Xardas26

I recently bought a Viper 500 from GP because I felt the need for speed. According to the 424 class regulations I put a stock Thundertiger Pro 40 engine and a 9x6 APC prop on the racer, and was very pleased with the performance. A few days ago I took my mp3 player out to the field and recorded a few high speed passes in order to calculate the speed using Waveoscope which can be downloaded at

http://www.sprut.de/electronic/soft/scope.htm#download

Back at my house I was very surprised to see that according to Waveoscope my Viper flew 220 kilometers per hour which is like 137 mph.

I didn't expect it was gonna be that fast because in other threads people were talking about 110 to 120 mph. Maybe it was that fast cuz i began the dive from stratosphere altitude. Anybody any other ideas??

Mike Connor

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That does not sound too far off since it was out of a dive.

vicman

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With a crazy dive it is possible. It seems like the W-scope reports a tad fast to me but it is what it is. Not saying you are off at all! Just commenting on my own experience. Welcome to the fast side.

rcdude7

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After doing some quick math, a 6" pitch prop would be turning 24K at those speeds. And that is with zero slip. Can that be true?

Mike Connor

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A 0" pitch prop can pull an aircraft forward since they develop forward thrust at -3* pitch. Can that be true? Props and paint sticks are different.

rcdude7

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Quote:

A 0" pitch prop can pull an aircraft forward since they develop forward thrust at -3* pitch. Can that be true? Props and paint sticks are different.






Okay, that being the case, what would the engine rpm at that speed be?

Xardas26

The 137 mph are based on waveoscope and not some calculation. According to your theory it doesn't make any difference if you're using a 9x6, a 10x6 or a 11x6 prop since all of them move 6 inches forward with each revolution under perfect conditions. But every experienced RC pilot is gonna agree that there is a huge difference between those props even though they all have the same pitch.

Waveoscope is a very accurate program that allows you to easily calculate the velocity of your airplane. The following video shows a Dago Red that was clocked at 369 kph or 229 mph using a radar gun:

http://www.mfc-osnabrueck.com/Speedc...Rekordflug.wmv

I used Waveoscope to measure the speed and came up with 365 kph or 227 mph. In other words, waveoscope was 1% off which in my opinion is a incredible result.

rcdude7

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I'm not saying that a 6" pitch APC must auger through the air as though it were going through a solid mass. I guess I'm more suprised that a stock TT .40 pro would unload to those speeds. Is there a english language version of the wavescope? That is a pretty neat tool.

65010

Your results sound correct.

I have a Q500 with a TT Pro 46, APC 10 x 6 prop, on FAI fuel.

Eagle Tree FDR and radar gun readings show 200+ kph level flight.

240+ kph in a dive from 300 metres. The recorder shows that engine unloads to about 18,500 to 19,000 in a big dive.

How did you record it on the MP3?

Mike Connor

My Feedback: (5)

MAAC magazine did some speed test some time ago and some slower aircraft (well under 100 mph) exceeded their theoretical speed by up to 25%. Things went down hill quick as the aircraft speed increased since drag quadruples when speed only doubles. Drag is a main consideration but along with other variables it would be difficult to calculate speed from pitch and rpm. It would have to be a sliding scale when in different speed ranges and aircraft drag would have to be known.

I am not an expert in this field but do like to read alot about this kind of stuff.

Mike Connor

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You can translate the web page using
http://babelfish.altavista.com/tr
or if you have Google tool bar you can right click the page and translate to English. There are a couple of threads in the last 60 days that discuss all aspects of the program so you may want to do a search.