Spoileron question

[Guz]

Ok, I guess I'm a bit naive, but I'm a bit confused on the accepted definition of what spoileron's are.

Looking it up, from what I can find, the general avaition definition is when spoilers ("Spoilers are plates on the top surface of a wing which can be extended upward into the smooth airflow and spoiling the air") are used as ailerons (increasing drag and having the aircraft yaw to one side) . Like the B52 Stratofortress bomber.

Where-as in the R/C community, it is when ailerons (control surfaces on the trailing edge of the wing) are used to act like spoilers ("spoilerons are on the trailing edge of the wing, but move upwards to 'spoil' the lift")

Why the differences?

I'm asking this because I'm contemplating using the first definition on a RES sailplane, and wondering how things will work out.

[rdwoebke]

I'm asking this because I'm contemplating using the first definition on a RES sailplane, and wondering how things will work out.

If you are intending to fly that RES sailplane in a contest, you probably won't be allowed to. Normaly the rules prohibit seperate activation of the spoiler surfaces.

I have had a Paragon where the spoilers were supposed to act together but for whatever reason did not on an occasion. I did not personaly feel the turning effect was that useable. It might be because our models travel pretty slowley.

YMMV

Ryan

[Guz]

No competition, just having fun type of thing.

[Skymangler]

I have an OLYII with spoilers mixed to the rudder. I made sure I could switch the mix off if someone thought it was unfair. I have flown in RES contests, I have the advantage of usually placing so low that no one cares. I really like how they work. The OLY is much more responsive to rudder with the mix turned on. I would estimate they double rudder effectiveness. I turn them on on launch and landing and off while thermaling. I used a couple of submicro servos. Much simpler than all that linkage. I use a Multiplex transmitter so the mix is not a problem. Not sure if that would be the case on other radios.

[Guz]

Ok, so what I want to try is do-able.

But, there still is the question on why there is a different definition from general avation and R/C of what a spoileron is?

[rdwoebke]

Ok, so what I want to try is do-able.

But, there still is the question on why there is a different definition from general avation and R/C of what a spoileron is?

Probably because RC spoileron is a convenient way to add glide path control to an existing design. But, when you are talking a man carrying plane that costs many thousands and has to be certified etc, people don't do "cheazy" solutions like we might come up with for a cheap/simple model. When computer radios became the norm, a plane that would previously have a Y cable for 2 servos for ailerons now gets seperate RC channels and why not get a little glide path control while you are at it. Spoileron seemed to be the natural name for it.

I have RC spoilerons active on my 2 meter Ray Hayes Osprey. It certianly helps with the spot landings.

Ryan

[JimNM]

I use "......eron" to describe the use of one servo for each aileron that is electronicaly mixed to allow for movement in opposition (ailerons) or in tandem (up=spoilerons, down=flapperons)

JimNM

[Bill Glover]

But, there still is the question on why there is a different definition from general avation and R/C of what a spoileron is?

'Spoilerons' are conventional ailerons that can be raised together to act in a similar way to spoilers, there are no full size aircraft that do this as far as I know. 'Spoilers' are not the same thing, even when they can be extended differentially for roll or yaw control as per the P-61, B-52, etc.

Flapperons are ailerons that can be drooped as flaps .. a number of full-size have this and they are called flapperons there, too.

[Whorges]

I fly R/C and hang gliders. I've seen application of both definitions. I would suggest that the 2nd definition is loose terminology stemming from the convention of a given surface having more than one application. For example:
Flying wing-- ELEVator + ailerON = ELEVON
DLG-- FLAPs + ailERON = FLAPERON
I more formal term for the 2nd definition you gave would be Crow but crow also implies the use of landing flaps. In your explanation you implied that spoilers reduce drag. The increase drag and spoil the lift. In the case of rigid wing hang gliders only one spoileron is activated at a time. The drag yaws the plane and drops the wing imparting roll.
Hot pockets,
Whorges

[Bill Glover]

Yes, the normal definition of crow braking is ailerons raised and flaps lowered (i.e. requires 4 control surfaces on the wing).

The prime role of spoilers is to destroy lift. Prime role of airbrakes is to create drag. Prime role of flaps is to add lift, although at higher deflections they can give a lot of drag too.

