Official Black Horse 1724mm Dornier DO335 Pfeil ("Arrow") Thread

[Oxotnik]

Dang! So simple.

My Do-335, as outfitted in the Maiden Flight post weighs 15.6 lbs (that's two pounds more than I'd estimated). The 6S-8AH battery pack (pair of 3S batts, plus heavy duty serial cable) weighs 2.6 lbs (this weigh is included in the 15.6 lb AUW). Based on that, here're the updated performance calcs for my Do-335:

AUW: 15.6 lbs
Wing Loading: 37.8 oz/ft^2
Wing Cube Loading: 14.7

Power total: 2690 Watts
Power/weight: 172.4 Watts/lb

[OV10]

I was also thinking that when I replace the plastic Corsair spinner with the aluminum TruTurn spinner, that the moment arm of the additional mass would bring the CG back a tad.

I’see if I can cone up with a way to get an AUW. Unfortunately, my small scale only goes up to 10-lbs and a bathroom scale would be grossly inaccurate on that low end of the scale. A few months ago, I’d done a little online searching for an economical 20-25 lb scale, but nothing jumped out at me. The Post Office would probably frown on me asking them to weigh a 68” warbird on one of their scales. LOL

I’ll see if I can come up with a clever way to get an accurate AUW.

Oxotnik Chuck...…..What I do that has been very reliable and pretty much spot on is to weigh myself on the digital bathroom scale and then re-weigh myself while holding the model and take the difference.

[Twowingtj]

I just use a couple of loops of 1/8" braided nylon cord, padded if needed, and a digital fish scale. Most are pretty accurate for our needs.

I use a Vanessa rig to CG most of bigger birds. The fish scale is part of it as well. That way I get AUW at the same time.

[Oxotnik]

I was also thinking that when I replace the plastic Corsair spinner with the aluminum TruTurn spinner, that the moment arm of the additional mass would bring the CG back a tad.

I’see if I can cone up with a way to get an AUW. Unfortunately, my small scale only goes up to 10-lbs and a bathroom scale would be grossly inaccurate on that low end of the scale. A few months ago, I’d done a little online searching for an economical 20-25 lb scale, but nothing jumped out at me. The Post Office would probably frown on me asking them to weigh a 68” warbird on one of their scales. LOL

I’ll see if I can come up with a clever way to get an accurate AUW.

[Twowingtj]

Congrats on the maiden Chuck. Good job! I suspect it will be closer to factory CG when you get the Tru-turn hung on the back end.

I don't know if you can, but I'd be curious what she weighs in at with the lipos loaded. And if it's close to spec or much above. I'm just wondering if she's a bit beefy and loading up the surfaces causing the rod flex.

[Oxotnik]

Congratulations Chuck!! The best news I've had today, and very encouraging for me going forward with my Do335. I really appreciate all the details.

Thanks, Nick. While you’re modding you’re 335, look carefully at the elevator and rudder pushrods, since you’re also planning to run the freight train 6S/5055/16x10x3 setup.

[MrSmoothie]

I successfully maidened my Do-335 today

Congratulations Chuck!! The best news I've had today, and very encouraging for me going forward with my Do335. I really appreciate all the details.

[Oxotnik]

Oxotnik CONGRATS :trophy:
I can hardly wait for ya to reinforce the rear control surface pushrods on that Chuck and then give the WOT treatment to that power system and tell us what ya think then.:pop
Can the ol' Warbird spec out a power system

I'm flying a FrSky GPS in my 335. I flew at half throttle for almost the entire flight. The GPS recored a peak ground speed of 93 mph (maybe 5mph wind during the flight). I bet that if the 335 can be opened up, she'd do every bit of a Buck 10.

When I had the 335 on a prep bench for the range check, when I opened up the throttle during the range check, the 335 was making the prep bench roll. At 2690W total, she's a friggin freight train for sure. LOL

[OV10]

Oxotnik CONGRATS :trophy:
I can hardly wait for ya to reinforce the rear control surface pushrods on that Chuck and then give the WOT treatment to that power system and tell us what ya think then.:pop
Can the ol' Warbird spec out a power system

[downwind3zero]

Awesome job man! Congratulations! I've been up waiting for this post. Thank you for your documentation.

