To log or not to log that is the question

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Camelia arrived with a trailing log in the summer and on inspection is "fubar".

So the question is, should I add a paddle wheel one thought the hull while she is on the hard or rely on these new fangled GPS system (she came with three seperate ones onboard)?

My head says get one, my heart says don't cut another hole in the hull.
 
It depends on the kind of sailing you do. Other than for racing, it is not necessary to know your speed accurately but it is essential to have some means of measuring your distance through the water. A GPS, or even three, is no substitute for a log of some kind. A trailing log can be fine and is easier to clear if it is fouled by weed. If your sailing ambitions for the season are modest, I would try the one you have and see how you get on.

We cruised for nearly 20 yrs with no means of measuring our speed other than a Dutchman's log and were quite happy. At that time we used a Walker log for distance. One disadvantage of a towed log is that you must of course remember to hand it when manouevring; a friend of ours reversed over his with embarrassing results.

If you don't get on with yours, a through-hull log can work fine. A properly installed one shouldn't risk sinking the boat. All through-hull logs sometimes foul, so it is much better to get one which can be cleared easily, preferably with a valve to stop water ingress when the log is withdrawn. This isn't absolutely essential and I got quite nifty at clearing our previous one while on the move. They do differ, however, in how readily they foul. My Raymarine log seldom fouls as there are flanges either side of the paddle, whereas the old Navico job was hopeless, with an exposed paddle.
 
I am inclined to disagree with johnalison to some extent

A log is next to essential if you want to know fairly accurately you speed through the water ... for optimising sail trim for example

However or navigational purposes the distance traveled over the ground is the most useful thing to know. With a log you have to calculate it, or determine it by plotting, from the log reading and a knowledge of the tidal streams.
A GPS can give you the distance, and speed and direction, made good over the ground straight off, no messing.

Not only does the GPS give you the information you need for navigation but it gives you a precise position anyway.
 
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Present boat had from new - now been on the water for nearly 10 years and we still haven't fitted the through hull log. We do short distance coastal sailing, seldom more than 5/6 hours/25km in a day, so it is mostly pilotage and SOG from one of the 2 GPS units & from the chartplotter is absolutely fine.

In fact I leave the oldest GPS set to SOG all the time and use the other two for navigation.
 
VicS said:
Not only does the GPS give you the information you need for navigation but it gives you a precise position anyway.
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No doubt it does, providing it works. I haven't used a logged distance in anger for a good few years but I'm not sufficiently optimistic to believe that it could never be necessary. As I said above, if you need to know the speed, you can have it, but if you want to navigate safely, you may at some time need a way of recording distance run without relying on GPS. A decent mechanical log plus tide tables and knowledge of the tidal streams will be more accurate than guesswork.
 
johnalison said:
No doubt it does, providing it works. I haven't used a logged distance in anger for a good few years but I'm not sufficiently optimistic to believe that it could never be necessary. As I said above, if you need to know the speed, you can have it, but if you want to navigate safely, you may at some time need a way of recording distance run without relying on GPS. A decent mechanical log plus tide tables and knowledge of the tidal streams will be more accurate than guesswork.
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That is no doubt the reason the boat has come with three GPS receivers.
Although I suspect not many carry back-up for an electronic log.
 
My impellor log never worked for very long. usualy grew brnicals and mussels.
Less holes in boat the better.
If i were to consider fiting a log for through the water speed. I would try and find a doppler log or pitot tube. probabaly not easy to find now.
or easy just find a walker.
 
Camelia said:
Camelia arrived with a trailing log in the summer and on inspection is "fubar".

So the question is, should I add a paddle wheel one thought the hull while she is on the hard or rely on these new fangled GPS system (she came with three seperate ones onboard)?

My head says get one, my heart says don't cut another hole in the hull.
Click to expand...

A log is not required for navigation. If you lost access to GPS and needed to navigate not knowing distance traveled just means that your EP circle of error is much larger. This in turns means you have to be more cautious and make decisions based on the uncertainty.

So if your primary means of navigation is GPS and you have redundancy covered in GPS, then I wouldn't bother. The hole in the hull is a red herring as this is all about navigation and the level of back up uncertainty that you are happy to live with. If you fit one you fit it properly so the skin fitting represents an extremely low probability of failure.
 
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BlowingOldBoots said:
A log is not required for navigation. If you lost access to GPS and needed to navigate not knowing distance traveled just means that your EP circle of error is much larger. This in turns means you have to be more cautious and make decisions based on the uncertainty.
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+1 you take your chances, like everything on boats.

