cloud-nine
New Member
I just found this on youtube and thought it might be of interest to those suffering constant paddle wheel fouling.
An impressive video of the nasamarine electromagnetic log.
- Thread starter cloud-nine
- Start date
Andrew_Trayfoot
Well-Known Member
I've been thinking about one of these for a while. I even have blanked off hole in the boat that would fit it. That had a NASA paddle wheel in in that never worked for more that a week or two and finally got dumped when a friend's boat nearly sank off Stokes Bay when it came apart in his hands!....
My issue is the display head: They look so cheap.
If I could find another NMEA display head for a reasonable price I'd go for it.
My issue is the display head: They look so cheap.
If I could find another NMEA display head for a reasonable price I'd go for it.
pvb
Well-Known Member
They do; crude graphics, way inferior to what the rest of the industry is doing.
Andrew_Trayfoot
Well-Known Member
I know NASA know their market, so far be it for me to criticise but....
I would have thought that there would be a gap in the market between what they offer and the rest of the industry...
Andrew_Trayfoot
Well-Known Member
I found this the other day: KMR-6 - Multifunctional Display with NMEA Multiplexer -5 inputs / 2 outputs
But very little availability and still too expensive..
But very little availability and still too expensive..
Hoolie
Well-Known Member
I have one to be fitted when we next have the boat out of the water. The NMEA will connect to the rest of the boat system via a multiplexer and the data will be available to the computer, the autopilot and the Raymarine cockpit instruments. No Nasa display!
William_H
Well-Known Member
What is the mode of operating? ie does it use ultrasonics to get a doppler measurement of water flow or does the name suggest some other science? ol'will
mattnj
Well-Known Member
NASA sell a pulsed output version to use with any other display head...
dankilb
Well-Known Member
I’ve got mine!
Yet to install it though and NASA never replied to an email asking whether 200mm is too close to the keel (big iron lump - 41’ AWB)! ?
I wonder how ‘electromagnetic’ a keel is? I shouldn’t imagine very much unless they’re practically touching.
Yet to install it though and NASA never replied to an email asking whether 200mm is too close to the keel (big iron lump - 41’ AWB)! ?
I wonder how ‘electromagnetic’ a keel is? I shouldn’t imagine very much unless they’re practically touching.
Hoolie
Well-Known Member
The clue is in the name! Not ultrasonic but works by generating an alternating electromagnetic field between electrodes. Unlikely to be affected by a metal keel.
NASA sell the unit with or without their Clipper display. Calibration is set on the small interface box attached locally to the sensor rather than on the display head.
vas
Well-Known Member
nice find, hadn't spotted it!
wheel works 1wk 2wk max here.
problem is that it's an AIRMAR DST800 triducer so speed temp and depth.
Temp failed (now showing 60C instead of 26C), log effectively useless, so I now only have depth (which is the most important in the Med where we have no serious tides)
Problem is that if I want to replace it with this, I need to drill another hole and fit a depth transducer in there. If they would do a speed/depth for 200quid I'd get it!
wheel works 1wk 2wk max here.
problem is that it's an AIRMAR DST800 triducer so speed temp and depth.
Temp failed (now showing 60C instead of 26C), log effectively useless, so I now only have depth (which is the most important in the Med where we have no serious tides)
Problem is that if I want to replace it with this, I need to drill another hole and fit a depth transducer in there. If they would do a speed/depth for 200quid I'd get it!
tillergirl
Well-Known Member
Onwa KMR-6 Multi-Screen Alan is the UK dealer, one available a little bit cheaper.
I have a NASA. It consistently shows half the speed. I need to pull the 'ducer and see if it is fouled. Don't really fancy an armfull of water. But there it is.
Rum Run
Well-Known Member
I have the half speed thing on a NASA log - it is caused by one of the two tiny magnets disappearing from the paddle wheel. Replacement part costs under a tenner! And refrain from pressure washing the paddle wheel next time........
Hoolie
Well-Known Member
An electromagnetic log doesn't have a paddle wheel! That's the point of them really ... ...
dukeofted
Well-Known Member
You could just epoxy the transducer to the inside of the hull if you are solid GRP. I did that to save another hole in the boat and it works perfectly.
AntarcticPilot
Well-Known Member
pvb
Well-Known Member
Have you tried antifouling the impeller and housing?
William_H
Well-Known Member
Thanks Hoolie but do you have any more specific detail on how this magnetic field works and is affected by water flow? ol'will
cpedw
Well-Known Member
I think it uses magnetohydrodynamics.
AntarcticPilot
Well-Known Member
That's the way NASA describe it. I don't think it's a Doppler log. Physically, the transducer has three tiny bumps on it, and is mounted flush with the hull.