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Thread: A Half-Sheet Boat

  1. #1
    Join Date
    Nov 2016
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    Peterborough, UK
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    Default A Half-Sheet Boat

    yes a boat from just half a sheet of ply - you didn't miss-read it and I didn't forget to put a 1 in there. At the beginning of the year I was looking to build a very, very lightweight boat. This may sound a bit extreme, but bear with me I have good reasons. The idea was I needed a boat light enough to strap to my back and carry up a mountain and have a go at paddling a few mountain tarns.

    I'd had a go at a 1 sheet boat last year but despite being small by boat standards it would be far too heavy and cumbersome. A quick search on google seemed to show most inflatables to be well over 10kg+, far too heavy to comfortably carry up a mountain. The specialist ones which were a little lighter cost too much to justify - although there are some amazing fold-up designs out there. However, as I have limited funds and was expecting to scrape any boat along some quite sharp rocks, delicate boats were ruled out. Also, buying a boat would be no fun at all - I wanted an excuse to make one.

    Based on some fairly crude calcs i estimated I could comfortably carry about 5kg in addition to all the normal kit - this would roughly allow for half a sheet of 3-4mm ply, 1kg of epoxy and enough fiberglass to sheath and tape the stress points.

    The hardest part of this challenge would be the design, it would have to displace my 80kg, be stable and portable. The stability would turn out to be the hardest part. when sitting the majority of our weight (~75%) is on our ass, our legs out in front make up the other ~25%. this poses by far the biggest problem: providing space for the legs in front but sufficient displacement at the rear. Over the last few months Iíve tried two designs, both successful in the sense that I floated, but rather hard to control.

    Attempt 1:
    with just a half long sheet of ply to work with i decided to go straight for maximum displacement with a vaguely trapezoidal design (while keeping it boat shaped), everything was compromised to keep the weight down to 4.5kg. I took advantage of a trip up north to give it a go and actually take it up a mountain! this worked better than i expected (i.e. it floated) but was remarkably unstable. there was insufficient room to put my feet out in front so they had to be squashed to the side in order to keep my centre of gravity as low as possible. full build pics here.






    Attempt 2:
    I went for a total re-design to improve stability, sacrificing displacement with a more canoe like boat/pointy box. The odd inverted front was done on purpose to force the LCB as far back as possible while retaining leg room. this one hasn't been up a mountain, but has been tested in a local river, weighing in at just 4.2kg. This was a massive improvement in fore/aft stability and the fully decked design meant it was much more forgiving on minor wobbles. The downside was quite a difficult launch. full build pics here.




    So after two partially successful attempts has anyone got any ideas for improvements for a third attempt ? I appreciate with just half a sheet i have to compromise on pretty much everything.

  2. #2
    Join Date
    Oct 2008
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    Walney, near Cumbria UK
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    Default Re: A Half-Sheet Boat

    Build a coracle.
    It really is quite difficult to build an ugly wooden boat.

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  3. #3
    Join Date
    Aug 2016
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    Hobart, Tasmania, Australia
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    Default Re: A Half-Sheet Boat

    Awesome. Unfortunately I'm pretty busy at the moment but I would love to have a crack at a design. It just might take me a while... Love what you have done so far. Its not an elegant suggestion, but perhaps a crude 2 part solid foam sit on top design would be easier to pull off. It would soak up some water but by then you would be walking down the mountain.

  4. #4
    Join Date
    Nov 2016
    Location
    Peterborough, UK
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    Default Re: A Half-Sheet Boat

    I did consider a coracle, but ruled it out as too delicate if there was any scrambling invloved, "Attempt 1" actually paddled quite like a coracle - much more difficult to balance than I’d expected, my hat off to those who can do it effortlessly!

    I like Al G idea - I’d never though of using buoyancy foam as a building material. Perhaps not for the whole boat, but I’m wondering if i could amend "Attempt 2" by giving it exterior buoyancy foam on both sides - something that could be removed and stored in the hull whilst its on the rucksack. The foam would also be sturdy enough to take a few knocks from sharp rocks too with minimal damage. Obviously the down side is nobody enjoys working with foam - yuk. I'll have a little play with freeship and see how much of an improvement it would make.

  5. #5
    Join Date
    May 2009
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    Fort Worth, Texas, USA
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    1,948

    Default Re: A Half-Sheet Boat

    Practice hiking with heavier weight and build a bigger boat.

  6. #6
    Join Date
    Mar 2002
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    Duncan, Vancouver Island
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    26,641

    Default Re: A Half-Sheet Boat

    I'm working on a quarter sheet boat that you wear on your feet. The benefit is that you don't have to carry them, but the downside is that you need two of them.
    There is no rational, logical, or physical description of how free will could exist. It therefore makes no sense to praise or condemn anyone on the grounds they are a free willed self that made one choice but could have chosen something else. There is no evidence that such a situation is possible in our Universe. Demonstrate otherwise and I will be thrilled.

  7. #7
    Join Date
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    Default Re: A Half-Sheet Boat

    I think the stability of Attempt 1 could be improved by attaching an extra-thick "big boss" foam swimming noodle along each side just below the gunwale.

