how to determine wing size for an airplane

[eatU4myT]

1 hour ago, Moach said:

place the CoG somewhere between 25% and 33% of the mean wing chord

Interested to know if this really applies in KSP, when the lift generated by a wing is not a function of its shape, just a number assigned by the devs?

[king of nowhere]

1 hour ago, eatU4myT said:

Interested to know if this really applies in KSP, when the lift generated by a wing is not a function of its shape, just a number assigned by the devs?

i'm mostly eyeballing it and going by trial and error, so we'll never know.

what i'd be curious to know is what would happen in reality if you put two wings one on top of the other like i did to gain some lifting surface. aerodynamics must be pretty rough around it. though biplanes actually had that setup, so maybe it works better than one would think

[steve_v]

28 minutes ago, king of nowhere said:

biplanes actually had that setup, so maybe it works better than one would think

Biplanes work fine at low speed, but they suck camel-balls if you're trying to break the sound barrier. Even if you could get one up to such speed without it tearing itself apart, the drag would be horrendous.
There is a theoretical design floating about somewhere, but IIRC nobody has actually built one.

In KSP it doesn't matter in the slightest, since stock aero models neither supersonic wave drag nor wing interaction. For that you need FAR.
All stock does is add a magic drag-multiplier at the sound barrier.

TBH this is probably the thing that annoys me most about the games aero model - there's no penalty for stacking wings, or even clipping them inside other parts. There's also no area ruling, no shockwave modelling, no drag occlusion for anything but cargobays and fairings, and a ludicrously forgiving stall mechanic.
Even horribly unrealistic designs (like WW1-esque biplanes) can reach hypersonic speeds in KSP, and many realistic ones fly like bricks due to counter-intuitive artefacts of the simplified drag system like the uber-drag from open nodes. 

Edited September 2, 2020 by steve_v

[king of nowhere]

ok, the first flight test was ended for lack of battery power. the second ended at 3000 m of altitude when i crashed into the side of a mountain (testing by night has limitations). i identified the source of the torque as all propellers accidentally turning in the same direction, and i retified that.

third test was promising. until 5000 meters, the plane fly itself. it climbs steadily at 10° without need for touching the commands. above that, it tends to lean downwards, but it is still possible to climb at 5° until 9000 meters. it's possible to go even a bit higher, but at this point i was fighting the controls, and i just got tired of trying. so i decided to test rocket flight.

the results there were less promising. as soon as i turned on the rocket, the plane started to turn in all directions. holding prograde was pointless, i had to do it manually. worse, it had a distinct tendency to point the nose upwards. if left to drive by itself, it would perform a full 360° turn. in the end, the 2500 m/s of fuel only allowed me to reach 25 km of altitude with a speed of 250 m/s. i need get the plane higher first, and then to find some aerodinamic fix.

i also tested it in water, and it can move around. it can't take off, but it can reach land.

EDIT: i also tested atmospheric reentry, and i really need to use the rockets to brake. even the wings don't survive the heat, much less the rest of the fuselage

Edited September 2, 2020 by king of nowhere