skaliwag

My Feedback: (1)

Any ideas on why the airlerons on a Bi-plane should be on the top, bottom or both?

combatpigg

My Feedback: (3)

The GOLDBERG ULTIMATE with symetrical wings and 4 ailerons has been a very popular plane in pattern competition. I don't think you will find any bipes with just 2 ailerons able to fly the entire repetoire of manuevers as well. The ULTIMATE rolls right through the centerline of the crankshaft, and snap rolls better than most any other plane I've ever seen. It's worth the extra effort to go with 4 ailerons. I have 4 ailerons on a DRAGON RAPIDE, and it is fairly aerobatic for such a large, underpowered plane. With only 2 ailerons, the wing that is trying to bank the aircraft is fighting the wing that is trying to fly level.

Deadstik

My Feedback: (8)

Skaliwag,

I totally agree w/Mr. Pig...... having gone thru the gambit of Andrew's Aeromasters with every type of wing option plus the Sig Skybolts, 4 ailerons is the way to go if aerobatics is your goal. If you just want to do the occasional roll, then two on the bottom will be ok. With just two ailerons it will be very difficult to get a "roll on a string" type manuever. Hope this helps...

Dan

Carolina Custom Aircraft
aka deadstik....

mr_leffe

Rolling down the runway 5 feet of the concrete at 100 mph isn't really the goal... The biggest IC engine I use these days s a TD.020. How important is the top / bottom in retaliation to the CG.
Much easier to put the mechanics on the bottom. Do they work better on the top or bottom. I was at a museum this w/end and noticed the Tigermoth's are on the bottom and the Fokker has them on the top!

Bipe Flyer

If you decide to go with ailerons on just one wing, make sure it is the wing with the least amount of incidence. On a biplane the higher AOA wing can stall while the other is still flying and if the ailerons are on the stalled wing you have no roll control. Usually if the ailerons are only on one wing they are on the bottom for simplicity, on both models and full scale. They are usually a little more responsive on the bottom wing, but there are a lot of other factors that can affect that as well. I had a bipe with barn door ailerons on the bottom only and the rudder was needed for nice turns. Having built and flown bipes with only 2 ailerons, I will now only build them with 4, unless it is a scale model.

The Fokker DVII is not technically a biplane, it is a sesquiplane (one and a half wings), which means that the smaller wing should stall first, so the ailerons are on top. The Tiger Moth is a true biplane.

ZoomZoom-RCU

Thats a good point Bipe Flyer, regarding the angle of incidence affecting the impact of the ailerons on a given wing. Hadn't thought of it in just that way before. I have biplanes with both set-ups though, but they all seem to work ok. The only one I've got where the ailerons are less responsive than the rudder is a Fokker DVI. But thats just how Fokkers are. The rudder will always be more potent then the ailerons in that situation.

ZZ.

Wazmo

In the situation where the ailerons are on the stalled wing, you could potentially have a control reversal because the aileron deflected upwards (effectively washout) could un-stall that side of the wing while the aileron deflected downwards (effectively wash-in) would keep that side stalled. So, the wing that should be rolling down (aileron up) will be lifting upwards (rolling up) while the wing that should be rolling up (aileron down) will not be lifting upwards and will roll down due to the stalled condition.

Bipe Flyer

That's right Wazmo.

skaliwag

My Feedback: (1)

Thanks for the input all....Here is what I think I will do...
Airlerons on the bottom for simplicity.
1 to 2 degrees more incidence on the bottom than the top.
Use 40% nitro.

Bipe Flyer

You want more incidence on the top wing. Less incidence on the wing with ailerons.

skaliwag

My Feedback: (1)

OK... Got It.

Dukester

My Feedback: (31)

Talking about incidence, I haven't really thought this out exactly, but wouldn't you want the bottom wing to stall out first? I'm thinking that if the top wing stalls first, then you'll be naturally unstable with the CG above the current lift component. If the bottom wing stalls first, then you still have a more or less stable system with the lift force above the CG.

Just a thought and of course neglecting placement of control surfaces.

