Realistic scantilings

[wizard69]

Originally Posted by MikeJohns

Why do you always do these sideways leaps into the stinking swamp when the discussion gets firm and technical ? I also think you would find Germansche Lloyds ( Not Lloyds ...different organisation) small vessel scantling guide very illuminating too. Read it it's free on their website.
Arvy who started this thread is probably worth you contacting for some offline advice, he has probably got to grips with it by now.

ABS also clearly and simply identifies the loads that have been identified as the desirable safe design criteria (from experience). So here's two simple questions that any prospective client should ask you:

I'm a bit amazed that you demand in one notion detailed specs and such on Brents designs (Derived form sound engineering math apparently) and then make reference to "design criteria (from experience).

Not that I'm saying the ABS design experience is bad just that you can't at the same time dismiss the design experiences of a builder with ships under his belt. You are just a likely to find example mistakes in both repositories.

What is your design criteria for the foreward lower pressure head on a 57 foot vessel ? What analysis have you done to ensure that this load can be resisted without any transverse support?

See this is very bothersome to hear from the standpoint of a third party. If you have a problem with the designs come up with your own numbers to prove either yourself or Brent wrong.

See I don't have any idea at all what Brent has done form the engineering standpoint with respect to his vessels, what I can say is the tone of this thread is such that offering any up wouldn't do him any good. The problem simply being that the designs have already been dismissed without any sound engineering to back up the dismissal.

Very simple questions, simple enough calculations that should be adressed for every ocean going vessel.

I'd be willing to suggest that ocean going vessels have been around a lot longer than those calculations.

Then there's other very basic calculations like COG, GM, Vanishing angle, roll period, dellenbaugh angle that will all tell a prospective a lot about the boat thay are considering. Do you even furnish that information ? In Europe they have found a need for people to be informed so that they are not taken in by marketing hype and can judge a vessel in comparison to other vessels on the 'numbers'.

Conversely you end up with a lot of people pouring over numbers that they have no hope in understanding. Of course a lot of that depends on your customer.

Every client I have these days wants a rollover stab curve and knows what to look for on them. Sailors are becoming better educated and it seems to me that a designer who spurns education so vocally is not shooting himself in the foot but blowing one of his legs off.

Yet with all this so called engineering going into modern boats we still have them going down at sea at regular intervals. Certainly that has a lot to do with the sailor, but is also could have a lot to do with very well engineered boats that are useless on the open water.

In any event I still get the impression that the effort here in attacking Brents designs has nothing to do with the boat but rather an attempt to protect or enhance the image of the Nautical Engineers here. Sorry if that is a little too blunt but one has to realize that in the history of seafaring the type of engineering you are looking for is relatively new to the small boat owner. Even where such parameters are offered up doesn't ultimately imply that the ship itself is structurally sound or will survive heavy seas.

Dave

[MikeJohns]

Dave

Thanks for your thoughts. Interesting that you too seem to adopt this idea of duality between 'adequate' design and engineering practice. I don't think their is any duality at all.


Firstly please note that Brent has been making the statements that have been challenged. Sometimes the best way of illustrating a misunderstanding or to get someone to think is to ask a question.

If you read my posts you will see I have not been attacking his designs but I have been trying to engage in discourse over his methodology and his understanding of both structural mechanics and its relationship to boat design. I have even posted several times that I think his smaller designs may even be compliant with scantling societies with some submitted calcs. I would have been happy to have worked on this with him for free.


I see Brent calls my last queries about assumed design loads "naive". Notice that this is the usual standard of his reply, he has given virtually no information at all. This is a shame as I said I would have liked to analyze his designs. However so far his response to every specific query has been a sideways jump.

If you conduct what is called a transaction analysis You will find sufficient in his posts and the replies here to find that he has been treated fairly . I'd even suggest he creates the conflict as a way of dealing with some of the issues.


If you want me to comment on your observations of frequent vessel failures and the role of the engineers therein you will have to be more specific. There are many valid reasons why vessels founder, break-up, lose keels etc: Shipping owners exceed the design life, racing boats cut the reserve strength for the rewards of low weight, Masters don't read their vessels stability books.... whatever. But it's an intuitive leap to lay the blame on engineers .

I am not going to defending Naval architecture further and I am not being patronizing but you really don't appear to understand it at all which is apparent from your comments.
For example it is perfectly acceptable to base engineering calculations on the loads that have been identified through experience. They are not mutually exclusive. I said before we can accurately enough predict structural response but the load we design to in a dynamic environment is the bit where observation plays a key role. Did you read those posts ? EDIT [ yes you did you even quoted it in your first post]

You will also apparently be very surprised just how informed many sailors are these days.

