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

[handyman220]

Congrats on the maiden. That first takeoff had the pucker factor going for sure, nice save, always keep flying it.

[Oxotnik]

Congrats, again, Nick. Great save on the Maiden and a beautiful second flight.

[Twowingtj]

Congrats!

[MrSmoothie]

I'm happy (OK, elated) to report that I flew my Pfiel twice this morning. The first takeoff was a near-disaster with the plane nosing up immediately and doing the "let's stall happy dance" -- not sure how I managed, but I got it under control long enough to get the half-flaps up and lots of down trim dialed in. Then I was able to fly fairly normal and have a surprisingly good landing.

My conclusions: off of Geotex, half-flaps not necessary. Too much up trim, too much elevator travel, not enough expo. Tail heavy.

Added 4.5 oz to the firewall, adjusted the elevator and flew again. Second flight was close to perfect from takeoff to landing. Did several rolls and one Immelmann. Concluded I had too much aileron travel and dialed that back later. Very impressive plane in flight.

Now I can go back to the shop and do a few more things I was waiting on until the maiden.

I flew with Roaring Top 6250 35c today, as far forward as I could go and still get the front of the hatch engaged. I'll be looking at possible options for a somewhat larger lipo that could position further aft in the compartment, and allow me to remove the weights -- might as well have more mAh.

My big takeaway today was that my biggest fear -- that of landing -- was unwarranted. With half flaps it was very easy to land, even on the first flight with everything out of whack. I posted details and a rough low-res video on my RCG build thread while I wait for the high res video segments to be uploaded to me for editing. You can see just how close I came to a total catastrophe on a model that was "this close" to being "just right."

[MrSmoothie]

I was reading a article on Wiki regarding push - pull configurations that the rear prop operates in disturbed air from the front that decreases its efficiency so I thought I would use higher pitch on the rear.
And it seemed to work very well in my case.

On the Black Horse Pfeil? And if so, what props did you end up with? I'll be trying out 16x10x3's (C/R) same as Oxotnik in the morning.

[Terminater007]

I was reading a article on Wiki regarding push - pull configurations that the rear prop operates in disturbed air from the front that decreases its efficiency so I thought I would use higher pitch on the rear.
And it seemed to work very well in my case.

[Creative RC]

[QUOTE=Terminater007;n250224]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. ...

I had been thinking a higher pitch prop was needed at the rear. Was there a reason based on findings which had you installing a higher pitch prop at the rear?

[Oxotnik]

Oxotnik Did you get the spinner I sent you? If so, did it work for you? I am still waiting for my Tru-Turn to show up for the front motor....

Yes, I did receive it. It looks great. Many thanks! Unfortunately, I've gotten busy with other things and haven't gotten around to installing it.

[downwind3zero]

Oxotnik Did you get the spinner I sent you? If so, did it work for you? I am still waiting for my Tru-Turn to show up for the front motor....

[Oxotnik]

Looking good, Nick! Don't forget to do good motors-on range checks. With those motors and long cables, you'll want to do a good range check, to make sure that the motors and high-amp lines aren't messing with the RX. After I nearly dumped my Freewing A-10 because the motors were causing the ailerons to fail (bad solder joint that I didn't detect with a motors-off range check.), I religiously do motor-on range checks now.

[MrSmoothie]

I've got my Do335 as far as I want to go before I maiden it -- looks like Friday morning has the weather I'm looking for and gives me a few more days to check a few functional things without rushing. Today was the first time I put everything together, although I did not tighten down (nor run) the props.

If you want to see more details and pics, go to my build log last page: https://www.rcgroups.com/forums/show...1#post44426285

[Twowingtj]

For a bit of a challenge, I decided to play around with the stock pilot to see if it could be made to be usable. The bulbous head was reduced, arms adjusted, some scale details and paint added. Not perfect but, I might just use it.

Also wasn't a fan of the gun blisters on the glue on slab. So, they were cut out, filled with balsa and sanded. CF tubing barrels were added as well.

[Twowingtj]

MrSmoothie Your mods on this bird are really taking it to the next level. Well done!

I had thought about opening up the rear cowl aft vents as well. Then the thought occured that doing that might cause all of the air to completely bypass the rear motor.

My attempt to get air to the rear motor are to leave a little extra gap between the rear cowl motor opening and the spinner. In addition, I had Tru-turn do my rear spinner with the lightened back plate and a little more space around the rear prop blades. The hope is that this combination will draw the air from the three open scoops over and around the motor.

[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.

[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]

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...

[Oxotnik]

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

[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]

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]

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.