Blender Jr.

Hi Everyone,

I've been meaning to write a build log about my Blender Junior for a long time now, but when I had time and motivation to create this article the video editing programs were doing everything in their power to discourage me.

So as you might have guessed, its Blender Jr. because it's not a baby but not full grown either. When I was building it, during last winter, I've just finished my first rc season and was starting to be bored by my scratchbuild trainer. Anyway I was still a bit intimidated by its acrobatic nature so I figured to try it make it more stable, and boy did I succeeded! :)

Basically what I've done is enlarged the wingspan (cord remained the same) and the tail feathers to match and elongated the fuse as well. These modifications added lateral and longitudinal stability to the already well behaved plane.

Here are the numbers:

Wingspan: 800 mm
Fuse: +100mm to the tail, and +35 mm to the nose to keep the CG
Horizontal stab: +10mm to the trailing edge (not to the control surface!), 20-20mm to each side
Vertical stab: +5mm to Leading edge

Also, being a European I don't have access to foamboard so  I covered the whole plane with brown packaging paper, you can find plenty of tutorials on the net about this technique, but I will write a short tutorial if there is interest. Basically you use thinned out white wood glue (PVA, Elmer glue) to cover the surface with paper that has very high wood fiber content. Its basically the little brother of fiberglassing :) It adds tremendous amounts of strength to the foam. I can literally hold the ~750 gram plane by the wingtip and the wing wont budge.

Though the plane flies like it's on rails, and floats even with the motor off (while being quite a heavy weight) I managed to do some rough landing with it. Like catching a branch while on approach and falling straight to the ground and it is still in one piece!

About the flying characteristics, as said, it flies like it on rails and being a reasonably sized bi-plane it has a nice presence in the air as well. Furthermore it handles strong wind very well, although that might have to do with mine being a bit heavy... anyway it has so ridiculous amounts of lift that it can slow to a crawl without any wing-rock or tip stalling, what makes for easy power off landings!
About aerobatics, it does loops like crazy which is not a surprise from a biplane I guess, and that the roll rate is reduced by the larger wingspan comes as no surprise either, but it can still do a single roll easily just don't try to roll it continously. By the way using all four ailerons might just remedy this!
Lastly I was never able to do a knife edge with it, but that maybe contributed to my lack of piloting skills as well as to its quite heavy nose :)

 Here is a little flying montage:

All-n-all it came out very nice, if you are looking for a step up from the trainer, and want to learn rudder usage as well, I can very much recommend to build this modified version. It's easy to edit the original BB plans, just get a ruler and enlarge the parts and also I advise to use a motor that can spin at least a 10 inch prop as the bulky nose of the BB block out most of the 8 inch one!

In case if you are wondering, the Old Fogey is my girlfriends trainer plane, am I a lucky bastard or what? :D

Thanks for reading through this rather long article!

Fly Safe!

Exhodus