Ch25: Contouring the Canard
As those who read my Chapter 25 Finishing pages know, I'm fanatical about using the 45-degree sanding pattern. The one exception is when contouring the top of the canard. Walk down the EZ flight line and rub your hand over the tops of canards. Feel that flat spot over the spar caps? There are two reasons for this: (1) not enough fill over the spar caps, and (2) too much sanding flat-spots the top of the canard.
I cured this by using the soon-to-be-patented Hicks Milling Machine. (But you can steal the idea if you want to.) I set up my canard on the lay-up table I used years ago using those "E" jigs used in Chapter 10. I used my smart level to level out the table and to position the canard on the "E" jigs with zero degrees incidence. Once I was sure of it, I bondoed the canard to the jigs so it won't move during contouring. I used a canard sanding block that I made specifically for this purpose. It is shaped to the exact Roncz airfoil. You use it by placing a strip of sticky-backed sanding paper onto the block, then sanding side to side with it along the span of the canard. At each corner of the sanding block are lag bolts that slide along the top of the table. The lag bolts allow you to use the sanding block like a milling machine.
As more and more of the micro is sanded off, you carefully screw the lag bolts in by an eighth of a turn to lower the sanding block. You keep screwing in the lag bolts and lowering the sanding block until you hit the high spots! In this manner, you can precisely shape the micro and ensure a very straight surface finish with precisely zero incidence (no twist).
While this approach sounds anal, it's very QUICK and very PRECISE! Alot quicker than spline sanding and stopping to measure the canard shape with little templates. It's almost fool proof.
(BTW: The last picture is obviously staged because I am not wearing my respirator.)