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Drilling wing to install OAT probe

MacCool

Well Known Member
Built RV-9A. I have a new Dynon ADAHRS which requires a new OAT sensor, which I'm putting on the underside of the left wing. I've run the wiring up to the middle inspection plate, just need to drill the 3/8" hole for the probe. What's the best way to drill the hole? The wing skin between the ribs flexes quite a bit...can I drill that hole through the adjacent rib flange?
 
Adjacent to the rib = not enough flexing from wind to crack the paint or fatigue the aluminum wing sheet?
 
Built RV-9A. I have a new Dynon ADAHRS which requires a new OAT sensor, which I'm putting on the underside of the left wing. I've run the wiring up to the middle inspection plate, just need to drill the 3/8" hole for the probe. What's the best way to drill the hole? The wing skin between the ribs flexes quite a bit...can I drill that hole through the adjacent rib flange?
Agreed, adjacent to the rib will be fine. Since it's near the inspection hole, reach in there and hold a small chunk of wood on the backside of the hole location...this should keep flex to a minimum while drilling.
 
Just finished doing mine, similar location. After a pilot hole, drilled 3/8" with a step drill. Located about 2" from rib flange. Maybe overkill, but I made a 0.062" x 2" diameter doubler and riveted it with 6 x AN426AD3 rivets. Don't like unsupported equipment, antennas etc just supported on the skin. Too easy to hit while washing or otherwise snag and damage the skin.
 
Just finished doing mine, similar location. After a pilot hole, drilled 3/8" with a step drill. Located about 2" from rib flange. Maybe overkill, but I made a 0.062" x 2" diameter doubler and riveted it with 6 x AN426AD3 rivets. Don't like unsupported equipment, antennas etc just supported on the skin. Too easy to hit while washing or otherwise snag and damage the skin.

That was my concern...a protruding object fluttering in the wind, supported only by wing skin. I had considered a doubler, securing it with countersunk 6-32 screws into nutplates but I don't have a riveter, rivets or nutplates. I haven't owned an RV long enough to become part of the RV community here, which I hear is pretty robust in this state, but distance and COVID have kept us apart. My AP/IA is coming over this afternoon to review my wiring and plumbing. Maybe I'll see if he can make me such a doubler. I like the idea.
 
Inspection plate

I plan to put mine on the inspection plate for two reasons: 1 the plate is surrounded by a stiffener so is stronger. 2 if it cracks or gets damaged or gets bent, it is easier to replace the inspection plate as opposed to doing a skin repair
 
I wanted to make sure the cable from the OAT probe did not interfere with the aileron push rod. I located the OAT probe somewhat aft of the centerline of the aileron tube (and the lightening hole it goes through) so that as the cable curves up from the probe, then back down, it could be secured to the adjacent rib at the bottom of the lightening hole with a ty-rap. If I mounted the OAT probe to the inspection panel, I didn't think I could guarantee the routing of the cable.
 
Cable routing wasn’t an issue. There is a three-quarter inch nylon conduit that runs from wingtip to fuselage right at the back edge of all three inspection plates. Running the OAT wires through that conduit to the fuselage is already done and was straightforward. Mounting the probe is my current project.

Here’s another question…splicing the wires...crimped ferrule butt connection with heat shrink tubing, Heat shrink solder sleeve connection, or heat shrink butt connection?
 
SNIP
Here’s another question…splicing the wires...crimped ferrule butt connection with heat shrink tubing, Heat shrink solder sleeve connection, or heat shrink butt connection?

Never liked solder sleeve or crimped butt connectors - too clunky. I simply solder the wires, shrink tube over each joint and then larger shrink tube over the two other tubes.

This process is used in multiple places and has worked well over the last couple of decades.

Carl
 
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