Elevons and Elevator

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wtsidney
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Elevons and Elevator

Post by wtsidney »

Anyone have experience or thoughts using elevons and elevator on a twin rail limited-B battle axe clone?

Thinking mixing elevons with elevator would be an easy mod using a couple mini servos and would improve turning and looping. Have been flying against a couple of flying wings that turn on a dime.
Last edited by wtsidney on Tue Jul 10, 2012 3:00 pm, edited 1 time in total.
Bill Sidney
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Re: Elevons and Elevator

Post by Dane McGee »

I have experience with both and although you may give it a try, I don't think it will give you the desired result of tighter turns on the Axe.
A Flying wing when set up properly will almost always out turn any conventional airframe. There are exceptions though.

Tight turning is all about wingloading and keeping the wing flying at a high angle of attack. I would try playing with the cg and insure the airframe is light as possible, or perhaps a different airfoil. I've seen conventional airframes that would turn with a wing but they usually had both light weight and a special airfoil.

.......Or you could join the party and fly a wing too :D
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Re: Elevons and Elevator

Post by wtsidney »

Was thinking the short coupled "Lethal Weapon" / "Battle Axe" was more flying wing than conventional air frame and would benifit from elevons.

These ships seem to be quite durable and the setup is pretty easy. I'm not going to the "Dark Side" with a flying wing yet.
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Re: Elevons and Elevator

Post by Dane McGee »

Bruce Blevins tried elevons on his SSC design which is similar to a Avenger at the Kansas event a month or two back. I think that by the end of the event, he had re-configured them all back to conventional tail setup.

Perhaps he can weigh in on the convo...........
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Re: Elevons and Elevator

Post by Dane McGee »

.....BTW, when are you gonna come up and hang with the north Texas crowd? We are going to Witchita Kansas first week of August.....you are more than welcome to make the trip with us.
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Re: Elevons and Elevator

Post by Quickdraw »

Are you using aileron reflex already? I tried mixing evelons ( I fly Avengers) and didn't like it, didn't help. I think it creates more drag. A flying stab would do you more good. It's difficult to out turn a flying wing that's set up right with a conventional airframe (but I try).
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Re: Elevons and Elevator

Post by wtsidney »

Got reflex dialed in - added enough to keep the elevator neutral and not have the nose drop when chopping power suddenly. Hadn't looked at how reflex effects turning. Will have to play with it.

Putting a flying stab on my twin rail bird could be fun. If I reduce the horizontal stab by 50% when converting it to a flying stab, do I need to enlarge the vertical stab?

Dane: Thanks, won't make it in August - too many other commitments. Been flying every two weeks, keeping the planes combat ready is taking a lot of time - but a whole lot of FUN! Sunday was the first time I did not come home with pieces :D
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Re: Elevons and Elevator

Post by EK »

You shouldn't need to change the Vstab. Size(area) needed is a function of the distance between the wing and tail. Longer tail requires less Vstab area. Most of the combat birds are quite short coupled so more area is required than on a normal rc acro bird. Hang a couple streamers on one of the tips and fly it around. You'll lose quite a bit of performance but don't want it snap with every elevator input. If you're not happy, add more area to the Vstab or just angle it aft more (puts it's center of area is farther aft).
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Re: Elevons and Elevator

Post by Bruce B »

Hey Bill. I have tried about everything and these guys are right, not many conventional planes will turn with a flying wing. The most important thing is to just find a design you like and stick with it.it's great to experiment but just make one change at a time so you know what to blame when something doesn't work.
As far as sizing of the elevator,in my experiance it only needs to be big enough to stall the wing and that doesn't really take a lot. Any more is just drag and slows the plane in a turn. A full flying stab is better than a conventional elevator in my opinion, but the pivot has to be tight and slop free.
Don't be afraid to try new ideas. Most great things come from people that think outside the box
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Re: Elevons and Elevator

Post by wtsidney »

Thanks Bruce - flew 4 rounds yesterday, with no destruction - it is GREAT going home with what I brought. Was able to keep out of the way of the flying wing and chase down an Avenger for a kill with my twin rail, Lethal Weapon.

Will modify one ship to have dual ailerons with flaperons on it - want be able to adjust reflex from the transmitter and move the alieron servo away from the rubber bands.

Still toying with the idea of a flying stab.

Having a GREAT TIME! Sure beats flying laps at the feild with a sport plane on Sunday's.
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Re: Elevons and Elevator

Post by Bruce B »

Awesome Bill. Hope to see you at a contest sometime soon. Keep us posted on how it works
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Re: Elevons and Elevator

Post by ZenManiac »

Quickdraw wrote:Are you using aileron reflex already? I tried mixing evelons ( I fly Avengers) and didn't like it, didn't help. I think it creates more drag. A flying stab would do you more good. It's difficult to out turn a flying wing that's set up right with a conventional airframe (but I try).
IMHO, I don't think you want aileron/elevon reflex mixed with up-elevator -- what could help is mixing camber with up elevator. This is typically used on 3D planes, and is called 'snap flaps'. The camber creates lift in the wing while the tail is being pushed down, essentially creating a pivot point in the fuze. In 3D planes, it lets you square-cornered loops and gives a whole lot more authority in turns.

