Speed Sensor Cleaning - While Afloat? - SailNet Community
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post #1 of 30 Old 08-31-2011 Thread Starter
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Speed Sensor Cleaning - While Afloat?

Howdy! I have a DataMarine speed sensor that is of the paddle wheel type and mounted via a thru-hull. Mine needs cleaned.

In addition to diving on it and waiting til the next haul out, I have read that I can remove the sensor while afloat. I have no doubt that the water comes onboard FAST when the sensor is pulled (I envision a garden hose turned on full blast). Obviously, having the plug in hand and a spare person just in case something unexpected comes up are requirements. Question is; has anyone actually done this? Is the flow of water as significant as I have described? Any advice/suggestions (including wait til haul out)?

Thanks!

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post #2 of 30 Old 08-31-2011
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As long as you're quick, the amount of water that comes through before you put the plug in won't sink your boat. It is, however, alarming the first time.

No one I know even bothers any more. They use their GPS.

Donna


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post #3 of 30 Old 08-31-2011
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Some transducer through hulls have a flapper that closes behind the sensor when it's pulled.. maybe you'll be lucky and have such a one.

However pulling the sensor is certainly doable but it can be alarming how fast the water wants to come in... but it's a pretty big hole and even though there's likely less than 1 psi it looks like quite the gusher. When I do it I have a plug handy that I insert instead of the sensor so that when we haul out there's no concern of a strap damaging the impeller. A second person to stem the flow would be good if you're just wanting to pop it out, clean it and reinsert it.

You'll end up with a couple of liters in the boat to mop up if you're quick.

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No one I know even bothers any more. They use their GPS.
I still rely on 'through the water' speed indication for sail trim.. and comparing it with the GPS keeps me informed about how much current is affecting our passage (around here it can be 2 knots or more at times)
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Last edited by Faster; 08-31-2011 at 08:06 PM.
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post #4 of 30 Old 08-31-2011
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It helps to have a small brush.. ( a stiff bristle toothbrush works ) to clean it with ready when you pull it. If I'm doing a quick clean..the bilge pump just pumps the water out...for a good cleaning, I'll pop a plug in...don't force anything in tight..just enough to stem the flow....

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post #5 of 30 Old 08-31-2011
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It takes all of about two seconds to pull the impeller and replace it with the dumb plug. You can easily press the pin out of the paddle-wheel and remove that and pull the paddles and then clean the paddles and housing. I do this on our boat about once a month. I spray the paddle-wheel shaft with a little SailKote to ensure the wheel spins freely and then apply a little Neosporin to the paddle-wheel and the plug to slow down and growth. When the water's cold that's good for about 3 months. During the summer months--here in Florida-- it's good for 4-5 weeks.

FWIW we use a "KnotStick" to calibrate the Knot-meter. Speed through the water may not be useful to some, but we find it beneficial went evaluating apparent wind and of course, maintaining a DR.

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post #6 of 30 Old 08-31-2011
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Have some one with a saucepan or wok ready to redirect the waterjet.

Make sure the dumb plug is lubricated and although stress raising it is not difficult to do and less than a 1/2 gall of water should find its way into the bilges.
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post #7 of 30 Old 08-31-2011
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Quote:
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No one I know even bothers any more. They use their GPS.
On a fully integrated system the knotmeter used in conjunction with the GPS and fluxgate compass will tell you your set and drift. I find that quite handy. Also just comparing the knotmeter and the SOG will help you with understanding current.

Racers use the knotmeter because there is less lag time. SOG is an average over time.

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post #8 of 30 Old 08-31-2011
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I have the same Datamarine knot meter. The paddlewheel is fat compared to say, the Signet brand, and mine is way down low, near the centerline. The first time I swapped in the dummy plug, I almost shat myself the water came in so quickly.

You get over it. Just have the dummy plug handy, and a wooden bung handy, in case the water pressure ejects the dummy plug somewhere.

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post #9 of 30 Old 08-31-2011
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Hey,

If you don't have the plug, a regular wood plug will work too. You will get some water in the boat, probably around a quart.

Be prepared for A LOT of creepy crawly type critters on the sensor. I place the wheel in a plastic bag and then do a nice cleaning job with the sensor inside the bag so the critters don't go all over.

Barry

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post #10 of 30 Old 08-31-2011
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Heh, I did this a couple of months ago, it was almost as nervewracking as the first time she went back in the water after I fitted the new transducers. Anyway, my speed sensor came with a plug. I took a couple of old towels and arranged them around the through-hull, pulled the pin and then quickly yanked out the sensor and popped in the plug. Water column reached about 8 inches high, must have been a few pints of it in the second or two the hole was open. Pretty terrifying, but the little bit that the towels didn't catch just ended up in the bilge. You want to really picture what you're doing, fumbling with the plug can only end in tears

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