Mig 21 RC RG

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burkefj

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Been wanting to re-do my profile mig 21 rc rg to use a tube based body and see how it would fly as an rc rg.

I resized a few parts for 2.6" tubing. Wing will be mid mounted through the tube, and the tail surfaces will be full movable surfaces with an aluminum pivot tube and carbon pivot rod. Vertical stab will go through the tube to the bottom inside and the 24mm motor mount will be in the middle of the vertical fin tab on the centerline. I built up a reinforced lower ventral to take the landing abrasion(laminated some styrene inbetween the foam), and built a 1/2" wide pseudo turtledeck/canopy piece.

I used a 2.6" styrene cone from apogee I had, cut it off about 60% of the length, cut and glued in a foam sheet piece to block the nose opening, then cut the tip off of the remaining piece of cone and glued it to the foam sheet. Worked well and came out at 1.6oz for the nose cone, but the wing CG is about 1.5" further forward than my other gliders so I will probably need some nose weight.

Just waiting for the tubing to arrive from bms. Specs, 2.6" diameter, 28" long tube, 21.5" wingspan, 39" long.

Wing area is just over a square foot, so won't have a long glide time, weight I'm hoping will be 12-12.5 with balast.

In the pics I show the pieces and the paper templates to show relative placement...

Frank

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burkefj

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I did an openrocket model I made for mass balancing, using thicknesses and weighed amounts to get approx cg with components placed as masses...looks like less than 1 ounce nose weight and about 12 oz total so far....
 
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tab28682

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Mig-21s always fly well! No doubt this one will as well.

I need to get back on my 3" 29mm and 4" 38mm balsa, ply and tubing Mig-21 RC RC projects. Shown below in a picture with my 2" free flight Mig-21 for 24mm. So far, the 3" model is just a tube cut to length....:)

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burkefj

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I'll try again using the upload feature....Here is the 3-d image of the mass balancing model, and the ork if anyone is interested.



Frank

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View attachment mig21.ork
 
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burkefj

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Tom, btw, I did reference your mig 21 when I was thinking about converting my profile to tube based...

Tom, where approx is your glide CG as a % of the root chord on your mig 21 wing, just to verify my estimate? I think my boost cg is starting at about 22% mac, or 45% root chord or 5% stability margin including the tail surfaces with glide CG forward of that as motor burns out. This is behind my profile cg location I used but that had a lot of flat fuse area forward....
 

K'Tesh

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OH! VERY COOL!!!

If you've got some graphics, I could play with them... :grin:

Now, about the Sukhoi Su-27KUB Sea Flanker...
 
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burkefj

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To avoid adding much paint weight I was thinking of leaving it in the white(not a silver base.. I know....) and using this Isreali scheme

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K'Tesh

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To avoid adding much paint weight I was thinking of leaving it in the white(not a silver base.. I know....) and using one of these schemes with trim vinyl....
I have a czech background, so I like that one, but I like the Isreali schemes...
White, Israeli it is...

Working it now.
 

K'Tesh

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Ok... Here we go... The Israeli paint scheme with white rather than "silver". I had to modify the fins (split them, change the fin tabs) to get the "decals" to apply properly.



View attachment Dynasoar Rocketry MIG 21.ork
 
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burkefj

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Very cool, that looks really nice!

Frank
 

K'Tesh

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Very cool, that looks really nice!

Frank
Glad you like it!

Of course if I had a sample to play with... :wink:

Thanks for posting that. It was a fun way to spend some time.
 

burkefj

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I think I might take the tail from the rightmost example in the first picture posted and put it with what you did, a little less red on the tail, seems cleaner....

Frank
 

burkefj

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Yeah, I kind of like that combination....now I just need a body tube.....
 

K'Tesh

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I was thinking you could always go with a white tail, and use a red chevron (and a reduced number of red and white stripes).
 

burkefj

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Ok, got the tubing in today for my Jayhawk kits and saved one for the Mig. Cut to 28" long, and proceeded to slot it for the wing and tail surfaces and do a dry fit(first picture).

Once that was done it went to together in about 2 hours taking my time. I was just able to offset the rail buttons to the side slightly and have the rail clear the ventral fin and the servo/control arms as planned. I did some indoor glide tests and it looks like my CG range was good, wound up in the middle of my guessed range. Did need right at 1 ounce for CG but my overall weight is 11 5/8 ounces total, so with markings will probably come out just under my 12 oz goal. Still torn on the color scheme...

Steps were:

Glue in wing
Install servos
Install Receiver
Glue in vertical stab
Glue in pivot tube
Glue on Canopy/dorsal spine

Frank

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burkefj

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Install rail buttons
Install front skid
Glue in motor mount
Install ventral/skid
Install tail surfaces and hook up to the servos
Set up the throws
Set CG and do glide tests.

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burkefj

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Sitting here in a snow storm in Oregon:) Wound up not having much red vinyl left, so I went with the simpler scheme but I think it's less garish anyway. This is from an Iraqi captured Mig 21 that the Isrealis painted and test flew before giving it to the US. Just finishing up some of the panel lines but wanted to take a break...

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TangoJuliet

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Looks great! Is there any concern at all about flutter on the elevons during boost?
 

burkefj

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Nope, the pivot point is at about the 25-30% point, and I've never had an issue with the 20-30 full flying tails I've done and flown, either rocket or electric powered...

Looks great! Is there any concern at all about flutter on the elevons during boost?
 

burkefj

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Had some lunch to recharge my internal batteries and finished up the bottom panel lines, and took a few more glam shots....exactly 12 oz rtf now:)

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iter

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I have seen this very aircraft. It lives at the IAF museum meat Beer-Sheba now. I might have a photo somewhere.
 

burkefj

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My wife and daughter braved the snow and ice and 25 degree weather and came out to maiden my Mig 21, here are the maiden and second flight, I only adjusted the glide trim a few clicks for the second flight but otherwise CG and throws were spot on, beautiful weather with no wind and clear sky. For as small as the wings are and the draggy nose it actually flies pretty nicely.

[video=youtube;TDsHNpCy2Oc]https://www.youtube.com/watch?v=TDsHNpCy2Oc&feature=youtu.be[/video]
 
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K'Tesh

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Nice Flights!

Where was the guy who was asking the questions from? Austria? Germany?
 

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