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Jan 28, 2017, 02:36 PM
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Build Log

Sukhoi Su-47 Berkut twin 70mm EDF (LX)


I got this one as an "airframe only" kit for $129

http://www.bananahobby.com/8-ch-blit...f-jet-kit.html

https://lxhm.en.ecplaza.net/products...47-rtf_1410471

http://www.f-hobby.com/sky-flight-su...or-thrust-p-13

http://www.generalhobby.com/su47-ber...ion-p-816.html

https://www.turbines-rc.com/en/jets-...p-upgrade.html

https://ru.aliexpress.com/item/Twin-...795390878.html

The manufacturer is listed as "Sky Flight Hobby", and occasionally as LX or Lan Xiang.

The kit version is fine for me, as I really don't need all the extra junk motors, junk fans and junk escs

Will strip out all that thrust vectoring stuff, plastic nozzles, plastic mounts etc as well, and as a result lighten it up as much as possible.

Power setup will the twin WeMoTec Mininfans EVO 70mm on 6S.

Here's a couple of videos of how mine flies :

Sukhoi Su-47 Berkut (3 min 21 sec)


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Sukhoi Su-47 Berkut (3 min 50 sec)

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The original Su-47 Berkut does all sorts of wild aerobatics, which in the model requires a very LIGHT airframe and lots of power

Su-47 Berkut - Extreme Maneuverability (5 min 50 sec)


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Last edited by Herb; Apr 06, 2019 at 12:06 PM.
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Jan 29, 2017, 01:07 PM
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Here's a few pictures of the original I collected on the internet, rather sexy plane when viewed from the right angle

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Jan 29, 2017, 01:08 PM
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Found a video of a very nice turbine one, too bad it was lost due to unknown cause (looks like radio issue or servo/linkage problem),

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Last flight Sukhoi SU-47 JET WORLD MASTERS MEIRINGEN SWITZERLAND 2013 (5 min 27 sec)
Jan 29, 2017, 01:10 PM
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Banana also had a $155 airframe of the Sukhoi PAK FA Сухой ПАК ФА (T-50) in twin 70mm

http://www.bananahobby.com/12-ch-bli...f-jet-kit.html
Jan 29, 2017, 01:17 PM
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Friedhelm Graulich removed the gear, and took out all that thrust vectoring junk as well.

Here's how his flies That kind of RTF weight will be hard to achieve with landing gear, but my plan is to get close to it.

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SU 47 von Friedhelm Graulich (3 min 0 sec)
Last edited by Herb; Jan 29, 2017 at 01:23 PM.
Jan 31, 2017, 07:46 PM
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The price wasn't bad, including tax & shipping it add up to $158

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Jan 31, 2017, 07:48 PM
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The contents were nicely packed & double boxed, and I did not find any damaged or missing items (yet ) ...
Jan 31, 2017, 07:50 PM
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The fans look like real cheap thin plastic wemotec copies, the thrust vectoring units are nicely done - but I won't use them.

The twin fans must resonate like crazy with those thin plastic shrouds.

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Jan 31, 2017, 07:51 PM
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The drag chute is included, I like the idea so I might keep it if it works reliably (it did in my FW G-91).

The canopy seems ok although not of the best quality.

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Jan 31, 2017, 07:54 PM
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The included landing gear works on a worm gear and a separate electronic controller that sense overcurrent at the end points - quite similar to current servoless retracts.

One of the plastic parts came pre-broken, but I managed to replace it with a hitec nylong servo horn, which seems to work fine.

EDIT: Complete landing gear later replaced with Freewing Su-34 all metal struts & gear units from MRC.

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Last edited by Herb; Mar 09, 2017 at 11:44 AM.
Jan 31, 2017, 07:56 PM
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I then checked the retract operation, and they seem to work fine ... I added some light touch of grease.

The overcurrent switch at the endpoints leads to a bit of a voltage drop.

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MOV08327 (0 min 44 sec)
Last edited by Herb; Feb 02, 2017 at 12:43 PM.
Feb 01, 2017, 11:32 AM
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I then re-tested the landing gear one more time ... after cycling it twice the second one broke , fixed that with a second hitec servo horn, then the third one broke . So now all three have a new nylon hitec cut-down servo horn, which hopefully will hold up.

It is good that I tested it ... it's not fun to have a new edf jet and find the gear does not cycle properly on the first few flights.

I am rather surprised that nobody mentions this problem anywhere, the plastic (styrene) plastic lever parts are clearly worthless, and so is the gear unless it's fixed/modified

It should have been easy for the manufacturer to switch out the defective plastic parts with stronger nylon?

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Feb 01, 2017, 12:23 PM
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Once the landing gear issue is done and solved for good I will move on to the servo setup.

Mine will be like the original Su-47, which uses ailerons for roll control and canards & elevators for pitch only.

Trying to fly this thing otherwise could generate some rather odd handling characteristics (eg ailerons for pitch control) and a ton of useless drag (eg canards and elevators/tailerons for roll).

I computed the correct CG for this geometry (obviously assuming all flight surfaces to be flat) and it's right at the elading edge of those twin square openings.

The paper model has a very nice smooth and stable glide at that CG ... Correct CG is obviously critical for good handling, makes no sense to correct a wrong CG with a flying surface incidence.

Canards will have an extra 2 degrees up incidence, as in my Rafale. Elevators will have a slight up incidence, to give the overall wing geometry a slight reflex.

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Feb 02, 2017, 04:15 PM
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Herb, if you use the drag chute, will you show how it works. Mine is partially built but dont understand how to install the chute correctly. Thanks Lee
Feb 02, 2017, 08:27 PM
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I have been looking at power options, one is a set of WeMoTec Minifans EVO 70mm - Arc motor, very efficient and lightweight ... The problem is one of them is used right now in the 70mm F-104 so it would have come out of there ...

The second option is a heavier (by ~6oz for the twin setup) CS 10-bl fan setup with an excellent but a bit heavier, long can MT inrunner motor.

At this point I am leaning toward the lighter WeMo setup due to that patently flimsy landing gear setup. This is a very light plane, so ~2000W or even less should be adequate.

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