Knotmeter question

Big E · Post by **Big E** » May 19th, '09, 17:29

Every year the impeller unit gets clogged with funk within the 1st couple of weeks after launch. Is there any kind of lube/protectorant I could use before launch to avoid this problem? it is coated with antifouling paint already...all suggestions would be appreciated.

Warren Kaplan · Post by **Warren Kaplan** » May 20th, '09, 05:45

I feel your pain and I haven't come up with anything that works. Then again...I don't care anymore. For my purposes reading my speed over the ground (the one that counts to me) directly from my gps solved the problem. I usually know which way the tide is going so I have a good idea what I'm up against. I really haven't needed to know my speed through the water if I know the tide flow. My knotmeter hasn't worked for about 3-4 years now and I don't miss it one bit.

Dean Abramson · Post by **Dean Abramson** » May 20th, '09, 08:03

I can often free mine by motoring backwards as fast as I can. Allow plenty of room, and have fun steering that rascal!

Dean

Ray Garcia · Post by **Ray Garcia** » May 20th, '09, 08:07

Same here, it started towards the middle of the season though. The boat would have to be taking on some real momentum before the knotmeter would register. Towards the end it just quit. When the boat was hauled I removed the paddle (held in place with stainless steel pin) and soaked it a few days in white vinegar to clean off all the crud. Came out looking like I just bought it. This year I painted it with some transducer paint I had left over. Good thing I tried spinning the paddle, the paint, which is thick, sort of glued up the works. I pulled the pin and cleaned it up a little with a toothpick. It is spinning freely again. Let's see what happens this season. My luck a piece of seaweed will clog it.

KVickers · Post by **KVickers** » May 20th, '09, 08:58

I always used to just tie a length of line to the bow, hand the bitter end to my son and toss him overboard. He'd swim under and free it up! After the first few times, if he saw the know meter stop, he'd just look over at me and shrug saying, "I guess it's time to get the rope, huh?" I'd nod and it was running again in no time atall.

Carter Brey · Post by **Carter Brey** » May 20th, '09, 10:36

I keep a dummy plug in the knotmeter through-hull, using GPS for my SOG. I test the knotmeter impeller by hand periodically and had DMI refurbish the instrument, but I just keep it in reserve in case the GPS fails and I need to know my approximate speed for dead reckoning. In the meantime it stays dry and free of growth underneath the vee berth.

Carter

Ed Haley · Post by **Ed Haley** » May 20th, '09, 11:43

It's a good idea to clean the knotmeter impeller before launch but I think the real culprit is the stuff in the water when you launch the boat. All the floatsum and flotsum around the launch area can get in the impeller and then take its time to work out.

Even picking up a piece of grass while sailing may stop the impeller from functioning for a while.

If it spins free before launch you've done all you can. The rest is luck.

Matt Cawthorne · Post by **Matt Cawthorne** » May 20th, '09, 11:49

I keept the blank plug handy and remove the knotmeter from the inside and replace it with the blank plug. A minute or two with an old tooth brush and it is all clean. I then just swap out the plug with the knotmeter and all is well. Typically only a few buckets worth of water get in during this process. Don't forget to put the pin and retaining ring back in place.

During the last 7 or 8 years I have been painting a very thin layer of bottom paint on the impeller. That seems to keep the impeller reasonably clean. I use Micron-extra.

M. R. Bober · Post by **M. R. Bober** » May 20th, '09, 22:01

Matt Cawthorne wrote:I keept the blank plug handy and remove the knotmeter from the inside and replace it with the blank plug. A minute or two with an old tooth brush and it is all clean. I then just swap out the plug with the knotmeter and all is well. Typically only a few buckets worth of water get in during this process. Don't forget to put the pin and retaining ring back in place.

During the last 7 or 8 years I have been painting a very thin layer of bottom paint on the impeller. That seems to keep the impeller reasonably clean. I use Micron-extra.

I do the same thing. Although with the Raymarine thru hull/sender very little water floods into the bilge. I skip the bottom paint.

Mitchell Bober
Sunny Lancaster (where we use dummies to plug holes in the hull,) VA

mattlydon · Post by **mattlydon** » May 22nd, '09, 08:08

airmar makes the cs4500 ultrasonic speed transducer - no wheel, accurate to .1 knots (so I read).

http://www.airmartechnology.com/uploads ... CS4500.pdf

The only trouble is that they cost $700

matt

bottomscraper · Post by **bottomscraper** » May 22nd, '09, 09:55

Our speed transducer has a typical season working lifespan of about 2 weeks. I tried transducer paint and I think it only made it worse. This year I used Micron Extra, we will see if that does any better. The location (deep in side of bilge) is just too hard to access mid season.

Here is something else that could fill the hole and might be more interesting!

http://www.gemeco.com/PDFs/ca500_rC_lr.pdf

Gary M · Post by **Gary M** » May 22nd, '09, 21:50

For some reason I find it hard to enjoy my boat when something isn't working, so I decided not to install a knotmeter.

As a matter of fact, I didn't install a lot of things!

When you own a 22 it is pretty simple.

Hardly moving, figure 1 to 1 1/2

Moving pretty good, figure 3 to 4.

Big smile, and eyes, figure 5.

Good enough for DR!
Gary

The Cape Dory Board

Knotmeter question

Knotmeter question

Cheap trick

My Solution

Knotmeter

knotmeter sticking

Mr Bober will chastise me for this

No, I won't.

wheel-less knotmeter sensor

Maybe a better use for the hole?

Keepin it simple