Cozy MKIV - Chapter 11

Building the Elevators

Start Date: July 9, 1995

I started out by filing the corners of the NC-2 torque tube inserts to fit. You'd think that with the same vendor (Ken Brock making the inserts and the tubes) you wouldn't have to modify anything to make them work, but no. I cut 3" off the ends of the tubes (to match the shortened canard length) and then pop-riveted the NC-2's to the torque tubes. The plans don't mention that there's a left and a right version and you better pay attention to the orientation of the NC-2's, or else the hinge rod won't fit. One of the NC-2's was not perfectly aligned (after pop-riveting) so I had to use a long drill and reamer to open the hinge pin hole a few thousandths. I'd recommend having the hinge pin installed when doing the pop-riveting to ensure alignment. I sanded the tubes with 220 grit, and put them aside.

I then cut the elevator core templates out of 1/16" aluminum. Deanie and I hot-wired the four elevator cores. I THINK we could have done it with only two cores (I have a LONG hot-wire saw) but decided to just follow the plans. After cutting out the "J" and "L" jigs from plywood, I micro'ed the foam cores to the torque tubes. The plans seem to indicate that you could slip the foam over the torque tubes, but I found that if I tried that, the foam would break. I had to slide the foam onto the tubes lengthwise. Of course, I could no longer keep the torque tube jigs in place, since they'd rip the foam to shreds as well, so I applied the micro to the foam (and a little to the tube), and then slid the foam all the way onto the tube. I cut away the foam near the hinge openings, put the hinge pin and the jig(s) in place, and then rotated the foam so that it was flat while the torque tube was rotated all the way onto the jigs. I may be dim, but it took me a few minutes of staring at the picture in the plans to figure out the orientation of the foam and the torque tubes with respect to the jigs. Finally, the dotted line (a little hard to see) gave it away. Make sure the tube is resting on the jigs while the foam is flat. Here are the foam cores after micro'ing to the torque tubes:

glassed elevators I then cut the center spool piece from the aluminum tubing and attached the CZNC-12A offsets to the spool piece with the AN3 screws. I cut the glass for the elevator skins and layed up 2 UNI on the elevator bottoms. After sanding and fairing the glass to the torque tube, I layed up the top skin from 2 UNI. Here are the elevators after glassing and micro'ing:

hinge view After sanding, shaping, and straightening the elevators, I glassed 1 BID on the outboard ends, and then installed the NC-6's in the torque tubes. I assembled and jigged the elevators for assembly to the canard, routed the holes in the dense white foam of the canard for the hinge points, and then floxed the hinges in place (1/8" showing above the surface).

Here is the canard jigged for elevator hinge installation. You can see the hinges floxed in place, as well as the NC-6 insert and the end BID layup on the elevators:

top of elevator tips I jigged the canard for tip attachment, and the cut the urethane foam for the tips. I micro'ed and 5 minute epoxied the tip foam to the tips of the canard, and then shaped the tip tops. My hand sander had almost exactly the right curvature on the top to fair the tips into the top surface. Here you can see the urethane foam carved canard tip top surface prior to glassing:

bottom of tips I layed up the 2 UNI layers on the tip tops, let it cure, and then flipped the canard. I carved the tip bottoms by eye.

Here you can see the tip bottom surface prior to glassing:

I layed up the 2 UNI layers on the tip bottoms and used any and all excess micro to continue filling the canard, either on the top or the bottom. I let it cure, and at this point, I went to OSHKOSH '95!!!!!

hinge view After getting back, I sanded the tips and the canard. [This procedure would occur multiple times (and will continue to occur multiple MORE times). Any time I have excess epoxy, I mix up dry micro and fill either the top or bottom surface of the canard].

Once the tips were done, I drilled the holes for the hinge pins in them in line with the other hinges. Instead of using a plastic or metal tube through the holes, I wrapped Saran Wrap (tm) around the hinge pin and packed the hole with micro. This worked well. I then files and sanded the hinge pin tips to match the shape of the canard tips. Here's this business:

Next, I carved some foam for the outboard elevator mass balances and glassed them in place with two UNI layers. I made a cutout in the canard where the mass balances would have to recess, and glassed that with one BID. The inboard mass balances (as well as the torque tube offsets) from Brock Mfg. had not had mounting holes drilled in them, so I drilled them out and mounted the inboard mass balances. Here's the mass balances in their recesses:

End Date: August 20, 1995

Addendum:

I later determined that I had a problem with the shape of the trailing edge of the canard and the positioning of the elevator in relation to the canard trailing edge. I would caution all COZY builders to read the description, as a few builders have said they had the same thing happen to them, and the problem may be common one.

The Canard/Elevator Issue/Problem page describes the issue, some suggested solutions, and my plan of attack.

[Prev][Next]