Richardw's Narrow Boat Project- PLATE THICKNESS

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

  1. richardw66
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    richardw66 Junior Member

    Stumble,

    The 100mm step in the side is the Gunwale and it's for walking along very carefully as you hold onto the handrail. It means you can get from the front to the back of the boat on the outside without walking along the roof and without treading dirty boots through the interior.

    There is nothing to stop you using the roof for other things and they are indeed used for general storage for sacks of coal or logs, some have planters on the roof to act like gardens and some boats have solar panels on the roof to trickle charge the leisure batteries.

    You can't put too much height on top of the roof because the boat still has to fit under low bridges and through tunnels.
     
  2. SamSam
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    SamSam Senior Member

    I wouldn't make one of fiberglass. I'm thinking material cost would be more to begin with, compared to steel.

    When these things have accidents, a lot of times the bow will get hung up on land or the lock gate, and then the tide will go out or the lock empty and the thing is supported on it's ends, spanning 40-50'. That would seem difficult to design for in glass, but maybe not.

    I think these things run into things and each other at a slow speed but with lots of ponderous, crushing inertia. If similar 'strength' plates of steel and fiberglass were subjected to a catastrophic force, such as one narrowboat t-boning another (which is probably just about impossible) glass, being brittle, will eventually fracture and leak while steel, being flexible, will stretch and deform a lot more (absorbing energy) while still remaining water tight. Steel is easier to repair. It wouldn't hurt to leave dents, they aren't affecting structure too much or water tightness at all, they can be beat back to shape or filled in with bondo.

    The deciding point though is abrasion resistance. They don't have fenders on these boats as there is no room for them. You can see both these boats have protective rub rails, but they don't match up. You know they are not going to slip into this lock with an inch of clearance all around, but will be bumping and jostling and sliding along the concrete and each other. When the water level goes up or down 5 or 6 or x amount of feet, they are grinding along the side of the concrete. A lot of the locks are rougher stone.

    [​IMG]

    Imagine what fiberglass would look like after a few trips through this set of locks, side by side with another boat. From what I read, the water doesn't come in or go out slowly in a lot of the locks, but rushes in and out, jostling and bashing the boats around.

    [​IMG]

    You can scratch paint on steel and it's not much of a problem, but scratch through gelcoat into composite and you might have to do something about it fairly soon.

    .
     
  3. SamSam
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    SamSam Senior Member

    These boats evolved from open barges, I imagine the gunnels were and still are for sideways strength at the 'sheer' line.

    Taking ideas from RVs, these things could use some slide outs as they're kind of claustrophobic and boring inside. They're mostly boring on the outside also, no provision for sitting comfortably on the decks or roofs. There is room for experimenting, innovation and improvement.

    With top clearance being sometimes critical, maybe the top foot or so of the roof could be cranked up and down like some of the RV pop-up campers.
     
  4. richardw66
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    richardw66 Junior Member

    Sam Sam,

    No, No, never ever claustrophobic or boring inside (well sometimes, but only the bad ones), but it doesn't have to be that way because the possibilities for interior design are endless even if the internal volume is a little restricted. But that only adds to bring about innovation and space saving measures so the inside of these boats can be perfect examples of practical form and function.

    Not wanting to advertise them but might want to check out Boat Brokerage ABNB's website at www.abnb.co.uk as I think they produce by far the best quality sales information and gives an idea of exactly what can be fitted inside a narrow boat. I recently viewed a boat at Whilton Marina Boat Sales called Pudding & Pie and it had a Aga Cooking range and a Victorian Cast Iron Roll Topped Slipper Bath in it.

    I can't wait to get to that bit of the design but first things first...
     
  5. Stumble
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    Stumble Senior Member

    I have been looking at a lot of pictures of these things thanks to this thread, and I keep coming away with all the wasted space on the top deck. None of these boats seem to make very good use of that space, which is a shame since it is often almost half of the total floor space. I am thinking hinged furniture, some adaption of RV awnings, and for when not passing thru narrow areas, hinged out walk ways that would allow a lot more deck space.


    From a hull design standpoint it doesn't look like there is a lot of wiggle room for design really. There is a very strict box rule in effect. I am guessing a decent NA should be able to toss together the scantlings in a few hours of time. I guess there is some debate over bow shape, possibly some stern shaping, but otherwise there isn't much work to do.

    It is the interior and living space that is going to be the hard part.
     
  6. richardw66
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    richardw66 Junior Member

    Stumble,

    Good lateral thinking; that's what I like to see.

    However the idea of fold out deck space may seem like a good idea but unfortunately in practice there is likely to be another boat moored up along side. Therefore any RV style fold-outs and slide-outs are unlikely to be practical. I've also learnt as a result of this forum that they would also add further weight at a higher level and be a lever outside the centre of gravity and the idea is to keep the boat's centre of gravity as low as possible to ensure stability.

