Pedal (assist) boat prop pitch

Discussion in 'Boat Design' started by jakeeeef, Nov 7, 2021.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    Everyone else on the wrong track bar you, you think ? I'm sure the matter of electric planing boats is exercising a lot of minds, because there is an awful amount of money to be made from it, if it can be successfully accomplished to a standard of utility comparable to current internal combustion powered boats. The stumbling block appears to be battery storage capacity versus weight. The angle of lightening the boat and other ways of reducing the resistance would not be being neglected, you can be certain of that.
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    Like most things design related - it depends.
    On pure numbers alone - it is 'suggestive'... but that is in an ideal setting...and with many assumptions.
    None of which are currently known.

    There in lies the crux of the issue.

    Design of "one element" is an easy engineering exercise. Not rocket science at all.
    However, as per my footer, design is a multidisciplinary process and as such it is greater than the sum of its individual parts.
    In simple terms, each item on its own, may be "ideal" but brought together not so, and requires a holistic review. Focusing on one element is missing the big picture of what naval architecture is and how to get the best fit - for the given SOR. One needs to 'design' the whole system that is surruoding or being supproetd by said "indidvaul" item..and only then can said individual 'item' be reviewed to ascertain whether it is helps to satisfy the SOR.

    Well, that is the cart before the horse.
    If you want your "system" to work and to establish its parameters, you need a NA to show you how your "system" fits into the holistic process we call - design.
    Focusing on one element - will not do that.

    Investors care little about patents. They care about - show me the numbers of how it will work and why.
     
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  3. jakeeeef
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    jakeeeef Senior Member

    I wouldn't invest in an idea that was novel, but unprotected by IP. I'd possibly take the idea to a manufacturer in a better position to build it more quickly and cheaply though. And if it was unprotected, I'd be perfectly entitled to do so.

    That's my understanding of the situation, but I'd be very grateful to hear other views.
     
  4. jakeeeef
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    jakeeeef Senior Member

    But does this depend on the size and complexity of the boat? This boat is so small, I wonder if prototyping and actually trying it with a range of motors, props etc. might initially turn out cheaper than having a NA run the numbers?

    I can completely get what you are saying even if the boat is a small dinghy, RIB etc upwards, (and certainly a CTV or similar) but this boat really is tiny.

    My thought was get the thing vaguely working with the skills I have, then that rough proof of concept warrants the investment of getting it tidied up by a professional.
     
  5. Ad Hoc
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    Ad Hoc Naval Architect

    That's what NDAs are for.!
     
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  6. Ad Hoc
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    Ad Hoc Naval Architect

    If that's what you feel is better, then there would be no point in

    Since by your own admission, you will have proved the concept....
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    What is the area of the boat's "footprint "?
     
  8. jakeeeef
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    jakeeeef Senior Member

    Ok,
    Before I start troubling any naval architects, I need to measure my losses, and actual motor output for the running time.

    Otherwise I won't know how much torque and power I have to work with. That's obviously key as it effects the weight, therefore range, planing etc.

    I've looked at rotary torque transducers. Is this the right way to find out? Or is there a cheaper way. It only needs to measure up to approx 10 hp max. And the ones I have found so far seem to be much more substantial than this.
     
  9. alan craig
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    alan craig Senior Member

    You can easily measure power IN to the motor with a wattmeter... then multiply that by the efficiency, which you might have to guess or maybe the manufacturer publishes a chart or figures... to get the power OUT to the prop. Then divide power by rpm to get torque. Google for units!
     
  10. Skyak
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    Skyak Senior Member

    I have investigated this
    -Use autocad 360 -it has a free tier until you get over $100k/year and it is a reasonable subscription after. Solidworks is fine but you will be out $5k before you have a clue what you are doing. Consider hiring CAD/engineering talent if you are not proficient already.
    -Start with a "Provisional patent" or equivalent. For a couple hundred dollars it sets the date and protects while you develop and test.
    -you almost certainly need to create a limited liability company -for taxes and liabilities.
     
  11. Skyak
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    Skyak Senior Member

    Will Frasier used to contribute here. A couple years ago he did a super job documenting (on Ytube) his design, test, and build of a solar boat for a competition. If you check out his later build and test you can see exactly how to do it, and the entire energy budget. If that seems too complex, you need to hire it out, because it just doesn't get any easier.
    There have been several battery electric surfboards built and documented on YT and Kickstarter. I would not choose any of them as "efficient as can be". They all use smaller, less efficient, lower toque props, often shrouded. This might be a wise marketing or safety feature.
    Torqeedo EOBs are a good efficiency reference. They can be beat, but not by a huge amount.
     
  12. jakeeeef
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    jakeeeef Senior Member

    I have read that there is a 'hobbyist' version of solid works. $100.
    It is, unsurprisingly, a less feature rich version, and I need to check out if it can do what I need. The promotional video for it certainly shows things modelled of a complexity beyond what I need.

    While hiring CAD talent is an option, getting my head round CAD has been something I've been meaning to do for a decade. Hiring in talent makes me worry if it doesn't work out, I won't have learnt as much in the process, and it will have cost me too.

    They only let you have solid works hobby edition for a year though.

    By which time you will of course invested months in learning it., So will perhaps continue with the $5000 option. I guess that's why they risk this model.

    But not sure how they stop people getting a succession of family members on different IP addresses getting it for several subsequent $100 years on their behalf?
     
  13. jakeeeef
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    jakeeeef Senior Member

    I think I need to try to find a company that hires out industrial instruments here in the UK.
    It's a funny size for a dynamometer. If it was a car or motorbike I was testing upto 1000 hp, there's a bunch of tuning shops in my home town alone that hire out their Dyno for £75- £100 per hour, but that's too big and for something with tyres. If it was an RC sized motor, dynamometers of this size are also easy to come by. These test bench devices for testing the 1-10 KW range, look much harder to come by!

    Just not much call for them I guess.

    There are bicycle turbo trainers that measure these parameters, but I'm concerned they are set up to attempt to give the cyclist their power at the cranks, but they never measure it directly there, so I suspect they might be set to provide an over reading to account for tyre/ roller friction or drivetrain losses and they don't provide info either way. Also most are rated at 2 kW maximum where they quote it. In short, I don't think I'll know exact numbers for sure unless I use something closer to a 'scientifically calibrated' device.
    I'm going to speak next week to a company I've worked with on the past who do marine load cells etc. They won't be able to help me directly, but hopefully they know enough about the testing business to put me onto whoever can.
     
  14. SolGato
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    SolGato Senior Member

    The best real world data available that closely translates to what you are trying to accomplish is Torqeedo’s specifications for their Cruise 4.0 electric motor.

    With their 1953-00 3-blade 11.8” diameter x 16.3” pitch prop, that motor will get a 200kg/440lbs vessel on plane at 24km/h or 15MPH.

    The Cruise 4.0 is a 48V 4kw input/2.24kw output motor with a lower planetary gear reduction that spins at 1300RPM.

    It takes a lot more electric propulsion power to get a boat on plane at those speeds than most people realize.
     

  15. jakeeeef
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    jakeeeef Senior Member

    There are 200kg vessels and 200kg vessels. However I'd still be interested to know if they are talking 200kg + payload, or 200kg total system weight.
     
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