[ferincr]

The prime role of spoilers is to destroy lift. Prime role of airbrakes is to create drag. Prime role of flaps is to add lift, although at higher deflections they can give a lot of drag too.
Question here...
I'm modifying a set of wings and I decided to add flaps to be able to reduce speed at landing since spoilers don't seem to reduce speed ( at least not a lot).
I've been thinking in keeping the spoiler and use them with the flaps in a "sort of" Crow. Now would they work ok or they'll counter act to each other???
(according to the above definition)
Any ideas?
Fernando

[Whorges]

When you say reduce speed at landing what your technically requesting is reducing stall speed. Flaps can be used to add camber if they are a significant portion of the cord (different airfoils have different reccomendations for flap percentage--from the reading i've done it usually falls between 1/5 - 1/3 the cord).

You've probably seen pictures of planes on final approach with 90 degrees down flaps. I'll agree it's sexy looking and has its application, but based on your statement of looking to "reduce speed at landing" I'm not sure this is the BEST solution. On the other hand, if you're looking to have strong control over your glide ratio so that you can land in a small field or catch a wing tip (DLG) or hit the bulls eye then 90 degree flaps can help alot; and so can spoilers.

However, if you truly want to be able to land with as little as speed as possible then what you need is control surfaces which modify your wing from it efficient cruising and thermaling mode to it's maximum Cl configuration which happens to be--thermal mode! No spoilers need apply.

The benefit to the wing you described is that if you get into cloud suck and don't want to loose your plane to the big thermal in the sky engage all possible drag mechanisms and go for a much more aggressive dive then your plane could ever survive without the drag. In normal flight config sailplanes can dive and attain speeds well beyond their structural limits, but with the increase drag the terminal velocity at a given dive angle is greatly reduced--allowing successful escape from wide spread lift.

I live in CT and rarely have I been able to find such lift, and it's not from lack of looking, but if you live in places like AZ this may be a very useful function, or simply an interesting flight characteristic of your design.

Good luck and have fun,
Whorges

[rdwoebke]

Question here...
I'm modifying a set of wings and I decided to add flaps to be able to reduce speed at landing since spoilers don't seem to reduce speed ( at least not a lot).
I've been thinking in keeping the spoiler and use them with the flaps in a "sort of" Crow. Now would they work ok or they'll counter act to each other???
(according to the above definition)
Any ideas?
Fernando

When you say reduce the speed, what do you mean? Do you mean reduce the forward speed of the model (glide ratio) or lower the sink speed.

Normally on our high lift gliders, we want to reduce the glide ratio. Spoilers do a good job of this. They kill the lift and reduce the glide ratio. Like this big glider I am holding here. It has a 20:1 glide ratio or better. AKA, for every 1 foot it drops it would travel 20 forward. Now, this is fine if you have a great big open field to land in. But, if you are flying from a baseball diamond you can't land it on the pitcher's mound without overshooting and hitting the fence. In comes the spoiler. That is the big blue thing in the center of the white section. It reduces the glide ratio to say 5:1 or less. And, an added benefit is if you need to get down in a hurry (say that transmitter starts beeping to let you know you forgot to charge it), you pop the spoiler and point that nose down and you can make a nice parachute descent and not worry about overspeeding it.

Ryan

[BMatthews]

Exactly, the proper way to use spoilers is not as an added drag device but as a way to steepen the glide slope. You don't want to actually dive with them out but rather pull back a little to a near stall and the glide slope really steepens as the model comes down flat. But for contest work I have to agree that these require more planning and forthought than the crow or big flaps where you can dive the model and come down in a serious hurry and when you pull out the excess speed is gone quite quickly.

[rdwoebke]

You don't want to actually dive with them out but rather pull back a little to a near stall and the glide slope really steepens as the model comes down flat.

.

On a strong RES model like the Bubble Dancer (in the picture) or Ava, you can deploy the spoilers all the way and point the nose down to descend quickly if you need to. You can also do the trick where you pull back on the stick and the thing sort of has no forward speed and drops at say 3-5 FPS.


But for contest work I have to agree that these require more planning and forthought than the crow or big flaps where you can dive the model and come down in a serious hurry and when you pull out the excess speed is gone quite quickly.

Likewise with the big spoiler on the BD you can bleed off speed fast. Probably not quite as well as crow on a 6 servo model, but pretty well.

At least that is my experience with the BD and the Allegro Lite (2 meter version).

