KFSS Butt Ribs

[MotReklaw]

KF'ers,

I have a question about the butt ribs, which I'm in the process of installing.

Which way should the butt ribs be turned, flange outboard or flange inboard?
I've noticed several photos here that look like the flanges are turned inboard, or maybe I'm not understanding the instructions in the manual.

Many thanks,

[Geowitz]

It seems that some people were turning them around to make the flange on the outside as they thought it made it easier to install the windshield and fabric. I believe the direction was changed in the manuals to reflect this. But basically, they can go which ever way you prefer. Older models generally face in with newer ones facing out.

[HighWing]

I think George is spot on. My current project has them on the inside per the early manual, but I put nut plates in to compensate for the difficulty getting at the hardware. I would guess that if the rib is left bare - as mine are - the esthetics would be better from inside as well if the flange was out.
Lowell

[MotReklaw]

Thanks guys,

It makes sense to me and I will mount the ribs with the flange out. I will have to trim a bit off the brackets to get the required spacing between the butt rib and rib #1.

Thanks again,

[jtpitkin06]

I asked John McBean about butt rib flanges while at Oshkosh. He told me the factory instructions have shown it both ways and; indeed, the demo aircraft present had them in both directions.

There are reasons to do it in either direction.

If the flanges face out:


Skylight nuts are easier to reach.
Skylight nuts are hidden from view with the wings in flying position.

If the flanges face inward:


Skylight less likely to crack with screw holes further from the edge.
Fuel gauge visibility is slightly improved.

My flanges point out per the instruction manual. If I had it to do over I would point them in for a better position of the skylight screw holes. If the flanges point out there is barely a 1/8 inch between the holes and the edge of the plastic skylight.


John Pitkin
Greenville, TX