He's right, it does only take a few minutes to weld stuff on deck. Like it just takes a few minutes to roller on some paint on a wall when you've done all the prep.... Simple in the lazarette or bow where there's no headlining or foam, pain inside taking the headlining off - though same for any boat in that respect - more so with steel with the sprayed foam as well, more reason to design and build it right in the first place. Least you'll never have to bed it in again like and it will never leak. Still a pain though.

I found it very surprising that he also stated that a intervals you should replace all the interior foam and Epoxy. The amount of work involved in this was definitely the main reason for ditching steel......

...I can weld and work steel plate but am not so sure about FiberGlass so did consider a steel boat of some sort, not now

Scheduled replacing of foam sounds odd, maybe after many many decades.
Basing your decisions on one rather 'vocal' guy you've never met having a bit of a rant on a web forum seems a light on research, there are a few good resources on the subject on the web & books at amazon.
https://www.boatdesign.net/forums/metal-boat-building/
https://metalboatsociety.wildapricot.org/
http://www.kastenmarine.com/articles.htm

Though as mentioned many times, for most GRP is a better bet.

 

[Motor_Sailor]

. . . Why on earth is the AVS at 160 rather than a more normal 120^o ish ? Why is the stability ratio so skewed ?
Numbers matter, Brent.

What's skewed? It's written on the graph that this design analysis includes a cabin house and sealed mast. Although it doesn't say how big the cabin house was.
But including the bouyancy from these is not unusual - the large deck saloon was the reason Hanse claimed that their Moody deckhouse design had an AVS of 180°, even though it would need to rely on the integrity of its patio doors.
The RNLI uses the same argument for maintaining their AWLBs are self righting.

The question you have to ask is would the mast stay intact after a complete roll and would the windows and hatches remain watertight?
Either the RNLI over engineer their closures or yacht glazing and hatches must be questionable.
Whilst Syabrite would have his own views, I would remain cautious of placing too much reliance on ordinary yacht cabin trunks contributing to ultimate stability. Sealed masts more so.

 

[[70521]]

I've asked about his quality control of his steel supply, given the evidence of the Titanic that I kindly linked to for him. Still waiting an answer.

Still not hear anything about quality control of BS raw material.

 

[NormanS]

Still not hear anything about quality control of BS raw material.

I don't think that even Brent Swain has ambitions to build something quite as big and structurally demanding as the Titanic. I would imagine that he would be exactly the same as any sane person looking for a few sheets of steel plate, and buy from a steel stockholder. That's certainly what I did, when I built a steel yacht. What did you do?

 

[rogerthebodger]

I and perhaps others would be very interested to read some technical details, or even see a photo of your yacht GHA.
I've sailed all sorts, and owned all sorts (except ferro!), presently have 1 large iron/steel, 1 medium wood, both gaff cutters.
Just started a formal college stick welding course to learn it properly, MIG which I'm familiar with, is not so handy for adding cleats on 10mm steel decks etc for obvious reasons.

I also have a steel boat that I built from a deck and hull built in 1978 by a friend of the designer Angelo Lavranos.

I finished the build in 2009 after purchasing the deck and hull end of 2004 and started work in jan 2005

link to pics in my sig.

 

[DownWest]

Have a look here: http://www.kastenmarine.com/frames_first.htm and scroll down to 'Variations on a Theme' Origami is mentioned, and might explain why Kasten is not on BS's Christmass card list.

 

[DownWest]

Still not hear anything about quality control of BS raw material.

While one might question lots of BS's stuff, Mild steel is what it is, quite strong enough to build a boat and can be held together with even rough welding. Mentioning the Titanic is hardly relevant, unless your tongue is well into your cheek...

 

[Mister E]

While one might question lots of BS's stuff, Mild steel is what it is, quite strong enough to build a boat and can be held together with even rough welding. Mentioning the Titanic is hardly relevant, unless your tongue is well into your cheek...

The reply is tongue in cheek in response to his bland statement claim that steel boats dont sink.

I am not bothered about BS but when he started insulting me for asking basic questions about coating the steel then he is fair game for hard to answer questions about his statements.
Unfortunately I do not know to search for the original thread as I can only get 4 pages to show. But if I can show his own statements showing inconsistency then I will.

Some of his statements remind me of a Used Car Salesman.

