Build Log: "Twin Wonder"

[Datum]

Hi all.

For the 4th time I think I figured out what to build for Flite Fest West (and in general). With that April date looming larger, I buckled down and decided on a very conventional plane. This time I actually started building something



Fig 1. Twin Wonder Top View

I call it the Twin Wonder. It uses two 24g hextronik 1300kv motors, has 48" span, 7.5" chord wing using a Clark Y profile, and is intended to carry short range FPV gear, a GoPro, and a 2200mah 3s battery.



Fig 2. Wing Structure



Fig 3. Wing (Main Section)



Fig 4. Airfoil Section Detail

Not particularly huge, but it has a more complex wing design than I'm used to. It uses formers to accurately make a Clark Y airfoil, and also needs a lot of accessibility to the wiring inside.



Fig 5. Landing Gear Design Sketch

There are also provisions for optional design objectives: a sprung, taildragger landing gear for soft-field takeoffs and LED strips for night flying, hopefully they will turn out okay.



Fig 6. April 16th Progress Photo

Here's my most recent progress: Wing has no motor nacelles or ailerons yet, but the main section is complete and ready for having junk thrown at it. Fuselage core is complete, with battery shelf and reinforcements integrated into center section. Still needs, well, everything else a plane needs.

 

[DamoRC]

Looking good! Will you maiden it before FFW?

DamoRC

 

[Datum]

Debating on it. Depends on if I finish early and what my self control is like.

 

[agentkbl]

so is this based at all on the FT Bloody Wonder? just wondering because of the name.

 

[Datum]

Ohhh woops never thought about that. No it isn't a big bloody wonder- it's supposed to be a slow-flying sweetheart. Twin Wonder gets its name from its motors (derived from Blue Wonders)

 

[Datum]

UPDATE!

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Fig 7. Current Progress!

Made the empennage. It has the usual stabilizers, with servos to be externally mounted (I don't care enough to make it sleek anymore).


Fig 8. Tail Underside Detail

The tail also includes a skid with skewer reinforcement to keep the rudder nice and clean.


Fig 9. Wing Underside Detail

The ailerons are also fitted to the wing, with some routing being done already.

Progress! Yay!

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Work remaining: Nose, Motor Pods, Control Linkages, + optional landing gear & wing light strips

 

[agentkbl]

Ohhh woops never thought about that. No it isn't a big bloody wonder- it's supposed to be a slow-flying sweetheart. Twin Wonder gets its name from its motors (derived from Blue Wonders)

Ah! I see. I thought as much, but with the square leading edge and box style fuse, I was thinking like a twin engine'd bloody wonder.

 

[Datum]

Update:

I found a 2axis gimbal I'm going to use for a nose camera! It's a bit heavy so hopefully I can still balance everything alright.

So far I added motor pods, and I'm working on the tail servos and nose.


Fig 10. Wing + Pods underside


Fig 11. April 25th Progress

 

[Datum]

Final Update!

It flew! I maidened it at FFW this year.

First, I found that my Turnigy 9x is really inadequate around other radios. I met a friend who let me try his Taranis QX7 and boy, did I buy one of those later that day. No control issues anymore!

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Photos

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Videos

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Design Evaluation:

Handling Characteristics

No tipstall issues, very gentle, but the plane was slightly unstable and lacked elevator authority. I'd use a longer tail or bigger empennage next time.

It was definitely underpowered- it struggled to climb and the reduced elevator authority meant a narrow speed range, requiring high throttle (70%-90%) in cruise.

Aileron authority was good, yaw authority was overpowered but helped a lot on takeoff runs.

Ground handling depended on the condition of the landing gears- when they weren't bent too badly it could take off and land with ease. The tail skid was very useful for takeoff runs, but broke off after a few hard landings.

Battery life was fantastic though. I used a 2200mah 3s battery for about 20-30minutes, including some time with the heavy gimbal configuration.

Structure

Vertical Tail was too flimsy, and wing formers came unglued.

Otherwise, a very solid build.

Landing Gear

The landing gear I made for it worked awesome. It definitely had issues with hard landings, but done correctly it cushioned it beautifully, as well as enabled super smooth takeoffs, even from rougher ground!

When using the gimbal, I had no successful landings- it simply came in too hot.

Gimbal

The 2 axis gimbal I tried worked well, but proved hard to balance right. Basically, I didn't have enough power or elevator authority to comfortably fly on. Too draggy for my two little motors it turned out (I ran at 90% throttle most of the time and ended up burning out a motor in flight- really fun crash!)

FPV

Never tried the FPV part. Sorry guys, it didn't really survive FFW and I didn't want to try it there. The FPV nose defintely held up well to continued crashing but the airframe needs repairs and I'm out of motors for now.

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What's Next?

As I rebuild my fleet, I may adapt this design to single engine out of necessity. I'm reluctant to buy another motor for the time being since I recently splurged on a Gremlin and a new Taranis. I may reuse the wing and landing gear with a Bixler-type pusher configuration, using a far beefier motor, or I might do fully conventional.

Either way I loved this plane during its short, accelerated life cycle. Its takeoff and landing performance and carrying capability were very useful, but the twin motor configuration ended up kind of a messy thing to build and fix. Hopefully something good will come from these lessons!

 

[Michael9865]

Congratulations! Nice evaluation report.