Official Nexa 1630mm Junkers JU-52 Transport (Balsa ARF) Discussion Thread

[Oxotnik]

Last Wednesday or Thursday, after getting the replacement Cobra motors installed and the rudder/tailwheel throws and expo adjusted, I took my Tante Ju to the field after dinner, to see how the new setup worked. The Ju was still cranky on the ground (I'm now thinking that the problem is in the Main gear, as in one strut compresses much more easily than the other which is causing a pretty severe yaw as ground speed increases. Unfortunately, though, after getting my Tante Ju into the air, the control horn pulled out of the elevator, leaving me with no pitch control. Tante Ju slammed into the ground at ~45°, breaking the fuselage and mangling all three nacelles. I'm calling the airframe a total loss. I'll probably buy a replacement ARF. I REALLY want a Ju-52 in my Air Wing! If VQ (or Legend now) still has Splinter Camos, I'll get one of them. Otherwise, I'll get a Nexa silver Lufthansa model.

[Twowingtj]

OOS, who says German planes don't sell well?

[TwistedGrin]

Gents - thanks for posting up your Parallel wiring looms....nice work.....like I need another model.....lawd hepp me

Thanks in Advance,
TwistedGrin

[Oxotnik]

Oh, one other thing that I thought of...
After putting my Ju back together, I balanced her and she seemed a touch tail heavy, even with the 4S-5AH battery pushed all the way forward. I know that I balanced here prior to both fights and was comfortable with the balance point (although, I can't remember exactly where it was). She didn't seem tail heavy on the maiden flight, but did look tail heavy on the 2nd (crash) video during the initial climbout, although she did fly predictably once I got her up to speed and in level flight. So, I added 3/4 oz of weight to the Center Motor firewall. I think that that should keep her from dragging her tail during flight. She now balances right where the manual says that she should.

[Oxotnik]

I'm surprised that I didn't calculate wing loading and power prior to my maiden. After reoutfitting my Ju with Cobra Outboard motors and new ESCs (so that all ESCs would be the same... due to my inflight motor failure, the right outboard and right ESC were trashed and thrown away), I did some weighing and measuring and ciphering, to get some performance specs.

The wing area wasn't provided in the manual; so, I did a little measuring.
Root chord: 12"
Tip chord: 4.25"
Span (one wing): 29.25"
Doing some easy geometry with some assumptions about the symmetry of the wing and the tip chord of the rounded wing tip, I got a total wing area of 570.4 in^2 or 4.0 ft^2

AUW: 6.8 lbs
Wing Area: 4.0^2
Wing Loading: 27.5 oz/ft^2
WCL: 13.8
Power (per motor): 320W
Power (3 engines): 960W
Specific Power: 141 W/lb

These numbers gel very well with how she flew on my maiden flight. Good power and faster-than-scale speed. Pretty easy to land, but had to be on the throttle. She'll sink pretty quickly in glide.

If anyone else measured their wing and got different numbers for wing area, I'd like to discuss it.

Chuck

[Oxotnik]

I received my replacement motors yesterday (replacing Propdrive V2 2836-1000kv), since HK doesn't ever keep anything in stock. Actually, I had a lot of trouble finding 2836-class 4S motors anywhere. Even Motion doesn't have any in stock. I did finally find some Cobra 2808/30 1000kv motors (and I bought their last two). The Cobra 2808 motors are little fatter than the Propdrive 2836 motors, but are the same length. The Cobra motors cost a little less than twice the cost of the Propdrive 2836. I just finished running the Cobra and Propdrive motors through a Wattmeter test. The performance of the Cobra 2808 was very marginally better than the PropDrive 2836. And, they weigh within a couple grams of each other. They are virtually the same motor. The Cobra motor did sound a little better than the PropDrive motor, making me think that maybe it's a better motor. Really scientific, right? LOL

For those interested, here're the results of my side-by-side PropDrive V2 2836-1000kv and Cobra 2808-1000kv motors. The prop was a 9x6 (for Flightline FW-190D-9). The battery was an HRB 4S-5000 50C battery.



The published data for the Cobra 2808-1000kv and an APC 9x6 is
Vi: 14,8vdc
Imax: 17.39A
Power: 257.4 W
Thrust: 40 oz (1144g)

Here's the actual page, from which I pulled the published data above: https://rcdude.com/downloads/Cobra_2808-30_Specs.htm.

Anyway, I should have my Tante Ju back in the air this week. There's gonna be a warbird flyin at an RC Club about an hour north of me on July 25. I'm planning to take my Ju-52 and Do-335, to offset all of the Mustangs, Spits, and Corsairs that are bound to show up (in addition to the ones that I'll also be bringing... LOL)

[Oxotnik]

Me likes a lot of rudder. What can I say? I do agree that I need to dampen and/or reduce the rudder throw. it's just too dang touchy on the ground. Since I have differential thrust programmed, I can certainly get by with reduced rudder throw.

[OV10]

My Tante Ju is kinda weird. It's like she yaws one way way with the tail wheel planted, then yaws the other way when the tailwheel comes up. The rudder and tail wheel seem to be aligned pretty closely and the Mains seem to have be tracking straight. After I get new motors in her, I'll try to figure out why she's so difficult to get running straight. I like a lot of rudder throw. Maybe, I just need to dial in some more expo, to keep from over-correcting.

