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FTFC20 1939 Popular Aviation Special by Vimana89

Vimana89

Well-known member
#3
Prototyping/Flight Testing Logs

Prototype 1: 3ch RET
Wing and tail plane close to scale, but nose was lengthened and fuselage length was shorter overall than the original, making a more "short coupled" plane. The dihedral was also made too extreme. Despite all of this, the plane balanced and flew beautify on 2s 650mAh 75c with 5x5.45x2 bullnose props, with a slight bit of wing rock and Dutch roll, but overall, a decent flyer that is easy and forgiving despite the flaws.

Prototype 2: 3ch AET
Control scheme switched to ailerons 3ch, fuselage lengthened, and wing moved up for a shorter nose. Plane could only achieve balance on 3s with an 850mAh 75c battery. 5x5.45x2 bullnose prop retained. A good flyer with very forgiving and recoverable stalls, but overly loaded on weight, making it a bit touchy, more prone to low speed stalls, and sluggish on acceleration and deceleration. Still, a solid performer despite its flaws, but not really where I want it to be.
 
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Vimana89

Well-known member
#7
This is a great design, and I have a working prototype already. Video footage to come shortly. My design is mighty mini sized, can be made from one sheet of foam, and uses only the most basic building techniques. At this size, the wing can be a simple one layer affair with no airfoil. I love this plane's classic, conventional look and design, paired with a gentle, high aspect delta wing. Straight wings are nice, but much more finicky. Here's a forgiving, gentle-stalling option for a trainer that requires no airfoil construction at smaller scales, and looks classy to boot? I really can't find anything not to like about this plane, It's like a delta wing mini Scout!

My first prototype is RET, and has a couple bugs. The dihedrals are a little extreme and add a bit of Dutch roll here and there, and I'd like to extend the fuselage/set the tail plane father back. Other than that, it flies like a boss on 2s. Definitely nothing to sneeze at. Before polishing the RET version further, I'll be testing a 3ch "yank and bank" version with a much reduced dihedral and ailerons. My plan is for this to be a modular platform like the TT, and have options for 3ch RET, 3ch AET, and 4ch.
 

Vimana89

Well-known member
#8
A small teaser clip of some unedited flight footage of the prototype. The camera cut out because I thought I had recorded this entire flight and landing, which got much better later in as my confidence grew with this plane and its imperfections. This is the shaky launch and rather unimpressive warmup, and then it cuts out before it gets more interesting.

I'll get some better footage of this rough draft plane being flown to its best potential as I work out the more polished version(s).
 

Vimana89

Well-known member
#9
I think I'll start by making a nicer RET plane, with extended fuselage, less dihedral, and a more permanent top hatch. If this works well and is an improvement, I can use the electronics from the prototype to build the AET version.
 

Vimana89

Well-known member
#11
Working up AET with elongated fuselage to be closer to original plans and give better balance and elevator leverage. I think I'll try no dihedral first, since this wing is swept and mounted on top. That should give enough stability with no need for dihedral.
 

Vimana89

Well-known member
#14
Pic and video clip of the second prototype(AET version) coming shortly. It doesn't matter what control scheme you use on this plane, it flies great! This version is teaching me how to fly with ailerons properly. This is a very capable design, and it has some real high speed potential and responsiveness, but overall has gentle and forgiving flight characteristics. Stalls are gentle, and if you are flying bad, your maneuvers will look goofy and clunky, and you will have a little stall here or there, but this plane will stay in the air just fine.

Once I got a feel for how the plane handles and responds with ailerons, everything started looking smoother and cleaner. I feel this plane is just a bit heavy loaded for my liking with the 850 3s compared to flying the RET with 2s 650. I will experiment with another more polished AET prototype that can fit and balance with an 850 2s.
 

Vimana89

Well-known member
#16
Great build! Love it when they fly well! :D
Thanks, this one is a real gem. The original designer was pretty forward-thinking with this design in 1939. There's nothing not to like about this plane, it's just all around great. With my build slop and lack of experience building many planes with full box fuselages and higher aspect wings, not to mention trouble flying ailerons, this should have given me more trouble, but the '39 just flies like a boss.
 

Vimana89

Well-known member
#17
Taking a break from building for a day or two or so, then I will be back at further refining this design. I like it as RET too, but have too many RET planes, so I will strip the imperfect RET prototype's electronics and start the next version soon, which will just be a further polished version of the AET one that can balance just right on a 2s battery.
 

FoamyDM

Building Fool-Flying Noob
#18
Taking a break from building for a day or two or so, then I will be back at further refining this design. I like it as RET too, but have too many RET planes, so I will strip the imperfect RET prototype's electronics and start the next version soon, which will just be a further polished version of the AET one that can balance just right on a 2s battery.
You've been building like crazy, don't burn out. *says the man with nearly a dozen current active design projects in the air.
 

Vimana89

Well-known member
#19
Started drawing up something else to prototype for this challenge, but I'm not sure I want the scale I started designing it at, and I think it would be better to focus on this one for now. I'll be starting the next version of this tonight or tomorrow. This will hopefully be the finalized, 1.0 version on which to base the plans. I am trying to get it to balance on a 2s 850, so I will move the wing back just a tiny bit, and maybe use a 3.7g micro servo for the elevator. I could use those on the ailerons too, but I only have four and they are pricey. I'll most likely trace the pieces as I go for the plans already, and use them if it is successful. I want to try to document the build process a little more in depth, but even so, It will be brief, because this is a simple plane to build.
 
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Vimana89

Well-known member
#20
Showing this part won't be really necessary for anyone working from a plan in the future, but to make it more interesting and be more detailed and transparent with my builds, I'd like to explain my process for designing and building without software. I draw up the templates on graph paper, and then hard copy them to cardboard, poster board, or spare foam and cut them out. I trace them on the foam and use a ruler and straight edge to flesh out the fuselage and draw out a straight rectangular strip for extra fuselage plates, hatches, spines, etc.
 
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