Can't figure out what this is

[Hudson Force]

It looks identical to a knotmeter that I used to have in the 1970's. There would have been a plastic paddle-wheel on the water side with a small magnet on one of the paddles that would produce a count at each full rotation and interpreted to speed. During bottom cleaning the plastic paddle-wheel was probably knocked off with the barnacle growth leaving a flush plastic disc that would not be easily seen. Typically there was a blank plug to fit into the through hull while cleaning the paddle-wheel transducer.

I would agree that it's best to glass over this well during a hull out in a boat yard. This is old technology with no modern use.

[Rustic Charm]

Originally Posted by Hudson Force

It looks identical to a knotmeter that I used to have in the 1970's. There would have been a plastic paddle-wheel on the water side with a small magnet on one of the paddles that would produce a count at each full rotation and interpreted to speed. During bottom cleaning the plastic paddle-wheel was probably knocked off with the barnacle growth leaving a flush plastic disc that would not be easily seen. Typically there was a blank plug to fit into the through hull while cleaning the paddle-wheel transducer.

I would agree that it's best to glass over this well during a hull out in a boat yard. This is old technology with no modern use.

My boat still has one of these 'knott' meters. But you make it sound like its ancient history you know there still quite common, you can still buy them?

[Rustic Charm]

Originally Posted by Stu Jackson

Count me in, makes three.

What in earth are you guys talking about

What's a 'lead line'

Do share

[Cheechako]

Originally Posted by Hudson Force

It looks identical to a knotmeter that I used to have in the 1970's. There would have been a plastic paddle-wheel on the water side with a small magnet on one of the paddles that would produce a count at each full rotation and interpreted to speed. During bottom cleaning the plastic paddle-wheel was probably knocked off with the barnacle growth leaving a flush plastic disc that would not be easily seen. Typically there was a blank plug to fit into the through hull while cleaning the paddle-wheel transducer.

I would agree that it's best to glass over this well during a hull out in a boat yard. This is old technology with no modern use.

I think it was established that it is just inside mounted...?

[Hudson Force]

Originally Posted by Rustic Charm

My boat still has one of these 'knott' meters. But you make it sound like its ancient history you know there still quite common, you can still buy them?

Well, I guess it's ancient history for me. I never liked mine. It was often becoming fouled and the idiots in the boat yard kept scraping my paddle
wheel off during bottom jobs.

I must admit that I did like having the boat speed relative to the water when mine was working!

[Don C L]

Originally Posted by Rustic Charm

What in earth are you guys talking about

What's a 'lead line'

Do share

Argh! Ye must not be in the club, mate! But then again ye might be let in on a pass if ye have a Walker Log on yer boat! Paddlewheels are old? I went in a while back inquiring as to how to purchase a Walker Log and they laughed me out of the place!

edit: Good God, they call it "ancient technology!"
http://exploration.marinersmuseum.org/object/lead-line/

[Rustic Charm]

Originally Posted by Hudson Force

Well, I guess it's ancient history for me. I never liked mine. It was often becoming fouled and the idiots in the boat yard kept scraping my paddle
wheel off during bottom jobs.

I must admit that I did like having the boat speed relative to the water when mine was working!

Mine is ok 'if' I remember to undo it and clean it before a trip. And I don't like doing that because firstly I have to remove all the contents of a locker under my settee and then after cleaning it I have to empty the bilge again of the water ingress. But, once it's going and I'm under sail it generally works well for the rest of the voyage.

So if a paddle wheel is 'old' techno, what's new to replace it?

[Don C L]

Originally Posted by Hudson Force

Well, I guess it's ancient history for me. I never liked mine. It was often becoming fouled and the idiots in the boat yard kept scraping my paddle
wheel off during bottom jobs.

I must admit that I did like having the boat speed relative to the water when mine was working!

I've got one even older I 'spect, a knot log mounted just above the keel, that mechanically turns a cable through the hull. Works great! Still amazingly accurate! If it ever breaks I'll be in trouble finding parts though.

[Jim Cate]

Originally Posted by Rustic Charm

Mine is ok 'if' I remember to undo it and clean it before a trip. And I don't like doing that because firstly I have to remove all the contents of a locker under my settee and then after cleaning it I have to empty the bilge again of the water ingress. But, once it's going and I'm under sail it generally works well for the rest of the voyage.

