Most Efficient Boat Propulsion

Discussion in 'Sterndrives' started by tom kane, Dec 4, 2014.

  1. tom kane
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    tom kane Senior Member

    Which boat propulsion system is the most efficient for all purpose boating?
    The image contribution shows a boat propulsion that has a shaft drive that can be run at any shaft angle and in surface piercing mode or subsurface mode.

    When the boat is launched the drive is at the lowest point for immediate thrust and as speed is gained the prop is raised to S/P mode for fast crusing with only the bottom of the prop doing the propelling and the only water drag is the hull and half of the prop. The prop is protected by sensors that detect any object in the path of the prop and lift the shaft if necessary and control the motor RPM.
     

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  2. tom kane
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    tom kane Senior Member

    Image shows a fixed tractor propulsion which gave good performance but would it not be great if it was steerable and jackable..not akward tilting like others.
     

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  3. myark
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    myark Senior Member

    Hi Tom
    When I have time and the $ I will be making a new design catamaran that the centre part slopes down towards the bottom of the twin hulls then the last 1m kicks up 45mm from level so it rides similar to a whales tail or hydrofoil while making buoyancy catamarans do not have in back end but still allowing to slice through waves in front of boat so no pounding.
    Because the cat has the extra buoyancy in back end an inboard sites in this region and still allows boat to sit in water level when not under propulsion as cats normally stick upward with the motors weights in the back.
    This design is suited for the pivotal drive system allowing all the benefits of your design that can perform like a jet unit but does not lose power running through an expensive jet unit as your design can be a direct shat drive, also no weed to clog the grating in jet units in fact the pivotal drive eats weed and turns it into thrust.
    For the future Myark folding trailer barge designs where the towing vehicle is driven on deck and directs its power source into a pivotal drive is the affordable solution to reliability and performance.
    As you mentioned the pivotal drive is so basic for example it can be placed on a direct drive from the engine, and when do not want power the shaft propulsion is simply lifted out of water if wanting to keep engine running.
     
  4. tom kane
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    tom kane Senior Member

    At least someone seems to understand simple mechanical devices. There is a World of inovation waiting for those with a little imagination. I sometimes wish I stayed with boats instead of loving Ground Effect Vehicles but boats can not do what i want to do. You will just have to get stuck in or you will run out of time like me.
     
  5. gonzo
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    gonzo Senior Member

    Tom: The conflict I see is that propellers designed to work ventilated don't do well completely submerged. This is the reason that many surface drives use the exhaust to ventilate the propellers and get the boat going. However, are you targeting a particular performance area where you think there could be a compromise design?
     
  6. tom kane
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    tom kane Senior Member

    Hi gonzo, I am inclined to think that purpose ventilating a propellor has no useful purpose as ventilating will automaticaly take place when the boat picks up speed and planes... ..this is what happens with most fast boats but many boats with fixed surface drive may have trouble getting moving because the prop ventililates and has no initial thrust. If you can adjust the shaft angle anytime you have more control over the prop placement.

    You are not going fast most of the time under many different sea conditions and you need control over where the prop is running especialy with following seas in general boating. If a surface drive does not operate at say 20 degree shaft angle it is not properly set up. You may get sick of a surface drive set up anyway and with Smart Drive you can easily have a choice by just changing a prop! Any propeller with heavy pitch will work in S/P mode as illustrated by 1950`s race boats where S/P mode was reconized.

    A selection of gears does wonders for autos both manual and automatic. There are 9 speed autos now and variable drives.
     
  7. gonzo
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    gonzo Senior Member

    All surface propellers operate in a ventilated condition. That is what keeps them from cavitating. Have you been able to accelerate a boat with one of those propellers without some kind of ventilation? All racers have some kind of system for it.
     
  8. myark
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    myark Senior Member

    Yes time fly’s as at first I thought plenty of time while having a good life of freedom, adventure and innovation that past so quick, especially now with two sons aged 5 and 10 years old.
    I am developing smaller ideas that one will be on www.kickstarter.com in the next week or so which is a tool that is suited for boating.
    I have about 20 smaller ideas for this Kickstarter web site that will run one after the other if the first one works, so I expect to make $ to carry on Myark water craft designs on the side in my workshop in China such as your pivotal drive is a good project.
     
  9. jehardiman
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    jehardiman Senior Member

    Tom, the problem is always going to be how much a priori knowledge you need. There are lots of system that work if you have 110% knowledge of what will happen. If you have a system that reacts to sensed conditions, it will always be xx.0% behind what it needs to be. In this sense, Ground Effect Vehicles are dirt simple with respect to ocean vehicles...i.e. you never know the conditions until they are passed.
     
  10. tom kane
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    tom kane Senior Member

    All surface drive props start submerged if you lift the drive your S/P prop will will be in a better position to work ventilated before planing. I have not seen many race boats with exhaust ventilated props. I am not keen myself on full S/P boating but being able to lift your prop into lower water pressure can reduce drag. If you reach 25 knots that is when S/P props get atvantages. Can you define a S/P prop?
     
  11. PAR
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    PAR Yacht Designer/Builder

    Please define "most efficient" . . .
     
  12. myark
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    myark Senior Member

    Tom said
    "Which boat propulsion system is the most efficient for all purpose boating?"

    Efficient from common sense point of view means, cost to purchase efficiency, performance from motor to drive efficiency, reliability efficiency, maintenance efficiency, fuel efficiency, or efficiency in weed invested waters, shallow water efficiency, DIY service efficiency and so on for all purpose boating
     
  13. FMS
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    FMS Senior Member

    On fuel efficiency and all purpose boating, I've seen many friends change their use when gas prices went up by $.50 and $1.00. When gas was less all purpose boating was cruising most of the day at 25-35mph. When it cost hundreds of dollars more to fill the tanks, that changed to more hours at no wake speed. That changes what drive would be most efficient.

    On maintenance efficiency, the Mercruiser outdrives aren't great in my opinion. However all the mechanics in this country have parts and know how to fix them because they are so common. That makes service easy and reliable regardless of the design itself.
     
  14. gonzo
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    gonzo Senior Member

    A surface piercing propeller is one that has blades operating out of the water during the upper part of their revolution.
     

  15. tom kane
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    tom kane Senior Member

    I think I understand what you are saying..all the boat experts I have met tell me you can not do this or that and it will not be efficient especially on these forums yet it is being done all the time somewhere.

    Try talking to ground effect vehicle, air boat, experts you get the same response about something that they are not familiar with.You better have more thoughts about ground effect vehicles if you think they are dirt simple I am told they are very dangerous and only highly trained experts know how to build, fly and handle them. Perhaps they do not stop to study your questions before giving opinions.
     
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