    Interior design will all be discussed in great detail later on. I have started another thread called 'Below the Waterline' which includes a hint that this boat will have a Eco Bow that is actually going to have a curved front end and not a pointed one. Following on from what you've said above, it is my intention to make best use the outside space and use the fore deck area as an outdoor dining area with fixed seating round the outside of the bow and a table that folds up from out of the deck. Another design idea I have is to either cantilever the roof over as shelter or have a retractable RV Style awning.

    This is the very early days of the overall design that will encompass everything but first I must learn to walk before I can run. the boat needs to have a solid foundation and not be a castle build upon the sand.
     
  7. Stumble
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    Stumble Senior Member

    Think of a hinge running bow to stern along the outboard top of the boat. When at the dock, or anchor you pull lift up a walkway that is folded down inside the sheer, and add 200sq foot to the upper deck of the boat. If someone is alongside, well either lower them and the tread acts as a privacy screen, or keep them out and repel boarders. :D

    The weight penalty is going to be pretty minimal, figure 40' or 2" aluminium square tubing, and some diamond plate. It will hurt maximum stability, but I doubt that these boats lack form stability anyway. They were used to carry metal ore and coal filled to the roof, so they have to have a good bit anyway. Since the walkways are only used at rest (or slow nice days) my guess is their stability effect is minimal.
     
  8. pdwiley
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    pdwiley Senior Member

    Rubbish. How many fibreglass icebreakers have ever been built?

    PDW
     
  9. TANSL
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    TANSL Senior Member

    Minesweepers were constructed of plastic. These ships can support loads well above those of an icebreaker.
     
  10. DCockey
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    DCockey Senior Member

    What type of loads?
     
  11. Ad Hoc
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    Ad Hoc Naval Architect

    As DC notes above ..what type of loads are you referring too?

    Chalk and cheese!
     
  12. rxcomposite
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    rxcomposite Senior Member

    Although I am a proponent of composite whenever possible, the use of FRP technology won’t work for this type of design. FRP’s toughness (the ability to resist impact such as sledgehammer blows and steel balls) comes from its high strength and LOW MODULUS.

    Though an FRP Uni/polyester has the same ultimate strength as a marine grade alloy the alloy has 3.5X more modulus. Steel has a much higher modulus, 10X that of FRP. To use FRP in a high length/breadth ratio such as this would translate to a “flexible” boat that sags in the middle. To gain longitudinal stiffness, it will need unusually tall longitudinals, deep transverses, thick roofs, and numerous pillars to support the roof transverses. These bulky framings would eat up a lot of interior space.

    The only way the composite structure can equal or surpass the stiffness of an aluminum alloy is to use Advanced Composite technology such as use of epoxy resin/vinylester, high glass content, high modulus fibers, post curing, and core technology. This will raise the cost and the skill set required.
     
  13. SamSam
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    SamSam Senior Member

    Minesweepers were made of wood and plastic mainly so as not to set off magnetic mines. A grp boat might support some sort of load in excess of an icebreaker, but motoring through ice would chew up and destroy a grp boat pretty quickly.

    As far as claustrophobic and boring goes, these seem to be kind of typical of the real narrow narrowboats and the theme seems to be sit on a sofa and look at the wall.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    I've got nothing against sitting around all day but if you can only look up out of a window, I suppose looking at tree tops and clouds, forget that. I'd rather the windows be lower so you can see the water and the shoreline while sitting.

    All these things have a relatively few, small windows. The topsides don't have much to do with structural strength, what's stopping them from having large picture windows?

    So if you don't want to sit inside and look at the walls, the option is to go outside, but none of the boats have any outside decks arranged as a permanent type fixture. In the back, all you can do is stand around in a small space, in the front, you can drag out a chair and sit around in a small space.

    I would sacrifice some of the cabin space for more forward deck space. I would also put the controls up front and put the engine exhaust and noise on the backside of my ears and nose. And make some use of the roof.
     
  14. Ad Hoc
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    Ad Hoc Naval Architect

    Getting better :)

    I can't see any ref to side frames? The bottom frame of 100x10 is a bit heavy. It you made the web say 5mm and added a rider bar say 50x6mm, the weight is less, but it is stiffer. And importantly the rider gives you a nice flat for sole bearers etc. Not easy attaching soles to FBs.
     

  15. waikikin
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    waikikin Senior Member


    the dimensions do kinda limit the "rooms", maybe some mezzanine seating areas with largish hinged/pop up hatch with nice double berth under.... or mezzanine berths/daybeds, kind go split level within the box envelope.
    Jeff
     
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