In this example, we start with an custom design WWII type fighter aircraft which has a commonly used geometry of its fuselage.
Techniques may vary depending on the geometry being worked on.
However, this model could be useful for ones related with aircraft modeling.
First, we decide where to cut (Trim Surface) on the fuselage and with which profile. In this example we start with an already cut fuselage which its cut borders are indicated with arrows.
Because we cut with a sketch composed of several curves and lines, the cut border created on the fuselage does not have a continues edge along the border. So we need to create "Combined Curve" in order to use the whole edge as one continuous edge when connecting with other geometries.
The created combined curve is indicated with an arrow. We just used one half of the geometry.
Now we need guide curves in order to have more control and precision on the new surface to be created.
Please pay attention to "Curvature Continuity" propagation within end points of the splines with connecting surfaces.
We use "Boundary Surface" tool in surface commands. You can see how all our guide curves, combined curve and the edge of the wing is used.
It is time draw the bottom line curve in side view. This curve is pretty much important in our following steps.
Please pay attention to "Curvature Continuity" propagation within end points of the spline with fuselage surfaces.
Here we need another guide curve coming from the wing to our center line, which we called it as bottom line curve.
This spline is essential in order to perform Curvature Continuity between the wing and the fuselage!
We use Boundary Surface tool again as shown below.
Here is the result of the completed boundary surface.
Now we need to trim this Boundary Surface! Why?
We need to open a space for front and rear part of this boundary surface in order to be able to connect with the first surface at the top.
Pay attention to trimming curves not be tangent to the border edge in the bottom view. On the other step it will be much clear, shown with arrows.
You can see the remaining areas left from the "Trim Surface" operation.
These remaining areas are vital because we need a tangent/curvature continuity between the upcoming front and rear boundary surfaces with this bottom surface.
Here comes the front surface! Again we use boundary surface tool.
Now we will use "Knit Surface" tool.
And comes the rear surface! Again we use boundary surface tool.
Now we have connected the wing with the fuselage.
From now on, you can Knit all surfaces we made with the wing and mirror it to other side.
Another view from upper part of the connecting surfaces.