rffs fliterbee?

[Fwilly]

I was thinking of trying to make a flitter bee for the rffs. I haven't tryed the full size yet and I was wondering if it used reflex in the elevons like the Ifo. Do all flying wings have reflex in their elevons? I am going to make it with about a 1/2 foot of wing area to give it about 2oz per square foot of wing loading does this sound like a good size for the rffs?
thanks

[pease1]

I just finished an RFFS-100 IFO. I'll tell you this, you're not going to get a flying wing with actuators to be acrobatic. My IFO sustains controlled flight, but it's not as good of a flyer as the Little Skeeter or Gordon's Kolibri style plane.

You might have a little more luck with the Flitter-B because it has an airfoil, but I'd have to reccomend against an elevon configuration after doing it myself.

I've already started working on the new airframe for my RFFS-100, a 1/24th scale RAF Se5a.

Rudder/Elevator planes just seem to work best with this system.

[Fwilly]

thanks I think I'll go with something like the pixel but resembling a pitts special or ultimate. You saved a good amount of time since I was going to build up the wing out of balsa. Maybe I'll try a flying wing after I have more experience with actuators.

[Dave Robelen]

Hi FWilly,
My little 13.5" span delta with the RFFS-100 is reasonably acrobatic. Loops, rolls, etc. The elevons are fully balanced and reflexed until the plane was in trim with neutral stick (about 3 deg. in my case). It seems to deepend on the design. My delta is fairly fast in cruise with a KP-00 style motor on 3 cells, while the mini IFO is likely more draggy.
Regards, Dave

[Fwilly]

so if I keep the drag down and make it slightly smaller it might be aerobatic?

[Dave Robelen]

Hi Fwilly,
Making the bitrd smaller would probably help. In the case of the IFO, the drag is most likely the result of a combination of several things. First, a flat plate is not an efficient airfoil, and second the very short wingspan relative to the chord results in large draggy vortices around the edge of the wing. From my experience watching the IFO style machine fly, it is especially well suited to tight manuevers that involve both inside and inverted lift. It simply needs a bunch of thrust to do that stuff.
TRhe delta I mentioned is a completely different type of design. The taper helps improve the eficiency of the wing, and using a flat bottom airfoil helps reduce drag still more in upright flight and positive "G" manuevers. Basically it flies considerably faster than the IFO style machine and is better suited to more space than a living room.
Cheers, Dave

[Fwilly]

thanks for the advice

one sheet of 1/32 inch balsa is enough to try lots of different designs for this small of a system:D. If a design fails your not out much time or money.

[Fwilly]

just cut the ribs and framed up the wing. I decided on a 10 3/4" wingspan and a 4 inch chord without the elevons. does that sound small enough to be succesfull? I used a flat bottom airfoil that is relatively thin compared to the full sized flitter B in hopes of cutting down on drag. If it dosen't fly the way I want I can always add a tail and a third actuator and make it aileron elvator controlled

[Dave Robelen]

Hi Fwilly,
Is that a constant 4" chord? If so that would work out to about 40-41 sq. in. which may be a bit on the small side. For monoplanes the most succesful seem to have about 60 sq. in. on average. Usually a flying wing needs a bit more area than a model with a tail because the CG will be so much farther forward.
Good lick, Dave

[Fwilly]

the elevons should add the needed wing area. how big of a control surface can the actuators move if they are perfectly aerodynamically balanced? I plan on using a peice of wire conected to the outer edge of the elevon going out forward of the hinge line with a piece of wood on it which I will move forward and backward to get the best possible aerodynamic balance.

[Dave Robelen]

Hi Fwilly,
There are two types of balancing controls. Aerodynamic balancing refers to having a portion of the control area ahead of the hinge line. In the case of this type of model I shoot for 30% of the control area to be balance area. The other type of balancing is static balancing. This is where you put a small weight on the front of the aerodynamic balance until it just hangs level. I have not found the maximum area for the controls. With a 3-cell battery (the actuator power is linked to the battery voltage) I have had good success with elevons that were 6" long and had 3/4" behind the hingeline.
Cheers, Dave Robelen

[Fwilly]

thanks
mine will be between 5"x3/4" and 5"x1" I will also be using 3 cells so it sounds like It will work