| Chapter 10 |
| Canard |
For building space reasons, I was forced to build components out of order so after Chapter 4 I decided to tackle the Canard (my first airfoil!!). First part of this chapter is to cut the blue foam bricks to size. First I needed a hotwire saw.
A quick trip to the hardware store yieled a 2x4 some electric conduit, paddle drill bit, and steel picture hanging wire, an extra battery charger. A few minutes of drilling and duct taping and I had it! One fancy hotwire saw ready for action! From an old 2x8 I created a giant resistor (as per plans) that I could use to limit power to the saw. Since I first needed to cut the blocks to size, I created straight cut templates from a small piece of fir molding.
My helper/wife Beverly was quite pregnant at the time and our single car garage becomes quite hot in the summer. But there we were! Our first cut, power to the saw! A low hum wire gets hot, into the foam lots of sizzle. Then nothing??? The wire had broken, quickly we pull it out leaving quite a large hole where the wire 'ate' the foam. String up the saw again, power, sizzle, first cut done! Reposition eveything, power, hum sizzle, break. Damn this time in a long cut, can't seem to get the wire out (the melting foam cooled around it). Hmmmm....String it up again, change the power setting, hum, sizzle, break!!!! This time we get the wire out. Okay, now I am getting upset, this can't be this hard to do!!! Looking at it the only thing that I didn't have was Safety wire ack!!! This hardware store variety steel wire was way too weak! Amazingly enough, my wife still is with me, even after a small emotional outburst about the hotwire saw, and the fact that she was forced to work in the very hot garage!!! Call wicks, overnight delivery of a one pound roll (I will be leaving soon on vacation and I really wanted to get this done).
Okay, new wire! Power, hum, sizzle...An hour or so later and all the blocks are cut to size! Template time!!! I cut and contact cemented the templates to some masonite (hardboard). Carefully, cut each one out and sanded smooth (at least I thought they were!). I placed the templates on the blocks leveling the water lines (NO TWIST!!). Beverly is back in the garage for more cutting. I explain the call numbers. We start our top cut, nice and easy seemed to work well! We try to do the bottom without flipping the piece over...bad mistake. It is hard to control the saw, we make a joggle, maybe even two. There is also a small nick on one of the templates that the wire likes to hang on near the aft end, underside, it causes a joggle in almost every cut. Sandpaper will hopefully get rid of them a little later. After a while we get the hang of things, and progress well. We make a good team, I am glad I married this girl!
I made the core assembly jigs according to plans (oops). The plans call for them to be a bit too short. I cut some extra 2x4 and bondo it in place. The nails that I have to hold the foam in place on the jigs seem a bit large, but it turned out they were just about the right size (just hate leaving those big holes in the cores!). A little bit of moving and repositioning got me ready to put these babies together! Be careful when aligning by sight as the spar cap cut creates an optical illusion! After assembly I put in the lift tabs and do the shear web layup. Nat says that build up in this area is the worse thing that can happen, so I spend a little time and make sure that each layer is either ~1/4" short or just right. When I drill out the shear web for the lift tabs, I must have nicked one of the back plates (damn!) because one lift tab bolt does not go in! I was tempted to tap it, but tapping a self locking nut plate isn't a great idea. Nat suggested to go in from behind dig out the plate and replace the nutplate. Sounds reasonable, but time consuming. I decide to try the tap method..after all if it just needs to grip the first one or two threads, I would be ok. This works, the bolt tightens, it actually takes a bit of force to get it all the way in. Leading edge gets cut and put on!
I spend a few hours one afternoon and cut and sand all the jigs for the canard. I set them up on the edge of my table and check...Hmmm, my table isn't square...That is the ledge of the table isn't straight. So I then use a string to line up all the jigs. After getting the jigs in place I plop the canard on and glass the spar caps. These are fun layups! I did have one problem though, the spar cap tape that I had received from Spruce (the monopoly of spar tape!) had several critical problems. First the key thread was broken in many places, apparently their fix for this is to tie it to the tows, which causes many problems when you tug on it to remove it. Then there were several places in the run that had epoxy already on the tows, to use them in this condition would ruin your day...Expect to order lots more. I complained to Jim Irwin at Spruce and he sent me extra tape for the damaged stuff. One other thing that I noticed is that some of the tows have cuts or breaks, most of the time these are covered with dried epoxy as before, but not always, so look out!!!Everything goes easy, wow that's a first!! When it came to doing the skin, I was out of helpers. So I cut the cloth a bit long and use my table and some spring loaded clamps to hold one end. I straighten the cloth from the other, works great! Skin layups take a long time, there always seems to be little problem areas!!! After the bottom cures, I flip the thing over and remove the peel ply and cut the fish tail. Hmmmm....something must have been off on the underside, because unless I change the shape of the airfoil there is no way that I can get this to sand smooth into the trailing edge. Reading ahead I see that all the other chapters use a layer of micro on top of the top skin on the TE to get it right. I do the same thing, and it looks ok...lets hope it flys that way. (Woo hoo my first airfoil complete!!)
Sorry about the pictures, the build pictures got blown away in the hard drive failure.
