Realistic scantilings

Discussion in 'Metal Boat Building' started by Arvy, Jan 13, 2008.

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  1. Brent Swain
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    Brent Swain Member

    scantlings

    Friends had charter boats built to Canada Shipping Act certification using origami methods, no transverse frames. The Canadian government inspectors , when they were told that they were origami boats said "We are familiar with the method and have no problem with it." The boats passed with flying colours.
    I think the survival of my boats in extreme conitions, are far more relevant than the approval of a desk bound bureaucrat who has never sailed anywhere, never owned and maintained a steel boat for any serious length of time, or never got his hands dirty building one.
    Transverse frames greatly increase the chances of a boat being holed on sharp rocks . They are a net liability in boats under 50 feet. When a BC ferry grounded east of Bella Bella ,the only holes were right next to the frames.
    Lloyds only approves stainless for keel bolts , which are guaranteed to corode badly in such an environment. I challenge anyone with a Lloyds or any other approved wood or fibreglas sailing craft to a demolition derby against one of my unapproved origami boats. So much for Lloyds, etc.
    I built my first boat using old fashioned dinosaur methods , frames set up on a jig , stringers laid along them , then plated. What a total waste of time and effort. Thankfully I had enough steel fabricating experience to relise what a waste of time it was, and was niether masochistic enough to continue this foolishness, nor sadistic enough to impose such slavery on others wanting steel boats .
    A friend built a Laurent Giles custom steel design. The transverse framing was totaly ludicrous, the structural equivalent of putting 12 by 24 inch frames every two feet in a 45 foot wooden boat. I suggested he cut a lot of it out , which he did with no negative consequences, and a huge increase in interior volume.
    The comments being made here suggest a similar totally ludicrous type of interior framing.
    I once hitched a ride with a guy who had built the framework of a Roberts Spray. When he calculated the amount of work fitting and welding the plating on, he put the finished framework on a trailer, towed it to the dump, took the plates off the trailer , left it here and drove home . He said it was one of the wisest moves he ever made.
    I once saw a design for a tahiti Ketch which called for 4,000 lbs of framing and 1/8th inch hull plate. That is the same weight as 3/8th inch plate and no framing. When you are pounding on a rocky lee shore , plating thickness is far more usefull than 4,000 lbs of framing.
    I was once offered a job plating such a tahiti ketch famework.I told the owner that I could build a finished hull in a fraction the time it would take to plate his project and he would have a far better boat in the end. You couldn't pay me enough to get me to waste time on such futile foolishness.
    Brent
     
  2. MikeJohns
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    MikeJohns Senior Member

    Brent

    Ships have very thin plating relative to their displacement and this is not an applicable argument to lighter vessels . Framing can limit the extent of damage considerably in smaller vessels.

    Not quite right. They do approve other materials. I agree though; generally stainless is a poor choice as a keel bolt unless massively over engineered or regularly replaced.

    Why? was the boat a complete dog? If not and it sailed well and is still around then it wasn't a waste surely ?


    The construction of the hull is a relatively small proportion of the construction time overall. A well built traditional framed hull can be very durable and strong provided some rules are followed by the builder ( and a good designer).
    Framing first is neither a dinosaur method nor a foolish one, just another proven way of doing things. If the method works it is definitely not a waste of time or effort in the long run. Particularly if you end up with a more desirable hull-form with attributes not feasible in a 'Brent' type origami boat.

    They are not mutually exclusive, you can have both framing and thicker bottom plate. The principal failure mode of the plating is buckling and framing stops the buckling which allows the panel to stretch and absorb a lot more energy and limiting damage.


    I would have thought that if we limit this to chined boats that once the framing is finished the plating can proceed quickly and easily without lofting, using a simple transferred pattern.

    When compared with the very accurate loft and fit-up required for an origami hull, if the frame is completed the hard work is done already.
    I’d also note that bar frames for smaller steel chined vessels can be fabricated easily and quickly by a relative novice.