Duke

Bipe Flyer

It's common to put the bottom wing at higher incidence for the reason that you stated if there are 4 ailerons or no ailerons. Another thing to consider is stagger. The bottom wing on most planes is behind the top wing and if it stalls then the plane is flying on only the top wing and the CG is further back on the MAC. If the top stalls first the CG is further forward. Generally, stalling the bottom wing first creates a softer stall whereas stalling the top first creates a somewhat sharper stall. Regardless, one wing is usually still flying so it is not nearly so pronounced as with a monoplane. Aerobatic biplanes with symmetrical airfoils are usually set with 0 degrees on both wings and the horizontal stab and have 4 ailerons.

Dukester

My Feedback: (31)

Nice to know I'm not completely out to lunch on what I was thinking.

Duke

skylane42

My Feedback: (53)

The great majority of biplanes are set up with equal or more incidence on the top wing. My Ace All Star Bipe had the ailerons on the bottom wing and I have never seen a bipe with ailerons just on the top wing.

rrragmanliam

My Feedback: (1)

Hi Bipe,

Hey as long as we're talking about it what's a simple, light, and effective way to link the bottom and top ailerons. I have a Herr Pits that's about 1/5 complete and after reading this thread I going to add ailerons to the top wing.

Thanks for any help.

Darren

Dukester

My Feedback: (31)

When I added top ailerons to my Pup, I just cut some small horns from ply and cut a slot in the TE of the ailerons. Then I mounted the horns to the extended directly off the back of the ailerons. Linked them with a small threaded rod with a Z bend on one side and a clevis on the other for adjustment. Took out all those problems of how to rig the control horns off the top or bottoms and keep them from binding or locking out.

Something like the attached pic.

Duke

Bipe Flyer

Darren,

I make mine the same way Duke does, except I use cut down control horns. On smaller planes I just use wire and on larger ones I use a carbon fibre rod.

jessiej

Good post, Bipe. Somewhere I have an Aeronautical Engineering textbook printed in the early '30s. You just did a nice condensation of several chapters, as I recall. (Excluding, of course the Beech Staggerwing). Let me emphasize, BTW that I picked up that text as a curiosity. It was NOT still a part of the cirriculum when I was a student.

As a practical matter, as stated in a previous post, the intended purpose of the aircraft will dictate the "best" arrangement. I have an almost twenty year old Lazy Ace, now powered with an OS 1.08 with ailerons on the lower wing only. It does a nice, relaxed form of aerobatics (loops, rolls, Cuban eights,etc, and will fly inverted despite the lifting airfoil. If, however, one wanted more "spirited" aerobatics symetrical airfoils and ailerons on both wings would be in order.

As a full scale comparison of the two styles, perhaps Stearman vs Pitts?

jess

Bipe Flyer

Speaking of the Beech Staggerwing. It has reverse stagger and the ailerons are on the top wing. The bottom wing has flaps. Flaps means higher AOA, so the ailerons are on the top.

The trainer version of the Stearman has ailerons on the bottom wing only. The Super Stearman, used for airshow aerobatics, has ailerons on both wings.

Wazmo

Don't the asymmetric linkages cause differential deflection between the top and bottom ailerons?

Bipe Flyer

Good eye Wazmo. The drawing I posted shows how they are setup on the DP Ultimate. It's actually better to have the horns both on the same side of the control surface, like in the Pitts I'm currently building. (Picture attached.)

The only thing that I can think of is that it might cause a slight yaw effect because the top aileron will move slightly further in one direction than the other.

Wazmo

I had a similar linkage on my E-Flite Ultimate and there was substantial difference in deflection between top and bottom ailerons, but the distance from the surface centerline (about 1/2 inch) was probably larger, especially as a percentage of the surface chord.

A potential problem with your revised linkage is that the pushrod could bind against the upper aileron if there's sufficent throw.

Bipe Flyer

Yes, it could bind. Especially if there isn't much stagger. Maybe that's why the DP Ultimate comes that way; sacrifice symmetry for extra throw. As you can see on the picture in the previous post, there is a lot of throw without binding due to the linkages being fairly close in to the root where there is a fair distance between the top and bottom wing. On my Bulldog, where the ailerons are shorter and the linkage is closer to the tips, the linkage just barely touches the trailing edge of the top aileron at full deflection.

Dukester

My Feedback: (31)

That's one thing I like about cutting my own horns and mounting them off the aileron TE. Nearly impossible to get that setup to bind.

Duke