Side Skin Install Part 1

I’ve been falling behind on regular posts, but I intend to return to a regular rhythm — if not daily, at least on the days when I work on the plane.. So, this post is a little longer as it captures work performed 8 – 13 July.

I’ve started to attach the right side skin to the fuselage. I measured and cut the insulation, making pieces for both sides at the same time.

I dimpled the forward part of the skin. This is optional for the Sling 4, but standard for the TSi. It may help performance a tiny bit (fewer drag counts), but mostly I’m doing it for appearance’s sake. Countersunk rivets sit flush with the skin when installed in the dimpled holes, rather than sticking out like the normal button-head rivets. To dimple the holes, I’m using a pop rivet dimpler for the skins, and a vise dimper for the longerons, and other places where space allows.

Attaching the insulation pieces before pinning the skin onto the fuselage
Vise grip dimpler for the longerons

I decided to install the NACA scoop before attaching the skin to the fuselage. Rather than using Sika sealant recommended by the manual (hard to get in US), I’m using Dow DOWSIL 732 RTV Sealant, which is very easy to obtain here. As indicated in the (TSi) manual, the holes for the NACA scoop are also dimpled. You can’t dimple composite material, so instead I took a countersink drill bit to it. However, the flanges were so thin, it just enlarged the hole, so I made some reinforcement strips from 0.020″ Al sheet and dimpled those too.

Skin dimpled for the NACA scoop
Reinforcement straps for the dimpled holes where the flange was very thin
I applied three thin outlines of 732 sealant
Appearance after initially setting the flush rivets – the sealant spread out nicely
After cleaning up the excess sealant
Installed scoop as viewed from the inside
I cut away an appropriate amount of insulation to work around the scoop
Skin attached with a few clecos for fit check
NACA scoop looks like it’s installed correctly
Spraying primer onto the skin where the stiffener plate attaches
View of the installed skin from the inside

I also completed a few small miscellaneous tasks: fit check of the seat belt reel (for front seats), designed & printed a seat belt grommet for the longerons, and drilled a hole in the skin for -3AN bulkhead fitting for the brake line.

Hole drilled for the -3AN bulkhead fitting – a stainless braided brake line will attach to this
My custom grommet for where the seat belt webbing passes through the longerons inside the wall

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