Yesterday, the forward wing tip rib was dimpled for flush rivets, today the aft wing tip rib was dimpled and an access hole was cut in the wing tip bottom skin for the wing tip navigation/strobe lighting, followed by the bending of all the tabs to the required angle. Followers of this RV-12 build will remember the dimpling of the aft wing tip rib is challenging, but made easy with a method conceived by the DOG Aviation think tank.
The dimples are easily made by using two dimple dies back to back with a washer placed between them INSIDE the rib and a specially fabricated nail to hold the dies in alignment. As the pneumatic squeezer’s piston pushes outward the male tip on the die pushes the nail into a yoke without a set as the dimple is being created. A washer with tape on it is placed between the yoke and the rib to prevent the yoke from marring the rib. This works great!
the opposite side so a dimple can be made on the opposite side of the aft wing tip rib.
One side effect I forgot to mention when discussing this process for the left wing is the rib will become slightly deformed because the rib is a U channel … all the dimples will put a small bow in it which needs to be corrected by a little fluting. Builders attempting dimpling of their RV-12 please take note: The aft wing tip rib has a natural bow or curve to begin with … however, the web of the rib which will be the outer edge of the wing needs to be straight and flat but after dimpling, it takes on a small curve as well. This small curve is easily taken out by slightly fluting the rib. Before dimpling, the natural curve of the aft wing tip rib was traced onto a piece of cardboard … after dimpling and the follow-up fluting, the curve can be verified to be close enough to move on.
This is the curve that is normal for the wing
tip rib.
While holding the web of the aft wing tip rib onto
the edge of a table, the rib is fluted as necessary at the location the rib departs
the edge of the table. This will take the curve/twist out of the rib … small
amounts of fluting are done to both sides of the rib. This rib is almost
perfect now.
After the aft wingtip dimpling was completed,
work started on the bottom wing tip skin. Because there will be a
navigation/strobe light installed on the wing tip, an access hole needed to be
cut into the W-1204D-R bottom skin. The template for the cutout was placed on
the skin and the outline for the hole traced onto the skin and then cut with a jig
saw.
Drilling holes with a step drill to allow access
for the jig saw.
Cutting the wing tip light’s wiring access hole
into the W-1204D-R
bottom wing tip skin with a jig saw using a 24 tooth per inch
blade.
Smoothing the freshly cut wiring access hole in
the W-1204D-R skin with a ScotchBrite wheel.
The last task of the day was bending all the
tabs on the W-1204D-R wing tip bottom skin to the specified angles. The same process
that was employed on the left wing to verify the tab angles using a digital
level was employed again. First the digital level is placed on the plane the measurement will be
taken on ... then the bevel button is pressed to zero the level to the slope of the
workbench. The tab is bent to the specified angle using the tool Van’s has the builder fabricate
from wood ... then the angle is verified with the digital level.
Using the specially fabricated bending tool to
bend one of the tabs
on the W-1204D-R bottom wing tip skin to the specified
angle.
Using the digital level in the bevel mode to
display the angle of the tab which, in this case, was 30 degrees.
Finished W-1204D-R wing tip bottom skin with
freshly cut wiring
access hole in the foreground and bent tabs in the
background.
