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Old Apr 06, 2006, 05:47 PM
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chara's Avatar
Munich, Bavaria
Joined Dec 2004
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Quote:
Originally Posted by Gene Bond
My concern is the increased drag of the upper wing's ailerons causing the adverse yaw... I'm studying the effect and solution on a current design, right now. Don't know much yet, but I'm learning!
Gene,
normally the yawing moment due to drag difference in consequence of asymmetric aileron deflection should not be so much of an issue on planes with short span. On sail planes, yes! The lever is much larger there.
If you have a symmetric profile and low AoAs, theoretically this yawing moment should be even zero. So I would not be worried too much about that for your current design.
However if it has a large span (w.r.t. the fin's lever) you may mix in some proverse rudder or if you have separate servos for each aileron do an "uneven" roll-command distribution (deflect the up-going aileron more than the down going), that's what we are doing in our "real world project" right now.
greetings
chara
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Old Apr 06, 2006, 09:55 PM
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Little Rock Regional, Arkansas, United States
Joined Sep 2002
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Nice......

Very nice bipe chara.... Thanks for sharing and all the hard work.. Just looks great.. gotta try one. STRINGFLY <>++++
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Old Apr 07, 2006, 01:39 PM
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Munich, Bavaria
Joined Dec 2004
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Quote:
Originally Posted by STRINGFLY
Very nice bipe chara.... Thanks for sharing and all the hard work.. Just looks great.. gotta try one. STRINGFLY <>++++
thanks a lot stringfly! i think you're gonna like it. it's so much fun!
greetings
chara
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Old Apr 07, 2006, 02:01 PM
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Munich, Bavaria
Joined Dec 2004
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Sooooo....
I just came back from the second test flight.
The larger aileron-servo horns did not do the trick . initial roll response is a bit better but "sustained" roll rate is still quite low (for my personal taste). seems that roll damping of the upper wing is so high that it does not permit fast rolls.
I'd say you're better of with 4 ailerons in any case. I'll do the modification tonight and post the outcome of the next flight hopefully tomorrow.

How is YOUR experience with other bipes??? 4 ailerons needed ???

Besides of that i had so much fun flying it!! it realy made my day!
Flip-overs are so easy, rudder turs, spins ... looks all pretty cool.
it can fly so much slower than everything else that i have build before, it actually moved backwards with some moderate headwind.
I'd say it is not so much a pure 3D aerobatics plane (at least not with the undercambered wings) but it is so much fun - I think you're going to love it!!

cu
chara
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Old Apr 07, 2006, 05:23 PM
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Munich, Bavaria
Joined Dec 2004
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OK I'm done with the linkage - looks promising and I'm confident that it will give much better roll rates.
here come some details of the 4-ailerons linkage. was very simple to do.
take a round CF rod and 4 short pieces of CF tube with matching inner diameter.
drill a hole for the axle into the tubes - test fit the assembly to the ailerons and then fix it with CA.
i use double sided carpet tape to stick the needle to the TE of the aileron and wrap around a strip of clear tape.

this video shows how it works and gives you also an idea of the control surface's throws that i use:

http://www.rcgroups.com/forums/showt...34#post5300328

good night everyone...
chara
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Old Apr 07, 2006, 07:12 PM
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Lake In The Hills, Il
Joined Jun 2005
359 Posts
chara,
Very clean and light aileron linkage!
Man you don't stop thinking outside of the box!!!!
Hope it flys the way you would like, Should roll too fast to count now,,,,, Thanks again for the plans.
windy city
P.S. Love the wiggling video, (sexy in a "plane" sorta way )
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Old Apr 08, 2006, 06:37 AM
gpw
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Chara ... we've had a good deal of trouble getting bipes to roll ... either they roll very well , but won't turn the plane with just the ailerons and elevator , Rudder does turn the plane ....OR the roll rate is so slow it's unnerving ...We tried the 1c wing spacing, reduced frontal area, all that ... ehh !!!flat wings , airfoiled wings ... some do , some don't .....????? 4 ailerons on most ... results unpredictable I dunno' till the flyings done... a Mystery !!!
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Old Apr 09, 2006, 04:04 PM
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chara's Avatar
Munich, Bavaria
Joined Dec 2004
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Flight with 4 ales..ahh, i mean ...ailerons :)

yesterday I tried the 4 ailerons setup and it worked great!
roll rate is just right, now! I would guess around 270°/s. that is for my taste sufficiantly high and still low enough not to loose orientation.
I'm preparing the video right now that will show you the difference.

