Initial rear skin mismatch investigation

Prompted by the experience of another builder (check out P. Latten's blog) I laid out the rear fuselage skins on a flat surface to discover any gross mismatches. I was not disappointed, but it was unclear exactly what skin was to "blame". The problems seems to be centered around the top rear skin and the rear side skins, and possibly the side skins.

In Scheme 1 I matched the rear top skin to the side skin. In this case the side skins would match the middle top skins, all the way to the centre fuselage

In Scheme 2 I matched the middle top skin to the side skin. In this case the rear side skins would mismatch the rear top skin. The mismatches would be confined to the rear sections of the fuselage.

Other inputs shows that Scheme 2 was the relevant scenario, as made clear when the skins were actually clecoed onto the fuselage rib structures and longerons.

Between ribs 5 and 6 it is expected that the lateral misalignment can be largely addressed by upsizing and recentering to 4mm, and 4.8mm rivets close to rib 5

Between ribs 4 and 5 it is expected that the mostly vertical misalignment can also be addressed by upsizing and recentering to 4mm, and 4.8mm close to rib 5

The mixed nature of these misalignments indicate the error is not located in any one skin. A full fix would involve relocating holes in the rear top skin as well as the rear side skins.

Have discussed with Sling and they agree with the validity of such upsizing.

Subsequent fitting of the skins to the fuselage has shown that a certain amount of blending can be done, mitigating slightly the amount of upsizing that is required.