Bf109 – Aviation CAD TechNotes

Messerschmitt: Bf109 Ordinates:

I recently received an inquiry from a museum regarding ordinate datasets for the Bf109. As I previously mentioned in this earlier post the archive I have has a lot of data that was done by others…so I figured it was quite comprehensively covered.

Anyway, I decided to have a closer look and see what was actually documented and how well it aligned with known data. It turns out to be a bit of a muddle. Although the data is quite well presented I have uncovered a number of inconsistencies and anomalies which I will need to resolve.

8-109.000 G-2 Flugzeug Zuss 2

What I thought would be a quick response to an inquiry has initiated a much more intensive study which admittedly I had not planned for. I will go back to basics with this one, using the existing data as a reference and develop a new set of ordinate data for the Bf109 similar to how I approached the Mustang P-51 project.

I have already started with the Horizontal Stabiliser and part of the way through the Vertical. The tables will essentially be a reconstruction from the Messerschmitt drawings and then compiled to develop the X, Y, Z ordinates for transfer to CAD.

bf109

Messerschmitt: Bf109 Part

Scans of the drawings for the Bf109 have long been part of my archive, but I was always reluctant to spend anytime on this aircraft as many others have already done a great deal of work producing CAD data from these designs.

However and occasionally I come across an item that presents a challenge and this part is one of those.

8-10910-2501: Lower Frame mount.

This is a cast aluminium part with a 3 degree draft on all faces (refer second image showing cross section) except the lower edge and the top edge on centre.

The challenging aspect of this part has to do with the top face, where it was important to achieve tangency with the draft faces at each of the mounting holes and maintain this through to the centre portion where the face locally is perpendicular.

The material thickness also increases marginally at the extent of the 2 inward holes.

The front edge of this face has a center portion of a fixed radius; so to achieve the desired results based on the above criteria for the back edge I used a tangential spline. I could have just used a radius arc instead of a spline as the difference was only 0.2mm, but I am keen to get this stuff as accurate as possible.