    Do you need a boat to sit in, or could it be something you sit on top of? Do you have some time for assembly/disassembly for when you get to your mountain pond?

    When I was a teenager I built some sort of crossbreed between a boat and a raft; unfortunately I don't have a photo handy. I lined up a bunch of u-shaped Styrofoam blocks, then put a partial sheet of plywood as a bottom and some narrow strips of plywood on top to hold the foam blocks to the bottom. Then I cut a couple of plywood rectangles that I attached at the front of the raft to create a plumb bow. At the back there was a skeg that could pivot up like a kick-up rudder if I hit bottom. I paddled the thing for miles with a piece of plywood screwed to a broomstick for a paddle. I sat on a board laid across the top of the u so that my heels were about 10cm below the seat. The whole thing was probably about 50-60 cm wide and 1.5 m long.

    So along these lines all sorts of things are possible. Foam for the body of the boat and the plywood mainly on the bottom to protect it and maybe for some shape at the bow. Maybe a bit of solid wood for framing if necessary, potentially involving thwarts. You probably will need a few fasteners but not a whole kilo of epoxy. A pram or scow shape would probably work best to create a short boat with a lot of carrying capacity that you can sit inside. Or maybe a hybrid between a stand up paddleboard and a sit on top kayak will do if you don't mind sitting on top.

    Another sit on top possibility would be a number of blow-up beach rollers that you tie together as a raft with perhaps some plywood on the bottom to protect it from the rocks. However, something with a bit more of a boat shape would be easier to hold its direction when underway.

  8. #8
    Join Date
    May 2009
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    Fort Worth, Texas, USA
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    1,948

    Default Re: A Half-Sheet Boat

    Haven't you guys seen the blow up balls that you get inside?
    Absolute minimum weight, no volume to speak of, and you get to see the fish thru the bottom of the "boat".

  9. #9
    Join Date
    Dec 2011
    Location
    North East England
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    Default

    Love the idea of a half sheet boat

    Perhaps not what you had in mind but here goes

    Egg box construction foam core to a top and bottom skin of 2mm ply. The side of the core skinned with 200g cloth and Epoxy. The depth of the boat is 184mm giving a total buoyancy of 126kg and weight of approximately 6kg.









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  10. #10
    Join Date
    Nov 2016
    Location
    Peterborough, UK
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    6

    Default Re: A Half-Sheet Boat

    well I’m starting to think foam is a much more important material to this than i first envisaged..... I didn't have any "Swimming noodles" to hand, but i did have some pipe insulation - I need to think of a much better way to fix them on, but the concept kind of works, it’s like putting arm bands on a boat.


  11. #11
    Join Date
    Dec 2011
    Location
    North East England
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    675

    Default

    Amazon have these for sale at £30 inc p&p


    https://www.amazon.co.uk/Aqua-Marina...qua+marina+sup
    Mine are on the way

    Richard Woods used inflatable bags on the side of his duo dinghy, 10ft two sheet boat


    If you search about you can get thicker pipe insulation, some of my pipes are lagged with very thick stuff

    Seeing as you are hiking what about two rolled up camping mats
    This would provide 9.7kg of buoyancy per side

    Or add onto the outside bottom 50mm xps foam, give it a bit of shape and grass over with 200g and epoxy. Quick calc comes out at an extra 1.4 kg - depends on your glassing but achievable with some peel ply to help. Could be lighter if you locally hollow out the foam boat side.

    I don't post to get a response, just to record my thoughts.

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  12. #12

    Default Re: A Half-Sheet Boat

    This skin on frame design at 8lbs leaves enough weight for a paddle and a roll of duct tape! http://gaboats.com/boats/sweetpea.html


  13. #13
    Join Date
    May 2015
    Location
    Edinburgh, Scotland
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    82

    Default Re: A Half-Sheet Boat

    half a sheet is a very appealing idea but SOF seems like the solution here.. i've seen plenty videos of people hitting the skin with hammers etc - they can be pretty tough!

  14. #14
    Join Date
    Feb 2006
    Location
    Pennsylvania
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    7,705

    Default Re: A Half-Sheet Boat

    Interesting exercise. I wouldn't dismiss SOF boats out of hand as too delicate. The dacron skin specified for that 8 pound canoe is much stronger than you'd expect. The roll of duct tape is well advised, just the same! (And that gent really oughta have a life jacket.)
    -Dave

  15. #15
    Join Date
    Dec 2011
    Location
    North East England
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    675

    Default Re: A Half-Sheet Boat

    This website details 1 sheet boat that might give some ideas
    http://www.christinedemerchant.com/b...one-sheet.html

    There is also stuff on cotoplast boats which might work
    http://www.christinedemerchant.com/b...yles-coroplast

    8lb - https://youtu.be/MwYc7p_oNDg

    This stuff is cheap as chips
    https://www.sheetplastics.co.uk/prod...tic-sheeting-1

    You can even get 2mm sheet 2400 x 1200 from wickes for £3.50 which would be great for proving the design
    Last edited by tink; 09-03-2017 at 02:46 AM.

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