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Old 14-09-2010, 06:26   #16
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Originally Posted by markpierce View Post
If the device is one one side of the keel as it typically is, it could be a matter of differing dynamics. If it really bugs you, install another one symmetrically opposed.
Yeah and when it drops to 2 kts on port tack I can stop looking at the inclinometer cuz the paddle is airborne - LOL...

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Old 14-09-2010, 07:08   #17
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I find speed-log to be helpful information -- but when cruising VMG is "king", and you can only get that reading from a GPS.

I do like to be able to compare GPS with water speed to estimate current but being a coastal sailor I can estimate current speed almost as accurately by looking at the wakes and eddies surrounding lobster floats and buoys, and get more accurate info on current direction that way. The speed-log also gives true wind (not just apparent wind) speed and direction on the wind meter, although I can estimate that too from other clues, and apparent wind is what rules my sail trim decisions anyway (except downwind when true becomes more important for safety reasons).

When using the boat just for day sailing or if not using the boat for a few days I change the transducer for the blank plug, so the paddle wheel doesn't foul. A towel laying in the bilge downhill from the plug picks up the one or two cups of water that come in during the quick transition.

Bottom line -- it's nice to have but not essential. It would become essential again only if the government or some catastrophe turned off GPS.

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Old 14-09-2010, 07:20   #18
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As stated above, the knotmeter is really valuable for trimming the sails for peak performance. Even as a cruiser where getting to my destination is the primary objective and where GPS SOG is the primary determinant - there is still room for a knotmeter. And that is to confirm that, yes, the sails are trimmed to max efficiency which will in the end contribute to getting to my destination quicker.
- - I have the removal transducer which is very handy as you can store it inside the hull and reduce the problem of sea life fouling the little paddle wheel. Problem is I nearly always forget to re-install it before departure. And if I do remember to install it, then I forget to remove it upon arrival and it clogs up with sea life.
- - If somebody "reverse-robbed" me (that is, held a gun to my head and forced me to accept the money) for about $800 +/- I would buy one of the electronic inductance models that have no moving parts. Then I could leave it installed forever (except for normal bottom cleaning). Otherwise, the knotmeter is a very low priority piece of equipment.
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Old 14-09-2010, 08:23   #19
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you'll never get a good sense of how you're hitting your polars without a knotlog.

when I have a medium-experienced helmperson on the wheel I'll often instruct them to forget about the telltales and just maintain a certain speed, especially going to weather. They learn to pinch the boat when the target speed is exceeded, and to foot the boat when they've slowed under their target. Amazing how many cruisers have never learned to sail a boat to its best VMG.
cruising is entirely about showing up--in boat shoes.
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Old 14-09-2010, 08:33   #20
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Well, there are cruisers who sail and sailors who cruise. With the first group generally cruising is more about going to great places in an economical conveyance - otherwise we would all just fly there. So comfort and simplicity takes the forefront and performance is put second. With the second group, performance (joy of sailing) is first and getting to the next destination an exercise in sailing acumen.
- - Their boats reflect their styles with the "barges" definitely being in the first group and the sleek rigs in the second. The first group likes to stop and smell the roses while the second group likes the smell of the ocean washing over the rails.
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Old 14-09-2010, 08:37   #21
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I consider the knot log and depth gauge to be essential items on any well-found boat. Both provide a wealth of info, are nearly bulletproof, and have a record of long life. If it weren't for the knot log's barnacle attracting capability, it might be about perfect.
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Old 14-09-2010, 08:40   #22
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Originally Posted by SailFastTri View Post
. The speed-log also gives true wind (not just apparent wind) speed and direction on the wind meter, although I can estimate that too from other clues, and apparent wind is what rules my sail trim decisions anyway (except downwind when true becomes more important for safety reasons).
True wind can be derived from GPS. Some instruments do refuse to calculate this, but the better instruments will do it.
The true wind derived from the GPS is slightly different from the true wind derived from the log. True wind from the GPS shows the wind that would be measured on land or a buoy anchored next to the boat. In my opinion this is the most useful and correct “True wind “, others disagree, but my experience is that true wind derived from the GPS is not only more useful, but more stable and accurate, as minor miss calibrations of the log affect true wind derived from this source and degrade the accuracy annoyingly
Tack and gibe on most boats using the log to derive the true wind and you will find the true wind varies considerably. Do so in a boat using the GPS speed input and the value is very steady (assuming steady true wind).
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Old 14-09-2010, 10:18   #23
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Originally Posted by SvenG View Post
Maybe nuts today but that is essentially where the term "knot" comes from. Using a chip log, how many knots passed through your fingers in a given period of time gave you your speed measurement in knots.

