Sunday, January 20, 2013

Left Wing Wiring Begins

Drilling out the grommet holes on the inner most ribs of the left wing turned out to be much easier than first thought. The step drill was hitting the previously installed stand off on the inboard rib and for that matter, so would the chuck of the drill.
                                               Step drill hitting previously installed stand off on the inner most rib.

I was prepared to a little “creative access” by way of slipping some vinyl tubing over the shank of a drill bit along with a dowel rod inside the tubing to keep rigidity and try using that to extend into the next rib bay to get to the inner ribs.  Fortunately, none of that was necessary because my 7/16” drill bit was way longer than I remembered and it was able to reach with no issues.
                                             At the root of the wing where the ribs are doubled up, inner ribs were
                                             drilled by going through the grommet hole in adjacent ribs.

My suggestion to builders interested in using shielded cable for the strobes and the Tygon tubing for the angle of attack indicator would be to drill all the W-1208 nose ribs to 7/16” for Heyco SB-437-4 or -5 grommets before riveting them in place. It is easy enough to do after the ribs are attached onto the wing spar, but you just have to jump through some extra hoops. If you are adding a left landing light and also using sheilded cable read the next paragraph.

Return from the future … the plan was to use SB-437-5 grommets in just those locations where the Tygon AOA tubing runs adjacent to the wiring and SB-437-4 grommets where the two shielded cables run by themselves. Because I’m using shielded cable for nav/strobe lights & the additional left landing light, the fit in the SB-437-4 grommets is snug enough so when both sheilded wires are in place, the ribs don’t want to move easily. This may make aligning the ribs to the skin more of a challenge than it should be, so I’ve changed those grommets out for SB-437-5 grommets. Now the wires do not prevent the ribs from moving easily. All of the rib grommets are now SB-437-5 except for the very last outboard grommet which is a SB-437-4.

After all the grommets were inserted into the ribs, the first wire installed was the stall warning indicator wire and by then my hands were getting quite cold so called it a day.
                              Stall warning indicator wire - first of the wing wiring to go into the left wing wire grommets.