WARNING: DO NOT TRY THIS AT HOME! …. unless you want a really freekin cool Flerken!
I’m doing several bad things to Josh Bixler’s beautiful stable design, and I don’t yet know if they’ll work. But that’s kinda my thing.
I posted this on Facebook, but realized it really belongs here on the forum, and I haven't posted in a while, so it felt like a good time.
As soon as I saw the FT Flerken I knew I HAD to make mine with EDFs. The only questions were What size, How many? …oh yeah, and HOW?!
I REALLY wanted to do twin 70mm EDFs, but there really isn't enough volume to fit them inside without changing the outer-shape, and I did NOT want to alter the outer appearance that much. So I settled on twin 50mm EDFs I still had from my old C-17 project. They are powerful little FMS 12-blade 4S fans, so I knew they’d have plenty of power.
Then I had to figure out where they could go. I followed Josh's build video like normal, but stopped before closing up the body. I knew I wanted the exhaust to come out where the motor-mount firewall normally is, but there wasn't enough room to fit the EDFs totally above the wing. So i had to mount them basically "in the middle" of the wing, and figured I'd have them suck air from both top and bottom inlets. I made some thrust tubes from poster paper and shoehorned those little suckers in there.
The air gets in through two lower inlets (main) and two aux inlets on the top. The aux inlets are passively “actuated” by the action of the fans drawing air. If they need more air than the lower inlets can supply, they hinge inwards allowing more air in. If the fans have enough air from the lower inlets, the upper ones relax closed. Functional AND it looks awesome!
The removable nose did need a lot of modifications, but most of the mess is on the inside. I basically wanted to push in the cheeks so the natural lower-body formed the inlet lip. This required some internal reinforcement however, because I basically turned a nice straight wall into a corner, which is not self-stable. It works though.
The “stock build” of the wings calls for a small amount of dihedral - an “up angle” of the wings that adds natural roll stability. For whatever reason, when I first joined my wings to the body I got a brief glimpse of them angled slightly DOWN, which is known as Anhedral - the opposite of dihedral - and it LOOKED SO COOL! Planes with anhedral are known to exhibit natural INstability in roll. For real fighters (e.g. F-16) this is good for maneuverability, but they also have the benefit of fancy control-computers to keep them in the air. For little foam planes, this roll instability is NOT usually a good thing.
While it’s not really fancy, we DO have the Aura5 Lite, and it IS a stability controller, so I thought I’d give it a try. The anhedral just looked too darned cool, and with the Aura5 it should be manageable. Worst case: it doesn’t work, I slit the wings and give it the proper dihedral.
The Aura5 is set up with the stock elevon configuration and mounted in the middle of the upper compartment along with the receiver.
The two ESCs are positioned on the bottom at the rear, just under the bottom louvers which are perfect heat vents. It's almost like Josh was thinking of me when he put those there!
Since it's a twin, the ESCs are OPTO and as such do not power the receiver and servos. For that I use an FT-7A BEC which draws power from a JST pigtail I soldered onto my ESC wiring harness. That way when I plug in my main flight pack everything gets power at once, and the Rx and servos get regulated 5V power from the BEC, AND I don't have to carry around a second receiver-battery, which would be overkill for this little bird.
For color I used construction marking orange with a little black for speckles and depth. Also the black adds a few accents to the inlets and exhaust. I also shot it with a few coats of satin-clear because the "construction orange" doesn't stick all that good, but it's a GREAT color.
I still want to add some "Flerken" letters and decals, but that will come later.
Hope that made sense! Looking forward to the maiden!
I’m doing several bad things to Josh Bixler’s beautiful stable design, and I don’t yet know if they’ll work. But that’s kinda my thing.
I posted this on Facebook, but realized it really belongs here on the forum, and I haven't posted in a while, so it felt like a good time.
As soon as I saw the FT Flerken I knew I HAD to make mine with EDFs. The only questions were What size, How many? …oh yeah, and HOW?!
I REALLY wanted to do twin 70mm EDFs, but there really isn't enough volume to fit them inside without changing the outer-shape, and I did NOT want to alter the outer appearance that much. So I settled on twin 50mm EDFs I still had from my old C-17 project. They are powerful little FMS 12-blade 4S fans, so I knew they’d have plenty of power.
Then I had to figure out where they could go. I followed Josh's build video like normal, but stopped before closing up the body. I knew I wanted the exhaust to come out where the motor-mount firewall normally is, but there wasn't enough room to fit the EDFs totally above the wing. So i had to mount them basically "in the middle" of the wing, and figured I'd have them suck air from both top and bottom inlets. I made some thrust tubes from poster paper and shoehorned those little suckers in there.
The air gets in through two lower inlets (main) and two aux inlets on the top. The aux inlets are passively “actuated” by the action of the fans drawing air. If they need more air than the lower inlets can supply, they hinge inwards allowing more air in. If the fans have enough air from the lower inlets, the upper ones relax closed. Functional AND it looks awesome!
The removable nose did need a lot of modifications, but most of the mess is on the inside. I basically wanted to push in the cheeks so the natural lower-body formed the inlet lip. This required some internal reinforcement however, because I basically turned a nice straight wall into a corner, which is not self-stable. It works though.
The “stock build” of the wings calls for a small amount of dihedral - an “up angle” of the wings that adds natural roll stability. For whatever reason, when I first joined my wings to the body I got a brief glimpse of them angled slightly DOWN, which is known as Anhedral - the opposite of dihedral - and it LOOKED SO COOL! Planes with anhedral are known to exhibit natural INstability in roll. For real fighters (e.g. F-16) this is good for maneuverability, but they also have the benefit of fancy control-computers to keep them in the air. For little foam planes, this roll instability is NOT usually a good thing.
While it’s not really fancy, we DO have the Aura5 Lite, and it IS a stability controller, so I thought I’d give it a try. The anhedral just looked too darned cool, and with the Aura5 it should be manageable. Worst case: it doesn’t work, I slit the wings and give it the proper dihedral.
The Aura5 is set up with the stock elevon configuration and mounted in the middle of the upper compartment along with the receiver.
The two ESCs are positioned on the bottom at the rear, just under the bottom louvers which are perfect heat vents. It's almost like Josh was thinking of me when he put those there!
Since it's a twin, the ESCs are OPTO and as such do not power the receiver and servos. For that I use an FT-7A BEC which draws power from a JST pigtail I soldered onto my ESC wiring harness. That way when I plug in my main flight pack everything gets power at once, and the Rx and servos get regulated 5V power from the BEC, AND I don't have to carry around a second receiver-battery, which would be overkill for this little bird.For color I used construction marking orange with a little black for speckles and depth. Also the black adds a few accents to the inlets and exhaust. I also shot it with a few coats of satin-clear because the "construction orange" doesn't stick all that good, but it's a GREAT color.
I still want to add some "Flerken" letters and decals, but that will come later.
Hope that made sense! Looking forward to the maiden!
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