Fan-fold experts, lend me your opinions... - RC Groups
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Aug 30, 2003, 12:47 PM
Self-taught crash expert
cynewolf's Avatar

Fan-fold experts, lend me your opinions...

I am relatively new to R/C, but I would consider myself in a
transition between beginner and intermediate maybe. Anyhow,
I have been getting the urge to fly a plane with ailerons on it...
so I made a wing with no dihedral (di- or poly- hedral will simply
fight ailerons, right?) and put it on my "mostly-Frog" favorite
little flyer.... sans ailerons for the first test flight! Wing span was
several inches greater than original Frog dihedral wing, so she
had a nice amount of extra lift. However, no dihedral, no
ailerons, NO CONTROL! I am amazed I got the poor bird down
in one piece! I had to muscle that thing, wouldn't level out to
save it's life, and the rudder wasn't all too helpful, but it was all
I had.

Well, now I not only understood how a dihedral wing helps, I had
first hand knowledge of how badly I need one! =]

So, last night a revamp the same wing, cut some ailerons in LAR
fashion, hook them up to a single servo centered under the wing.

Waited all night for the sun to wake up (I was awake, what's it's
problem!?) was at the flying field at the break of dawn. First flight
needed some trimming, banking to the right rather sharply. Not
alot of help from trimming the ailerons, but it seemed OK at first.
Level her out, try my first turn, using ailerons and rudder together
as I thought I should, what a fight! I brought her down, thinking
maybe a need to reverse the channel the ailerons are on. Not a
good choice... crash. Well, I'll link / mix the ailerons - rudder, first
I did it in NOR mode. Bad. Then I did it in REV mode... not TOO
bad, but compared to the control I am used to with elevator /
rudder/ dihedral this stinks! Also have troubles keeping a nice
level craft.

I brough her home, ready to crawl back to my dihedral wing and
beg forgiveness for being unfaithful!

I am wondering if the undercamber wing is a bad combo with the
ailerons... or maybe I had too little travel on the ailerons... they
are supposed to move opposite right? When one is up, one is

Maybe the shape of the wing tips needs some mod?

ANy bright ideas are greatly appreciated! Thanks and have a
great Labor Day weekend all!
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Aug 30, 2003, 12:56 PM
40%, 5% whats the diff?
TeamSME's Avatar
When you move the stick to the left the left aileron comes up and the right aileron comes down. Vice versa for right. Dihedral helps a plane get back to it's normal flight path.
Aug 30, 2003, 01:41 PM
The effect is sadly temporary
Hippo's Avatar

If you're using baked wings (looks like you are) I would taper the wing, so that it has the full chord at the center, and you take an inch off the trailing edge at the tips. This will create washout, and help to improve stability.

Also, yes, ailerons aren't all that effective on an undercambered wing like that, but on my Shark, I found I got the best results mixing 50% rudder with the ailerons.

Like TeamSME said, make sure everything is moving in the right direction. You'll also want some differential if you can make it happen. That is, the aileron that's moving up should move farther than the one that's moving down. If you position your control horns right, this is automatic... Unfortunately, I can't remember which way they need to go for that right now...

Good Luck, Stick with it.

P.S. The ailerons will become a lot more effective if you sheet over the bottom of the wing to create a flat bottomed airfoil.
Aug 30, 2003, 05:48 PM
Self-taught crash expert
cynewolf's Avatar

Thanks for the ideas

I'll put some more effort into getting this to work...

I guess the bottom line is, if it will end up being LESS responsive
than just rudder / elevator then I won't keep it.

I reshaped the wing, I already just by chance had the differential
set up... not on purpose I assure you.

I don't know about flat bottom... sounds like it'll be something
more than just slapping a sheet of fan fold on... maybe some
split F3?

Thanks again!
Aug 30, 2003, 06:18 PM
The effect is sadly temporary
Hippo's Avatar

It could be that simple

A sheet of fanfold beveled at the edges to fit nicely up into the bottom would work nicely. You could also use saran wrap or something to cover the bottom. The foam sheet will add a little weight, but it will really reduce drag, so you'll probably come out even.

Aug 30, 2003, 09:14 PM
Foam rules
Thatovalguy's Avatar
With a undercamber you do need the up aileron to have more angle than the down aileron. Being the down aileron creates more drag and will cause the plane to yah the wrong direction in turns. I have a few undercamber planes in the stable that are vary aerobatic on elevator and ailerons, One is my Fan fold fun jet 75 and that plane is a real blast to fly. As far as coupling rudder and ailerons, I never have done it or needed it sept on 1/4 scalers that I have.