Clipper Log

[bertiebasset]

Hi all,
Strange thing happened today, I recently purchased a 28 ft boat and found the log not working. After taking it out and replaceing the paddle wheel it still did not work. Today I went to the boat, replaced the whole unit less hull fitting, firstly trying it under a running tap to ensure the display (duet) was working correctly. On fitting it it seemed to be ok. Checked the old unit holding under tap and that works ok. Chased cable run thru and plugged it in and am sure it worked then stopped, pointed it aft and it worked then stopped. Now nothing. Only thing I can think is there is something holding the paddlewheel at the bottom of the hull fitting tho when I withdraw it I get a full flow of water into the bilges. Other option is could the cable be getting interference from other cables in the run, there is a clipper wind and new horizon chartplotter running alongside it ?
Would appreciate any help with this tho will be away for rest of week so unable to enter into discussion till Friday.

 

[Bodach na mara]

It is not clear from your post which unit is working and which is not, also whether it is working in the boat or just under the tap. Is the new unit a Clipper as well?

Some thoughts: The most likely fault is with the paddle wheel and spindle. These get worn which allows the wheel to run off-centre and it can jam on weed or barnacles that like to grow in the unit above the wheel where you can't see them. Another possibility is the loss of the magnet that is in the wheel, but from your description this is not likely.

A replacement wheel and spindle can be obtained from NASA by mail order. They are also available from www.allgadgets.co.uk

Pick-up and interference from other cables is not likely unless the cable is badly worn. Oh, that could also give intermittent failure if the sheath is not connected . I have that problem at the BNC plug on my sat-nav antenna.

 

[bertiebasset]

Thanks Wight and sorry for confusion. The boat had been on the hard in Portland for a year before I purchased her, but the previous owner had had her anti-fouled whilst she was out the water. Unfortunately I was not present when launched. On delivery passage to east coast the log never worked. I removed the unit and the paddle seemed free but was informed sometimes the magnets fall out of the wheel so replaced the paddle wheel. This made no difference so thought the whole unit had failed (the cabin floor has recesses for the top of both log and depth sensors) so sent off for new log. Thought I would just check the display worked before putting new log in so plugged in new log and ran it under tap to see 2knots 3knots etc on display. Fitted new unit and plugged it in and I seem to remember it working so chased cable through and before reconnecting I checked the old unit by same method of running under tap with same results. ie it works perfectly. On plugging in the new unit after routeing cable it seemd to work then stopped so I pointed it aft and I seem to remember it working then it stopped. Since then it seems to no longer work so I left it alone to sort out other problems thinking I will need to beach her and check the undersides to see if there is something stopping paddle wheel from spinning. Now have new paddle wheel and old log unit as spares lol

 

[Bodach na mara]

I admit, I am beat by that one. The symptom suggest a cable fault (broken screen or central wire) in that when you turn the sensor, the break makes temporary contact. With a new cable and sensor, that is not impossible, but not likely.

 

[Trundlebug]

Sounds like a classic case of worn spindle to me.

I had similar experiences, but the best thing to clarify is to loosen the large plastic nut holding the sensor assembly in place, and twist the sensor slightly whilst under way, to adjust the angle of attack of the paddle wheel. You can usually hear or feel when the paddle is rotating, and this should be confirmed by the helmsman.

If you get it working but then it won't get going again after stopping, the spindle is definitely worn and needs replacing.

I seem to remember it's a very low cost fix - a fiver or so.

 

[Poignard]

A couple of times this year my NASA Clipper log would not work after the boat had not been used for a couple of weeks. Rotating the transducer by 180 degrees got it working again but when put back to the original directon it stopped working again.

However, it has been ok on the last two (short) sailing trips

 

[Andyloc]

weed growth covering the bottom of the skin fitting could cause the paddlewheel not to turn properly whilst still alllowing water to flow in when the paddlewheel is withdrawn.

 

[VicMallows]

I haven't even bothered to fit the log transducer for my Duet (it's too short for my hull where the old NAVICO transducer was) .....should have just bought the Clipper Depth standalone. (also, remember all the stories of the NASA thru-hull-flange failing?)

I am quite happy with just the GPS speed-over-ground. After all, before GPS (or DECCA) we simply did the same calculation .... but the other way round.

Vic

 

[seadog30]

stiff paddle wheel ?

