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FTFC'18 WWII Kalinin K-12

FoamyDM

Building Fool-Flying Noob
#1
I'll be aiming for this Russian oddity: the Kalinin K-12



This Site claims this proof-of-concept pre-WWII was a test for a larger tail-less Bomber. After successful demonstrations of this Bird-feather-painted working concept, the designer was arrested prior the larger version was finished.

While the Amazing Painting Scheme caught my eye,

It was the trailing reverse foil that got me interested.


Plus I can fly my mini-arrow with comfort now, so the failures here will be less Pilot error, and more design related. :D

I'll start with these planes here:




The Small Build is approximately 1:20 scale
Wing Span: 42"
Length: 21"
Base Chord: is 9"
Tip Chord: is 3.7"
Weight: ~350g
Wing Loading: TBD
Motors: Twin A or F - Pack motors with Differential Thrust.
Prop: 6-x4.5 Propellers
Battery: 1.65 Ah 2S or 2.2 Ah 3S.
Servos: 5 to 6 - 9g .

I will also be equipping it with FPV Gear in the Nose.
C-Pack will be 167% -Info to Come.

Check out the rest of the builds here

and other great resources
HERE
HERE
and a modeler's take HERE
 
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#3
Wow, you don't see too many Russian wings. That paint job though... you'll have your hands full just with that. Good luck. I suspect it may be pitch sensitive and you may need to increase the size of those tip fins or make the fuselage really slab sided to get enough yaw stability.
 

FoamyDM

Building Fool-Flying Noob
#4
@Rockyboy - Right?!
@Erospace - Stalin may be the reason for the lack of wings. Maybe so on the tip fins. I can't wait to see how the base version flies. The comments indicated it was a bit unstable during flight but takeoff and landing were great. I say now, "that paint job will be fun." I may not be saying that later. :p

The Kalinin K-12 was a scaled-down three-seat prototype proof-of-concept aircraft for a far larger tailless bomber. Also known as the BS-2 or the Zhar-Ptitsa (Firebird) so, I'm suspecting they were aiming for a phoenix look. They would've finished it but Stalin doesn't take kindly to being told his other project the Kalinin K-7 wouldn't work . so the designer was arrested and executed.

I think this is the full scale version of the BS-2 however, I'm still determining:


Kalinin K-12 STATISTICS:
crew: 3 people
Length: 8 / 10.3 m(33'-9.5");
Wing span 20.95 m (68'-9");
Weight: empty 3210 kg / (7076 lbs)
maximum load 4200 kg; (9286 lbs)
Engine: 2 Shvetsov M-22 ( under license of the British, Bristol Jupiter VI.)
The Soviet had the following characteristics: radial 9 cylinders 480 hp 353/358 kW ;
Speed: maximum 228-240 kph (141-150 mph)/ cruise 189 kph (117 mph);
Autonomy 700 km ;
Maximum flight altitude 7170 m;
Armament: 2 7.62 mm guns, ShKAS (Shpitalnyi-Komaritski Aviatsionnyi Skorostrelny), 7.62 mm caliber;
Cartridge weight 9.6 grams.

The designer would probably have both ShKAS variants:
1932 ShKAS - Fire rate 1800 projectiles / minute; Initial projectile speed 775/825 m / s; Weight 10.6 kg; Length 810 mm; Pipe length 585 mm; Model 1937,
Ultra-ShKAS - Fire rate 2500-3000 projectiles / minute; Initial projectile speed 825/870 m / s; Weight 18 kg; Length 935 mm; Pipe length 605 mm,

500/800 kg of bombs.

It's neat how the soviets solved the pitch issue with flying wings using the offset reverse airfoil instead of the base up-trim of the flaps like on the mini arrow.

Also that window in front makes this plane PERFECT for FPV! :cool:
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#6
REFLEX!!!!!!!

A great word and an often misunderstood concept. There was a great deal of research into airfoils for tailless operation and a suite of beautiful and graceful reflexed airfoils derived but reflexing itself is just the generation of a secondary high pressure zone at the rear of the wing.

I have been told by some that flat bottomed wings and even symmetrical wings will not fly because they are not reflexed! Well guess what, I fly wings and tailless designs with a mixture of different profiles from flat bottomed KFM designs through to fully symmetrical tailless designs.

Actually any wing can be flown tailless as the reflex can be supplied by the angling of the control surfaces into an upwards direction and thereby supply the REFLEX. (The same way an upwards deflected aileron causes a decrease in the total wing lift by creating an area of positive pressure at the wing rear portion).

There are only two things that you must be aware of in flying a wing as either a flying wing or a tailless design and they are getting the CG balance point correct AND that narrow cord wings can be difficult to control because of the small distance between the lift centre and the reflex pressure centre. The smaller the distance the more difficult to control or balance.

As a result of the Reflexed control surfaces the wing will not generate the same amount of lift you might expect from the wing if used in a conventional design I do recommend that you keep the build reasonably light as increased weight requires increased reflex angles on the control surfaces and actually reduces the wings overall lift capacity, especially if the craft is a tad nose heavy. Apart from that it will fly and fly really well!

You have a fan of your choice and possibly of your design when finished.

Have fun!
 

Namactual

Well-known member
#7
Wow, I do not think I have ever seen a better match with that combination of air frame and paint scheme. That is one odd looking duck.

I can not wait to see it fly!
 

FoamyDM

Building Fool-Flying Noob
#8
I'm not entirely sure how exactly to "calculate" reflex. With the Mini Arrow, its just... mostly level and adjust trim in flight.

