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Thread: Prop size vs blade number

  1. #1

    Prop size vs blade number

    Yup me again with my hand out.
    You know the drill VW 1600c and Snowmobile clutch drive.
    I have 64 X32 wooden two blade prop and a composite three blade 59" with 10* pitch blocks.
    Both spinning at 3100 rpm.
    Which one should give me the Most "Push"
    Don't care about " Hole shot".

  2. #2
    Super Moderator Corky's Avatar
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    Re: Prop size vs blade number

    Your engine has a set torque and HP for the given working curve...It is what it is no matter what you're loading on it to do the work...All things being equal it comes down to where each prop hit's it's working efficiency...Prop pitch,chord,material, all come into play here..You need to know the manufacturer's specs and the intended application to make an educated decision for which prop would fit the bill on your engine.... Here's an article on multi-blade props and how more or less blades affect performance..This is for airplanes but the principals are exactly the same...http://aerotrash.over-blog.com/2015/...ropellers.html

    Aluminum .120 14' X 76" hull
    Teledyne 4a084-4 engine
    Circle S 1.69:1 reduction
    67" Whirlwind "Razor X" prop



  3. #3

    Re: Prop size vs blade number

    WOW! That makes my head hurt. Way over my head.
    In your exert opinion which is light years ahead of mine.
    Which , off the top of your head would you think would push
    my cat best, speed is not important.
    I can turn both props to 3100rpm which is what Competition aircraft
    says there Ultra-Prop .is max. It happens to be at 3200 rpm on my motor for each prop.
    The wooden prop actually runs a smidge slower at 3000rpm. Both load the motor and That's
    as fast as it will turn.

    https://www.youtube.com/watch?v=okmC...ature=youtu.be

    I had the boat locked down not able to move But it felt like it wanted to with both.





  4. #4
    Super Moderator Corky's Avatar
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    Re: Prop size vs blade number

    ... Yeah, the technical equations are nice but if you read between all the technical formulas there are a few good points... In my opinion I'd give the ultra prop a chance first and see how it performs...I like having the ability to change the pitch if I ever make improvements that swing the power band up a touch and need to add some pitch{in a nutshell that article states the 2 blade might be more effecient in the long run so I'm actually going against the suggestions there}.....The nice thing is you can always try the other if you think there's something to be gained...Just be sure to build your cage using the bigger prop to make sure you have the clearance to play with them...
    Last edited by Corky; 02-04-2018 at 07:13 PM.

    Aluminum .120 14' X 76" hull
    Teledyne 4a084-4 engine
    Circle S 1.69:1 reduction
    67" Whirlwind "Razor X" prop



  5. #5

    Re: Prop size vs blade number

    Kinda the direction I was thinking too.
    Is 1 * a big enough change to tell a difference?

    I have 10* now and feels like I could a very small amount more.
    So is the $21 investment worth trying

  6. #6
    Administrator Papee's Avatar
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    Re: Prop size vs blade number

    Ultra props have a better low end push but they run out of push early. They will get you out of the water fast but cruise is better on a stick or air foil type prop at least in my comparison. The cheaper props like the ultra prop or arrow prop have a flat profile.

    Also pitch degrees and pitch number on a prop are two different things.
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