Flying the Red Butterfly, Vertical Take Offs and assisted vertical descends

On 2S500mah, it flies ok with two antennae, sensitive with one antenna, not acceptable with no antenna. It clearly needs more voltage and I think batteries with higher discharge rate then 15C is desirable. As it is, there is not enough power near end of flight and there are residual current in the batteries.

On 3S800mah, it flies great with one antennae, sensitive with no antenna and plenty of thrust. There is so much thrust (near the beginning of each flight), the model can take off vertically from the ground.

I couldn't manage hanging off the prop for hovering and then to attempt vertical tailfirst landing. With a strong headwind which is greater then the flying air speed, the model can appear to retreat tail first and usually at this slower air speed, the model can appear to descend vertically, although in a 'flying' posture.

The Red Butterfly flies

The red butterfly flies much better after modification.
The photo above shows the two modifications I tried.
I have the Augmenter ring and the two feelers/eyes.

The two eyes were taped onto the wing. Round balls were glued to the ends of the two carbon fibre strips and 5gm lead weight taped onto the carbon fibre strips. It transforms the flight from fluttery to a proper controlled flight. With the CG brought forward, it became controllable.

The Augmenter was tried with 3S800mah motor. It is actually a detractor. The speed envelope reduced, it seems to help a bit on high Alpha flight, but only one flight was made with the Augmenter and it was subsequently removed.

With the Augmenter removed and the eyes fitted, I flew it with 2S500mah. Only managed to fly less than 4 minutes on each battery. Probably because I had fitted a cut-down 10x4.7 prop, and unbalanced at that. I did it because the 7x4 prop broke when I crashed the model.  

Both modifications look cool. The yellow eyes are a keeper, but the augmenter ring not so, maybe I will keep it for 'special occasion', but only after I sprayed it silver front and red back.

The other modification since then is the application of yellow vinyl to the top of the wings. This helps visually. On a bright day, the yellow shows through to the underside, but it is no issue really, as the visual aid is for the moments when you can't see well, which doesn't happen on a bright day.

STOL/VTOL Single Motor

A single electric motor, 10x4.7 prop, 45degrees canted upwards to provide forward and upwards thrust, just behind the CG, ducted with controllable vanes at the bottom and narrowing to a vane-linked elevator and huge ailerons and rudder for the other two axis around the CG.

The duct to be made big enough, enough void within to even out the swirls and pulsation of the prop fan. One entry to the prop fan, two main exits with one at the vaned area and one at the rear. Net area of vaned area and rear exit should be lesser than the entry. There shall be sliding plates at the diagonal corners of the duct below the prop fan to provide torque correction force. Instead of linking it to the aileron servo, we can leave it manual, adjusted after flight testing.

The bottom vanes shall be at 45 degrees pointing rearwards, but can be closed. With the vanes closed, the model is to fly like a normal powered plane with the pair of wings providing lift and countered by the downward force of the elevator. With the vanes opened, the elevator shall move upwards to push the tail down so as to compensate the nose droping moment.

The pair of low aspect ratio wings shall be located relative to the CG, to glide when the elevator is at neutral (vanes closed condition). There shall be dihedral for stability as the ailerons are omitted for the first test model. The wings to be top mounted, just below the lower of the prop fan disc.

The fuselage is a longish pod to a rectangular box. A large fin is mounted on top of the box, and the rudder extends to the box. The elevator is cut out from the bottom of the box.

Model to be 3 Channel. Throttle, Elevator, Rudder. 2210 motor, 3S1300mah battery, 10x4.7 propellor, 2 servos, 30A ESC, Hitec receiver.

Yellow Butterfly, Red Butterfly, Red Savoia S13

My Flying Flea, aka Pou du Ciel, could only crash and is converted to the Yellow Butterfly by the additional of thin oval discs at the rear wing. It still didn't fly. On the last test, it flew up to 6-10m high and dived straight down. Maybe I should return the 2S500mah battery to the battery compartment and make 3-5degrees of incidence on the front wing. Alternately, I am considering modifying it to have elevators at the rear wing.

The depron quick build is the Red Butterfly, it flew, barely.
It has the flying characteristics of a butterfly, Muhamad Ali's word: 'float like a butterfly', except that I have a hard time doing the flight corrections. The 3S800mah battery is already placed immediately behind the firewall and it is still tail heavy.

Instead of fixing nose weight, or ripping the elevon/rudder servos and mount them forward and replacing the pushrods, I shall add some interesting structure ahead of the CG. It should both be interesting and also serve as nose weight.

Two ideas, the Augmenter and the Feeler.

