Traditional Log / GPS

[joe17]

I am considering buying a new boat. One of the candidates doesnt have a through hull log. The owner has been using GPS as a his log.

Is there any good reason why a boat should have a traditional log?

Things which came to my mind were :
. Less complicated system than GPS (and free of political interference!) therefore perhaps more reliable?
. Knowing the difference between the speed through water against speed over the ground.

I am sailing in the Baltic, in the gulf of Finland, so its not an area which is subject to strong tidal streams etc.. Therefore I had concluded this is not a showstopper. Any other opinions?



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[willothewisp]

My log never seems to work for more than two weeks consecutively- if at all - and sometimes comes up with the most outrageous readings. It's only three yers old, mind, so last summer I thought I wouldn't bother and forgot all about it. Have used GPS instead, much more reliable. Having both of course gives you speed added/reduced by tidal streams, but you can work those out anyway. (not so in the Baltic I believe)

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[Benbow]

I find it very valuable to be able to see the actual tidal stream by comparing log vs GPS. I don't know how you could work this out any other way. Tidal stream atlases don't show sufficient detail close inshore, and locating an eddy or detecting an unexpected foul stream can make a huge difference to your progress. However, that is the only real objection I can come-up with. In an area such as the Baltic with no significant tides, I would have no worries about not having a log. Although purists will no doubt worry that you can't calculate an EP if your GPS fails.

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[AndrewB]

Agree.

The only thing I'd add is that should the GPS fail, it is always possible to estimate distance sailed from speed, and so an EP can still be established. A <A target="_blank" HREF=http://www.tallshipbounty.org/chip.html>chip log</A> is traditional and easily made up, but even simpler is to measure the time it takes the yacht to sail past a matchstick thrown from the bows. (The speed in knots is approximately twice the length of the boat in metres divided by the time in seconds).

 

[peterb]

Re: Agree.

Chip logs (or Dutchmen's logs) are the traditional way of doing it, but they're difficult if you're short handed. Racing back from the bow to time the chip going past the stern is difficult. I use 20 m of floating line, tied to the stern at one end and with a small float with a mast at the other. Let the line form a loop behind the boat, then drop the float into the water. As the line comes tight the float's mast jerks. Time from drop to jerk, speed is 40 divided by time in seconds.

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[Evadne]

My boat didn't have a through-hull paddlewheel when I bought her so I got a trailing log. The Stowe is no longer made but there are some alternatives still available, as well as the traditional mechanical ones. You don't have to drill another hole through the hull, they don't have to be deployed if you prefer to use gps "log", and if they do get fouled then you pull in the impeller and remove the weed. The main thing is to remember to pull it in when you get to a harbour entrance, or before using reverse gear. They are also unsuitable for planing motorboats.
Personally I'd never rely on gps for a log, but then I only use our handheld gps as a secondary aid anyway.

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[Leisure27]

Re: Agree.

That's a very good idea. Last year I bought this product: www.knotstick.com, good and cheap (especially now with the dollar rate) but the reading gets cocked up if you pick up the smallest bit of weed, you have to keep pulling it out and cleaning the disc. You can't really leave it in all the time but it is good for a period when say trimming the sails. If you get one, get a spare bungy as they easily get lost over the side.

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[LadyInBed]

If you really want a log and don’t want to cut a hole, the other options are a trailing log or if you have a transom stern, hang an impeller over the back on a pole.
In you are coast hopping in non-tidal waters, you could probably live without one.


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