    European scantling societies are not overly conservative. When they moved work boats scantlings to leisure craft they went too far at times, some scantlings were deficient in earlier revisions and had to be increased. In such ways the rules have evolved into sensible guides that produce strong and functional vessels. You might even find that the latest ISO GL and DNV even allow for the type of designs you have perfected to your techniques.

    They may not be the enemies you imagine since Dutch yards have been aware of these techniques for many decades and have produced many smaller craft to this principle. I've seen barges built in dutch yards with a very similar technique too.

    cheers
     
  3. Brent Swain
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    Brent Swain Member

    Scantlings

    Frames don't limit dammage on small craft, they increase it. One of my 36 footers hit a sharp rock doing hull speed. It bounced off, undammaged . If it had frames the steel would have had something to stretch against and would have been holed at each frame. Aluminium river boats avoid having transverse frames against the hull skin for this reason.
    Had the stringers been set on the frames in the BC ferry , instead of notched into them , the plating would have been creased the full length without holing. A friend, starting one of my 36 footers , got the job of diving on that ferry. He was leery of his boat having no frames ,until he saw the dammage . The ferry was only holed at the hard spots made by the frames. Frames against the hull plate drastically increase the likelihood of a boat being holed on sharp rocks . Without transverse frames it simply bounces back.It is far easier to dent or hole hull plating if you hit it next to a frame, than it is hitting it where there are no frames.
    The framing I used on my first steel boat served absolutely no useful function, just made the project far more labour intensive, and heavier. Thus they were a total waste of time, time which could have better been spent using the boat for what a cruising boat is for, cruising.
    If you invent many ways to make a boatbuilding project far more time consuming and labour intensive, and these self made hinderances don't change the way a boat looks or sails , does that automatically mean they are useful? Only if the enjoyment of building the boat is the the only reason for it's existence, or maximising the number of man hours you can justify charging a client. Perhaps this is a major source of objection to my efforts to bring ownership of good steel boats within the reach of the not so rich. I'm sure livery stable owners once had similar objections to those new fangled horseless carriages.
    I have pulled together 36 foot hulls in three days or less, something you are extremely unlikely to accomplish in a backyard built framed boat.
    Attaching plate and stringers to frames before welding is a major source of distortion, which is non existent in frameless hulls, and common on framed ones. The less you do to a piece of plate , the fairer it will remain. Thus simplifying the building proccess is a good way to increase the odds of a hull remaining fair.Weld shrinkage only improves the shape and fairness of origami hulls.
    As for Dutch technology, I've sent quite a few books and sets of plans to Holland, thus introducing advanced Canadian technology to them.
    When a sharp rock hits between frames, only hull plate thickness will prevent holing. Frames only help if you are so naive as to assume sharp rocks will only hit directly on a frame. When they hit right next to one , the likelihood of a hole being punched in goes up drastically.
    It would have taken a lot longer than three days to plate that tahiti ketch and you would have wound up with a massive amount of totally useless redundant scrap metal weighing her down, as well as making the painting exponentially more labour intensive and critical.The amont of welding and grinding that remaind to be done would have been exponentialy greater.
    The only welds on a 36 ft origami hull are the centrline, two 14 ft chines amidships, four 6 ft seams on the bottom, two 5 ft seams on the bottom, bulwark caps and around the transom. One client bought a portable welder with an hour meter on it ,before beginning his 36 origami boat. By the time he launched her, he had a total of 350 hours on the hour meter for the whole project. The tahiti ketch, or most non origami boats would have been many , many times that amount of fitting , cutting and welding.
    Origami boats are far more forgiving that dinosaur methods when it comes to accuracy of cutting and fitting required.I usually let the owner do his first ever cutting on his own boat.It was never a problem.
    Many of the labour seeking atitudes toward boatbuilding are a leftover from the puritan era, puritanism being defined as "The terrible, nagging fear that someone , somewhere, just might be having a good time."
    Brent
     
  4. MikeJohns
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    MikeJohns Senior Member

    Origami boats

    Brent

    Since this forum is home to many students and is relevant to the thread it's a good topic to pursue. I'd also welcome anybody else's input on this.