But you probably knew that.

I knew the technique but didn't know that's where knot comes from! Learned something new today!
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Old 14-09-2010, 15:02   #24
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Similarly mine died (3 times) so I stopped fixing it. 8 years and 26000 miles later I was really good at judging boatspeed without it.

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Old 14-09-2010, 15:15   #25
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G'Day all,

Am I the only one who carefully puts a thin coat of anti-fouling on my paddle wheel? Takes a Q-tip, a few drops of leftover paint and a couple of minutes, lasts for a few months, and markedly reduces fouling.

Do be careful to not get paint into the bearing area, though!


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s/v Insatiable back in MBTBC marina, waiting for next eye jobs to be done
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Old 14-09-2010, 16:45   #26
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I liked my old knot-log so much. that the last time I hauled the boat, I pulled out and plugged another useless hole in the bottom of the boat.
I would rather know VMG which is what the boat is actually doing. Speed thru water is only good if there is no current, traveling the GIWW last year according to the knot-log we were making 7 1/2 knots under power at 1200 RPM.s. It took us 2 1/2 hours to go 5 niles, going against an approximate 4 knot current. VMG was dead on the money.
I don't cruise at maximum speed, but at comfort speed, a whole lot nicer ride and keeps the ADMIRAL happier....
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Old 14-09-2010, 16:54   #27
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My higest priority as far as instrumentation goes is wind speed and direction, and water depth. Everything else I don't worry about so much. I look at the GPS for speed, but since I am not racing, I don't get too excited about the speed. Instead, I see how my boat is behaving in the seas, and I adjust my sail trim and course for the best ride rather than maximum speed. When I am out cruising, it doesn't matter if I am going a half knot faster or slower on a knot meter. I will sail at a speed that doesn't create a demolition derby on board Exit Only, and that doesn't incite the crew to mutiny. Sometimes I go fast, and sometimes I go slower, but I always arrive with the yacht in one piece and a crew that is happy.

If I could have one additional instrument on board, it would be a crew satisfaction meter. If the crew is happy, then it's a great cruise. Since I don't have a satisfaction meter, I rely on my wife to tell me how I'm doing.
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Old 14-09-2010, 17:00   #28
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Shiva still has her original B&G Hornet instruments which includes a speed log transducer and displays speed in two decimal places. Getting it calibrated is a major problem and it is sensitive to fouling and this slows it down and recalibration introduces error of course.

Having said that, it is an awesome and necessary bit of data for sail trim and even "towing the dinghy trim" and as you adjust the above you can see not only a trend in the speed through the water but very small increments of change and considering how slow a sailboat moves .1 of even .05 of a know is nothing to ignore.

Sure tell tales tell the sail trim story, but they are clearly not as accurate (subtle) as the electronic data.

And this also is used to compute true wind speed and angle which is handy to know re reefing and so forth.

The speed through the water next to the SOG indicates the current, leeway and so forth. When they read the same there is no current.

No you don't need the data, but it's useful and it's "fun" and it can help you with sail trim, but I wouldn't have a boat without a speed log.
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Old 14-09-2010, 17:22   #29
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i have heard many mention how it helps with sail trim and such. If you are watching SOG on the GPS instead of the output from the paddlewheel wouldn't you get the same exact change since the current would be constant. A trim change that increased boat speed .5 knot would still be good wouldn't it?
I can see that maybe if you changed directions that you could not expect the numbers to be equal but you should be able to expect any change you make in one direction to be seen in both the speed through water and over ground.
Our boatyard owner (a naval architect) tried to talk us out of adding the speed meter since it would need another trough hull. We balked and wanted it because we have always used it. The other day it was not working well and I just changed the input in the same place on our display to the SOG instead of the boat speed and no one never even noticed. We did everything we usually did with the speed and it seemed to be just as accurate and sensitive to sail changes.
As far as redundancy is concerned being without GPS would be a bigger problem for many sailors today. You could always have a knot log to drag for that rare occasion that the GPS is down to handle the DR.

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Old 14-09-2010, 18:10   #30
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I would not discount all those that suggested that a knotmeter is essential equipment, but the overground (over the bottom) display of speed on a GPS will display relative changes in speed through the water when the direction of the vessel and the set & drift of the current remain constant. This is also assuming that the GPS is obtaining suitable triangulated signals from sufficient satellites to keep an accurate fix. I most frequently cruise without my "paddlewheel" knotmeter in place.

Take care and joy, Aythya crew
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