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    Re: Voyaging the traditional way
    From: George Huxtable
    Date: 2004 Nov 4, 00:23 +0000

    Bill asked
    
    >Regarding taffrail logs:
    >
    >While I have a used brass T.W, Cherub on my fireplace mantel, I have not
    >used it nor do I have the counter (perhaps the wrong term?).  I have read
    >that they tend to lose accuracy in following seas. (My guess is they run too
    >slowly.)
    >
    >Could Robert, David, et al comment on their experiences of the accuracy in
    >different types of seas at different points of sail?
    
    ==================
    
    Response from George-
    
    I've used a Walker taffrail log for many years. I don't make ocean
    passages, but with that log astern I have been through some roughish water
    (by my standards) in my time, in the "chops of the channel" and off the top
    left-hand corner of France. But nothing like as ocean storm, glad to say.
    
    It normally stays trailing from the taffrail unless I feel the need to
    trail a mackerel line, as the two are incompatible. I've used it when my
    nav was by DR and radio DF bearings, and also later, in conjunction with
    GPS.
    
    It's difficult, however, to make a good estimate of the accuracy of the log
    in such (very) tidal waters as those I inhabit. However, it's only under
    idle conditions that I have had cause to suspect if of inaccuracy, when it
    tends to droop rather than trail. If I were in continuously heavy breakers
    then I would start to distrust it, but would then have other troubles on my
    mind.
    
    The rotator never seems to jump out of the water, under the worst
    conditions I have been out in. Parhaps a helpful factor is that my little
    boat (on rather Folkboat lines) is very close to the water, with only a
    couple of feet of freeboard, where the log is attached at the
    stern-decking.
    
    I think the most testing conditions for a trailing log are in a power
    vessel that's pitching into a head sea. I made a passage in a small steam
    coaster, rather lightly laden, back around 1950, and approaching Cape
    Cornwall the pitching was severe enough to give the engine-room gang a lot
    of work in winding the throttle-valve to control the racing when the screw
    came right out. Standing at the taffrail was like being in a lift as it
    went up and down, and the cord of the Walker log was making some very
    strange angles with the horizontal. But it was a very long cord, and I have
    little doubt that the rotator itself was trailing at a comfortable angle.
    Somebody came aft from the bridge to read it, now and again.
    
    As long as a vessel is being regularly passed by waves from astern, then I
    suggest that the effect of those waves on the log averages out. That is,
    being slowed when immersed in water moving the same way as the boat (and
    the wave) when the rotator is at the top of the wave, then speeding up when
    in the water moving the opposite way on the bottom of the wave. Swings and
    roundabouts. But things may be very different for those fast multihulls
    that are able to "surf" along the face of a wave for long periods.
    
    This reply has been rather  anecdotal, I'm afraid, and I think Bill is
    seeking something more numerical.
    
    Finally, a word of advice to users of Walker logs. Look over the stern
    before engaging reverse gear. Failure to do so cost me a rotator.
    
    George.
    
    
    ================================================================
    contact George Huxtable by email at george---.u-net.com, by phone at
    01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
    Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    ================================================================
    
    
    

       
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