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post #31 of 47 Old 05-04-2012
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Re: Dead Reckoning

For Casy and anyone else curious .My experience in the Arctic was sure different from temperate cruising. but no big deal.I could sometimes get a RACON fix ,good for 25 miles out but usually only one at a time. I was rarely more than 30 miles offshore and could get a sloppy Rf fix on CBC Inuvik. or a radar on a drill ship.I had most of them marked on the chart When rough, the compass just went round and round so steering relative to the waves worked pretty well as long as the wind was known and steady.Winds long ways away could cause surface currents of 3 knts.so it could get interesting. The ice was a different twist too.as were sunny midnights and moon rise over the pole come fall.As the nights got longer and darker guessing whether the approaching white thing is ice or breaking wave over the windshield became great fun on longer trips.
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post #32 of 47 Old 05-07-2012
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Re: Dead Reckoning

For you dead reckoners: What do you use to give you speed and distance covered?

Back before sat nav, gps and all, we used a log (a propeller and string towed behind boat and the mechanical device that gave speed and distance covered- seems you can only buy these used now). Seem relying on a thru hull log and its potential to get fouled without knowing is not reliable. With the mechanical towed log we would pull the towed propeller out of the water every 3 hours to check for fouling.
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post #33 of 47 Old 05-07-2012
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Re: Dead Reckoning

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For you dead reckoners: What do you use to give you speed and distance covered?

Back before sat nav, gps and all, we used a log (a propeller and string towed behind boat and the mechanical device that gave speed and distance covered- seems you can only buy these used now). Seem relying on a thru hull log and its potential to get fouled without knowing is not reliable. With the mechanical towed log we would pull the towed propeller out of the water every 3 hours to check for fouling.
Knotmeter. If I start to get concerned about its accuracy, I pull it and clean it. You can check the accuracy with a dutch log.

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post #34 of 47 Old 05-07-2012
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Re: Dead Reckoning

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Knotmeter. If I start to get concerned about its accuracy, I pull it and clean it. You can check the accuracy with a dutch log.
How do you stop the water when you pull the thru hull knotmeter? I have two old thru hull knot meters in my boat. Will remove all and glass in a patch on next hull out as I fear them getting knocked out and hole the boat. Which leads to next question: Why do not all these thru hull knot meters and depth sounders not require a seacock shut off? Seems these plastic "plugs" are an accident waiting to happen. Seems they could be designed to be insert into a seacock and if they were knocked out or started leaking you could pull them out and shut the seacock.

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post #35 of 47 Old 05-07-2012
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Re: Dead Reckoning

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How do you stop the water when you pull the thru hull knotmeter? I have two old thru hull knot meters in my boat. Will remove all and glass in a patch on next hull out as I fear them getting knocked out and hole the boat. Which leads to next question: Why do not all these thru hull knot meters and depth sounders not require a seacock shut off? Seems these plastic "plugs" are an accident waiting to happen. Seems they could be designed to be insert into a seacock and if they were knocked out or started leaking you could pull them out and shut the seacock.
Knotmeters must have a blank plug that is used when the knotmeter is pulled.



"Modern" knotmeters have a flap that stems the flow when the knotmeter is removed.

Wooden plugs can be stop the flow from a broken thru-hull.


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Last edited by jackdale; 05-07-2012 at 04:54 PM.
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Re: Dead Reckoning

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Knotmeters must have a blank plug that is used when the knotmeter is pulled.



"Modern" knotmeters have a flap that stems the flow when the knotmeter is removed.
How can a plastic plug meet ABYC standards ( I assume it does) when requirements are so strict for thru hull valves?
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Re: Dead Reckoning

The plug is the same material and diameter as the knotmeter. It is held in place by the same threads as the knotmeter. I pull knotmeters regularly to show my students how it is done.

Check the video I posted for other techniques.

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Re: Dead Reckoning

I made reference to the Dutch log, check here for info.

Knot/log calibration

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Re: Dead Reckoning

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The plug is the same material and diameter as the knotmeter. It is held in place by the same threads as the knotmeter. I pull knotmeters regularly to show my students how it is done.

Check the video I posted for other techniques.
Ok, good video, I love the attitude of those guys and how they abuse the crash yacht for the greater good. But I still don't see how basically a plastic thru hull plug that is usually not mounted very well on the hull is acceptable for a boat. I would not mount one and as stated plan to plug the two now installed. With all the debris in the water now there is a lot of stuff to hit and knock out the knot meter. By the way, ordered some of the orange forespare plugs that they showed in the video, mine arrived a couple days ago. Good to see they work, along with the collection of my wood plugs.

Last edited by casey1999; 05-07-2012 at 06:03 PM.
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Re: Dead Reckoning

Casy, that was called a taff rail log. You guessed it , mounted on the taff rail. Sharks can eat the prop so carried spares. Going into reverse could also eat em up.
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