EDF powered dream come true

[Oldbrass]

When I was a kid, a crucial part of my summer was getting some fresh balsa chucker planes and heading to the fields by the ocean to catch the winds off the North Atlantic. As I watched those little planes catch the wind, I dreamed of being able to actually fly them rather than rely on the capris of thermals and gusts. RC was not something that was in the cards for me.
Fast forward forty years.

So after building five foam board RC planes, I decided to reach back through time and make that kid’s dream come true. The profile design is lifted from a direct scan of the original, unchanged Guillow’s, red, chucker glider, as are the decals. This time though, it’s scaled up 3x, carries two 30mm EDF powered by a 3S 850 and full landing gear. The horizontal stabilizer is a full, flying tail with the pivot point about 1/3 of the way back from the leading edge. Yaw is provided by differential thrust and a single servo runs the tail. No ailerons at this point. I may add them later. Super simple but goofy fun and faster than I expected. I still have some tweaking to go, but it does fly!

 

[quorneng]

Neat.
Is that ballast on the nose?
Now you know where the CofG needs to be move the battery forward and do without ballast. Weight saving is vital with EDF's. "Every little helps"!

 

[Oldbrass]

It is ballast. I absolutely get your point about minimizing weight but my problem is the battery is already pretty far forward and I am not the best pilot. Aesthetically, having the battery mounted sideways right at the nose would look a lot like the metal clip that is present on the original glider but it would also mean that any crash landing would probably destroy the battery. I’ll see if I can figure out something to move it for a little bit and maybe add a little bit of protection as well. This model and viewing essentially as a proof of concept and I think it’s likely I’ll build a second slightly differently.

 

[quorneng]

Oldbrass
The other way to avoid ballast is to use a bigger heavier battery. Same all up weight so no improvement in performance but you do get more endurance. Say 1000 mAh instead of 850 equals 18% longer with no penalty.
Just as an aside you may well find a 1000 mAh is actually cheaper than an 850 simply because it is a more popular size in 3s.

 

[Oldbrass]

Oldbrass
The other way to avoid ballast is to use a bigger heavier battery. Same all up weight so no improvement in performance but you do get more endurance. Say 1000 mAh instead of 850 equals 18% longer with no penalty.
Just as an aside you may well find a 1000 mAh is actually cheaper than an 850 simply because it is a more popular size in 3s.

Oooh! Good point! I used the 850 because I had it on hand but that would well be worth the purchase if it removed ballast and improved performance. Good call!

 

[mrjdstewart]

that is going to be fun. you have differential thrust?

on the next one move your battery back closer to cg and you can loose all that dead weight. with these little fans every gram makes a diff.

good luck,

me

 

[Oldbrass]

Hookay! Update:

The Jetfire had a bit of a... rough landing the other day. Wings and engines are good but the nose took it a bit hard. It also seems to have killed the 850 that was powering the show. Good news is, the 1000 that I ordered arrived! So, off I go to rebuild the nose and sub out the 850 for the larger 1000, hopefully negating the need for ballast. The real trick I have is the differential thrust. It's CRAZY touchy! You have to fly it like you're thinking about making turns rather than moving the stick. My radio TX is pretty basic (Flysky T6) and I don't believe allows for setting sensitivity or curves on inputs. I know I can adjust for max inputs, but I'm not sure what that does for overall throttle. I'll have to mess around.

Bottom line, it FLIES! And not only that, it flies at cruise at something like 15% power. It's crazy. I'm actually tempted to just add a rudder and forgo the differential all together, but that means another servo and push rod.

 

[Quinnyperks]

looks great!

 

[Oldbrass]

looks great!

Thanks!

 

[GliderFlyer]

Hookay! Update:

The Jetfire had a bit of a... rough landing the other day. Wings and engines are good but the nose took it a bit hard. It also seems to have killed the 850 that was powering the show. Good news is, the 1000 that I ordered arrived! So, off I go to rebuild the nose and sub out the 850 for the larger 1000, hopefully negating the need for ballast. The real trick I have is the differential thrust. It's CRAZY touchy! You have to fly it like you're thinking about making turns rather than moving the stick. My radio TX is pretty basic (Flysky T6) and I don't believe allows for setting sensitivity or curves on inputs. I know I can adjust for max inputs, but I'm not sure what that does for overall throttle. I'll have to mess around.

Bottom line, it FLIES! And not only that, it flies at cruise at something like 15% power. It's crazy. I'm actually tempted to just add a rudder and forgo the differential all together, but that means another servo and push rod.

Wow, I really enjoyed seeing this. By the way, what did you use to cut out the decals? they look so fine!
Also, I have the FS-T6, and you can program in expo using the setup called dual rate/exp. Only on channels 1,2&4 though. For channel three it's called throttle curve. The auxiliary channels can't have expo I think.

 

[Oldbrass]

Wow, I really enjoyed seeing this. By the way, what did you use to cut out the decals? they look so fine!
Also, I have the FS-T6, and you can program in expo using the setup called dual rate/exp. Only on channels 1,2&4 though. For channel three it's called throttle curve. The auxiliary channels can't have expo I think.

Thank you so much! For the decals I use a Silhouette Cameo V2 and Vinyl from Oracle. I had to completely remake the printed images using Adobe Illustrator and then export them as an .SVG to Silhouette's proprietary software. Not exactly speedy, but soooo worth it.

As for setting up dual rate and throttle curve, I'd love to see how to do that in order to save having the weight of the rudder servo and linkage and so stretch flight times.

My hope is to get this all worked out (graphics files and 3D .stl's for printing included) and then post it all as a build for anyone interested in making the build.

I've got her flying really, really well now and it's crazy fun to fly. Sounds like a flying dentist's drill, though!

 

[Oldbrass]

She flies like a DREAM!

Here a link to the video my son shot. No sound as we were both blathering on and on about how cool it looked as well as his 1001 questions about how I was intending to land it.

 

[Quinnyperks]

Wow, I really enjoyed seeing this. By the way, what did you use to cut out the decals? they look so fine!
Also, I have the FS-T6, and you can program in expo using the setup called dual rate/exp. Only on channels 1,2&4 though. For channel three it's called throttle curve. The auxiliary channels can't have expo I think.

I had a t6, it was not good until my mother shattered it. It also browned out a lot at flite fest.