Pitot tube or paddle wheel speedo......which is more accurate

[Moody Blue]

Any guesses, facts or real test data ? Just curious.

 

[bayman]

Re: Pitot tube or paddle wheel speedo......which is more accurate

This is my general consensus...of course there are exceptions.<br /><br />I would say it depends on the speed you are going. <br /><br />Pitot tube are best for higher speeds and are known to not be good at slow speeds.<br /><br />Paddle wheels are more accurate than pitot tubes at SLOW speeds.<br /><br />Option C, the GPS seems to be the best all around.

 

[craze1cars]

Re: Pitot tube or paddle wheel speedo......which is more accurate

Based on my experiences with both, I agree with Bayman's summary.

 

[brine]

Re: Pitot tube or paddle wheel speedo......which is more accurate

borrow a handheld GPS for half an hour and you can determine the accuracy of your speedo on your boat. Mine (tube) is out 1 mph at WOT (45) , and it is 5 mph low at 20. <br />which style do you have?

 

[Moody Blue]

Re: Pitot tube or paddle wheel speedo......which is more accurate

That was my assumption as well. Always interesting to get other view points and opinions. I've got the paddle wheel type and was curious how accurate they really are. My 14ft whaler style boat with a 40HP Mariner and only me aboard is reading 42mph at WOT. Feels fast but not sure its the true speed.

 

[umblecumbuz]

Re: Pitot tube or paddle wheel speedo......which is more accurate

RodC,<br /><br />You've got an great outfit if your Whaler 14 can hit 42 with 40hp!<br /><br />One downside of paddle wheel sensors is that the shaft tends to get clagged and slows down the wheel. Out of water the wheel should spin like a top. If it's sluggish, the shaft needs cleaning. Happens more in salt of course.<br /><br />Straight line gps seems more accurate at all speeds.

 

[swist]

Re: Pitot tube or paddle wheel speedo......which is more accurate

Fewer and fewer boats are coming with factory-installed speedometers since they aren't that accurate and clog easily, and most people have GPS.<br /><br />Only issue with GPS is it gives you speed over ground. If you boat in an area of significant currents, as I do, you have to keep that it mind - it will tell you how much progress you are making, but not how the engine is performing relative to the current.

 

[trog100]

Re: Pitot tube or paddle wheel speedo......which is more accurate

i have a paddle wheel speedometer on my fishfinder plus a gps one.. allowing for river flow.. tides and such they both seem to read the same at all speeds..<br /><br />gps measures true speed between two ground points and the paddle wheel measures actual speed thru the water.. having both is usefull cos a 5 knt water flow especiall at lower boat speeds makes quite a difference if u want to know how long its gonna take to get somewhere as opposed to "how fast your boat goes"..<br /><br />out of the two for overall usefullness i would pick the gps but for boat thru the water speeds u would need to make a run in opposite directions then average the two out..<br /><br />trog100

 

[b.gagnon]

Re: Pitot tube or paddle wheel speedo......which is more accurate

Most fish finders with the paddle wheel list it as a trolling speed sensor. With mine I notice that at higher speeds it can be off quite a bit, but some boats that I have been in when put up next to my gps have quite accurate. I would guess that placement is key as with any sensor.<br />Pilot tubes have never worked well for me, but at the same time I never gave them much of a chance.

 

[JasonJ]

Re: Pitot tube or paddle wheel speedo......which is more accurate

My pitot tube reads a consistant 3 mph slower than my gps, unless it clogs, then it reads 0. I don't know why I even have it, I am always looking at the rpms anyway, and the gps for my trolling.

 

[KilroyJC]

Re: Pitot tube or paddle wheel speedo......which is more accurate

In my minimal experience with using a GPS for speed, I ran for a mile after coming up to stable top speed, then turned 180 and wend right back over my track, then averaged the two numbers. I figure this compensated for wind, waves, current, etc.

 

[dingbat]

Re: Pitot tube or paddle wheel speedo......which is more accurate

Only issue with GPS is it gives you speed over ground. If you boat in an area of significant currents, as I do, you have to keep that it mind

If you're anchoed in a 5 mph current how fast are you going?