 

[john_morris_uk]

While one might question lots of BS's stuff, Mild steel is what it is, quite strong enough to build a boat and can be held together with even rough welding. Mentioning the Titanic is hardly relevant, unless your tongue is well into your cheek...

I agree that steel is inherently strong. Steel is tough stuff. Its got lots of good properties (like it springs back after limited deformation and is elastic and doesn't shatter or puncture easily.) However that doesn't absolve the designer who sells designs for other people to build and go to sea in from doing some basic structural calculations.

Brent will hate this, but I've just noticed some comments quoted on the metal boat building pages of another forum. It's self explanatory and sums up some of the reasons I remain extremely skeptical of some of Brent's claims.

Tom Macnaughton, an engineer who set up the Canadian yacht design school has been warning people about Brent for decades. He has a succinct article on Brent's method that was posted on BD net years ago, I'll copy it here :


" Periodically someone will just decide that the transverse framing is not necessary. They always come up with great sounding verbal rationalizations but have never actually done the math.
The amount of weight you can save by tailoring construction to save the absolute maximum in weight, including custom spacing the transverse frames and other transverse members is so minimal and the mathematics necessary to properly predict where you can reduce transverse framing is so complex that I am certain that no one advocating the elimination of transverse framing has actually done the math.

They are just building cheap, weaker boats.

One North American advocate [Brent Swain] has written a book which he told me "proved" his case, yet on buying his book I found there was no real structural analysis in it and the one piece of math in the book which applied to reducing framing was wrong.

There have been recent attempts to reinvent the construction method. Any reduction of the scantlings simply produce a boat less strong than the other methods. Naturally a rationale for this cannot be put in engineering terms. There it would evaporate.

The overall rigidity of the boat is largely dependent upon the framing. This leads into another argument. This one says that you can eliminate the framing by increasing the thickness of the shell plating. While this would, in theory, and viewed in isolation be true. It does not really work out because stiffness usually comes from thin deep frame members with high section modulus for their weight. Thickening a thin relatively heavy plate to provide the lost strength from removing the frames is very inefficient. The net result is that if you eliminate framing you about double the weight of the hull shell.

In an actual calculation comparing a normal hull framed both longitudinally and transversely with one that eliminated the framing the increase in weight of the metal structure of the vessel was 96%. Even disregarding the consequences for plate forming operations and welding operations of going to thicker plate, it should be easy to see that the large weight penalty is not acceptable because the performance of the boat will suffer terribly.
Do we really believe that these people are making the shell plating as thick as necessary to gain back the strength lost by eliminating the framing, given this weight penalty? I think it highly unlikely in view of their claim that they can reduce costs. Therefore should a metal boat be promoted as “frameless” you can essentially say that something is wrong.

A North American advocate [Brent Swain] has written a book which in one place compares the stiffness increase obtainable by using a thicker plate versus a thinner using an erroneous prediction of the relationship of thickness to stiffness. Presumably his entire system advocating reduced framing is justified by basing it on this erroneous calculation. There appears to be another interesting reason for this intense desire to justify reduced framing. We have noticed that all the structural members whose removal is advocated are the ones whose shapes are difficult to predict if you do not understand how to design the vessel with developed surfaces and produce patterns and plate expansions graphically such that every piece of the boat can be precut and can be set up and welded into a predictable shape.