    That’s a very general and unsupported opinion. I will counter it by saying that when it comes to small boats( in most scenarios I can think of) frames can considerably limit the extent of collision damage, they are also very good at conducting operational stresses and stiffening the vessel globally . You can illustrate this clearly with a CAD model and an FEA package as you can model collision scenarios. We do this routinely for specific design.

    Also consider that framing will often buckle before the plate actually ruptures which will further absorbing impact energy and limiting damage. This can be accomplished by the designer if designed for.

    Anecdotal evidence is just that and it proves nothing, for example:

    When it comes to forward collisions lots of steel boats have hit rocks at hull speed with no damage, nothing to do with how it was framed, it’s more a factor of the collision contact angle at the point of impact. If the rock projected into the vessels path and the vessel was bluff bowed it’s going to significantly dent or hole it regardless.

    Again you extrapolate extremes , ships and light alloy craft are not even in the ballpark of the vessels we are discussing. They only work as compelling arguments to a neophyte.

    This observation is just conjecture. One failure scenario I immediately envisage is that the panel buckles and the rock ‘catches’ then the tin opener effect so prevalent with ship plating would have happened anyway. How can you possibly know that this would not have happened instead ?

    Actually it takes far less energy to buckle a large panel ( buckling as in a permanent structural collapse ) than it does to stretch the material while it is restrained from buckling. Once the panel has started to collapsed it compromises all adjacent plating without frames.

    This is a point you seem to misunderstand; in an extreme event the framing stops the panel buckling allowing it to yield instead . For plating to be sheared against a transverse is possible but historically its been shown to be a non event in smaller vessels. Sure you might hit the perfect condition for a straight shear but boy….. you’d have to be unlucky. Try using a guillotine (an optimized plate shearing device) with a gap equal to say 3 plate thicknesses.

    Aren’t you over pushing this aspect (see my comment above). Smaller welded steel craft under say 35 tonnes have been common for around 60 years now in many guises; commercial military and leisure craft . They have shown that they have a remarkable resistance to being holed in underwater collisions. Sometimes I have seen fishing boats with wasted plating holed this way but often enough they remained intact and watertight .

    To get some perspective in this is important, it is usual for steel boats after pounding on a rocky shore to survive dented but intact.

    Even you are trading on the well established durability of metal boats which has been established by traditional construction techniques.

    Ships are a different story. What was the plating thickness and the displacement of the ferry you are quoting I have no idea but lets say around 10mm (very generous )and 500 tons ?
    In comparison look at a 6 tonne steel vessel plated with 5mm lower plate. Looking at a single framing adjacent shear and simply sitting the vessel on a rock; the ferry plating has to cope with stresses that are not 10 times but 40 to 50 times greater. I could go on about energy of the collision since this is a dynamic event. Lets just say it is very very unlikely to happen on the smaller steel vessel even beam on, and head on its almost impossible if the stem and keel LE angles are half reasonable.



    But then don’t extrapolate this to all framed vessels for the sake of trying to market your designs. It is just not applicable in modern optimized framing based designs. You seem stuck in the past with that an over-framed Tahiti. We have actually moved on from there you know.



    What are we talking about here How do 10 bar frames and some associated stringers escalate the cost significantly ? And then you might get a hullform you really wanted rather than on that is dictated by a construction method .

    To compare recent figures for a 37 foot chined hull. At launch the hull steel including welding consumables had cost around 8% of the total expenditure and closer to 5% of the boats re-sale value. You can quickly see that both the saved cost (and time) rapidly diminish when you consider the finished vessel.

    Not quite sure what you mean here but pro built boats show no distortion while over-welded amateur built boats can be an eyesore. I suggest people take a local welding course and learn about weld shrinkage and how to compensate for it or hire a pro to assist and the problem disappears. You assist your clients as part of the package?

    There are some beautifully fair stress free round hulls rolled heat formed and welded in relatively small sections from masters of the art. They do a huge amount to the plating and the frames pull the last of it into line.

    On weld distortion ditto my prior comment.

    But what about repairs? Weld distortion is something that framing actually counters very well. We even add framing specifically for this when repairing.

