A vane gear for Weaverbird

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  • 24 Mar 2017 16:06
    Reply # 4687767 on 4048415

    Mark,

     thanks for pointing out. It totally slipped off my mind,  I have seen picture of Oryx's vane before but couldn't get any disruptions or drownings for this type of vane.

    I'll post some pictures when hulls are turned.

     

  • 23 Mar 2017 13:25
    Reply # 4685140 on 4048415

    Vlad,

    Catamarans don't suffer weatherhelm so much and should be well balanced - so you can get away without a servo.  Have a look at Oryx, Pete uses simple horizontal axis vanes (I think I am correct) on his stretched KD860. 

    Look forward to seeing you cat complete,  I am quite a fan of Bernd's designs.  

  • 23 Mar 2017 08:30
    Reply # 4684694 on 4684193
    Karlis Kalnins wrote:Thanks for sharing, David. Am I correct in understanding that the Hebridean concept is that the vane/mount/course wheel rotate (horizontal-ish axis) with the servo blade? Unless I'm reading the dxf wrong, that seems to be the major difference compared to something like the Belcher (and your previous) vanes.

    That's correct. A full discussion of the reason for this can be found at 
    http://www.windvaneselfsteering.co.uk/
    wind-vane-design-features.htm

    The other design feature I see is that the servo seems to be forward-mounted or leading it's pintles (vertical axis). Is this just convenient, or does it confer some advantage?
     
    The vertical axis is set at 23% of the chord of the servo blade, to get enough hydrodynamic balance without risking overbalance. The upper part of the servo blade is deliberately placed forward of the vertical axis to get the mass balance correct. When the structural components are all aft of the axis, weight ought to be artificially added forward of the axis to achieve this. 
  • 22 Mar 2017 23:47
    Reply # 4684193 on 4048415
    Thanks for sharing, David. Am I correct in understanding that the Hebridean concept is that the vane/mount/course wheel rotate (horizontal-ish axis) with the servo blade? Unless I'm reading the dxf wrong, that seems to be the major difference compared to something like the Belcher (and your previous) vanes.


    The other design feature I see is that the servo seems to be forward-mounted or leading it's pintles (vertical axis). Is this just convenient, or does it confer some advantage?
     
    Last modified: 22 Mar 2017 23:51 | Anonymous member
  • 22 Mar 2017 17:38
    Reply # 4683400 on 4048415

    Thanks, David.

    It is a cruising cat. I am building ECO-7.5 designed by  Bernd Kohler stretched to 9 meters. Two hulls are built, getting them ready for the glassing. So it is a bit early stage, just trying to investigate possibilities of using the wind vane on the catamaran.

    Last modified: 23 Mar 2017 08:16 | Anonymous member (Administrator)
  • 22 Mar 2017 07:27
    Reply # 4681982 on 4681906
    Vlad Sokolsky wrote:

    Hi David.

    Very nice job. Do you think this design concept could work on a small (9 m) catamaran? 

    Yes, so long as the catamaran is of the slow, heavy cruising type and not a light racer that accelerates fast; it's rapid changes of apparent wind direction that defeat all vane gears when used on fast multihulls and monohulls. My gear is sized for a 7m boat, and would need scaling up, but otherwise there's no reason why it shouldn't be used on larger boats.
  • 22 Mar 2017 06:18
    Reply # 4681906 on 4048415

    Hi David.

    Very nice job. Do you think this design concept could work on a small (9 m) catamaran? 

  • 21 Mar 2017 13:34
    Reply # 4679978 on 4048415

    David,

    I am able to open the DXF, and now understand how it works.  Once you have it set up with the lines in place, it should be very clear to all. 

    It really is a very simple, yet sophisticated design, excellent work.

     

  • 21 Mar 2017 01:50
    Reply # 4679123 on 4059800
    Darren Bos wrote:

    Paul, I always thought the Cape Horn had some interesting design features.  I think it fits in David's category 4 (servo pendulum, horizontal power axis).  Do you have any thoughts as to what characteristics prevented the Cape Horn from working while you've had success with the Hebridean?  Could it have been as Slieve describes and the servo blade had forward rake?

    Not really, the thing would always only steer in one direction and never the other... It was a brand new unit and for all I know, it may have had a manufacturing fault. However trying to get assistance from a French Canadian in Canada from New Zealand was an exercise in frustration. Had I been hearing I might have had better results via the phone but email was hopeless so in the end I just moved on.
  • 20 Mar 2017 17:26
    Reply # 4678286 on 4048415

    Arne,

    I've dreamed up some of these non-slip sheave designs for continuous lines, but they're not needed in this case: When using a primary cord linkage, there can only be less than 360 degrees of adjustment (obviously), so the course adjusting lines can go through holes at the bottom of the groove  with stopper knots tied in a recess inside the sheave.

    Mark,

    The drawing is now here , but be aware that it is by no means a "Recipe" that can be used to build one, without knowing anything about vane gears. It's purpose was simply to develop the geometry of the mechanism. 

    A cloth vane on a frame may develop a little bit of camber. But it doesn't matter if it doesn't. 

    Last modified: 20 Mar 2017 18:41 | David
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