Chip Log?

[Little Rascal]

Has anyone every used or made a traditional chip log?

Unfortunately my old stowe log was borrowed and lost so I am without a proper log until I can replace it. Which will be after my next trip.

I have GPS for SOG but it would be nice to have a check on my boatspeed and to get an idea of how much tide is running. Worth messing about with do you think?

 

[prv]

All three square riggers I've sailed on have had them, though I've only seen one used once and that from a distance (fifty-odd feet above )

They had a big wooden reel of fairly light line, with the famous knots in. A length of broom-handle went through the middle of the reel and the word "TALLOW!" and an arrow were written on in big letters, pointing to the hole that the stick went through. Always lots of tallow around on that kind of ship so I guess it was a good choice for greasing the "bearings".

The actual log was a quarter-circle of plywood with some scraps of lead nailed around the curved edge. Two legs of line going to each end of that edge, passed through holes then knotted. Third leg went through a hole and jammed in place with a small bit of wood on a length of marline. Nothing clever, just the right amount of friction when jamming it in.

One person holding the reel in front of them, another standing at the rail counting the knots, a third with a watch timing them. When they grabbed and stopped the line, the peg fell out and the log fell over to be pulled back in.

I'm sure you can look up (or indeed work out) the proper distance between knots.

Only really done on those ships to show people how things used to be. I can't imagine it being worth the hassle on a yacht if you have GPS. Work out tide either from buoys etc as you pass them, or check the charted streams.

Pete

 

[rob2]

GPS gives accurate tidal data - just lie a-hull...

Rob.

 

[AntarcticPilot]

Another way is to throw a chip of wood (or other biodegradable convenient material, e.g. bread) from a known point at the bow and time it past the stern. Make sure the object is thrown sideways enough to miss the bow and quarter waves. Simple matter to compute speed through the water from the distance and the time, and more accurate than the traditional log-reel, which, as the instruction to use tallow indicates, suffers from problems with friction at the reel!

So, on my boat, I have a length of maybe 25' to time (you can't go from the bow; impossible to throw the object sideways enough). 1 knot = 1.687810 ft/sec, so speed in knots = 1.687810 * 25 / time.

Therefore, 10 seconds = about 4 knots.

 

[Little Rascal]

Hmm, I'd need quite an accurate clock for my boat it's only 19ft

The normal run is 28 seconds, I was thinking of a simpler version with a shorter line. P'raps short enough to coil and let it run by hand for less friction. And maybe a bit of bungee rather than the peg for recovery.

 

[2nd_apprentice]

Mmh taffrail log e.g. Walker Knotmaster would be easier but then again not exactly push button either

 

[Giblets]

A late sailing buddy of mine used to swear by his "tennis ball log"

IIRC he had a 50 ft length of line with a tennis ball tied on one end and a small loop on the other to go over the middle finger. He used to stream the line astern in a loop and drop the ball into the 'oggin whilst starting his stop-watch and time how long it took until the line went taut. The figures where as follows:

30 seconds = 1 knot

15 seconds = 2 knots

10 seconds = 3 knots

7.5 seconds = 4 knots

6 seconds = 5 knots

5 seconds = 6 knots

4.25 seconds = 7 knots

3.75 seconds = 8 knots

It appeared to be quite accurate particularly at slower speeds and was used successfully on several channel crossings in the days before GPS, plotters & Decca.

 

[Little Rascal]

A late sailing buddy of mine used to swear by his "tennis ball log"...

Sounds worth a go!

Re Taffrail logs: I would like a Stowe log to replace my old one (don't really fancy holes in the hull)....

 

[Little Rascal]

Well I have an old tennis ball and some 3mm line. Now: how do I attach the line to the ball? Two holes and a stopper knot (a la swingball)? Or would that sink it

 

[john_morris_uk]

GPS gives accurate tidal data - just lie a-hull...

Rob.

So in order to work out whether its time to tack (and perhaps save a few minutes on your passage by tacking as the tide turns etc) you stop the boat and watch the GPS to see what is happening to the tide?

Or as you approach a headland you aren't sure whether there's a tidal eddy where you are and can't decide whether to tack inshore or stay offshore....

Lots of reasons why you need an idea as to what the tide is doing as you sail along and don't want to stop. The tidal stream tables aren't accurate to the minute and are often vague about when a tide actually turns. They also aren't very good close inshore.

I know it doesn't matter to lots of people, but speed through the water vs SOG is a measure I keep an eye on nearly all the time...

Each to their own though.