Air-headed Aviator
Member
I've somehow been working on my own interpretation of an EDF RC plane for five years now. The development of my designs have coincided with my growth in understanding Aerodynamic theory. Lets go through memory lane.
The Last Bullfighter:
Eight times I've attempted to create a mixed propulsion aircraft combining an EDF with a propeller powertrain. I imagined that a lot of the disadvantages of EDFs could be covered by the advantages of a propeller, just like what was done for Early 1940s designs. However it was very hard integrating two different powertrains that needed very different things. Very few Bullfighters were ever flown and the ones that were simply couldn't be balanced to fly.
The Last Bullfighter:
Eight times I've attempted to create a mixed propulsion aircraft combining an EDF with a propeller powertrain. I imagined that a lot of the disadvantages of EDFs could be covered by the advantages of a propeller, just like what was done for Early 1940s designs. However it was very hard integrating two different powertrains that needed very different things. Very few Bullfighters were ever flown and the ones that were simply couldn't be balanced to fly.
Shortcut P.1:
Two airframes of the same design were created as a re-evaluation of what I assumed an ideal EDF design should be. I came across my first RC Design book, and developed the theory that because of how slow RC planes are (below Mach 0.70) that the best performance would come from straight wings, not swept. I created this design with the simplified goal of being fast, still believing in the power house of EDFs. The First airframe was an attempt at using a specific airfoil, however it was created wrong and could not fly. The second air frame used a more tradition Clark Y airfoil. Flew once on a very windy day, where it showed that it was terminally short coupled. On a calmer day it could not get into the air. I was using a 6S EDF on 4S and didn't have enough thrust with this un optimized inlet design.
Shortcut P.2:
The next design intended to solve the short coupled problems and power issues. I started analyzing the turbofan subsonic aircraft I get to work with at my job, and wanted to implement the ratios I've seen for inlet and thrust tube lengths. In addition I pulled a Yak-9 and put the EDF in the front. This allowed a tail distance more typical of an airplane. Along with a thinned fuselage this design should have flown, however I couldn't do things normal and tried to make a design that depended on spoilerons for roll control. I didn't understand spoilerons enough back then, so this design could not fly. The fuselage as well was very weak at the wing joint, so it broke easy. Thus I abandoned this design
Detour:
Around the same time of Shortcut, I got access to an Arrows Mig-29. Not confident in my ability to fly such a bird in my area, I thought the parts would find better use in a unique design. Detour was an attempt at a more conventional approach to an EDF with my ideas in mind that could be modified easily going forward. The EDFs were mounted now on pylons over the CG, and with these inlet and thrust tube lengths I surmised from multiple real world jets. Detour could have flown too, but I did not fly it. Where Shortcut 2 was too ambitious Detour was too safe. I worried I would settle for adequate. I never flew Detour, but it was a good design study to refine building techniques.
Swoosh Reprise P.1:
At this point in my journey, I wanted to combine the desire to use a straight wing, avoid a short coupled aircraft, have the "correct" inlet and thrust tube length, and create a high performance high capability aircraft. I recalled one of my past designs, the Swoosh - a twin boom pusher prop plane, and thought that would be a good layout to fulfill my goals. Reprise was an experimental design with an A-tail produced in 2024. The A-tail was intended to keep it out of the thrust blast, the design made use of joint aileron flapperons, and it used a 4S 64mm EDF. It had only flown once, and poorly. I tested gliders before the maiden, but they didn't reveal how little the aircraft could maneuver. It was a miracle that I didn't lose the aircraft in a river. In addition the aircraft was all too heavy, being lethargic in thrust as well.
