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Thread: The "13", a semi-disposable box keel boat

  1. #141
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    Default Re: The "13", a semi-disposable box keel boat

    Quite nice!

  2. #142
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    Default Re: The "13", a semi-disposable box keel boat

    Still fairing? Goodness no. I'm such a donkey bottom, I'm on the second set of foils... Ahem.

    The first were, um, full sized models.

    Great shots of the boat, by the by.

    Peace,
    Robert

  3. #143
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    Default Re: The "13", a semi-disposable box keel boat

    Quote Originally Posted by amish rob View Post
    Still fairing? Goodness no. I'm such a donkey bottom, I'm on the second set of foils... Ahem.

    The first were, um, full sized models.

    Great shots of the boat, by the by.

    Peace,
    Robert
    Mate, you gotta pay attention, half scale is where its at, takes half the time and half the materials......

  4. #144
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    Default Re: The "13", a semi-disposable box keel boat

    Weighed the "13" on the trailer this evening, came in at 280lbs, my calculations before building came in around 300lbs, so im happy with that. Should allow me to add myself and a wee bit of ballast to bring it down on its 1st waterline. We will then see if i crunched my numbers correctly for the next 4 in, which should bring her transom extension down to the water, and extend the waterline another 12in.
    Snow and minus temps again in a few days, but hopefully clear by the end of the week. Need to install some pad eyes for lashing down some concrete flooded batteries before testing righting moments.

  5. #145
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    Default Re: The "13", a semi-disposable box keel boat

    Quote Originally Posted by skaraborgcraft View Post
    Weighed the "13" on the trailer this evening, came in at 280lbs, my calculations before building came in around 300lbs, so im happy with that. Should allow me to add myself and a wee bit of ballast to bring it down on its 1st waterline. We will then see if i crunched my numbers correctly for the next 4 in, which should bring her transom extension down to the water, and extend the waterline another 12in.
    Snow and minus temps again in a few days, but hopefully clear by the end of the week. Need to install some pad eyes for lashing down some concrete flooded batteries before testing righting moments.
    This most recent bit of info about actual boat weight related to calculated weight, along with the shown waterline and intended loading for test purpose, all says a lot about the scaling – where the 13 footer is essentially a test bed for a larger boat, rather than anything in less size than the intended full scale one.

    As a 26 footer, I think it is looking good for internal ballast, with possibly a steel plate shoe.
    But gives me food for thought about usefulness as a design with only al little more in length (say, only as much as 16 ft), and in which case the cost implication of a drop keel with ballast bulb might not be a good idea.

  6. #146
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    Default Re: The "13", a semi-disposable box keel boat

    Quote Originally Posted by Lugalong View Post
    This most recent bit of info about actual boat weight related to calculated weight, along with the shown waterline and intended loading for test purpose, all says a lot about the scaling – where the 13 footer is essentially a test bed for a larger boat, rather than anything in less size than the intended full scale one.

    As a 26 footer, I think it is looking good for internal ballast, with possibly a steel plate shoe.
    But gives me food for thought about usefulness as a design with only al little more in length (say, only as much as 16 ft), and in which case the cost implication of a drop keel with ballast bulb might not be a good idea.

    It was only ever intended to be a test bed for for a 26ft design. It was only looking around since i got started that i found similar hull weight and possible loadings with some other small boats, Matt Leydons "swamp Thing" in particular, that has even less beam than the 13.
    The box should be efficient at leeway prevention off wind and at low speed, it will be interesting to see the difference , if i can accurately measure it, with a board deployed in both vertical and canted positions, should be a substantial difference between stalling angles.The fact this is intended as a "motorsailer" upwind performance is not an essential part of the design, and depending on the box performance, any additional boards might not be deemed the extra work. External steel plate on the bottom has always been the idea with option of extra internal as batteries, water and maybe even lead bricks; I will also calculate the engine as being part of the ballast as it is low and fixed.
    Is the box worth the extra hassle to build over a flat bottom in a boat this size? Maybe, depending on your own needs.

  7. #147
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    Default Re: The "13", a semi-disposable box keel boat

    The snow was bang on cue, so time to organise some rigging details. I found if i removed the top rudder pin, my longshaft 4hp is a perfect fit.





    In "theory" the 2.5hp should have enough power to allow me a S/L of 1.8, but in the interest of science, i should probably try with the 4hp too, with some extra weight.

  8. #148
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    Default Re: The "13", a semi-disposable box keel boat

    Quote Originally Posted by skaraborgcraft View Post
    Mate, you gotta pay attention, half scale is where its at, takes half the time and half the materials......

    Yeah. Now you tell me!
    Haha.

    Peace,
    Slow Learner

  9. #149
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    Default Re: The "13", a semi-disposable box keel boat

    As a motorsailer, the box keel seems worth the cost and effort in order to accomodate the motor and shaft where their weight contributes to the stability requirement. Thinking about this a bit more…….maybe a steel fuel tank fitted into the box could have
    .Assuming the inside of the box is lined with an epoxy/glass skin, this fuel tank could be bedded into it with enough rubberized compound, in such a way as to lend some structural rigidity to the boat spine.

    Any comparison to a Leyden design overlooks the lack of a motor’s mass and bulk, or the lack of it in the case of the sharpie hull with chine runners (like Swamp thing or others), despite the roughly similar beam/length proportions.

    Useful space within the box keel has interested me for different reasons to motor placement, and any proportional reduction of beam is therefore counterproductive. Meaning, that A beamier hull with a wide box keel is so vastly different to this design of yours, skaraborg, that I would do best to focus on alternative forms.
    In fact, a L:B ratio of roughly 2:1 is more like it for me, and I am talking to John W about using some of his plans.

  10. #150
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    Default Re: The "13", a semi-disposable box keel boat

    Lug, the box certainly has advantages. At the current state of drawings, requiring as little overall height as possible and yet retain headroom, we have decided not to use the box as storage in the main accomodation, though that might change. Current thinking is to keep the structure as free of "built in" stuff as much as possible, if stuff is easy to remove it is easily serviced not in the confines of the boat, and makes it easier to keep a clean ship. I think a multi laminate sole of perhaps 5 layers, with a steel bolted steel shoe/ballast plate will be plenty stiff enough, and keep the inside free for maintenance. Built in tanks were considered, and decided against in favour of polyethylene.
    The Leydon comparison was one of similar length/beam/displacement. Not everyone wants to use a sweep or oars, and many a Paradox fitted with outboards. The extra weight back aft can be easily compensated by shifting a 15l water container up forward.
    I have more focus at present on higher L/B ratios in excess of 3, though in the smaller size size of boat that you are thinking of, that can be a restriction that might not be acceptable. Look forward to seeing what you come up with.

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