 

[trog100]

Re: Pitot tube or paddle wheel speedo......which is more accurate

u really need the two.. else u dont know.. <br /><br />"If you're anchored in a 5 mph current how fast are you going".. that one is okay.. its when u think u are doing 5 mph but its into a 5 mph current.. now that one really is a waste of time and fuel..<br /><br />the rev counter dont help much either.. going with that five mph current 1000 rpm would give me a very fuel efficient 10 mph ground speed at about 8 miles per gallon but going against it would need about 2400 rpm for a 10 mph ground speed plus about four times the fuel usage to cover a given distance.. if u boat where there are tides and currents u really need to know about em..<br /><br />some parts of the UK have a forty ft variation tween high and low tide and at certain times of year we have tidal bores.. the highest of the year on the river trent where i boat is next next tuesday.. it should produce a three ft tidal wave that comes about twenty miles up river..this wave travels about 6 mph.. the river severn has a six ft one and folks surf for miles on it.. this one comes in about 12 mph..<br /><br />kinda weird anchoring to a floating pontoon and watching the river go past at about 6 or 7 mph.. in the evening u look over the top of the river bank and the current is going one way.. in the morning u look 25 ft right up a steep muddy bank and the current is going the opposite way.. he he <br /><br />mind u we might have "tides".. but we dont have hurricanes.. thankfully..<br /><br />trog100

 

[umblecumbuz]

Re: Pitot tube or paddle wheel speedo......which is more accurate

No tides worth a mention where we are Trog. We're spoiled really.<br /><br />Really, the beef is not about absolute speed or accuracy, is it? It's about 'Where am I?' If you have gps with a combo unit and good mapping, I'm sure most boaters will watch their position far more than their actual speed. They'll watch their revs more than their speed. And they'll watch their fuel more, also.<br /><br />To me, speed is secondary to those other points. Am I alone in this?

 

[Dunaruna]

Re: Pitot tube or paddle wheel speedo......which is more accurate

Originally posted by Stillfishing:<br /> To me, speed is secondary to those other points. Am I alone in this?

I agree to a point. I think speedos are a waste of time unless you are trolling. 1 or 2 MPH can make a difference. <br /><br />I use GPS but I usually don't boat in tidal or flowing waters.<br /><br />Aldo

 

[BillP]

Re: Pitot tube or paddle wheel speedo......which is more accurate

I think paddle wheels are more accurate but never read anything that says why. My "marketing" thoughts tells me pitot tubes are cheaper to make and would be the norm if they were more accurate than wheels. <br /><br />Also, I had an ultralight plane with a pitot tube for airspeed. 5-10 degree changes in the tube attack angle changed airspeed readings approx 10mph. The plane only flew 55mph and that much error was dangerous. It was mandatory to make sure the tube was installed in the same position everytime. I would think all pitot tubes have the same problems.

 

[dingbat]

Re: Pitot tube or paddle wheel speedo......which is more accurate

Your speed is, what it is. You only need to know your actual speed to set up your rig or to boast. <br /><br />It makes no difference to me if I'm running home at 20 kts. or 22 kts. I do the speed that best suits the situation.<br /><br />Having said that that I do most of my fish on the troll so speed has some relevance to my actively. I have both GPS and paddle wheel and use them both when trolling. I typically use the GPS as primary indication and the paddle wheel to determine tidal flow and direction more than anything.

 

[tommays]

Re: Pitot tube or paddle wheel speedo......which is more accurate

well on ski boats with twin air guide speedos and tubes they were right on the money<br /><br />but most people dont want to spend the kind of money that setup cost and they are out of buss now<br /><br />tommays

 

[coleman kayak1]

Re: Pitot tube or paddle wheel speedo......which is more accurate

weel, I always carry a gps, so I've never really tried anything else. GPS seems pretty accurate

 

[Moody Blue]

Re: Pitot tube or paddle wheel speedo......which is more accurate

Looks like a GPS is next on my toy list Then I will know for sure how accurate my speedo is.