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  1. #1
    Join Date
    Sep 2004
    Location
    South West Wales
    Posts
    681

    Default Navman Speed Log being over optimistic

    We have a Navman Log on Galadriel with a through hull paddle wheel. Last year it appeared to be fine - this year with the paddle wheel all cleaned and polished it is reading probably about twice the likely speed we are doing (let's face it, a 36 year old 25 foot fin keel boat with 9 HP on tap is unlikely to be hitting 8 knots when the tap isn't even full on).

    Before I invest in a replacement, has anyone any ideas?
    Mike

  2. #2
    Join Date
    Jul 2008
    Location
    ,home Portchester
    Posts
    2,434

    Default

    The only time we've hit 9 knots was reading our Navman GPS en route for Yarmouth with a F3-4 on the beam, cruising chute and about 2kts of tide beneath us, but we didn't need to adjust a thing the whole journey from Calshot Spit - Brilliant!

    Are you able to compare the reading with your GPS? we don't have a log and use GPS for our speed checks.(We are also a W.Tiger - T182 )

    As you are getting a reading I guess the little magnetic blob on the paddlewheel is still there,I don't know if it is a metal or metallic paste but it can be knocked off. Usually the problem is the reverse, where weed and marine life make their home in there,so under-reading or nothing registering at all.

    ianat182

  3. #3
    Join Date
    Sep 2004
    Location
    South West Wales
    Posts
    681

    Default

    Hi Ian,

    Yes we have a Garmin GPS and a Standard Horizon Chartplotter so have good speed over ground data. The paddlewheel was fouled but cleaned before our first trip this season.

    Its not really a problem as from last season we have a pretty good idea of speed through the water and with some tidal calculations can work it out.
    Mike

  4. #4
    Join Date
    Jul 2010
    Location
    Live: Surrey, Boat: Hamble
    Posts
    116

    Default

    Assuming you have the Navman Speed 3100 you need to run its speed calibration which can be found on page 8 of the manual http://www.plastimo.com/pdf/SPEED3100%28English%29.pdf

    The other Navman models also have calibration settings that you can use to adjust the speed reading and their manuals are available for download from http://www.plastimo.com/uk/services/notices.php if you don't still have your paper manual.

  5. #5
    Join Date
    Sep 2004
    Location
    South West Wales
    Posts
    681

    Default SJF comes up trumps!

    SJF,

    Thanks - I've not got the instructions for this instrument (fitted to Galadriel by the last owner) - so now I know what to do.

    The Forum does it again...

    I will have a fiddle in the week when I go out and get it reading more accurately.

    No more 8 knots for us, then
    Mike

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