Help with boat building project ideas

Discussion in 'Boatbuilding' started by DonnellyShard, May 28, 2020.

  1. hoytedow
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    hoytedow Wood Butcher

    On the other hand, if it is built right, it should be crane worthy, but with at least 2, preferably 3, straps and spreaders.
     
  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Thank you Hoyte.
    Donnely, even if you are building a simple dinghy for your barge, it would be well worthwhile looking at the huge range of plans available for all types of dinghies and small craft. These wee beasties are a lot more complex than you might initially think, unless you are building a rectangular box, and even a box will need to have to the buoyancy / displacement calculated (which you were asking about how to do in an earlier post).
    Selway Fisher have plans for small craft available as well, but there are also many others out there - you have to first decide what type of dinghy / small craft you will need for your barge.
     
  3. DonnellyShard
    Joined: May 2020
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    Location: Essex, UK

    DonnellyShard Junior Member

    Thanks for the replies everyone. It is in fact a rectangular box design I am interested in doing. 13x50ft, the reason for 13ft is to keep with the marina standards.

    Flat box with a flat roof building on top. It must also be able to move with an engine or decent outboard, not that it will be but this is also so it's up to standard, not to mention if we want to move it.
    The top of it I have covered and know what I'm doing, not to mention being in a family of builders helps a lot. It's just the hull calculation. I've looked at quite a few different style barges on the yard, one 65ft in length, but it the calculation for the sides I am interested in figuring out. Some are a lot lower than others but use thicker steel and more framing. Some are larger and only use 4mm thick steel on the bottom (same thickness as our 30ft). hoytedow I will definitely figure out your explanation when I get a chance. Today has been a bit hectic.
    Our boat neighbour has just cut his 45ft hull in half down the center to try and make it another 4ft wide. But not making the sides any higher and not sure if he's taken that into his calculations at all but I will be watching his project also.
     
  4. bajansailor
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    bajansailor Marine Surveyor

    Ummm, ok, so you want a rectangular box?
    50' x 13' x (say) 2' draft gives you a volume of displacement of 1,300 cubic feet.
    One cubic foot of fresh water weighs approx 62 lbs (salt water is approx 64 lbs).
    So at 2' draft your box displacement is 80,600 lbs in fresh water, or approx 36 tons / 36.6 tonnes.
    Be aware though that no engine is going to be too happy about moving, let alone manoeuvering, a square box.
    That is why you put a bit of a pointy bow on at one end.
    And you design the other end so that water can actually flow into the area where the propeller is.
    And you get something like the Teign barge I linked to earlier.

    Re your neighbour, maybe he is going to make his hull into an assymetric catamaran? :)
    Or is the 'new' boat gong to have a 4' wide bluff bow?
    If so, he could maybe rename it the 'Aquatic Bulldozer'?
     
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  5. DonnellyShard
    Joined: May 2020
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    Location: Essex, UK

    DonnellyShard Junior Member

    Thanks for the reply. Yes it won't be pleasent to manouver but it would be from one section of mooring to the next really, no intention of bringing it through water on a journey, hence why a bit concerned a out craning a ply and fiberglass hull. Was told 3 layers of 10oz cloth and epoxy would be fine but as I said, a lot of horror stories.

    Thank you for the detailed answer, it helps alot. When you mention the draft are you talking about what's actually underwater or the full size of the side? If that much underwater then 3.5foot sides should be more than adequate I'm guessing? Weight wise sounds perfect, I don't think I will come close to that with the structure in mind plus kitchen, interior etc.

    My neighbour is very patient. How he acquired that hull was it was built around a sinking wooden boat which was placed inside of it, which he ended up scrapping. Each day over 2 years he cut it up bit by bit and put it in the boot of his car, later bringing it to the rubbish tip. Now instead of building a structure on top of his hull which was his original plan, I came in one afternoon and it was split in 2. I will take pictures if you like.
    Just makes me chuckle that this rubbish site would of had a complete boat in it lol
     
  6. Will Gilmore
    Joined: Aug 2017
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    Will Gilmore Senior Member

    A layer of ferrous oxide is often
    Especially if you don't put a keel of any sort on it. You should include in your design a keel board down the center for a little lateral resistance to prevent side slipping in the turns. Otherwise, you spin around but don't change direction. It can also aid in strength to lift with a crane.