The Augmenter
Cut out of McDonald's salad cover, this circular cowl is gracefully curved and let us call it the Augmenter!

So called because, it shall:

1. increase the thrust from the propeller, 
2. render the model stall proof because at extreme angle, it will still provide lift at the nose, enabling the model to hold higher AoA,
3. enable the model to land vertically on its tail,
4. enables the model to have slower and more constant airspeed in climbs and dives,
5. looks cool because relative to the 7" propeller, it is so huge (I think I shall spray it silver).

The weight increase will be very slight, only a few grammes.

Will it work? I don't know, even if it is detrimental to the performance or if it makes the model more difficult to fly, it is interesting.

The Feeler
How about some flexible wire/rods stuck on to the nose, so it looks like the pair of feelers of a butterfly?
I could add small plastic balls at the extreme end, for safety (hahhahah) reasons, both visually and practically.
Wow, am I a show-off?
Don't care, so long as I am having fun.

Will it work? There might be complications, but having long feelers infront of the propeller disc must be good at least for the CG as it presents long moment arms so I can use the least weight to bring forward the CG.

With all these ongoing projects And yet, I'm thinking of doing a quick build of a red-white Savoia S13.
Go Outerzone, there's a peanut plan.
Let's see, the mods I would make:

• sheet balsa everything, fuselage, tail, wings, nacelle
• engine nacelle integral with the top wing
• engine nacelle to house the aileron servo (only the top wing has ailerons), esc and motor (to use the Emax motor currently in the Red Butterfly)
• carbon fibre strips as cabane struts with nylon fishing line riggings (the 0.33mm thick type)
• Both upper and lower wings, with the cabane struts, engine nacelle, demountable in a single unit from the fuselage boat, the esc lead and servo lead is to be connected before fixing the single unit (dowel and screws or rubber banded?) 
• right under the lower wing, in the fuselage (the boat/pontoon), will be the elevator and rudder servos.
• Forward, in the nose will be the receiver and 3S battery
• The top of the nose, until the cockpit, shall be removable, this means nose to rear of the trailing edge of the lower wing is open for inspection, modification and reinforcement
• elevator and rudder pushrods shall be the 0.8mm wire running in nylon tubing

How difficult can this be to build, fly and maintain? If I get sick of biplane flying, I can just do up a wing with motor pylon mounted and fly it as a 3 channel monoplane model.

Why a flying boat? Well, a flying boat is supposed to ROW (Rise-Off-Water), so there's no wheels around, and maybe one day I will fit a motor powerful enough to be able to take off grass! ROG, Rise-Off-Ground or more appropriately Rise_Off-Grass!

Red Butterfly

Red Butterfly

Name derived from its flying wing planform and huge elevons which, together, looks a bit like the wings of a butterfly. Red, because red packing tape has been used.

The idea is to have a simple depron flying wing, huge elevons and rudder, deep fuselage profile for 3D type of flying.

Depron is weak, so carbon fibre tube has been used on the leading edges of the wing and fuselage, and carbon fibre strip on the hingeline of the wings. Both tube and strip were sized very close to the 5mm depron.

Flying on 2 cells lipo (2S500mah) was attempted, it flew like a kite, meaning it can go up, but extremely difficult to fly, the wind takes over and flying is more like making constant corrections to the model, sometimes successful, sometimes not, and never consistent.

Then I placed a used 2 cells lipo as additional nose weight and it flew well enough.

So on the next trip, I used 3S800mah, more controllable but plenty of quirks. I find it can fly, but the CG is too far back. When the model was inverted, instead of diving towards the ground, it flew upwards.

A control horn broke from the model, curtailing further flying, but what I would do perhaps, is to install the 3 servos right behind the leading edge to bring the CG forward slightly, possibly devise somthing to prevent the 3S800mah battery from falling out (happened twice, model floated down in a level plane due to the rearward CG).

To improve visibility, I should add some color trim on the top, perhaps the yellow vinyl sticker that I bought.
To increase interest, I may use McDonald's plastic cover for the salad as a huge cowling, who knows, maybe it allows the model to 'parachute' vertically tail first?

Repairs and riggings

With so many crashes and repairs needed to the Flying Flea/ Yellow Butterfly, I think I have become more adept with repairs and riggings.

