Bell P-39: Fold Over Flange

Technote: Bell P-39 Fold Over Flange.(Inventor 2017)

This a quick technote to highlight an issue that we sometimes come across with creating flanges in Inventor when one part is sloping away from the other.

The part we are working on is shown on this scrap view from the Bell drawings. This flange is folded over onto a sloping top plate from the side plate that is at an angle of 105 degrees.

P-39 Oil Cooler Main1

The issue relates to the reference edge selections that will determine whether or not we obtain a smooth transition from the side plate to the new flange.


When I first did this I selected the outside edge of the side plate to align the flange sketch. This was not satisfactory due to the notches; that are perpendicular to the side plate; influencing the creation of the eventual flange bend which gave us a rather awkward and untidy bend transition…definitely not good.

So I recreated the sketch; this time aligning with the inside edge of the side plate; which resulted in a smooth transition bend to both notched areas as shown below.


Occasionally when creating flanges the selection of which edge is referenced can make all the difference in achieving a satisfactory result. Use the sheet metal Face command to create a flange based on a 2D sketch as we have done here.

I should note that those notches are bigger than they need to be at this stage. I normally develop these complex models using a generous radius until I have completed the construction. Once I have achieved a satisfactory model and everything aligns correctly then I can go back and adjust these notches to a minimum size.

Progress Update:

I have included the rear fuselage section contour lines for reference. Will probably have to leave this project for a few weeks as I really need to spend some time sorting out my garden that is slowly resembling a jungle!

P-39 Aug21

37mm Gun Mount & Rudder Cable Guide Pulley.


About Hugh

BIM & Cad Manager/Strategist, 3D/4D, multi-discipline cad workflows, integration. Interests include photography and historical aviation.
This entry was posted in Bell P-39, Inventor, Sheet metalwork, Technote, Uncategorized and tagged . Bookmark the permalink.

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