Instead of this fully predictive system these boats seem to start out as scale hull plate patterns created by trial and error by cutting shapes and “folding” them until a shape is derived which looks good. Then the full sized patterns for the plates are scaled up for various sized vessels. However this trial and error system leaves no way to predict the shapes of transverse frames, watertight bulkheads, floor timbers that follow the shape of the hull and keel, etc. Interestingly enough it is these same members whose shape cannot be predicted using these methods that suddenly are declared “unnecessary”. At best this seems an exercise in self-delusion.
One final argument made for “reduced framing” is that if boats are composed of curved surfaces and that curved surfaces are stiffer and therefore don’t need framing. Let’s get real, even to figure the deflection on a simple curved beam of constant radius gets you into calculus. When you get into anything as complex as a boat hull with varying curvature in all directions, not to mention chines, deck edges, varying loads from ballast keels, large engines or rigs, the math pretty much goes off the charts. I just simply don’t believe that the folks I’ve seen advocating this as a reason to reduce framing have done these calculations.
Even with today’s computers and some pretty fancy and expensive software achieving any significant weight savings given the normal complexities of hull shape is quite unlikely even without considering some of the other factors which tend to make it difficult to save weight in real world hulls. Among these are the fact that without frames to stiffen the structures all the stress simply runs to stress concentration points where the hull may be reversing direction of curvature, be flat for hydrodynamic reasons, have some sort of chine or other corner around which the stress will not carry without some support.
Given all this the prediction of stress levels to sufficient accuracy in any given area to allow the reduction of scantlings on the basic of curvature becomes unrewarding and in practice is never done. My experience is that the people asserting that they can make such scantlings reductions, although speaking with great confidence and often with much disparagement of those who question them have not in fact done the analysis necessary to develop rational scantlings and are in fact just deciding to believe what they want to believe. One common characteristic of these promotions seems to be little or no space devoted to any real structural analysis of the relationships between methods. There seems to be a lot of space devoted to circular arguments saying that no proof is needed because only very stupid people living in the past could possibly not see the superiority of this new method. The evidence that these people are stupid is that they ask for the proof! These are “religious” arguments in that we are asked to “have faith” and those who doubt are castigated as lacking in the vision of the “true believer”. You will find us always on the side of “doubt” rather than faith.
We are always worried that we have made a mistake, have failed to see a possible failure mode, are using a model that is not as predictive as it might be possible to construct, etc. The “true believer” is unencumbered by doubt and therefore need never check for mistakes, worry about failure of imagination, etc.
We don’t buy into this and you shouldn’t either. In conclusion, do not be distracted from the lessons of real structural analysis by the promotional materials of these companies.

This is simply another repetition of the mistakes that builders have made over and over. I would suggest remembering an old principle of design: If structural analysis says a boat is strong enough it may be wrong, but if structural analysis says a boat isn’t strong enough it is probably correct. "

Tom MacNaughton YDS

from https://www.boatdesign.net/threads/...y-steel-building-methods-that-is.34211/page-8

 

[NormanS]

Following on from this, I expect you have evidence of Brent's boats falling apart?

I built a 35ft multi chine (3) Alan Pape designed yacht. Yes it had frames, and probably more significantly, chine bars. Obviously, I have no way of proving it, but I always thought that after the hull and deck were complete, the relatively flimsy frames, could easily have been removed without affecting the strength of the structure. To my mind, the frames were only needed to facilitate the method of building. How much strength do a few bits of 50 x 5mm flat bar contribute to the fantastic strength of a completely welded steel hull and deck?

 

[john_morris_uk]

Following on from this, I expect you have evidence of Brent's boats falling apart?

I built a 35ft multi chine (3) Alan Pale designed yacht. Yes it had frames, and probably more significantly, chine bars. Obviously, I have no way of proving it, but I always thought that after the hull and deck were complete, the relatively flimsy frames, could easily have been removed without affecting the strength of the structure. To my mind, the frames were only needed to facilitate the method of building. How much strength do a few bits of 50 x 5mm flat bar contribute to the fantastic strength of a completely welded steel hull and deck?

I don’t think they fall apart but I do expect someone who writes so adamantly about how his designs and construction methods and practices are the bees knees to be able to come up with some basic calculations and figures. The point of the bit I quoted is that he can’t. I’ve asked him and others have asked him and all he sticks to is ‘well it sails brilliantly and every time I’ve run it aground on a reef it’s survived’.

Many of the calculations are bread and butter to a proper designer. I’ve got a friend who is a naval architect and a serious sailor and he agreed that he will have a go at doing some of the calculations if he is given sufficient drawings and data. Unfortunately the outline drawings Brent has supplied me are nowhere near enough data.

 

[Achosenman]

Following on from this, I expect you have evidence of Brent's boats falling apart?

I built a 35ft multi chine (3) Alan Pale designed yacht. Yes it had frames, and probably more significantly, chine bars. Obviously, I have no way of proving it, but I always thought that after the hull and deck were complete, the relatively flimsy frames, could easily have been removed without affecting the strength of the structure. To my mind, the frames were only needed to facilitate the method of building. How much strength do a few bits of 50 x 5mm flat bar contribute to the fantastic strength of a completely welded steel hull and deck?

I’m sure there are calculations that can provide the answer. Perhaps you should do them to prove your theory.

I continue to be amazed that BS believes qualified and skilled naval architects are wrong because they don’t have as many miles at sea as he claims. Yet conversely he thinks his experience at blundering into reefs, somehow gives him boat design qualifications.

