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MultiThom

Drag behind speed sensor

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Before GPS, there were speed sensors that didn't require a through hull transducer (not pitot).  They just dragged behind and twirled like  a spinner fishing lure--they were useful in small slow boats or plastic boats or boats with no electrical system where paddlewheels were not practical.  I was looking for one and either I don't know what they are called or no one makes one anymore.  Anyone seen one lately?

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Yah, Thanks, I think that is the principle of the thing, but 20 years ago or so there were dozens and made of plastic...only ones I see on eBay are ancient brass. 

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48 minutes ago, MultiThom said:

Yah, Thanks, I think that is the principle of the thing, but 20 years ago or so there were dozens and made of plastic...only ones I see on eBay are ancient brass. 

Yep. Mine is an early 1900’s version displayed in my den. Too expensive to drag behind a boat when an out of date iPhone with gps and a free ap will give you SOG and COG for virtually free. 

If you want old school, tie some knots in a piece of small stuff and run it out, counting the knots run out in a defined period of time. Might take some effort to calibrate it. Real old school. 

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Take a look at these... http://www.knotstick.com/

 

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Thanks, Zack.  That works on a different principle (pull a washer behind you and it stretches a spring).  Only works to 9 kts. 

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I still have a Knotstick.  Remember those?  I use it to calibrate the electronics.

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