The bottom flange of the tunnel sides have a bead of Proseal applied during the riveting to the fwd lower skins. I think this is to guard against the ingress of oil etc into the cockpit.
So, in order to tame the Sticky Stuff Monster, out came the masking tape!
We were able to use the C-Frame to back-rivet most of the AD426AD3-3.5’s … as far along as the muffler doubler area …
… but then, due to the top flange, back-riveting wasn’t possible.
So having clamped and braced the tunnel sides, we used the gun and bucking bar for the last few.
Masking really helps to keep everything clean.
Next day, after the Proseal had set, we clecoed the sides to the tunnel top ready for riveting.
I found that by clamping the lower skins and tunnel top end to the bench, and by clecoing on the F-14132 Tunnel Angle at the front, the whole structure was quite stable & secure for riveting.
The angled end of a Tungsten bucking bar coped with the acute angle of the tunnel sides …
… but the last rivet was a real pig. None of my bars would fit in the very small clearance at the narrow end of the taper.
In the end we used the end of a screwdriver to start the set, using a spacer for leverage and brace. Once partially set, the smallest bar just fitted to finish off.
Once the tunnel top is riveted, a fillet of Proseal is run along each join at the top.
This was the easiest Prosealing so far : )
Masking tape again proving its worth!