    I think you’ll find that they precede you by many decades. Many barges were built on a flat floor, plating first and then framing and they pulled the plates together to form the hull prior to framing . Many of their smaller sailing boats so built were essentially frameless with a bulkhead integral tanks and deck beam brackets the only side stiffening, one such boat (with 10mm bottom plate) circumnavigated in the 50’s. Are you really unaware of this? The style and limitations of these sorts of hulls did not suit the market and they did not become commonplace again in Holland until VandeStaadt re-adopted some of the methods for smaller lightweight sailboats.


    This is your reply to the comment that it would have been quicker to plate an existing frame
    The point was that you have to loft the entire side then cut it so that you can pull a seam together and get a uniform gap before it’s stitched up so precision is very important and it will take longer and be harder to achieve than plating an existing and complete chined frame that can be done in what 8 plates total ?

    What percentage of the time of the construction of the whole vessel are we actually addressing? I would suggest 1% or less. Is that really significant? People can actually really enjoy the framing stage and hone their welding skills prior to tackling the plating.

    People who want tobuild their boats, usually have a very definite idea of what they want and framing is a strong durable sensible and very well proven construction method no matter what you say.

    Origami boat building appears to be a fast way of producing a hull consisting of bottom and side plating but sans deck. Presumably you then have to fabricate and add deck beams before plating the deck?
    Ring frame methods lend themselves to quite rapid deck building while I can see that this is the point that the frameles origami style will suddenly bog down to conventional speed (or even possibly slower)……….is this correct?

    Also the significant flaw is that this method you push is severely limited to certain hull-forms in it’s suitability. Many people want something different and they will need to use conventional/modern framing techniques since there is no sensible alternative. There is absolutely no benefit to you to continually claim otherwise (that I can see) .

    When I get time I’ll post some computer simulations of modes of failure which should be illuminating. To be meaningful I need to know your designs maximum unsupported panel width length and thickness.

    Here's an example of the type of study we can do. As a predictive tool it's very close and it saves all that destructive testing we used to do :)
     

    Attached Files:

  5. Brent Swain
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    Brent Swain Member

    Yes, I'm sure it's a lot of fun doing things the hard way when someone else is paying you by the hour to do it. More time= more pay , at someone elses expense.
    The implication that all cruisers can afford to hire a so called professional to take a long tedious outdated method to build you what he decides you need, is elitist, and an insult to low income people who want to get off the treadmill.
    Take a sledge hamer and hit a framed boat next to a frame . It will dent easliy Take a pickaxe and you will punch a hole it, it. Hit it away from frames and it will dent far less and probably not be holed.
    Welding plate to frames , then doing the longitudinal welds will cause distortion between them.
    Not every cruiser can afford to hire you to take your time , paid by the hour to get her perfect. With origami building techniques, shrinkage of longitudinal welds simply forces more compound curve in the topsides, reducing distortion.
    Take a sledgehamer and pound next to a frame on a lightly plated framed hull . It will dent easily. Hamer betwen frames and it will be much harder to make the same dent.
    All my decks are done origami style , which lets me fabricate and install allthe decks on a 36 footer in 8 hours. It lets me weld all the beams and stringers on a workbench before installing them ,eliminating a lot of overhead welding. Try it.
    Most of the framing distortion in amateur built boats is from welding the hull to frames, then doing the longitudinals.With origami building, welding shrinkage simply forces more compound curve into the topsides plate making the hull even fairer.
    Origami boatbuilding is a lot more forgiving in terms of the accuracy required than framed construction. Give or take an inch doesn't make much difference in the finished boat.
    I think you should read my book so you will have a better understanding of the matter.
    My current boat cost me $4,000 to get launched. To get her sailing , and liveable took another $2,000. $4,000 is definitely not 5% of $6,000 unless we use your mathematical skills.
     
    Last edited: May 9, 2008
  6. Brent Swain
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    Brent Swain Member

    When I try to post on this site , I keep getting logged out every a couple of minutes. Sorta kills ones enthusiasm for continueing on this site. Does this mean that when you say anything that someone doesn't agree with it gets erased?

