Composite Sailboat Propellers?

Discussion in 'Sailboats' started by Pteryx, Mar 4, 2009.

  1. Pteryx
    Joined: Mar 2009
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    Location: New Jersey

    Pteryx New Member

    Hey all,

    I'm an engineering student working on a solar-electric boat for my senior design project. We're currently having trouble finding a propeller for our endurance drive-system and would like to look into testing some composite sailboat propellers, but we have been having trouble finding suppliers, especially for lightweight props (composite or aluminum). Does anyone have any recommendations for sailboat prop suppliers? Any help would be greatly appreciated.

    Thanks!
     
  2. tspeer
    Joined: Feb 2002
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    Location: Port Gamble, Washington, USA

    tspeer Senior Member

    Take a look at model airplane propellers. Or even ones for small UAVs. They make some big props these days for large scale models. You can even find variable pitch props.

    If you want more solidity than just a narrow two-bladed or three-bladed prop, you could stack more than one on the same shaft, or even make them counter-rotating. But I suspect it would be better to simply go with a larger diameter.
     
  3. Guest625101138

    Guest625101138 Previous Member

    Can you give an indication of the speed and intended power.

    As Tom said there are some good airplane props. They tend to be underpitched for their blade area to suit boats.

    There is one decent CF boat prop for lower power applications. It has plenty of strength and good proportions for a boat prop. Could put a couple of kilowatts through it. Go down about half way on this page:
    http://www.bolly.com.au/models/glasstwo.html
    It is the 15 X 25 prop.

    This place has some solid RC plane props that are very low price for what you get:
    http://www.hobbycity.com/hobbycity/...7&Product_Name=Master_Airscrew_propeller_13x8
    http://www.hobbycity.com/hobbycity/...Product_Name=Master_Airscrew_propeller_12.5x5
    http://www.hobbycity.com/hobbycity/...0&Product_Name=Master_Airscrew_propeller_10x8
    http://www.hobbycity.com/hobbycity/...3&Product_Name=Master_Airscrew_propeller_12x8
    http://www.hobbycity.com/hobbycity/...&Product_Name=Master_Airscrew_propeller_16x10
    They might have enough strength if the boat is easily driven

    If you provide some idea of what you are trying to do then it will be possible to give you an idea of what will work best.

    You can get aluminium props machined to suit for about CAD600 if your budget goes to this.

    Also quite easy to fabricate a decent prop if you have normal shop tools such as welder and grinder.

    Rick W
     
  4. kenJ
    Joined: Jul 2005
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    Location: Williamsburg, VA

    kenJ Senior Member

    composite

    Might want to look at the Kiwi Prop. Built in NZ, metal hub with replaceable composite blades.
     
  5. Durando
    Joined: Mar 2009
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    Location: New Jersey

    Durando New Member

    Hello everyone, I'm also a member of this solar-electric boat team. To give you a better idea of what our intentions for this system are, we are using a Perm PMG 132 motor @ 24 volts. This provides for a power of approximately 2.2 KW. The propeller will be rotating at approximately 660 rpm.
    The system will be running on a predetermined course for 2 hours, with the objective being to travel as far as possible within the designated time period. I hope this gives you a better idea of what we are trying to accomplish.

    Thanks again!
     
  6. Guest625101138

    Guest625101138 Previous Member

    You have not provided the design speed.

    If you have not accurately established the design speed then give some idea of the boat such as length and displacement. With 2.2kW on a very light planing hull you could expect maybe 20kts.

    The attached analysis shows what you would get from the Bolly boat prop. It will certainly handle these loads. Note that you have to spin it at 1000rpm not 660rpm.

    A thrust of 200N would be enough to get a well designed boat weighing around 200kg on the plane and up to 20kts.

    The second set of data at 660rpm shows you need a pitch around 1m. You will only get this with a purpose built prop. If you have basic fabrication facilities it would take about 6 hours for a tradesman to make a prop.

    Rick W
     

    Attached Files:

  7. Durando
    Joined: Mar 2009
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    Location: New Jersey

    Durando New Member

    The boat will be acting as a displacement hull when in this configuration, therefore the goal speed of the system is actually 10 mph (8.7 kts or 4.47 m/s). The boat is 18 ft (6.1344 m) in length, and has a displacement of roughly 400 lbs (181 kg) when completely loaded. My mistake for not providing the goal speed initially. This speed should provide for a much lower value of pitch.
    Thank you again for your help.
     

  8. Guest625101138

    Guest625101138 Previous Member

    The optimum 5.5m displacement hull for 180kg will require 104N at 4.5m/s.

    I have no idea how close to the optimum your hull is but the Bolly prop is a good fit for this application. The attached shows what you could expect. It will need to spin at 520rpm.

    I have also attached the details of the best planing hull I can come up with in a few minutes to show what you would require to achieve close to 20kts with 2.2kW. I did this to see what was possible. You would need to reduce weight a little and make it streamline above the water. This planing hull is obviously very different to the 5.5m displacement hull optimised for 4.5m/s.

    If you wanted better analysis you would need to give details of your proposed hull.

    Rick W.
     

    Attached Files:

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