Skiboat design, inputs ?

Discussion in 'Powerboats' started by copenhagen, May 11, 2011.

  1. copenhagen
    Joined: Apr 2011
    Posts: 22
    Likes: 2, Points: 0, Legacy Rep: 52
    Location: copenhagen

    copenhagen Junior Member

    Ok here is my 3. itteration of a design for a runabout/skiboat

    it will be a lake boat, so it wont see waves over one foot, usually no more that half and it will only be run at high speeds on calm water.

    it will be powered by a 147 kg heavu tohatsu (nissan) 140 twostroke outboard on a bracket.

    it will be made in stitch and glue on a jig (yes i know there is a slight curvature in the forward part of the hull panels but the panels are developable) it is my plan to make it in 6mm plywood with biax covering both sides, on the part of the bottom that isnt covered by the sole ill glue some 10 mm core cell foam on the back side and cover with boax

    there will be 4-5 longitudinal stringers in 9mm plywood with a flat deck glued on top, (yielding 5 longitudinal box sections covered in biax glass) this sole will be 15 cm deep and filled with foam to add rigidity

    all other components in 9mm plywood, (same lamination and construdtion as bateau.com phantom 16)

    ill add 3 longitudinal liftstrakes unless you guys explicitly warn against it

    please some input on the design (i myself think im getting there)
     

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  2. copenhagen
    Joined: Apr 2011
    Posts: 22
    Likes: 2, Points: 0, Legacy Rep: 52
    Location: copenhagen

    copenhagen Junior Member

    dont mind the waterline by the way.. havent figured out how to add the weight of the outboard yet....

    what im looking for in the way of feedback is the running surface of the boat, intuitively it seems to me that it would need a skeg or lift strakes to keep it from walking and sliding
     
  3. copenhagen
    Joined: Apr 2011
    Posts: 22
    Likes: 2, Points: 0, Legacy Rep: 52
    Location: copenhagen

    copenhagen Junior Member

    here is an .fbm file for anyone interested in commenting
     

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  4. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 471, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    How heavy will the biax sheathing be and the general laminate schedule? I doesn't appear you've accounted for slamming loads sufficiently and this hull will produce plenty.

    Can you post just the lines and skip all the pretty colors?

    My first thoughts are the bow has a lot of fullness and not enough deadrise, while the stern is better, with moderate to low, seemingly consistent deadrise. I think you should bring the curve in the chine up "quicker", which will increase deadrise forward, make the entry finer and offer the boat a better "edge" to bash through the "cushion".
     

  5. copenhagen
    Joined: Apr 2011
    Posts: 22
    Likes: 2, Points: 0, Legacy Rep: 52
    Location: copenhagen

    copenhagen Junior Member

    I just love your answers :) there is really no mistaking them is there ;-) (seriously i do really apreishiate you taking time to answer my posts)

    The lamination is 6 inch 400gr biax tape on all seams in and out, bottom and sides covered in 400 gr biax and rowing (rowing mostly to allow sanding when faring) inside onw layer of 400 biax over stringers, covered by 400 on flat surfaces with overlap, all seams fillet glued with fibre filler.

    sole filled with pu foam and floor with 400 biax on both sides, 1x1 cleats on all stations and stringers in contact with floor, all interion sides not under sole first covered in core foa, and then 400 gr biax.

    deck sanwich of 4mm ply on both sides of 50 mm consruction foam with rowing on both exterior faces.. stringers to meet transom like "hockey sticks" and back seat backrest as structural member of "boxes" like sole of hull..

    strakes in 3 in mahog placed over stringers to act as outerflange of i beam like longitudinal cleats on deck end of stringers..

    everything glued with epoxy

    i posted a quick fix (it will need alittle moving arround to get the transom true and lines straight.. but general picture...

    (is it possible to buy some engineering time to get it right before i strat cutting plywood? or should i just send you a beer??? )
     

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