Wing Modeling

[Mudhen15]

It shouldn't come as a surprise that most, if not all, modern aircraft are monoplanes, with one wing. I'd like to make a mod with a wing that follows this concept of having the entire structure as one.

Anyway, I don't know how to define things in the model at all, so I was hoping someone here could help.

[ColdJ]

On 10/31/2024 at 12:07 PM, Mudhen15 said:

It shouldn't come as a surprise that most, if not all, modern aircraft are monoplanes, with one wing. I'd like to make a mod with a wing that follows this concept of having the entire structure as one.

Anyway, I don't know how to define things in the model at all, so I was hoping someone here could help.

Hi, haven't been in this section for ages or I would have replied sooner.

In the KSP stock system there is a single point of lift per part. This is defined by the world origin in the Blender environment, so where your model mesh is situated in the  workspace compared to the world origin will determine where KSP thinks the point of lift is. But of course other factors like point of mass, centre of the fuel tank etc are also determined by world origin, so that is why the configuration files can have parameters added to adjust Centre of Mass, Centre of Lift and Centre of Pressure. The last one is determining where the drag will pull on the model. Nice easy example of this is the stock crew capsules. It is why they fall base first through the atmosphere when not attached to other parts that could override this

Here are the 2 lines in the "Mk1 pod_v2.cfg. They are for lift and pressure, they haven't bothered to change the centre of mass.

    CoPOffset = 0.0, 0.5, 0.0
    CoLOffset = 0.0, -0.35, 0.0

Note that they say "offset". Anything that you change with these uses the world origin of the model as it's starting point. So for most wings I would have the root of the wing at the world origin. This not only means that the mass of the part is close to the body if not changed in the config, but also helps with the way that "Unity", (the platform that KSP is built on) reacts. Unity does not like mass to be too far from origin because it treats it like you would hold something in the real world. If you pick up a sledge hammer and hold it close to the solid metal head then it is not too difficult to hold, but the further from the head you hold the shaft, the more strain on your wrist.

So, first to remember that the Y direction in Blender is the Z direction for KSP (X remains the same). So in blender if you look at the narrow end of the pod, it is pointing at positive Z. In the config files it is written

CoPOffset = X, Y, Z or -X, -Y, -Z if you are shifting along the negative axis. You can of course have positive and negative depending on where you want the virtual point in space to be.

So if spawned in the SPH. the X is the sides left and right, -X for left side. The Y is front to back Positive Y pointing towards the open hangar doors. The Z is up and down. Just to be confusing, -Z is up and positive Z is down.

So in the examples we can see that they have shifted the Centre of Pressure (drag) towards the narrow end and the lift towards the base.

As such the capsule falls base first and the base provides a slowing resistance due to lift.

 

Now that we have a knowledge basis to work from, we can see that generally we like 2 wings so as to spread our lift out. Each wing and the body itself get used in the lift equation. But you also get lift from elevons.

So if you insist that your model mesh must be just one part, rather than 2 that look like 1 when attached, then you must live with the lift being right in the centre of the plane and rely on the flaps to provide the stabilising lift out to the sides. Just remember that unless you config the flaps to have their lift forward of where they actually are, then your lift will be at the rear edge of the planes wing. This is fine on smaller planes, especially if you config the main wing to have it's point of lift further forward than it looks like it should, but might cause unstable flight for large craft like a big flying wing bomber.

Hope this helps.

Edited November 29 by ColdJ

[Mudhen15]

thanks! never knew how complex it was.