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Old Sep 05, 2009, 06:02 PM
Master of the figure 9
Old Man's Avatar
United States, IN, Indianapolis
Joined May 2004
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Building Techniques for my next Mig-21

As some of you know I just finished my yet to be maidened Mig-21 from Ben Song's fantastic plans. I am getting ready to start building another one and I am looking for some advise.

1) I will not be using hot glue due to the weight. I am considering using 3M Super 77 and/or Liquidnails Perfect Glue #1. Does anybody have a lite weight glue that they would recommend?

2) After looking at John Morgan's great Thud build, I was wondering, has anybody skinned a "foamie" with just balsa? I was thinking maybe 1/16" or 1/8" glassed. Again, trying to save weight and get a nice smooth finish.

3) How should I choose an airfoil for the Mig 21?

4) What is the best method to build the airfoil? Hot wire cut from a solid slab? Built up with ribs and skinned? What about a foam base and a build up and skinned balsa top?

5) What is everyones preferred horizontal stab confirguration? Full flying or fixed with elevators?

6) Am I stupid idiot asking too many questions?

After looking at all of the beautiful models here on RCG I value your opinions and input. After all, I never could have finished the first build without the help of my fellow e-zoners.

Thank you,

David
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Old Sep 05, 2009, 06:30 PM
The Ultimate Interceptor!
DeltaDart's Avatar
United States, CA, Hilmar-Irwin
Joined Dec 2004
829 Posts
As far as glue goes, try Fabritac. You can get it at Hobby Lobby craft stores and most other craft stores and is a fabric glue. I believe its the same formula as Ultimate RC foam glue except at a 1/4 of the price. Just use a little, press together then separate, then press together again and its set. Be warned though, if you use too much it will eat the foam. Just practice on some scrap and you'll have the hang of it real quick.

Been waiting for you to maiden the Mig for a while now.Good luck on your new build!
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Old Sep 05, 2009, 08:24 PM
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Crystal River Fl.
Joined Jul 2008
3,681 Posts
Hi David! The glue I'm using is Beacon 3 in 1, same as ultimate foam glue, I get it at joann's fabric or hobby lobby craft stores,, 4oz for about $4.. Like DD is using, this stuff works the same, it is good, strong, and light.. The only issue I had with hot melt was the sanding, I didn't think it was all that heavy, I use it and 5min epoxy, but have used the beacon and 5min on the F5 build, no hot melt..The beacon glue sands good too...I would think liquid nails would be VERY heavy and hard to sand.. Flying stabs vs fixed horizontal stab and elevators? The latter is the easier to build, and works good, depends on what the plane had that you are trying to model, that is the deciding factor for me.
Airfoils, I have a software pack that I got years ago I use for making the wing design, although I asked John and he told me what he uses, I'll forward that pm to you, it has the info in it, you can find it on the web...
NO, it's not stupid to ask questions on here!! We are all here to have fun, learn, share and help each other, that is some of the great things about this hobby, and we get to meet some great people on here and make some great friends too!!
I like the foam wing I cut and covered with balsa. I'll post on my thread the weight and deminsions tomorrow.. The balsa covered foam is VERY strong. There are many other ways to build an airfoil wing on here too...
Good luck,, walt
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Old Sep 05, 2009, 11:46 PM
Master of the figure 9
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United States, IN, Indianapolis
Joined May 2004
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Walt, below is a picture of the Liquid nails Perfect Glue #1. It is clear and works similar to the Beacon 3 in 1 that you mentioned above. However, it is a real bugger to sand and it costs around $3.50 for a 3/4 oz. tube. It does have a great hold and it is lite.

I like the fixed stab with elevator style, I have to admit that I am a little nervous about my flying stab hanging up on the launcher.

I will be looking for the pm for the airfoils. I have a sheet of 1/4" Depron for the main fuse plate. I bought it because it is smoother than fff and I figured that it would make a nice smooth building platform and a nice smooth bottom for my wing. If I go with a hot wire cut wing, I figure I can laminate the upper section to the depron base and then add the leading edge. Similar to your F 5 wing.

Does anybody have any input on balsa sheeting versus foam and balsa sheeting? All suggestions are welcome.

David
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