has anybody out there solved the problem of keeping the rotating knotmeter under the boat free of whatever grows there and stops said meter from working? it takes less than a day after a diver clears ours before it's fouled again.
pinwheel knotmeter
- Thread starter mortyd
- Start date
- Status
I pull it and install the blank plug every time I leave the boat. After a lot of pulls, I only get about 1/2 cup of water in the bilge with each exchange. I tried the special antifouling paint made for transducers; didn't work any better than nothing at all.
antifouling paint - I wheedle some from the yard, but they also make some for the pinwheels - don't know if that stuff works or not.
I have a '92 Catalina 30 with the AutoHelm ST 50 probably the same original equipment that you have. I was cleaning it all the time too and finally the wheel crumbled. I'm happy getting my speed from a handheld GPS and I'm getting ready to look at GPS aps for an I-Pad. I'm just not sure that the rotating knotmeter is worth the pain, aggrivation and slight additional drag.
On the other hand I'm not thrilled with the non working display in my bank of instruments.
So about paint...I haven't found anything that keeps the knotmeter clean for very long and it's probably becoming as obsolete as the LORAN which also came with my boat.
On the other hand I'm not thrilled with the non working display in my bank of instruments.
So about paint...I haven't found anything that keeps the knotmeter clean for very long and it's probably becoming as obsolete as the LORAN which also came with my boat.
greenlight, your gps gives you speed over the earth, not through the water; understanding this difference is essential to understanding your boat.
Mort, The speed over ground is what is really important anyway. Its speed made good that's more important. The wheel is affected not just by the boat movement but by current running over it, hence it is NEVER really accurate. Also the crud that y'all are fighting to clean affects its performance & accuracy. Just a lil crud buildup will induce drag & affect the speed at which the wheel does, or doesn't turn. The knotmeter also does not take into account lateral forces slowing the boat, tidal current, etc. that effect speed. GPS is far more accurate. I have the answer to solve the problem of the rotating knotmeter: Get rid of it! It's a piece of history - about as accurate as Loran. That's why they don't even sell them anymore. GPS is the wave of the future. Check it out sometime. You can pick up a Garmin handhled for a hundred bucks. Why anyone wants to fool with the knotmeter wheel anymore is beyond me. An apparent wind indicator is a much more valuable sailing instrument then any aboard. As far as doing things old school, I could also use a lead line, but that would just be silly.
I've used the Transducer Paint that is sold at West Marine on my paddle wheel and find it to be somewhat effective, meaning that I only have to clean it about every 90 days or so. It comes in a container about like finger nail polish so it's just a convienient size to keep on board.
One advantage of having the paddle wheel operational (and calibrated) is that it's one more way to know what the current is doing when compared to GPS speed. I don't personally think it's an outdated instrument, but, like so many other things about sailing, it might just depend on how you use your boat.
Then again, I used a lead line to calibrate my depth sounder... yes I have a lead line!
DanM.
One advantage of having the paddle wheel operational (and calibrated) is that it's one more way to know what the current is doing when compared to GPS speed. I don't personally think it's an outdated instrument, but, like so many other things about sailing, it might just depend on how you use your boat.
Then again, I used a lead line to calibrate my depth sounder... yes I have a lead line!
DanM.
- Dec 30, 2009
- 680
I replaced mine with a depth sonar transducer, for my GPS. I am happy knowing my arrival destination time, which my GPS figures out for me according to the speed it sees the boat going over the water. The other thing GPS speed does for me is, did my sail trim adjustment help me??As far as, am I going 4 or 5 knots or mph, really I could care less.... Red
The speedo(speed thru water) is a primary performance indicator....You trim your sails with one eye on the tells and one on the speedo.... it's very important if you race.... that said...I rarely use mine anymore, 'cause the gps is no maintenance and I've become lazy. In the past I've smeared Desitin on the paddles.. someone here suggested mixing the diaper rash product with a little lithium grease to make it last longer.
Joe, I haden't heard of the desitin trick, interesting. I guess the zinc oxide could form a protective barrier. As I said I gave up maintaining that knot wheel a long time ago. Futile in my opinion. To Dan: Yes I have actually used a lead line as well, but I actually just used a cloth measuring tape with a wrench tide to the end of it for a weight. Talk about low tech! LOL.
- Status