    Brent Swain
     
  7. Brent Swain
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    Brent Swain Member

    When your computer models tell you one thing and a boat pounding in 8 ft surf for 16 days tells you another. I'll take the pounding test over your computer numbers.
     
  8. Brent Swain
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    Brent Swain Member

    Length of the panel in a hard chine boat is the distance between chines or chine and deck or chine and centreline, a distance that is supported by longitudinals , which being portions of arcs , have to be compressed longitudinaly rather than simply bent ,as is the case with straight transverse frames..Got cut off again. Someone is obviously trying to silence me on this subject.
    It is obviously far easier to bend a relatively straight frame than it is to compress a longitudinal on end , especialy when it is welded along a curve.
    I'm of to another site.See ya when I see ya.
    Brent Swain
     
    Last edited: May 9, 2008
  9. Brent Swain
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    Brent Swain Member

    With a steel boat many of the details are simply fabricated out of hull scraps and scrap stainless which are welded down ,eliminating a huge expense that fibreglas boats experience. Thus the finished steel work on a metal boat is a lot more than a shell of a fibreglass boat .Anchors that cost the fibreglas boat builder hundreds of dollars are simply welded out of left over hull scraps.
     
  10. MikeJohns
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    MikeJohns Senior Member

    Brent Swain Origami Boats

    I thought this was principally about owner builders, that’s what I’ve been talking about anyway.
    Hiring an experienced welder for 2 days and budgeting that into the cost and it may be worth working 5 days on the treadmill to pay someone like Murielle to come and do it.

    This goes for any stiffener, longitudinal frame, transverse frame, floor, bracket etc in contact with the hull plate, but you are not going to do this unless using plating that is woefully lightweight.

    Any realistic scantling that I would recommend and you would hardly mark the paint with either a sledge or a pick. Go into your garden and put a pick axe through 5mm plate sitting on the ground and post the photo. You’ll need some special powers and a matching cape.

    Now take a wrecking ball equal to the mass of the hull , restrain the hull and swing it. Then assess the result and you will understand controlled and uncontrolled collapse and just what framing can do. You saw the photo of the steel yacht hit by the freighter in the Canary Islands.

    Some boats are specifically designed for collisions , it should come as no surprise that they have plating supported by significant and closely spaced framing.

    Which is why it’s recommended to weld the longs first and them the transverses.

    Ditto above

    But with flat bar chine ring frames they can all be welded before hand, including the deck beams. Plating is then a very simple affair. No where near as hard as you are trying to paint it. For you to make fair comparisons compare your method to a modern VandeStaadt (they produce very quick easy built hull designs) rather than one particular design of old.

    This is ok if the error is faired gently into the curve, but you cannot have this sort of error as deviation from any pair of lines to be joined without some very poor consequences. This means the lofting will need to be accurate (to define a welding gap) in this regard and it will always be quicker to plate the existing chined frame that you were talking about.

    I have not been questioning your method or your designs , I am questioning your vocal opinions and comments attacking methods which don’t suit your marketing paradigm. The whole ‘framing is obsolete I have the answer’ argument.
    People come to the forum to discuss ideas. This is what we are doing.

    You are here, you wrote your book, this is a forum, I’m questioning your wisdom and you are free to explain your reasoning.

    So many self built steel hulls sit in the garden because the fun bit (the building cutting welding) is over then they find the engine,prop and shafting is going to costs more than the hull cost them to get to that stage.


    No there’s no conspiracy, have you tried contacting the moderator? If this happens it is not due to any moderation .

    I’ll take the computer simulation when it comes to failure modes and just how the plate will distort against anecdotal tales any-day. Anecdotes have a tendency to be misleading and are often misrepresented particularly when used for marketing.

    If you look around you’ll find numerous vessels have survived this sort of calamity even some smaller lightly built foam-grp vessels . The key to the level of damage is how the vessel is oriented to the incoming waves. Most hulls will cope with the pressure head and slamming load . I have seen a solid GRP vessel on rocks hit by waves every high tide stay intact until removed months later, and come to think of it even a ferro hull the same, by the same token I’ve seen holes punched in ferro boats holed after grounding just from the bump from the wash from a passing trawler . All useless anecdotes really.

