Chapter 10: Canard Wing
I'd say that every builder looks forward to the day he/she starts the canard. After all, you finally get to be Burt Rutan and hot-wire a few cores. You also get to do something else other than the fuselage. Cutting the cores and building the canard turns out to be relatively simple. The hard parts are getting the spar caps exactly right, and keeping the canard straight and level through all the building steps. I found getting the spar troughs correct was tough. On advice from the archives, I overfilled and sanded the bottom trough back down to contour, or so I thought. When I glassed bottom skins, I ended up with a few hard ridges at the edges of the troughs. Nothing major, but I'll need extra micro I didn't want. I used bil kleb's hot wire saw and core templates, so that saved me a bunch of tedious work.
After Chapter 10, my basic canard with no elevators, fill, or paint weighed 22 pounds.
Lessons Learned:
1. I drilled a hole through the pipes for the hotwire saw and use a screwdriver to tighten the wire. The clamping force of the pliers kept collapsing the pipe, causing the pipe to buckle under load.
2. I used aluminum angles screwed onto the 2x4's and butted up against the aft canard cores to jig them bone straight. I drilled holes every six inches for drywall screw on both sides surfaces of the angles.
3. Clamp a piece of angle to the metal strip jigs that hold the inserts into the aft cores during micro cure. This ensures that the lift tabs will be in line with each other and are perpendicular with the chord line. It might be worth the effort to set the proper angle per the M drawings. I didn't do this and one lift tab is forward of the other. Plus, as I was installing the canard in Chapter 12, I noticed that neither tab fits flush against F22. I used flox and BID pads to get a matched fit. (This is quite common by the way. Don't get too hung up on trying to match the M drawings as I'm sure your mileage will vary anyway.)
4. Before slurrying the shear web, I temporarily stuck the wood dowels back into their holes to keep slurry from running into the holes.
5. It's faster to lop the slurry onto the shear web with a brush, then follow with a squeegee.
6. Before glassing the shear web, I measured the "perimeter" of the shear web at several locations and made a pattern. I laid up the slightly oversized, biased-cut UND (two layers at a time) on paper on my workbench, then trimmed to exact shear web dimensions. WORKED GREAT, no scissor trimming required!
7. I used 10 pieces of UND, not 9 for the shear web layups. My mileage obviously varied....
8. Remove the nails (or drywall screws :-) ) and remove the cores from the jig before pulling off the peel-ply from the shear web. Otherwise, you might rip the cores from the bondo'd nails, making huge holes in the cores and ruining your day.
9. I used a drywall screw to pull the silicone plugs from the lift tab inserts. Screw the drywall screw into the silicon plug, apply gentle heat, and pull out in one piece.
10. Although the plans give you the "one inch wide" dimension for the high density foam inserts (elevator hinges), you need to use the full-size figures 19, 49, and the full-size M drawing to get the length, height, profile, and placement of the inserts. My point is, remember the M-drawings. They'll keep you from asking embarrassing questions to the Designer.
11. I used 10 tapes on the bottom spar trough and 11 tapes on the top. I didn't experience any problems with the 2.5 inch tape. These layups were FUN! I purposely overfilled the bottom trough slightly, but after going through the hassles of sanding down to contour, I made sure to do a better job of filling the top trough "just right". (Note: Much, much later, I figured out a better trick while helping Clark Canedy with his canard. As we were glassing the bottom spar cap, I found that by dragging the F template along the foam (covered with duct tape), you could ensure the spar cap tape fibers conformed to the exact template shape. It was very easy to tell when we had the proper fill because the template would start picking up epoxy from the tapes. We would mark that spot and start the next tape layer at that spot.)
12. Make the E, F, and G templates out of 3/4-inch wide wood. In that manner, you can put the template on the canard and the level on the top of template without having to delicately balance everything. Else, the level falls off the template and punches a big ding into the canard foam.
[Previous] [Home][Next]