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Dec 21, 2017, 07:03 PM
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After some masking, it was time to spray some red

There's a few places where it needs some minor touch-up, maybe after the holidays...

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Dec 21, 2017, 07:04 PM
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Starts to look almost like a finished product, after some minor assembly.

Still waiting on the fan, but all the rest of the electronics is more or less in place ...

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Dec 21, 2017, 08:45 PM
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The silver underwing tanks actually improve the looks a bit

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Dec 23, 2017, 09:36 PM
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Made a simple balsa fairing around that carbon rod that sits right in front of the fan,

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Dec 24, 2017, 04:39 PM
Fly it like you're in it
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Herb, regarding your posted intake size, is that an overall diameter, or a corrected figure allowing for the shock cone?
I had wondered about a modification to the stock intake that would place the cone further in, thereby reducing it's diameter and influence on the ducting, possibly reducing or eliminating the cheater.
Quite a bit of work I'm sure, but still scale, as the full scale cone would move for and aft as required.

Edit...
Looking closer to your images, I see the large restriction created by the central diverter that houses the cockpit area(similar to a MiG15)
I don't imagine there is much to do about that
Last edited by microlyn; Dec 24, 2017 at 04:47 PM.
Dec 24, 2017, 05:23 PM
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Hi Johann, no full diameter minus the shock cone obstruction = effective intake area.

On my large MiG-21 I carved out the shock cone from the bottom, inside :

The whole nose / intake part there is a lot more aerodynamically clean, I think.

But, as you say, I doubt that the cheater intake can be eliminated on this one ...

The ducting design around the battery box on the Freewing one is well made, they used ply sides to allow as much air as possible to
flow through. As I said, the worst part is the rounded rear of the green shockcone.

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Last edited by Herb; Dec 25, 2017 at 11:28 AM.
Dec 25, 2017, 11:34 AM
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The plan is, once I get a hold of it, to install an 80mm WeMoTec EVO fan in it.

Here is how that fan flies a slightly smaller edf, with very good ducting

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FunJet Ultra 6s 2,7kW 336 -360km/h 80mm EDF WeMoTec Midi Evo (1 min 44 sec)
Dec 25, 2017, 02:23 PM
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Go some work done on the linkages & various servo covers ...

There seem to be numerous reports on Freewing servo failures, esp. the flap ones. Which seems rather odd since, just like in the case of the "blue box", I never had a Freewing servo fail myself.

Note in particular, from the picture of my MiG-21 below, that there is nothing special about these Freewing flap servos, they are just like all the other ones, standard (metal gear?) 9g digital servos.

https://www.motionrc.com/products/fr...pare-parts-tab

I have an alternative explanation: There is one unique feature of flap servos - on these or any other Freewing edf jet. If the linkage adjustment of the flap servo is done incorrectly, the servo gets stalled when the flap is up (retracted). This draws quite a bit of extra current and heats the servo up over time, until it fails and possibly brings the plane down. This is particularly true of digital servos.

It is therefore essential to carefully adjust the linkages & throws on the flaps so that there is absolutely no binding.

EDIT: Note incidentally that the above linked MiG-21 spare parts list from MRC is inconsistent with the servo list added below. The former lists a mix of plastic gear analog servos, plastic gear digital servos, and metal gear digital servos, some of them reversed. On the other hand the list below (from the MiG-21 product page at MRC) list digital metal gear servos exclusively. So there might have been some design changes along the way? I wish I knew what type of servo mine has in it.

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Last edited by Herb; Dec 27, 2017 at 12:36 PM.
Dec 25, 2017, 02:26 PM
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Marked the stock CG location at 265mm, according to the Freewing manual - with landing gear out :

Knowing Freewing it is probably slightly conservative ...

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Last edited by Herb; Dec 27, 2017 at 12:07 PM.
Dec 28, 2017, 11:41 AM
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The FMS 80mm fan finally arrived ($76 from Bangood https://www.banggood.com/FMS-80mm-12...p-1125125.html ) and is ready to go into the MiG-21, after programming the YEP 150A esc.

Programmed the HK 150A YEP esc (YGE clone, www.yge.de) using the appropriate card, with parameters set for a 4-pole medium-inductance inrunner (low advance 6 degrees, startup plane slow, pwm frequency 8kHz). Same parameters as for the indentical fan & motor in the FW A-4.

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Last edited by Herb; Dec 28, 2017 at 05:31 PM.
Dec 28, 2017, 02:59 PM
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... and finally installed in the MiG-21, had to carve some foam out of the fan hatch to make the FMS fan fit :

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Dec 28, 2017, 05:21 PM
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Installed the Hobby Eagle A3 Super II gyro (from bangood) with adjustable gain (right knob) and programmed it in the usual way as described here :

https://www.rcgroups.com/forums/show...my-Jets&pp=100

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Dec 29, 2017, 08:31 PM
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Couple of pics after one more successful sortie . Those FW aileron throw recommendation are a bit ridiculous though

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Dec 29, 2017, 08:54 PM
Fly it like you're in it
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Looks great Herb!
The control throw matter seems to be a recurring problem with Freewing. It may be time for them to find a new test pilot
Dec 30, 2017, 11:05 AM
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Not sure what is going one there ?

In my case I mostly took the throws over from my larger MiG-21, assuming from the beginning that the FW throws were on the wild side ... which was indeeed the case.

Airworld and Feibao make a nice large turbine MiG-21 that has been flying for years, both are exactly 1.4m wingspan.

http://www.airworld.online.de/Englis...IG21/index.htm

http://www.rcuniverse.com/forum/rc-j...ml#post3843795

On the other hand the FW MiG-21 is 0.8m wingspan, so the throws on the larger one need to be scaled down by a factor of 0.8/1.4 = 0.57. Those are the numbers given below:

AIL ELE RUD FLAP LOW FLAP HI

Freewing MiG-21 manual throws (hi rates) : +- 20mm +- 30mm +- 24mm xx 45mm

Freewing MiG-21 manual throws (low rates) : +- 16mm +- 30mm +- 20mm 30mm xx

AW/ Feibao turbine MiG-21 throws (scaled) : +-6mm +- 28mm +-14mm 14mm 28mm

My throws after maiden : +-8mm +-28mm +-15mm 15mm 30mm


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Last edited by Herb; Dec 30, 2017 at 12:29 PM.


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