 

[[70521]]

I don't think that even Brent Swain has ambitions to build something quite as big and structurally demanding as the Titanic. I would imagine that he would be exactly the same as any sane person looking for a few sheets of steel plate, and buy from a steel stockholder. That's certainly what I did, when I built a steel yacht. What did you do?

I don't manufacture boats, therefore am not responsible for quality control! BS builds boats for customers, I am assuming he gets paid for them, therefore I am interested in the Quality Control that he has for materials.

I have spoken to a manufacturer of boats who had problems with the quality of raw materials. Somebody in the supply chain was swapping high grade materials for cheaper, lower grade stuff and after a lot of failures in service did a huge amount of work to sort out the problem. Eventually going back to the component manufacturer and getting certified supplies and as if by magic the problem stopped.

 

[NormanS]

I don’t think they fall apart but I do expect someone who writes so adamantly about how his designs and construction methods and practices are the bees knees to be able to come up with some basic calculations and figures. The point of the bit I quoted is that he can’t. I’ve asked him and others have asked him and all he sticks to is ‘well it sails brilliantly and every time I’ve run it aground on a reef it’s survived’.

Many of the calculations are bread and butter to a proper designer. I’ve got a friend who is a naval architect and a serious sailor and he agreed that he will have a go at doing some of the calculations if he is given sufficient drawings and data. Unfortunately the outline drawings Brent has supplied me are nowhere near enough data.

I can understand how Brent's style of discourse doesn't go down well with the "Establishment", and he obviously upsets you. But to be fair to him, he is building boats using a relatively cheap and simple method. They float, and apparently sail. There is no evidence of them falling apart or being inherently dangerous to their crews. That being the case, what benefit would be obtained by your much vaunted " calculations", except providing "bread and butter" to a designer?

I can just see the head shaking and tooth sucking that took place when one of our ancestors got fed up hollowing out logs, and instead lashed some planks together in an early form of clinker construction. History repeats itself.

I have no interest in again building a steel boat, but I have an open mind, and look on projects from a practical, rather than a theoretical viewpoint.

 

[dom]

For that last 200m or so there’s a change of sound, tone, and wave pattern; one instinctively knows the distance from a lee-shore beach. A glance over the shoulder, a few more strokes, feather the oars, 3-2-1, crunch. Still love that bit!

The thought of unexpectedly hearing those same sounds from the cockpit at night fills me with dread. Survivors brim with insights to prevent a recurrence by them or others.

Wld be interested to hear about the other strand of this thread.

 

[john_morris_uk]

I can understand how Brent's style of discourse doesn't go down well with the "Establishment", and he obviously upsets you. But to be fair to him, he is building boats using a relatively cheap and simple method. They float, and apparently sail. There is no evidence of them falling apart or being inherently dangerous to their crews. That being the case, what benefit would be obtained by your much vaunted " calculations", except providing "bread and butter" to a designer?

I can just see the head shaking and tooth sucking that took place when one of our ancestors got fed up hollowing out logs, and instead lashed some planks together in an early form of clinker construction. History repeats itself.

I have no interest in again building a steel boat, but I have an open mind, and look on projects from a practical, rather than a theoretical viewpoint.

But it didn’t take long before some people were much better than others at forming and lashing the strakes together. They formed guilds and became master craftsmen. They kept their trade secrets safe but they handed down best practice to their apprentices.

Eventually mathematical modelling and research came along.

I am very happy to agree that a hands on iterative process can produce good products but to ignore hard won research and strength calculations is foolish. If Brent sold his designs in some countries and there was an incident that lawyers could ascribe to his work or design (and lack of basic calculations) then he’d find himself in deep guano.

I don’t have a particular problem with him building his boats or sailing them and crashing them.

I do have a problem with the potential for dreamers to get suckered into his world without knowing the full facts. Lack of calc’s is just part of the Brent Swain fantasy. His only retort is to point out he and a few others have sailed this way for years. As most people recognise, that means diddly squat. Many years ago hundreds of people running steam engines and boilers claimed that they’d always built them this way and there was no problem. A few explosions and deaths and certifications and inspections of boilers became mandatory.

Fortunately, even in contemporary UK you can still build a modestly sized boat and put to sea without any qualification or testing. (I’m assuming it’s not commercial and it’s under SOLAS size). However making outrageously phantasmagorical claims about how safe ‘your’ design and practices are’. is not sensible and needs to be challenged.