online prop design tool, check it out

Discussion in 'Boat Design' started by kerosene, Apr 8, 2021 at 7:30 AM.

  1. kerosene
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    kerosene Senior Member

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  2. Will Gilmore
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    Will Gilmore Senior Member

    Nice.
    I would be interested in that, as well. There is a company that makes and markets preformance props for trolling motors. I can't remember their name, though.

    -Will (Dragonfly)
     
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  3. kerosene
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    kerosene Senior Member

    I have seen one guy who does them in short series, casts by hand. and another one that is bit more professional.

    It would be neat to 3d print a prop. My think has been to model recesses to the prop - in the recess one could laminate glass reinforcements to give a little extra strength to the printed structure.
     
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  4. Dejay
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    Dejay Senior Newbie

    There is also prelimina prop but without fancy 3D generator.

    Unfortunately I still have no clue how to select an efficient propeller!
     
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  5. mc_rash
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    mc_rash Junior Member

    That depends on many factors, kind of boat, dimensions, speed, power, ..
    If you need help give some information and we will help.

    Edit: @Dejay I replied on your post and thought you were @kerosene
     
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  6. Heimfried
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    Heimfried Senior Member

    I used the mentioned website very few times to try to "create" a boat propeller. The results were not usable to me. The Wageningen ship researchers on ship propellers were (and to my knowledge are) word leading since about 1930/40. But their focus were on propellers for large ships and their results are not easy to scale to boat propellers.

    I'm interested in the idea of 3D printing props which has proven to lead to working props. My idea has been to print a developing series of props and the best one could be manufactured in metal perhaps. For this reason I wrote a software tool which generates a propeller from data I put in. I choosed these defining data according to the definitions on props of the International Towing Tank Conference ITTC. The output data consists a ".stl" file which to my knowledge will be a common input file for 3D printers. But I don't have a 3D printer.

    Unbenannt.jpg Fillet.jpg Rake.jpg Skew.jpg
     
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  7. Heimfried
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    Heimfried Senior Member

  8. mc_rash
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    mc_rash Junior Member

    As far as I know the Wageningen series is based on the Ae/Ao ratio which is a dimensionles fraction, so you don't really need to scale something (please correct me if I'm wrong). In my opinion it's not that easy to engineer new propellers that are better than these from the Wageningen series, doesn't matter how small/tall prop & boat/ship are.
     
  9. portacruise
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    portacruise Senior Member

    Kipawa is one of these, and most OEMs offer "high performance" propeller weedless versions for bass boat applications, but all the ones I have tested with a Troll Motor are less efficient than a properly selected model airplane prop. APC makes one particular Plug & Play generic prop that appears to fit most trolling motors for improving efficiency, but I have gotten the best results by fine tuning to the best specific size and pitch as confirmed by on the water- test measurements. Both APC and MAS have extremely low prices on their props compared to the alternatives, and they are fairly durable and cheaply replaced if necessary. I have found that the best exact prop size has to be tweaked according to the boat characteristics, motor RPM and torque as well as gear ratios when a direct drive is not used. The work done by Will Frazier and Rick Willoughby seems to confirm a generic 2 blade shape similar to a model prop is the most efficient compared to the shape of existing Troll Motor props.



    Hope this helps.
     
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  10. Heimfried
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    Heimfried Senior Member

    I don't think so. I'm no expert on propellers at all. If you look at the methods and the effort which is used to "translate" results of model ships in towing tanks to scale, then you will find that Froude number and Reynolds number, both very important to this point, have a very different behaviour if scaled. So this transforming is about approximations and very much experience. The Wageningen guys did free water measurements additional to the towing tank ones to examine (and I think to improve) their data. did read Dave Gerr's Propeller handbook which contains a series of Wageningen diagrams (BP-delta) to provide a pick of results. But trying to find the appropriate point for my very small numbers (power, diameter, ...) showed me that this data are not very helpful in my case.

    So, while scaleability is given, a starting data point far away of the center area makes the results less reliable.
     
  11. Heimfried
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    Heimfried Senior Member

    My remark in #6 that the Wageningen tool didn't help me, was not meant to discourage anybody to try it. In the contrary, if someone presents a successful result I would probably try the tool again.
     
  12. DogCavalry
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    DogCavalry I aim to misbehave.

    Model airplane prop! Absolutely brilliant. Fluid dynamics is fluid dynamics, as I occasionally say. That little guy isn't going to manage much disk load, because the blade roots are week, but then it doesn't have to.
     
    Last edited: Apr 8, 2021 at 5:09 PM
  13. portacruise
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    portacruise Senior Member

    Strange that (efficient?) torquedo and others still use a conventional looking prop, I don't know what up with that! If it's the weed Factor, that can be helped by using SS folding props like Rick W uses in his boats designed for HPB racing. Some sizes of model airplane props are available in carbon fiber, which is much stronger.

    Here's one commercial version that uses a model prop, though...


    EP Carry - Shop Now https://www.electricpaddle.com/shop.html
     
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  14. kerosene
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    kerosene Senior Member

    I think it comes down to what you are pushing. 22' yet 300lb displacement narrow beam human powered craft or "whatever the customer chooses to strap it to", including 2000lb displacing planing boat.
    Torqueedo has to work for "everybody", not quite but almost.

    trolling props are optimized for really slow speeds and potentially high drag. this makes the stock props leave a lot on the table when strapped to a kayak or similar low drag craft.

    Rick's aircraft props are optimized for lie rpm. When playing with the tool on this thread I actually got better efficiency when I reduced diameter. Surprised me but it might be the 1400 rpm that influenced it.

    (haswing osapian 55 was source for my specs)
     

  15. kerosene
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    kerosene Senior Member

    oh BTW the tool doesn't go below 0.3 area ratio. that means that the skinniest isn't really that skinny.
     
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