is there a non impeller speed-log?

[Sasha_V]

Hi folks.

A few years ago I thought I heard tell of a speed log that used a sonar beam and reciever to measure speed, thus no moving parts and nothing to clog.
Have done some searching and cannot seem to find anything out there nowadays. Any ideas or recollections ofsuch a beast?


And when I said non-impeller...I did not mean the old VDO sumlog with the propellor-on-a-fin-driving-a-cable-type configuration. Have one of those...it came with the boat and gained us half a knot of speed when we retired it.




Sasha

[capn_dave]

at one time, It was ultrasonic device that measured the speed of paticulate in the water.

I am not sure if it is still available, I have seen them on a couple of boats.

Fair Winds

Cap'n Dave

[Faster]

You're right - I recall reading about such a system a few years back - but can't remember who offered it. Haven't seen anything about it lately so maybe it never caught on.
The main drawback may have been the need to lead a wire down the keel to one of the transducers. (in one version that I remember)

I think it used the doppler effect or transit-time ultrasonic technique, a common industrial flow measurement method. As a flow measurement it is a bit unreliable and subject to errors that may be why it hasn't caught on here.

Makes sense, though, to eliminate the moving parts, doesn't it?

[kimberlite]

For the life of me i cant remember the name or find it on the web.
The company that makes it has many that retrofit to your current
through hull. i just can't find them again. my only issue was that it needs 12 volts at the transducer.
fair winds,
eric

[TrueBlue]

When all else fails, GPS will save the day.

[Sasha_V]

errr...no, it won't. GPS will give me (more or less) speed over ground, but that isn't always the info wanted.

Mind you, the GPS has also told me that I have sailed across the middle of a tall volcanic island in the pacific and that I was sailing at 78meters above sea level while parked at anchor....So it is not exactly perfect.

Sasha


Really want to track down this non- wheel transducer....Jeff H, any idea?


Sasha

[Sasha_V]

Bump...hopefully someone can help if this message crosses their path.

[FrancoisP]

French company NKE has one:
http://www.nke.fr/prod.php?idprod=3795994&rs=cv&lang=1

Francois

[Sasha_V]

THANK YOU!!!!!!!!!!!!!!!!!

It isn't the exact one I recall seeing...but it may just be better. I have sent them an enquiry and hope that the price quoted will not bring on a coronary....

(I figiure that if it beats five years of annoyance value at clogged and broken impellors then it is worth it)


Sasha

[f123olly]

Speed=distance x time
A tennis ball on a measured string and a stopwatch will be about as good as anything you can buy...and its cheap!