Wing attach oops

szicree · #1 11-08-2005, 04:40 PM

I recently drilled my rear spar attach and all went well in terms of fit, alignment, incidence, sweep, blah, blah, blah. So here I was reading through another builder's account of a similar accomplishment when I came across "I used a hardwood block to make sure the drill remained perpendicular to the material". AAARGH!!!! I knew I was forgetting something. I had even made several sizes of maple blocks specifically for this task! Dangit! So I went out to check and found that the worst of mine goes through at a 4 degree nose down angle. This is not good and I'm looking for ideas. I'm gonna contact Van's as well. My first idea would be to carefully reface the spar carry-through to match the angle of the hole, my thought being that the goal is to have the bolt or nut sit squarely on the underlying surface. The problem here is that to reface the whole surface would require taking about .070 of material off of each face. That seems like too much. Ideally I could find some type of tool that I could insert in the hole and rotate against the face until it created a surface for the bolt/nut. Any ideas would be greatly appreciated.

Steve Zicree
RV4

RV7Guy · #2 11-08-2005, 04:47 PM

I read about somebody who a booboo similar to yours and the solution was to go redrill to a larger bolt. As long as you have the edge clearance all the way around this should work.

No cause to panic, YET!!

Darwin N. Barrie
Chandler AZ

LettersFromFlyoverCountry · #3 11-08-2005, 04:59 PM

So tell me more about the hardwood block, thing. I haven't seen reference to that before. I presume this acts as a bushing?

McFly · #4 11-08-2005, 05:03 PM

Would a shim like washer on both sides of the bolt work? This would keep the standard washer and bold head from gouging the spar when tightened down. I would think you would want to make it slightly larger than the standard washer. You would also need a longer bolt to accommodate the extra layers.

I like RV7GUYS solution, but if you don't get the edge clearance this may be an option. Good luck.

PS: Bob, the maple block (or steel or aluminum) acts as a jig when drilling the hole.

LettersFromFlyoverCountry · #5 11-08-2005, 05:27 PM

I notice that Avery sells a plastic bushing sort of thing. Would that be useful in this procedure/

McFly · #6 11-08-2005, 05:49 PM

We are airplane builders Man, we don't buy jigs.

All you need is a drill press that is accurate for drilling a hole perpendicular to the jig material. The upper and lowers surfaces of the jig material MUST be parallel to one another.

You may want to make several jigs with progressively larger holes (you want to start small and work your way up to final size). Use a reamer for final size if possible.

Mike S · #7 11-08-2005, 06:43 PM

The tool you need is called a spot facing tool, uses a pilot in the hole to guide a cutter that will make a flat normal to the bore.

Check machine tool suppliers, or a local machine shop.

Mike

Rick6a · #8 11-08-2005, 06:51 PM

Quote:

Originally Posted by szicree

I recently drilled my rear spar attach Any ideas would be greatly appreciated.Steve ZicreeRV4

Steve,

If I understand you correctly, the hole is drilled at an angle so the bolt will not seat properly? If so, the fix is fairly easy. You will have to fabricate a square tapered shim using .125 stock approximately 1" square. Taper the stock as required. This "may" mean a taper ranging from .125 on one end of the shim down to .005 on the other. Drill a hole in the center of the shim to .312 to accept the bolt shank, maintaining e.d. Just like any washer, the tapered shim MUST contact the entire head of the bolt. The threaded end is to be dealt with the same way UNLESS you can find a combination nut/washer that is designed to float on a slanted surface such as the one shown. Of course, the bolt will have to be of a longer length as required.

This was a common fix on the production line. You are not the first person to drill a less than perpendicular hole. Just a little rework and you are good to go.

Rick Galati RV-6A "Darla"

szicree · #9 11-09-2005, 12:40 AM

Wow, too many good ideas. Here's my options in order of appeal:

1. I've got gobs of edge distance so I really like the idea of just re-drilling (straight this time) to a slightly larger size. I figured out that with a 4 degree correction and a half-inch hole depth, the hole will be .035 over by the time I'm done. Lucky for me the existing hole is actually .010 under right now because I didn't ream it to final size yet. So if all goes well I'll be .025 over spec by the time I'm done poking a new hole. This would mean I could use an 11/32 bolt, which is so close to the 5/16 nobody will ever notice the difference.

2. The spot facing idea seems mighty appealing since I wouldn't risk screwing things up worse. However, I'd end up having to remove about .035 of material to get things perpendicular, which seems like quite bit.

3. The shim idea was actually the first thing I thought of when I realized my screw-up, but I hate the idea of a big ol' shim under there. I've never used anything like that and I'm curious about how I go about getting it into just the right orientation. Eyeball I guess?

I sure appreciate everybody's input on this one, so if anybody would like to comment further that would be great. Thanks again.

Steve Zicree
RV4 (with a honked up spar stub)

N941WR · #10 11-09-2005, 06:52 AM

Quote:

Originally Posted by szicree

Wow, too many good ideas. Here's my options in order of appeal:

1. I've got gobs of edge distance so I really like the idea of just re-drilling (straight this time) to a slightly larger size. I figured out that with a 4 degree correction and a half-inch hole depth, the hole will be .035 over by the time I'm done. Lucky for me the existing hole is actually .010 under right now because I didn't ream it to final size yet. So if all goes well I'll be .025 over spec by the time I'm done poking a new hole. This would mean I could use an 11/32 bolt, which is so close to the 5/16 nobody will ever notice the difference.

Steve,

The best way to get them straight is to take a block of steel and have a machine shop drill a "straight" hole in it. (Let them know what the block is for and they might heat treat it for you.) Use your drill bit to center the guide over the existing hole prior to drilling and clamp it in place. You could use wood but it might allow the drill to wonder a little and you might not get a straight hole.

FYI- A reamer will not work because they are designed to follow the existing hole.

This will not help you but it will help others following this thread who still need to drill these holes.

I marked the hole location, dimpled it, then drilled a starter hole in it with a #30 bit. The starter hole did not penatrate the bracket, it was just enough to enlarge the dimple. A small block of oak was then clamped to the aft spar, using a #30 bit to center the block over the starter hole. The #30 hole was then drilled through the spar using the block to make sure the bit went in straight. Progressively larger drill bits were used to enlarge the hole and a reamer was used to attain the final size.

There are three pictures, dated 10/7/05, on the fuselage page of my web site that should give you and idea of how I did it.

If I remember right, after the step in the instructions telling you to drill the hole, they talk about using a block to keep the drill bit straight.