SibLim update

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  • 30 Apr 2018 21:39
    Reply # 6126910 on 6126908
    Annie Hill wrote:
    Paul Thompson wrote: You misunderstood, I did not mean to suggest that you should do it. Only to show that you can have a fully balanced rudder that is supported at both ends.

    Ah, I thought it was a suggestion.  I knew of your style of rudder, in fact.  They are usually fitted to motor boats in England.
  • 30 Apr 2018 21:36
    Reply # 6126908 on 6125432
    Paul Thompson wrote:
    Annie Hill wrote:

    To do as you suggest, Paul, would require some heavy metalwork, to ensure that the rudder is sufficiently strong.  I'm trying to avoid any more metal below the water so that I don't have to worry about electrolysis.  Moreover, I want to attach the rudders using James Wharram's method, with rope hinges.  Cheap, low tech, and incredibly easy to check or replace.  And doesn't require bushing.

    I've just posted on my blog, for those who are interested.

    You misunderstood, I did not mean to suggest that you should do it. Only to show that you can have a fully balanced rudder that is supported at both ends.

  • 30 Apr 2018 00:39
    Reply # 6125432 on 6124459
    Annie Hill wrote:

    To do as you suggest, Paul, would require some heavy metalwork, to ensure that the rudder is sufficiently strong.  I'm trying to avoid any more metal below the water so that I don't have to worry about electrolysis.  Moreover, I want to attach the rudders using James Wharram's method, with rope hinges.  Cheap, low tech, and incredibly easy to check or replace.  And doesn't require bushing.

    I've just posted on my blog, for those who are interested.

    You misunderstood, I did not mean to suggest that you should do it. Only to show that you can have a fully balanced rudder that is supported at both ends.
  • 29 Apr 2018 11:53
    Reply # 6124721 on 4315719

    Arne, if you look very closely at the cross section through the middle of the rudder, I drew a trim tab, which is what Annie wants for her self steering. It’s good to hear that you found no friction in the renewed Wharram figure 8 Dyneema cord hinge, as trim tabs are very sensitive to stiff rudders, to the point of not working at all well. When that’s the case, the fallback position is to reverse the linkage and convert the trim tab into an auxiliary rudder (which just happens to be mounted on the main rudder, which is fixed when the vane is in operation). 

  • 29 Apr 2018 09:38
    Reply # 6124648 on 4315719
    Anonymous member (Administrator)

    Annie, I bet you will be all right with the rudders David has designed for Siblim. I surely can see Paul’s point in making a balanced rudder for La Chica, but Siblim is so much lighter, and with fairly long tillers, so I think you will handle it easily (..btw, in Magazine 74, p.26, Karlis Kalnins describes a free-standing, balanced rudder with a little ‘deflector skeg’ to avoid catching ropes...).

    Last summer I helped a friend with replacing the hinge roping on his Tiki 21. The original was probably well over twenty years old, and were still not really falling apart. We used 3mm Dyneema line. The new hinges turned out to be as good as any; nice and tight and with no steering friction.

    If you ever find the tiller forces of Siblim to be on the high side, the straight trailing edge of the rudders would make it easy to fit a trimtab to one of them, and thus let you trim out any tiller forces. Even here, the use of rope hinges would simplify the job a lot.

    Good luck!

    Arne

     


  • 29 Apr 2018 02:35
    Reply # 6124459 on 4315719

    To do as you suggest, Paul, would require some heavy metalwork, to ensure that the rudder is sufficiently strong.  I'm trying to avoid any more metal below the water so that I don't have to worry about electrolysis.  Moreover, I want to attach the rudders using James Wharram's method, with rope hinges.  Cheap, low tech, and incredibly easy to check or replace.  And doesn't require bushing.

    I've just posted on my blog, for those who are interested.

    Last modified: 29 Apr 2018 02:39 | Annie
  • 23 Apr 2018 00:41
    Reply # 6114863 on 6100634
    Annie Hill wrote:
    Arne Kverneland wrote:

    There seems to be a problem with the new WA files section. I have yet to see any text following any diagram or photo. I think I'll stick to my member's photo album until WA fixes that....

    Btw,the rudders looks good, except that the full-dept skegs prevent the use of balanced rudders.


    I'll trade a balanced rudder against getting a rope caught between a partial skeg and the rudder!  Each to his own.

    LC had a fully balanced rudder and it was supported at both ends, so it is possible to do. In due course, Le Canard Bleu will be getting the same treatment.
    Last modified: 23 Apr 2018 00:43 | Anonymous member
  • 22 Apr 2018 07:08
    Reply # 6114113 on 4315719

    "I may be making progress, but I still have to fit out the saloon, the galley and the cockpit, lay the decks (including the teak- sorry Mr Tyler), put on the rubbing strakes, make the rudders and bilgeboards, make tillers, build a mast, make a sail, wire the boat, make cushions, paint the hull and around the cockpit and no doubt dozens of smaller jobs that presently escape my mind."

    Almost inaudible sigh. You will be reducing the thickness of plywood by the same amount as the thickness of the teak, won't you? Please?

  • 22 Apr 2018 02:35
    Reply # 6113987 on 4315719

    Blog updated, for those who wish to look.  Again, there's a bit of progress to see.

  • 16 Apr 2018 07:58
    Reply # 6100705 on 6100633
    Annie Hill wrote:
    David Tyler wrote:

    But, but, but...

    I made the drawing back in January last year. It lacks dimensions, that's all.


    I dare say you did, chuck.  But I can't find that drawing anywhere in my files!  Dimensions wouldn't go amiss ;-) if you could manage them. 
    These might save a bit of time with the rudder leading edge:

    http://www.windknife.com/full-foil 

    Cheap enough for what they are but I have not used them myself.

    Even the "nose only" section may not be big enough enough though.

    Not sure I am terribly impressed with their asym section, and its hard to see that nose scaling to an 800 mm chord.

    Then again David's asym foils would be dead easy to construct and those box sections look pretty strong to me.



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