cordless airboat propeller question

Discussion in 'Boat Design' started by alan craig, Jul 30, 2012.

  1. Dennis A
    Joined: Aug 2009
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    Location: Amersham bucks uk

    Dennis A Junior Member

    Cordless Air Boat

    Alan
    As I have said before, a increase of 1.5 X the prop speed will make a improvement in your boat speed but could damage the batteries in your drill. What you really need is a gear system so that the prop speed could be increased in stages.
    I am starting to build a planing boat for next years event.

    Dennis
     
  2. bntii
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    bntii Senior Member

  3. alan craig
    Joined: Jul 2012
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    alan craig Senior Member

    Dennis, you are right, but I'll take the risk based on gut feeling. Bntii, I had about 1/2 hour of cruising around which means that I was only using about 90w per drill cruising at full throttle which compares to 260w measured static per drill. As about 60w is absorbed by each drill with no load, thats a very small power to the prop when cruising. Even if I only cruised for 1/4 hour it is still very low power to the props, and the batteries were not flat at the end.

    Anyway, a friend has bored all the toothed belt pulleys for me but I'm feeling very lethargic about this and other hobby interests at the moment so I have not done the work yet. But I'll post here when I have some results,
    Alan
     
  4. alan craig
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    alan craig Senior Member

    Cordless Canoe progress 2013

    Hello all, I said I would get back with results of changes:
    I tried designing props using Javaprop which would theoretically provide about twice as much thrust and efficiency but they were too difficult to make in the time I left myself (last minute of course). So I then built a step up belt drive speed increaser but the result was very disappointing with only about 7% increase in rpm; I think the drill might have been reaching it's power limit, don't really know why.
    For this years race I went for two props in water, conventional by CCC standards, driven from long shafts. Ended up with 12" x 8" props from model 'planes but the drills were cutting out due to overload; they work again as soon as you release then pull the trigger.
    Thanks for all suggestions last year.
     
  5. alan craig
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    Location: s.e. england

    alan craig Senior Member

    Pic posted here, couldn't get into previous.
     

    Attached Files:

  6. portacruise
    Joined: Jun 2009
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    portacruise Senior Member

    Thanks for the post.

    Wonder if list member Jeremy participated this year and what the winning entry looked like.

    Porta
     

  7. Jeremy Harris
    Joined: Jun 2009
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    Jeremy Harris Senior Member

    Unfortunately I didn't have time to compete this year, we're part way through building a new home, and it's absorbing a fair bit of my free time. I may have another go next year, as I've incorporated a boat shed and workshop in to the new house..........
     
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