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Old Mar 24, 2010, 01:47 PM
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Build Log
MiG-21 MF (Fishbed J) Scratchbuilt

Just started my latest scratch build project, a 1/8-th scale MiG-21 MF (Fishbed J) for a 101mm fan.

This thread in German

So far I managed to find some time to patiently cut out all the fuse formers and trial fit the fan ...

It will eventually be powered by a Neu 1515 motor in a 101mm fan on a 9S 4000 setup; depending on final weight (< 9 lbs) power will be in 3.0-3.5 kW range.

Inspiration for the MiG-21 project came from another avid edf-er JC (Bidule),

http://www.rcgroups.com/forums/showt...1177686&pp=100

I found this particular plan on e-bay:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=200453935022

The plan is nice and seems very well made ... will know more about the quality after the MiG has flown

Edit Jan 7 2011 : Video of the second flight of the MiG-21:

MiG-21 MF (Fishbed J) 100mm EDF (4 min 4 sec)


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Old Mar 29, 2010, 04:42 PM
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Still in the process of making a kit from the plan.

Transferred with artist carbon paper, cut out and sanded all the wing ribs. The wing assembly will be next.

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Old Mar 29, 2010, 04:52 PM
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I am using this 101mm fan, which is quite lightweight (179g) and should be able to take ca. 4kW no problem.

I spent about half an hour statically balancing the rotor with my magnetic balancer. The rotor needed quite a bit of weight ...

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Old Mar 30, 2010, 12:37 AM
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Very nice!!!

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Old Mar 30, 2010, 11:11 PM
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Thanks

The small one flies pretty well : Hope to break the sound barrier with the big one

.

Alfa Model MiG_21.wmv (2 min 15 sec)


... and so does the big Airworld one:

Arvika 2009 - Gränsträffen - Tom Storvik MIG-21 (8 min 10 sec)
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Old Mar 31, 2010, 01:10 PM
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The wings are partially sheeted, and part of the basic fuse framework is done.

The plans are for an icdf setup (Kress fan and K&B engine), with the df unit and fuel tank sitting almost right on the CG.

I think I need to move the fan & motor back, so I can move the batteries forward, and still get the right CG.

.
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Old Apr 03, 2010, 09:44 AM
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Subscribed!

Looks nic eso far
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Old Apr 08, 2010, 07:08 AM
jean-claude Terrettaz
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Carp, Ontario, Canada
Joined Mar 2000
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canopy

My e-mail :karen.jean-claude@sympatico.ca
Hello my friend,
How is the build advancing?
I did the canopy and I'm facing the how-to attach and make easy to remove...
Maybe you can help me a bit here
Maybe making two parts like the real one??
Anyway, I joint my e-mail address this way it's a bit more private , but I will continue to ad progress on the e-zone thread.
I fine a nice way to attach the main hatch I will post a pic later.
When I resolve the canopy attachment , I will shoot the primer and I will test fly the model . next month
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Old Apr 08, 2010, 07:10 AM
jean-claude Terrettaz
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I will send you I link for a nice planking method .. maybe is done already!
A bientot
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Old Apr 09, 2010, 11:56 AM
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Thanks JC ... usually I don't worry about canopy latches etc. until after the maiden.

Many times we have done the first flight with just tape holding down the canopy

You canopy plug looks great !

I managed to get a little done on mine, not much, I spent more time thinking about the setup (power and component location), order of build etc. than actual building.

Such as: glass wing first and then attach, or vice-versa etc.

PS. Try to send the fax again. Thanks!

Ducting:

The MiG-21 has one very long but straight intake ... The idea here is to have the ducting act like a "spine" for fuselage, giving it most of the rigidity. This way I don't rely on the exterior balsa planking and fiberglassing to give all the strenght.

Consequently I used light 1/64 ply also for the exhaust ducting, and not a material such as mylar - which is light but gives no rigidity.

.
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Old Apr 09, 2010, 12:06 PM
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Wings, elevators and rudder setup

I decided to use the scale outline for the ailerons.

The elevator servos are embedded in the horizontal stabilizers, this way the linkages are short, tight and slop-free. I used two small 9g airtronics servos (identical to futaba 9g servos).

The rudder servo is a hitec hs-82 mg.

The aileron servos are hs-82s mg and the flap servos are hs-85s mg.

In the end I plan on having nine servos (2 ail, 2 flaps, 2 elev, 1 rudd, 1 nosegear steering, 1 airvalve)

.
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Old Apr 09, 2010, 12:15 PM
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This is how it looks so far ... one very long beast

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Old Apr 09, 2010, 12:20 PM
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First attempt at a shock cone... will have to try different shapes to see what works best for the edf.

In particular the back end could be made longer to smooth out the airflow into the fan.

My intake diameter is now at around 94mm, but a sharp balsa intake ring still needs to be fitted.

The shock cone in the picture below is 64mm diameter, giving therefore an intake area of roughly 37.2 dm^2.

The 101mm fan I am using (inner rotor diam 42mm, outer rotor diam 96mm) has a FSA of ca. 58.5 dm^2,
so that would give a 64% intake - which is a bit on the small side

To get an 80% intake requires a smaller shock cone that's around 54mm in diameter, giving then an intake FSA of around 46.5 dm^2 ...

A 54mm diameter shock cone means making a second cone shaving off 5mm per side on the original (semi-scale) one which is not too bad.

.
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Old Apr 12, 2010, 04:33 PM
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Still waiting for the retracts (Springair) but the wing and tail surfaces are almost done.

So far each wing is 6.6oz with two servos each, and the two horizontal stabilizers are each 1.0oz with servos. The vertical fin is 2.2oz with he rudder servo. All still need to be closed up and fiberglassed.

.
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Old Apr 12, 2010, 04:36 PM
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First attempt at a canopy plug, the canopy is simple enough that it could be made out of bent plastic sheets and a ply frame.

.
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