Log impellers

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Chae_73

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Our boat has a Stowe log, which I assume is an original fixture so would be 1987 vintage. The impeller is a sphere with voids (segments). In the year that we have had the boat, it has mostly not worked due to being fouled up (was not working when we bought the boat, worked briefly after re-launch and then fouled up again).

Are newer designs any more resistant to becoming clogged? I read about electro-magnetic impellers but they seem to have their own issues.

Is the answer to be brave and remove the through-hill regularly for cleaning, whilst afloat?
 
Have you tried using the correct antifoul paint designed for impellors? I have the modern raymarine type & usually do not have to remove it in a season. When it does get stuck I usually find it is weed fron the mastic bedding ( only 3mm Th) to the through hull joint ( will not retain the antifoul paint) which attracts long strands of weed growth to catch the vanes. I remove these with a bent wire pushed through the hole & rotated to "cut" them off.
Surround the hole with disposable nappies to gather up the water & one can usually prevent too much water spreading into the bilges.
 
Chae_73 said:
...Is the answer to be brave and remove the through-hill regularly for cleaning, whilst afloat?
Click to expand...

You could do that, I've thrown the towel in with those things, put the blank in and forget it, haven't yet got round to permanently filling the hole in the hull. SOG from GPS will do for me...
 
Daydream believer said:
Have you tried using the correct antifoul paint designed for impellors? I have the modern raymarine type & usually do not have to remove it in a season. When it does get stuck I usually find it is weed fron the mastic bedding ( only 3mm Th) to the through hull joint ( will not retain the antifoul paint) which attracts long strands of weed growth to catch the vanes. I remove these with a bent wire pushed through the hole & rotated to "cut" them off.
Surround the hole with disposable nappies to gather up the water & one can usually prevent too much water spreading into the bilges.
Click to expand...
Can you post details of these A/F paints? Like the OP I had not heard of them either.
 
A speed log is not essential, though a means of recording distance is usually associated with a compass as being necessary. Knowing the speed can be very useful though and I would be loath to do without it. Whatever means you have of delaying fouling, there is really no substitute for being able to retract the impeller for cleaning. We lived with a terrible Navico log for many years on our old boat and I got accustomed to withdrawing it when under way. There have been several discussions about it here but I found that using a sponge was all that was necessary to prevent excess ingress. Now that I have a log with a valve I worry about it even less.

When we were on the move most of the season my Raymarine impeller rarely fouled, and only occasionally picked up weed, unlike the Navico (‘80s vintage). With little sailing this year it has tended to foul and harbour creepy-crawlies but is easily cleaned. I normally smear the impeller with silicon grease to delay fouling.
 
V1701 said:
You could do that, I've thrown the towel in with those things, put the blank in and forget it, haven't yet got round to permanently filling the hole in the hull. SOG from GPS will do for me...
Click to expand...
The thing about having the 2 readouts is that one can determine tidal effect much better. It also gives a more consistent speed reading & when coupled to other instruments can be used to give apparent/true wind info. One might not bother with that, but it is a bit like having gadgets on a car. One might not have them, but when one does they are nice to have & nice to use. They just add to the sailing experience.
Of course there are those that say that the experience of sailing does not need that info. Well yes , & often I do not even turn my GPS on. But when I do the quality of the equipment makes it more pleasurable.
 
johnalison said:
A speed log is not essential, though a means of recording distance is usually associated with a compass as being necessary. Knowing the speed can be very useful though and I would be loath to do without it. Whatever means you have of delaying fouling, there is really no substitute for being able to retract the impeller for cleaning. We lived with a terrible Navico log for many years on our old boat and I got accustomed to withdrawing it when under way. There have been several discussions about it here but I found that using a sponge was all that was necessary to prevent excess ingress. Now that I have a log with a valve I worry about it even less.

When we were on the move most of the season my Raymarine impeller rarely fouled, and only occasionally picked up weed, unlike the Navico (‘80s vintage). With little sailing this year it has tended to foul and harbour creepy-crawlies but is easily cleaned. I normally smear the impeller with silicon grease to delay fouling.
Click to expand...
I beg to differ. After 10 years of boat ownership I finally fitted a working speed log last summer. Seeing the SOG and STW was a total revelation! All of a sudden I knew exactly what the effect of the tide was on the boat at that exact place and time.

