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A Hebridean principle vane gear for Shui Jen

  • 18 Oct 2023 15:13
    Quote
    Reply # 13268765 on 13264965
    Anonymous member

    Hi Asmat,

    I think I've found the text about the de-powering effect of inclining the vane axis...

    John S. Letcher self-steering for sailing craft pages 145-146.

    Thank you again for the input!

    Mauro


    P.S: a free PDF version of the book can found under:

    https://jesterchallenge.files.wordpress.com/2018/02/self-steering-for-sailing-craft-by-john-s-letcher-jr-small.pdf 
  • 10 Oct 2023 18:20
    Quote
    Reply # 13265326 on 13265187
    Anonymous member
    Anonymous wrote:The purpose of an inclined axis is to prevent oversteer. As the vane deflects, its power diminishes. Imagine the vane blade deflected 90°, until it is completely horizontal. Thanks to its inclined axis, it is now in an attitude giving lift, tending to return it towards its initial, vertical position. 

    Hi Asmat,

    thank you for giving me the second good reason to leave the design of the vane unchanged!

    Ciao

    Mauro
  • 10 Oct 2023 13:46
    Quote
    Reply # 13265187 on 13264965
    Anonymous member
    The purpose of an inclined axis is to prevent oversteer. As the vane deflects, it's power diminishes. Imagine the vane blade deflected 90°, until it is completely horizontal. Thanks to its inclined axis, it is now in an attitude giving lift, tending to return it towards its initial, vertical position. 
  • 10 Oct 2023 11:54
    Quote
    Reply # 13265157 on 13264965
    Anonymous member

    Thank you Scott!

    This make sense...

    I'll build the vane as described from David ;)


    Cheers 

    Mauro
  • 09 Oct 2023 21:18
    Quote
    Reply # 13264978 on 13264965
    Anonymous member

    Hello Mauro,

    I have not (yet) built my own vane gear, but I have done my best to understand David's design and the construction details.

    I think this reply from David  explains why he added some inclination to the vane axis.

    Without this inclination the vane position will become unstable as the boat rolls to windward. With a horizontal axis, the top of the vane will be further into the wind than the axis such that the vane could be driven in either direction by the wind. And, after having gone in one direction the vane would tend to flop all the way over.

    With some inclination added to the vane axis you can ensure that the top of the vane is always trailing downwind from the pivot point.

    I expect the vane that you drew would have still have issues with stability as the boat rolls on the waves.

    This is how I understand things. If anyone else thinks I got it wrong, please correct me!

    I hope this is helpful.

    Last modified: 09 Oct 2023 23:08 | Anonymous member
  • 09 Oct 2023 20:38
    Quote
    Message # 13264965
    Anonymous member

    Hi David, hi all!

    After two seasons on my Kingfisher 20+ named Shui Jen I'd like to sail a bit along the coast alone. My aim is to improve my skills particularly in terrestrial navigation.

    My big little yacht starting from F4 has a weather helm that is too much for my bungee to tiller system. For chart work in a moderate breeze I need a steering assistent. That's why, after reading the book of Bill Belcher, I started a new winter project: building a David Tyler's hebridean principle vane gear.

    I have question about the vane turret. Was the increased inclination of the turret from 10 to 15 degree, a way to align the centre of pressure with the course-setting axis of the vane? 

    If yes, could the same effect be obtained by sloping the only vane and not the turret?

    Keeping the turret upright would simplify the building....

    I made a primitive drawing without any scale or proportions just to clarify my idea...

    I would appreciate any comment....particularly from David of course :)

    Buon vento

    Mauro 

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