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Author Topic:   Pitot tube and speedometer
ConB posted 03-23-2008 05:48 PM ET (US)   Profile for ConB   Send Email to ConB  
With the use of GPS speed calculating units does any one have an argument in favor of maintaining a pitot tube speedometer on their Whalers?

I want to move my depth sounder transducer to the position the pitot tube is in and the thought stays in my mind not to put the pitot tube back on.

Con

contender posted 03-23-2008 06:55 PM ET (US)     Profile for contender  Send Email to contender     
I never like the speedos anyway I would take it off. (they never worked right and got clog all the time) If your boat is already set up with the right/correct prop, and other than crossing the ocean (for navigation) do you really need to know your speed? And like you said you have it on your GPS...good luck
kwik_wurk posted 03-23-2008 07:03 PM ET (US)     Profile for kwik_wurk  Send Email to kwik_wurk     
Yeah, there is no reason to keep it. I took mine out. In fact the GPS is much more accurate that a pitot tube (they tend to read a little high in the upper speed range, and then not at all a trolling or manuevering speeds).

The only thing that makes me cringe is the idea of drilling more holes in the transom.

If you re-use the exsisting holes, make sure they are water free. I usually stick a coton string, or cloth in the hole and tape it inplace. I come back a few hours later and see what I have.

Chuck Tribolet posted 03-23-2008 09:39 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
If you deal with significant currents, pitot tube and paddle
wheel speedometers tell you speed THROUGH the water, while
the GPS tells you speed relative to the bottom. Ask yourself
if you care.

My depthfinder came with a paddlewheel. I hooked it up --
if the GPS craps out, it can help me get home in the fog
by dead reckoning.


Chuckh

swist posted 03-24-2008 09:26 AM ET (US)     Profile for swist  Send Email to swist     
Some high-quality pitot-type speedometers can be quite accurate. Airplanes still use them to determine airspeed - like a boat airspeed is not quite as interesting as ground speed, but it's still important in ascertaining engine performance and fuel management.

If I had a boat in Maine up near the Canadian border where there are 20' tides and all kinds of inlets and outlets with incredible currents I would want to know both speed over water and speed over ground, but for your average boater in your average locale, I agree GPS-based ground speed is good enough.

Chuck Tribolet posted 03-24-2008 11:51 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Airspeed is esp. important to an airplane: it's what keeps
the plane flying. If you have a plane with a 60 knot stall
speed, a 40 knot tail wind, and an 80 knot ground speed, it's
falling out of the air because the airspeed is only 40 knots.


Chuck

ConB posted 03-24-2008 07:02 PM ET (US)     Profile for ConB  Send Email to ConB     
Thanks for your thoughts on the speedometer.

At this time I think I will remove the pitot tube.
Install my new ELVIS (ELectronic Vessel Information System, a Garmin 540S) and continue to carry my hand held GPS for back up speed and log. I also carry paper charts like my father taught me.

Con

JMARTIN posted 03-25-2008 06:02 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
My paddle wheel is used quite a bit when trolling, my paper charts have never blinked out and stated that the antenna signal is lost. John

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