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

[Oxotnik]

RE: 150 W/lb. I agree that that's a nice place to be for this Do-335. For the wattmeter/tachometer tests, I had her sitting on a prep stand at the field. These stands are heavy wooden stands with wheels on front, to allow them to be moved around the field. With both motors running at WOT, the 335 makes the stands roll. I had to put bricks in front of the wheels to keep the stand from taxiiing during the dual motor tests. :-)

During the maiden flight, she felt great. I flew almost the entire mission at 1/2 to 5/8 throttle, and she felt fantastic. I'm planning to fly her tomorrow, and am looking forward to opening her up for some high-speed flying.

[OV10]

. I'm planning to fly her tomorrow, and am looking forward to opening her up for some high-speed flying.

Lookin forward to the vid of a couple rip snortin LHSP's

[Oxotnik]

Rip Snortin' Flight...

The video quality is quite...not quality... sorry. I'd grabbed a 120° FOV camera and it makes everything look a million miles away. Plus, I had the camera angled too low on my cap, and a lot of the flying was out of view (and I edited almost all of that out). With the 4-40 pushrods installed for the split rudder and split elevator, the Do-335 was rock-solid at full throttle. I'm a bit embarrassed by the landing. I didn't manage the descent as well as I should have and set her down pretty hard. Hard enough to bend the pin that attaches one of the struts to the retract trunion to where the wheel was binding in the wheel well. I didn't want to risk having a jammed gear in flight; so, just the one flight today. I was very happy with her performance at full throttle though. I flew a bit over 5 minutes (close to 6 minutes) and landed with 50% battery remaining. I'd estimate that over half the flight was at 1/2 to 3/4 throttle. I did roll her (with aileron rates still on low) and it was a sloooooooow roll. LOL Unfortunately, that roll was out view of the dorkcam. :-/

Anyway, that's my Pfeiling for today.

[MANFRED]

Thanks! Right now, I consider the spinners a work in progress -- every time I print a part, I've changed it a little. Also, the base plate is designed specifically to engage the Flightline F4U Corsair 10mm prop hub -- not just the shaft, but also to engage a hex shape and a larger cylindrical base. I'm using that shaft on a Flightline 1600mm motor, same as Oxotnik. In other words, I think it's a little too "specific" to the parts I'm using. Then there's the big thing -- I haven't spun one yet! I have a test setup and I intend to mount one of the motors, intended prop, and after that, add the spinner, and see how it goes.

Unless you buy one of those FW-190 spinners (I think there are more than one out there that might work, but don't know), the front spinner is nearly as distinctive in profile as the rear spinner. I recall that on the RCG thread for the Starmax/Hobbyking 1600mm FW-190, there are links to a company that makes a nice ARF FW-190, similar size, that offered 2- or 3- bladed spinners. Oxo, do you know what company I'm talking about?

Good day Mr. Smoothie, have you had a chance to run your spinner designs yet?

[Oxotnik]

I'd posted this on Nick's Build-a-Pfeil Thread on RCG, but thought it was also worthy to post here. The post is discussing the repair to the strut pin that I bent yesterday when I dorked up the landing.

Another observation when I disassembled my struts: no locking fluid was used to attach the struts to the strut pin and there were no flats on the strut pin. The pin that fits into the strut is grooved; so, that'll certainly help to prevent rotation of the strut grub screws on the pin. I have put Vibra-tite VC-3 on all five grub screw that contact the pin. Before putting the struts into the RM400-90 retract initially, I'd ground flats on the pin where the two trunion grub screws contact the pin, and I'd vibra-tited those two grub screws.

If you've never used Vibra-tite VC-3 for locking threads, it's amazing stuff. It doesn't lock as hard as Loc-tite, and it's removable and reuseable, but it definitely keeps screws from backing out. Vibra-tite can be found on Amazon and eBay. I highly recommend the stuff. I never use Loc-tite any more.

When I re-install the struts into the trunion, I'm going to make sure that strut is flush with the trunion. It'll give a little more anti-bending support for the strut pins. As it was, there had been about a 1/4" gap between the strut and the trunion. On Nick's RCG Thread, he'd mentioned that he used washers to fill the gap, which is also a good idea, and maybe even better than mine.

[OV10]

Oxotnik Somehow I missed the high speed pass on the vid, maybe because ya didn't announce "and here's a rip snortin high speed pass for Warbird"

[Twowingtj]

Oxotnik I used 5mm washers to close the gap on the struts as well. When I got around to doing the nose gear, I found that a 5mm ID wheel collar worked great.

[Oxotnik]

Oxotnik Somehow I missed the high speed pass on the vid, maybe because ya didn't announce "and here's a rip snortin high speed pass for Warbird"

Next flight, my friend. :-)

I’d edited out the passes leading up to full throttle, as the passes were mostly out of view. A pass or two before the crappy landing, I announced that I had her at full throttle. Top speed, as recorded by the onboard GPS was 87mph. With a 13 mph tailwind, she’ll break a buck. :-)

Bent pin has been unbent. I’m mulching the wife’s flowerbeds now (before the storms move in). Should have the Rip Snortin’ Pfeil ready to rip snort again before bed.

[Terminater007]

Here's a Old video of my Do335 before I sold it
That's running a 14x7 apc on the front and a 14x8.5 apc prop on the rear. takeoff is using half flap Landing's with full flap need to be nice and flat. ...

,,,

[Oxotnik]

Nick's Build-a-Pfeil Blog on RCG hasn't been mentioned lately, but I encourage everyone to stop by Nick's blog periodically to see some of the fantastic 3D-printing work and detailing that he's been doing to his 335. It's fantastic work!!
https://www.rcgroups.com/forums/show...k-Horse-Models

[Twowingtj]

I wound up doing something simular to what Nick did over on RCG, with the air scoops. The goal was two fold. One was to eliminate the flanges around the parts and two, to get additional air over the battery, ESCs and more to the rear motor.

