Richardw's Narrow Boat Project- PLATE THICKNESS

Discussion in 'Metal Boat Building' started by richardw66, Nov 27, 2013.

  1. Ad Hoc
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    Ad Hoc Naval Architect

    Precisely.

    In fact, I did it that way to allow both possibilities, since I had interest from other possible clients eager to build it themselves rather than pay a yard. Since the first build was being built in a yard, and they had the facilities to press. So it was/is an either or, solution.

    No...that's deadrise, not dead angle.
     
  2. richardw66
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    richardw66 Junior Member


    Summing up the lessons learnt from this thread:

    I understand a lot more now what goes in to designing a boat and if this sounds contradicting, the understanding I have gained is that I don't really understand it! I've been educated about ballast, I now understand that a boat has fixed ballast, movable ballast and variable ballast. My idea of the thread title was to unveil my concept of using thermal mass as ballast but the idea seems to have gone down like a lead balloon. I think it still merits further thought as it is essentially a composite floor made up of steel/insulation/concrete, I just need to convince a few doubters that water will not get it under the concrete and as there is no void or any way for air and moisture to get to the back of the steel plate why does it need to be accessible for inspection.

    Fuel and water tanks would be variable ballast as a result of consumption. The knock on effect I envisage with the concrete floor idea is total lack of movable ballast. The standard layout is usually to have a big water tank in the bow and the fuel tank in the stern. If I was to partition the tanks so I had left and right tanks with the possibility of pumping from one side to the other that would effectively be moveable ballast. I friends boat has the water tank in the bow on the centreline of the boat. The fuel tank is at stern to one side and the battery bank is at the other. Depending on the level of the fuel tank it is lighter or heavier than the balancing battery bank therefore he trims the boat with the sacks of coal that he carries on the roof; - moveable (and variable?) ballast!

    My intention is to be mindful of the trim of the boat as I go along and with the aid of CAD solid modelling have some idea of component weights and therefore the centre of gravity front to back and side to side. I don't use a special package dedicated package for this, only AutoCAD.

    Hull Cross Section:

    Sukisolo was right about traditional boats being designed to maximise load but he is totally wrong when he says I now have the opportunity to refine the shape. I couldn't appreciate it at first but I can now understand the format of the illustration and Ad Hoc's suggestion does look good with the chimes and slope angles and probably would cause less wash and consume less fuel BUT I have to say that one big flaw the design has it that it fundamentally fails to address the principle requirement maximum internal volume. A narrow boat hull could never be that shape however I do understand where he's coming from. The cross section will enviably be a box but I can now better appreciate that the challenge is to make slight alterations to the angles with the intention to make it look less like a box. I don't think the small amount of angle changes possible would have a significant effect on the efficiency of the hull side but I think angle changes can be taken forward and extenuated into the bow design and there they may be able to be given a physical benefit. Either way I've never seen a narrow boat quite like that so may be Sukisolo is right and that will be my opportunity achieved.

    Anyway, lots of work to do on my part playing and sketching various alternatives so things may go quiet for a while but I will be back to show progress and listen to your feed back.
     
  3. Ad Hoc
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    Ad Hoc Naval Architect

    I never said it was a narrow boat!

    The boat was designed for a client with a very different SOR to yours, ergo, different solution. His raison d'etre was for a classic Dutch barge.

    No 2 designs are the same...
     
  4. richardw66
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    richardw66 Junior Member

    Actually I have to say sorry but you're wrong there boys. I do hope I'm not trying to teach you to suck eggs here:

    The main cost of the narrow boat shell in this country is the labour, even if you use heavier thicknesses. Joining different plates together involves welding, welding is a skilled process and takes time, time is money so adds to cost. More over cutting plates down from raw material size causes wastage and therefore more cost. It is much cheaper to fold a plate and as my cross section demonstrates best to keep to overall standard raw material plate widths. Press bending the panels along the length is carried out on a CNC Press in a full batch quantity and the repeat ability between items is spot-on and the whole batch will be exactly identical to a very fine fraction of a degree. Although I have not had a boat fabricated before I have had far larger and far more complex structural fabrications put together. To my mind UK narrow boat builders are a cottage industry and not at all regulated as much as the construction, (or maritime) industry for weld testing and quality. That's why I am confident that a competent structural steel fabricator can weld a boat together.

    At the end of the day my driving force is price and accuracy and not artisanship. That probably sounds very harsh and probably is. This project will be done on a budget and all money will be accounted for and justified. If I had a million to spend and it could be done for half naturally I would spend the half, not that I will be cutting any corners.
     
  5. richardw66
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    richardw66 Junior Member

    Accept my apologies, yes you never said it was a narrow boat and of course that was also pointed out in another post.

    Honestly I really do appreciate you input, these things evolve and come round full circle. The fact is I'm stuck with a box design that has to fit within a box limitation and I'm trying to make it with standard plate sizes that don't help. That's probably why a UK narrow boat looks like if does and may be there is no other alternative.