Could you get home without it and GPS a compass and a guesstimate of your speed?

So a balance hole in hull vers more security of navigation. If I wanted security of navigation it would be a trailing log for me.

Present boat came with through hull which is good for sail trim etc speed increased decreased but I would question its accuracy..
 
If the GPS satellites get switched off or weather is too poor for them to work, it will not matter how many receivers one has...

Though our VDO log is nice to have, I suspect it misreads anyway. If I had to rely on it I think a dutchman would be preferable. I previously had a trailing log and the spinner got eaten or otherwise disappeared about every 100nm.
 
I bought a Wasp log this year , from Ebay.
Bugger to stream but once set it's fine.

Like others my paddlewheel log is a complete waste of time , even if the wheel is removed and very carefully antifouled it only lasts until perhaps June before fouling up.

I think I got the Wasp becuse evry other boat always seems to overtake me and I wanted to see my speed through the water and wanted to check my sail trim.

Of course I knew in my little black heart the reason why is due to my short waterline length.

When I checked it out the boat was going as fast as you would expect others of the same lwl to go.

It also stops you overestimating your speed through the water when again in your little black heart you know there's some tide going with you.
 
The chances of GPS falling over in some catastrophic way are so remote as to be unworthy of serious consideration. Provided you have some redundancy in terms of GPS receivers then I don't see much point in having a mechanical log of any sort. That said, I do have a paddle wheel log which came with the boat. It's fine when it works but it doesn't for about 50% of the time due to fouling.
 
Thanks all, I'll give all your posting some thought.

Most of my sailing is in the South West with trips over to the Channel Islands and North France.
 
SAPurdie

"or weather is too poor for them to work,"

What sort of weather conditions stop them (GPS)?.

I am sure that many woud like to know
 
As said earlier it's about your acceptable level of uncertainty. Most forms of traditional navigation have an error level. Navigating is about recognising this and working with it. So your log may not be calibrated correctly, the paddle wheel may be gunged, the compass may have a metal bar near it, the tide may not be as predicted, your lines in three point fix in a chop may not cross at the same point, your time check may be out by a second or two when you read the sextant.

GPS is fantastically accurate. YOu can add plotter and AIS to it (on a smart phone these days although I prefer to use laptop) for those times when your acceptable level of uncertainty is exceeded. That's to do with your risk appetite and trust in software.

I set off around the Atlantic with a Nasa duet which was occasionally in agreement with me (the depth of the Atlantic is apparently sometimes 1.5m!) and a Garmin 72. By the end of the year I only used the log to record the log and for sun-run-sun sighting. The latter was really only for personal development and back up if the electrics failed.

I hope that helps. It's more about the way you approach sailing than the equipment.

Matt
 
I really cannot understand anyone contemplating boring a hole in the hull to fit a log paddle-wheel sensor. When I had one it always fouled in a short time and needed constant removal and cleaning - water got in even with sealing flaps. The whole procedure was a pain and is so primitive that I would sooner go back to my Walker Excelsior Mk IV trailing log than re-install it, except that is somewhere in the cellar and not even on the boat, just like my sextant and tables.

The original skin fitting is now blanked off and my Garmin plotter provides a very precise SOG in one of the data windows - far more accurate (to two decimal places) than the original VDO log ever was and it gives trip and total distances too. True that there is no through-the-water speed but I do not need that, SOG is the important thing and just as useful for sail trimming.

I have two other GPS back-ups, including a netbook running OpenCPN with the dashboard readout. I have never known anything ever interfering with full GPS reception and think it infinitely unlikely - too much of the world's navigation/surveying services rely on it.
 
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Barnac1e said:
I really cannot understand anyone contemplating boring a hole in the hull to fit a log paddle-wheel sensor.
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Actually, I can think of a reason.

Many, many years ago when I was sailing my Wayfarer at Whitby and before I bought my first cruising yacht I crewed for a friend with a cruising Folkboat for a race from Scarborough, a drying harbour, arriving the evening before and sleeping on board for the morning start. It was difficult to sleep against the harbour wall when the keel began to settle on the bottom on the falling tide as the waves from a strong southerly were entering the harbour and lifting and dropping the boat - bang, bang, the mast and rigging shaking and rattling from the impact.

Driven to distraction, my friend leapt from his bunk, pulled up the cabin sole, unscrewed the log transducer and pulled it out. When the level of water had risen enough and the boat had settled firmly on the bottom he replaced it with the remark to remember there was water in the boat if we got up in the night. We had a quiet night and pumped out in the morning.
 
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