Has anyone ever done...

Discussion in 'Boat Design' started by lewisboats, Jan 19, 2013.

  1. lewisboats
    Joined: Oct 2002
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    Location: Iowa

    lewisboats Obsessed Member

    A pram with 2 part transoms? One part very raked and the other part angled to match the side panels. I get 585 lbs displacement (salt) with just a hair over 6-1/2" draft, 10 ft waterline, 12 ft LOA, 47" waterline beam and 55" max beam. This is more than I can usually come up with using a conventional transom that would angle down to the Vee and require more rocker to keep the bottom of the transoms at or above the waterline. In this case should the first part of the transom encounter water it would not impede the progress as much as a more vertical transom but actually lift the bow like a ramp.

    [​IMG]

    Same boat with Max draft of a bit over 10.5" and a displacement of 1330 lbs

    [​IMG]
     
  2. lewisboats
    Joined: Oct 2002
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    Location: Iowa

    lewisboats Obsessed Member

    A 9 ft version with nearly the same beam dimensions drafting its maximum of 9 1/2" displaces 850 lbs... that's a lot for a 9 ft boat... and it still presents the same entry as a flat bottomed pram would at around 500 lbs displacement.

    [​IMG]
     
  3. lewisboats
    Joined: Oct 2002
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    Location: Iowa

    lewisboats Obsessed Member

    Same draft on a 7 ft X 4 ft version still yields 610 lbs displacement...that's Mom and Pop and quite a bit of grub. It does have a lot of rocker though and would be equivalent to any other pram style boat of the same length and displacement.

    [​IMG]
     
  4. Submarine Tom

    Submarine Tom Previous Member

    I had a version of the last one when I was a kid.

    What's your question?
     
  5. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

    My question is -has anyone designed a pram style boat with the transoms being divided in two...such as in the pictures-.

    So who designed the boat you had when you were a kid? I would like to find examples of boats with these kinds of ends.
     
  6. Submarine Tom

    Submarine Tom Previous Member

    I have no idea.

    It was likely a home build.

    It blew away one night.

    I probably learned more about boats on that little thing than on any other boat.
     
  7. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Steve,

    What is the goal for the 2 part transoms?
    Better performance in waves or less sinkage when overloaded?

    Personally I have never seen one but can't see it being too much of a problem to build.
     
  8. yipster
    Joined: Oct 2002
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    Location: netherlands

    yipster designer

    More tomatos in a box incurages growing cubed tomatos I guess couse I dont like prams look. A beam chine in bow and stern neighter, sorry. Displacement figgers seem ok, stability may be an issue, maybe a flatbottom? Just one mans opinion so dont take it to serious ;^P

    Edit thinking back however, my uncle had such a build rowing boat, say "my first" boat.
    later sailed a small pirat, great fun, still think my girls were rite with they should have a point
     
  9. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    Hi Yipster,
    Did the farmers in Holland in the olden days not have that kind of rowing boats?
    To enable to get an animal easy onto the boat and to get it off at the other side of the canal? He did not have to reverse the boat to get the goat or cow onto the banks at the other side. Bert
     
  10. lewisboats
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    lewisboats Obsessed Member

    Sorry I am a little slow in getting back to this. Not feeling so hot over the weekend. I actually called in sick (pretty much unheard of for me).

    I have seen quite a few prams over the years and I don't remember seeing one similar. It might just be a figment but I think that "bending" or creasing the transoms allows a non flat bottomed boat (Vee or perhaps multi-strake) transition quite smoothy to a higher near vertical "end". Most prams would have to have greater rocker to keep the point of the transom from immersing or not load it near as much. With this shape you can maintain the better manners and rowing performance or even sailing performance with it normal carrying capacity but when you really have to load it down it presents ends that are similar to a flat bottomed pram up to its theoretical maximum load... which would be quite a bit more than an equally sized more conventionally ended pram. It does sacrifice a bit of waterline length over a conventional shaped one but only about 5% or so being as you want to keep your ends fairly clear of the water when looking at optimal performance.

    Or am I full of hooey?
     

  11. yipster
    Joined: Oct 2002
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    Location: netherlands

    yipster designer

    Hi Bert, i know you like the Kaag, my dad's family, later just uncle had a small farm in Leimuiden on the river Drecht, you might know that neighborhood too? wide dyke, house on the waterside. and what a daywagers house it was. the basement was a dutch barge! someone once canaled into the dyke, sunk his barge in it and build a house on the steel hull. later a villa (pic) was build and half the land sold off in bits, no building permits tho. someone moored a tjalk on the backyard but houseboat was soon gone and the land for sale again. half a year back the house was for sale i noticed, very nice but no money here. never seen those farmers there (my uncle was actually a bicycle builder/repairer) setting over animals but all, my family too, had that model rowboats, first in wood and later in metal. i was young and those boats even without point were more fun than girls and haystacks :) so keep going Steve, planty designers do such here a dutch roeiboot square for me? a scow than ;)
     

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