NASA Clipper Duet Depth Log spurious readings

[yodave]

Hello,

I've been struggling with spurious readings through my Clipper Duet. The speed is fine and works well, but the depth log has been problematic for the last couple of years. Every now and then it works, as it did a fortnight ago, but 95% of the time it gives false information. Which is useless.

The boat is a 32ft twin-keel ketch. We're on a muddy drying mooring ...but the problem happens when we're out on the water (40/50m) too whether we're sailing or motoring.

I have re-installed and replaced the transducer with a new unit. I have sent the Duet display unit back to NASA for testing/refurbishment. I have disconnected the unit from the boat electrics and connected it to a standalone 12v battery that I purchased specifically for the purpose ...but that didn't fix it either. A bubble isn't the problem as the transducer is through the hull using the NASA factory fitting, and is not anti-fouled.

The next step is to remove the whole system and extract some pleasure in throwing it away with gusto ...however I'd rather avoid that as the transducer is through the hull, and this will leave me with a bit of a headache as any replacement system most probably won't fit the same holes. Despite having spent money trying to fix it, the expense of replacement is much less of an issue now than it was when the problem first arose, as it's become a real pain.

So I'm thinking one last attempt at identifying what the problem could be now that I'm pretty sure that it's not electrical interference.

Any thoughts or opinions are welcome.

Thanks in advance.

 

[steve123]

I had a problem with my NASA depth intermittently not showing more than 2m, even when in much deeper water. Tracked it down to my flexible solar panel - the problem occurred when the panel was positioned near to the wire between the transducer and the display.

 

[[70521]]

With 40 or 50 meters under the hull depth is not an issue, but I know what you are saying.

Have you considered changing the frequency of the pings this might sort out the problem.

I know crossing over the 100 m contour is aways a thrill but I tend to discount the depth after 10 meters.

 

[yodave]

I had a problem with my NASA depth intermittently not showing more than 2m, even when in much deeper water. Tracked it down to my flexible solar panel - the problem occurred when the panel was positioned near to the wire between the transducer and the display.

Hello steve123, and thanks for your reply. I guess isolating the power source doesn't rule out ambient interference along the lines that you have described. I can't think of any item that would be causing this kind on interference nearby, however I'll source some ferrite rings and see if that makes any difference.

Thanks again for your input.

Best wishes!

 

[yodave]

With 40 or 50 meters under the hull depth is not an issue, but I know what you are saying.

Have you considered changing the frequency of the pings this might sort out the problem.

I know crossing over the 100 m contour is aways a thrill but I tend to discount the depth after 10 meters.

Thanks for your thoughts Camelia. I mentioned the deeper depths so that forum members could discount any thought of there not being enough water under our keels.

I hadn't considered changing the frequency of the pings. Not being very technical, is the concept to take the frequency away from any possible similar frequency which could be causing some sort of conflict?

I'll do some digging around in this area to try to understand this better.

Many thanks!

 

[[70521]]

Thanks for your thoughts Camelia. I mentioned the deeper depths so that forum members could discount any thought of there not being enough water under our keels.

I hadn't considered changing the frequency of the pings. Not being very technical, is the concept to take the frequency away from any possible similar frequency which could be causing some sort of conflict?

I'll do some digging around in this area to try to understand this better.

Not quite

See Page 14 of your manual "Change the display update rate", or give the really helpful people at NASA a ring.

 

[Aardee]

Where is the transducer positioned? - A friend had issues with his depth log as the transducer was positioned between the keels, which I gather was prone to false reporting due to the pings bouncing between keels.

 

[yodave]

Not quite

See Page 14 of your manual "Change the display update rate", or give the really helpful people at NASA a ring.

Hi Camelia,

Thanks for your response. As it happens I called NASA earlier this morning and explained that last weekend I headed out into deep water with a standalone battery connected directly to the Clipper Duet only. NASA were very helpful and they pointed out that during my diagnostic test I kept the engine running, and suggested that I repeat the test without the engine being on. My plan is to do this over the weekend.

As for Page 14 / "change the display update rate" ...I don't seem to have that page and nor does NASA > http://www.nasamarine.com/pdfs/Clipper Duet.pdf

You don't happen to have that document as a PDF by any chance?

Thanks again.

 

[yodave]

Where is the transducer positioned? - A friend had issues with his depth log as the transducer was positioned between the keels, which I gather was prone to false reporting due to the pings bouncing between keels.

Hello mystique,

Thanks for your input. That is interesting. The transducer is between the keels, so that could be a possibility. I'll add that to my list of potential culprits.

Thanks again for taking the time to contribute.

Best wishes!

 

[yodave]

Well, I did the test over the weekend and took another small step forward. I spent a couple of hours ...going through the manual, I made sure all the settings were correct and I connected a standalone battery to the display unit. The main battery bank was disconnected from everything, and everything else was off. I fitted ferrites. Then I observed the results.

The reading stubbornly remained displaying 'out'. I spoke again to NASA today and they suggested I source another transducer and run some tests. They want me to listen to the transducer and confirm I can hear clicks. Point it to the sky and the display should read 'out'. Rub my palm across the transducer and there should be random numbers on the display. If my results are not as expected then I've to return the display unit.

I'll update this thread when I have more information that might be of use to others.

 

[yodave]

Thanks again to the forumites who responded to me. This is an update for anyone who experiences this kind of problem in the future.