My recommendation would be to go with the 4 aileron setup. If you are happy with low roll rates it is sure worth a try to enlarge the bottom ailerons (e.g. like shown in pic). that is also if you want to keep it very simple and feel detered by the "complexity" of interlinked ailerons.
I'm curious how JERBEARS modification worked out I hope he will let us know!

chara
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Old Apr 09, 2006, 04:20 PM
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Munich, Bavaria
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Quote:
Originally Posted by gpw
Chara ... we've had a good deal of trouble getting bipes to roll ... either they roll very well , but won't turn the plane with just the ailerons and elevator , Rudder does turn the plane ....OR the roll rate is so slow it's unnerving ...We tried the 1c wing spacing, reduced frontal area, all that ... ehh !!!flat wings , airfoiled wings ... some do , some don't .....????? 4 ailerons on most ... results unpredictable I dunno' till the flyings done... a Mystery !!!
yes, I see. bipes have a bit of their own mind it seems. and all this just because there is a second wing on top.
I bet if we asked a professional aerodynamicist why something did not work he would have a perfect explanation. If we asked another he would have a totally different explanation. this wing interference stuff is a voodoo art....
However, since that was my first attemt on a bipe-design I am pretty satisfied with the result so far.
thanks for the response Gene!
-chara
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Old Apr 09, 2006, 04:30 PM
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Munich, Bavaria
Joined Dec 2004
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Quote:
Originally Posted by windy city
chara,
Very clean and light aileron linkage!
Man you don't stop thinking outside of the box!!!!
Hope it flys the way you would like, Should roll too fast to count now,,,,, Thanks again for the plans.
windy city
P.S. Love the wiggling video, (sexy in a "plane" sorta way )
Thanks for the kind words windy!
did I show you the "budget" version of the likage
(that was before I found the spare cf-parts) ? *LOL*

greetings from Munich
chara
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Old Apr 09, 2006, 07:01 PM
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Lake In The Hills, Il
Joined Jun 2005
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Glad the four ailerons worked out!
I also would like to hear about Jerbears smaller version. But a little BIGGER one might be cool too! (just following thru with what happens to all the plans here. (bigger, smaller, more of this, etc ))
Yours looks good in white and blue. I think this one needs to be made with White Depron, It is on my list.
And whats wrong with the "BUDGET" linkage, it's in my price range
Greatings back at you from the WINDY CITY.
windy city
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Old Apr 09, 2006, 09:16 PM
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indianapolis, indiana
Joined Oct 2002
993 Posts
got her finished a couple of days ago ... this morning was the first chance to maiden. all went excellent. i use gbv 15t 26awg 8040 prop and 830/850 2 cell lipo packs. i have learned that for great preformance, my planes need to weigh around 4.3 oz. rtf w/o battery pack. this gets me in the air at under 6 oz. to accomplish this with this plan i used peeled blucor and kept it to a 19'' wingspan. ended up right on target weight .... 4.3 oz. having some expierence with bipes, these are the things i did to increase aileron authority.
#1 cut down nose height as much as possible w/o changing the really cute look it has.
#2 used bottom wing only ailerons ... cut full length to the tips. also angled the aileron line slightly forward towards the nose.
#3 lowered bottom wing to the bottom of the fuse so that motor does not sit on the centerline at equal distance from each wing. instead it is closer to the bottom wing and gets better prop wash across the control surfaces.
it is cute as a speckled pup !!!!!! flys quite nicely, good range from real slow to quite fast. it is 3 channel (no rudder) and turns on a dime. tail biting loops
(more like flips) and rolls very well for a bipe. nice slow soft landings too.
my compliments on the design ...... it is an eyecatcher !! it is not my intention to indicate that the plans should be changed in any way. i am sure it is a great plane as designed. these are only steps i took to fit my needs.
thanks so much for sharing ..... it's a winner. maybe i can get Gene Bond to do a video some time this week. if so, we will post it. oops, forgot ... flat wings (no undercamber) but with dihedral.

jer
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Old Apr 10, 2006, 02:21 AM
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Michigan, United States
Joined Feb 2006
176 Posts
Jerbear,
Could you post a few more pics? Please. It looks like you dont have the center wing supports (cabane Strut). If this is the case, how is that working out in flight? BTW y our plane looks great. Looking forward to some video.

Hawk
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Old Apr 10, 2006, 04:50 PM
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Munich, Bavaria
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Jerbear, that's excellent news!! congratulations!!!
- she looks lovely! I'm glad everything worked so well and I hope you will have a lot of fun with your Bipie!
Your mods are great - I like it! Extended ailerons (with slimmer struts) are highly recommended, also from my perspective. I will make an update to the plans. I realize you went for smaller size and less weight and left away the styrofoam bracings of the fuse and used some bamboo skewers for stiffening things up - that was the best way to save some weight on this design (I originally went for more robustness) -well done!

Would be great of course if Gene helped you with the video and we could get to see it!
I'm still working on mine cause I wanted to underlay it with some music. Unfortunately "MovieXone" keeps on crashing - I WILL finish it however no matter how!

Once again... you've done a wonderful job and I'm happy to hear such positive feedback!
greetings
chara
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Old Apr 10, 2006, 05:28 PM
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Indianapolis, IN
Joined Sep 2001
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Got a quick chance to check Jer's Bipie out at lunch today... Excellent design & mods. Minimal adverse yaw with just the bottom ailerons, and acceptable roll rate. The tail-biting loops are a blast!

The wind was ~10mph, so we had to fly it further from us than would make sense to video (no zoom on the cheap CVS camcorder), so we'll wait for a calm day.

All-in-all, it's the right size and weight for the CDR motor. Crazy throws help as well. The Parachute landings are cool
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