FT Edge 1080

[Pieliker96]

540 * 2 = 1080.

This is an idea I've had kicking around ever since seeing the Yak-110 at OSHKOSH - two Yak-55's transformed into a single twin-fuselage craft. The goal is to basically do the same thing with Andres' Edge: join two of them together at the wing and (maybe) sling a EDF underneath. This should be relatively simple, involving no more than a custom wing and elevator - everything else will be completely stock. I've not done any really detailed planning (ex. weight, battery requirements, wing loading, etc.) beyond just entertaining the concept. I'm interested to see how it'll fly.

 

[Hyper46havoc]

I really like the idea of a twin fuse plane

 

[CustomRCMods]

👍👍👍 I’ll be watching this

 

[Air-headed Aviator]

Theres something about these whacky twin boom projects that are just awesome

 

[Pieliker96]

I've done a decent preliminary estimation of the performance of this aircraft.

Expected maximum AUW is 1.7kg, or 2kg with the EDF (Stock is ~850g). That's with two 1800mah 4s batteries. I would go with more capacity given the high current draw of the motors & edf, but I don't want to make this bird too heavy - I'll have anywhere from 30% (no EDF) to 55% (With EDF) more mass per unit wing area than the stock plane.

This translates into a ~15-25% increase in stall speed over baseline given that v ∝ √ (mass/wing area) - not insignificant, but very manageable with the already low stall speed (or at least maneuvering speed), propwash over the massive control surfaces, and high thrust-to-weight ratio that the craft has.

I'll be using counter-rotating propellers to eliminate torque, as well as differential thrust, just for kicks. I'm debating whether to have the fan on all the time while in-flight. I think I could have three modes, all on a switch:

-Off (For battery saving)
-Tied to throttle with a ~50% dual rate (For general flying/maneuvering)
-Directly tied to throttle (For high speed passes)

which would allow me to potentially extend battery life a bit by disabling the less-efficient EDF when it is not needed.

I'm playing with the idea of making the EDF removable by means of a pod that would slot into the wing and horizontal stabilizer. That would allow me to have the best of both worlds in terms of raw thrust versus aerobatic performance and flight time, but would add extra complexity and potentially wear out over time.

 

[Grifflyer]

This is going to be really cool, good luck!!

 

[BrickRedRock]

That sounds real difficult in figuring out how to balance the power between the two systems. Not an expert but I would think that too much thrust from the EDF will cause the propellers to drag and waste power and the opposite on the other end. Would be interested in seeing the results.

 

[Pieliker96]

...EDF will cause the propellers to drag and waste power and the opposite on the other end.

This is a great point which I've been thinking about for a while. I guess it's time to do some calculations:

The 9x4.7 propellers I'm planning to use, along with 1100kv motors on 4s (Max 16.8v), give a maximum theoretical pitch speed of about 80MPH (Plenty fast for me). As speed increases to this magnitude (assuming it is attainable), most of the thrust will be coming from the higher-pitched EDF with the propellers producing negligible amounts of thrust (and therefore little drag).

Increasing the pitch to a 9x6 yeilds a theoretical maximum pitch speed of 105MPH. Realistically it'll be a lot less, taking into account drag, voltage droop under load, and the fact that battery voltage decreases throughout the flight. I'll also probably stick to the 9x4.7's for the snappier throttle response and lower amp draw.

Either way, this seems to be a fantastic top speed before the props become detrimental. This plane is designed and built for 3D flight, which is arguably more fun when "low & slow". I'm not really concerned about the drag caused by the fan (even when stopped) because it's quite a small area when compared to the cowling on the plane itself. Sure, it'll be inefficient. But if I wanted efficiency I wouldn't be strapping an EDF to it anyways.

 

[Pieliker96]

Made some progress on the right-side fuselage. The double-wide elevator was too large to fit on a single sheet of foam so I just removed the counterbalance from one side. I figure I can basically make both fuselages sans the wing, tape them together at the H-stab, then figure out the wing from there.

 

[Pieliker96]

And then there were two!



