Hi guys, I'm looking at a new design for a sport jet which I'd like to keep as simple as possible, preferably keeping the wings free of servos. Due to the short span (900mm) and somewhat axi-symmetrical nature of the design, I think I can get away without ailerons and use tailerons. However, there isn't much room back there for the all flying stab bearings and linkage (due to the exhaust duct) so I was wondering if ailevators would work OK. I've never considered using elevators as ailerons for roll control before, but the thought struck me that if the elevators are powerful enough to control it in pitch, they should also be powerful enough to control it in roll due to the short span and low inertia about the roll axis. One thing about the design, though, is the delta wing may need flaps in order to keep the angle of attack of the fuselage low enough for smooth landings, or at least to avoid stricking the underside of the rear fuselage on landing. Adding flaps which cover, say 2/3 of the span then lends the opportunity to use them as flaperons, however I wonder about the wash onto the stab at high angles of attack. This would be similar to an F16, I guess - has anyone used flaperons on an F16? Thanks!

Stumax, I havn't used just the elevator portion as tailerons, but this one used all flying stabs as tailerons, which are very powerful in roll.
Bob

Stumax,

Most of the Jepe-USA.com composite jets fly on tailerons The [link=http://www.ductedfans.com/Pyranha_EDF_fast_jet_Ductedfans.com_Jepe_USA.html]Pyranha 480[/link] and the [link=http://www.ductedfans.com/Jepe_F_16_Jepe_USA_.com.html]F-16 [/link] are 16 to 200 and just tailerons, I have even taped the flaps and ailerons on the [link=http://www.ductedfans.com/EL_Bandito_ductedfan.html]El bandito [/link] just tailerons and rudder worked well a bit less weight trying to break 209 Mph.

Your jet looks fast, sort of the F-104 meets the El Bandito. Keep going looking forwar to seeing it rip up the sky.

Morris
www.Ductedfans.com

Yes, on a SM 1/8 F16.. guess that I tried all the configurations possible on this plane and what I liked most
was flaperons (just 15 degrees for landing) and conventional elevator. Worth to mention that in all those tries the F-16 flew fine with just tailerons and aleirons with tailerons too.

Btw, congrats on your design.. it looks promising. You may also think in reducing the air intake area.. the plane will be much faster and still have plenty of air for the turbine and refrigeration.


Enrique

Stumax,

Not sure I correctly understand your terminology or exaxtly what you are contemplating.

Tailerons are pitch and roll control with the horizontal stabs. Works well with some designs but roll control may be ineffective at lower speeds...at least that was my experience with a Yellow F-18 single, ducted fan.

Ailevators (or elvons) are applicable to delta wing aircraft and single control surfaces on each wing act as elevators and ailerons. These work just fine on deltas but don't work well on conventional aircraft because the pitch moment ("elevator") is too close to the cg. Your design has a delta wing planform but is not a "delta" because of the conventional stab arrangement. I don't think ailevators would do well.

Flaperons are simply when the ailerons are drooped to provide some "flap" effect. My limited experience with them is they tend to be touchy and not particularly effective.

The best control solution is stabs, ailerons and flaps but if you are trying to eliminate controls on either the wing or tail, I would go with tailerons.

Craig

PS: I also like the look of your design. From the leading edge of the wings back it reminds me of a Mig-21.

At subsonic speeds there is almost no advantage of using tailerons instead of ailevators.
Ailevators may work very well for a low aspect ratio wing design such as yours.
I did try using ailevators on a SIG Somethin Extra simply because I used one servo per elevator half and wanted to to see if there were any gains from using tailevators when torque rolling. As it turned out roll control when using tailerons only was very sluggish in all flight modes. I attribute this to the fact that the rolling torque produced by the tailevators in this case is much smaller than that of the ailerons on the wing simply because there was a big difference in lever arm beween the ailerons and the tailevators.

As Enrique said, in my Skymaster F-16 1/8, I use flapperons and ailevators. More than 15 ° on flapperons, the model start to fly weird and at low speed with flapperons, ailerons become sluggish so I use ailevators when at low speed. (I have a mix when flapperons or gear down, ailevators are activated).

Hope this help<br type="_moz" />

Erbroens, Guillo, 

On the F16,  with flaps down, how was the plane slow speed behavior with conventional elevators vs. a Vtail/taileron configuration?

Thanks 

Rob

My impression on the F-16 was that flaps aren´t needed to slow down the plane for landing.. it already drags out nicely by itself so the flaperons where set for giving extra lift but no drag at all. (15 degrees). The nicest, shortest and easiest landings where done this way.

About the difference on the slow speed behavior it seemed to me that the flaperons gave more solid roll control, regardless of using conventional elevators or tailerons. The choice of conventional elevator setup was made as it seemed to react better at higher speeds.

I concur with much of the above, flaperon and taileron on F-16 is just so much more fun.

Thanks for the feedback and kind words about my new design, guys. It looks like flaperons and elevators will be the way to go. The time and effort to put two servos in the wings and hinge the flaperons will be offset by the simplicity of having elevators instead of a flying tail and struggling to fit it all into such a tight space. Good to know that flaps on F16's are OK, although I get the feeling that too much flap movement is going to cause problems both with wake onto the tailplane as well as making the roll authority a bit mushy. BTW, this one's for 90-100mm EDF but it would be possible to fit a Wren44 size turbine. I'm also doing a larger winged version, swept wings with a tailplane mounted up the fin similar to a Hunter for 100-110mm EDF, this version would suit a 12lb turbine. Thanks again, guys.

I agree with Enrique but as I said in post No. 7, at low speeds I prefer to use ailerons assisted by tailerons (known as Ailvators). I think that this is related with the total flying weight. Mine is too heavy (30 lbs wet prior to take off)