Also I will repeat again:
It is always up to the designer to show that their design is safe and sensible in a hazardous environment. You can do this by complying with scantling rules or by your own analysis.

I guess my concern is that Brent is designing by gut feel and opinions. I might be wrong in this he may well be working with an engineer already and it may just be his marketing ploy to create conflict. Anything is possible. But it would be nice if he could discuss things amicably. From my viewpoint he is in questionable territory scaling a successful 26 or 36 footer up to 57 feet, and I don't think he realizes this. Maybe he does, what do you think?
Cheers

[MikeJohns]

Originally Posted by Brent Swain

................ ..........
Do you want to put your money where your mouth is and bet $5,000 that no boats of my design were ever built? Or ever circumnavigated? You don't have the huevos. By failing to take the bet, you admit that you are a liar. Your credibilty has dropped to zero.....................

Brent

Now you are really posting nonsense.

What is your game? Again those were not my statements.

Please find the post you are talking about click on the "quote" bit before writing your comment and then we all know who and what you are adressing. Alternatively quote the post number ( top right after the hash sign #----- )

Thanks

[DanishBagger]

Oh, boy, so much to comment!

[Schwarzenegger voice]I'll be baak! [/Schwarzenegger voice]

I'm back.

Originally Posted by Brent Swain

Mike
There are several pages in my book pointing out the geometric principles involved in the structural characteristics of origami hulls. I guess I was talking
over the heads of some, like McNaughton..

Don't confuse "unfounded, unexplained claims" with "over your head". It's a fatal flaw in your argumentation. Besides it's really poor form to pretend it's a matter of you being so "advanced" that naval engineers aren't capable of understanding your principles and argumentation. Seriously, as I suggested earlier in this thread, look the term "strawman argument" up, and please, puhlease, give real answers instead of this ridiculous play for the gallery.

Sorry I am unable to talk down to their level , but kindergarten was along time ago.

When you get off the ferry in Nanaimo start walking south. Behind Muddy waters pub, you'll find two of my designs, Viski and a 31 footer. Further down at Newcastle marina , you'll find a couple more , Serafina and Puna. At the yacht club you'll find another 36 footer. In the harbour there were 4 anchored out the last time I was there. Some may have gone cruising. Being debt free, they are free to do that.

Claims, claims and more claims.
The thing is, even if it's true, that does in no way mean your "analysis" is right, it does not mean your designs are seaworthy, it does not mean you have done your homework. How many times must one say that before it seeps in behind that thick forehead of yours?
Further, I doubt you can conclude that because one saves a bit on the framing, then any boat of yours you see must then have owners that are debt free. That's quite a stretch. And by all means quite irrelevant to this dscussion.

In a backyard at the top of the hill on old Victoria Rd you'll find another. In Ladysmith at the maritime society you'll find another , if he hasn't gone north for the summer.

Do you want to put your money where your mouth is and bet $5,000 that no boats of my design were ever built?

Noone is saying that _none_ of your boats have been built. I already said as much. Your continued use of logical fallacies is pathetic to put it bluntly. We're saying that your claims that every which way your turn woopty, there's a Swain-design is just a claim from you - the seller. And that EVEN if it were true, it wouldn't mean your designs are inherently strong, nor seaworthy, as that is the McDonald's argument, and thus invalid.

Or ever circumnavigated?

We've been there. I pointed out to you, that even if someone did a crossatlantic in a (literal) bathtub, that wouldn't prove it was seaworthy, nor strong.

You don't have the huevos. By failing to take the bet, you admit that you are a liar. Your credibilty has dropped to zero.

We've been there too. Remember you suggested a demolition party? And if we didn't partake, it must mean you were right in all your claims? My answer was, of course, that you can bring your boats to me, and we'll have a demolition party between your steel-contraptions and my 5,5 mtr epoxy sandbagger. Then, by your logic, if you didn't comply, it must mean my boat was inherently more seaworthy and stronger than yours.
You see, one cannot make that sort of claim. It's yet another logical fallacy.
One has to wonder if it's just wishful thinking on your part, when you say it's been a long time since kindergarten …

The decks , cockpit and cabin on my boats are all 1/8th inch plate , with the stiffeners installed and welded before installing the panels in the hull , as on any other steel boat.

Fair enough (at least to me).

Loads on chainplates are far below what the hull can take( or windward shrouds for that matter).

Numbers and analysis please. Otherwise it's just yet another unfounded claim.

You can put a hydraulic jack at that pint and pump it as far as it wil go without deforming the hull in any mearureable way. I make my chainplates, out of 1/2 inch plate. The weight is negligible and there is aboslutely no disadvantage in going for a huge overkill.

There's more to "spreading the forces" than oversizing the chainplates.

Ditto for rudder fittings.

See above.

