Preventing growth on a thru-hull speedo

[Kings Gambit]

Larry, I have no idea what "relative current" is. But I think you mean the difference between SOG and STW.

Current is current. It's either going with me or against me. In many, many cases, like KG humorously said, we don't "need" these things. But I sail regularly in a place where the current is either on my nose or behind me. Its velocity becomes important in passage planning and ETAs and the like, and I just, well, uhm, like to know.

If folks just go out and sail around, or even just sail across a current and back (except the English Channel ), it's less of an issue. They could care less.

I like things on my boat that are installed to work. When my knotmeter stopped working last year, I investigated why it didn't, fixed it, photographed it and wrote it up for Catalina's Mainsheet magazine. I got help right here from skippers helping me with BNC connectors.

I don't believe the GPS system will ever fail, but if my two on board units do fail at the same time, my knotmeter is one very important piece of navigation instrumentation that I find is pretty essential.

Otherwise, nah, I don't need it.

Those guys in predicted log competitions using only the following:

What is a Predicted Log Regatta ?
"It's a fun way to practice navigation and satisfy your competitive nature in a friendly environment while enjoying time on the water in your boat. This is not a test of speed - it's a test of navigational accuracy. It doesn't take a special boat or high priced electronics. All it takes is: A Boat.----- A Compass.----- A Tachometer.----- A Chart."

 

[Benny17441]

I find that the two step method works better for me. I remove the transducer and immediately cover the hole with a rag then I pick up the plug and slowly remove the rag while I quickly insert the plug. I do it with planned and decisive moves to prevent any fumbles.

 

[alexco38]

http://www.panbo.com/archives/2009/10/airmar_cs4500_part_i_reliable_boat_speed.html

non-paddle wheel speed sensor. Uses ultra-sound, no moving parts.

 

[seadaddler]

A depth meter is a real need here in Florida and any other place for sure and a good
smartphone or handheld GPS is all that is needed.
Yes most will say paper charts are important and agree but when you are sailing around
or coming into your port some times a few feet is the difference between running aground
and staying in what depth your boat needs from running aground or when tides are changing
and you are leaving your dock and notice the depth is slowly dropping too close to what yoy need,so depth is really the only needed piece of equipment.
Nick

 

[Maine Sail]

Options:

-Pull the transducer when not in use
-Move to an ultrasonic transducer
-Pull it and clean it once every couple of weeks

 

[Graycruiser]

Current is not an issue for us on the Chesapeake Bay, so I pulled the speed transducer 3 years ago. GPS speed if fine for our needs. There is a device for about $100 that will use the GPS NEMA speed message and translate it into the NEMA speed thru the water. This will at least allow a wind instrument to provide true wind calculation. Still no current info.