Swoosh Reprise P.2:
We finally get to a success! A lot of things happened up to the development of Reprise P.2: I learned about Wing Cube Loading, I got the Model Aircraft Aerodynamics book from Martin Simmons, and I found more definitive information on tuning a Ducted Fan powertrain. With that knowledge, I reevaluated the approach of Reprise P.1 and pivoted. The main goals of P.2 was to lighten the design as much as possible, give it a conventional-ish tail, and provide it a WCL that matched the agility I wanted and stability I wanted. P.2 has a cruciform tail to avoid the Fan blast, and a low profile low slung fuselage to provide a clear pitot inlet for the fan instead of the bisected duct. P.2 was my first successful EDF design (kinda poetic, since back in 2015 the original Swoosh was also my first successful RC design). It was quiet stable and possessed a decent thrust-to-weight ratio. I flew it all summer 2024 and modified it in a variety of ways to test new ideas and developments. Reprise proved for me that the straight wing approach could improve the capabilities of an EDF design, being able to compare in speed to a lighter prop powered design and have 5.5 minute flight time. Most of the lessons with Reprise have gone forward to the next designs.
Antagonist P.1:
The next EDF design I attempted finally made use of the Arrows Mig components. Antagonist was intended to push the exploration of EDF designs further. Reprise was good, but I wasn't wowed by its capability, so I introduced more complex attributes to test. Antagonist made use of a proper low camber, tapering wing. Two 6S 64mm EDFs with pitot inlets. It had flaps, spoilerons, and an improved version of the conjoined rudder system which used one servo. Antagonist was surprising to maiden, cause it went with no incident and flew incredibly easy. At this point I had 5 active designs all using WCL strategies and new-to-me aerodynamic theory. Antagonist had by far the highest WCL, which would have suggested it would fly at a high stall speed and high throttle. However Antagonist was perhaps the easiest most gentle design to fly, and with the lowest stall speed! Its wing design provided qualities the other builds lacked with their constant thickness wings. Antagonist was fast and confidence inspiring, and my first successful application of spoilerons. These spoilerons were spring loaded, being activated by the ailerons when deflected. Over time I modified Antagonist too, adding fairings in a variety of ways to reduce drag, and eventually deleting the spoilerons for traditional ailerons to enhance the roll speed. I also began experimenting with a device I called the Thrust Body.
This device was a fairing for the EDF motor to help retain thrust lost by the cross section change. The thrust body returned as much as 15% of the thrust of an EDF.
Swoosh Reprise P.3
Antagonist has taught me a lot about EDF design, enough to encourage me to redesign Reprise for a third time. I wanted to address a variety of shortcomings with P.2: The inlet was compromised for packaging and did lose some performance and I also wanted to integrate the thrust body. I wanted to reduce the drag of P.2 for more efficiency. And I wanted to improve the powertrain cooling and potential balance of the design. For P.3 I adopted the shoulder wing layout of Antagonist, placing the EDF low to allow for a slimmer, sleeker tail plane. The EDF position was shifted to hopefully centralize the mass of the aircraft more tightly. A duct for the ESC was introduced, and the tail booms were thinned more than with P.2, now with noses to retain the strength of them. As of writing I've only flown it once, and so far still need to correct the CG. Still it reveals very good power-to-weight, climb, and speed.
Antagonist P.2
The latest EDF design so far is the second iteration of Antagonist. I recognized that due to the compromises for the best technical performance for the EDFs on board, Antagonist P.1 had a very large cross section. Another design of mine with less power (though still 75% of it) feels faster (prop driven), so P.2 was focused primarily on reducing drag. The wing itself was moved lower in plane to the central fuselage to eliminate the area of the wing box. tail booms were thinned to reduce their drag, and the wingspan was reduced. Traditional ailerons were used, along with a refined flap system. But in addition to that I've added a new experimental approach. The central Nacelle was given the cross section of a laminar flow body, 50% position of maximum thickness. I'm calling the approach a "speed tail" like that used on some high performance cars. A significant portion of an objects drag comes from how well it reintroduces the air it displaces back together, The sleek speed tail intends to cut down on the drag of at least the central fuselage. the EDF housings themselves are faired as smoothly as I can to the middle. Other than that some relatively minor changes were also down to the tail feathers: being shifted backward for better potential stability. The fuselage was widened for better access, and a NACA duct was introduced to improve powertrain cooling. Antagonist P.2 has yet to be maidened as of writing, but I intend to directly compare it to Antagonist P.1 to see if my changes have helped or harmed. Hoping helped! but how P.2 performs will inform my next stage of EDF aircraft design.