    That would be the width if there are no transverses (the shortest dimension) the panel length if there is no transverse support will be equal to the whole chine.

    No …..contact Jeff if this happens it’s the computers not the people and should be easily sorted. Composing your reply offline and posting it after logging on should work fine in the meantime.

    Curvature on this scale adds very little the strength, the radius of curvature is fairly small for a longitudinal.

    But you are rather confused here:

    An inner longitudinal welded to the plating becomes a T section. If you load the plate (the longitudinal becomes the web of the T), you are not compressing it , in fact the plating shifts the neutral axis of the T closer to the outer edge of the longitudinal (even completely off it if you consider the full plating) making it predominantly a tension member, the plate is the compression member.

    For the longititudinal to be in compression it would need to be on the outside.

    Furthermore structures like this fail in buckling and the difference between the (slightly) curved and straight stiffener will be zilch to a significant impact.

    There’s a break even point where it’s worth working and buying fittings rather than fabricating them, but yes for the budget conscious builder with time on their hands (or just the desire to do it yourself) it is worthwhile.
    This is the owner builder scenario with time but limited budget that we were talking of about the hull. The other scenario is pro built which we were not talking about but that you used in the first comment.


    Brent in your favor; you are an experienced sailor and boat-builder your designs are original, you have my admiration for that.

    However if you post what appears to be misinformation expect to be questioned and be prepared to give reasonable replies. There’s no conspiracy here to silence you or make a fool of you. I have said I’m not picking on your design but I am rather being forced to defend framed designs because of your comments. You appear to have a few biased misconceptions about just how structures work. You also appear to hinge much of your argument on some fairly minor detail. That should not concern overly except to get you to stop the in the face marketing comments that another poster had already suggested that you to stop.

    Keep promoting metal boats but please get your arguments in line. There are reasoned errors and beliefs, the latter has no place in marine engineering. If views are actually based on reason then they can change eh!.
     
  11. Landlubber
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    Landlubber Senior Member

    Mike,

    Well arguemented, and engineering wise, correct.

    We have all seen "frameless" boats being built for decades now, Brent is certainly not the only one to be doing so, but he does push his barrow rather hard.

    Thank you for so politely applying another persons opinions. I would like to say facts, but it seems that we are in an ever changing world today, and maybe facts as we knew them will be modified to a new science as we speak. Have you all been following the HHO gas thread. I just love changes for the better, and we are all learning new things every day if we wish to open our eyes, but don't shut the mind.
     
  12. MikeJohns
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    MikeJohns Senior Member

    Landlubber

    The basics of mechanics of solids have changed little over the last 100 yrs, only a better understanding of failure modes . The real advances are in materials and now recently, our ability to analyse them. With isotropic materials (metals) the FEA package has been a very useful design tool and is the greatest advance so far.

    Frameless boats are a misnomer, plate has to be stiffened one way or another otherwise it will flex excessively or even collapse under load. I see that Brent actually uses longitudinal frames after pulling the hull together with this I think they have no choice since the hull is allowed to take whatever form it relaxes into after welding which will not be entirely symmetrical so any bulkhead or transverse will be highly problematic.

    You can get away with a few basic design errors in 31 and 35 foot steel boats, but if you are talking as Brent mentioned up to 50 feet I am very skeptical that this can be done without some transverse stiffeners to carry the longitudinals without the latter becoming overly large. Structural design is no place for mis-information and unchangeable opinions ...it's just materials loads and stresses, and calculations that can be checked by others.

