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-   -   GPS Speedo? (https://www.sailnet.com/forums/electronics/313578-gps-speedo.html)

Rob_P 03-04-2018 03:33 PM

GPS Speedo?
 
I have been having issues with intermittent speed readings on our Raymarine ST50 and 2092? paddle wheel speedo. As you will all know, its obsolete equipment and I don't want to cut a new hole in the hull for a replacement paddle wheel.

I'm not so much of a racer but in light winds it can be difficult to feel minor speed changes when trying to trim the sails, hence I miss my speed display. Late last season I did try an app on my Iphone but the screen times out and the update rate was too slow.

I'm looking for a "cheap" GPS speed display hand held or panel mount that will work in the 0-10 knot range.

Any recommendations?

Robert

RegisteredUser 03-04-2018 05:23 PM

Re: GPS Speedo?
 
You might want to try a Pad w/gps.
You can put charts on it.

I have a simple, inexpensive Galaxy Tab A.
There are many apps

BarryL 03-04-2018 09:30 PM

Re: GPS Speedo?
 
Hey,

I don't know what you mean by 'cheap' but you can buy basic gps unit for under $100. You can get a better hand held GPS with charts and everything for under $300.

You can use an iphone or other smartphone with a $10 charting app, but it will kill your battery quickly unless you provide power to it.

Barry

hellosailor 03-05-2018 12:26 PM

Re: GPS Speedo?
 
Got an obsolete Android phone? If not, you can also buy one dirt cheap, just install a GPS speed app on it, a 12v power cord, and velcro it in place until you get a new paddlewheel.

An intermittent paddlewheel speed is usually a bad connection, corroded, loose, or cold solder joint. Could be the cable or the instrument.

RegisteredUser 03-05-2018 05:22 PM

Re: GPS Speedo?
 
Maybe check for any living or nonliving things in the area of the small wheel.

fallard 03-05-2018 08:52 PM

Re: GPS Speedo?
 
A problem with using GPS for sailboat speed is that you are measuring speed over the bottom—not speed through the water.

If the water is moving over the bottom (i.e, there is a tidal current) you will be missing an important input to your integrated sailing instruments. Assuming your GPS data is independent, you won’t have a reading of true wind, for example. OTOH, if you don’t have integrated instruments, it probably won’t matter that much.

chef2sail 03-05-2018 10:09 PM

Re: GPS Speedo?
 
Quote:

Originally Posted by fallard (Post 2051415106)
A problem with using GPS for sailboat speed is that you are measuring speed over the bottom—not speed through the water.

If the water is moving over the bottom (i.e, there is a tidal current) you will be missing an important input to your integrated sailing instruments. Assuming your GPS data is independent, you won’t have a reading of true wind, for example. OTOH, if you don’t have integrated instruments, it probably won’t matter that much.

If you are a fanatic about boat speed Fallard is 100% correct. I only really put my paddle wheel in when racing or trying to fine tune sail setting.

Most of the time the GPS ( speed over the bottom) is fine for us.

Only if I were a racer would I spend the money to replace a thru hull and upgrade

KeelMe 04-14-2018 12:12 AM

Re: GPS Speedo?
 
STW is great for set and drift and SOG is great for speed. If you really want to know how you are doing you need both.

You can anchor your boat in a river and STW will tell you your going 3-5 knots while SOG will read 0. Or you could be drifting down the river and STW will be 0 and SOG will be 3-5 knots.

If you are interested in how long it will take you to get from one point to another STW will not hep you.

Minnewaska 04-14-2018 05:53 AM

Re: GPS Speedo?
 
If one is totally chill, they can get away with GPS speed alone. Me, I'm not chill. When SOG is low, I'm all over whether the bottom is fouled, the prop is fouled or the motor working properly (if I'm motoring), did we snag something, are we trimmed properly, etc? I always check current, when out of synch. It would drive me nuts, not to see STW to be able to confirm we are actually moving at the proper speed.


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