So if a paddle wheel is 'old' techno, what's new to replace it?

g'Day RC,

You can reduce fouling of the knotmeter by... would you believe... putting some anti-fouling paint on it! Pull the whole transducer, push the axle pin of the paddlewheel out sideways and remove the wheel. Carefully clean all growth from the paddles AND from the concave cavity in which it spins. Clean with acetone. Using a Q-tip, coat all the surfaces with a thin coat of left-over bottom paint. Carefully remove any that slops onto the hub of the wheel where the pin comes out. When dry, reassemble and install. Check to be sure that the wheel spins freely. If not, clean up wherever it is hanging up.

This lasts us for a few months with no fouling. Easy to re-do when it looses effectiveness.

Jim

[JPA Cate]

RC,

After you have done as Jim suggested, when you start to get a little growth on it, the log readings will be lower than the actual speed through the water in neutral tide conditions. That is a hint to do the following, after you're moored or at anchor. Put enough white vinegar to cover the paddle wheel into a coffee mug or a plastic tub, and soak the fitting to soak the paddle wheel. The acid in the vinegar eats off the calcareous marine growth. Repeat as needed.

Ann

[Rustic Charm]

Jim and Kate great advice. Thank you, I'll do that. both of them. I'm down on the boat today and was going to take the paddle out fir the winter so I'll clean it with vinegar to start with.

[Boatyarddog]

Originally Posted by ramblinrod

It definitely is a transducer. If it penetrates the hull liner, but not the hull, it is a depthsounder transducer, someone has likely epoxied to the hull to shoot through it.



The wire laying in the galley would have gone to an old analog sounder display, that may have been mounted on a bracket at the nav station, or that swung out into the companionway.



Certified Raymarine Installer

Don't think a shoot thru the Hull transducer would have a screw on cap.
The ones I've installed didn't.
They were required to be epoxied or submerged in glycerin or oil.
Could be a type of submerged transducer.


Sent from SV Cloud Duster

[Boatyarddog]

Originally Posted by Rustic Charm

What in earth are you guys talking about



What's a 'lead line'



Do share

I believe a lead line is use for depth measuring, and bottom condition.


Sent from SV Cloud Duster

[TrentePieds]

Quote: "What's a 'lead line'"

Are you serious??? Go ask Mark Twain ;-0)!


A lead line is a device for measuring depth of water. Go here:


https://en.wikipedia.org/wiki/Depth_sounding


In the bottom of the “lead”, literally a slug of lead with an eye at the top to attach the line, is a recess. Into this recess you put tallow. When the lead comes up, the bits of sea bottom stuck to the tallow will tell you what your holding ground is for anchoring. There is a set pattern of knots and bits of cloth and leather that are used to mark the fathoms along the line so even in pitch dark you can still take your “soundings” by feeling these distinctive marks. "Mark the twain" is the second mark on the line, and the author took his pen name in commemoration of his days as a steamboat pilot on the Mississippi.


It was the “arming” with chewing gum instead of tallow that MySaintedMother objected to.


In TrentePieds I just use as many overhand knots tied close together as corresponds to the depth in fathoms since I only ever anchor in depths of six to eight fathoms. The “lead” is a common fisherman's “sinker”. No provision for “arming”, but around here, with our excellent charts and well frequented and known “holes”, it doesn't matter


Here is an old focsl shanty that I love: Two tunes, the first the traditional RN version going back to the time of Trafalgar, the Glory Days of the RN after whose people and ships so many B.C localities are named, and the second a more modern version embraced and enthusiastically sung by “Newfies”. Neither of these renditions is in true chantyman style, but never mind... :-)

https://www.youtube.com/watch?v=d_2g_kNTBek

https://www.youtube.com/watch?v=-Dmpz5QeR_g

TrentePieds

[Hudson Force]

Originally Posted by Rustic Charm

................
So if a paddle wheel is 'old' techno, what's new to replace it?

Well, here you are correct again! The paddle-wheel in the water provides you with your speed relative to the water and a knottmeter function using GPS satellite data gives your speed related to coordinates. Having both gives you current set and drift information.

There is no substitute that I know of for the speed relative to water data. I ditched mine with my reliance on my GPS data. I can subjectively infer current data from progress, but not with the accuracy of having both inputs.

My coastal cruising habits present me with more dynamic current shifts than long offshore passages, but often more visual clues of the current. I guess people choose their tools by their use and experience.

Bottomline: Your right,- I don't know of a substitute