Odyssey - 2.4m Endurance FPV | Build Thread

[kep]

Hey folks! I've been working on a 3D-printed 2.4 meter wingspan, high-endurance FPV/surveyor platform. It carries an FPV cam in a pivoting pod that can point down for aerial surveying, and is pitch stabilized by Ardupilot.

Early Render:

Odyssey specs:

• 2.4 meter wingspan using an E423 airfoil
• 3124g in PLA, loaded w/ 10,000mAh batt
  • Final ASA version 2850g, 22oz/sqin wing-loading
• Avatar HD Pro FPV cam
• 2x Sunnysky 2200 motors w/ APC 10-47SF-B4 props
• Speedybee F405 Wing FC
• PLA/PLA+/ASA filaments, Adaptive Cubic & Gyriod infills

I've been in CAD for what feels like ages, but have finally started to assemble the first flight model. The prototype is printed out of PLA, which makes it about 9% heavier and more brittle than the final intended ASA, but should give some great insight into the design and flight characteristics.

Assembled fuselage, can of Libby's Pumpkin for scale.

https://imgur.com/UK7yXu5

https://imgur.com/OpHXkzQ

https://imgur.com/C4BlvlS

https://imgur.com/FWU9sze

https://imgur.com/VA3BGef

 

[kep]

After looking at balance, Odyssey is coming in a little heavier on the tail than expected. I had concerns of tail boom buckling on landing, and so increased the infill by a bit, but it's bitten me back. I had built in 3cm of sliding room for the battery to control CG, and now, even when it's all the way forward it was just not quite enough using the originally planned layout of internal components.

I was 36g heavy on the tail (or 100g light on the nose). The tail servos total 40g, so there's my problem--moving them forward into the fuselage is my plan for the next iteration, but I have to work with what I've got now.

My first take was to move the 96g FC package to just above the battery using a rather ugly modification to the canopy, adding a bulbus volume for the FC:

Some feedback on this made me rethink my approach. Attaching the FC to something removable was dicey, even if secured well, it'd have to be constantly re-synchronized.

The new plan is to compact what I can forward and add a bit of lead. Safer, less finicky, but a tad heavier.

From left to right: dual ESCs, FC, batt, FPV processor module, FPV cam + cam pod. Still some room for the tail servos to be placed behind the ESCs. If I do ultimately want to add a GoPro, I may just extend the fuselage for the room.

 

[kep]

And here we are! Balanced a hair nose heavy, with all the hardware inside, including a 10,000mAh battery. Final mass of 3209g! That puts the wing loading at 25.1 oz/sqin, oh boy that's up there! Odyssey will be fast, and cut through wind and weather. The question that remains is can I land it?

Xflr5 puts the zero-alpha cruise speed at 32mph w/ no flaps, so I'm hoping it'll be reasonable with full flaps.

https://imgur.com/sCX7t4y

Control surfaces are working great! Fuselage is stuffed with wires, so cooling may be a concern, but we'll see. Still some work ahead of me to get the FPV OSD working, tune stuff, program in RTH failback, and prepare for the maiden flight.

https://imgur.com/VuueXsc

The updated camera pod is printed at higher fidelity 0.16mm layers that really helped the gear threads mesh smoother. Here you can also see its pitch stabilization.

 

[JetCrafts]

wow youre one smart dude
i have no clue about this type of stuff

 

[LitterBug]

those Ailerons are HUGE!

 

[kep]

I'm gonna have alotta flap, for a hopefully survivable landing speed, but it'll be sensitive enough that I plan to always use stability control.

 

[kep]

Odyssey 2400 took to the skies today! Wish I had a longer clip, but it's all out of focus after this.

https://imgur.com/uqlDeWi

Flight report: She flew great--gobs of lift, plenty of thrust. Really, just the PID rates were the trickiest bit, being far too high for such large flaperon surfaces, made it difficult for the FC to keep things smooth when input was applied. An autotune in Ardupilot during the next flight should help stabilize things. Elevator had good authority in normal flight, and enough to be comfortable in Flaps 1, but Flaps 2 was on the edge. Extending elevator surface from 190mm to 230mm ish should be perfect. I might go with a tad more tail too.

Reviewed the Logs, and average speed during the 9 minute flight was 46.5mph, with a minimum speed of 33.5mph. Xflr5 estimated a minimum of 32mph. So we're pretty close to our flight model!

She sailed smoothly into some brush. A little banged up, and a perfect opportunity to test the viability of a fiber-epoxy repair method I've been wanting to try. The epoxy is drying now--and it'll be ready to fly this week when I'm back on the runway.

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