Question about welding wings - sorta answered

[ThirdHorseman]

Did some searches of the forums but didn't find anything definitive...

I'm trying to create a lifting body design made from welding 32 Wing Connector Type A wings into a tube, 8-wings to a side:

I made sure to put the "Module=winglet" section in the opening of the PART.CFG file:

PART
{
// Kerbal Space Program - Part Config

// --- general parameters ---
name = WingTypeA-8xLongTube
module = Winglet
author = Me

I set the attachment rules, editor parameters, and standard part parameters (mass, dragModelType=override, etc). I also made sure to put in the "winglet parameters" section:

// --- winglet parameters ---
// dragCoeff will override the maximum_drag value
dragCoeff = 0.5
deflectionLiftCoeff = 2.0

My question is, what should the "deflectionLiftCoeff" be? I probably shouldn't just do 2 * 32 = 64 because half of the wings are rotated 90degrees so I assume the lift is less. Would it be something more like:

(2 * 16) + (1 * 16) = 48

assuming you halve the liftcoeff for wings that are rotated 90 degrees? That still seems like a lot of lift, but it's a lot of wings so maybe that makes sense...

Anyone have any ideas or thoughts, or can point me to the correct info? Thanks!

Edited November 10, 2014 by ThirdHorseman

[Daffs]

Just an idea (non coding/editing), Mr Overfloater has several SSTO's with large cargo bays built like this, he just struts the wings with an X join between each wing. There's a video on Youtube. (don't know if I'm allowed links so search '[KSP] Astroliner VIII "Nova" SSTO - construction' it's at 10:54 in the video).

[numerobis]

Would it work to just weld one side together, and use four parts? Otherwise you can't replicate the lift characteristics.

[ThirdHorseman]

Yea I originally built it out of 32 individual wing connectors, all strutted to hell and back, and the part count killed my laptop. I tend to weld the large-count parts just to keep the part count down, but this is the first time I've played with wings.

Same goes for just welding one side...after you put in enough struts to hold the whole thing together the part count gets too high.

Is there a mod like Kerbal Engineer that shows lift ratings for ships? I could just build the part using 32 individual wing connectors and then look at the total lift value, then just apply that to the part? Or I'll just stick to using it as a structural piece, give it like a 2 or 4 lift rating, and call it a day...

[numerobis]

Technically you're asking for an impossibility: the 32-wing assembly has wings pointing perpendicular to each other, so there's going to be inaccuracy in your translation to a single winglet part.

What probably makes the most sense is 16x the lift, and 32x the mass. Then, when you're flying straight and pitch up, you'll get pretty much the same characteristics (minus flexing).

Where you'll differ is if you yaw. The 16 boards on the sides would then produce lift and either stabilize or amplify the yaw, depending what side of the center of mass they're on. But in your merged model, nothing will happen, no matter what you set the lift value to.

(Unless the merged model has its "right" vector the other way, in which case you'll see no lift but a strong yaw effect.)

[Kryxal]

Maybe consider merges of 8 to retain the proper characteristics?

[ThirdHorseman]

For the record, I just set the lift as 16 (2.0 * 8). I figured the two side rows won't add any lift, and since one side each for the top and bottom row would have access to airflow, they would cancel and act as a single wing (high pressure underneath the part, low pressure above). So 16 doesn't feel cheaty to me.

I'm gonna mark this as Answered, but I'd really love to see more engineering data for these kinds of parts. It's really hard building spaceplanes...which have had their importance increased dramatically since Funds! were introduced...without knowing the actual aerodynamic information. I'm seeing lots of people putting in wing connectors that don't add any lift, or doing things to the lift vector that doesn't make sense. It would be great to have a readout that shows total lift amount along with the vector...

[numerobis]

The lift vector depends on your direction. In the SPH, the lift vector is calculated with airflow coming at you. Click the root part (usually the cockpit) and rotate the plane using shift-wasd. You'll see the lift vector (and the center of lift) change in response to the angle that you're making with the airflow.

I agree it might be nice to have a window where you type in altitude and speed, then it spits out the magnitude of the lift vector, taking into account the current rotation.