    cheers
     
  13. Brent Swain
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    Brent Swain Member

    I switched to angles for longitudinals long ago to prevent them from falling over, or buckling. Until they do , the longitudinals, being inside the hull are under compression, and don't compare in any way, structurally ,with a flatbar longitudinal on a flat surface. Only when the surface becomes flat are they under tension rather than compresion. While curved, they are no more under tension that the stones in the bottom of a Roman arch.They are far stronger than a flat bar on a flat surface. The topsides , being sections of cones , are far stronger structurally than a flat surface and thus the only unsupported panel is the distance between the decks and longitudinals, or chines.
    The 1/8th inch plate commonly used for 30 footers is easliy dented, especialy next to a hard point, like a frame.
    I suggest any one who doesn't quite comprehend the structural stiffness given to a hull by shape , tack together a model frameless hull from sheet metal , and try to deform it. Without the decks on, it can be twisted easily. Once the decks are on it is very difficult to change the shape in any way.
    The huge structural strength of fully welded bukheads, that decks and chines, and the longitudinal curves represent are as strong structurally as anything you will find on a boat. They make transverse frames as redundant as reinforcing a steel hull with paper mache.
    I once tried to force the conic curve out of the end of a 36 footer. I cranked a 12 ton hydraulic jack rock hard without moving it in any way.
    Like a shoebox, with the lid off, it is easy to change the shape. Put the lid on and it becomes much stiffer. With a full sized hull and deck you can put your most powerfull hydralic jack on the end of a post on one chine and against the hull deck joint on the opposite side and crank it rock hard without changing the overall shape in any way. You'll only bulge the plate out locally where the jack hits it. To change the shape you would have to stretch the deck and hull plated diagonally.
    Much of ther distrust of origami boats comes from a failure to understand the geometric proinciples involved. Much of the unjustified faith in transverse framing comes from a failure to understand the geometric principles involved, and from looking at a single cross section of a boat in isolation, without considering the overall shape . The contribution of shape to the overall structural strength of an origami shell becomes very self evident as construction proceeds.
    My boats have survived so many serous poundings on lee shores , coral , rocks, collisions with freighters, barges, icebergs, etc , that you are unlikely to find one that they haven't survived. Their structural intregrity has been proven time and time again beyond any reasonable doubt. Thus doubts are clearly an indication of a lack of understanding of the principles involved.
    A friend started building a Van de Stadt 34 at the same time as I started a 36. I had the hull and decks together by the time he had the frames built. I had the entire shell built and fully detailed by the time he had the bare hull plated.
    There is no way you can do the huge amount of cutting , fitting and welding of a multi chine hull with many full length chines in the time it takes to do an origami boat.
    I do admire Van De Stadt for being one designer who took advantage of the properties of steel without being hide bound to copying wooden boat building, and thus not holding back advancement in steel boatbuilding thinking..
    Of course building any boat , origami or otherwise, you use a batten to make the lines fair. In origami all it has to be is fair, regardless of accuracy , to get a fair hull . In traditional imitation wooden boatbuilding far more accuracy is required.
    I use origami methods for hull, decks, cabins, cockpit, keels, skegs and rudders, not just the hull. They have been standard sheet metal practise since the ancient Egyptians , in fact ,for as long as sheet metal has been around.
    I have taken measurements from the chine to the hull deck joint on several of my hulls , They were symetrical to within 1/16th of an inch.
    If you take 6 square plates and join them corner to corner, then the end result cannot be anything but square. It is geometricaly impossible for them to be anything but square , as long as the original plates were square. The same principle applies to more complex shapes like hulls and decks. As long as the hull plates for one side are copies of those for the other side and the decks for one side are copies of those on the other side, and they all join up at the same relative points, it is geometricaly impossible for the resulting shape to be anything but symetrical.
    The huge expense in imitation wooden types of steel boatbuilding explains why there are so few around. They are rarely built.
    Like the livery stable owner, it is understandable that someone who has spent decades aquiring a huge amount of knowledge would not aggree with any new technology that threatens to make his vast acumulation of knowledge outdated and redundant. Those who cling tenaciously to outdate methods of a steel boat building are modern day boatbuilding equivalents of livery stable owners.
    As Ongola said " When a new idea comes along , it goes thru three stages. First , it is ridiculed. Then it is violently opposed, Finally it is generally accepted." Origami boatbuilding has reached the generally accepted stage , here on the BC coast, after having gone thru the first two stages decades ago. There are bound to be a few backward holdouts elsewhere in the world , where they are still at stage one or two.
    They remind me of the guy I met in Victoria who was in the government maping business. He was complaining about a guy with a computer who was scooping up all the work and putting him out of work. The solution was simple . Get a computer and learn his methods.
    Ditto modern boat building methods. Learn more modern methods, when what you have learned threatens to become redundant. It's not that difficult ,and streamiling the building procces brings the cost of building down to where you will have a much larger number of potential clients to build for. Give up the livery stable business , and learn about horseless carriages. This is the 21st century , after all!
    Brent
     
