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Nov 02, 2017, 04:36 PM
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"Die Fledermaus"


I'm almost ready to order the balsa for this VTOL Quad. Much of the construction is balsa/foam with the wing spar (two 1/16" laminated balsa sheets) being permanently fixed to the balsa fuselage floor. The foam covered wing uses 1/8" balsa main ribs with the root rib being 1/4" and the end ribs being ply. Details of the ailerons will have to wait until after the wing is covered. Anyway, it's nothing spectacular, but the design is simple and straightforward, and should be a fun project.
More to follow.
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Nov 02, 2017, 06:56 PM
Nicholas Jacobs
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Quote:
Originally Posted by PlumbBob
I'm almost ready to order the balsa for this VTOL Quad. Much of the construction is balsa/foam with the wing spar (two 1/16" laminated balsa sheets) being permanently fixed to the balsa fuselage floor. The foam covered wing uses 1/8" balsa main ribs with the root rib being 1/4" and the end ribs being ply. Details of the ailerons will have to wait until after the wing is covered. Anyway, it's nothing spectacular, but the design is simple and straightforward, and should be a fun project.
More to follow.
Ailerons ? What about making the whole thing thrust vectored. No ailerons, no elevator, no rudder. Just 4 independent props ? If that doesn't work out you can always cut out the other surfaces as needed.

Nice, back to balsa (sort of).

Cheers
Nicholas
Nov 02, 2017, 08:12 PM
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I'm curious. Would low pitch props as control props still work in that configuration if you're going fast? Like if you have a quad plane and the lift props are also used for control, will forward speed effect the lift prop's effectiveness for control?
Nov 02, 2017, 09:45 PM
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I've not done this before,but the front motors should be able to handle roll, pitch, and yaw in FFF without using the rear motors. I suppose if the idea was to allow for more radical maneuvers the rears could add a bit of Wow. But since I'm still in only the foothills of this learning curve, I'm going for something more conventional. My plan is to use tricycle gear with a castoring front wheel so I can do normal takeoff and landings. I suppose I could use the rear motors like flaps for STOL.
I don't recall reading about comparative energy consumption between the same plane with different control configurations, i.e. vector control vs control surfaces. As for vector control, perhaps another day, but for now I think I'll stick with rudders, elevators, and ailerons.

Thanks guys,
Wayne
Nov 02, 2017, 10:39 PM
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Awesome! Can't wait to see how it progresses.
Nov 05, 2017, 11:25 AM
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I've pretty much finalized the design, but have yet to locate the electronics and landing gear. Ordered 8x5 bullnose props for the rear, and 9x5x3 props for the front. Also itemized my balsa requirement, but still waiting to place the order - fairly pricey. It'll probably take several months for me to pull together all the pieces, but I'm happy with it.
Apr 21, 2019, 10:59 PM
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The beginnings of Die Fledermaus v1.1.2. Nicholas suggested going with all thrust vectoring, so I'm going to give it a try. Front/rear motors on each wing will have a common servo, and I'm going to try a free wing horizontal stabilizer to see if might help alleviate pitch up during transition and/or even work. I'm also planning on building the wing as a KFm hybrid with the KFm notch on the bottom, and curved foam board top. The front props are 9", the rear are 8", and the motors will be 2216 1125kV. Only .06" separate the CG and the Center of Lift.
Apr 23, 2019, 04:16 AM
wov
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I would center the four lifting props around the CG of plane, which it clearly isn't at the moment.
Apr 23, 2019, 10:01 AM
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wov, the front and rear props are not the same diameter, so they do not carry equal shares of the weight. Think of them as being similar to two people on opposite ends of a teeter-totter (see-saw), one being larger than the other. To balance the board they are sitting on the heaviest will have to be closer to the center, the other will have to be farther away. The calculated CG and lift points on the design are correct.
EDIT: That being said, I will double-check that I accurately located the points onto the drawing.
EDIT: It checks out.
Last edited by PlumbBob; Apr 23, 2019 at 10:53 AM.
Apr 24, 2019, 03:49 AM
wov
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I understand. What is the advantage compared to four identical motors/props and moving the front motors a little bit further forward?
Apr 24, 2019, 08:01 AM
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It allows me to position the Center of Lift as close as possible to the CG while keeping the motor pods as short as possible.
Last edited by PlumbBob; Apr 24, 2019 at 08:20 AM.


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