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Old 14-09-2017, 17:05   #1
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Do you need a dedicated speed instrument

As speed and distance can be seen and measured via a gps instrument is there a need for a dedicated speed log instrument. It would not only save extra expense it saves time on routine cleaning of the hull fitting.
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Old 14-09-2017, 17:13   #2
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Re: Do you need a dedicated speed instrument

Only in that it saves you turning on the Navionics
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Old 14-09-2017, 17:15   #3
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Re: Do you need a dedicated speed instrument

This is often discussed here on CF. Bottom line is that a log tells you speed through the water, something useful in sail trim, etc, as well as in evaluating currents. This data is not available from the GPS.

Some folks don't find this a problem, others (like me) do. There is no absolute answer to your question.

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Old 14-09-2017, 18:04   #4
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Re: Do you need a dedicated speed instrument

Quote:
Originally Posted by Jim Cate View Post
This is often discussed here on CF. Bottom line is that a log tells you speed through the water, something useful in sail trim, etc, as well as in evaluating currents. This data is not available from the GPS.

Some folks don't find this a problem, others (like me) do. There is no absolute answer to your question.

Jim
Agreed. Both speed over ground (GPS) and speed through water (log) are fundamental units of sailing, just like wind speed. That said...

If you are just day sailing for relaxation or even island hoping in the Bahamas, then you could be fine with GPS only. Many learn to sail on board without any speed info at all.
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Old 14-09-2017, 18:27   #5
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Re: Do you need a dedicated speed instrument

Quote:
Originally Posted by Jim Cate View Post
This is often discussed here on CF. Bottom line is that a log tells you speed through the water, something useful in sail trim, etc, as well as in evaluating currents. This data is not available from the GPS.

Some folks don't find this a problem, others (like me) do. There is no absolute answer to your question.

Jim
Also agreed

Plus I like the redundancy of having both.
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Old 14-09-2017, 18:52   #6
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Re: Do you need a dedicated speed instrument

Many of us have sailed with no speed instrument or GPS. So, no, it's not "necessary."
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Old 14-09-2017, 19:08   #7
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Re: Do you need a dedicated speed instrument

Also, if you have wind instruments, true wind speed is calculated based on speed through the water as an input, so without the paddlewheel that information is going to be less accurate.

If you sail in areas with significant currents, speed through the water information can be extremely useful. As to whether you "need" it or not, that's a function of what information is important to you.
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Old 15-09-2017, 05:28   #8
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Re: Do you need a dedicated speed instrument

On my boat I do not have a way to measure speed through the water, only speed over ground (GPS). No problem for me. When I'm on my boat, I don't care about speed. I'll get there when I get there.
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Old 15-09-2017, 07:21   #9
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Re: Do you need a dedicated speed instrument

change of speed thru the water, tells much about sail trimming and is big help if racing.
I personally never race, unless of course ,there is another boat.

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Old 15-09-2017, 08:21   #10
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Re: Do you need a dedicated speed instrument

This was already discussed extensively here: http://www.cruisersforum.com/forums/...te-186723.html

A few other threads too, which you can find using Google site search: https://www.google.com/search?q=site....com+speed+log
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Old 15-09-2017, 08:32   #11
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Re: Do you need a dedicated speed instrument

I would not install one on a 'new to me' boat.
-They often stop working from debris,
-a hole in the boat that is often just a plastic fitting,
-I never look at it anyway. What I want to know is how fast am I moving toward my destination.
-In a pinch a piece of wood on a string can tell you your speed.
-Here in the PNW where tidal currents run fast at times, it's useless.
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Old 15-09-2017, 08:34   #12
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Re: Do you need a dedicated speed instrument

I haven't cleaned my log in years and it doesn't work. Far as speed goes if I adjust the sails and my GPS speed across land goes up that's good enough for me!
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Old 15-09-2017, 08:47   #13
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Re: Do you need a dedicated speed instrument

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-Here in the PNW where tidal currents run fast at times, it's useless.
I'd say the strong currents make one MORE useful. Improves the reading for true wind speed, helps work out current direction/speed and helps with sail trim tweaking
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Old 15-09-2017, 08:54   #14
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Re: Do you need a dedicated speed instrument

I assume you have had some sailing classes some day...

If your electronics fail, you still will have a compass, a log (speedometer) and a wind vane. With paper charts you can estimate your location using calculations of youur last position, the course sailed and the speed.

So it is important for redundancy and is good seamanship. You can of course use a long line with some knots on it, throw it on the bow into the water and measure the time while it passes along your boat - so you can calculate the speed from m/s or ft/s in kn.
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Old 15-09-2017, 09:01   #15
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Re: Do you need a dedicated speed instrument

Mine is part of a speed/depth/temp transducer. When the boat is sitting for more than a day or two I pull it out and put in a plug which keeps it mostly clean. Every once in a while a bit of seaweed will jam it but that is rare.

It's certainly a piece of gear you can get by without, and I got by for several years with my old one broken. But it is useful, for sure.
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