    Once again, many apologies.
     
  6. SukiSolo
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    SukiSolo Senior Member

    With respect, I never said you cannot have a near maximum area in the midship and for a significant length. That is exactly what barges, wherries and many cargo vessels have. They do not have square box like ends unless houseboats on a permanent mooring. In fact a square end (bow or stern) is a severe disadvantage whilst turning a canal boat.

    How you persuade water (dense fluid if you like) to start to flow around the midship prism and then recover the energy expended is the key to a good design. I cannot believe you need 'living' space right into the very ends of the vessel. Ropes, anchors, fuel, tools etc all has to go somewhere. Preferably not in the main living quarters. When you draw it up, make a list of all the things you need just to operate the vessel, and maintain it. Include all the emergency stuff, maybe buoyancy aids etc. Then space plan where they will go.

    On the concrete ballast side, I am still dubious until I do the sums about differential expansion/contraction. On one project I did designing a mobile phone mast unit we had 6mm difference (potentially) in movement diurnally between 2 materials of the main housing. We decided to design it to drain moisture out
    of the enclosure but keep it as weatherproof as possible. Worked just fine, and I see them most days....

    Mostly ACAD will be fine for your design work but may be a struggle with the shape as it resolves in the bow and the stern. Rhino would be a lot better for the hull itself, and it can unfold the panels ie give you the flat sheet prior to bending. It also gives limited Hyrdrostat data but is fairly quick to extract other essential hull stuff.

    I would also advise building a model prior to commencing build. If you did it at 1:10 it could even be tested for speed/drag and manoevering using corrected scale weights. All trims could be verified etc and lots of other stuff fully envisioned. If it was my project I would definitely do it for myself. I still believe in prototypes/models etc wherever possible, even with the best envisioning and designing it is nice to verify everything and maybe catch some minor unforseen item. A model with removable topsides would be an excellent tool prior to build, I reckon it would be worth every hour spent on it.

    Oh, I think you owe Ad Hoc an apology, as his design allowed for both pressing the panel and or welding. Part of his good thinking and allowing for both facilities and/or self build or cheap labour somewhere else in the world.
     
  7. richardw66
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    richardw66 Junior Member

    Suki Solo,

    I have already apologised to Ad Hoc.

    The reason for the mains understanding is that on first face post are made that seem to be not relevant to the title subject which is Canal Narrow Boats but I'm beginning to learn that people are expressing a wider opinion in order to give an example of what a certain part of a boat does by comparing if to another type of boat.

    My first impression was that what was I was being told to do on my boat but I now I'm developing an understanding for the principles and reasoning behind them and how they can or cannot be incorporated into a canal boat.

    So far as the overall design goes I think I need to resolve the midship section before progressing on to the bow as I'm sure there is a whole new can of worms to open there in another forum subject. No doubt lessons will be learnt there that will have a knock-back on the midships and that may be the case several times over.

    I too overcame many obstacles when designed telecommunication masts and hold granted international patents on the subject!! (Bragging again!)

    I have access to Rhino because one of my work colleagues prefers to use it, I've not tried it myself because the screen format just seems so different but I will make a special effort to try it out. I've used AutoCAD since version 1.2 back when it was on a 5 1/4" follow disk in drive A with another in drive B to draw on. I have used many different CAD packages in the old past but I have to admit I an totally biased toward AutoCAD, especially for what I do for a living which is essentially putting lines on paper for someone else to build from.
     
  8. SukiSolo
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    SukiSolo Senior Member

    Thanks Richard. You will find Rhino very useful and the fact it will output/input stuff to it from Acad even more of a boon. Been there used Acad since Rel 9 with 2 screens etc and before that a mainframe and PC Dogs!. Will admit I don't like Acad but don't draw buildings, more products including some architectural or 'street furniture'. I have some train carriage drawings that load 3-5 times faster than Acad can do it....same drawing on same hardware.

    I have had stuff cut (CNC) including 4m dinghy, printed (lost wax) for casting, stereo lithographed etc from Rhino with no problem at all. The neat thing is it will take in via DXF or DWG and you can use the lines/curves though if splines I would tend to recreate in Rhino. It (Rhino) is designed to be easy for Acad users to grasp, which is so so to me but it is the easiest 'hard' NURB modeller out there still. I've been using it since before Rel 1.0 ie pre production Betas.

    I think the posts on here have been helpful and you are gaining a little more insight into the design of your canal boat. It is a bit like anything, naval architecture has its own ways of drawing and designing, aerospace another, architects their way etc. Some extremely good people have in-putted to this thread so it is wise to learn from them. You will not need all the possible equations and formulae to get a good hull form but you will need a few simple ones. We still wish the best outcome for this project.
     
