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Old 28-02-2012, 00:26   #31
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Re: How Necessary is a knot meter

We had a knot meter once, more trouble than it was worth. Just use the GPS now.
I can't get my head around why people need any meters at all. Once you know your boat she tells you through your feet when she is happy. The sound of the wind in the rigging and the look of the sea tells you how much wind is blowing. A couple of bits of cassette tape in the shrouds gives you the direction. Telltales on your sails tell you how high to point.

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Old 28-02-2012, 00:27   #32
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Re: How Necessary is a knot meter

Found that the paddle-driven speedometer read about 1/10ths of a knot different from one tack to another on my former cutter.

Now with a motorboat, have no speedometer but do have tachometer and GPS. Despite the significant currents around here, one can equate RPM to speed through the water after some observation. But of course, speed over ground is what's relevant for navigation. The boat's sails boost SOG for a given RPM depending on wind strength/direction.
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Old 28-02-2012, 04:15   #33
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Re: How Necessary is a knot meter

BTW

How good are the propeller-less models?

I hate the fact that no matter how much I try, it seems our log gets stuck or slowed somewhere into the passage.

b.
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Old 28-02-2012, 06:28   #34
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Originally Posted by four winds
I agree, that would be for just long enough to clean it.

I would look for a new proper plug.

So the impeller threads into the housing? And turns out for cleaning, not pulled straight out?

I'm still looking for the paper manual, I think I have it somewhere.
My previous log plug was a half twist one with a steel dowel pin. The first time I pulled it I found the pin had sheared some time ago and the only thing holding it in the hull was corrosion, friction and bottom paint.

The new one plugs straight in and has a plastic threaded nut on the through hull. I lube the o-rings with vaseline.

I reckon the pin type are old design. Be prepared with a plug when you pull it...
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Old 28-02-2012, 07:01   #35
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Re: How Necessary is a knot meter

Our B&G knotmeter was pretty accurate. I used to pull it out when we were on the Chesapeake to keep it from fouling.

I'll tell you when I found it to be indispensible--offshore after crossing the Gulf Stream. You need to play the eddies, and if you get it wrong, you can lose a knot or two. Comparing the knotmeter (boat speed) to the GPS (speed over ground) tells you when you're in a fair or foul current. We would have a chart on the boat showing the eddies so we could plot a course to take advantage of the fair currents, or at least avoid the foul ones.
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Old 28-02-2012, 07:27   #36
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Re: How Necessary is a knot meter

To me, it's as important as a depth sounder for a back up should the real world ever intrude on my life.

REALLY? You must have "misspoken", because unless you have never been in skinny water, this may be true, but here in the "real world", the cruising world, skinny water is a fact of life. I had to say something, because the quote above in red is, in my opinion, really really bad advise for a new sailor that is looking at what to spend his money on. While arriving later than you thought because your knot meter petered out is not nearly as important as arriving "on time" on a sandbar or other obstruction.
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Old 28-02-2012, 07:49   #37
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Re: How Necessary is a knot meter

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Originally Posted by mrohr View Post
I'm a minimalist and do not find many instruments indispensable ,but most of us want to sail well and I find the speed log is the best instrument for any who want to get the best out of their sail trim and craft.
Exactly. It doesn't matter if it is accurate or not. It is the only instantaneous measure of relative boat speed.

Meaning, if I trim the main in a little, did I improve things or make them worse? With only GPS I have no way of really knowing, unless I try to calculate my average speed over several minutes. With a knot meter I know immediately. What the actual number is does not matter, but my indicated speed will go up, down, or stay the same. Whatever it does, I know the affect of my change in sail trim.

To me that is extremely worthwhile information.
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Old 28-02-2012, 07:57   #38
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Re: How Necessary is a knot meter

waterworldly, are you sure you read that right?

Looks like the statement supports the importance of a knot meter as well as a depth sounder.

Scanned for the post to see context but didn't find it in a quick scan of the thread.
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Old 28-02-2012, 08:28   #39
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Re: How Necessary is a knot meter

As far as trimming...I usually go by sail shape. Over the years I have been able to see if the air is flowing properly over the sail. It might be true that I could be off by .1 of a kt. but I doubt a kt meter could pick that up the way they fluctuate so much...well, at least mine.
Thank you everyone for the input...GPS it is then and a constant vigilant of log entries. In other words, I don't need to change any of my habits, save $300 and a little labor to plug another hole under the water-line.
Although I just splashed after a painful engine rebuild and drive-line, I am going to haul in 2 years for an epoxy bottom and rigging. I will also be changing other thru-hulls. Putting a few above the water-line and eliminating some. So this removal of the kt meter will just be an item on the long list. Thanx again.
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Old 28-02-2012, 08:43   #40
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Re: How Necessary is a knot meter

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I lube the o-rings with vaseline.
Better to use silicon grease. Vaseline is a petroleum product, and it will break down the o-rings over time.
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Old 28-02-2012, 08:49   #41
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Re: How Necessary is a knot meter

Both the paddlewheel and the sonic model for Ray Marine are made by Airmar. They recommend that when not in use they be pulled and stored till you go out to reduce growth, or use water based antifouling. I have both and the sonic one is very accurate, but it is around $600. Keep lots of orings around because the flapper valve eats them and I lube with vasoline too. They're a weird size and I can only get them from airmar or Ray Marine. I keep a spare flapper valve and snap ring around but never have had to replace them. I made a pvc scrub pole I keep on the dock that I can touch up the face of the transducers with if readings don't seem correct. Are they necessary for safe navigation? In my opinion, no, but you should have some method of determing distance travelled, but they are a handy tool and I am glad to have them to increase my DR data in determining position. Are they a pain? At my age anything invented later than the 19th century is, but that's the minimalist in me coming out.
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Old 28-02-2012, 17:24   #42
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Quote:
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Better to use silicon grease. Vaseline is a petroleum product, and it will break down the o-rings over time.
Old habits die hard - 30 years of vaseline. I must have an entire ocean of failed o-rings in my wake...

Also very much depends on the material of the o-ring but I take the point...
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Old 28-02-2012, 17:33   #43
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Re: How Necessary is a knot meter

if you have a gps, totally unecessary... for a cruiser.
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Old 28-02-2012, 18:02   #44
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Re: How Necessary is a knot meter

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if you have a gps, totally unecessary... for a cruiser.
I heard somewhere that "the one with the most toys, wins"!
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Old 28-02-2012, 18:02   #45
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Re: How Necessary is a knot meter

As JDS61 said I use my Taff Rail log for not only speed but distance run in 24 hrs, and still use DR everyday!! along with noon sites offshore. of course I use a GPS but don't need it LOL I to don't really like NEW Things Ive had to many of them go belly up on me over the last 50 yrs LOL so I Stick with what I know works and has worked for 1000s of sailors before me and I hope a few after me !! Just my 2 cents Bob and Connie
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