Surface Propulsion, long-tail-emprovements.

Discussion in 'Surface Drives' started by tom kane, Feb 9, 2016.

  1. tom kane
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    tom kane Senior Member

    An interesting web site about Indigenous Boats.

    http://www.indigenousboats.blogspot.co.nz/2012/10/burmese-long-tails.html

    The original French circa, 1900 design offered to the public as the first outboard motor has spawned a lot of variations and improvements through out the world.
    The idea to lift the drive propeller shaft has made boating easier for many socialites and must have saved much damage over the years and made fishing and travel easier, and yet so called developed countries have not
    adopted the principle.
    Spelling of web site is correct but is not correctly spelled in saved post.

    www.indigenousboats.blogspot.co.nz/2012/10/burmese_long_tails
     
    Last edited: Feb 9, 2016
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    How can you trim the bow up, if needed, with such a drive ?
     
  3. tom kane
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    tom kane Senior Member

    They seem to be doing that successfully.Do you understand the mechanics of system?
    Different boats would respond with different plane angles.
    How do other S/P drives cope?
     

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  4. Mr Efficiency
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    Mr Efficiency Senior Member

    They don't cope unless the boat is suitable for them, you have a propulsive force being appled higher up than other drives, that itself pushes the bow down. You can't raise the bow by changing the drive angle, because the prop just comes out of the water further, losing thrust and racing the engine. The hull needs to have an inherent tendency to run bow-high, and porpoisy, so that trim can be adjusted by tabs/interceptors.
     
  5. tom kane
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    tom kane Senior Member

    Attached Files:

    Last edited: Feb 10, 2016
  6. tom kane
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    tom kane Senior Member

    Does anyone know how these Burmese long tails are set up or can supply drawings of the mechanics of them.? Must be somebody mechanically minded with an interest in how they work. With no specific photos or a good explanation one can only guess.

    My guess is that they have about 10 degrees movement from side to side and up and down with the single U/V joint out side of the transom exposed to the elements
    and a shaft from the motor run to a bearing at the transom also exposed to water.

    The Burmese do a lot of work and play with them with water spraying everywhere.
     
  7. Jim Caldwell
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    Jim Caldwell Senior Member

    No U joint, motor and all pivot.
     
  8. tom kane
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    tom kane Senior Member

    Surface Propulsion,long-tail-emprovements

    The drive system I am interested in is not the usual direct drive, but the other easier to handle pivoting at the transom drive like the one in this image.
    Gives a flatter shaft angle and other advantages.
    Thank`s for reply.
     

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  9. Jim Caldwell
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    Jim Caldwell Senior Member

    Does not look like a long tail, prop churning water 3 feet from stern, no motor visible above transom, appears to have a strut angle back off transom to hold prop shaft.
     
  10. SamSam
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    SamSam Senior Member

    Here's the kind Jim Caldwell is referring to, where the whole thing pivots. I guess the yellow plastic jug keeps the big lumps of water off the generator/alternator. It looks like there is a big plate/trim tab below the water, but i can't figure out what all the spaghetti like tubes are for.

    [​IMG]

    This is what you're referring to...

    [​IMG]


    [​IMG]


    I think you have the general idea of how they work down good enough to build one. I don't believe the u joints are underwater except maybe occasionally. I imagine they are regular car type universal joints, which are exposed to all sorts of water conditions under the car, and function pretty much flawlessly with maybe a little grease now and then. There aren't any splines as otherwise there would have to be something to retain the shaft and propeller from pulling off the boat when slowing down etc.

    The knuckle at the top of the transom looks to also be a car u joint with a vertical shaft welded to the center for the lever control to shift the prop side to side, with the up and down part utilizing the u joint yoke as it normally would. You can see the other unused set of yokes facing fore and aft.

    In the middle photo, on the second boat from the bottom you can clearly see how the water pickup for the engine cooling works, where it loops around and scoops up water. I'm not sure about the shorter pipe just below it, I thought maybe it was just for support of the upper tube, but the way it is it seems like it would inject air in front of the scoop tube. Maybe that helps keeping stuff from plugging up the water scoop tube.

    They all have a rope on the handle to hold the lever down and the propeller up out of the water when parking. I have no idea what the two little tubes just above the steering knuckle are for. The curved bar connecting them together suggests they hold something but I don't know what.

    The first longtail has the disadvantage of putting all the weight up high on a skinny boat, the second kind puts the weight low inside the boat, but you have to sit behind the engine while running, getting all the noise, all the fumes and all the heat which must be a nuisance in a tropical climate.

    In this video '' caught in weeds '' http://jtdytravels.com/category/burma-myanmar/ (the second one) when the guy raises the prop the big flywheel stops but the center shaft keeps turning. That must be some kind of clutch/transmission thing. It looks like on the other boats the driveshaft goes under the engine, so they must get the power off the front of the engine somehow.
     
  11. tom kane
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    tom kane Senior Member

    Thank`s SamSam showing the two different (models) of long tail boats, there must be a history of where and how the Burmese models evolved different to the direct drive version.
    I have not been able to find working diagrams or anything properly explaining the working of the Burmese version which gives a flatter shaft angle and easier handling and other things .
    Some modifications to the Burmese model could give it more than 20 degrees of movement up down and left and right and also put the U/V joints inside the transom and a shorter prop shaft behind the boat.
    The Burmese model is a very simple and effective DIY version of some of the very expensive and sophisticated S/P drives.
    I suppose the may be other models different again.
     

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    Last edited: Mar 12, 2016
  12. SamSam
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    SamSam Senior Member

    Cripes!

    [​IMG]
     
  13. Barry
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    Barry Senior Member

  14. Mr Efficiency
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    Mr Efficiency Senior Member

    These contrivances are basically for use in flat water environments.
     
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  15. tom kane
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    tom kane Senior Member

    Surface Propulsion,long-tail-emprovements

    Perhaps you can find me some information about how long and from where they found this long tail design and adapted it to their environment.
    There must be other designs in other parts of Asia.
    Wikipedia has got it all wrong in their information.
    I still would like a diagram of the Burmese version and what they call it.
     
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