hole duplicator

[prkaye]

Can someone recommend a "hole duplicator" tool that would work especially well for drilling the holes in the rear skirt? I'm terrified of getting this wrong and ending up with extra holes in my plexi.
I'm thinking of doing a fiberglass rear skirt - seems many people have had very good success with this.

[noelf]

There are several ways to "duplicate" a hole in materials. Avery carries a tool called a STRAP DUPLICATOR, and are available in several different sizes. I found his type of tool useful, but at times was not appropriated to any type of curved surface I was working on. I had to come up with something different.

I ended up with two different approaches that worked very well for me.

1. Cut a strip of paper poster board material about 2 inches wide, and 12in or so long. You want a lot of "extra" length here. Locate the hole you want to work with in the base material, place the paper "strap" over this hole, and tape it down into position at the opposite end. With a small, sharp, pointed tool, push the tool through the paper and into desired the hole. You have just "located and registered" the hole. Now, leave the "paper strap" taped down, but lift the punched-hole end and slide the new unmarked item (skirt) into position. Lay the "paper strap" back into position, and the previously made hole will be your guide for the location of the new hole. I found this process worked ok with just needing a couple of holes duplicated, but was very time consuming when a large number of duplicated holes were required. This brings us to the item #2.

2. Pilot drill all holes in the base / underlying material. You should have a good idea where the holes will be located when you positioned the two items one on top of the other. Mark for edge positions on the base material. Now, with a long straight edge, draw as straight a line as you can through the center of the previously drilled pilot holes. This line needs to be a good 10 to 12 inches long, in whatever direction, away from the hole, that you can re-measure in a later step. Once the lines are drawn, carefully mark the center of the pilot holes with an accurate, small, perpendicular line to the previously dawn line. You have just declared the location of the pilot holes. Now, from the center of each pilot hole , measure out exactly 8, or 9, or 10 inches along the first line and place another mark. Now you know that the exact center of the pilot hole is located exactly 8, or 9, or 10, or whatever inches away from this mark. Finally, place the overlying material on top of the base material, use your straight edge and transfer the long straight lines to the top material. Measure from the visible reference marks your exact distance, and you have now marked the positions for the duplicated holes.

Hope this helps...

[szicree]

Somebody on here posted a while back about little doodads that you actually place in the existing hole. They have a small point that then protrudes from the hole and makes a mark on the part to be drilled. I'm sure somebody will see this and know where to get them.

[Rick6a]

Originally Posted by szicree

Somebody on here posted a while back about little doodads that you actually place in the existing hole. They have a small point that then protrudes from the hole and makes a mark on the part to be drilled. I'm sure somebody will see this and know where to get them.

That may have been me. I have long been an advocate for using transfer pins and have relied on them for doing all manner of aircraft sheet metal repair work over the years:

http://www.vansairforce.com/communit...transfer+punch

On the RV-8 project they really got a workout when I drilled the side skirts very fast and accurately using the little bits of metal:

http://www.vansairforce.com/communit...ht=side+skirts

[BillSchlatterer]

I would take a pass at making your own. They are just way too easy and I think they work better since you can tailor them for the job. These pictures are lousy but this is the one I made from scrap for the skirts. Not more that 10 minutes to make out of scrap.

Just take a piece of something thick like .040-.063 and something thin as you can get, probably .020 and trim them to the same size. Kinda like big popsicle sticks. I'll explain but the pictures should make it clear.

Then cleco them together at the back and drill a #40 hole through the tip. Bend the thin side back and dimple for a #30 rivet or #6 screw depending on the size hole you are trying to find. You want the dimple to sit down in the plexi without much movement. Don't drill out the #40 hole in the thick side as that will tend to help you center a pilot hole. Now rivet the back side together so that you can slip the thin side with the dimple under the skirt and let it find the hole.

Hold the guide tight against the skirt which should hold the thin piece centered in the plexi. Drill the skirt through the #40 hole which you will have to final drill to the #30 dimple size later. While you have a #40 hole in the skirt, stick a piece of coat hanger, or fine round finish file into the hole and make sure it is really centered on the plexi hole. If not, just file the #40 hole over a bit to make it perfect and then drill to #30.

I have used these in several places, the smaller and thinner you make the piece underneath, the better the fit but it flexes a little more.

I would tape the canopy if you are worried about scratching it as the dimple will scrap around as you try to find the hole. The tape just helps center it better and protects the plexi.



This is a picture of the bottom thin side. The holes can be marked through to help with alignment. There is a smaller one just above the big one that I used for something else.



This is the tool spread apart to show how the thin side goes under the skirt and you drill though the thick side.



This shows the tool inserted under the skirt and ready to drill the #40 pilot hole. You can skip doing this with a pilot hole but it is a little safter tha way.

Hope this helps.

Bill S
7a finishing

[andrew phillips]

I can't take credit for this idea but worked perfectly for me!

Apply masking tape to the top of the canopy at the rear by the skirts. I put about an 8" wide strip of tape. From each of the pre-drilled holes, take a ruler and draw 2 lines that start from the center of the hole and extend onto the tape. The 2 lines need to form a "v" shape. When you lay your skirt over the holes just extend the lines back onto the skirt and where they come to a point is where you drill the hole. Worked perfectly for every single hole for me and only took a few minutes. Hope this explanation is understandable.

[prkaye]

that intersecting lines idea is brilliant. I'd heard of a similar idea but measuring from a fixed point back on a single line, but this idea of using two intersecting lines is amazing. THANKS!

[Greg Arehart]

The closer to 90 degrees your two lines are, the more accurate your location.

greg