I carried out the tests as instructed by NASA and reached the point where I thought it best to return the display to them (again). I had previously sent the display to NASA in 2012, and it only ever worked intermittently/infrequently since I got it back. In my opinion, NASA customer support is very good, and they explained that they found three faults with the unit which they subsequently fixed. I re-fitted the unit at the weekend and it's now operational again.

While I'm delighted that the problem has been resolved at last, that's tempered with the dawning reality that I have been trying to track down an interference problem for two years that simply didn't exist. I had become convinced that interference was the problem, as I had already returned the unit to NASA for repair (2012), and replaced all of the other components. In their defence, NASA have made me aware that my display unit is now quite old (it came with our yacht).

I suppose I'll just have to chalk this one down to experience. For the record, despite the two-year wild goose chase, I still feel that NASA customer support is amongst the best I've come across; they're helpful, communicative, and they treat their customers as people not numbers.

 

[VicMallows]

and they explained that they found three faults with the unit which they subsequently fixed.

Good marks to NASA for customer service ....but it would be nice to know exactly what those 'faults' were. (To be honest, I can't imagine that any company would bother to go that far. They would either replace the PCB or simply send you a complete new unit).

 

[yodave]

VicMallows: best I can tell the electronic joins/joints were dry and three were brown. That means nothing to me, but NASA said it was because they were old. The kit is well past any warranty; as I mentioned it came with our yacht.

Hope this additional info makes sense.

Thanks for your comment!

 

[gchead]

Have read your thread with interest. I have a new Clipper Duet.

The depth readout works fairly well but only up to about 14 meters. What depth does your Duet measure up to? (My transducer is glued to inside of fibreglass hull - 29' yacht).

Also the speed log always reads about 1-2 kts slower than actual SOG as measured by GPS. Anybody have any suggestions?

 

[Kwik Decision]

Have read your thread with interest. I have a new Clipper Duet.

The depth readout works fairly well but only up to about 14 meters. What depth does your Duet measure up to? (My transducer is glued to inside of fibreglass hull - 29' yacht).

Also the speed log always reads about 1-2 kts slower than actual SOG as measured by GPS. Anybody have any suggestions?

I have separate NASA depth and log, but I would imagine the technical details are the same as for the duet.

My depth transducer is located inside the hull in a NASA supplied oil filled tube. It generally reads depths to around 100 m without problems, but can give false readings quite often. Deeper than ~100 m it generally reads OUT.

Regarding the log. Firstly clean the paddle wheel - these tend to get fouled quickly, and inspect it to make sure one of the little magnets hasn't fallen out (this does happen occasionally, but NASA sell spares). Then calibrate it, following the instructions (which are easy to find on the NASA web site, if you can't lay your hands on your copy). Also note that when calibrating against a gps, you either need to be somewhere where you are sure there is no current, or you will need to do multiple runs with and against the current to get the calibration correct.

 

[gchead]

I have been cleaning the paddlewheel regularly but I'll also check none of the little magnets have fallen out. I didn't know you could calibrate the log. Have checked the manual and I'll do this next time I'm out.
Yes, the oil filled tube may be the solution to my depth problem. Mine shows OUT at any depth over about 14 mts. I'll check with the local Nasa distributor here in NZ and se if they stock them.
Many thanks for your timely advice!

 

[yodave]

In the end I replaced the whole system with a new Duet and that resolved my problems.

My set-up shows OUT over 100 metres, and gets twitchy (unreliable) at around 1-2 metres.

As for the difference between your speed log and GPS that's the same as me ...however my view is that variation is down to the tide, so your speed through the water is unlikely to be the same as your speed over the ground unless there's no tidal movement. Of course, you may well be describing something completely different.

 

[ex-Gladys]

I had old NASA kit on Gladys when I got her, and in less than 2m, it was very unreliable, generally showing 4x the real depth. This could be resolved by manually adjusting the sensitivity, but then you had to readjust in deeper water. I was glad to get the Tacktick stuff that replaced it, completely self compensating and "fire and forget"

 

[ghostlymoron]

I had the opposite problem with mine. The depth was fine - it also became unreliable at less than 2m over a sandy bottom. Mine was mounted in an oil filled tube offset to one side and (I think) between the bilge keels. The only thing I can think of is the mounting position. Can you try moving it using a temporary fixing and see if you can get a better reading?
The log part of mine worked fine most of the time but jammed up frequently. I tried cleaning it including the spindle but that was generally unsuccessful and replacement was necessary. Eventually, I replaced it annually which did the trick. Fortunately, they are cheap to replace. I think the problem was caused by my drying mooring on soft sand damaging the spindle.

 

[rocky-]

Dear all,

I recently bought a new Nasa Clipper Wind instrument, which I was installing last saturday. I already have a well working Nasa Clipper Duet. I tought that I easily connect the power cables of the wind instrument to the duet's. But when the wind power cables are connected to the duets power cables and to the boat as well, the duet starts to measure 1.4kts speed of the boat, while the boat is docked, and not moving.
If I disconnect the wind instrument, the speed goes back to 0 slowly.
If i reconnect it again, then the speed goes up again to 1.4 kts slowly.
This is very strange. Where shall I search for the error, do I need noise filters between the two instruments power cables?
Do you have information about such missbehaviour?


Regards,
Krisztian