Why don't you make a sheet metal model of an origami hull and see for yourself how much stiffness you get from shape.

Everyone here believes the smaller of your boats are pretty stiff. We're worried that you think it can just be made longer and a bit wider, slap in some thicker plates and all should be well. Hence we differentiate between, say, a 30 footer and one of 50-60ft.

That will answer a lot of your otherwise naive questions.

LOL, are you calling people naïve, when you're the one that haven't been able to make a real argument, put forth some basic analysis or in any way put together something that even resembles anything real in the course of seven pages?

It only becomes self evident when you actually try to twist a sheet metal hull. The irrelevance of transverse frames also becomes self evident at that point. Try it before making anymore naive coments here. I've done several dozen of them.

I'm glad you admit your comments are naive.

Seriously, though: A "designer" who sells his designs should be capable of a little more than ad hominems, marketing speech and unfounded claims.

Originally Posted by wizard69

While a second opinion is always helpful I suspect that the average person would really be put off by some of the bull headiness demonstrated by the engineering crowd in this thread. Especially if the case was one of implementing new design methodologies.

If you think of me, I'm not an engineer. I'm a journalist here in auld Denmark.
Further, noone is, to my knowledge, saying that it shouldn't be done, we're saying that one cannot simply go by gut feeling and guess work - especially when scaling.

As a third party late to this thread the above clearly goes both ways. For example the issue of transverse structures and the relationship to hull penetrations. I've seen Brent dismissed several times in this thread with respect to that one issue but as far as I can see he is absolutely correct.

Well, if you want a real "dismissal": Then you're absolutely wrong, if you think that.
The thing is, Brent is claiming through anecdotal claims that his boats are sea worthy and _overall_ stronger _because_ some of his boats have survived "attempts at puncture". You see, one cannot extrapolate like that.

Considering the number of probably engineered ships that have in the last few years sank because of hull penetrations there is reasonable reason to believe that modern ship engineering leaves a lot to be desired. Here I'm talking about the larger ships that went down in the arctic and med.

You don't think there's a "huge" difference?

Anyway, you're extrapolating much more than the argument can bear.

Exactly. So why not analyze the boats correctly to see if there are any real problems?

Erm, because he's not willing to divulge any information, and when pointed to calculations and analysis he dismisses it as close to witchcraft.
He's not even willing to admit that there might be a problem with, say, 55-footer with no strengthening. The closest he got was saying "well, the customer can choose to strengthen it themselves," apparently suggesting that this should be done with guess work too.

In any event I'm with Brent at least in the idea that the strength of the hull is an important factor in a boat ability to survive certain sorts of unplanned exceptions.

Of course it's an important factor, but there are much more to "hull strength" than (anecdotal) puncture resistance.

In any event back to modern engineering, how much effort is put into the hulls ability to survive outside exceptions. That is collision with objects, rocks or other ships. Further more which would you rather have, a hull supported with a rigid back bone that is easy to penetrate or one without that has a higher tendency to deform?

You're buying into unfounded claim that an unsupported hull by definition is harder to penetrate than a supported one.

The fact is that a lot of very small boats are nothing more than the hull structurally. An Origami only extends the boat in size.

Eh, that _is_ actually not just a detail.

Only in the sense of what you know of and have been trained to? If such a boat was analyzed from the ground up would you feel better? Something that would likely take an engineer willing and able to throw off his preconceived notions and training.

I belive others have responded better to that than I'm capable of. But suffice to say, that puncture resistance wise, I wouldn't mind one of his smaller designs. I'm pretty sure they're good at it. However, there's much more to sailing and owning a boat, and trust one's life to it, than anecdotal puncture resistance.
But I have already adressed this earlier in this thread.

Yes it would. Again though there have apparently been several engineers posting in this thread that have offered up nothing with respect to sound engineering investigations.

How much do they have to go on. They have shown him, why it might be a problem when upscaled, and have mentioned numerous times what else to consider. However, Brent dismisses every- and anything as withcraft, because it must be good if he can sell it (at least that's his argument).

Complaining about something because you don't do it that way isn't very constructive. Instead show us some sound engineering studies that support you view as an engineer.

Sorry, but it's brent who dismisses everything, claiming that the "traditional method" is ridiculous, that the traditional method is inferior to his, and that math and science should be shunned. You see, that little last detail in his argument makes sure he can continue with his religious argumentation, but the fact remains, with that sort of claims, he better provide some analysis, and if he himself is not capable of it, he should get help to do the calculations.
And, before you or he drops in and says it cannot be done: Of course it can.

See that is what I'm hearing in this thread, to paraphrase: Origami can't be any good because we don't do it that way.
No there hasn't been anyone person saying so but the tone that comesthrough is just that.