We had the same problem, I took the unit out,cleaned it, oiled it, tested it under a tap and all was well. Put it back in and it would not spin.

Repeaded the excercise 3 or 4 times, it worked out of the hull but not in.

The eureka moment came when I had the boat in the yard last winter !


With the log removed again I noticed a build up of gunge, limescale maybe antifoul paint for the last couple of mm at the hull end of the "hole".

Gently scraped this ring of gunge out and ran fine wet and dry arround the inside of the tube.

What was happening was while the log ran down the hole ok it pinched on the last couple of mm where the grunge reduced the hole diam.


All works fine now.

Good luck

 

[bertiebasset]

Thanks for all the replies, as I stated, it is a new log so wear cannot be the problem. I think seadog has it, the previous owner stated it works ok (dont they all) and that he had had her professionally antifouled (2 coats) whilst on the hard so probably some a/fouling has been overpainted and is hindering the paddlewheel from rotating. will get her on the sand in the wash in a couple of weeks and get under her to see.

 

[Tintin]

A couple of times this year my NASA Clipper log would not work after the boat had not been used for a couple of weeks. Rotating the transducer by 180 degrees got it working again but when put back to the original directon it stopped working again.

However, it has been ok on the last two (short) sailing trips

I've had similar experience. I have found that just rotating it 5 or 10 degrees makes it work again.

My guess is it is something to do with smooth water flow over the paddle wheel / air bubbles / hydrodynamics / voodoo.

 

[G12]

I haven't even bothered to fit the log transducer for my Duet (it's too short for my hull where the old NAVICO transducer was) .....should have just bought the Clipper Depth standalone. (also, remember all the stories of the NASA thru-hull-flange failing?)

I am quite happy with just the GPS speed-over-ground. After all, before GPS (or DECCA) we simply did the same calculation .... but the other way round.

Vic

It's just 75 ohm coax, you can add to it. (I got this info from NASA when I installed my duet)
Same with the depth, can be shortened or lengthened. (Again, this is from the horses mouth.)
I adjusted mine with satellite grade coax and normal 75 ohm tv coax connectors.

Oh, for the OP, Make sure the log transducer is pointing the right way.... NASA ones have a little arrow on them that unlike every other make of log I've ever seen, points AFT instead of forwards. The Log will read zero if it's pointing the wrong way.

 

[bertiebasset]

Make sure the log transducer is pointing the right way.... NASA ones have a little arrow on them that unlike every other make of log I've ever seen, points AFT instead of forwards. The Log will read zero if it's pointing the wrong way.

Thanks for that, according to my instruction manual which runs to a couple of pages, the arrow should point forward. I did turn it to point aft and it worked then stopped. When down there again will try it again pointing aft. and yes, i did try a slow rotate round to see if it worked off line and no it did not.

 

[Bodach na mara]

Oh, for the OP, Make sure the log transducer is pointing the right way.... NASA ones have a little arrow on them that unlike every other make of log I've ever seen, points AFT instead of forwards. The Log will read zero if it's pointing the wrong way.

Are you sure about that? The pick-up simply counts pulses as the magnet passes under it and mine works just as well pointing "back" as "forward".

The point in an earlier post about rotating the sensor about 45 degrees in each direction is a good one. At that angle there is a side load on the spindle combined with a flow across the blades which can free the rotor.

 

[VicMallows]

It's just 75 ohm coax, you can add to it. (I got this info from NASA when I installed my duet)

Oh dear! It was obviously too late at night and I didn't make myself clear. The NASA LOG TRANSDUCER THRU-HULL FITTING is too short to fit through my hull where the old NAVICO one is. (The old Navico thru-hull skin fitting is still in place with a blanking plug).

No issue with length of cable to log transducer....any sort of wire will do.

Vic

 

[G12]

Are you sure about that? The pick-up simply counts pulses as the magnet passes under it and mine works just as well pointing "back" as "forward".

The point in an earlier post about rotating the sensor about 45 degrees in each direction is a good one. At that angle there is a side load on the spindle combined with a flow across the blades which can free the rotor.

I am sure about that, I own one, it's brand new and doesn't work backwards..... I know this because I installed it the wrong way around the first time..... its in the manual which I of course read afterwards!
I also thought it was bloody peculiar!

 

[oldharry]

My Navman transducer has a profiled paddle wheel which gives a lower reading if installed 'backwards'. Never had a Clipper so dont know.