Looking for Nordic Pram Plans... Cheap

Discussion in 'Boat Design' started by bjdbowman, Mar 3, 2018.

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  1. bjdbowman
    Joined: Apr 2017
    Posts: 57
    Likes: 1, Points: 8, Legacy Rep: 10
    Location: Florida

    bjdbowman Junior Member

    2019 Updated Design

    I am uploading some of my design ideas at this time as a progress... I have redesigned the little dingy to meet the size requirements for the following:
    1) I need to be able to carry it or wheel it
    2) it needs to fit within the bed of my pickup truck...
    3) it needs to be able to span between my cat beams and my hulls when serving as a life-raft/dingy aboard a larger boat.
    4) it needs to be able to be used to transport materials from the dock to the cat.
    5) it needs to be able to be sailed... I need to work on a sail plan...

    Capacity should be about 500 pounds while weighing less than 50 pounds.
    Needs to carry a small outboard or electrical drive (<5 hp).

    9' x 4.5'
    [​IMG]

    [​IMG]

    [​IMG]

    Design length : 8.858 ft
    Length over all : 8.858 ft
    Design beam : 4.572 ft
    Beam over all : 4.556 ft
    Design draft : 0.550 ft
    Midship location : 4.429 ft
    Water density : 65.016 lbs/ft^3
    Appendage coefficient : 1.0000
    Volume properties:
    Displaced volume : 7.689 ft^3
    Displacement : 0.223 tons
    Total length of submerged body : 7.074 ft
    Total beam of submerged body : 4.039 ft
    Block coefficient : 0.4893
    Prismatic coefficient : 0.6045
    Vert. prismatic coefficient : 0.6010
    Wetted surface area : 25.204 ft^2
    Longitudinal center of buoyancy : 3.793 ft
    Longitudinal center of buoyancy : -1.034 %
    Tranverse center of buoyancy : 0.000 ft
    Vertical center of buoyancy : 0.346 ft
    Midship properties:
    Midship section area : 1.798 ft^2
    Midship coefficient : 0.8095
    Waterplane properties:
    Length on waterline : 7.074 ft
    Beam on waterline : 4.039 ft
    Waterplane area : 23.262 ft^2
    Waterplane coefficient : 0.8142
    Waterplane center of floatation : 3.733 ft
    Y coordinate of DWL area CoG : 0.000 ft
    Half entrance angle of DWL : 44.425 degr
    Transverse moment of inertia : 23.921 ft^4
    Longitudinal moment of inertia : 77.943 ft^4
    Initial stability:
    Vertical of transverse metacenter : 3.457 ft
    Tranverse metacentric radius : 3.111 ft
    Longitudinal transverse metacenter : 10.483 ft
    Longitudinal metacentric radius : 10.136 ft
    Lateral plane:
    Lateral area : 2.571 ft^2
    Longitudinal center of effort : 3.841 ft
    Vertical center of effort : 0.334 ft
    Hull characteristics above waterline:
    Lateral wind area : 8.678 ft^2
    Z coordinate of wind area CoG above DWL : 0.541 ft
    Distance from bow to wind area CoG : 2.995 ft

    Free-Ship-pram-chines-Linesplan https://ibb.co/YNr0zsR
    cad-file https://ibb.co/5R398cJ
    Free-Ship-Design https://ibb.co/p34TqSZ

    Still working on a small sail plan and I have an idea of using dual keels with small plastic wheels in the keels to be able to use the dingy as a wheelbarrow or for moving it when it is loaded down...
    I will ask this question later on... will the dual keels work with sailing? how much added drag will this be?

    Is there a way to make this design better? more hydro-efficient?

    Thanks...
     
  2. DCockey
    Joined: Oct 2009
    Posts: 4,071
    Likes: 158, Points: 63, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    Fit in the bed with tailgate down, on top of the wheel houses?
     
  3. DCockey
    Joined: Oct 2009
    Posts: 4,071
    Likes: 158, Points: 63, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    Added drag from the keels will be in proportion to their wetted area (both sides of both keels). The submerged wheels will also add drag, which could be a significant portion of the overall drag depending on the size of the wheels and associated hardware. Skate board size wheels inline with the keels probably would not add appreciable drag.
     
  4. bjdbowman
    Joined: Apr 2017
    Posts: 57
    Likes: 1, Points: 8, Legacy Rep: 10
    Location: Florida

    bjdbowman Junior Member

    David,

    Thanks... I'm still not sure about the keel ideas... I may want to use the aft center of the hull for a very small in/out drive so I'm am thinking that I want to have two off-set keels with room for a rudder or small outboard engine hanging off the transom.... with the in/out drive in place. This in/out drive idea would have to have a lowered boxed out portion of the aft hull for intake and in order for the drive to be submerged. Still toying with this as I also want to sail this and row this, just for fun and daily exercise.

    With that said, I don't want to have the wheels at the rear of the keels, but in order to balance on the wheels of the boat with a full load, the wheels will have to be somewhere in the middle of the hull (longitudinally). Now I am stumped on how to do this... I will post a new thread on wheels on dinghies. Not sure if I'm trying to get too much of my wants into one little boat.

    Thanks,
     
  5. bjdbowman
    Joined: Apr 2017
    Posts: 57
    Likes: 1, Points: 8, Legacy Rep: 10
    Location: Florida

    bjdbowman Junior Member

    In the bed, between the wheel wells is my concern, with the tail-gate down... Mr. Green, with the rope, in the garage?!?

    Thanks...
     
  6. DCockey
    Joined: Oct 2009
    Posts: 4,071
    Likes: 158, Points: 63, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    What is an "in/out drive"? That is a term I'm not familar with.

    Measure the distance between wheel houses in your pickup. Full size pickups usually have 49" or so between well houses - wide enough for 4 ft x 8ft sheets of plywood, etc.
     

  7. bjdbowman
    Joined: Apr 2017
    Posts: 57
    Likes: 1, Points: 8, Legacy Rep: 10
    Location: Florida

    bjdbowman Junior Member

    David...Thanks. I have measured my truck and have accounted for the wheel wells and sides, rim, anchors, etc... I modeled the truck in 3d and the boat in 3d to maximize the size of the boat... I may add an additional foot to the length, but I'm building a scale model first so maybe, we will see...

    Thanks again for your input... the in/out drive is short for inboard / outboard, but I am thinking of building a water jet like a PWC or Jet ski with a small electrical drive... as a test bed... That's for another thread. like the wheels.
     
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