Thank you very much, AlexC.
The first step is to use one matching drawing of the blueprint for each of the three orthogonal views. This can be done by simply taking a screenshot of that area and using the image or by creating those "crops" in Photoshop.
They have measurements in them, which I placed into the cube. From there, each view can be scaled, offsetted, and rotated if needed. While you click on the top bar of each view to have them active, use "Shift + v" to get into the dialog (Attributes)
The second step is to start with a simple Bezier curve (two points only and "drag" the mouse for each point to get longer handles.
Start in one view to define a quarter of the "bow", then go to the next, and then to the third. Typically, you have to go through that routine at least twice.
If that spline matches a quarter of the construction, You can use the Symmetry Object to get two and another to get all four.
The current State of the Object for each Symmetry will result in four Splines that cover the four. I connected two each time and copied it vertically in the middle while scaling it down.
I noticed that three do not define the shape well, so I created two more copies and rotated those (Spline 1 2 and Spline 1 4). Rotation is performed by selecting all points of a single Spline, then using the Rotate tool and adjusting the Axis in Attributes in X, Y, and/or Z to achieve the desired rotation point.
I hope the first file I shared helps to support seeing those steps.
All the best