[Oxotnik]

Maiden Flight Report

I successfully maidened my Do-335 today. Upon arriving at the field, I carefully checked the alignment of the ailerons, elevators, rudders, and flaps. Did a thorough range check with the engines at full throttle, with no problems. Did a taxi test to get the nose-wheel steering trimmed. One of the Main Struts rotated in the trunion. Several grub screws were loose on the Mains and were vigorously retightened. After tightening the screws, the 335 taxxied just fine (and later took off and landed just fine, too). I know that I’ve described my setup in other posts (and some of it multiple times), but for the completeness of a maidened flight repot, I’ll describe my setup again.

Radio: JumperT16
Receiver: FrSky X8R (two), running on 8.4v from a 2S LiPo receiver battery.
Motor (tractor and pusher): Freewing 5055-390Kv (Flightline Spitfire), with prop adapter from Flightline 1.6m Corsair)
Prop: MAS 16x10x3 (tractor and pusher)
ESC: Hobywing 60A ESC, BEC power disconnected
Battery: 6S. Two CNHL 3S-8AH-30C batteries wired in series.
Flight Weight: 15.6 lbs
Wing Loading: 37.8 oz/Ft^2
Wing Cube Loading: 14.7
Power: 2690 Watts
Power/Weight: 172.4 Watts/lb

Weather: 70°F, winds 5 – 10 mph, clear skies and sunshine.

Although I didn’t put a wattmeter on the motors at the field, I had done that at home and the motors, each pulled around 55 Amps and 1340 Watts. When I did the first power-on range test, the 335 moved the stand, to the amazement of those watching. The guys all really impressed with the output of the inline 5055 motor and 16x10 props.

Take off was incredibly easy. I’d previously done taxi tests and had the nose-wheel steering trimmed in nicely. The takeoff roll and climbout was straight as an arrow. The climb out was much steeper than I would’ve liked, but she had a lot of up trim, that I had trim back out.

Flying was easy, too. She was very predictable and flew like she was on rails. I was not aggressive with her on this first flight (didn’t even roll or Immelmann), but I could tell that she’d easily be up that. The only surprise that I experienced during the entire flight was when I decided to do a WOT pass down the runway. I can in on shallow dive as I brought throttle to full. Almost instantly, the 335 started wagging her tail like a fish. I eased back on the throttle and she resumed easy predictable flight again. (more on this in my final thoughts and recommendations)

Landing was very predictable, as well. I came in a bit high and fast, as often when landing from the North on this field, due to the trees lining both sides of the runway. I’d misjudged the throttle input a bit as I was turning onto final. She was high and fast; so, I chopped throttle and came in on a rather steep approach and brought power back up as I neared the ground. I was a little doing that, though, and the 335 plopped down a bit harder than I would’ve liked. I’d actually half expected her to bounce. Because she didn’t tells me that the suspension in the gear is well engineered. I flew for almost 5 minutes. After the flight my 6S-8AH battery had about 75% of the capacity left (about 3.85 v/cell).

Final Thoughts and Recommendations:

If you’re planning to run a power train as aggressive as the 6S, 5055-390kv, MAS 16x10x3, be careful at high speed. After the flight, I checked the elevator and rudder pushrods and discovered that by manually pushing on the rudder and elevator that the stock pushrods will flex inside the fuselage. I’m suspecting that the heavy propwash was causing the elevator and/or elevator to flutter.

Recommendation: Stiffen the rudder and elevator pushrods. Either add addition supports within the fuselage or replace the pushrods with 4-40 pushrods.

My Do-335 flew better than expected. Even though it was a maiden flight and I more tense than usual, I still enjoyed the flight. She was very well behaved during takeoff, flight, and landing. If the Do-335s aerosurfaces are visually trimmed, there should be no surprises during the takeoff and climbout.

She’s a real keeper. I can’t wait to fly her again, now the maiden-flight pressure is off!!!

[Twowingtj]

Oxotnik Good luck on the maiden. Glad the hear that it did CG with the 8k lipos. Do you have any idea what the AUW on it is?

I was planning in the future to put nose gear doors on it and have the landing light operate with the gear. I thought that the cicuit board from the FW A-10 would suit the purpose to do that. I did find out that the XWave retracts work on the opposite signal than the Freewing A-10 retracts. I had to reverse the channel in the transmitter. So when the gear are up, the light comes on. Goes out when extended.

