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Go Back   SailNet Community > General Interest > General Discussion (sailing related) > Paddle Wheel Speedometer
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Thread: Paddle Wheel Speedometer Reply to Thread
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Topic Review (Newest First)
03-23-2013 06:52 AM
jameswilson29
Re: Paddle Wheel Speedometer

Quote:
Originally Posted by capta View Post
...
I also find a speedo a welcome addition to our GPS info.
I, too, appreciate having a speedo in addition to GPS. Knowing how fast you are going through the water and over the ground is very useful information in many situations in tidal waters and in the ocean where there are currents.
03-23-2013 03:48 AM
SchockT
Re: Paddle Wheel Speedometer

Quote:
Originally Posted by capta View Post
If you're sailing in places like the PNW with lots of debris in the water, like logs, perhaps this was to protect the speedo impeller?
I also find a speedo a welcome addition to our GPS info.
The impeller is probably more vulnerable to that stuff in the traditional location on the bow. We had an impeller get knocked right out of the thru-hull by a chunk of wood during a distance race. We didn't know about it until someone jumped down below to get something and splashed into ankle deep water!

I wonder what the flow on the keel would be doing when the boat is heeled over, and maybe making some leeway. Would it flow straight back the way the impeller is aligned, or will there be a down element to the flow angle? That would affect the accuracy of the knot meter I would think. So are they trying to straighten a bit of the flow at the knot meter?

Whatever it is it is a very strange thing to have sticking out of the side of your keel.
03-23-2013 12:53 AM
Fstbttms
Re: Paddle Wheel Speedometer

Quote:
Originally Posted by Cmdr311 View Post
I think the purpose is to keep seaweed from fouling the paddle wheel. I can always put it back on next year if the speedo fouls excessively.
I doubt it. In 20,000+ hull cleanings, I have never seen seaweed foul a knotmeter paddlewheel.
03-22-2013 08:38 PM
capta
Re: Paddle Wheel Speedometer

If you're sailing in places like the PNW with lots of debris in the water, like logs, perhaps this was to protect the speedo impeller?
I also find a speedo a welcome addition to our GPS info.
03-17-2013 09:44 PM
outbound
Re: Paddle Wheel Speedometer

Agree with S man need both to figure out set and performance in real time . If growth,weeds etc. are a concern can use ultrasound speedo Airmar cs4500. airmar part# 44-063-1-03 or Raymarine part # 44-063-1-03. Never fouls. No maintenance. Never have to pull it out to clear and hope you get the plug in before your boat sinks. Cool piece of kit but dear.
03-17-2013 09:28 PM
Cmdr311
Re: Paddle Wheel Speedometer

Agree on the odd placement. I only sailed it a few times in the fall before we hauled her for the winter. I didn't notice any speed differences from one tack to another. My first reaction when we hauled her was, "What the...?" I think I'll take it off unless someone who knows its benefits pipes up. I can always put it back on next year if the speedo fouls excessively.
03-17-2013 09:21 PM
Sabreman
Re: Paddle Wheel Speedometer

Quote:
there any reason to keep the speedometre in this day and age of GPS?
As other posters say, Speed over water is very different than SOG and useful to know. What many people don't realize is that the GPS speed is an average over a longer period of time and not an instantaneous velocity. Thus, you could be slowing and not know it for a minute or two. SOW is an important piece of information when determining the effect of sail trim.

Example - last summer, we eased the traveler 2" and saw an immediate 0.5 kt increase in boat speed. With a GPS, the effect would have been averaged out and difficult to determine when factored with other variables.

I don't look at GPS speed when determining performance.
03-17-2013 09:12 PM
Faster
Re: Paddle Wheel Speedometer

Quote:
Originally Posted by mad_machine View Post
there any reason to keep the speedometre in this day and age of GPS?
SOG is not particularly helpful when you're trying to trim sails for best speed through the water... For the full picture you need both..

That an odd placement for a paddlewheel.. do you notice a big difference in indicated speed from one tack to another?... btw I'd probably pull that 'bracket/diverter/tuningfork/whateveritis...'
03-17-2013 09:02 PM
Cmdr311
Re: Paddle Wheel Speedometer

Yeah, I've wondered if it might function like a vortex generator on an airplane wing to align the flow of water over the paddle wheel?? Nobody in my boat yard has seen anything like it before. I'm about to paint the bottom and am considering taking it off.
03-17-2013 08:46 PM
SchockT
Re: Paddle Wheel Speedometer

Quote:
Originally Posted by mad_machine View Post
there any reason to keep the speedometre in this day and age of GPS?
Speed over water is different from speed over ground. If you sail in areas where there are a lot of currents it is useful to have both pieces of information so you know how much current you have with or against you. In our waters being aware of such things can get you to your destination faster.

As for the "tuning fork" I have never seen the like! Maybe it is supposed to align the flow with the knotmeter transducer?
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