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Dewoitine D.520 Babe_b10
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5x5 or 6x3 prop?

Dewoitine D.520 Vote_lcap57%Dewoitine D.520 Vote_rcap 57% 
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Dewoitine D.520 Vote_lcap43%Dewoitine D.520 Vote_rcap 43% 
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Total Votes : 7

Dewoitine D.520 Empty Dewoitine D.520

Post  dirk gently on Fri Mar 29, 2019 2:15 pm

Hello All!

I decided it was time to wipe the dust off of some old Cox motors. My first project is a Dewoitine 520 with a Baby Bee. 72cm wingspan, AUW, let's say around 220g:

Dewoitine D.520 Post-6719-0-25055300-1552243423
Dewoitine D.520 Post-6719-0-00436000-1552243437
Dewoitine D.520 Post-6719-0-96283000-1552243448
Dewoitine D.520 Post-6719-0-50476600-1552638052
Dewoitine D.520 Post-6719-0-13717000-1552638065
Dewoitine D.520 Post-6719-0-21778800-1552638082
Dewoitine D.520 Post-6719-0-11305500-1552638094

You can see it's kind of close to being ready. I tried using film covering, but I gave up and went back to tissue.

Just for fun: I have some 6x3 props and some 5x5 props, so I'm going to put a poll up to ask you guys which one you think is better for this project.
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Post  rsv1cox on Fri Mar 29, 2019 3:05 pm

5X5 but I'm guessing.  Babe Bee?

Nice job on the tissue covering.

Looks like your going to add ailerons and a micro radio system. Huh...

Good luck.
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Post  dirk gently on Fri Mar 29, 2019 3:22 pm

Yup, the ailerons are already done, just haven't had the time to shoot another photo.
It will be two channel, yank and bank, two 5g servos.
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Post  dirk gently on Tue Apr 02, 2019 1:12 am

Here's the (mostly) finished thing, weighs 195g without battery. The COG is a bit more forward than I would like, so I'm going to move the receiver and voltage regulator back a bit. I'm tempted to use a 120mAh 2S lipo to save weight, as I don't need any to balance the model, I'm just not sure how many flights I can get from a battery that small.

The front-top fuselage covering came out somewhat messy and will have to be redone at some point, but it's good enough for the maiden. The rest of the tissue covering ended up great, especially the wings are tight and virtually wrinkle-free.

Dewoitine D.520 Dscn1813
Dewoitine D.520 Dscn1814
Dewoitine D.520 Dscn1815
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Post  Levent Suberk on Tue Apr 02, 2019 2:25 am

Good work. Which brand of fuel proofer you used?
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Post  dirk gently on Tue Apr 02, 2019 2:53 am

None yet (hence the "mostly" done in my previous post), but I will paint it with some thinned down epoxy, that used to work fine for me in the past.
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Post  1/2A Nut on Tue Apr 02, 2019 3:14 am

Lovely work Dirk! I have used down to 80mah before on two servos. 120 mah should get you some flights as you
have no fuel storage only brief flights with the tank on the engine. A horse shoe mount and a 1oz fuel tank would
get you 3 long flights with 120 mah. Then you dash home put the battery right on charge to see how much it
takes back. That's what I do to determine actual flights possible. Low weight plane with small servos should do
at least 5 flights with the small engine tank. Those tanks are good for CL that's about it. You can prop up and use
a exhaust throttle to extend duration. Torque can be a issue at launch though.
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Post  dirk gently on Tue Apr 02, 2019 3:22 am

Thank you!, I think I will start with the 120mAh battery then, I don't have to head home to recharge anyway, I have a field charger.
I have flown these little engines before, I'm aware of the time limitations, and I'm not discouraged by them.

Can you clarify what you mean by torque being a potential issue?
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Post  1/2A Nut on Tue Apr 02, 2019 8:18 am

Also meant to give you a thumbs up on that last post of mine Thumbs Up
Thank you for sharing good pictures and your project!

If you use a 6x3 prop with a low weight plane it effects the plane more on launch the
plane can torque over to the left right after hand launched. What is the typical run time
with the silver engine tank? Also a 5x4 maybe a good prop for the engine.

I make fuel tanks for RC flying Small Cox Logo
Dewoitine D.520 4_micr13

Beer Cheers


Last edited by 1/2A Nut on Tue Apr 02, 2019 8:23 am; edited 1 time in total
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Post  dirk gently on Tue Apr 02, 2019 8:22 am

Ah, right, now I get it. I think I will try both props, as it's almost a tie for now.
Running time is between 1.5 and 2 minutes, if I recall correctly. Then you refill and go back in the air, you can do that all day, replacing the battery every so many flights.
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Post  akjgardner on Tue Apr 02, 2019 9:01 am

Your Airplane looks good, A babe Bee will fly it Just fine. I build a lot of the Guillows kits and fly them with babe bees, The bigger ones I fly with Norvel .074s. Looking forward to the Flight Report
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Post  getback on Tue Apr 02, 2019 2:18 pm

I like the green color man she looks good hope you can post a flight of it do it's thing with U at the controls !! sunny RC Plane
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Post  roddie on Tue Apr 02, 2019 10:13 pm

I've always liked the Dewoitine aircraft. I considered scratch-building a D-520 for the 2nd CEF Speed Contest..

