Chapter 10, Build it rite, and it'll Bob. . .

Building the canard.

Feb 18, 2007, "K" jigs. I read on a other builder sites how time consuming it was to make all ten of the canard "K" jigs. The jigs that the canard foam pieces rest in for assembly after the shear web is done, and before you start on the canard spar caps. I ain' t the sharpest tack in the box, but I can make up for that with tools. . . Some of those are sharp!

I traced the single "K" jig on the stock ""M" drawings onto a sheet of drafting velum (Clearprint™), sprayed the back of that with "77", and pasted that to a scrap of 12mm Baltic Birch left over from cutting the wing jig cradles for chapter 19. Band sawed this to a rough outline, then finished to the line with a sanding drum in the drill press.

I then glued a strip of 12mm to the jig above, just touching the baseline of the tracing. Rummaging around in the junk drawer, I found a couple of new toggle clamps which I then screwed to the top of this. Trim up the sides on the table saw to make parallel, we're just about ready to rock.

Still using the scraps from the wing jigs, I ripped up a pile of 12mm birch to end up being 3" x 9.5". I put each blank into the jig made above, and penciled the outline onto the bottom. Head over to the band saw to rough them out, then back to the jig to make them real purdy.

Put a Hugh Jass top bearing pattern router bit in the router, attach that to the router table, and make some dust. Ba-da-bing, 10 minutes later I have 26 identical "K" jigs. I only need ten, I donated a few of the extras to be given as a door prize when I was at RR this year.

Sep. 10, 2008, Templates
Nothing serious here. Hot wire templates out of some 'junk' 18ga sheet metal gathering dust, the incidence and contour jigs out of 12mm Baltic Birch. I sanded the edge of the hot wire templates with 400 grit, will need to do it again just before I start cutting foam. Nicks on the metal = ski jumps on the foam.

Sep. 12, 2008 Lift tabs, etc.
A local aluminum scrap dealer (Alreco) had four square feet of .125" 2024-T3 in stock, with my kind of price on it. I laid out one canard lift tab using Dykem layout fluid, a scale (ruler), compass, scriber, and square. Don't start at the edge of the sheet, rather about .25" from the edge. The edge is often sheared, the metal is mashed and could be under stress there. Rough cut it out with a coping saw (the manual kind. Yes, it works in AL), sand just proud of the line with the bench top belt sander. Use this to trace the second one, cut as above, rough sand to contour. Aerosol contact adhesive the two pieces together, fine sand both to final contour, drill the holes per plans. Note the wood clamp on the lift tabs at the drill press, no scratches! Do something similar for the embedded attach plate. Now glue all the pieces together, drill the holes in the embedded plates.

While I was in '.125" metal mode', I also cut out the elevator hinges, aileron bellcrank brackets, and both trim lever/handles.

Dec. 16, 2008
Working solo, I cut up two 9' blocks of foam into the elevator and canard blanks with the wire saw. The pix to the right shows just about everything. How I used framing squares as guides for the saw, two short straight cut templates, the wire saw, gap in the table for the wire saw to drop into at the end of the cut, ... I opted to cut the elevator blanks off with the table saw.

Jan. 6, 2009
I had the 'usual suspects' up to Casa Hall for a hot wire party today. I repaid their help with a tub of "Road Kill Chili" for lunch. We cut two sets of canards out. One for me, one for Curt. They said the chili was pretty good. I might put a hot wire video up shortly. Since I'm dial up, it'll have to wait a bit... In the meantime, here's a pix of hot wire lag as Curt and I finished up a straight cut.

Jan. 7, 2009
I set each canard cores in a set of "K" jigs to cut them in half for the shear web. No clear instructions in the plans, but I know the canard lift tabs depend on a plumb cut. Read: canard incidence.

I screwed two 10' 2x4's to the table from the bottom. The canard cores stick out past the 2x4's a few inches, shouldn't be a problem.

The plans say "use 3" nails..." to jig the cores to the 2x4's, I used 2 1/2" finish nails spaced every 6-8 inches. DO NOT forget to angle them zigzag like. The plans also say to string line the trailing edge... I would have liked to, but the trailing edge is pretty well hidden between the jigs. I strung along the spar cap joggle (picture), and made a leap of faith that the trailing edge was also straight due to how well the cores were cut, and how they fit together. There was a slight bow in each foam piece, so the nails at the ends of each block were Bondo'd first, then I shimmed to the string line before Bondoing the centers of each block. I estimate 1/16" of bow.

Jan. 8, 2009
I marked the lift tab plate location with a sharpie, then cut a pocket with my trim router (it's real light) to a hair over 1/8" deep. Lightly pressing the plate into the foam showed me where I had to Dremel out for the nut plates. A bit of fast setting micro, then some silly-kone in the holes, and I'm off to the fiberglass cutting room...

