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georgerace
Joined: 25 Oct 2006
Posts: 788
Location: Albion, MI
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 Posted: Mon Mar 24, 2008 10:34 am Post subject: Positive Flap Position |
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In a positing about 701 Flap Controls, Dirk Slabbert down in Piketberg SA mentioned his idea to provide 2 to 3 degrees of positive flap position.
I wonder if anyone else has experimented with this idea and can report results obtained. Used in conjunction with elevator trim, it would seem that you would be able to "adjust" your level flight attitude for least drag and best cruise fuel economy over a small range, by making this small change
Since I have incorporated electric flap control, it would be a very easy adjustment to make when rigging the flaperon position.
George
CH-701 Kit (N73EX reserved)
Getting close to finish.
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dirkslabbert(at)telkomsa.
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| Posted: Mon Mar 24, 2008 11:19 am Post subject: Positive Flap Position |
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George, I think you got it right!
The idea is to somewhat smooth out the downwash from the main airfoil, by setting the flaperon so it blows up slightly.
Remains to be seen!
Just for interest I made my rear stab, slightly adjustable, + or - 3 deg, to perhaps find the best cruise.
I have'nt worked on mine for 3 months, but at it again, now or never!
'Best,
Dirk.
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ronlee
Joined: 25 Dec 2006
Posts: 141
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| Posted: Mon Mar 24, 2008 12:50 pm Post subject: Re: Positive Flap Position |
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I have electric flaps on my 701. I am able to put in a few degrees ( maybe 10, I can't remember) of positive angle, up on the trailing edge of flaperons, also known as re flexing. I get 2-3 mph more speed in normal cruise (4800 RPM) without changing the throttle setting. When I do this my nose comes up so I have to trim it down to maintain level flight, indicating needing less down pressure from the tail and less weight to the main wing. Is this a more efficient way to cruise? it appears so. I love my 701 as much as the first time I flew it. I now have over 100 hours on it. I fly it every chance I get.I built a Titan that I could reflex  the flaps and it helped the speed too. I then reflexed the ailerons which gave me a bit more speed. It would stall at a bit higher speed if I landed with reflexed flaps. I had no control over the ailerons though, as they were set in a reflexed position all the time.Ron LeeTucson, AZ
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Ron Lee
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rsteele(at)rjsit.com
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| Posted: Mon Mar 24, 2008 3:34 pm Post subject: Positive Flap Position |
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The CTSW light sport plane by Flight Design actually uses positive flap position for cruise flight. I think it's about 6deg.
Ron
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rtdin
Joined: 16 Mar 2008
Posts: 46
Location: Florida panhandle
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| Posted: Mon Mar 24, 2008 4:24 pm Post subject: Positive Flap Position |
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Most competition sailplanes use reflex flaps and I heard that Maule uses 7 degree reflex in cruise.
Bob Dingley
**************
Create a Home Theater Like the Pros. Watch the video on AOL Home.
(http://home.aol.com/diy/home-improvement-eric-stromer?video=15?ncid=aolhom00030000000001) [quote][b]
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graeme(at)coletoolcentre.
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| Posted: Mon Mar 24, 2008 4:55 pm Post subject: Positive Flap Position |
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I think you will find the CH 701 flies to slow to be helped by fositive flap.
a reduction in negative from spec creates a higher nose attitude.
Graemecns
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notsew_evets(at)frontiern
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| Posted: Mon Mar 24, 2008 5:16 pm Post subject: Positive Flap Position |
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I used 3 degrees negative on my Avid and it would get a long 14 knots faster than zero flap. Also I had 1 1/2 neg on my Kestrel 17 meter sailplane. Awesome difference in speeds..
Steve
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rtdin
Joined: 16 Mar 2008
Posts: 46
Location: Florida panhandle
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| Posted: Tue Mar 25, 2008 5:32 pm Post subject: Positive Flap Position |
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We see that reflex flaps can give you a couple of knots. Now on the other hand, 3 or 4 degrees of down flap on a Cessna Birddog in cruise would also give you a couple knots increase. It aint a rule if it doesn't work every time.
Bob Do not archive
**************
Create a Home Theater Like the Pros. Watch the video on AOL Home.
(http://home.aol.com/diy/home-improvement-eric-stromer?video=15?ncid=aolhom00030000000001) [quote][b]
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