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Old 04-21-2011, 05:32 AM   #1
K CLOSE
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Question Got to shake off the rust today- and now I have a few questions for my fellow Watters

In what for me is an increasingly rare occurrence I got to sneak off and fly today. Shook off the rust OK, nothing wrecked and got three planes trimmed in for my Dad on his new-to-him computer radio. Good times.

Thing is I cracked out one of the older planes in my fleet. It's a HET Keith Ryder "EightBall" racer that suffered some minor damage and then sat for 3 years or so. Flew her today and I had forgotten just how fast that little bugger really was. So, that leads me to ask two quick questions to you other folks out there....

First, I was really trying to figure out how fast this little plane is. I was flying at a soccer field that is bordered by roadway. I know traffic was traveling on the road at around 40 mph. I would level off (way) above a car and I would reach the end of the straightaway well before cars were halfway there. I did this in both directions numerous times and the results were pretty consistent. So I'm guessing it's likely over 80 mph. What do you folks think, did I miss something or does that seem like a decent guess? It's running a 10/10 Frio on 11.1 spinning a 8x6 APC.

Second, the plane has very little cooling / venting. If I increased the size of the overall air exits (with no increase in inlet) would that speed her up a little more? or slow her down? It has a small air inlet, with the air venting out hand cut louvers, hollow "exhaust pipes"(chopsticks) and a small outlet cut into the tail. I attached some pics to help explain, thoughts.....


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Old 04-21-2011, 07:15 AM   #2
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Hey now,
General rule of thumb: exhaust should be double the area of the intake.
Also idealy the intakes should be as far forward as possible and low. Exhaust should be aft and high. Idealy right above the wing just ahead of the wing trailing edge. That's a low pressure area and helps draw out the hot air.
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Old 04-21-2011, 02:06 PM   #3
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I've heard that before, but I thought it only related to the efficiency of the cooling. Does that rule apply to increasing / decreasing drag as well? I full well realize that this is going to make negligible differences at best, but I was thinking of maxing out efficiency and then seeing if I could get it checked somehow. If I was making a "speed run" would it be better to tape over the air inlet and exhaust for the run or does none of this really matter?

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Old 04-21-2011, 03:05 PM   #4
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Somewhere in the model forums is a load of information on measuring model speed using the 'Doppler shift' affect.
It means recording the fly past using something like a video/sound recorder, uploading it, and then using some software to show the speed.

I'm sure a search should find something.

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Old 04-21-2011, 03:16 PM   #5
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Just looked in the EDF forum and there was a thread on the Doppler speedometer -

http://www.wattflyer.com/forums/showthread.php?t=58662

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Old 04-21-2011, 03:27 PM   #6
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Originally Posted by eflight-ray View Post
Just looked in the EDF forum and there was a thread on the Doppler speedometer -

http://www.wattflyer.com/forums/showthread.php?t=58662
Hi Ray
Heres some more info
http://www.skyhighhobby.com/rc/speed-measurement-tool
http://translate.google.com/translat...005-10,GGLD:en
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Old 04-21-2011, 04:30 PM   #7
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Originally Posted by K CLOSE View Post
First, I was really trying to figure out how fast this little plane is. I was flying at a soccer field that is bordered by roadway. I know traffic was traveling on the road at around 40 mph. I would level off (way) above a car and I would reach the end of the straightaway well before cars were halfway there. I did this in both directions numerous times and the results were pretty consistent. So I'm guessing it's likely over 80 mph. What do you folks think, did I miss something or does that seem like a decent guess? It's running a 10/10 Frio on 11.1 spinning a 8x6 APC.
...
I've got one, works fairly well:
http://www.wingedshadow.com/howfast.html

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Old 04-21-2011, 05:04 PM   #8
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Awesome. Thanks guys. I'm trying to find the Iphone app now. I don't want to add anything to the plane as it's real small. Any opinions on my guess

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Old 04-21-2011, 05:45 PM   #9
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Originally Posted by K CLOSE View Post
Awesome. Thanks guys. I'm trying to find the Iphone app now. I don't want to add anything to the plane as it's real small. Any opinions on my guess
Hi
Heres the site but only the windows link works, the android link does not
http://www.xioptics.com/james/rcspeedo/index.php
Try the App store version of one
http://itunes.apple.com/us/app/rc-sp...320504978?mt=8
Take care
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"When wild the head-wind beat,Thy sovereign Will commanding, Bring them who dare to fly, To a safe landing."
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Old 04-21-2011, 05:55 PM   #10
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Hi
Any one seen these yet?
http://pocketradar.com/
Slightly expensive, but looks really interesting
Take care
Yours Hank

"When wild the head-wind beat,Thy sovereign Will commanding, Bring them who dare to fly, To a safe landing."
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Old 04-29-2011, 03:32 AM   #11
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FWIW the Iphone app didn't work out for me, so I think I'll try to set up a "video day" with a friend and doppler it. I'll hit my F2G Super Corsair then too.

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