bought some metal and a couple of new tools

The last week of summer has come and gone.  We made a family mini vacation to southern Ontario and took in the Brantford Community Charity Airshow among other things.  It was an awesome airshow with quite the collection of warbirds, aerobatics and of course the Canadian Forces Snowbirds!

​Also located at the same airport is Aircraft Spruce, one of the biggest suppliers of aircraft parts, pilot gear and building supplies.  I had placed an order the week before and was able to pick up 3 rolls of aluminum sheet to be used in my build.  Ron and Donna were also at the airshow and were kind enough to bring the rolls back north with them to the shop, saving us having to drag them around on the rest of our family trip.

​I also stopped at KBC Tools in Missisauga and picked up a couple of really handy items.  First, I've been reading about how to cut long straight edges on aluminum sheet.  Some of the spars and doublers I have to make for my airplane are too long to be easily cut by shears.  Even local machine shops in my area  are either unable to handle the widths or too expensive.

​One of the solutions on the Zenair builder's forums caught my eye.  It involves making a aluminum cutting knife out of a carbide machine shop grooving insert attached to a handle, in this case a old crescent wrench.

​I found the grooving insert at KBC tools.  It's expensive for it's size, but is able to make very thin cuts in aluminum.  For a couple of dollars more, I opted for the Titanium nitride coated insert making it more durable:

Side profile showing the cutting ends. It's hard to show in the picture, but the cutting surface on each end is only 19 thousandths of an inch wide. It's used for making grooves in machined metal, like for O-rings etc.

​For a donor handle, I used an old crescent wrench with a seized head.  I cut the head off at a 110 degree angle at the narrowest part of the handle using the chop saw:

​Cleaned it up on the grinder.....

​Next I used a combination of Dremmel tools and hand files to carve a shallow groove in the handle for the insert to rest in:

Insert to handle layout

File and grind a shallow groove, drill mounting screw hole on drill press

Tap the hole for 6/32 NC cap screw thread

Install insert and tighten screw

I took it apart again and used the grinder to clean up any sharp edges on the handle that may scratch the aluminum when making a cutting pass.

​I made a test cut on a scrap piece of aluminum and this tool cuts it nice, clean and straight and only requires a couple of passes to score the aluminum enough for breaking.  MUCH faster than using a laminate blade like an Olfa.

​The other tool I picked up at KBC Tools was a NOGA Rotodrive countersink/deburring tool:

​This is a much quicker and simple way to deburr dril holes.  It is a rotating "dog-leg" countersink and with a very light touch and two turns will remove drilling burs without countersinking the hole.  Lightweight and fast, it will be super handy as I progress through building.  Much better than rolling an oversize drill bit between the fingers.

​I continued work on the wing tip extension.  I fabricated two (one for each wing) spar web doublers out of 0.032 sheet on the bandsaw. These will be the bread of the sandwich where the tip extension and spar web meet:

​Laid out the proper rivet spacing and matched drilled them together:

​Mounted the assembly to the wing spar web and match drilled the par caps, then clecoed everything together to confirm alignment:

​With the assembly temporarily in place, the next problem needs to be solved.  How to match drill to the original holes in the spar web (inclunding the orginal outer wing rib) without any access inside this part of the wing?  As you know, the previous builder just eyeballed things so measuring what is already there won't be accurate enough. I could pull more of the wing skins off and back drill through the new doubler, but there is an easier way!

​Introducing the "rivet hole duplicator".  This ingenious tool allows you to match drill to holes behind the sheet aluminum.  It consists of two straps of spring steel, one with a hole locator and the other with a drill guide:

Drill guide hole on left tang, locator pin on right tang.

​With this tool, it's simple to find the right spot to drill each pilot hole.  The pin tang slides in behind the panel you are drilling and the guide lines right up to where your new pilot hole should be..... GENIOUS!

River hole duplicator in use

​Duplicate holes on web spar (right side of joint centreline) are complete awaiting final rivets. We'll need to figure out what we are doing on the back side to extend the spar caps and sandwich everything together but for now, this should be easily repeatable on the second wing:

​With that complete, I took some time to fabricate the wing slat ribs from some spare 0.016 sheet.

​There are 12 of them required, 6 in each wing slat.  So I traced them out from the template, trying to use up as little real estate as possible.  This will become more important later on when cutting other multiple items from full sheets:

​One of the lessons learned earlier when I was making tail ribs was to centre punch and drill the relief and tooling holes before cutting out the metal, so I did that here first:

It takes a very light tap to make enough of a centre punch mark for the drill

Holes drilled and deburred, awaiting final cut and trim

12 slat ribs trimmed and sanded, waiting for bending. The other piece at the front is an access cover for the horizontal stabilizer, all complete waiting for installation.

​I discovered that the elevator tip rib form I traced out was undersized by about 2%.  So I corrected the form and made the tip ribs with the correct aluminum template.  Glad I caught this now, not later when I begin assembly.  Here they are awaiting bending:

​Very please at the progress I'm making.  Coming up this week, I'm going to the woodshop to final trim and sand my plywood form blocks and I'll start tracing out the longer spar and doubler pieces for the horizontal stabilizer and elevators.  Then I can start the assembly process!


​Progress!