However, most 3D planes have longer fuzes than our combat planes, giving a better fulcrum effect of the snap flaps. I don't know how much it will help our short-coupled planes.

-= Dave
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Re: Elevons and Elevator

Post by Bruce B »

I agree that the short coupled nature of a combat plane probably won't see much if any benefit from doing this. I'd say a lightweight airframe that's built straight is more important than getting the tightest turn radius possible. I try to be conservative with the setup because I don't want a real snappy plane after I get a streamer way out on the wing. If your plane is already on the edge of a stall in the turns, a streamer in the wrong place can turn it into a handfull in a hurry.
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Re: Elevons and Elevator

Post by Blue Note »

IMHO...Flying stabs are a nice upgrade to conventional elevators/horizontal stabs allowing sharper and more precise control with less weight. A balanced stabulator also places less stress on the servo and is a smaller target during collisions. It also allows fine tuning for incidence issues to be performed very easily on the radio. I prefer symmetrical wing airfoils with a 0-0-0 setup approach, so with the optimal CG the reflex factor tends to be much less than on semi-symmetrical airfoils, thus less drag. I absolutely agree that the proper CG, typically as aft as you maintain comfortable control, will increase your maneuverability more than anything, but at the expense of stability. I feel each wing planform/airfoil combination has only one optimal CG and preferences for stability or responsiveness cause one to deviate from that point. The aft moving CG from fuel consumption and the anticipation of attached ribbons ( a lot of attached ribbons :lol: ) influence my setup, but I find that the ribbon influence does not really affect the CG as much as tip stall and snapping, which I address with airfoil and planform. Any given plane can only be "improved" to a certain point before more fundamental changes need to be made. Also, the success of mixing elevons with the elevator depends in part on how well the aileron deflection imparts an influence on the wing alpha and at what point that it induces drag. Even in cases where the turbulence from the ailerons/elevons is displaced beyond the lateral boundary of the elevator/stabulator to keep it "clean", the end result tends to be a tight, mushy turn with a notable decrease in forward momentum once controls are returned to neutral. Some of this is compounded by the short coupling of the airframes used in combat, but largely to the CG and airfoil choice, not to mention our power to weight ratios which can make speed recovery slow after tight turns with heavy stalling. As alluded to in previous posts, research of the proper setup would best be found in the pattern and control line arena, where it is used often and successfully, but typically with much higher thrust levels and/or throttle control. I have not found the elevon/elevator mixing setup to produce the desired results so far, but your results may vary. It certainly is beneficial to build as light as you can as far as flight performance is concerned, no matter what your setup.

I figure if you really want to be able to keep up with the flying wings in a turning war, you might as well be flying a wing yourself. If you desire a little more "hands off" stability to scan the skies and look for targets, a more conventional plane design may be more suited to you flying style. Even though my planes are extremely maneuverable, I notice the contest leaders usually winning with strategy more than reflexes. Some of the best rounds I have seen are with people flying "sick" planes that you wouldn't even consider to be competitive during launch. Knowing what you and your plane can do will be your biggest advantage, be it speed, turning radius, snapping tendencies, stalling characteristics, etc. Also, being aware of your competitors planes flying traits and characteristics can help quite a bit. All planes and pilots have weaknesses that can be exploited. FWIW.
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Re: Elevons and Elevator

Post by wtsidney »

Thanks for the comments and insight. I do enjoy scanning the skies for targets with the "hands off" stability of my current setup. :D

Had been thinking of adding dual ailerons - but that adds cost, complexity and weight. It would be nice to move the servo away from the rubber bands, and being able to adjust reflex from the radio. Really wanted to justify the dual aileron setup, and thought mixing reflex into the elevator, would be a benefit during normal flight and turns. Hadn't thought about drag, that wouldn't be good in tight turns. Will have to experiment with C.G. and lightening the airframe to see how handling is affected. There is something to be said for keeping it simple, with a single servo on the wing.

I did replace my standard hitec servos with fast Metal Gear servos and like it!

Will add a flying stab to the twin rail, Lethal Weapon I'm flying. Less drag / Less weight and smaller target are worth doing. Just need to work out the conversion details.

I'm still amazed with how reflex effected the flight characteristics and handling of these planes. And being able to fine tune the reflex to set the elevator to neutral. Hadn't played with reflex before combat.
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