Paul Tuttle

Paul Tuttle

Well Known Member
I,m ready to drill the rear spar to attach the wings to the fuselage. All measurements appear to be exact, but there appears to be little or no room for error to maintain the proper edge distance.


Has anyone else run across this? I'm hoping the answer is hold your breath, drill carefully, and carry on.

I've attached a little drawing for explanation

rearsparim9.jpg
 
That's correct...

Things are tight. Be Careful. Measure multiple times before drilling. Start with small hole so you can "walk" it over if necessary.
 
I had a box about 1/8" by 1/4" in which it was OK to drill. Anything outside that and I would have not had edge distance on either the spar or fuse. Make sure you use a drill block and/or a long drill bit to make sure you get it straight through all four layers. A helper is pretty important on this task. Good luck.
 
Mel said:
Things are tight. Be Careful. Measure multiple times before drilling. Start with small hole so you can "walk" it over if necessary.
Click to expand...
Excellent advice from Mel. Golden. Now is not the time to cut corners. That is a critical location and optimum hole quality should be strived for. That means start with a #40 or #30 pilot hole and bring the hole up to full size in steps. If possible, use a drill block to assure perpendicularity. The final full size pass should be done with a well lubricated reamer and low RPM. If you do have to move the hole over to maintain e.d. here is a method I often used in my day job:

http://www.vansairforce.com/community/showthread.php?t=11769

Good luck Paul, may the drill gods be with you!
 
Yes, very little room for error

Hi Paul:

I can second what everyone has said.

I have an RV-8 QB. I found it difficult to accurately judge the edge distance of the rear spar since it is sandwiched between to other items. Before drilling I was tweaking the incidence by slightly raising the rear spar before drilling. As you move the rear spare up/down/in/out you need to take relative measurements to determine edge distance. When I drilled I thought I had *plenty* of room to spare. In reality I only had slighly less then 1/16.

I used a hard wood block and a set of drill bushings for drilling.

Mike Draper
RV-8
Bridgewater, MA
 
Paul,

I drew the lines on the spar stubs before inserting the wings so I could see exactly where I could drill.

There are some pictures on my fuselage page showing how I drilled the holes. Scroll down to the 10/7/05 entry.

Once I center punched the proper location, I started drilling a #40 hole in the stub but limited it to maybe 1/16" in depth. You only want to start the hole, not go through one part of the spar stub.

Then I slid a 12" flexible drill bit through a small block of oak that I had previously drilled a perpendicular #40 hole through. The tip of the 12" bit was placed in the starter hole and the oak block was slid down the drill bit until it was against the spar stub and then clamped it in place. This was done to make sure the block was exactly in the right place.

The 12" #40 bit was then chucked in my drill and the hole was completed. This method assured a perpendicular hole through the spar.

After that I enlarged the hole using a bunch of different bits. The final size was completed with a reamer, thus providing a perpendicular and round hole.

I hope that is clear and it helps.
 
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Thanks guys, I've remeasured it a couple of times and it's not quite as close as it first appeared (but still close) I'll follow what you have said, and things should turn out right.
 
Paul,

One other thing. The edge distance given on the -9 is to the center of the hole, not the edge. This caught me at first as I couldn't figure out how I was going to drill such a large hole and maintain the proper distance from the edge of the hole to the end of the spar. BIG Duhhhhh on my part.
 
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