I had the log in situ for 35 days and covered 1250 nm with no fouling issues. It constantly told me that it was way too cold to go swimming and logged both temp and depth on the downloadable data file.

The new through hulls with flap have made pulling the log far less stress free.
 
I've never had any luck with paddle wheel logs. Had 3 over 28 years and none have gone more than 3 weeks without stopping.
Take it out, clean, use. Next day it's stopped again.
Fitted a nasa eml. 6 weeks later it's still working. I like seeing the current speed whilst moored as it measures down to 0.1 knts.
I think it's worth the £165 and can easily be withdrawn if or when it needs a clean.
Can be a pulse or nmea version to work with your existing display
 
I dumped all my NASA kit because all the displays get serious condensation ( inspite of their claims that they do not) The wind vane wore out twice. The illumination is poor. The compass is c..p. The echo sounder gave up the ghost after 2 years. It is just cheap & nasty kit
 
V1701 said:
You could do that, I've thrown the towel in with those things, put the blank in and forget it, haven't yet got round to permanently filling the hole in the hull. SOG from GPS will do for me...
Click to expand...
Yep , gave up on thro hull , same , not filled yet , but have a trailing log if we feel the need.
 
If, per littlesister's post #3 you put the log in to go sailing and take it out when you get back, you don't really have to clean the log. Fouling builds up most when you leave the boat not moving for a while. So I put the log in before going anywhere, and take it out when we've finished sailing (at the end of the weekend / holiday). The airmar through-hulls in a tube are a little nerve wracking to deal with first time round but once you know you only get a bit of water in it's not a worry.
 
my paddle wheel log stops working around the beginning of August. Cleaning it gets a few days of inaccurate operation. I have an old Stowe trail log that takes over for the second half of the season!
 
Sandy said:
I beg to differ. After 10 years of boat ownership I finally fitted a working speed log last summer. Seeing the SOG and STW was a total revelation! All of a sudden I knew exactly what the effect of the tide was on the boat at that exact place and time.

I had the log in situ for 35 days and covered 1250 nm with no fouling issues. It constantly told me that it was way too cold to go swimming and logged both temp and depth on the downloadable data file.

The new through hulls with flap have made pulling the log far less stress free.
Click to expand...
I don’t think we disagree. You have survived ten years without a log and no disasters occurred, I presume. I try to avoid putting dissatisfaction into the hands of those without the means to acquire or fit items that many of us enjoy.
 
In order of usefulness electric instruments are as follows:

1 - Echosounder - have sailed many miles without one but do like to have it now especially with a deepish keel.
2 - GPS - there were times long ago when I'd have sold my soul to know where I was within a mile or two, let alone within yards.
2 - Speed log - inaccurate for long even after calibration but there are times it is useful, mostly to compare STW with SOG
3 - Wind speed/direction - why bother: you can feel the wind and know where it's coming from.

I'm not a total technophobe: I do dearly love modern plotters, though I hope I can still remember how to use leadline, sextant and compass.

If you do use a paddlewheel log pull it out and clean it regularly, especially if the boat has sat static for more than a day or two. You won't sink with a few pints of water coming in. You won't sink even if you waited 3 minutes with water coming in, let alone 3 seconds.
 
I'm lucky with my nasa log, it seems to work accurately and doesn't get fouled though I do remove it often.
It's been put in the right place presumably with little turbulence, and is mounted in a locker with bulkheads that go above the waterline (along with heads seacocks) so if any of these failed, it wouldn't sink the boat!
STW is very useful, even if your setup means it's not 100% accurate. Just for things like trying to work out what does and doesn't affect speed...
SOG is useful too but it's nice to have both to compare them and work out tidal effects, in the same way that comparing your Heading and COG can give you a lot of useful info.

It's probably not relevant to most yachts, but Radar should use STW rather than SOG as otherwise with tidal streams the aspects of the targets will be wrong. It won't affect the CPA calculation though.
The tug I'm on doesn't have a speed log, only SOG and it's frustrating at times.

As for these electromagnetic logs, are they the same principle as the Doppler logs commonly used on ships? - if so, in my experience in commercial use they are very good! You can also select Water Track or Bottom Track for SOG or STW depending on what you want, and have no moving parts to get stuck.
 
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