  14. MikeJohns
    Joined: Aug 2004
    Posts: 3,192
    Likes: 208, Points: 63, Legacy Rep: 2054
    Location: Australia

    MikeJohns Senior Member

    Origami boats Brent Swain

    You do keep repeating the entire mantra, much of which we have already discussed. But lets look at the more serious misunderstanding.

    Understand the difference between an arch and a curved beam:
    (Apart from also apparently misunderstanding collapse under compression and just how structures achieve their strength )

    For a structure to be considered an arch you must increase the curvature to the point where the axial forces become significant. An arch has to have a very small radius in comparison with the element thickness. For the longitudinal curve of a boats hull the radius of curvature is variable, on a 36 footer it will vary along the length ballpark within what 20 to 50 feet? What are your element thicknesses, 3/16” ?
    This is just too shallow a curve by a massive factor anywhere on the hull for the thickness of the material for it to be considered anything other than a flat beam for the purposes of structural support.

    Even frames and plating on a tightly curved developed bilge are only a little better since the element thickness is so thin in comparison to the radius of curvature.

    As curvature increases you can count on going down to around 20% less material with a tight curve in plating and framing and this is counted in the Curvature coefficient applied to curved members and plating. In your case this would not even be applicable to the hull longitudinal. Also be aware that unsupported curved surfaces can Pop-through into an inverted state with little energy absorbing and no stretching from a significant collision.

    As for tension and compression you consequently misunderstand this. It would pay for you to try and grasp correctly some basic theoretical structural engineering concepts. There are also some good engineering forums where you could engage in educational discourse and try out your ideas incognito.

    I am concerned that you are looking at local impact strength but losing sight of the requirement to design the whole for a pressure head. A mid-30 foot boat is going to be forgiving with respect to these sorts of misunderstandings. A larger vessel could be problematic with your current level of understanding applied.

    Also get it into your head that modern scantlings are not hangovers from wooden boats we have moved on. Even the Van de Staadts you admire comply with class society rules.

    Do you accept the curvature information or would you like more on this?

    As for origami accuracy… yes if you loft it accurately and weld with care but then that differs with your earlier statement about lofting accuracy not being critical ; since it is your analogy try joining your 6 square faces with half an inch error in the edges and an error in the first weld angle. :)
     
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  15. M&M Ovenden
    Joined: Jan 2006
    Posts: 365
    Likes: 80, Points: 38, Legacy Rep: 527
    Location: Ottawa

    M&M Ovenden Senior Member

    Brent, you still don't seam to get that most people don't have anything against the origami building method. Most people will recognize it is an interesting method among others. As you stated (quite enough) it may have its advantages. You should also recognize that it has limitations which don't suit some peoples needs. It would be wise for your reputation to stop insulting the rest of the boat building community with your little snags about dinosaurs and horse carriages. If you opened your mind a little bit you would find out that there are good reasons why different designers and builders pick different methods and that many of those who design and build framed metal boats these days do so with some very modern technology. You seem to pick your comparisons with a fairly narrow mind. We are not all out there cutting frames with a hack saw and welding with our grandpa's sticks.
    Most of your reasons to praise origami boats are not wrong, most of some other peoples reasons to not want an origami boat are also not wrong. Can you accept that? You would do a much better job advertising your views if you did so with respect.

    On the structural argumentation, I have been tempted to jump but in but Mike has been doing a way better job than I could with a nicely structured argumentation. I have enjoyed the read. By the way, thanks Mike for offering my welding services to Brent. I'm honored you picked me, but unfortunately, we are located at opposite ends of Canada and I am fairly busy.

    Cheers
    Murielle
     
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