 

I have had 2 broken propellers and a few other ailments:

• the 0.65mm nylon rigging line does not bend sharply when needed; I replaced with white sewing thread, although now I replaced the sewing thread with 0.33mm nylon fishing line to address the other issue of snapping;
• rigging lines pulled out of the attachment lugs; I replaced the broken attachment lugs or glued on a small washer; and
• the attachment lugs themselves pulled out from the wings; I glued the lugs and clamped them to the wings until the glue is cured; the pvc wing pivot broke; I replaced that with
• the wing pivot fabricated from PVC cover sheet sheared off; I used another plastic horn to be the wing pivot and superglued in placed. Similarly when the first plastic horn snapped, I employed the same except that I superglued it temporarily in placed and then epoxied the horn and struts;
• the rigging lines snapped; I tried joining with additional piece of thread, forming loops at the free ends and using that to attach the new thread and finally using 0.33mm nylon fishing line;
• the tension of the rigging lines collapsed the cabane struts; I had to re-rig the whole model, good thing too as the previous horn was displaced before the glue cured, leaving me with a lower forewing.

After so many re-riggings, I employed push rods for the wing because previously, when I was using 0.65mm nylon line or sewing thread as pull lines, I had issues with adjustability, and the rubber band to make the forewing pitch downwards places additional strain on the servo and linkages, the servo hummed.

 

Using push rods has additional benefits. Because the wing lugs are in board, it makes sense to install the pushrods first and then proceed with the rigging. Previously I had installed the primary roll rigging, then the secondary lateral rigging and then the incidence pull lines. It is difficult to install the inner pull lines as space was so limited and the lines restricted my fingers this way and that.

 

With the inner pushrods secured, they held the wing at the approximate incidence and I proceeded with the rigging. The first rigging is the roll rigging, and then the lateral rigging. All together, only six pieces of 3mm aluminium tubing, each approximately 3-4mm long are used. 2 for the 2 ends of the roll rigging line, 2 for the 2 ends of the lateral rigging line and 2 at the outboard pivot points where all four lines converged, so I can lock the roll and lateral lines inplaced in one go.

And if I shall have a chance to do up the main wing's actuating mechanism again, I shall fit the arm through a slot cut in the aluminium tubing because the arm now is worked loose and has slop. Good enough for pulling I guess, but not for pushing and would never be good enough if I put tail elevators.

 

Reincarnation of the Flying Flea into the Yellow Butterfly, although it still crashed

The problems with my flying flea so far appears to be: the short range of CG (usually it appears nose heavy but as this is complicated by the AOA of the forewing, it is kind of difficult to assess until it is flying), the securing of the 2S500mah battery (Mr. Grayson, the grey foam pilot couldn't put his back to the battery tight or long enough), the constant loosening of the wing actuating horn (so I have slop) and the general fragileness of the rigging lines which are a pain to re-install.

The two sets of forewing rigging lines of sewing thread has snapped. I the forewing rigging thread with 0.33mm fishing line (40 cents investment) because the sewing thread snapped frequently.

I tried to tackle is the short permissible-range of CG. I would prefer to distance the wings a bit more, to give it more moment arm, but there is not much chance with such a short fuselage. Instead, I glued on two sticks of tail, fabricated from carbon fibre rods and two oval discs of clear pvc sheet (book cover material) joined at the rear with a flat carbon fibre strip. This gives the planform an appearance closer to that of a butterfly. And since the model is sprayed yellow, hence, Yellow Butterfly. So it is not a flying flea then, but, let's at least get it flying.

I found I had to add a 5gm weight to the rear of this double tail (or third pair of wings) when the battery is in the cockpit if the model is to balance at the calculated CG point. So I made a hatch at the bottom of the fuselage, just behind the former of the cockpit and placed the battery there and removed the 5gm of leadweight. Seems a bit tail heavy but I like to try that because many taxi runs ended up nose-over, maybe the rear wing is lifting too much.

With the 0.33mm nylon line forewing rigging, slightly collapsed cabane (resulting in a lower forewing), transparent pair of third wings, and battery behind the cockpit backrest former, the model lifted off the ground wallowed in the brief seconds when it is in the air before snapping inverted and dived onto the ground. Clearly, a sign of rearward CG.

The model is broken again. The front cabane struts broke from the firewall, the starboard horn teared (including tissue) away from the foam wing.

Every crash is a re-build opportunity for improvement.

But maybe I will lay off Yellow Butterfly for a while and do up the RED 3D Butterfly (inspired by the Yellow Butterfly but with single depron foam elevon wing, deep fuselage and rudder). Another possible model I might make before I continue with the Yellow Butterfly is to do up a tandem wing flyer.

Concept for tandem winged flier
Take two chuck glider wings (18" span, 1/4" x 4" balsa, polyhedral for the front and dihedral for the rear), separated by a fuselage with at least 6" between the TE of the forewing and the LE of the rear wing, pair of elevons at the rear wing, with a rudder set 6" away from the TE of the rear elevon. Die, die must fly.