Does anyone make Aileron Spades for models?

[RH1N0]

Looking forward to Matt's explanation! I know very little about aileron spades or how they work so I won't bother to make something up in a feeble attempt to sound intelligent

Instead, here's a pic of an aileron spade on a very scale 40% Extra330S by Mark Szufa. The pic is from the Aircraft International image gallery and you can access more pics of the plane at http://www.aircraftinternational.com...tra2/index.htm

Enjoy

.

[RH1N0]

Here is the flight controls section of the Extra300S (full scale) service manual which gives a good explanation of the direct controls:
http://www.extraaircraft.com/Tech-Ma...M300S/CH27.pdf

+-1mm allowable free play on aileron and elevator! That's better then many RC models!!!!

[N726AC]

	Quote: Originally Posted by SargeNZ
	From just thinking it through you could conclude that spades help with both up and down deflection. I would assume that with the aileron neutral you want the spade with a 0 degree angle to the oncoming airflow? Then if the aileron deflects down, the spade is put in a positive angle to the airflow, making lift, since the spade is foward of the hingepoint, it helps the aileron rotate down. When the aileron is deflected upwards, the spade is put into a negative angle, this causes a force downwards on the spade, helping to pull the aileron upwards. Would it not also add to aileron surface area and thus roll authority? NB: This is just what I have deduced, and could quite easily be wrong.

Sarge got it right,here is a shot of one of the spades on my Citabria. I have flown identical Citabrias with and without spades and there is a noticable difference. Also, spades have nothing to do with mechanical counterbalance, just and aerodynamic aid to lighten controll forces.

[Matt Chapman]

Spades. Okay, here we go.
I'll try to keep my thoughts in some sort of order, but I'm sure to bounce around a little bit. As far as RC spades go, it's just going to be my opinion, nothing more, nothing less.

First, control systems in most modern aerobatic planes, both FAA certified, factory built and experimental have push/pull, rods. The exception is the rudder, where the cables are used.

Counter balance Vs. aerodynamic balance;
Not all spaded as created equal. It's just not possable to say that a spade is or is not one or the other. Take the Pitts Special S1-S. The plane was built and designed without spades. As far as I know, they didn't even exist yet. The control pressure on all Pitts aircraft is light and balanced, but always looking for increase in performance. The spade is there ONLY for the purpose of lightnening the aileron pressure at the CONTROL STICK. Move on to the Lazer type monoplane and now you have a spade that is aerodynamicly required as a counter weight. It MUST be on the plane to maintain safety. You also gain the benifits, but it's needed to balance the control to prevent flutter. My CAP ailerons are balanced to 103% to 110% in static.
The spade works in both direction.
they are attached at a hing piont also the pushrod attach piont most of the time. The arms go down, and forward. Not always the same geometry as every design is diff. Take the left aileron....as it goes up, the spade plate leading edge goes down...thus exposing it to the on coming air thus "pushing" it down and helping the aileron go "up". At the other end of this is the right aileron going "down"...in turn it's spade is moving "up" exposing it's bottom side to the on coming air and "pushing" it up. So, they do work together. It's not a one or the other type design. This is how we creat a balance in the system.
Angle of attack, incidence...or what ever you want to call it:
The plate is fixed onto the arm. It's not moveable once bolted on. (except a very cool and inovative design by Leo Loudenslager on his Lazer 200) The spade only moves when the aileron are moved. To trim the spade plate, you first need to know that the plane is trimmed hands off. Then, put the plate on the arms. This is where a it can get complicated. Let's assume a "0" incidents wing. ( the angle that the wing is bolted onto the plane...not changable) The wing passes through the air at some angel of attack...this is changable...with the elevator and airspeed ect...
How do we decide what angle to mount the plate? A few ways... all have their owne feel to them and end result.
Before I go on...look at the one photo of the Citabria with it's spade plate. Level flight, but look close and you can see the leading edge of the plate is raised relitive to the bottom of the wing. the Citabria wing is a flat bottom wing. Most acro mounts have a round wing (symetrical airfoil). If you level the plane based on "0" then put the plate on at zero, you will have some angel of attack of the plate in the air. A wing does not pass through the air at zero....at least not while producing lift. so, in effect the plate will be passing through the air with the leading edges "up" relitive to the oncoming air. This is not necessarily a bad thing or wrong. With a "round wing" the air flowing around it flows in the same basic shape as the airfoil, so this would also lead you to believe that you could mount the plate parallel to the bottom surface of the wing....so air flows over it in a 'zero' effect. This is where you want to start. In this position, you will have a very twitchy stick, no center, no feel at all. Not a good thing. We now start to move the leading edges up or down depending on what we want to accomplish. Please keep in mind as well that some planes have the arms mounted at the front of the plate and others at the back of the plate...so keep in mind that you would have reverse effects fom one type to the other. The closer to center the leading edge the less feel you'll have at the stick, the further from center, the stronger the center. Simple, right? Now throw in the effect of upright and inverted flight while pulling or pushing... As air flows back under/over the wing, you want the ailerons to maintain the same feel, but the air will tend to seperate and will change the angel it hits or passes over the spade. This will lighten or increase the weight of the feel during a pull or push, creating a "digging" of the plate. Almost pulling the stick from your hand. Not good when trying to fly precision. Typically you'll see the leading edegs down just a bit. This will creat the center feel, move out of center with ease and mainatine stability through a push. This however is not cast in stone! everyone has his or her own ideas and pref.
Also, the newer planes, Pitts S2-C, Pitts 12, and Python have been desiged to have all the positive control feels without spades. This was done through use of hing point %, balance and airfoil. No plate = less drag.
It's my opinion that it would be impossable to set up a spade on an RC plane. You just have to have feel feedback to get it to work. We are also working to get a "feel" to the human arm. Our ability to move our arms fast, stop fast or on center is based on aileron weight and feel. The servo will do that based on mechanics every time. (at least a Futaba servo will!! zing!)
Take into account that I'm a pilot....we really need the input of some who may have designed a plane or two...say a Pitts Python maybe....somebody in the Florida area....worked with Curtis Pitts....first name Kevin... Jump in Kevin.
Thats my take guys!
This and a dollar and you get a cup of coffee at Wawa. ( for you west coasters..that our 7-11)
Matt