    -Will (Dragonfly)
     
  7. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Donnelly, you might have "no intention of bringing it through water on a journey" now, but your plans might change - and it would be wise to have your boat as versatile as possible, so that it can be driven from A to B reasonably safely and without too much angst and stress incurred along the way.
    But if your heart is set on a 'house on a box', then you should be able to get some useful ideas from Eric Sponberg's houseboats (he is a contributor to this Forum, but not so often now that he is retired and off sailing around the world).
    Houseboats https://www.ericwsponberg.com/boat-designs/houseboats/

    Re the 'draft' of your box, this is the depth that is immersed in the water.
    A hull depth of 3'6" might be OK - it all depends on how much you want to load on board your barge.
    If you are building it with plywood and fibreglass, it might be easier to make the hull depth the width if a standard plywood sheet (ie 4')?
    I think that Eric Sponberg's hulls are ply and fibreglass.
    Remember that it is VERY easy to add weight to a boat, and more difficult to take it off afterwards (many people seem to have the same problem :) )
    And it all adds up very quickly.
    Re your neighbour, yes please re pictures - although rather than hijacking this thread with them, it might be easier to start a new thread, and invite comments re what he is doing?
     
  8. DonnellyShard
    Joined: May 2020
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    Location: Essex, UK

    DonnellyShard Junior Member

    Thanks for the replies. Quite a bit to consider. The website link with Eric's boats are great. I did look through his website and those houseboats are pretty much what I wish to achieve. I know what you mean by plans change with the moving of a boat but these will literally be plopped into a residential mooring, just want to be able to remove from water for maintenance and have it propelled enough to park it.

    I will ask my neighbour if I can get him to join this forum and post his boat, many of you could give him some advice on here. He seems to also be taking the plunge and trying something new.

    With the hull I want in mind now I've to decide if I want to do 4 pontoons separately like another build I've seen or one single one which will require more space and rent during hull construction
     
  9. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    In view of how your boat is very rarely going anywhere, there is no point in putting an engine on it - on the rare occasion that you have to move it, it would be easier to get another vessel to tow it.

    You said : "With the hull I want in mind now I've to decide if I want to do 4 pontoons separately like another build I've seen or one single one which will require more space and rent during hull construction"

    Re 4 pontoons 'separately', and how you are now thinking about making your houseboat in 4 modules - I just looked back at post #6 on the previous page, where you posted the 3-D drawing on a truss frame.
    Two sections (rather than 4) would be more logical - you could even build it in a catamaran arrangement, as you won't need all of the vast amount of reserve buoyancy that you will get from a rectangular box.
    You can use the house on top of the hulls as the structure to join the hulls together.
    If you have a beam of 13', you could have hulls 4' wide and 4' deep (to suit plywood panels) with a 5' space between them - if we assume a length of 48' (6 sheets of plywood) rather than 53', then at 2' draft on the hulls, each hull will have a displacement of approx 23,800 lbs or 10.822 kg.
    The two hulls together will be approx 21, 650 kg - or 21.65 tonnes.
    This should be 'do-able' - but you do not want to get too extravagant on the outfit of your houseboat, as the weight will start to increase rapidly then.

    If your length is 52' rather than 48' (adding an extra half sheet of plywood to the length), then the displacement at 2' draft will be approx 25,800 kg.

    And yes please re getting your neighbour to join the Forum, and tell us about his boat.
     
    Last edited: May 31, 2020
  10. DonnellyShard
    Joined: May 2020
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    Location: Essex, UK

    DonnellyShard Junior Member

    Thank you for the detailed reply. I think I will draw up what you suggested with 2 separate 4ft hulls. I can calculate how much weight it will be approximately finished and fitted, just need a bit of time and effort. Thinking of it this way too it would be a lot less materials, for the hull, I'm just thinking I would go with 4 layers of 10oz cloth and epoxy resin, which I think should be okay considering it will be static.

    Definitely the direction I want to go in! I'm not in a massive rush to start this so I've time to study and look at everything and get some detailed drawings going. As I said, I've knowledge on building the structure to go on top of the Hull, and have worked with fiberglass, but I've never gone as far as to making a hull. But I always like to push the boat out (no pun intended). If I could get a structure started for the hulls over winter I'd be happy, just depends how many hours I can free up to have a solid design done before I rush out and buy materials.
     
  11. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    Around here, larger boats are taken out for maintenance on an inclined railway. No crane work or lifting is done and the hull is supported on an adjustable cradle. There might be a similar setup in your area there or even a drydock.
     
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  12. DonnellyShard
    Joined: May 2020
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    Location: Essex, UK

    DonnellyShard Junior Member

    Thank you for the reply. On the yard I'm at they do in fact have some old tracks to the water but I've never seen them used. Other issue is where it is wouldn't be near where I'd be making the boat as I'd be over the other side of the yard.
    I will ask if they are used as I didn't even think about it
     
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