Buratinu Maxi 2000 by wersy

Last crawled date: 2 years, 9 months ago

Specifications
airfoils: own design
wing span: 2000 mm
wing chord: 284/140 mm
CoG: 198 mm from rear edge of the fuselage
motor camber: -4.6° (long fuselage front version 205 mm)
overall weight: 1140 g (PETG/LW PLA)
wing area: 45,5 dm²
wing loading: 25,1 g/dm²
motor: Extron 2220/12 1270 KV max 250W
folded propeller: 9 x 6"
battery: 1500 mAh 3S 40C
ESC: 30A
Print Settings
Wings
perimeter_extrusion_width = 0.5
layer_height = 0.25
perimeters = 1
fill_density = 0%
bottom_solid_layers = 4
top_solid_layers = 4
After Hans-Juergen tested the Buratinu 1600 I designed middle wing parts to expand the wingspan to 2000 mm.
Many thanks again Hans-Juergen, for printing and testing it for me!
This is way the Buratinu Maxi 2000 version was born ;)
All photographs are taken by him, and of course the video as well.
Many thanks for that too!
https://youtu.be/tHonqMbJ-0g
All other needed parts can be downloaded from Buratinu 1000
The special thing about this version also is that all parts of the wing, i.e. W3 to W5 as well as the elevons are identical to the original Buratinu version which are included here:https://www.thingiverse.com/thing:3047415
The wingend W6 is smaller. You must take it from the Buratinu Midi 1000https://www.thingiverse.com/thing:4280142
Or in case you can print larger, you can take the parts from here:https://www.thingiverse.com/thing:3857570
The Buratinu 1300 uses the same fuselage as the Buratinu Midi.
So you have to take it from here:https://www.thingiverse.com/thing:4280142
This is his report
The printing went completely easy even for the new large inner segments of the wing.
The half-shells and the skid-strip in connection with the fuselage extended at the front (205 fuselage nose) have proved very good. This makes everything look really stable, and even the (optional) launch hook for a bungee launch is glued into the skid reinforcement with a drop of epoxy via a small hole drilled from the outside. It's quick, easy and keeps the skid stable.
The center of gravity is minimally 195 mm, but I then moved it forward quite quickly and determined a range of 196 mm to 200 mm measured from the end of the fuselage as probably the best solution. Even with a CG of about 198 mm, 20 grams of lead is needed in the fuselage nose. I put the weight on the outside of the fuselage at the front for easy corrections. Later, the final weight should disappear inside the fuselage. There is enough space for this due to the extended 205 fuselage. In addition, I positioned a larger battery (1500 mA) as far forward as possible to avoid having to add more extra weight. Both measures are sufficient to achieve the CG - but this only works if the wings are printed light, i.e. with LW-PLA filament. For a wing printed in standard PLA, I don't think the center of gravity is still halfway reasonably achievable.
The motor I used is an Extron 2220/12. It has an outer diameter of 28 mm and fits the motor bulkhead exactly (bore 16/19 mm).
The 9" x 6" folding propeller clearly creates sufficient power for the model. 30A ESC is also well sized and on the safe side. In flights so far, it has been shown that the 2000 Buratinu gets too fast at full motor power in level flight and the wings start to flap. I have flown (even in climb) at half power as a rule. At full power the glider climbs almost vertically.
Some attention should be paid to the coloring on the underside of the wing. As a pure thermal glider, visibility of the model at higher altitudes becomes important so as not to lose sight of it. From experience with my 1600 Buratinu with green underside, I highly recommend choosing a more visible contrasting color (red or black).
After all the electronics found their place in the Buratinu 2000, the center of gravity was set, and the rudder deflections were programmed, I made the first takeoff as a pure straight glide with flit. The good news was that the CG wasn't completely wrong, but I had to walk just under 200 meters to retrieve the glider that had landed. He just wouldn't get back on the ground.
The next launch was then again with the bungee, but now with motor. I recorded this and the following launches with the helmet camera. The video shows the flight behavior of the Buratinu Maxi 2000 better than I could describe it with many words.
https://youtu.be/tHonqMbJ-0g
I would estimate that the 2000 Buratinu will remain probably the largest version from the Buratinu series with the same design principle. From my point of view this has several reasons.
The center of gravity can only be achieved by lengthening the fuselage, adding weight and using LW-PLA.

The wing loading can hardly be improved by the additional measures (CG/weights) compared to the 1600 (without additional weight). The value settles at about 25 g/dm². or just below.

The flight characteristics become more and more special with increasing size. While the 1300 Buratinu is an all-rounder and the 1600 a fast glider with ambitions for thermals, the 2000 should be particularly suitable as a pure light wind glider for thermals. In this respect it outshines all smaller Buratinu. However, its range of use is already clearly limited.
The really remarkable thing about this Buratinu construction kit series, from the original Buratinu to the Mini, the Midis and now the Maxi versions, is that it allows every model pilot to select and print the most suitable Buratinu for himself and his ambitions, depending on his preferences.
I have another video of the 1600 "frolicking" here.
https://youtu.be/0b0aUI8GmoI
I don't dare to do the same with the 2000 (yet) - but who knows, .....?
I am curious about the experiences of the other future 2000 Buratinu pilots. Because a rebuild is worthwhile in any case.
Finally, Michael, thank you very much for your design and for your support during the construction of the 2000 (half-shell, skid reinforcement, extended fuselage) and the many helpful suggestions - thank you!