foosball_movie

Hi. I recently completed a Sig Wonder with an OS .25 FX engine. This weekend I had a 20mph tail wind and the Wonder was very quick.

I'd like to know how quick. What's the most accurate way to measure? I thought about measuring the length of the field then taking a time measurement at the front and end when the plane crosses, but that doesn't seem very accurate.

Is a radar gun the best way?

Can I put something in the plane to measure air speed?

Mike Connor

My Feedback: (5)

Time over distance is very accurate if you can get a good time. Parallax is a problem if only one person is doing the timing.
Radar gun is good but they are not cheap if you want a decent one.
Doppler speed check seems accurate and all you need is a good audio of a close high speed pass and the free WaveOScope program.
If you have a video I will check it for you or you can download the program and check it yourself.
http://www.sprut.de/electronic/soft/scope.htm
It is in German but Google will translate for you.

Mike Connor

My Feedback: (5)

http://www.rcuniverse.com/magazine/n...roduct_id=2076
Cheap on board speed logger.

foosball_movie

Thanks Mike.

I downloaded the wavescope application. Pretty cool, actually. I'm going to take my video camera out to the field and give it a try.

Couple of questions. Since the instructions are in German, I'm not sure what some of the features do. See attached image. Anyone have English instructions?

Also, to get the speed, do I just left-click on the far left of the wave form and then right-click on the far right of the wave form? Should I do this several times to get a more accurate measurement?

Mike Connor

My Feedback: (5)

Yes, even though the lines are further apart as you go to the right the speed should be consistant. I use Windows sound recorder to get a wav file from my videos. Attached is one of mine.

foosball_movie

Sheeeeeeeeeeesh.

180 MPH !

What plane were using?

Mike Connor

My Feedback: (5)

That one was not my plane but a f3d that someone owned. I have checked many planes and only a few were mine.

Bad_Daddy

60 miles per hour equals 88 feet per second. 30 mph = 44 fps 120 mph = 176 fps
If you use a stopwatch to fly the length of a football field, (100 yards = 300 feet), and divide 300 by the number of seconds it took, your answer will be in feet per second, and you can translate from there to mph.
If you need to know to a greater level of accuracy than your stopwatch abilities can produce, buy a radar gun.

Mike Connor

My Feedback: (5)

In this case it would be a "Foosball" field!
Combatpigg uses two timers to eliminate parallax error and probably comes up with some pretty accurate #'s.

combatpigg

My Feedback: (3)

My timers use cell phones to communicate. They are stationed under the raised tailgates of SUVs,sitting in chairs, with the edge of the tailgates providing the reference to the start/stop points in the sky. The person in control of the stop watch is at the finish line, the person who tells the timer to start the stop watch is at the start line. Last summer we ran a 175,a 155 and a 130 mph plane several times and the results were amazingly consistent, usually within a couple hundreths of a second from run to run, if not dead on sometimes.

I think that $40 electronic gizmo is the way to go VS having to buy your timers beer and lunch.

The SUVs provide some protection if something goes wrong.

foosball_movie

Ok. I captured the audio on my Wonder and finally put it into the wavescope application. If I did it right, it came out to 198 KMph or around 124 mph. Seems a little fast, but the plane was moving.

Here's the wav file if someone can verify:

http://www.foosmovie.com/images/wonder%20(6).wav

Mike Connor

My Feedback: (5)

Some sound files are easier to read then others. I had trouble following the lines on yours but you may not be too far from what I did see.