Aunt Ju has a pretty significant sized rudder and is easily swayed about. I never had the issues your having and looked in the manual for what I had for throw and it was 15 degrees max.
Try tamping it back

[OV10]

Tony, Charlie, would love to catch up with you guys at a fly-in sometime. We definitely share common interests in warbirds.

Hopefully a vaccine will get the year 2021 back into a more normal lifestyle and me and my newly retired sweetie can hit Fall Nall with the bigger Rollin Hangar/Bunkhouse, that should be an easy drive for you Chuck

[Oxotnik]

My Tante Ju is kinda weird. It's like she yaws one way way with the tail wheel planted, then yaws the other way when the tailwheel comes up. The rudder and tail wheel seem to be aligned pretty closely and the Mains seem to have be tracking straight. After I get new motors in her, I'll try to figure out why she's so difficult to get running straight. I like a lot of rudder throw. Maybe, I just need to dial in some more expo, to keep from over-correcting.

[Grantham Kid]

I had a couple of planes that were squirrely on take-off. I fitted gyros to the rudder and it cured the problem.

[Oxotnik]

Tony, Charlie, would love to catch up with you guys at a fly-in sometime. We definitely share common interests in warbirds.

[Twowingtj]

OV10 Nope, even closer to the field. Just off River Rd. Needed a bigger house for all the new birds in our future. That's when you know that you are seriously addicted. .

[OV10]

Where and how did the motor mounts break? We've got the same motors for my wife's JU.

We're moving, so won't get it on the bench for a while . Just looking for preventive measures if any.

I read this statement this morning when I responded to Chuck but it just didn't click. Not out of the area I hope

[Twowingtj]

Oxotnik That was one ugly spiral in there Chuck. I wonder, if you were able to add some toe in to the gear, if that might help with your take-off roll tracking?

[Oxotnik]

Sorry to hear Chuck that you had a momentary mental lapse during the emergency recovery. Thankfully these emergencies don't occur that frequently with multi electrics.

Yep, I totally screwed up the emergency landing. During the climbout, I heard a loud SNAP and could tell that I'd lost some power. I'd banked left, to bring it down the runway for a low pass, to put eyes on the plane, and spotted the non-turning right prop. It was definitely a major screw up to do a right turn with a dead right engine. I was thinking ahead of how I was planning to get into the pattern for landing and didn't think tactically how I needed to fly the plane with a dead right engine. I was very lucky to walk away from that mental lapse with only broken motor mounts and some very superficial damage to airframe.

Here's the video. I don't think that I actually posted it. I was pretty mad at myself for mis-managing the engine-out recovery.

[OV10]

Tony,
A page or two back,I think that I posted the crash video.No vid During flight, the right motor quit. I was okay, until I made a right bank to get into the landing pattern. Never bank a multi into the dead power side She death-rolled to the right, and amazingly was caught in the loving arms of a bush at the treeline before she hit the ground. Only damage to the airframe was superficial. The right motor was dangling from the nacelle by the motor wire. The left motor was loose to the touch. When I got her home and on the bench, and pulled the motors, both of the motor mounts had broken between at stress risers near screw holes. I don't know if that happened in flight (it was only my third flight) or if the motor mounts broke during the bush recovery. I would be pretty sure that it was the latter

I'd balanced all three props, but with three motors running, I could hear the vibration and dissidence. I'd used Vibra-tite on the motor mount screws, but I think that the vibrations worked the screws loose. Next time, I'll use a stronger loctite, since the screws don't have much thread length.

Sorry to hear Chuck that you had a momentary mental lapse during the emergency recovery. Thankfully these emergencies don't occur that frequently with multi electrics.

[Twowingtj]

Oxotnik Thanks Chuck. I must have missed that video. Ouch.

[Oxotnik]

Where and how did the motor mounts break? We've got the same motors for my wife's JU.

We're moving, so won't get it on the bench for a while. Just looking for preventive measures if any.

Tony,
A page or two back, I think that I posted the crash video. During flight, the right motor quit. I was okay, until I made a right bank to get into the landing pattern. She death-rolled to the right, and amazingly was caught in the loving arms of a bush at the treeline before she hit the ground. Only damage to the airframe was superficial. The right motor was dangling from the nacelle by the motor wire. The left motor was loose to the touch. When I got her home and on the bench, and pulled the motors, both of the motor mounts had broken between at stress risers near screw holes. I don't know if that happened in flight (it was only my third flight) or if the motor mounts broke during the bush recovery.

I'd balanced all three props, but with three motors running, I could hear the vibration and dissidence. I'd used Vibra-tite on the motor mount screws, but I think that the vibrations worked the screws loose. Next time, I'll use a stronger loctite, since the screws don't have much thread length.

[Twowingtj]

My Tante Ju is still down. On the last flight, both of the outboard motors broke their motor mounts (Propdrive V2 2836-1000kv), and I can't find these motor mounts, nor the motors, in stock on HK and can't find any other 2836 class ~1000kv motors for replacements. Am kinda frustrated not being able to fly to fly my new Trimotor. :-/

Where and how did the motor mounts break? We've got the same motors for my wife's JU.

We're moving, so won't get it on the bench for a while. Just looking for preventive measures if any.