banged this one out...sorry for ALL the spelling...

[N726AC]

Way to go MC ! I was not aware that the spades on the Lazer and Caps were also a mechanical counterweight.
Next, how about servo tabs? I can post pics Friday of servo tabs,,,,

[N726AC]

couple photos of the spades of an Extra 300L

[IMACmike]

We are also working to get a "feel" to the human arm. Our ability to move our arms fast, stop fast or on center is based on airleron weight and feel. The servo will do that based on mechanics every time. (at least a Futaba servo will!! zing!)

with JR you really can feel the difference!

[kjkimball]

OK, Matt. I'll chime in on this one.

Why spades? Early ailerons such as on cubs, Pitts S1S, Buckers, etc. are Freise style. These had light forces. Rol performance was increased by sealing the leading edge of the aileron to the wing trailing edge. Later, ailerons changed to symetrical style that are round nosed with the hinge line in the center of the radius of the nose. This allowed easier sealing of the aielrons to wing gap but with very high stick pressures. This is the S1T Pitts style aileron and eal monoplane ailerons. From what I can recall, the Zlin monoplanes of the late 60's or early 70's had spades first. When the S1T wing and new aileron came to be too heavy, the idea from the Zlin was used and the forces were reduced. Rumor has it that this idea came during a discussion between the manager of the pitts factory at the time and a friend of our from Texas. It worked.

As it has been pointed out, spades are tuned to the airplane and pilot. Each unique. Yes, the mass of the spade being forward of the hinge line can be used as some portion of the required mass balance of the aileron system. If it is as on the SP95 and a few other designs, do not fly with spades off or the ailerons will flutter and flutter is bad...

Spades can be thought of as additional aileron area. This added area is forward of the hinge line of the aileron and forward area can be used to lessen the stick forces for the pilot. In the 20's the Travelair 2000 had 'elephant ear" ailerons which had a rounded forward section at the tip that resembled that of the mammal's ear. This area reduced stck forces.

Note how the spades on the extra are mounted on a slope relative to the wing, lower inboard. This allows these spades to do 2 jobs. One, lighten the roll stick forces and two, allow the extra to comply with FAA certification of having to be able to lift a wing with the rudder (no dihedral in the wing so needs this). The tilted spade catches the air in yaw and deflects the ailerons to allow rudder/roll coupling.