I am a structural engineer, so I understand how to balance forces... however, not sure how to determine the lifting load on the various wing portions. I know there are sites and I will use them, however, I still don't entirely Grok. and I would like to avoid the cargo cult thinking symptom I am prone to when understanding wing life formulas. While the just-fly-it method will be how I likely will work it out. I'd like to understand the balance

 

Hai-Lee

Old and Bold RC PILOT
Mentor
#12
I'm not entirely sure how exactly to "calculate" reflex. With the Mini Arrow, its just... mostly level and adjust trim in flight.

I am a structural engineer, so I understand how to balance forces... however, not sure how to determine the lifting load on the various wing portions. I know there are sites and I will use them, however, I still don't entirely Grok. and I would like to avoid the cargo cult thinking symptom I am prone to when understanding wing life formulas. While the just-fly-it method will be how I likely will work it out. I'd like to understand the balance
Reflex is such a huge topic that we could easily hijack this thread and so I will avoid the indepth and simplify to where hopefully many will understand.

The biggest misunderstanding is that persons see the underside curvature of a classic reflexed airfoil and think that such a profile is compulsory to perform as a flying wing. Unfortunately the same persons forget that the majority of effective lift from an airfoil is due to the top surface and the partial vacuum created there, (90+% of the lift).

If you understand the idea of a lift centre in a normal. (conventional), wing setup, and that it is due to the accelerating of the air over the top surface of the wing then you should also understand the basic concept of pressure increase due to decelerating the air as well. When an aileron is raised the air flowing over the wing is effected and slows down in flow rate, though at the change in direction of the airflow direction due to the aileron leading edge the air slows greatly and changes direction abruptly. This slowing generates a relatively high pressure area and this high pressure causes a loss of total lift in the wing.

To understand the concept of balance just consider the conventional aircraft layout where the wing generates the majority of the lift and the tail provides a small corrective, and variable, amount of lift to control the attitude of the plane at a great distance from the wing lift centre, (point of attitude rotation). Now take the corrective forces setup and consider that the rear wing reflex takes over the function of the tail lift, (control), albeit over a much shorter moment. Unfortunately the tailless corrective forces are interactive with the overall wing lift as well:rolleyes:.

With the setup of a conventional aircraft the Weight is best balanced over the lift centre of the wing or slightly forward thereof. Well surprise! The balance of the tailless aircraft is exactly the same BUT the tailless arrangement does not give the ability to have different incidences wing Vs tail as often used on high lift aircraft and so the entire wing must be set at a higher incidence and the reflex increased to maintain that attitude. This is often achieved by varying the CG point WRT the wing lift centre. By pushing the CG further forward the reflex is increased to give a greater force at the rear of the wing and a leverage balance is setup between the three points of interest. The weight, (CG), the Wing lift centre, and the reflex control force, *the balancing force".

Just to confuse matters further the reflexing force does not need to be connected directly to the wing as long as it redirects airflow and provides an area of pressure, (variable), at, or, very near to the wing TE.

You can send yourself rather insane chasing every variable just remember the concept of bringing the tail forces to the rear of the wing and you will soon see that any wing that flies can be used as a flying wing, (reflexed).

As for the plane which is subject of this thread I suspect that as a wing the CG would definitely have been within the area of the bomb bay, (load), or else the trim changes would have been traumatic when the bombs were dropped.

Have fun!
 

FoamyDM

Building Fool-Flying Noob
#13
As I've been digging around the second double fuselage K-12 i think is acutually a Belyayev DB-LK. but I found a model kit for the infamous Kalinin K-7 (coined by me as the flying battleship) I learned 2 things... it was a political rival that got Kalinin arrested, and there's a fighter concept plane SAM-7 that has nearly the same look... maybe picked up Kalinin's design thoughts... dunno.

anyway here it is:
image277.gif
image279_2.jpg

I work with CAD most days and am relatively adept at scaling images, and tracing with p-lines... question is how well will it come together. I'm no good with flattening curves. :eek:

Hai-Lee you are welcome to expound on flying technical stuff ALL over this post. Your explanation of forces and their balancing was great. So I know I have it right, it's the redirection of air against the flat side of the reflex wing from the generally downward flowing wing's trailing edge that effects the force on the reflex wing to generating a counter rotational moment about the CG to balance it all out. I was going to try my CG at the Bomb bay doors first as I would put the heaviest load at the CG to keep it simple. :p As always thanks!

Side note, I love the BICh-17A...


These all remind me of Nausicaa of the Valley of the Wind's flying wing, and the K-17 reminds me of the Pejite flyer
, and the K-7 vaguely of the massive flying wings that crash in the valley as the haul the God-weapon-head-thing. I thought Miyazake was orignal, turns out he was delving deep into the Russian WWII X-plane archives. :D
 
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FoamyDM

Building Fool-Flying Noob
#14
Enjoy the progress photos... Coffee too late makes FoamyDM... Build planes?!, Don't mind if I do. :)


It's coming together nicely. I taped the wing shut for now to see. More this weekend. Night.
 
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PsyBorg

Wake up! Time to fly!
Mentor
#18
Thank you sir.

Looks like an Aeroplane to me!! Gettin close to tossin in some motors and electronics too. :applause:
 

FoamyDM

Building Fool-Flying Noob
#19
@Psyborg - Yup. i'll pull my AircPirates Sea Duck motors pods and load 'em up after it's wired. It's supposed to be rainy here so I hope to have it ready to test by the end of the weekend.

Be prepared for updates!
 

PsyBorg

Wake up! Time to fly!
Mentor
#20
Cool!! be sure to make bomb racks.. I posted hand drawn diagrams for the bombs so someone who is good at auto cad can do them proper and put them in pdf format for everyone. I will do final testing on some tweaks this week end and get build write up to go with them.