Drilling new hole in Aluminum rib; how close?

[mhorowit]

I'm trying to align the holes in the leading edge sheetmetal with the existing holes in the ribs. Sometimes they line up, sometime I can see the hole in the rib, maybe 1/2 screw shank thickness away (in which case I use a Dremel bit to enlarge the hole in the sheetmetal in the direction of the rib hole) and in some cases I'm more than a screw shank's distance away, so I'm going to have to drill another hole in the rib. Question is how close can screw holes in ribs be before I've weakened the rib?
If this were wood I'd enlarge the hole, glue in a dowel and redrill the hole. What's the equivalent when drilling holes in ribs? - MikeH

PS - I've seen pictures where folks rivet another piece of aluminum to back up the rib, but there has to be a easier way

[VictorBravo]

Re: Drilling new hole in Aluminum rib; how close?

IMHO one or two double-holes side by side in a rib will not be a problem. What you want to do is have the holes in the ribs lined up fore-aft in the center of the rib flange so they will not start a crack running out to the edge of the rib flange. One hole in the center of the flange and then another one next to it halfway out to the edge of the metal is what will start to crack and weaken the rib.

Many more experienced restorers here than I, but I'm pretty sure that you'd MUCH rather see enlarged holes in the leading edge sheet metal than the ribs. Drill the holes from inside the wing using the EXISTING holes in the rib as your guide point... and if that means an oval or double hole in the skin then it's a lot better than in the rib. Skins are cheap and easily replaceable, ribs take more time to repair or replace.

The trick tool is a cheapie 90 degree angle grinder from Harbor Freight or a 90 degree Dremel tool. The length of the drill bit needs to be chosen on the basis of allowing the drill chuck to allow you to drill the holes without the drill chuck hitting the rib, or as close to 90 degrees as possible.

I'm trying to align the holes in the leading edge sheetmetal with the existing holes in the ribs. Sometimes they line up, sometime I can see the hole in the rib, maybe 1/2 screw shank thickness away (in which case I use a Dremel bit to enlarge the hole in the sheetmetal in the direction of the rib hole) and in some cases I'm more than a screw shank's distance away, so I'm going to have to drill another hole in the rib. Question is how close can screw holes in ribs be before I've weakened the rib?
If this were wood I'd enlarge the hole, glue in a dowel and redrill the hole. What's the equivalent when drilling holes in ribs? - MikeH

PS - I've seen pictures where folks rivet another piece of aluminum to back up the rib, but there has to be a easier way

[astjp2]

Re: Drilling new hole in Aluminum rib; how close?

Look at AC 43.13-2a, if you use the same criteria as a rivet in structural aluminum, you are looking at 2D edge distance....Tim

P.S. get a 3/32 hole finder, it will help align the holes and is real close to the diameter of a #4 pk screw.

[mhorowit]

Re: Drilling new hole in Aluminum rib; how close?

P.S. get a 3/32 hole finder, it will help align the holes and is real close to the diameter of a #4 pk screw.

Tim - I"m not close to the edge; I'm close to a previously drilled hole.
Also, would you please define a "hole finder"? Thanks, MIkeH

[astjp2]

Re: Drilling new hole in Aluminum rib; how close?

Here is a link from the Yard store that show a hole finder, you can use it to drill through the leading edge.

http://www.yardstore.com/index.cfm?action=ViewDetails&ItemID=266

I would use figure 4.5 of AC-43.13 1b, it gives a distance of 4d, but realistically 2 D would be good enough, I had prewar ribs and I had a heck of a time to getting the skins tight and the holes aligned, I finally had to use a #45 drill bit that was 12" long and drill through the skin from the inside, the long bit allowed me to reach it and not hurt the spar or other areas of the wing. Tim

[Forrest Barber]

Re: Drilling new hole in Aluminum rib; how close?

next time you come by Alliance, you can check out my collection of "hole finders" quick way is to use two worn out hacksaw blades, bolt one end, scratch your head and figure out on the other end that you need sharpened machine screw on one blade facing inward...... end of A&P course for today.
2D is good use holes in ribs don't redrill ribs if possible.

[mhorowit]

Re: Drilling new hole in Aluminum rib; how close?

next time you come by Alliance, you can check out my collection of "hole finders" quick way is to use two worn out hacksaw blades, bolt one end, scratch your head and figure out on the other end that you need sharpened machine screw on one blade facing inward...... end of A&P course for today.
2D is good use holes in ribs don't redrill ribs if possible.

In combination with Forrest's suggestion and pictures on the Inet, I'm ready to build my first hole finder. Forrest describes the male part on one leg, but what's on the corresponding other leg? Could be another male part pointing inward( in which the first 'peg' traces the inside of the hole and the second 'peg' scribes the ID of the hole on the outside), could be a hole in which the initial male peg is used as a center punch.

which is it? - MikeH

[high time cub]

Re: Drilling new hole in Aluminum rib; how close?

Hi Mike,

scroll down for a description and sketch.....

http://www.seqair.com/skunkworks/Canopy/Metalwork/Metalwork.html

Jim

[Guest]

Re: Drilling new hole in Aluminum rib; how close?

Also could buy one from an aircraft tool supply if you were so inclined

[mhorowit]

Re: Drilling new hole in Aluminum rib; how close?

Also could buy one from an aircraft tool supply if you were so inclined

Dave - half the fun is building the thing you need to do the job - even if it means building an air compressor! - MikeH

[mhorowit]

Re: Drilling new hole in Aluminum rib; how close?

Hi Mike,

scroll down for a description and sketch.....

http://www.seqair.com/skunkworks/Canopy/Metalwork/Metalwork.html

Jim

Excellent; I was looking at it wrong; thanks, MikeH

[high time cub]

Re: Drilling new hole in Aluminum rib; how close?

Mike,

The hole-finders in my tool box are 65+ years old. They're beautifully crafted from sheet copper. The head of the "finder" rivet is countersunk and soldered in place creating a flat surface between the blades. Be inspired!

Jim

[mhorowit]

Re: Drilling new hole in Aluminum rib; how close?

Mike,

The hole-finders in my tool box are 65+ years old. They're beautifully crafted from sheet copper. The head of the "finder" rivet is countersunk and soldered in place creating a flat surface between the blades. Be inspired!

Jim

I figure the one I'll need would be about 23" long. Do you have 'finders' that long or am I approaching this wrong? [The LE of the aileron is 44" long - divide by half gives me 22" + some for the handle]

Sheet copper means almost no spring, correct? in that case I can use steel banding, right?

I was wondering how I would secure the 'finder' ; thanks - MIkeH

[high time cub]

Re: Drilling new hole in Aluminum rib; how close?

No, the longest is 6-7 inches.

Right, the copper has almost no spring.

[VictorBravo]

Re: Drilling new hole in Aluminum rib; how close?

There are also the little blind hole center punch widgets. You put one in the hole, it leaves a small point sticking up, you put the new sheet in place, and hit the sheet with a hammer. Remove the sheet, and it has the hole center already punched.