[IowaRV9Dreamer]

I'm slightly confused, which is pretty good at this point...Can someone help me???

I'm merrily follwing the instructions building the middle of the fuselage and I've assembled the skeleton consisting of seat ribs, baggage ribs, center section bulkhead, and F-705 bulkhead. So far so good.

I see that each set rib is supposed to have 2 bolts in it to attach to the aft side of the center section bulkhead. There are no holes in the flanges, so I figure I should drill some. As I'm picking up my drill, I see the following note on section A-A of DWG 25: "IF HOLE IN RIB FLANGE IS MISALIGNED WITH HOLE IN F-904, CAREFULLY RUN DRILL BIT THRU HOLE"

This makes me stop and think. They want me to be careful running a dril but thru the spar bar. Probably so I won't mess it up and cause a weak spot. I guess they might mean "use a drill bit by hand to slightly widen out the hole". Problem is I have no holes to widen out - I have to drill these holes (#12 seems to fit nice in the spar). Will it be OK to drill if I am "careful?"

Of course, the manual never mentions any of this, but I'm happy that I'm at least thinking about it.

Is it OK to just have at it and drill the holes using the spar as a drill guide? I can't see how to drill them not in assembly, since the spar bars are so thick. Maybe I'm too cautious... what have others done?

 

[rv9aviator]

If I remember my ribs had holes but may have been just a small hole like the rivet hoiles and I enlarged them using the center section as a guide. I would use whatever drill size slips through the center section. If a 3/16 fits well I would use that as it should let the bolt go through. The # 12 would be fine if it doesn't shave metal out of the center section. Hope this helps.

 

[Norman CYYJ]

To drill thru the spar can cause damage to the holes in it very easily. So take a small drill quite a bit smaller than the hole that you want to drill. Put a piece of tubing over it that will fit thru the spar hole. In other words put a piece of AL or copper tubing in the spar hole and then use a small drill that just fills the tubing and won't cause it to bind. Then drill the hole in the rib. Remove the rib and then drill the small hole to number 12. No damage to the spar and the hole will be in prefect alignment.

 

[n615ks]

The brass & aluminum tubing (KD?) sold in hardware stores is perfect for the job and the ID/OD steps up in fractional drill sizes. My ribs were not drilled either and it was a bit of a surprise when I was asked to insert bolts through them . I drilled them one size under with the tubing through the spar and then used a reamer to finish up after removing from the spar.