Ye Olde Rocket Forum

Go Back   Ye Olde Rocket Forum > Work Bench > Rocket Boosted Gliders
User Name
Password
Auctions Register FAQ Members List Calendar Today's Posts Search Mark Forums Read


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 01-10-2017, 12:12 AM
burkefj's Avatar
burkefj burkefj is offline
Craftsman
 
Join Date: Feb 2009
Posts: 462
Default Mig 21 RC RG

I've wanted to try doing a full fuse RC rocket glider Mig 21 ever since I built a profile version a few years ago. I settled on using the same vertical stab/wing/tail of the profile and use a 2.6" bt-80 lightweight tubing I had. I found a used nose cone I had and chopped off the nose and trimmed about 3" off of that keeping just the tip. I then glued in a piece of 6mm depron to block the rear of the nose cone and glued the tip onto that to give the characteristic mig 21 look. A 28" long tube seemed about right for the body and I decided on a sort 12mm sandwich profile for the canopy and spine to reduce drag instead of a full turtledeck.

I used openrocket to build a mass model putting in the weights of the components including electronics, tubing, depron etc, with an estimate of my required boost CG and what nose weight might be needed. It looked like one ounce of nose weight would do the trick and keep me at 12 oz rtf using a 24mm E-6 rocket motor which will boost that weight to around 500'. Wing area is a bit smaller at just over 1 sq foot than my other rc rocket gliders so glide will be steeper, but not as steep as my bomarc which weighs closer to 14 ounces rtf with a similar wing and much more draggy design.

I decided to use the tab for the vertical stab that goes through the body tube to hold the motor mount in place, and to use full flying tail surfaces since that was very easy to do by putting a simple aluminum pivot tube through the fuse just in front of the motor mount, and using a carbon torque rod. This meant I could get by with using just two servos for roll and pitch.

I sandwiched in some .04 styrene into the ventral to protect it for landing and used a wing skid at the front. Since the ventral sticks down in the way I couldn't put my launch rail guides at the bottom but I was able to offset them slightly and not have the rail interfere with the servos or pushrods.

Wing goes through a slot in the body tube.

I got it assembled and did some in the house glide tests without components installed and found the max rearward CG for boost to be about where I expected which required 1 oz of nose weight and my finished wight was right at 12 oz.

I chose not to paint the model to save weight and leave it in the white but use the markings from an Isreali captured Mig 21 which I think turned out nicely. Markings are hand cut trim vinyl, heated after application with a hair dryer. This plane was an Iraqi Mig 21 that defected and was flown to Isreal, done in two different color schemes with a 007 number, then given to the US for evaluation. There is a plane in the Isreali air force museum painted in one of the schemes but it is not actually the same plane since the US cannot seem to find/return the original to Isreal.
Attached Thumbnails
Click image for larger version

Name:  mig213d.JPG
Views: 43
Size:  24.3 KB  Click image for larger version

Name:  WP_20161229_09_29_40_Pro.jpg
Views: 43
Size:  323.0 KB  Click image for larger version

Name:  WP_20170106_19_58_13_Pro.jpg
Views: 50
Size:  259.6 KB  Click image for larger version

Name:  WP_20170107_15_34_31_Pro.jpg
Views: 53
Size:  356.1 KB  Click image for larger version

Name:  WP_20170107_15_33_50_Pro.jpg
Views: 57
Size:  376.5 KB  Click image for larger version

Name:  WP_20170107_13_49_40_Pro.jpg
Views: 79
Size:  375.6 KB  
Attached Files
File Type: ork mig21.ork (2.1 KB, 27 views)
__________________
RC Rocket glider kits
www.dynasoarrocketry.com
Reply With Quote
  #2  
Old 01-10-2017, 07:40 AM
neil_w's Avatar
neil_w neil_w is offline
Mr. Cut-by-hand
 
Join Date: Nov 2015
Location: Northern New Jersey
Posts: 439
Default

Spectacular, maybe the most "realistic" one yet. Love the nose and the sculpted cowl on top.
Reply With Quote
  #3  
Old 01-10-2017, 07:43 AM
mojo1986's Avatar
mojo1986 mojo1986 is offline
Old Canuck Modeller
 
Join Date: Mar 2005
Location: Kingston, CANADA
Posts: 2,160
Default

Wow! Your ability to finish these things is fantastic! Can't wait to see the flights! Way to go, Frank!


Joe
Reply With Quote
  #4  
Old 01-10-2017, 11:18 AM
burkefj's Avatar
burkefj burkefj is offline
Craftsman
 
Join Date: Feb 2009
Posts: 462
Default

Thank you very much! Hopefully we'll get out of this rain/sleet/snow cycle in Oregon and I can fly it this weekend....

If you want to see more photos of how it went together you can look at my rcgroups thread:

https://www.rcgroups.com/forums/sho...65-Mig-21-RC-RG
__________________
RC Rocket glider kits
www.dynasoarrocketry.com
Reply With Quote
  #5  
Old 01-10-2017, 10:28 PM
AstronMike AstronMike is offline
Craftsman
 
Join Date: Sep 2007
Location: Lakeland, FL
Posts: 224
Smile Neato

Always nice to see what you're cranking out, Frank!!

Reckon you're also still searching for a suitable Depron replacement as well. Please keep us posted on those developments!
Reply With Quote
  #6  
Old 01-11-2017, 02:49 AM
burkefj's Avatar
burkefj burkefj is offline
Craftsman
 
Join Date: Feb 2009
Posts: 462
Default

I've tried MPF and value xps and variation, softness and stiffness ruled them out, cellfoam 88 was nice and stiff and consistent with a nice finish, but it was very weak, snapping much too easily. Foamboard is too heavy for my kits that I've found so far, and I tried the waterproof flitetest foam board and CA won't stick to it, they recommend hot glue which is heavy and would not work for my kits either The waterproof foamboard is brown so would require added weight from paint. No good substitute at this time, but I do have enough parts cut for 60 more kits till I run out.

My kits were a pretty optimum weight/size and strength, so finding an easy substitute that does not require a complete redesign, or reduction in boost/glide performance is not as simple as you might think. MPF is probably the closest thing out there, but I would not want to sell kits from it at this point.

Frank


Quote:
Originally Posted by AstronMike
Always nice to see what you're cranking out, Frank!!

Reckon you're also still searching for a suitable Depron replacement as well. Please keep us posted on those developments!
__________________
RC Rocket glider kits
www.dynasoarrocketry.com
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump



All times are GMT -5. The time now is 05:44 AM.


Powered by: vBulletin Version 3.0.7
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Ye Olde Rocket Shoppe © 1998-2024