The shear web layup was pretty straightforward, though I took 10 pieces of UNI to complete. Counting error on my part? I pre cut the lift tab crush plate BID pieces with a paper cutter. Picture of the peel-plied shear web. Notice I weighted the lift tab crush plate area, don't forget to shim one side up (the nails in the picture) so the cured surface will end up being something plumb.

Jan. 13, 2009
"K" jigs were set on the table in Bondo. Set the end ones first, make sure they're both level, then set up two string lines to do the rest.

Bottom spar cap went pretty well to plans, I filled the trough with nine strips of spar tape. After cure, I spline sanded smooth. Tip: be conscientious in filling the trough. Once cured, it does NOT sand as easy as urethane...

Jan. 16, 2009
Like some have done before me, I put the elevator hinge hard points in before glassing the bottom skin. I made a jig to cut the pockets, went pretty slick. The cutter is a fresh 1/4" drill bit chucked in the trim router, it just barely poked though to the top surface. Sand an 1/8" radius on the corners of the hard points, goop some micro on the sides of the hole with a stir stick, yer good to go.

Jan. 17, 2009
I applied peel ply to the trailing edge 'fish tail' with staples, putting at least 1/2" (but no more than 3/4") on the foam. Duck tape with the edge at the tangent on the leading edge, sand the spar cap again, tape up the lift tabs, and have at the bottom skin layup. Cutting 12" wide by 150" longs strips of UNI was an exercise, given all the clutter in my shop.

Jan. 19, 2009
Bottom skin cured under the tent. Bondo a pipe to the fish-tail, I used a 10' piece of 1" plastic electrical conduit cut in half and spaced out a bit. In hindsight, anything should work. It needs to support the rather flimsy fishtail, and provide a surface for the supporting blocks. I might have been better off finding (read: buying) another short length of conduit, but what I did worked.

As before, I bondod the outside support legs on first, then ran two string lines to add the middle three. Saw the fishtail off, no need to get real close (else you hit the staples). Score/knife the foam at the 1/2" mark, then grab a loose end of the peel ply and pull. I micro'd in a small radius at the junction of the shear web and canard tip foam joint, and allowed to cure slightly. Enough cure so that foam dust didn't stick. Much anyway.

Sand the top to approximate profile, enough that you can check for check for straight and level everywhere with the templates. Switch to 100 grit and finish up the profile. Don't forget to taper the leading edge from the bottom skin layup.

Sand the shear web surface again. The top spar cap was like the bottom, though I placed 12 strips. Peel-ply, cure overnight, then set in the tent for a semi-elevated post cure. Check the leading edge bottom skin taper job, and sand a joggle in the ends for later tip layup's

I opted to put my second NAV, and the GS antenna on the canard. Sand the high points off the spar cap first though, and use your templates (all of them) to check contour while your at it. The coax routing to the interior of the fuse is a close cut. You'll need to clear the elevator hinge hardpoints, yet stay 'inside' enough so you don't cut into the fish-tail (AKA: trailing edge of the canard). I stopped my cable channel cut just inside of the lift tabs, then final drilled at an angle with a long 3/16" drill bit through the bottom skin. I left about 20" of coax in excess, so that it will go direct to any radios. This may avoid a weight penalty of having to make a 10" extension... with two BNC connectors... and a BNC coupler. Light planes fly fast I hear.

Sand the trailing edge 1/2" lap joint again, and rip into the top skin layup. I found that when I was done wetting out a ply, I 'flipped' the hanging leading edge end up onto the top then brushed a bit of epoxy on it. This made for a relatively painless way of getting epoxy onto the lap with the bottom skin.

I have a small 'gull wing' depression at the trailing edge lap, near where the foam stops. I'll fill this with dry micro at contour stage. I'm leery of putting more epoxy (micro) on top of a bubble-gum stage lower layer.

Fork it, weez done :)

Tips

  • Make sure your table is straight, smooth, and level. I think this is good practice anyway.
  • If you think you goofed up when cutting the cores (huge wire lag, joggle, etc.), re cut them. Smooth straight cores are a definite asset.
  • Ensure all your jigs are identical. Not close, identical.
  • Don't sweat the top skin lap onto the bottom. Flip it up, brush it with epoxy, then lap it onto the bottom skin.
  • Cut your UNI strips wider than the plans call for. Unless you're real good at cutting 150" of UNI in a straight line.
  • Cut the elevator hinge hardpoint pockets (and install them) before glassing the bottom skin.
  • Make sure you have enough spar tape. Having extra on hand is pennies in the grand scheme of things.