Eventually I hope to refine these or multiple EDF designs enough to eventually write plans on. One thing I haven't shared about these many EDF designs is that in one way or another they've all been focused on uncovering the niche that EDFs can really fill. Realizing how regardless of powertrain, most if not all electric RC planes are flying around the same Mach numbers at slow subsonic speeds, I was trying to understand why you would use an EDF over prop if at all? I didn't want to think that the only reason to use an EDF was to just emulate full scale jets in model form. Those questions lead to the above rabbit whole, my attempts to understand EDFs and subsonic aircraft design. I've been discovering new ideas, reevaluating old assumptions, and finding genuine success! I don't yet have a good answer for the niche EDFs serve from a design approach, but I'm enthusiastic about attempting to figure that out.Two airframes of the same design were created as a re-evaluation of what I assumed an ideal EDF design should be. I came across my first RC Design book, and developed the theory that because of how slow RC planes are (below Mach 0.70) that the best performance would come from straight wings, not swept. I created this design with the simplified goal of being fast, still believing in the power house of EDFs. The First airframe was an attempt at using a specific airfoil, however it was created wrong and could not fly. The second air frame used a more tradition Clark Y airfoil. Flew once on a very windy day, where it showed that it was terminally short coupled. On a calmer day it could not get into the air. I was using a 6S EDF on 4S and didn't have enough thrust with this un optimized inlet design.
Shortcut P.2:
The next design intended to solve the short coupled problems and power issues. I started analyzing the turbofan subsonic aircraft I get to work with at my job, and wanted to implement the ratios I've seen for inlet and thrust tube lengths. In addition I pulled a Yak-9 and put the EDF in the front. This allowed a tail distance more typical of an airplane. Along with a thinned fuselage this design should have flown, however I couldn't do things normal and tried to make a design that depended on spoilerons for roll control. I didn't understand spoilerons enough back then, so this design could not fly. The fuselage as well was very weak at the wing joint, so it broke easy. Thus I abandoned this design
Detour:
Around the same time of Shortcut, I got access to an Arrows Mig-29. Not confident in my ability to fly such a bird in my area, I thought the parts would find better use in a unique design. Detour was an attempt at a more conventional approach to an EDF with my ideas in mind that could be modified easily going forward. The EDFs were mounted now on pylons over the CG, and with these inlet and thrust tube lengths I surmised from multiple real world jets. Detour could have flown too, but I did not fly it. Where Shortcut 2 was too ambitious Detour was too safe. I worried I would settle for adequate. I never flew Detour, but it was a good design study to refine building techniques.
Swoosh Reprise P.1:
At this point in my journey, I wanted to combine the desire to use a straight wing, avoid a short coupled aircraft, have the "correct" inlet and thrust tube length, and create a high performance high capability aircraft. I recalled one of my past designs, the Swoosh - a twin boom pusher prop plane, and thought that would be a good layout to fulfill my goals. Reprise was an experimental design with an A-tail produced in 2024. The A-tail was intended to keep it out of the thrust blast, the design made use of joint aileron flapperons, and it used a 4S 64mm EDF. It had only flown once, and poorly. I tested gliders before the maiden, but they didn't reveal how little the aircraft could maneuver. It was a miracle that I didn't lose the aircraft in a river. In addition the aircraft was all too heavy, being lethargic in thrust as well.
Swoosh Reprise P.2:
We finally get to a success! A lot of things happened up to the development of Reprise P.2: I learned about Wing Cube Loading, I got the Model Aircraft Aerodynamics book from Martin Simmons, and I found more definitive information on tuning a Ducted Fan powertrain. With that knowledge, I reevaluated the approach of Reprise P.1 and pivoted. The main goals of P.2 was to lighten the design as much as possible, give it a conventional-ish tail, and provide it a WCL that matched the agility I wanted and stability I wanted. P.2 has a cruciform tail to avoid the Fan blast, and a low profile low slung fuselage to provide a clear pitot inlet for the fan instead of the bisected duct. P.2 was my first successful EDF design (kinda poetic, since back in 2015 the original Swoosh was also my first successful RC design). It was quiet stable and possessed a decent thrust-to-weight ratio. I flew it all summer 2024 and modified it in a variety of ways to test new ideas and developments. Reprise proved for me that the straight wing approach could improve the capabilities of an EDF design, being able to compare in speed to a lighter prop powered design and have 5.5 minute flight time. Most of the lessons with Reprise have gone forward to the next designs.
