Draker

Draker

Well Known Member
Hi, folks, I think I spent all day searching here and on builder's logs reading about wing wiring. I'm at the point where I'm prepping the wing ribs, and that means I ought to be thinking about my wiring plans. I'm not sure what lighting/pitot/accessories I plan to have where yet, but I'd like to make sure what I do now can support any decision I make later. I may actually end up going hog wild with pitot heat, AOA, AP servo, lots of lights, etc. so I'd like to prepare for as much as I can.

To that end, I was planning to drill a 3/4" conduit hole in each of the ribs (both sides) for whatever wingtip lighting I go with, open up the two existing tooling holes to 7/16" and 3/8", and potentially add a third 3/8" hole as other builders have done.

My question is: is there any down-side to adding all these holes if I end up not using some of them? Having unused holes does not structurally compromise the ribs does it? The only down side I can think of would be just more holes to debur, but I thought I'd ask for opinions here before starting to drill.
 
Ryan,

As you have probably already guessed, any holes in the ribs, used or unused reduce their strength. I am sure you would not be the 1st builder to put 4 holes in each rib so structurally, you're probably OK as long as you pay attention to edge distance. You may not need all those holes though. I recently finished wiring my wings and have NAV, Strobe, heated pitot, A/P servo, and a COM antenna cable and I only needed 3 holes in each set of wings, and none as large as 3/4".

I had a QB, so I had to put the 3rd hole in after the wings were mostly assembled. Not terribly fun, but not impossible either. If you really want to give yourself the option you could try a pilot hole for the 4th hole to align that hole through the ribs. Then if you do decide to open it up later, it will be easy to do with a unibit extension. Another option would be to run the conduit through the existing lightening holes and hold it in place with cushion clamps.
 
Hey Ryan,

Here's Van's official guidance on adding holes to route conduit, etc.

https://www.vansaircraft.com/pdf/Wing_Wiring.pdf

I added the 0.625 holes on the pitot side for the AOA line, and ran the 0.75 holes all the way to the tips for the wingtip lighting wiring. I'll extract the wires for the roll servo at the right place from the conduit.

Holes in the ribs, used or unused, will have the same affect on the strength of the rib, but Van's has analyzed the stresses on the ribs and made reasonable recommendations about where to put them. There are places that have no stress and can tolerate a hole without noticing a thing. Other places are a no-no!
 
Last edited:
Thanks, guys. I have seen https://www.vansaircraft.com/pdf/Wing_Wiring.pdf and have a printout hanging in my airplane factory. Unlike other builders, it seems my ribs came with only two existing holes, not three, so I'm very hesitant to add anything besides what Vans calls out in their published wiring guide. I think I'll double check with Vans via E-mail just to be sure.

Ryan
 
Rv9 different

Careful there. If you are building a rv9, Vans told me the rib holes by the spar need to be 1/2" max as per plans, not the larger size approved for the 7 and 8.
 
Sorry, forgot to specify I'm building an RV-7A. In case anyone's curious, Van's recommendation was to stick with the FAQ and use only the holes and sizes called out there, which is what I'll do.
 
You must log in or register to reply here.