Repair revisited

This blog cover the additional work done to the repair damage created in transit from the airshow.

Overview

Best not talked about

Final inspection of the repair displayed unacceptable gaps between the skin and the rib at two locations.

Initially packers were added but the realization was reached that application of rivets created all types of issues

I had been too optimistic after the repair and now had to accept this task was at the limits of my ability but it had to be fixed to my satisfaction.

Rework
A lot of time was lost rethinking on this issue and putting pride aside this was as a tough job as this builder has ever undertaken. 

After a lot of soul searching it was decided to remove the tabs that were creating the issue's and rivet new ones on. This position was reached after fitting the skins to both sides, inspecting the fit it was concluded the core of the issue laid in the curves.

With the rib exposed the curved tabs were removed and dressed then a replacement set fabricated. To allow the component to be fitted the side was cut creating tabs on the mating faces and these were then drilled allowing three [3] rivets to be installed at the top and bottom with a couple in the middle. 

The original full length stringer doubler was replaced with two [2] 0.025'' 2024-T3 custom folded channels. These were tapered on the flanges and staggered to each other to create a smooth path for any loads to transfer between members. The flanges were riveted to hold the assembly straight while lining up the members.

New outer flange

Top fixing of new bulkheads

With the part ready the tab was slid between the bulkhead web and skin and with the location marked onto the web, next the holes were drilled and all the components clecoed to the bulkhead and then riveted. The operation was repeated until all bulkheads were modified, finally the skins were fitted but it was difficult to drill the align ribs for drilling from the skin side one skin had to be off to allow the necessary drilling to be undertaken. 

To create access the damaged port skin was cut open near the rib and fitted to the starboard side and that access allowed the operation to be repeated on the starboard side.

This is one idea that allowed the positioning of the rib correctly for pre-drilling

The jig was manufactured using the damaged skin, match drilled using the new skin and fitted to the aircraft, holes for the rib could be drilled, position checked
through the whole process.

Note: Each check involves the installation and removal of one of the side skins multiple times not to mention the installation of both skins to confirm alignment which consumed the better part of each day given to each task. A jig was developed as a result of the time lost doing this and not begin able to reach the rib to control its position for drilling

Blue Stuff
The aircraft was leveled using the water tubes  at points along and across the fuselage plus the the elevator stab with a small amount of weight applied on the elevator stab to tweek the alignment before riveting with the final task to pull rivets.

Note: Both skins are clone's of the original factory skins with all factory pre-drilled holes reused.

Mid-night and the lower skin's are installed
with the next skin to be installed for riveting

The final task next week is one final check, remove clecos and fill all the empty holes with pop rivets. 

Comment
How a small amount of damage in real terms had cost the builder 75+ hours of work. rework and more rework is hard to fathom. That this much time could be consumed and not achieve perfection is beyond me but the task was like a game of chess, every move had significance with unseen consequences and with each move, options reduced in a game with no visible guidelines.

The description of the work is at best in this case an overview and dose not go close in covering the time lost in fitting, re-fitting, checking and re-work.

Ready to close