Coastal Cruiser

Discussion in 'Boat Design' started by Guest625101138, Oct 25, 2007.

  1. harry tams
    Joined: Mar 2006
    Posts: 36
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    Location: tasmania

    harry tams Junior Member

    That is a very beautiful little camper. I like the galley using the wonderful out doors. It would work for some but it would not be for me. It's just too small.

    Your idea regarding hatches for additional headroom has a lot of merit. The pop-up roofs on many recreational camping vehicles demonstrates the desirability of low profile to reduce windage and conserve fuel.

    A well sealed pop-up could also provide stiffness to large panel that creates the deck thereby eliminating some of the framing requirements or thickness of materials used... it might not even add to the weight.

    To keep the cost way down (4HP is about 20kg and $1500), it sure would be nice to be able to use a small out board. Could a more effective prop be created to enable this option?

    Harry Tams
     
  2. harry tams
    Joined: Mar 2006
    Posts: 36
    Likes: 0, Points: 6, Legacy Rep: 10
    Location: tasmania

    harry tams Junior Member

     
  3. harry tams
    Joined: Mar 2006
    Posts: 36
    Likes: 0, Points: 6, Legacy Rep: 10
    Location: tasmania

    harry tams Junior Member

    Apologies. I messed up Rick's quote in the previous post. Tried to respond to each section in turn. The result? Rick has been misquoted. Sorry
    Harry tams
     
  4. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Can the 4HP be adapted to take a more efficient prop?

    Find an old SEAGULL many small units were made for pushing sailboats not tenders and swung large props thru deep gearing.

    They are insanely simple motors , so a modern Honda 4 stroke lawn mower power head might be adapted .

    FF
     
  5. Guest625101138

    Guest625101138 Previous Member

    Fred
    The biggest prop they will take is about 9". This is on the small side for getting decent thrust from a 4HP motor.

    Rick
     
  6. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 111, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    From the wicopedia,

    One main feature of a British Seagull is the gearbox and propellor combination. At first glance, they seem very primitive but due to the high gearbox reduction ratio they are capable of propelling much larger boats than might be expected. The silver Century Plus model, for example, is designed to propel a displacement hull of up to 26 feet in length.

    Couldn't find the prop size , but at least they were 5 bladed.


    FF
     

  7. Guest625101138

    Guest625101138 Previous Member

    Fred
    It seems they can take up to 10". Must be for the 6HP model.
    http://www.britishseagullparts.com/engine-propellers.htm

    I have been working on 500 to 600mm to get decent thrust from low horsepower.

    The Mars electric motor I have can be run up to 9kW. With a 550mm prop it could produce thrust around 1400N. At 4kW it can get 800N.

    By comparison a 4HP outboard with a 10" (250mm) prop could get about 400N with a nicely made 4-bladed prop. Going up to 550mm 2-bladed gets 620N.

    For a boat of this size and shape 400N would be needed to hold in a 50kt wind. You would not choose to be in these conditions but it is not uncommon to be caught out even in sheltered watered.

    Wind strength over 70kts is much less common. The windage in this condition is around 800N.

    One of the things I did not like about the yellow boat is the windage from the side. I have not worked out what strength would roll it but it would be something that needed evaluation.

    Rick
     
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