VS spar strobe cabling

[zkvii]

Hi,

I've looked at the various posts / RVator, but am struggling to find information on how people have made the transition through the aft VS spar / bulkhead for the strobe lines.

With the "A" tie down bracket the actual spar is quite a 'thick' surface to drill through (.250+) and then the steel brackets are in addition. I like the comment from VANs about not going through the VS (just the bulk head) but can't find any detailed photos.



Option A is to take out a rivet - probably my preferred option at the moment
Option B is between the rivets - but makes edge distance very "marginal"
Option C is in the main VS spar - doesn't 'sound' like a good idea

Comments / ideas / photos

Thanks,

Carl

[lrfrey]

Carl, A or B will work. I did B but on the left side. Van's did A or B can't remember which in one of the recent issues of thr Rvator. Removing one rivet isn't going to hurt anything, but I elected to go between them. I will not use a snap bushing thus keeping the hole small and not compromising edge distance, then wrap the wires with spiral wrap or a piece of neoprene tube.

Larry

[Ironflight]

I actually have hole at both "B" and "C" locations Carl. I originally used the "B" location, but when I got the rudder mounted, with the lower fairing, and the wires installed, I found the the cable was binding more than I liked. There were probably a number of ways to solve this, but about then, I saw pictured on several people's web sites of the hole at "C" (I think I saw it on someone's plane at a fly-in as well), and that looked like the quickest and easiest way to go at the time. Seems to be working quite well for me.

Paul

[Radomir]

Carl, after seeing it on another -7A, I chose "D" -- run wires right by the tiedown bar where it's tapered, through that semi-circular hole.. Didn't drill any additional holes. There's enough room for strobe and position light wires. Beef the wires up with some heatshrink (or whatever you feel comfortable with) for additional protection. The plane I saw it on had about 80 hours at that time, and showed no signs of chafing of those wires.

[Guy Prevost]

Carl,
Option C really isn't a bad choice. Structurally the material towards the centerline doesn't carry much stress. The (vertical) centerline of the rear spar is it's neutral axis, it's the material on the outside that really gives the VS it's stiffeness. That's why you can put lightening holes in the center, but wouldn't want to notch out the edges of the doubler.

A way to visualize this is to think of an "I" beam. The stength of the beam is in the top and bottom flanges. The web of the beam is just there to hold the two flanges apart, where they can do some good.

Hope this helps,
Guy

[Jaknjoan]

I have been flying my RV-9A for nearly 500 hours and find my location has worked well. I drilled a 5/8 hole in the middle, between the two rivets, directly above the bolt hole, then inserted a 5/8 inch bushing from the inside. The 5/8 inch hole in the rudder is also in the center, but possibly a little higher. I ran the wires through a 7/16 OD plastic tube from the hardware store(5/16 ID). The center results in the least movement of the wires when swinging the rudder. The plastic tube is pushed into the bushing and gives double protection to the wires.

Jake Thiessen
Finished RV-9A in 2003
Flying 500 hours

[zkvii]

Just for completness - the response from Gus @ VANs

"Either A or B is OK, don't do C"

Thanks for everybodies input.

Carl