  9. waikikin
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    waikikin Senior Member

    Richard, what you've proposed in using a steel fabricator is sound, much of your Narrowboat to a degree is much like the body of a tip truck although with framing to the inside. Boats generally besides the "romance & traditions" are really just funny shaped boxes engineered to cope with anticipated loads that make their way on the sea or water.
    Having said that... sometimes metal fab & composites fabrication businesses will take on a boat project & vow to never again, maybe they have the business head screwed on & lack the compassion to deal with leisure boat owners emotional decisions! Thing is tip trucks.. & working barges the owners need them to earn a living, leisure boats not so.
    One thing that sets a good builder or fabricator apart is their finish detailing, I work with boilermakers, some are just plain happy to squirt something together & walk away dags & all, others will carefully position & prep & appropriately grind to a neat standard, use of folds & inserted rounds & geometrics will make a steel vessel so muck kinder to it's operators & passengers & the insertion of staino wear interfacing to bollards/ fairleads & similar a nice touch, some of these cost very little extra but add greater value.
    Jeff.
     
  10. petereng
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    petereng Senior Member

    Hi Richard,
    I've read most of this thread and I'm wondering why you have not consiodered fibreglass? A simple mdf mould and you are away? No corrosion easy to repair (if needed) extremely tough and will be around for at leat 50 years with no maintenance?

    Regards Peter s
     
  11. richardw66
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    richardw66 Junior Member

    Peter,

    I have to apologise to you in that no, I never considered building a boat in fibre glass for the reason that it will be a big boat, we'll not big; long. I will not actually be building the boat myself but will put the construction out to competitive tender. Welding steel is a specialist trade and I should imagine fibre glass moulding is even more so. Therefore I believe there is a larger pool of resources for welders than there are fibre glass lay- uppers.

    Also it is not really the right material anyway, yes as you say it is repairable should it get damaged but I suspect only after the boat has been recovered from the bottom of the canal.

    If you read the other forum I have going regarding Bilge and Ballast you'll learn like I have that dimensions of a empty canal boat shell will result in a very shallow draft and whilst that may sound like a good idea for a shallow canal there is also a maximum permissible air draft otherwise the craft won't be able to pass under bridges and tunnels, therefore in order to have enough internal headroom the boat needs to have a reasonable draft.

    A fibre glass shell may be lighter than steel one but then would need more ballast to achieve the desired draft and as I've been told time and time again; ballast takes up internal volume.

    So you see there is a compromise to be had and I think a steel hull offers a better starting point in that regard.

    Well that's my answer, I trust others will no doubt beg to differ.
     
  12. richardw66
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    richardw66 Junior Member


    Jeff,

    I know exactly where you're coming from with regard to finish detailing. This is the start of a very long path of design and I thoroughly accept that the devil is in the detail. I also understand that to take path I've chosen to take on the construction with a typical steel fabricator instead of a true arts and crafts boat builder the details will need to reflect this.

    To that end this boat will be completely different to any other boat you've seen before in terms of looks. I'm not talking about the standard of workmanship to the cosmetic frills and add-ons because there won't be any nor will the final design look 'cut'.

    In architecture we have a descriptive terminology know as 'cut'. It's what happens when you have a lovely beautiful completely wholesome design for a building that looks great BUT then the 'bean counters' get hold of it and decide parts of the build are too expensive and so substitute all the good bits that make the project look like something for some inferior or cheaper alternatives in an exercise known as 'value engineering'. Usually this means paying 90% of the original cost but only getting 50% of the quality, and as we say in the trade; it looks cut!

    I assure you my boat will not be value engineered but right from the off it will be Design Engineered! Rather than have a badly fabricated detail not done by a proper boat builder I won't have the detail at all; I will just have the clean classic unmistakable lines of a narrow boat.

    Think of the old Route Master Bus and then compare it with the new one, same with the TX1 and the TX4 London Taxis, both are instantaneously recognisable as design icons as each is generically the same and yet they are different from each other in a Retro kind of way.

    So if there is such a thing as a retro narrow boat then that's what I'm trying to achieve.
     
  13. TANSL
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    TANSL Senior Member

    richardw66, perhaps because of my difficulties with English but do not understand at all the boat you want to do. But I have enough interest in such a special boat. Could you delight us with some figure of your boat?. Enough so that, at least I can get an idea, without revealing the secrets of your design. What do you want to do with it exactly, and what may have maximum draft, and what maximum strut to pass under the bridges?. Why you've decided that she can not be steel?, Do not understand the reasons you give. Would it be a solution aluminum, intermediate between the GRP and steel?. How to apply architectural techniques to design boats? Do not understand your definition of "cut" and how it applies to ships. Thanks
     
  14. SamSam
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    SamSam Senior Member

    He wants to make a Narrowboat for the English Canals that have a lot of low, narrow places with not much water depth.

    [​IMG]

    [​IMG]
     

  15. Tad
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    Tad Boat Designer

    Right at the beginning you need to figure out what you are aiming for and why? Hopefully the result will be better than these....

    narrowboat2int.JPG

    narrowboatint.JPG

    So what's the reason for the side decks? And why the tumblehome house sides? The modern aim would be to open the space up....probably with "tilt-outs" as all the superyachts are doing these days....
     
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