aseaholm

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The newer short coupled designs have become a lot more dependent on aileron reflex to really get a combat ship dialed in. Initially, folks had problems that looking back I believe could be attributed to improper aileron reflex.

I've come up with a very simple method to determine if your aileron reflex is set at the correct amount. Here are the steps and a simple illustration:

1) Get your bird trimmed to fly straight and level.

2) Fly into the wing at full power and quickly pull the power off.

3) If the nose dips quickly when the power is removed you need to reflex your ailerons. Two turns is usually enough and a good place to start.

4) Continue these adjustments until is just coasts with the power off. Now you'll have plenty of elevator authority to grease it in on landing and won't need dual rates.



This information can also be viewed at:

http://www.teamseaholm.com/forum/topic.asp?TOPIC_ID=29

Enjoy!

A.J. Seaholm
TEAMseaholm
[email protected]

Montague

That sounds like using reflex to cope with a thrustline or incidence problem? After all, raising the ailerons does lower the wing incidence as well as change the airfoil shape a little, right?

Not that I don't do pretty much the same thing already, getting reflex right is a bit part of my flight testing on newly built planes. But usually I use the reflex to fix problems with hunting, aileron flutter, and to get the right inside and outside turning "feel".

Demon

No. While reflex can be used as a cheezey fix for thrustline/incidence problems, in this case it is to properly set up a touchy airfoil.

D

aseaholm

My Feedback: (1)

Montague,

Actually it’s more of a that aileron position looks right thing. Initially, it looked right to line the top of the airfoil up with the top of the aileron. This actually puts the trailing below the center line of the wing and introduces more camber. The additional chamber is like having the flaps down and increases the pitching moment which is trying to drive the nose in the ground.

Since the ailerons are not a perfect fit to the airfoil you have to tune them a little to keep the true characteristics of the airfoil. The Selig 8036 generates a lot of lift for tight turns, but along with this comes a sensitivity to reflex. This is good though, because that’s how you get the good roll rate, the airfoil needs to react well to moving the ailerons up and down with big changes in lift.

The way around this is to just scale up the horizontal 3-4 times but then you’re just carrying a bunch of extra drag around you don’t really need. This slows you down through the turns and makes planes harder to balance because of the additional surface area and weight…

Aileron tuning, an easy way to really get your ships dialed in…


Demon,

Actually, I prefer to think of it as aerodynamically balancing a performance wing design. It fixes a touchy airfoil though too...

A.J. Seaholm
www.TEAMseaholm.com
[email protected]

ChuckAuger

My Feedback: (12)

Yo TICK!!

Glad to see you made it back all right. The day you left was perfect flying weather and I had a blast that afternoon (of course!).

Good to hook up with you guys and hang for a while, have to do it again sometime! [8D]

Montague

That makes sense. I hadn't thought it from the fact that ailerons don't really follow the airfoil. I've always known they were a "close enough" approximation, I just never worried about it. (not that I didn't worry about reflex)

Fwiw, I usually measure reflex by putting a straight edge along top of the wing, and measuring the gap at the hinge line. On the airfoil I'm using at the moment, I usually find about a 1/8" reflex on 1.5" ailerons works pretty well. That's a lot of reflex. I'm now wondering if that's an indication that my airfoil has a high pitching moment. (I went over the L/D and Cd vs AOA polars with this airfoil, but just ignored pitching moment). Don't get me wrong though, I like my airfoil.

I'll have to try the power-off trick next time I'm at the field, I never though of that as a test for reflex.

On second thought, it might not help much on my planes, I tend to run a longer tail moment than you do, so the pitching effect of reflex might be different, what do you think?

aseaholm

My Feedback: (1)

Chuck,

I made it back, I’ll get a couple pictures posted later today over on my forum. Have to drag myself to the gym and play a little basketball today. Thanks for a great time in AMA. I really need to practice up on my pool game… OUCH!

Montague,

“On second thought, it might not help much on my planes, I tend to run a longer tail moment than you do, so the pitching effect of reflex might be different, what do you think?�

I try to set up my planes so the horizontal is not carrying much load. Meaning the airplane is a lot like a flying wing and the horizontal is just there for stability and authority for change in direction. If you’re too heavily loaded you would notice a change in flight from power to no power. It sounds like to me your design is in good shape. If you don’t notice any change with the power off then chances are your reflex is good or like you said the increased tail volume is over coming the pitching moment.

It would be interesting to know what the pitching moment of your airfoil is. This was one thing I looked at when choosing the Selig 8036. Here’s a polar SNACK dumped out for the 8036. SNACK is NOT absolutely correct but for comparison purposes I could run it for your foil and see how they compare.

If you want to keep it under wraps I understand. It sounds like you’re good to go though, you don't need me to tell you that though, you've been kick'n tail with it all year... [8D]

A.J. Seaholm
www.TEAMseaholm.com
[email protected]

jester1a

My Feedback: (1)

Good inforation for us 8036 drivers. Is it universal?

JESTER

OOPS I missed that line on the drawing-- never mind

aseaholm

My Feedback: (1)

Jester,

This trick should work for any combat design, especially if it is short coupled.

I know many SPAD designs are sensitive to aileron reflex. This trick will work in that case also.

A.J. Seaholm
www.TEAMseaholm.com
[email protected]

Montague

Getting a little off topic, but in you're curious, here's a snapshot of my airfoil. I'll mail you an export from Profili here in a few moments (when I find your email address). I'm curious what you think about it's comparison to the 8036:

Cajun

Reflex is needed in flying wing designs to stabilize the wing since there is no stabilizer. Very short coupled designs, like several of the combat ships are close to flying wings with the stabilizers pushed up against the trailing edge, hence needing a little reflex. This usually results in the shape of the airfoil being very close to design parameters. Look at the Clark YS airfoil and you'll see a lot of reflex built in. Pushing the ailerons down to level with the wing bottom distorts the shape of the airfoil.

Spads need the reflex to overcome the very sharp LE which results in ships hunting and being unstable in pitch.[], but this is a sore subject for some.

Cajun

Johnny C!

I may be pushing this thread a little further out, but help me if you can...
I have a Hergett 1/12 P-51, built by John "VooDoo" West. I have a Magnum .25 stuffed into
the nose & it is unbelievably fast. I have always had to trim for level flight with the elevator
a little down. I have double checked CG several times. I recently lowered the incidence, but
I still have to add what appears to be the same amount of down elevator. Could I use your reflex
adjustment to correct this? It's not a real big deal, because it is so fast & flies so good, but it
does bring up an interesting problem & a possible solution.
Thanks,

Johnny C!

Montague

Just try it and see what happens. Just put in a little reflex and test fly, and see if you like the results. If not, just take it back out.

One thing you can do is use a straight edge to check the aileron alignment as it is now. Place the straightedge on the top of the wing, so it touches the TE of the aileron and rests on top of the wing. If there is a gap between the straight edge and the wint at the aileron hinge, you have reflex. Now flip the wing over and do it again on the bottom of the wing. If you have a gap here, you have droop. I've never seen a case where droop is a good thing, so at the very least, make sure the bottom of the ailerons are a straight continuation of the bottom of the wing.

thojo

that works for many, but my SD7062's, you need to make sure the TOP of the wing is flat to the ailerons. If you look at the airfoil in Profili, it levels off horizontal toward the back of the wing..