An advantage of not using the waterproof foam is being able to simply make the canopy out of black foam. One disadvantage (from buying the laser-cut kits) is that the more complex geometry is more prone to error / small misalignments.



I also made a little tail wheel wire holder with some sheet balsa. It's sort of grafted under the skin of the foam to give a cleaner look.
The tail wheel is also protected by the little ventral skid. Not that I intend to fly off of grass, but it couldn't hurt.



Custom motor mounts without thrust angle for counterrotation purposes.

 

[Pieliker96]

We have a wing!



Total current airframe weight is 680g.

 

[Gazoo]

I like where this is going.
Looks so clean.

 

[Pieliker96]

Wiring is mostly done. Cramming everything through the spar (5 servo wires and two 14 guage leads) was a bit of a chore.

I think I'll end up maidening the plane without the EDF.

I'll post updates as parts arrive.

 

[Pieliker96]

the rest of the parts arrived this morning. I got the motors installed, cowlings on, landing gear built (although they still require some tweaking), and control linkages done. I ended up going with some 10x4.5 props btw.

One of the ESCs died for some reason. There was no magic smoke, and the resistance on the motor side and battery side is the same as the working ESC. I've ordered a replacement.

Of course, that doesn't stop me from having some fun!

It looks nice with the 2" spinners. I'll have to come up with a cool paint scheme...

 

[Pieliker96]

So I got the new ESC today and had the same problem. Turns out the method I used to attach the bullets is not reliable.

The 3.5mm bullet connectors were a snug fit over the ESC's motor tabs. It was a pretty slick looking way to attach them, but evidently they don't make contact on the ESC pads some of the time. The old ESC and the new ESC both work. I just ended up soldering wires onto the tabs instead.



It seems to taxi pretty well, especially with differential thrust.

Final All-up Weight without EDF is 1.84kg, which is just a tad bit over my expected maximum of 1.7kg. Considering that I used heavier batteries and didn't account for the spinners (which account for 120g combined) I was pretty darn close.

Time for a maiden flight!

 

[Chuppster]

So I got the new ESC today and had the same problem. Turns out the method I used to attach the bullets is not reliable.

The 3.5mm bullet connectors were a snug fit over the ESC's motor tabs. It was a pretty slick looking way to attach them, but evidently they don't make contact on the ESC pads some of the time. The old ESC and the new ESC both work. I just ended up soldering wires onto the tabs instead.

View attachment 133844

It seems to taxi pretty well, especially with differential thrust.

Final All-up Weight without EDF is 1.84kg, which is just a tad bit over my expected maximum of 1.7kg. Considering that I used heavier batteries and didn't account for the spinners (which account for 120g combined) I was pretty darn close.

Time for a maiden flight!

I'm excited to see it!

 

[Pieliker96]

I had a successful (?) maiden flight today. The plane flew beautifully, but I nearly folded the wings within a minute in the air.

One contributing factor to this was me cutting into the leading edge so I could move the batteries farther back to get the CG proper (pic below). I also expected the stock spar to hold a plane nearly twice the stock weight with a greater span, which it evidently couldn't.

I'll build another wing with a proper stronk & skookum spar, then try for a re-maiden flight.
Then when I get the EDF I can go do a re-re-maiden!

 

[JTarmstr]

Nice save!

 

[Pieliker96]

I built a better wing yesterday. The spar is layered 3/8" x 36" square poplar stock glued with CA. Pics below.



Then I went out and flew it. Man, does this thing fly well. I found that it was basically impossible to stall the wing, even with full back elevator. This means I'm nose-heavy from the optimal CG, but it's so maneuverable that I don't really care. As I learn more advanced aerobatic flying, I'm sure that I'll end up moving the CG back to make post-stall aerobatics possible. Having counter rotating props also means that it doesn't want to roll in high-alpha or at slow speeds, which feels incredible. It's like a regular Edge 540 but without all of the asymmetrical tendencies.

I got some video of the flight, but the SD card on my phone ran out of space. I got around 8 minutes of flight time (If I had to guess).

Now it's time to strap an EDF to it!

 

[Michael9865]

Congratulations!