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1/96 Beechcraft Starship glider with spinning props
The latest installment in my scale indoor glider series is a half-size downscale of the Murph's Models Beechcraft Model 2000 Starship business plane in stock markings. For the main parts I used my new favorite paper, Canson XL Pen and Ink art paper (80 lb text/118 gsm), and for detail parts I used 24 lb bond/89 gsm paper.
Because the pusher propellers are well-shielded from hitting things during landings (and during crashes), this is the first time I've included them. Rather than build them static with feathered blades, I went ahead and made them to spin freely in the airstream. This was super fun! It was also as quite challenging at this small of a scale, and it came with a significant weight penalty. Even though each propeller assembly only weighs 0.15 g, once the nose weight to balance them out is accounted for, the addition of this feature amounts to about 0.5 g out of the plane's 4.2 g total mass. Modifications for aesthetics:
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Completed model and flying characteristics
Freshly built, this model was very satisfying. Then came the struggle to make it fly.
Because the canards straddle the nose joint, I had to guess the CG and finish the assembly before starting test flights. As described before, the CG ended up too far aft, so I had to add more nose weight after the fact. I then had to give the plane an absolute truckload of nose-up trim, both to the canards and to the wingtips. The initial careful airfoiling of the wing outer portions was for naught, since I had to heavily reflex the trailing edge upward, to the point where I think most of the lift is coming from the highly swept inner portion of the wing. I also had to deform the wings upward overall to get dihedral for roll stability, since when I first attached the inner wing sections, they inadvertently introduced unwanted anhedral. All of this mashing of the wings into shape is unfortunately evident in the outer wing surfaces, and the wingtip vertical stabilizers are now tilted forward compared to how they should be. The costs of the first version of a small-scale flying model, I suppose! With all that, the model ended up heavier than I would've liked, and it doesn't get an efficiency advantage out of its high aspect ratio wings, given that the aft-swept tips are mostly lifting downward for trim. So in the air, this model is kind of a brick. It does glide though! When thrown with a touch of bank, it seems to have a Dutch roll response, kind of a little waddle. You can't really see the props spinning while the Starship is flying, though you can hear a faint whirr from them, which is cool. Even just blowing on the props to spin them is a hoot. When I make a P.180 Avanti, I'll put spinning props on that too. Though they'd be far too fragile to put on a model's nose, I wonder whether I could get away with putting forward-facing props on twin-engine planes like the P-38? Perhaps if I fly it into a suspended sheet rather than into a badminton net. Flying into a net, the engine nacelles on the VC-25A (747) model have taken quite a bit of punishment. Here you can get some idea of what the light coming through the vellum windows looks like.
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Tags |
beechcraft, glider, rutan, spinning props, starship |
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