It is possible to build ailerons that do not require spades. It takes many tries to get it right. Even at that, it is only right for one person on one airplane. We did get it right on the python. The ailerons are much larger than the model 12 that we kit yet hae no spades. There are many other factors that played into getting a spade free set up. Hinge point is only one. Simply changing an aileron from 2 hinges to 3 can change the aerodynamic stick forces.

The idea of using spades on a model would be tricky to sort out. It is very easy to have spades that are too large and over drive the controls. In this case, you could actualy end up with tension loads on the linkage instead of compression loads. It would be possible to have the ailerons stick at full deflection. Setting the pitch angle on the spade is critical and if it is off from optimum, the ailerons may have zero centering or get snatchy in some flight attitudes.

So, to be more direct to the original poster's questions of are model spades available? I don't think so. Should they be? Nah,....most likely not for the many reasons pointed out in this thread. Knocking them off in wing bags, in the grass, etc., would be a real problem.

Kevin Kimball
www.pittspython.com

[Matt Chapman]

Kevin,
Thats a great response! Thank you.
I'm working on trying to get my ailerons better this coming season. I'm going to have to make up a set of new arms as the new Extra arms don'f fit my older style wing. I would also like to try the tilt to the plate as well. We'll see how that goes.

Take care!
Matt

[rdgood]

Matt and Kevin,

Do you think that there would be any advantage to adding any sort of aerodynamic counter balance to take some of the load off of the servos?? From what it sounds like the only way to tell (with the current info) is be able to feel the forces during flight. I am wondering if a person could set up some kind of rig with an ammeter and detect the deflection forces??

Probably more work than its worth but hey its what we modelers do!!!!


Ronster

[asleep]

We had a crack at spades about a year back. Indeed, they did lighten the torque on the servo's but they made everything so 'twitchy' as when their angle of attack came to an incidence that would put a moment on the control surface, it was like running +ve expo. And making things worse their efficacy is different at different speeds.

The Red Bull lads are fine as their flying as fast as they can all the time and hence, the spade config is more predictable.

My $0.02??? 3M IMAC will happily run with 2 x ganged (or separate) 8511's. Unless you're Mark Leesburg who would need about 4!!

cheers
sleeping

[yak55x]

I have been studying the possibility for a while as well. I've come to the conclusion that the angle of the spade arm effects it in that the up aileron spade digs at a higher agle of atack than the aileron that goes down. This would be the effect of the spade arm forward sweep angle.

I sold my Yak 55M so I can't take picture to show you but it is very obvious when you see it. And the Yak has HUGE double spades. The up aileron spade really digs hard. Hence the name of spade? Makes sense. I don't know who invented them.

This causes more down lift and drag than the opposing aileron which pressures that aileron to deflect farther up. If the ailerons were not connected via cable or pushrod this would be an unstable condition but when interlinked there is still a positve neutralizing force - but less, which to the pilot is a lighter stick force.

I think it would be easy to set them up with an eagle tree e-logger recording the amps from the Rx pack. It would be easy enough to compare pre and post amps while flying mostly roll manuvers.

Better yet would be to use the more advanced eagle tree systems that record servo position and isolate the aileron servos amps. The catch is that the ailerons have to be mechanicaly interconnected for them to balance out the forces.

The added bonus of static balancing would increase the aileron flutter evelope speed as well.

None of this is rocket science - somebody will do it and then everyone will jump on board knowing that spades are a lot lighter than servos and batteries. who want's to be the guy? haha

The aggressive hinging techniques may be better suited for models and easier to set up but I fear the gap created would lead to less roll performance in the end. Most full size mounts are using both aft hinging and spades but the latest designers are realizing that they can just use 25% hinges on the outboard side of the aileron and 35-40% on the inboard hinge to lighten the forces. But again - aileron gap sucks. More the suckier. But how much roll can you use anyway?

I just got back from the Red Bull air races in Monument Valley and the roll rates are blinding. Mush faster than you'll see at an IAC contest. It's amazing - I love those planes so much it makes my eyes water.

Servo tabs are interesting too, allthough not very scale and may not give a very "tight" feel. Just an intuition - may be allright on models though. I was thinking of trying it.

Why nobody does all this? It's easier to buy another servo - or three

I'll get around to trying it and post the amp reading ect.