Stitch & Glue design from round bilge boat design.

Discussion in 'Boat Design' started by rbkepler, Jul 25, 2020.

  1. rbkepler
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    rbkepler Junior Member

    Have a set of offsets for 8' Handy Andy by William Atkin. Been wanting to build a stitch & glue chined rowboat that fits in my truck box. My idea is to use the offsets for the transom and a midship frame to be constructed of 3/4" mahogany. Dimensions for the hull panels, constructed of 1/4" mahogany ply, will be based where the two diagonals cross and meet on both transom and frame. Does that sound dumb or wrong?

    Attached Files:

  2. bajansailor
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    bajansailor Marine Surveyor

    I can see where you are coming from here, however if you obtain the shapes of the hull panels based on the diagonals (where you are effectively regarding the diagonals as chines) then it is not going to be very accurate, because you are not taking into account the curvature of the panels.
    And the chines will probably have some curvature in them, rather than being straight lines.
    Be aware also that if you want to use 8' long plywood sheets the overall length of the dinghy might be only 7' 6" (or a bit less even) to take account of hull curvature.
    It might be easier to get a set of plans for a little chined dinghy that give you offsets (or even full size patterns) for the hull panels?
  3. SamSam
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    SamSam Senior Member

    Would that not be a perfect thing to work out in cad of some sort? Not that I would have a clue how, but it would seem that's something it would be good at.

    Also, another guess, but 3/4" and 1/4" sound heavy for that little canoe. The originals weighed something like 20 lbs or so, I thought. Nevermind, I thought it was a canoe, like the Henry J. Rushton 'Wee Lassie".
  4. rbkepler
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    rbkepler Junior Member

    Thanks. I just layed out the midship frame on paper. I now understand what you mean about missing out on the curvature of the panels. Better keep looking for the plan I need.
  5. philSweet
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    philSweet Senior Member

    You have to get a clean sheet of paper and develop the hull shape from scratch using Rabl's method. To do this, start with the middle panel using the diagonal offsets as guides, and making adjustments at the bow and transon as needed. Then develop the topsides panels upwards from the upper chine and chop at the sheer. Then develop the bottom panel from the lower chine and chop on the centerline. The keel line won't be the same as the original, and you can tweak things a little bit during the build, but the keel line and bow knuckle is what it is. In general, you can't fit a panel to the old centerline. The round build hull centerline and diagonal offsets overspecify the panel development geometry.

    You can use Freeship or other software to validate your paper design, or just build a model out of poster board, doorskin, or deadpanel stock. Freeship lets you compare the hydrostatics to those of the original.
  6. Pericles
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    Pericles Senior Member

  7. clmanges
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    clmanges Senior Member

  8. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    I designed and built a little 2 part stitch and glue dinghy 20 odd years ago - it is 7' 7" LOA, and is a scaled down version of Danny Greene's Chameleon. The 'plan' in the Duckworks link below is what I used as a reference re my design -

    Building Robbie

    My Mini-Chameleon can be built as either a one part dinghy with a midships frame, or a 2 part nesting dinghy with two frames in the middle for bolting the two halves together (it stows in 4' of length).
    I have photos of the plans I have drawn - they were drawn on A3 paper, not A4, hence the photos are not to scale, but they are fully dimensioned (albeit in mm, not inches). If you let me have an email address to send them to you (and anybody else) are most welcome to have a set of plans by email (no charge).
    I will attach a photo of the first dinghy built.

    Here are a few more links re plans -

    Catspaw / Two-Paw Plans

    Boat Plans | Wooden Boat Plans | Boat Kits

    Some more dinghy plans from Duckworks -
    Duckworks has Loads of Rowboat Plans for Amateur Boat Builders

    And a free plan that can be downloaded -
    ''Fritz'' a Tender

    I know that the Atkin dinghy has a pointy bow, but he has to be fairly tubby then to get the necessary volume of displacement, hence why most small row boats now seem to be pram types with bluff bows.

    If Duckworks are selling the plans for the full size (10' 4") Chameleon (they only mention that the plans are available from Danny, but he is no longer in Bermuda), and this will fit in your truck either full size or nested (overall length when nested is 5'4") I can recommend this design, based on the smaller version that I built.

    My Mini Chameleon is fairly light weight, and rows like a dream. It is ideal for one person, but can take 2 - I have had 3 people (about 360 lbs) in mine once, but we only had about 4" of freeboard.....
    I have built 3 of them (I took a mould off the original one, and then built two GRP versions), and have supplied plans to a couple of pals who have also built boats for themselves.

    If you would like to have a copy of my plans, you are most welcome.

    Martin's Mini Chameleon.jpg
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