To enlarge the pre-drilled wiring hole for a conduit, I followed Van's recommendation and enlarged them to the maximum of 3/4". I verified that I could get .81 conduit through the 3/4" holes using a scrap piece:
|Checking that I can get the .81" conduit through a .75" hole.|
To actually do the enlarging for the inboard ribs where both skins were already riveted, I used a 12" 3/8 drill extension (from Home Depot) and a unibit which had 3/4" as its largest size:
|"The harpoon" - setup to enlarge rib holes|
Deburring those holes was slightly annoying and required some contorting, but was doable.
Running the conduit through them, on the other side, was VERY annoying and time-consuming:
|Conduit done on the right wing|
Luckily, I recruited an intern (visiting friend) to do it for the other wing:
She looked happy on this picture - that's because then she hadn't yet realized how painful it'd be to run the conduit through the inboard section with the bottom skin already riveted on :) but she got it done anyway.
I chose to install the pitot tube one bay outboard of the aileron bellcrank (per previous post) and cut/bent/deburred/flared its tubes such that they'll go through the rib, angled such that they point towards the holes in the next rib:
|Pitot and AoA tubes bent for passing through the rib.|
In the process, I found that using a tube bender on these is a very bad idea - I tried to create a bend a little further down, and it created a kink, which made the tube break, forcing me to cut them a little shorter. Going back to the Garmin manual, I realized they were not 1/4", but rather 3/16", which explains it :/
Just in case, I protected that lightening hole so the tubes can't contact the ribs:
|Grommet edging protecting the path of the pitot/AoA tubes|
I drilled the second set of tube holes, for the AoA tube, using a combination of the extension shown above, long drill bits, a right-angle drill, and a snake drill (it was especially annoying to drill through the 3rd and 4th inboard ribs):
|Pair of pitot/AoA holes next to the|
|AoA tube holes through the ribs (not yet their full size)|
|Initial drilling the inboard AoA tube holes|
Finally, I enlarged the holes to 3/8" (slowly, #40 -> #30 -> #21 -> #10 -> 1/4" -> 3/8") for the SB375-4 snap bushings and verified that the tubes run fine through those paths:
|Pitot and AoA holes with snap bushings installed|
|Pitot and AoA holes just before the aileron bellcrank|
Finally, I test-ran the tubes through the bushings and cut them to size (+slack):
|Tubes running all the way to the pitot tube|
|Tubes reaching the pitot tube|
I realized I don't have the proper snap-on tubing connectors for the root rib holes, so I'll need to order those.
For the second conduit, I didn't want to drill another large hole, so I used ClickBond right-angle cable tie mounts (CB4020V5N12-750):
|ClickBond CB4020s for the second wing conduits|
|Wife examines the installed cable tie mounts|
|Row of installed cable tie mounts for the second conduit|
For some reason, removing the Clickbond fixtures was really hard, and in fact some of the cable tie mounts came out when we pulled them and had to be re-installed.
|Cable tie mounts with the fixtures removed|
I ran the conduits and cut them to size (with a couple feet of slack) - it was amazingly easy compared to the first one, made me wish I had just done this for the other as well:
|Second conduit running through the wing|
The outer rib has no Clickbond for now - I'm leaving that for when the wingtip is installed, so I can figure out which side won't interfere with the wingtip itself. Also, if it goes on the inside, that'd interfere with riveting. Should be pretty easy to install it from the outside anyway.
Since the 2nd and 3rd inboard ribs have no Clickbond mounts (no good reason to, and it'd be quite painful to install in the tight space), I put grommet edging on those to prevent chaffing of the conduit:
|Grommet edging on lightening holes that have no cable tie mount|
I found the right position for the Garmin GAP-26 heatet pitot regulator, one rib inboard of the bellcrank:
|Position for pitot heat controller|
This position is close enough to the inspection hole but will minimize wingtip (NAV antenna/magnetometer) interference by keeping the high-current box further from the tip, and there's enough wire length to still reach the pitot tube. I match-drilled the box's holes into the ribs, then installed Clickbond CN614CR06P nutplates to hold it without interfering with the aileron pushrod:
|Pitot heat controller in place|
|Clecos holding the pitot heat controller show that the nutplates won't interfere with the pushrod|
|Clickbond nutplates for attaching the pitot heat controller|
|Clickbond nutplates with the center shaft removed|
When I test-ran the conduit, I also tried attaching the box and running the wire to the probe - the wire length is indeed good, and the run will be away from the pushrod:
|Garmin pitot heat controller box with wires running to the pitot tube|
|Pitot heat wires arrrive at the pitot tube with good slack|
In retrospect, given how much effort it was to get all of this through the inboard ribs, I probably should just have removed the inboard skin, done the work, then riveted it again - I still don't understand why Van's has to rivet that skin at the QB factory.
At this point, the only thing left related to the ribs is the root connectors (for both air and wires).
Total wing ribs time: 13.2h
Total wing rib rivets: 0!!