Ryan

[Bill Glover]

For landing, it's normally spoilers or spoilerons that people actually need. The stall speed is fine (plenty low enough), it's the efficiency of the plane that causes the problem. So you want to add drag and/or dump some lift, to allow a steeper approach.

If you already have ailerons then spoilerons are simple to configure (provided you have a TX that will handle the mixing). They basically turn the wing into a negative camber section, which is pretty inefficient (think of flying an undercambered 'floater' inverted ;)). As well as steepening the approach they do actually allow a slower touchdown speed because you can flare to a much higher AOA without stalling (the upward deflected ailerons effectively add tons of washout to the wing).

For models, flaps (or flapperons) are normally less effective as an aid to landing. Obviously they do have benefits e.g. for changing the wing camber in flight to alter the glide speed etc.

If you don't have ailerons then you're normally looking at a spoiler/spoilers on the wing, or airbrake(s) ... which don't have to be wing-mounted. Years back several designs used a servo to raise the canopy as an airbrake, the other one that works well is a 'split rudder' airbrake. My personal favourite is basically a simple TE flap on the wing, but with a top plate extending forward of the hinge line. So as the flap part goes down the top part goes up. Significant drag with little or no trim change.

[ferincr]

Ooooppss!!!
It seems like I cut my new to be wings for nothing...
Oh well!, nothing to be done now but to keep going ahead with them.

[moonbase1]

Bill, your post with the analogy of “flying an undercambered 'floater' inverted ;) ” brought up a question in my mind. If spoilers (mounted well in front of the TE) are designed to spoil the lift, do spoilerons (at the TE) create “lift” on the under side of the wing to push the wing down? I am still learning about this sort of thing, but in my mind the turbulence created by spoilers seems a lot less controllable than the inverse lift i picture being created by spoilerons. Is this true, or am I way of the mark?

[Bill Glover]

do spoilerons (at the TE) create “lift” on the under side of the wing to push the wing down? I am still learning about this sort of thing, but in my mind the turbulence created by spoilers seems a lot less controllable than the inverse lift i picture being created by spoilerons. Is this true, or am I way of the mark?

That's pretty close. Spoilerons basically modify the wing section, just like flaps. But as they raise, they effectively create a negatively cambered wing - which is draggy and much less efficient, and has to fly at a higher angle of attack to generate lift. Once spoilerons go past 45 degrees you start to get more and more pure drag, obviously if they were at 90 degrees (which is rarely possible) it would be 100% simple drag and they'd actually be airbrakes!

Actual spoilers destroy the lift on the section of wing they cover (as well as causing drag). But the rest of the wing continues to operate normally.

[moonbase1]

If the entire length of the wing had small spoilers, would it be imposible to controll? Or if the spoilers were small enough and only slightly raised would they only "kind of" spoil the lift?

[Bill Glover]

If you had full-span spoilers it would drop out of the sky when you deployed them!

Yes there must be a minimum size for spoilers ... too small and the airflow would simply re-attach behind them. Depends a bit on the section, not usually an issue with models but a few sections used on full-size are really fussy and can even - apparently - be affected by trim tape (used as part of the colour scheme) running span-wise!

[Guz]

Wow, this caused a nice banter of information.

I did find a nice aminmated image of the aeronautical definition of Spoilerons:
http://www.grc.nasa.gov/WWW/K-12/airplane/Animation/airpar/Images/asprl.gif
From NASA (http://www.grc.nasa.gov/WWW/K-12/airplane/spoil.html), the page has some java apps showing how spoiler/spoilerons work.



And a nice image of what a spoiler is:
http://virtualskies.arc.nasa.gov/aeronautics/tutorial/images/Spoilers.gif
Spoilers are devices that are located on top of the wings. Spoilers have the opposite effect from flaps and slats. They reduce lift by disrupting the airflow over the top of the wing. Spoilers are deployed after the airplane has landed and lift is no longer needed. They also substantially increase the drag which helps the airplane to slow down sooner. Source: NASA (http://virtualskies.arc.nasa.gov/aeronautics/tutorial/wings2.html)



Although, I haven't been able to find some decent images explaining the R/C definition of Soilerons. Anyone want to step up?

[Bill Glover]

Although, I haven't been able to find some decent images explaining the R/C definition of Soilerons. Anyone want to step up?

It's simply raising both ailerons together. Do you need an image for that?! I can take a picture of one of my planes if necessary!