Dewoitine D.520 D520-010

A healthy Babe Bee is very capable of swinging a larger diameter propeller than the two that you have listed. You could certainly run a 5" diameter propeller.. but you'll burn-through that 5cc's of fuel very quickly. I've run a wooden 8 x 3 on a C/L "bipe" which was R.O.G./stooge-launched. It may have been "lighter-weight" than your RC model.. but your D-520 will be unhindered by control-lines.

Think about the "maiden-flight" of this scale-model. A strong Babe Bee with a prop that will produce the most power.. may fly the model too fast. That may not give you adequate time to set trims.. before you run out of fuel.. and is also likely to be an unrealistic scale-speed. I'm not suggesting that you maiden the aircraft with an 8 x 3 propeller.. but you may want to obtain a wooden 7 x 3.. and bench-run it, just to see how your engine runs.. compared to the other two props. You can always "bush" the hub of a larger propeller to fit. Lower RPM's = less fuel-consumption. If your AUW is light-enough.. you may be surprised.
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Post  dirk gently on Wed Apr 03, 2019 7:19 am

Roddie, looking at the picture you posted I realised I forgot to add back windows to the model, and I put the number "1" markings where the windows should be. I will have to address that.
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Post  dirk gently on Tue Apr 09, 2019 1:48 am

Here are a few shots from the underside:
Dewoitine D.520 Dscn1817
Dewoitine D.520 Dscn1816
Dewoitine D.520 Dscn1818

I'm pretty happy with the water cooler (which also doubles as landing gear).

Looks ready to go:
Dewoitine D.520 Dscn1819
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Post  dirk gently on Mon May 13, 2019 2:16 pm

It's alive!



Zips through the air with the screaming engine, I was surprised it had so much pull. I was half-expecting the little Bee would tear the model apart, but it was all fine in the end. The motor was a bit of a hassle to start at first, once it got going it would start first time, every time. I got 5 flights out of my 120mAh battery, they set back some 80mAh. As always, the worst landing was the one that made it to the movie Smile
Despite the speed, the model is an easy flyer, thanks to the forward GC. I went with the 6x3 prop, and realy don't feel the need to change anything. Flight time is about 1:40 on the integral tank.
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Post  akjgardner on Mon May 13, 2019 2:52 pm

Nice airplane, glad it flys good for ya !!!!
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Post  rsv1cox on Mon May 13, 2019 3:17 pm

Beautiful model so nicely finished and constructed. Fly's great too. You must have great eye/hand coordination to maintain flight at such speed.

Bob
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Post  dirk gently on Mon May 13, 2019 3:57 pm

Thank you for your kind words, it means a lot to me. I am indeed quite happy with how the model came out visually. I don't consider myself a good flyer though, this plane really just flies itself, in spite of the speed - I have to say though, it doesn't look as fast on the video as it felt in the air Airplane
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Post  1/2A Nut on Mon May 13, 2019 6:39 pm

Well done Dirk Thumbs Up

In time you will get use to the speed, into the wind it will float in on landing nice and slow.

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Post  dirk gently on Tue May 14, 2019 5:19 am

Just some stats for ya:
Based on the pitch of the sound at the beginning of the video, the motor is doing some 15k rpm. With my 6x3 prop (actually, 5.7x3) the performance of the engine according to http://godolloairport.hu/calc/strc_eng/index.htm would be:

Static thrust = 10.93 = 0.69 pound = 0.31kg
Perimeter speed = 113.65m/s
Required engine power = 0.076HP = 0.055kW
Estimated flying speed = 42.6mph = 37.0Knots ~70km/h (not sure about this one).

Is this kind of performance reasonable for a Baby Bee?
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Post  getback on Tue May 14, 2019 8:45 am

Dirk is that plane all stick and tissue ? what was the weight FW The Baby Bee was hauling it really well , better than you would think 2 Channel radio ? Small Cox Logo RC Plane Small Cox Logo
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Post  dirk gently on Tue May 14, 2019 9:26 am

All stick and tissue, bank and yank - radio is actually 6-channel, but only 2 channels are used.
Flying Weight is 205g (I'm guessing about 7oz). That would make for a thrust/weight ratio of about 1.5, more than I'm accustomed to with my electric-powered models.
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Post  getback on Tue May 14, 2019 10:43 am

thanks that's a good weight especially for RC . 2 channel is a lot of fun not alot to worry about ( if it's not to fast) Very Happy
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Post  dirk gently on Sat May 25, 2019 4:02 pm

Not the best flying day for the French fighter:
Dewoitine D.520 20190510

It is being rebuilt though.
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