I made 1/4 " inserts for the scoops. Cut openings in both the insert and matching in the fuse. Then used the same technique to sand to fit the fuse shape. I went further on the sanding however. I went until the outside flanges came free.

I also opened up the ventral scoop. To prevent debris from entering, I glued a piece of screen between the mount and scoop when installing. That way I can check and clean the screen if needed.

[MrSmoothie]

Thanks Oxotnik!

Finally starting to look like something! Still, a lot of things left to do. But it felt good to get some of the repainting finished. My scheme is Zestorer prototype M14 (RP+UQ), which had oversized markings on the fuselage and wing undersides.

[MrSmoothie]

Here's a Old video of my Do335 before I sold it
That's running a 14x7 apc on the front and a 14x8.5 apc prop on the rear. takeoff is using half flap Landing's with full flap need to be nice and flat. ...

Thanks for posting that Terminator -- for whatever reason, that never turned up in my Youtube searches. Great flight (and especially the landing!).

[MrSmoothie]

Good day Mr. Smoothie, have you had a chance to run your spinner designs yet?

I have not. I've been playing with a modification to the "cone" portion to add a second lip to the inside of the base plate rim to ensure against centrifugal distortion. It may not be necessary at all but I don't like the idea of one of these spinners coming apart in flight and the balance consequences that would occur. I do plan to run both on a test stand before flying.

[Oxotnik]

Yesterday was a fantastic day, weather wise, here in North Babalama. I cut work-from-home early and went to the field. I had plans of really wringing out my 335, as I've only flown it very sedately thus far. Unfortunately, though, the aerogods saw things differently. First, one of the Main struts twisted in the trunion. I got it tightened down. Then, the pull-pull yoke on the nose gear wasn't grabbing the strut well enough to steer. As hard as I tried, I couldn't get the blasted yoke grub screws to grab the nose gear strut. So, I finally tossed the 335 back in the aircraft carrier and flew other things (T-33, Me-262, FlightLine Spit IX, FMS 1.7m Mustang), and even ran an off-road buggy up and down the runway at 40 mph. Had a fun day, despite not being able to get the 335 into the air.

[MrSmoothie]

I set up and ran a static test of the longer rear spinner today. I think once I figure out a way to set the spinner/prop assembly up to balance, this will work.

The test board was held in a sturdy vise stand, and as I slowly applied throttle, I cold see the spinner tip go "out" and back "in" at various points during the run-up. I may or may not have reached full throttle, and if I did, I didn't hold it long at all. I tried the lower range again with the same results, and figured "this isn't going to work."

Then I thought, let's see what happens if I put the spinner back on the base rotated 120 degrees. Surprisingly this worked pretty well, with no obvious issues, including full throttle, which I left on for a bit. I marked the relative position of the spinner to back plate, and then tried a further 120 degree rotation with similar results to the first attempt.

My conclusion is that the 3D spinner will work but it obviously has to be corrected for balance.

I know I can reprint the back plate with thinner walls and less infill -- I already did a front backplate this way. I also think the spinner could be printed a little lighter. By doing this, I figure there's less mass to be imbalanced, especially as you get out towards the tip of the spinner.

Clearly, balancing the spinner/prop assembly is the thing to do, but easier said than done, given the way it's made and held together. I'm thinking I need to make a 10 mm shaft "replacement" that is designed to work with my prop balancing device. I'll need to think this one through a little -- it'll be worth it to have the better outline spinners -- not to mention the hours I've put into this one aspect of the model!

Footnote: I used a 4500 mAh for the test and ran it down to about 55%. This was on/off, and mix of throttles, but nothing longer than a minute or two. The motor was warm when I concluded -- with the pusher prop, no air flow over the motor, and no forward motion either. Made me thing I need to do a couple more things to put a little additional air through the rear cowling.

[Oxotnik]

Nick, you might consider doing what Downwind did: Print the spinner to be mounded on the spitfire backplate.

[MrSmoothie]

Nick, you might consider doing what Downwind did: Print the spinner to be mounded on the spitfire backplate.

Interesting idea for plan B -- but at this moment I don't think the back plate is the problem. I failed to mention that I did a test run with just the backplate only and it ran just fine at all speeds. My guess is that the cone portion is to blame -- that it's long means anything out of line or balance as you move away from the prop makes the problem worse.

I really do think that I "over-printed" these parts, which seems to be a common error with those relatively new to 3D printing -- eventually one learns that you can get away with thinner walls and much less infill and still have a part stronger than the injection molded spinner cone that comes with the mode.

But I will definitely keep this idea in mind... And save the 8mm Spitfire shafts...

[MANFRED]

It looks great though! Hopefully you can get this sorted out because it looks 100 times better than the stock plastic clown nose! Regarding cooling, I wonder if you could put a louvered piece on the bottom aft of the ship to help with airflow?

[MrSmoothie]

Today I had a successful static (test stand) run of the new, lighter version of the rear spinner! I carefully balanced the prop and spinner using substitute "plug", that fits like the aluminum Corsair shaft, but has a 3mm hole through it to accept the Dubro balancing "spindle". The Master Airscrew prop was not balanced (I did that alone, first) and I think that was a big part of my previous problem. But the significantly lighter cone and base didn't hurt.

While the aft motor was removed, I drilled 3 x 3/8" holes in the firewall for a bit of additional flow. I also opened up the vents in the bottom of the fiberglass cowl.