Then you heard wrong.

[quote] A well trained engineer could easily prove either himself wrong or Brent wrong through a bit of computer time.[quote]

Well, some have actually explained some principles to him, but he refuses to listen. Even if those principles are logic. Otoh, perhaps _because_ they're logical.

But the engineers contradict that in this thread. The overall tone is that anything that moves away from structures with conventionally spaced traverses is a no no.

No, people are saying (me included), that one cannot simply remove these things blindly, and then to make matters worse, just upscale as one sees fit, equally blindly.


[Skipping a part]

Notably Brent is saying he has not had any of those spectacular failures. Now I don't have the info to say if that is true or not, what I'm saying is that the people (the N/A's) who should be able to offer up a sound evaluation of the designs aren't. By sound evaluation I mean full spectrum of modern engineering techniques including computational methods. Frankly Lloyds has nothing to do with it, as Crag Cay pointed out, not all of what is in Lloyds is based on modern principles.

As mentioned, him claiming as much is far from making the truth. But besides that, not having had a catastrophic failure doesn't mean it won't happen, or is prone to happen. Also, him claiming as much, doesn't mean that his boats are basic seaworthy.

The other rather scary bit in this thread is the idea that the only worthwhile vessels afloat are the ones designed by engineers.

Not at all. I'm not claiming that at all. And as far as I can see, noone else is.
Where are we claiming that?

Frankly that flies in the face of history where the vast majority of the ships afloat never had the good fortune of structural analysis. Even more so, as you point, many that have had the effort fell apart anyways.

Yes, and so have many boats that hadn't had proper analysis in order to remain strong enough after changes in methods.

One more thing before I go on. You seem to be obsessed with your isotropic metals and sound engineering. That is all well and good but I live right next to Lake Ontario one of the great lakes and there are still occasions of large commercial vessels going down. Mind you this isn't a massive storm in the Pacific or Atlantic either. One could make a very good argument that the success of Brents designs have more to do with the owner - builder - user mentality of building the vessel to keep ones ass intact.

Or that more people up there are prone to such things as religion, pyramid schemes, marketing speech, and yes, Brent Swains unfounded claims.
My point is, that you cannot deduct what you just did on the basis that Brent's boats are sold up there. You're making a logical leap.


[I'll wait with your second post till later]

[MikeJohns]

Ok I'll visit your first post a bit more specifically too Dave.

Originally Posted by wizard69

..................
As a third party late to this thread the above clearly goes both ways. For example the issue of transverse structures and the relationship to hull penetrations. I've seen Brent dismissed several times in this thread with respect to that one issue but as far as I can see he is absolutely correct.
Dave

Absolutely correct about what ? ..........That ships plating fails at the hard spots. We knew that, but we are discussing smaller steel hulled boats. It doesn't happen with them unless the plating is very light in relation to Displ.

Originally Posted by wizard69

In any event back to modern engineering, how much effort is put into the hulls ability to survive .......collision with objects, rocks or other ships. Further more which would you rather have, a hull supported with a rigid back bone that is easy to penetrate or one without that has a higher tendency to deform?....
Dave

Where do I start ? Collision is considered more for commercial vessels, if you commission a design it can be all important if that's what you want. Yes it can be considered or not.

I think you are a bit off the ball with the rigid comment, a sailboat needs to be rigid.

Originally Posted by wizard69

...
Only in the sense of what you know of and have been trained to? ................Something that would likely take an engineer willing and able to throw off his preconceived notions and training.

There are lots of pre conceived ideas but no-one is limited to them. Huge variation in hullforms and techniques. Consider that 'origami' hulls have been around a lot longer than Brent and the pros and cons of this method were discussed in NA literature from the early 50's. You will find that considerable boat innovation has been visited before. You are as innovative in NA as the individual.

Originally Posted by wizard69

..................
there have apparently been several engineers posting in this thread that have offered up nothing with respect to sound engineering investigations. Complaining about something because you don't do it that way isn't very constructive. Instead show us some sound engineering studies that support you view as an engineer. See that is what I'm hearing in this thread, to paraphrase: Origami can't be any good because we don't do it that way. No there hasn't been anyone person saying so but the tone that comes through is just that. A well trained engineer could easily prove either himself wrong or Brent wrong through a bit of computer time.
Dave

You are really stretching things to reach that view, look back over the posts. I suggested earlier that we could easily analyze the stress levels , Brent wouldn't have a bean of it and spent a lot of effort trying to make analysis sound inadequate.

Originally Posted by wizard69

..................
But the engineers contradict that in this thread. The overall tone is that anything that moves away from structures with conventionally spaced traverses is a no no.
Dave

Just plain wrong and qualified in the comments I made. There can be significant transverse loads. How large can you make a monocoque structure before the deflections become too great ?

