Recent inspection of the aft mid cabin, through the floor opening for the aft stick, revealed a unexpected surprise. There was a large amount of water accumulation at the F-806-1 Rear Spar Attachment Bulkhead Assembly. The aircraft had just been washed.
I drilled three drain holes in the area to drain the water and to ensure that an unnoticed water accumulation does not happen again. The weight issue could be significant as well as the fact that there is wiring in the area.
Today, after removing all of the floor panels, I ran water over both of the wings. I suspected that the water was travelling under the wing/fuselage fairings, down into the gap and onto the lower wing skin that extends under the fuselage where it is attached with screws. Then the water on this skin could flow under the F-815-1 R&L outboard seat ribs into the mid cabin. Sure enough, the water was flowing through the outboard ribs wherever there was a slit where each rib tab was formed.
Inspecting the wing fairings, the right fairing has obvious gaps between the fairing and the top wing skin. The left fairing is better but there is a gap where the front and aft fairing meet. I did not roll the outboard edge of the fairings. This might have helped push the outboard edge down against the wing skin when it is screwed in place but I really don't think it would be all that effective. The screw holes are near the edges and are dimpled. Dimpling can deform the edges.
I suspect the water accumulation in the mid cabin may be an issue specific to the RV-8A. The tail wheel RV-8, sitting tail low, promotes water drainage from the wing/fuselage interface. The RV-8A sitting much more level can promote water accumulation outboard of the outboard seat rib. For this reason, I will be applying a bead of chalk along all of the outboard edges that I can reach of the F-815 outboard ribs and to the inboard edges of the rib that are not reachable outboard. I will also try running a bead of RTV just inboard of the screw holes of the wing/fuselage fairings to try to stop the water from entering the gap.
If anybody has any other suggestions, I'm open to your advice. Otherwise, I advice other RV-8A builders to seal the bottom of the outboard seat ribs to prevent cryptic flooding of the mid cabin.
I drilled three drain holes in the area to drain the water and to ensure that an unnoticed water accumulation does not happen again. The weight issue could be significant as well as the fact that there is wiring in the area.
Today, after removing all of the floor panels, I ran water over both of the wings. I suspected that the water was travelling under the wing/fuselage fairings, down into the gap and onto the lower wing skin that extends under the fuselage where it is attached with screws. Then the water on this skin could flow under the F-815-1 R&L outboard seat ribs into the mid cabin. Sure enough, the water was flowing through the outboard ribs wherever there was a slit where each rib tab was formed.
Inspecting the wing fairings, the right fairing has obvious gaps between the fairing and the top wing skin. The left fairing is better but there is a gap where the front and aft fairing meet. I did not roll the outboard edge of the fairings. This might have helped push the outboard edge down against the wing skin when it is screwed in place but I really don't think it would be all that effective. The screw holes are near the edges and are dimpled. Dimpling can deform the edges.
I suspect the water accumulation in the mid cabin may be an issue specific to the RV-8A. The tail wheel RV-8, sitting tail low, promotes water drainage from the wing/fuselage interface. The RV-8A sitting much more level can promote water accumulation outboard of the outboard seat rib. For this reason, I will be applying a bead of chalk along all of the outboard edges that I can reach of the F-815 outboard ribs and to the inboard edges of the rib that are not reachable outboard. I will also try running a bead of RTV just inboard of the screw holes of the wing/fuselage fairings to try to stop the water from entering the gap.
If anybody has any other suggestions, I'm open to your advice. Otherwise, I advice other RV-8A builders to seal the bottom of the outboard seat ribs to prevent cryptic flooding of the mid cabin.
