Brian DeFord's Adventure
Building a Cozy MK-IV

Chapter 11


The elevators are hot wired from Styrofoam just like the canard. There are two sides which will be joined by a tube in between each side. The tube also has attachments for the control system so that it all ties into the fuselage. First thing to do is install the hinge bushings in the elevator torque tubes which have slots cut in them from the distributor. The slots are purposely undersized due to the tolerance of the tubing and have to be filed out to make the bushings fit. Once the bushings are installed the foam elevators are attached. Both sides get glass and the trailing edge is a glass to glass joint. I've got pictures of the elevators just after glassing the bottom side and then after glassing the tops.

Bottom glass on elevators
Top glass on elevators

After both sides are glassed and trimmed they get attached to the center section torque tube. This piece has control arms at each end which get fastened to the control system's pitch linkage. Here's a picture of the center section tube and the whole elevator system after assembly.

Elevator torque tube
Elevator assembly

The elevators are then attached to the canard. This is done by routing out some of the dense foam installed in the canard and potting the elevator hinges in these holes with flox. The hinges swing on a pin which is slid through the bushings installed previously in the torque tubes. The whole assembly is done at once and great care is taken to ensure the elevators have complete travel. This has been a problem for other folks, so I used a new template that holds the elevators in their full down position while the flox cured. After cure, I checked the travel and it was perfect!

Elevators being attached to canard

The next step in the chapter is to make wing tips for the canard. I formed them from Styrofoam and glassed them on both sides. They have a swept up appearance and look pretty cool. Here is a sequence of photos showing the tip fabrication.

Canard tip block
Canard tip upper surface
Canard tip complete

The elevator hinge pins are also removable from the tips and so a sleeve of tubing is installed at this time. Next the elevators must be balanced so that they do not flutter in flight which can be catastrophic. The balancing is accomplished using lead weights that are attached to the torque tube control arms and the ends of each elevator section. After adding the weights, the elevator should balance in a "nose down" attitude. The elevators have to be removed to add the weights. After adding the weights I checked the balance and it was perfect. The canard is then modified at each end to allow the weights to fit into small pockets on the underside. This involves cutting out the skin in that area, removing the foam and applying a glass layer to cover the exposed foam. The canard is now complete except for the final finishing and attaching it to the fuselage which happens in chapter 12.