Few questions about fairing block transducers

[IOLANI]

Doing some last minute touch up on the new bottom paint. This boat has several old transducers in the bottom that I believe have been abandoned or are no longer being used. I noticed one is a bit odd in that it has a couple of plastic ears that protrude down which holds a plastic ball about the size of a marble which spins freely between the ears. Hard to tell but looks like the round sphere may have had spokes or small fins protruding at one time like a little paddlewheel. Sorry I forgot to take a picture anybody know what this is by the description?
Is it normal practice to just leave these in place when no longer in use or should you take the time to remove them and glass the hole back in...?

Question #3...on the ones which are in use is it ok to sand or scrape the face clean or can this affect the operation?

[BJones]

Doing some last minute touch up on the new bottom paint. This boat has several old transducers in the bottom that I believe have been abandoned or are no longer being used. I noticed one is a bit odd in that it has a couple of plastic ears that protrude down which holds a plastic ball about the size of a marble which spins freely between the ears. Hard to tell but looks like the round sphere may have had spokes or small fins protruding at one time like a little paddlewheel. Sorry I forgot to take a picture anybody know what this is by the description? Is it normal practice to just leave these in place when no longer in use or should you take the time to remove them and glass the hole back in...? Question #3...on the ones which are in use is it ok to sand or scrape the face clean or can this affect the operation?

Sounds like a speed in the water pick up. Totally mechanical. A lot of cruising sailboats have them...

[IOLANI]

Sounds like a speed in the water pick up. Totally mechanical. A lot of cruising sailboats have them...

Interesting. I’m convinced then that the little paddle wheel spokes are broken off it looks almost smooth like a marble but I can spin it easily with my finger. I could see that little wheel getting fouled with the smallest piece of seaweed or trash or a barnacle. Have they become obsolete with the advent of GPS or is there still a place for them ?

[Cricket]

Used to be a big thing, especially with Datamarine products. The guts holding the paddlewheel should be removable from inside the hull with pulling some sort of pin. I'm a big believer in less is more when it comes to holes in the bottom.

[Captain Ralph]

IMO, a paddle wheel is still a good tool. GPS offers speed over the ground, The paddle wheel offers speed thru the water.
If you enjoy old school of DR, it is speed thru the water that you need calculating vectors (set & drift) and such.
These last couple of years have had some fun watching our ole Berts speed displays vary running the upper St Johns river.

Finally got our fuel flow meter to use speed thru the water a few years ago. Took a while to understand how one days MPG numbers differed from the next days numbers so much.

[IOLANI]

Good stuff guys thanks. . I may just try and figure out which helm device it's connected to and get it working again. This boat still has a lot of vintage chart plotters and such on board.


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[Scarlett]

Those paddle wheel transducers were also used with wind instrument computers to calculate true wind speed and direction. Used more on sailboats.

[Play'N Hooky Too]

To answer your third question, do not sand the face of any transducer that is still in use. Also do not paint the face of it unless you are using the bottom paint specifically formulated for use on transducers.

I would remove the old transducers if you are certain that they aren't connected to anything. I would either re-glass the hole or use it for something else (intake for a washdown pump, bait tank pump, etc.)

[IOLANI]

To answer your third question, do not sand the face of any transducer that is still in use. Also do not paint the face of it unless you are using the bottom paint specifically formulated for use on transducers.I would remove the old transducers if you are certain that they aren't connected to anything. I would either re-glass the hole or use it for something else (intake for a washdown pump, bait tank pump, etc.)

Will do thanks.