Where to start? - help please.

Discussion in 'Boat Design' started by Time, Jun 21, 2007.

  1. Time
    Joined: Jun 2007
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    Time Junior Member

    Firstly I'm not a designer of any sort.
    I've had a "vision", if you will, of owning a ultra slender hull trimaran. Diesel powered wave piercing.
    8.5mLOA 2.5m Beam as the max dimensions. Fully enclosed F16 styled canopy cockpit with tandem seating for 2. It would need to be very stable, strong etc etc. Sponsons connected to center hull by aero styled "wings".

    Can anyody help me to develope the dream?

    Time.
     
  2. SeaSpark
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    SeaSpark -

    Fun

    Sounds like a fun idea, some remarks:

    -Ultra slender hulls carrying 2 people and a diesel engine will perhaps have to be longer than 8.5m

    -A very stable design will possibly have to be wider than 2.5m

    -The 2.5m beam will not leave much room for functional wings on a trimaran.

    Is there a reason for the 8.5mLOA 2.5m Beam limitations?
     
  3. Time
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    Time Junior Member

    Sea spark,
    If you use "earthrace" www.earthrace.net as an example, scale it to 36% of it's size then you get a boat that is roughly the dimensions i'm after. Now i have to admit that not being familiar with scaling and it's effects on the boat dynamics, so i don't know if that is a valid proposal. But i'm happy to have it explained to me.
    If you consider that the center hull need only be 700-900mm wide to enable a person to sit in (i know thisis not much room but my glider has less room then this and is very comfortable) then you have a wing length of 80cm (i supose if extra width is needed you can simply design the wings to fold) I have no idea on stability requirements etc etc. So with that in mind lets redefine the dimensions.
    8.5m trailerable length (to allow for folding/removeable bow)
    2.5m trailerable width (to allow for folding/removal of the sponsons and wings.

    When i said "aero" styled wings i ment jus the general shape, the would be there merly as a means to attach the sponsons to the centre hull.

    Time.
    unfortunatley it's the maximium trailerable dimensions i can have.
     
  4. SeaSpark
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    SeaSpark -

    Doodle

    A cross post doodle.
     

    Attached Files:

  5. Time
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    Time Junior Member

    yeah thats' pretty close!
    Here are a few photoshop mash ups of what i was thinking...i origionally thought an outboard..but have since set myself on a diesel inboard. Obviously these images rely heavily on the earth race design but that is all i had to work with.
    [​IMG]
    [​IMG]
     
  6. Willallison
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    Willallison Senior Member

    A fundamental question has to be asked before you can establish if this is likely to be a viable concept....what do you want the boat to be able to do?
    ie - how far, how fast, for how long, in what conditions? etc
     
  7. SeaSpark
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    SeaSpark -

    Lol

    To be honest i am not an expert on powerboats and too sleepy to explain what i know about scaling in proper English hope someone passes soon who can.
     
  8. Time
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    Time Junior Member

    Well, Say we use the Australian offshore challange as the goal - hobart to melbourne (as i'd like ot use it to compete in that event at some stage). Speed is not a huge worry...more then 20 knots less then 100 knots...but less then 100L/hr (WOT) fuel consumption is a more significant bench mark.
    So to sum up and answer.
    How Far - minium 200nm max 400nm
    how Fast - crusing speed in the vacinity of 40kts
    How long - ~ 40kts for 200nm
    what conditions - Open ocean 2-3m seas.
     
  9. SeaSpark
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    SeaSpark -

    Attached Files:

    Last edited: Jun 21, 2007
  10. Time
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    Time Junior Member

    Thanks that is an intresting site!
     
  11. Willallison
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    Willallison Senior Member

    Ah - now we're talking..... I'm hoping to do the challenge in the next year or two as well:p

    For an event like that, I think you have to consider conditions far worse than 2-3 metre seas. . I was off the E coast of Tas a few weeks ago with 4 - 6 metre seas. Of more concern, they were only about 9 - 10 metres crest to crest and breaking. Very unpleasant in a small boat.
    I'd also consider a range of 200nm to absolute minimum. I know the longest leg between fuel stops is around 160nm but I'd want to allow around double that for conservative estimation in very bad conditions - so say 300.

    I have some concept sketches for a boat that I've called the monomaran. It is a very slender monohull with stabilisation provided by inflatable tubes. If you're not completely tied to the trimaran idea, it could be worth exploring. Send me a PM if you'd like to discuss it further.
     
  12. Time
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    Time Junior Member

    PM sent.
     
  13. Time
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    Time Junior Member

    Here is what i came up with as a first attempt at using some modeling software...no wonder you guys get paid to do it talk about tedious...and it still looks average. i couldn't get the shapes right. Though you get the idea

    [​IMG]
     
  14. Time
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    Time Junior Member

    Has anyone any further thoughts?
     

  15. SeaSpark
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    SeaSpark -

    Subaru Impreza Monohull

    Imagine a wave piercing monohull with a surface drive connected to a Subaru Impreza engine (diesel version) and the electronics that keep the car on the road.

    Some modifications will have to be made to make the electronics keep the boat out of the air instead of the car on the road. When everything fails the bubble on top and engine on bottom will give some sort of stability.
     
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