Spartan running good, GPS say's otherwise...

[Checkmateguy01]

Put my hand held Gramin GPS in the Spartan and went for a run with the stock power cell batts., boat was running really good but i'm little shocked at the GPS numbers. Ran a full run, when i brought it in the GPS showed only a best speed of 21.8 MPH, i thought it was better than that. I had estimated (guessed) about 27-28 mph, but didn't get it, according to the GPS. I had the batts on the charger for several hours at a slow 1 amp charge, topped them off for a few minutes a 3 amps, both were showing about 10.50 volts. I wasn't making very long full throttle passes, lake was a little choppy, full throttle bursts of maybe 50 feet (judging by our 70' feet of lake front) so maybe it wasn't giving the GPS time to reach full speed, wishfull thinking? The boat is definatly faster with the DTX5000's, but i did not get to run them this weekend. Several people were watching as i ran the boat, over heard someone say "that thing goes like a bat outta hell", it was running good. I had the batts all the way back, strut slightly positive, tabs neutral, and the X442 prop. I can't say i'm not happy with how it runs, i'm having a blast with it and am running the boat in conditions i would'nt dream of running my SV27 in, i just wish the GPS speeds were a little better...

[roadrashracing]

Did you have the battereis all the way back, I never got much more than 27 28 out of mine but its still fun.

[dag-nabit]

GPS units can generally provide very accurate speed measurement, but there are factors that can interfere with the accuracy.

The frequency at which the GPS receiver updates information from the satellites is one factor, how many satellites the GPS is connected to is another, the more satellites, the better the accuracy on both positioning and speed.

It is commonly accepted that GPS units can have difficulty determining accurate speed on short, rapid acceleration runs, due simply to the lag time of transmitting signals. Even though the GPS receiver may have a sample rate of 2 m/sec, the data can lag the actual event (I have seen it written, by as much as 1 second) due to the time it takes to transmit signals from the satellite.

Not an issue when calculating the speed of a car, bicycle, or pedestrian traveling several meters (yards) at relatively constant speeds, or at a steady acceleration rate.

But our boats are capable of going from zero to all out in very short distances, and then decelerating.

Your GPS may well be providing accurate information, but if possible, when the water conditions allow, try getting some good long straight runs in and see if there is a change in how the GPS responds.

Kevin

[Checkmateguy01]

Did you have the battereis all the way back, I never got much more than 27 28 out of mine but its still fun.

Yup, batteries all the way back. I have the boat set-up as "fast" as possible. I gotta think i'm gettin at least 25 mph with the Power Cells, dag-nabit might be right about the GPS lag. I'll try again with the DTX's next weekend.

[Brushless55]

Yup, batteries all the way back. I have the boat set-up as "fast" as possible. I gotta think i'm gettin at least 25 mph with the Power Cells, dag-nabit might be right about the GPS lag. I'll try again with the DTX's next weekend.

If your doing a full out run for longer than 2sec then the gps will refresh and get you the top speed
but I would think this boat on the stock Nimh packs should get 25mph all day long??