mechanical knot meter

[Jon Libby]

We have a VDO knot meter on the boat that has a propeller under the boat that is of course driven by the water going by it. There is a cable from that unit to the instrument, like I'm use working on in an older car (just gave my age away). Has anybody worked on one like this? The cable at the back of the intrusment is not turning, but as we move in the water I can hear and feel the cable slipping or missing at where the unit comes thru the bottom of the boat. I've tried to take the jacket off this cable at the fitting at this point but I'm afraid of breaking it or cracking the cable. There is a hose clamp holding the jacket to what looks like about a 5/16 (hollow of coruse) threaded rod. Does anybody know if this is a wet fittiing that will sink the boat if removed. Has anybody removed one of these units from the bottom of the boat.

I'll try and attach a photo for the unit on the bottom of the boat.

Thanks in advance
Jon and Arline
www.ericson-36c-kasidah.blogspot.com

 

[chuckshipp]

Jon,
Why would you still have that thing hanging down on your Boat, When I bought my boat about 10 Yr ago, I had a little propeller that looked like a water wheel hanging down, gurarantee It would stop working 24 hrs after I cleaned it up and put it back.
With the new Gps, I think that they would be or accurate, than any mechanical thing like that. I have a Garmin, Map 76, and it works great for keeping up with my speed. Just a suggestion.
Chuck

 

[jkm]

That picture reminds me of Jules Vern or maybe the Hunley.

 

[Jon Libby]

Well, we do have a GPS chart plotter that gives us our speed over ground. But when we moved the boat up the Hudson and across the Erie Canel we where fighting current. It would have been nice to know the real boat speed. Plus we are planning on cruising soon and will be watching our power comsumption. This thing doesn't need any power. I have thought of removing it but I think if it works keep it.

And about GPS speed readings. We have a good old Northstar and were out in big winds, got back to dock and were ask about our speed, (I'm never one to brag) and stated our speed as noted on the GPS. The old timer next to us with about the same size boat said "I can't get that kind of speed" out of his Caliber 35, "oh wait was that a GPS reading,...OK you weren't going that fast GPS is off more than right."

So If I had my knot meter working I could have checked, not that I care

 

[Jon Libby]

So I'm guessing, nobody else has this type of unit or seen it. If I get it out of the boat should I submit it to the maritime museum?

More later on the next project.

 

[tenders]

This spring I glassed over the hole for my knotmeter. Yes, speed through the water is nice to know in a current vs. speed over ground via GPS, but not so nice that it's worth the hole.

(Sorry, I've never seen a speed wheel like that either!)

 

[windjunkee]

the paddlewheel type of knot log is very important if you want to know your speed in the water versus your SOG. You won't be able to tell current set or drift without it. We have both the GPS information and the knotlog and it helps in getting current information.

Jim McCone
Voice of Reason E-32-2 Hull #134
Redondo Beach, CA

 

[Chris Miller]

without boat speed, how do your anemometers calculate true wind speed & direction?

and no, I've never seen one like that either- but it does look like it could be attached to a cam with a bunch of guys rotating it on the Hunley!

I have to agree with Chuck, long term I think you'd be better off spending the $350 and getting a new speedo... just my $0.02
Chris