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Tip: Official guidance for drilling holes in wing spar center section 7s and 9s.

Funny footnote in the guidance document

"*This FAQ is dedicated to our Tech Support guru Ken Scott, who spent the better part of 15 years asking for this document to be written only to retire shortly before its release."

I remember asking this very same question at least a dozen years ago. Can't remember who answered, but it was probably Ken.
 
Brian, good info, to make it easier to find in the future, I am going to make it a sticky in the "Builder tips" forum.

Thanks for sharing.
 
I always know when someone revives one of these old threads as I get a ton of new share request from Google drive. LOL
 
Holes

"Only one new hole should be drilled in each bay (i.e. left aft outboard, right forward inboard, etc.)."

Not sure I need additional yet. May I intrepret this to mean four (4) more pathways or a total of eight (8) holes may be drilled?
Left, Aft, Outboard==Left, Forward, Outboard
Left, Aft, Inboard==Left, Forward, Inboard
Right, Aft, Inboard==Right, Forward, Inboard
Right, Aft, Outboard==Right, Forward, Outboard

It appears only a couple options result in a straight pass through.
Just making sure.
 
I recently went through the process of adding 2 inboard holes. This operation would be much easier before you have to sit in the plane to drill the holes. I used a dewalt 90 degree adapter and a step bit to drill 3/4" holes. From the template I thought they were going to be straight through, but they were not. Still I didn't have much trouble routing the wires through. I have a long pair of forceps that I used to grab the wire after it passed through the first side and then to get it started on the second side.

A couple of notes about the Van's templates and suggestions. First the templates don't include the area for the 1-1/2" bars so it is difficult to position them. I added 1-1/2" to the bottom and that made it much easier to locate them. The other item is that Van's provides an allowable box to place the holes but says the center (vertically) is the best position. This actually places the wires fairly high. It might be better to use the lower extremes from a wire routing point of view. I'm adding adel clamps to the seat ribs to make sure the wires can't interfere with the stick assembly.
 

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"Only one new hole should be drilled in each bay (i.e. left aft outboard, right forward inboard, etc.)."

Not sure I need additional yet. May I intrepret this to mean four (4) more pathways or a total of eight (8) holes may be drilled?
Left, Aft, Outboard==Left, Forward, Outboard
Left, Aft, Inboard==Left, Forward, Inboard
Right, Aft, Inboard==Right, Forward, Inboard
Right, Aft, Outboard==Right, Forward, Outboard

It appears only a couple options result in a straight pass through.
Just making sure.

That is what I noticed too, and if you are routing static or pitot then it is more important. I made templates and laid them over each other, selected the locations based on other stuff - -yes a late addition -- then drilled, deburred and alodined.
 
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