Originally Posted by wizard69

..................
Frankly Lloyds has nothing to do with it, as Crag Cay pointed out, not all of what is in Lloyds is based on modern principles.
Dave

Eh? um er ...what

Originally Posted by wizard69

...
The other rather scary bit in this thread is the idea that the only worthwhile vessels afloat are the ones designed by engineers.
Dave

Who the blazes implies that ? This is not a valid observation.

Originally Posted by wizard69

..................
One more thing before I go on. You seem to be obsessed with your isotropic metals and sound engineering.

Obsessed? Because I mentioned it more than once while repeating the same stuff over and over in reply to someone who doesn't engage in discourse.

Sheesh

[Brent Swain]

My chainplates are half inch plate , tensile strengths 60,000 psi. The metal above the hole in the chainplates is 1 inch of steel or roughly 30,000 lbs tensile with a shroud of 11,500 tensile attached to it.. You claim the 30,000 tensile chainplate will break first? Duhhh!!! The base is 6 inches long attached to a total of 1/4 inch plate below it. That is a total of 90,000 lbs tensile. You claim that that will break before the 11,500 tensile shroud? Duhhh!!!
The mast is supported by a half inch plate web , three inches deep under the mast, tensile and compression strength of 120,000 lbs . You claim that will break before the three windward shrouds of 11,500 lbs each? Duhhhh!!!
The support posts taking the load from the web to the chines have a compression strength of 180,000 lbs. You claim they will break before the three windward shrouds of 11,500 lbs tensile strength?
The topsides plate has a width of roughly three feet and a tensile strength total of roughly 432,000 lbs tensile. And you claim that wil stretch diagonally before the three windward shrouds break?
To compress the hull at the chainplates the side decks have to compress inward, or be stretched diagonally.They are 2 ft wide with a tensile strength of over 180,000 lbs. To change the hull shape they will also have to stretch diagonally.And you claim my math is at fault? Duhhh!!! And yours is right? Duhh!!!
I have an ultimate stability curve which I'd be happy to post here, but I don't have access to a scanner. My boats have positive righting moment to beyond 170 degrees.
The LCB is at 5.4 stations on my 36 footer. All float exactly where they are supposed to ,as long as they follow the plans and don't put huge tanks under the pilothouse floor or under the cockpit. I'm not resposible for their unilateral decisions, made against my advice.
Prismatic coeficient is .54.
I just talked to Andy Gray who sailed from BC to Hawaii in 15 days in one of my 36 footers. I sailed my 31 to a point south of Hawaii in 14 days enroute to Christmas Island. So much for your dismal performace predictions. I did two trips from Hawaii to BC in 23 days, the first 1,000 miles to windward, not too shabby for a heavily loaded 31 ft twin keeler.
Van de Stadt has many of his designs out cruising with no transverse frames in . There are a lot more Van de Stadt designs out here than McNaughtons. Especially in Europe. So who is speaking from the most experience?
Your predictions of the extremely remote possibility of disasterous failure are like the predictions of terrorist threats. The likelihood of being killed by a terrorist attack in the US is considerably less than the matehematical probability of being killed by an asteroid . A rational person wouldn't lose any sleep over the threat of either.
Brent

[wizard69]

Originally Posted by MikeJohns

Ok I'll visit your first post a bit more specifically too Dave.


Absolutely correct about what ? ..........That ships plating fails at the hard spots. We knew that, but we are discussing smaller steel hulled boats. It doesn't happen with them unless the plating is very light in relation to Displ.

I'm not sure who in the thread was arguing about this issue. At least there is more than a little agreement here.

Where do I start ? Collision is considered more for commercial vessels, if you commission a design it can be all important if that's what you want. Yes it can be considered or not.

This is what I'm getting at, there is al sorts of ways to look at a vessel from the engineering standpoint and I suspect not all vessels get the same review and engineering effort. I'm talking about private use vessels primarily targeted at the consumer.

I think you are a bit off the ball with the rigid comment, a sailboat needs to be rigid.





There are lots of pre conceived ideas but no-one is limited to them. Huge variation in hullforms and techniques. Consider that 'origami' hulls have been around a lot longer than Brent and the pros and cons of this method were discussed in NA literature from the early 50's. You will find that considerable boat innovation has been visited before. You are as innovative in NA as the individual.

That may very well be true but I've seen response in this thread and quotes that seem to dismiss the concept out right. It does make one wonder just how much vessels that deviate even slightly from the norm are excepted by NA.

Now I understand that Nautical engineers, or for the most part all engineers are conservative by nature. That is probably a good thing but Aeronautical designers seem to be much more likely to go beyond the norm to explore new concepts. That may be a perception that isn't valid but it is one that I have.