[Oxotnik]

I’ve had a couple PM’s asking about balancing with the 6S-8AH battery pack. I went the route of purchasing two 3S-8AH batts (CNHL 3S-8AH-30C) and wiring them in series, to get 6S voltage and 8AH capacity. I’m parallel-feeding both 5055 motors from this pack. To balance at the manufacturer’s suggested CG location of 175mm aft of the leading edge, I had to push the battery pack as far back as it’d go in the battery compartment. I’m still about 5mm nose heavy, but plan to maiden with this slight nose heaviness.

I ‘ve got her loaded and ready to deploy. Once I get to the field, I’ll do a thorough range check, recheck the wiring and kick the tires. If no problems are encountered, I should have her in the air in a few hours. :-)

I’m a getting a bit nervous, I have to admit. Maddening small stuff doesn’t phase me anymore, but maidening large, complex warbirds still turns my stomach in knots.

[OV10]

So, I’ve decided to try to get my 335 into the air tomorrow. I’ve kluged together a makeshift aft spinner, using the prop adapter from the FlightLine Spit 5055 motor and the spinner from the FlightLine Corsair. It’s far from an accurate spinner, but it’s better than a bare prop.

I had more to do, to be flight-ready, than I thought. It’s already getting late, and I’m getting worried that I may be rushing. All I really have left to do is to balance her, I think. I’ll do that in the morning. If no surprises and the weather is decent, hopefully, I’ll get her into the air tomorrow afternoon.

Oh, I discovered today that I’d lied to you all a couple of weeks ago. I’d said that the EFlight Extra300 prop adapter would fit on the Spitty 5055 motor. Well, I was going to do that today, but the prop adapter does NOT fit. The bolt pattern matches, but the hub, onto which the prop adapter fits, is too large a diameter for the Extra 300 prop adapter. Sorry for passing on some misinformation. I’ll take my demerits... :-/

Oxotnik Appreciate ya fallin on your sword, had to just go dig out the copy of the post I put away in my tech ref files and s###can that false narrative.
NO RUSHING...…...that's why preflight checklists exist.

[downwind3zero]

Oxotnik God luck with your flight!

[Oxotnik]

So, I’ve decided to try to get my 335 into the air tomorrow. I’ve kluged together a makeshift aft spinner, using the prop adapter from the FlightLine Spit 5055 motor and the spinner from the FlightLine Corsair. It’s far from an accurate spinner, but it’s better than a bare prop.

I had more to do, to be flight-ready, than I thought. It’s already getting late, and I’m getting worried that I may be rushing. All I really have left to do is to balance her, I think. I’ll do that in the morning. If no surprises and the weather is decent, hopefully, I’ll get her into the air tomorrow afternoon.

Oh, I discovered today that I’d lied to you all a couple of weeks ago. I’d said that the EFlight Extra300 prop adapter would fit on the Spitty 5055 motor. Well, I was going to do that today, but the prop adapter does NOT fit. The bolt pattern matches, but the hub, onto which the prop adapter fits, is too large a diameter for the Extra 300 prop adapter. Sorry for passing on some misinformation. I’ll take my demerits... :-/

[Oxotnik]

downwind3zero Those look good, considering they're from the Spitfire! Points for ingenuity!

Oxotnik If the Tru-Turn spinners work out, I'd love to stock those as an Upgrade.

The tractor is a really nice fit. I found it on the shelf at my LHS. I had to special order the aft (and it's the only thing keeping me from maidening). I gave TruTurn the prop (which has wide blades (MAS 16x10x3, reverse) for the pusher) and I'm expecting it to fit nicely. I'm having them anodize the after spinner black, but I rattle-canned the tractor spinner (Krylon Fusion All-in-one, Matte Black) and it looks fantastic. I went Ultimate shape for both the tractor and pusher spinners. If I had special ordered the tractor spinner, I probably would've gone P-51 shape, instead of Ultimate, since the the tractor spinner has less L/D than than the aft spinner.

I'd love for Motion to carry TruTurn spinners, especially ones cut for reverse spinners.

[Twowingtj]

Alpha There are Tru-Turn options for both the front and rear spinners that should pull off the profile well. The P-51 style for the front and the Ultimate for the rear. 3 1/4"

I ordered both. With lightened back plates and custom cuts it was $$$.

[downwind3zero]

Used the printed spinner with the original backplate. Heated the nuts and compressed with vise to seat them. It's not a tru-turn but it turns true :) Better than nothing.

[Oxotnik]

Noooooooooooooooooo, another twin. I...cannot...resist...twins...

WarbirdCharle's gonna happy. Two nice-sized Bronco's released within a year. :-)