Antagonist P.1:
The next EDF design I attempted finally made use of the Arrows Mig components. Antagonist was intended to push the exploration of EDF designs further. Reprise was good, but I wasn't wowed by its capability, so I introduced more complex attributes to test. Antagonist made use of a proper low camber, tapering wing. Two 6S 64mm EDFs with pitot inlets. It had flaps, spoilerons, and an improved version of the conjoined rudder system which used one servo. Antagonist was surprising to maiden, cause it went with no incident and flew incredibly easy. At this point I had 5 active designs all using WCL strategies and new-to-me aerodynamic theory. Antagonist had by far the highest WCL, which would have suggested it would fly at a high stall speed and high throttle. However Antagonist was perhaps the easiest most gentle design to fly, and with the lowest stall speed! Its wing design provided qualities the other builds lacked with their constant thickness wings. Antagonist was fast and confidence inspiring, and my first successful application of spoilerons. These spoilerons were spring loaded, being activated by the ailerons when deflected. Over time I modified Antagonist too, adding fairings in a variety of ways to reduce drag, and eventually deleting the spoilerons for traditional ailerons to enhance the roll speed. I also began experimenting with a device I called the Thrust Body.
This device was a fairing for the EDF motor to help retain thrust lost by the cross section change. The thrust body returned as much as 15% of the thrust of an EDF.
Swoosh Reprise P.3
Antagonist has taught me a lot about EDF design, enough to encourage me to redesign Reprise for a third time. I wanted to address a variety of shortcomings with P.2: The inlet was compromised for packaging and did lose some performance and I also wanted to integrate the thrust body. I wanted to reduce the drag of P.2 for more efficiency. And I wanted to improve the powertrain cooling and potential balance of the design. For P.3 I adopted the shoulder wing layout of Antagonist, placing the EDF low to allow for a slimmer, sleeker tail plane. The EDF position was shifted to hopefully centralize the mass of the aircraft more tightly. A duct for the ESC was introduced, and the tail booms were thinned more than with P.2, now with noses to retain the strength of them. As of writing I've only flown it once, and so far still need to correct the CG. Still it reveals very good power-to-weight, climb, and speed.
Antagonist P.2
The latest EDF design so far is the second iteration of Antagonist. I recognized that due to the compromises for the best technical performance for the EDFs on board, Antagonist P.1 had a very large cross section. Another design of mine with less power (though still 75% of it) feels faster (prop driven), so P.2 was focused primarily on reducing drag. The wing itself was moved lower in plane to the central fuselage to eliminate the area of the wing box. tail booms were thinned to reduce their drag, and the wingspan was reduced. Traditional ailerons were used, along with a refined flap system. But in addition to that I've added a new experimental approach. The central Nacelle was given the cross section of a laminar flow body, 50% position of maximum thickness. I'm calling the approach a "speed tail" like that used on some high performance cars. A significant portion of an objects drag comes from how well it reintroduces the air it displaces back together, The sleek speed tail intends to cut down on the drag of at least the central fuselage. the EDF housings themselves are faired as smoothly as I can to the middle. Other than that some relatively minor changes were also down to the tail feathers: being shifted backward for better potential stability. The fuselage was widened for better access, and a NACA duct was introduced to improve powertrain cooling. Antagonist P.2 has yet to be maidened as of writing, but I intend to directly compare it to Antagonist P.1 to see if my changes have helped or harmed. Hoping helped! but how P.2 performs will inform my next stage of EDF aircraft design.
