I investigated various ways to stiffen the arm rests. Lots of options, and lots of opinions. I think there is a trade off between: weight, labor time, stiffness, cost, asthetics. I decided to just put an angle on the inboard edge to stiffen it. I used the ruined F-719 angles that I had left over which I think is 0.062 3/4 X 3/4angle. I trimmed one edge down to 5/8 so it wouldn't hang out below the arm rest flange.
I used the side skin to drill holes intothe angle and then used the angle to drill the arm rest. I countersunk the holes and used flush rivets to install the angle on the arm rest.
I clecoed the new stiffer arm rest in place and tested it with pressure. It is stiffer, but not solid. I think it will withstand getting a kink from an inadvertant heavy elbow or foot. But it probably won't hold 180 pounds stepping in. I think this meets most of the requirements. On forum guy said, "would you rather have a kink in your side skin?" I guess he is thinking if I make it to stiff and someone steps on it the side skin will buckle so better to have a flimsey arm rest buckle.
Well, I think slightly stiffened with angle is a good compromise. It will stand up better and probably still fail before the side skin does.
