[jsharkey]

I installed -4 Snap Bushings and a pull string for cable installation before I closed the skins on my wings a few years ago. I am now installing a landing light, nav light and tip strobe in the wings and have realized that the shielded three wire strobe cable alone fills the -4 snap bushings. I might just be able to squeeze the 18AWG nav light wire through as well but definitely not the 14AWG landing light wire.

Anyone else faced this late in the day dilemma and any ideas on how to get around it. I have lots or corrugated wiring conduit but am not sure how to secure it to the ribs deep in the wing.

Jim Sharkey
RV6 - Wiring

 

[JonJay]

Conduit

I installed conduit late in the game. The product I used was from TAP plastics. It is a rigid carbon fiber/epoxy composite tubing. I ran it through the same lighting holes as the Aileron Push Rods and secured each end with an Adel Clamp at the wing root and then at the Aileron Bellcrank Access Plate location. It is very secure, light, and has plenty of room for extra wires.
You do need to insure that you locate the tubing clear of the Aileron Pushrods and Bellcrank but there is plenty of clearance there.
I only needed one 4' conduit from the Bellcrank to the wing root, but you could transition your wiring at the Bellcrank and install another conduit to the wing tip ahead of the spar.
I used a standard snap bushing epoxied into the end of the tubing to prevent chaffing.

 

[N941WR]

Jim,

If you are going to use LED position lights, you might be able to down size those wires a little. Check with your manufacturer.

 

[fl-mike]

I had the same problem. I removed the existing bushings and opened up the holes using a 1/2" unibit on a six foot or so extension I made up from two sections of threaded rod and a couplers (drilled and tapped the coupler to secure the unibit with a setscrew). Covered the rod with shrink tube or something to keep from chewing up the holes and went slow. I was able to get new snap bushings in all the holes by reaching in through the lightning holes or inspection plate. It actually worked quite well and was fairly easy. I think I used a length of hinge pin or something to fish a pull-string through.

 

[RVG8tor]

Which holes

............... I removed the existing bushings and opened up the holes using a 1/2" unibit ......

Fl Mike,

Which holes did you open up to 1/2"? I am assuming that you are talking about the small holes just where the rib meets the main wing spar. I am working on my QB wings and don't know exactly my wire requirements at this time, but I was thinking of just doing a series of holes, at the forward part of the rib near the main spar, curious if that is where you are opening up to 1/2" the other choice is conduit, but if I can run all my wires and pitot lines long the spar in the ribs I think I like that better, of course with a string for future wire pulling if required. It seems most go with the conduit, either the 3/4 corrugated stuff Van's sells with the hole aft of the forward lightening hole or conduit suspended in the lightening hole.

Cheers
Mike

 

[jsharkey]

I had the same problem. I removed the existing bushings and opened up the holes using a 1/2" unibit on a six foot or so extension I made up from two sections of threaded rod and a couplers. Covered the rod with shrink tube or something to keep from chewing up the holes and went slow. I was able to get new snap bushings in all the holes by reaching in through the lightning holes or inspection plate. It actually worked quite well and was fairly easy. I think I used a length of hinge pin or something to fish a pull-string through.

Necessity truly is the mother of invention. Thanks for the inspiration!
Jim

 

[fl-mike]

Which holes did you open up to 1/2"?

In my case, they were existing. Not sure what is on the new kits, this is a slow build 6. The most important thing is that they all be in about the same location! The drill extension will allow a little slop, but guiding it after the second or third rib can be tricky. It'd be easier with a helper. I seem to remember I had to do some adjusting at the wing walk area at the root, but you'll come in from both ends anyway. I also started with one extension and added the second extension as I got in. My arms aren't THAT long. I believe the newer kits (7,8,9) have more inspection plates, so that would make things easier.

 

[Rene Bubberman]

It takes some improvisation....

Here's how we did it: http://websites.expercraft.com/PHVII/index.php?q=log_entry&log_id=2964

 

[mototopo]

Sorry for the intrusion,
I own about 30ft of a "special modified polyamide" fireproof wire conduit but it's not enough soft as the one Vans sells and it's almost impossible to slide it into the 3/4" hole on the wing ribs. Can this hole be enlarged to 0.790" (20 mm) or 0.750" (19 mm) is the maximum size allowed for the hole?

Thanks

 

[flion]

You should be ok enlarging it that little bit.

For those needing to do that after the fact, the aviation department at Home Despot (er, Depot...) has conduit drills - long flexible drills for routing conduit through walls. The drills aren't really useful, since they're intended for wood and sheetrock, but the extensions are. There are two that I know of - the largest fits at 3/4" unibit while the smaller will accomodate the 1/2" uni. They are also useful for getting the unibits into other awkward places and can be flexed an amazing amount. Requires two people to operate though as you can't guide the bit and operate the drill with normal human arms...

 

[lucky333]

Bushing with slightly more I.D.?

Sounds like you are pretty tight but take a look at some alternatives here. You didn't indicate which -4 you used but even with the SB375-4 you can go up another .031" I.D. with the same .375 hole (SB-357-281), more if you used a bigger hole size.

http://www.heyco.com/products/sec_04/pdf/4-01.pdf

Mouser stocks Heyco in depth. I bought 100ea of several sizes on the list but not the big IDs or I'd send you some..

Good luck.

I DO like the looong drill idea!