1.0 Hours -
One of the things I really like about the RV-7 kit is that almost all the parts are cut to size and pre-punched. For someone like me, with no previous building experience, this level of completeness is what allows me to enter the field in the first place. The few parts that must be fabricated by the builder are usually small and simple to make. The wing walk doublers were no exception.
The doublers are simply a second layer of skin on the upper, inboard wing surface that help reinforce the wing where people will stand when entering/exiting the plane. Where all the other skins are sheared to size and pre-punched, Van’s simply supplies two sheets of AS3-025×9 3/8×26 aluminum. Unfortunately, the sheets are closer to 10” x 45” and must be cut down to the size listed in the plans (9 3/8” x 26”).
Looking at other build sites, there was a mix of people that cut the sheets to the size in the plans and people that left the width as 10”. Not cutting one side seemed appealing, so I simply cut the sheets to the proper length and left the width as 10”. Read on and you’ll see that I decided to trim the sheets to the width in the plans.
Initially, I cut the doublers to 26" x 10". Later, I narrowed them to 9-3/8" as called out in the plans due to edge distance for one hole.
The doublers are placed on the underside of the W-702 skin so they can be match drilled. The inboard edge of the doubler lines up with the inboard edge of the skin, and the forward edge of the doubler sits 9/16″ aft of forward edge the skin so that it does not interfere with the spar. After marking a line 9/16” aft of the forward edge, I lined up the doubler and used duct tape to make sure it stayed in place when I flipped the skin/doubler over.
After marking the back of the sking, I taped the doubler in place at the proper distance from the forward edge.
The doubler must be 9/16" back from the forward edge of the skin so that it does not interfere with the forward spar's flange.
I then proceeded to match-drill the doubler using the holes in the skin as a guide. I used clecos to clamp the assembly to a piece of MDF as I drilled. This also ensured that the pieces were staying in proper alignment.
I matched drilled the doubler using the holes in the skin as a guide.
After I finished drilling, I separated the two pieces to inspect my work. Everything looked good except for one hole in the doubler. The aft, outboard-most hole was very close to the edge of the doubler. In fact, it did not have proper edge distance and I was worried that the metal would warp near the hole when it was dimpled. To fix this, I decided to cut the width of the doubler down to the prescribed 9-3/8”. Trimming the extra 5/8” off the doubler fixed my edge distance problem by completely removing the problem hole.
One doubler fabricated, one to go.
One down, one to go.