You are really stretching things to reach that view, look back over the posts. I suggested earlier that we could easily analyze the stress levels , Brent wouldn't have a bean of it and spent a lot of effort trying to make analysis sound inadequate.

Maybe! I guess the issue here is that expecting someone to engage you at the same level of Nautical engineering as you have apparently achieved is a bit more than I expect. It is a personal thing I guess as I could imagine many a design for personal fulfillment right now but am to naive to enter in to a gainful conversation with a NA.

Just plain wrong and qualified in the comments I made. There can be significant transverse loads. How large can you make a monocoque structure before the deflections become too great ?

Would that not almost instantly become a bunch of questions that would have to be asked first. What is good for a barge that lives on a canal is not in any way suitable for a large lake.

We see this in commercial sail boats as boats of vary similar external appearance are far apart with respect to what people consider suitable for off shore.

Eh? um er ...what



Who the blazes implies that ? This is not a valid observation.



Obsessed? Because I mentioned it more than once while repeating the same stuff over and over in reply to someone who doesn't engage in discourse.

Sheesh

Ok now I lost this train of thought in this message. Brent has his personality as do all of us, I just am trying to get across what I took from this thread upon initially reading it from the very beginning. That is based on the comments of all responders not just you. I'm not about to reread the entire thread so I'm not sure if it is even worth while to continue to discuss the response that Brent got.


Dave

[MikeJohns]

So Brent you do like numbers and maths

Again it would be helpful if you actually said who you were addressing, also which vessel design you are referring to since you continually refer to your smaller successes to vindicate the prospect of larger versions and this was the concerning argument.

The shroud chain-plate compression post points were not mine but it is interesting here to consider a few points that often trap novice designers which I will mention;

Compression posts don't rely on compressive strength as much as on buckling resistance. So it is more section shape and length than cross sectional area . Chainplates are in shear as well as tension, shear strength is lower than tensile and a sensible fatigue strength is around 25% of the shear strength. Just referring to tensile strength alone is poor practice. Ditto for tensile and fatigue in higher stressed cyclic loadings .

Fatigue induced failure is exacerbated in vessels which lack sufficient global hull stiffness. This is what makes transverse support essential as the vessel size increases since the transverses prevent (or reduce) the change of shape that occurs with hogging and sagging, this same lack of global stiffness will also put much greater cyclic loads on the mast and its rigging as some GRP boat owners have found in longer boats with insufficient bulkheads.

I said to you before that Van de Staadt group has explored the 'frameless' (sans transverse) issue and found some definite limits to it's application so I am not sure why you mention them again. They do however have a transparent and professional approach neither do they market themselves as anti-establishment mavericks.

[Brent Swain]

Thanks for dropping the childish hillbilly coments.
Covin also mentioned hogging and sagging. To hog, deck plating at 45,000 lbs psi yield strength would have to stretch longitudinally a considerabl distance ,in order for a boat to hog. With 1/8th inch deck plate this would mean a yield strength of 45,000 lbs per 8 inches of deck pate, not counting the longitudinals. Zero chance of that happening. Puting transverse members across the decks would have zero effect on longitudinal stretching. To sag , hull plating with 1/4 inch hull plating in the larger boats would have to stetch longitudinally a considerable distance . With 1/4 inch plate that would mean that plate with 45,000 lbs of yield strength per 4 inches of width would have to stetch longitudinaly , not counting longitudinal stringers. Puting transverse frames across a piece of plate does absuolutely nothing to increase it's longitudinal strength. Thus transverse framing does absuolutely nothin to stop longitudinal stretching of either the hull plate or the deck plate , thus having zero efect on hogging or sagging ( or twisting). These are the exclusive domain of materials that stretch easily, like wood.
I think the figures I've given for the strength of chainplates representy a big enough overkill to match the shroud strength , with a huge safety factor.
Yes I believe a lot of rigging failures come from following mathematical calculations like those shown in Skenes Elements of Yacht Design, which advocate using ultimate tensile strength instead of yield strength, especially when using materials that work harden like stainless. I prefer to avoid using stainless to hold the mast up or for anything structural. I find that once you get more than ten feet above sea level corrosion drops of drastically and galvanizing lasts for decades.
The biggest boat I've ever built was a 47 footer, origami construction , 1/4 inch plate on the hull and 1/8th on the decks and cabin. She has since done most of a circumnavigation , west from BC to Newfoundland via the South Pacific and Indian ocean , and now cruises Portugal. No stuctural problems whatever. The owner loves her.
I ended up visiting the physio threapist several times a week and now limit my own boatbuilding to 36 feet ,for the good of my own back.
Were there structural problems with larger origami boats , they would have shown up by now. Otherwise you may as well caution people to worry about being killed by an asteroid, and expect to be taken a seriously.
Now there is an occupation for skeptics. Selling people asteroid death insurance.
My first boat was designed by the author of Skenes Elements of Yacht Design , tank tested in the Davidson lab, where all US Americas cup boats were tested. The boat was an abortion . After sailing her from BC to New Zealand and on to Fiji ,my faith in world reknown "Guru "designers was blown completely. Many have little or no offshore cruising experience, and zero boatbuilding or metal working experience.
Math has it's uses, but must always be tempered by common sense and experience. Without such it can lead to serious problems. There is much that you can never learn adequately about steel boats without getting your hands dirty building and cruising in one for several decades.
It is difficult to clearly understand the geometric pinciples involved in the contribution of shape on structural rigidity of an origami metal hull by mathematical dithering, but they become clearly self evident when you build and cruise in one for decades.
I've tried to explain the geometric principles in my book to the best of my ability, but some obviously have tunnel vision when it comes to simple geometric explanations. As a picture is worth a thousand words, simply making a model out of sheet metal , and testing the rigidity as various stages , is probably the best way for these people to come to an understanding of the principles involved. Nothing else has worked for them.
Brent

