Fuselage rib 8 with stiffener and shim

I have been looking at simple and lightweight ways to ruggedize the Sling 2 tail structure against inadvertent impacts on the tie down bracket. The club Slings I fly all have evidence of such impacts, including cracked skins in the vicinity of the bracket loop. I know of one severe instance caused by two people mounting the step (against procedure) - the impact on asphalt was severe enough to push the bracket loop partially in. The damage included detachment of the channel RF-CHL-004- and longeron RF-LGN-801- from the skin, damage to the skin itself (possibly the cracking referred to), and presumably a crumpling of the rib RF-RIB-801-.

I have fashioned a new part from 3.2mm 6061-T6 which attaches to the rear face of rib 801, which adds strength to the lower part of this rib where the tie down bracket RF-BKT-010- is attached.  This part extends upwards and couples to the 3.2mm thick angle 8 RF-ANG-008 via multiple rivets (will use 4x13mm rivets here). This new part weighs just 70g.

With this arrangement, any impulsive forces applied to the tie down bracket will be transferred via the new part, to angle 8, and onto bracket 9 RF-BKT-009 which secures the rear channel of the horizontal stabiliser. The idea is that such forces will be directed away from the more delicate structure of the longerons and crumpling of rib 8 will be avoided.

One concern that comes to mind is that impulsive forces (associated with a tip-over onto hard ground, caused by two people on the step) to the tie down loop were previously absorbed by the skin, longeron attachments, and rib 8 albeit with damage. The horizontal stabilizer is not subjected to a high deceleration owing to the "crumpling" of these components.  With this modification such impulsive forces will be more directed to the horizontal stabiliser structure, causing a more intense deceleration of the horizontal stabiliser. The tendency would be a momentary downward flexure of the horizontal stabiliser. The concern is that the HS may be damaged - clearly a far worse outcome than a bit of crumpling of the lower parts of the tail skin etc.

This concern is eased as I plan to attach the new tail skid that has been developed by Sling. This rubberised items will largely shroud the tail hook and prevent impulsive contact in most forseeable circumstances.