Fuselage Panels

NAA P-51D Mustang: Front Fuselage

Following a recent inquiry, I have revisited the NAA P-51 Mustang project to develop the front fuselage and cockpit. This will be an extremely detailed and accurate model including fixings and rivet holes.

P-51D Early.png

The partial structure above is for the early P-51D version; note the instrument panel and support frame. There are also some minor differences with the other components, most notably the curved beam which has different end brackets for the early and late versions.

The 2 instrument panels depicting the P-51D versions, with the later version on the right. This will be a medium to long term project for which I will post regular updates.

Technote: Positioning Holes in Complex Surfaces

When detailing the skin panels for aircraft it can be quite daunting trying to locate a series of holes accurately at a specified distance from the edge of the panel. Typically fillets to wings and horizontal stabilizers and transition pieces to vertical stabilizers are all complex surfaces.

In this example, we need a series of holes located 17.5 mm from the top and bottom edges. As you can see the surface at the top and the flange angle at the base varies.

The location of the first hole, top and bottom, is aligned vertically so we first create a workplane to determine the horizontal position of the first hole. Ultimately we will use a 3d intersection curve for the centre line of the holes which must first be determined by sweeping a circle profile sketch along the edge as a surface with the radius set to the required edge distance. Using a circular profile for the sweep ensures that any intersection point on the surface will be at the specified edge distance.

This swept surface is then trimmed to the first work plane to define the start point of the 3d surface intersection curve as shown.

The resulting 3d spline represents the line of the hole centres at 17.5mm from any point along the edge of the fillet.

We then apply a point and an axis (perpendicular to the surface) at this point to determine the hole direction. I suspect because it is not a regular surface the hole feature will not allow me to select the surface for direction. Use “Extend Start” when creating hole.

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To pattern the hole along the spline and be perpendicular to the surface create the array as shown below. Be sure to select the extended options for “Direction 1” and “Adjust”.

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Do the same for the top array of holes, resulting in 2 sets of holes aligned with the surface at 17.5 mm from the edge.

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This works for the vast majority of riveted panel connections where locally there is a degreee of flatness between the matching parts. In instances, where there is extreme curvature of the connecting faces the radius of the extruded circle would have to be adjusted accordingly.