[Tad]

I really hesitate to get into this....but in the interest of general information.

As far as I know (Brent can correct me) there are three stock Swain designs. These are as shown in his book, How to Build a Better Steel Boat (pub 1994). The smallest is 26' by 8'2", displacement is 6700 pounds and ballast 1800. The mid-size is 31' by 10', 12,000 pounds displacement with 3500 in ballast. The largest boat is 35'5" by 10'6", DWL = 30'0", draft is 5'10", displacement is 17,280 pounds, 5700 of ballast.

I have the plans for the largest (35'5") boat dated 1988. I assume the plans are meant to be used in conjunction with the book. There are four sheets in this plan set. The first, called DWG 1, is a sail plan. Additional information offered includes "keel 5700 Ballast 4500 lbs." and "Sail area 600'". Drawing 2 is "Construction Plans", scale is 1/2" and it includes layout of hull plate, transom, cabinside, deck framing, keel & rudder, skeg, and midship construction sections for two versions, one with CL keel, the other with twin keels. Drawing 3 has no title and includes drawings of a main and jib sail, details of bitts and a forward lower chainplate, and a deck plan. Drawing 4 shows the fittings welded to a steel pipe mast and includes spreader fittings, etc. It does mention "All rigging 5/16" 1 by 7 galvanized high tensile"

As there is no bottom construction plan or elevation it's hard to say much about the hull stiffener layout. Hull plating is indicated as 3/16". The center keel midship section shows a stiffener layout of 8 longitudinal stiffeners, all 1" by 1" by 1/4" angle "20' long". Two of these are on the bottom plt and two on the topsides either side of CL. There are "floors 1/4" PL" indicated but number and spacing is unknown. The box keel is also 1/4" (sides) & 1/2" bottom plate and with a 3/16" top forms water tanks though there is no indication of how extensive these might be. Deck (1/8" plt) stiffeners are 1" by 3/8" FB.

The fin keel is 13'4" long and 20" at max thickness, at the root. The bottom panel scales at 4'7" wide from keel root to chine, and topsides are 2'10" from chine to deck edge. There are no bulkheads indicated.

[Tad]

Originally Posted by Brent Swain

My first boat was designed by the author of Skenes Elements of Yacht Design , tank tested in the Davidson lab, where all US Americas cup boats were tested. The boat was an abortion . After sailing her from BC to New Zealand and on to Fiji ,my faith in world reknown "Guru "designers was blown completely. Many have little or no offshore cruising experience, and zero boatbuilding or metal working experience.

Another amazing leap! One boat did not meet expectations so all yacht designer's are incompetents?

How the heck do you substantiate the claim that "Many" yacht designers have little or no offshore cruising experience? Care to produce a list perhaps? Every successful designer of sailboats that I can think of has extensive sailing experience.

[MikeJohns]

Hello Tad

Thanks for the info on the designs, perhaps we can visit these in more detail later. I would be interesed in one detail, are the stiffeners welded with one flat against the plate or standing off and bracketed?

In posts #33 and #59 of this thread Brent claims that both 50 and 57 footers have been built. If you or anyone else finds any information on these or if Brent would like to cooperate, they would be very illustrative.

Cheers


Brent
You appear a little confused about hogging and sagging.
Hogging doesn't require the steel to yield unless you are talking about a permanent deformation. I am refering to normal in-service loads within the elastic limits of the materials. Try jacking this 57 footer up by the bow and the stern and measure the midships deflection. The entire girder being the hull changes shape transversely as it is so bent. Transverses add significant rigidity because of this and you are mistaken in this regard.


I didn't call you a hillbilly I implied that you market yourself as anti-establishment maverick. I don't think this is an observation any child would have made.

[Echo6]

I have to jump in here. First off, I am an mechanical engineer, I am a member of the origamiboat yahoo group, I own Brent's book, and Alex Christie's DVD on origami boat building. I have been building an origami schooner designed by Tad for 2.5 years. Here is a picture of the boat, and you can see most of the history on my blog. Now I think it is a pretty boat with nice lines, even the chine. However, you can consider me quite biased! Structurally, it has 8 3/16x1.5" angle longitudinal stiffeners midship running approximately 3/4 of the length of the boat (no brackets). 2 above the chine and 2 below on each side. It also has a 2" sch40 pipe at the sheer where the deck joins. There are 2 deep floors with 3" flanges that span the twin keels + a couple of 3" x 1/4" flat bar transverse stiffeners between the keel floors that terminate at the chine, flanged floors for the mast foundations, flanged floors for the skeg foundation, and flanged floors for the engine foundation. There is also an integral water tank between the twin keels. The cabin tops and decks are 1/8" with 3/8x1" flat bar stiffeners with 36" transverse spacing and 12" longitudinal spacing. I calculated this out of Gerr's "Elements of Boat Strength". To do it over again I would probably space the transverse frames a little closer to cut down on local deflection. That 1/8" if thin and distorts. I haven't run any numbers on the scantlings, but it seems strong enough to me. I will not engage in any purposeful collisions with fiberglass boats however. The bowsprit might get stuck and take me down too !

Now for my take on origami boat building. I am enjoying building it, but if I ever decide to do it again I will probably go to a plate on frame boat. It will be completely computer cut and designed in 3D CAD down to the interior. All the pieces can have layout and alignment lines scored on them from the supplier. I could also have all the interior precut. With the origami boat, I am spending a lot of time in the hot Mississippi sun templating bulkheads and floors and other bits of structure to the existing hull. Yes the hull went together quickly, but I am bogged down like any other boat when it comes to things inside. I might could have used the hull surface model that Tad built to model everything and have it cut, but I don't know how close they will match. This preference probably stems from using 3D CAD at work all the time. I would probably have a better boat for the time I spent in front of the computer in the air conditioning thinking about how everything goes together.

From a home builder's perspective, I think origami is a good way to build if you don't have a lot of equipment or don't want to pay for the computer cutting. I personally think that computer cutting is money well spent. I had the hull plates, cabin sides, and cabin tops cut by computer and they fit beautifully and I never could have burned them out that cleanly.

Brent turned me on to the origami boat building method. I saw his posts and other information on the internet. I dug through the net for anything I could find on it. I wanted something a little different from his boat so I hired Tad to design my hull. Brent does have a bunch of boats out there. Here are a few I found really quick.moonflowerofmoab.com

I do think that many successful boats out sailing is an indicator of how good a design it is. It may not prove beyond a shadow of a doubt that there is not some flaw there somewhere, but life is never certain. If the flaw was really critical it would probably have shown up. In the old days I bet a lot of boats were commissioned based on the reputation of the designer/builder ie. lots of successful boats still sailing.

My 2 cents on the 55footer. I think you could do it in origami. If I was doing it though, it would probably have at least two structural transverse bulkheads. I agree that you would not want to stretch a 36' design, but you could design one from scratch with the proper strength.

This thread is a deja vu of a discussion in the back issues of the Metal Boat Quarterly.

[Tad]

Mike,

The drawing indicates welding the stiffeners with the 1/4" edge of one leg against the hull plt. No brackets of any kind are indicated. No weld spec is given either.

I came by these drawings as I was requested by an owner to design a double spreader cutter rig for the boat. This I did, she has since sailed (actually mostly motored due to lack of/contrary wind) to Mexico. I did sail on the boat, and I was happy with her performance.

I am aware of one large hull attributed to Mr. Swain's method, but I have no idea if he was personally involved. It is unfinished, approximately 50' ish feet in length, and reportedly built on Cortez Island BC a number of years back. This is a bare hull floating around Quadra Island, last seen at anchor in Heriot Bay. When I looked at this hull (years ago) it seemed extremely flimsy, but was unfinished.

[MikeJohns]

Tad
Thanks, perhaps not quite the "torture test" that Brent was referring to. It does appear that his marketing gets a little energetic at times and it is hard to know just what can be considered fact.

Jim
Thanks for such an objective view.
I tried to say to Brent before that I think overall the rapid hull construction and minimal hull materials is not such a great factor in time or money considering the completed vessel. Particularly in vessels under 36 feet where the framing can be fairly minimal.

Cheers

Great looking boat by the way.