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Miscellaneous Modifications

Date: December, 2007

After returning from a nice Thanksgiving at Bill and Marilyn Seibold's beautiful home in Bisbee, AZ (where they live right on the airport - nice!), I decided to start a bunch of mods/changes to the plane.

  1. Install a hidden rudder belhorn on the right winglet (I had done most of the prep-work when repairing the wing a year ago, and I had installed the conduit for BOTH belhorn cables during the original build, just in case).
  2. Rudder Hinge Attachment Mods:
    1. Remove the visible screws holding the rudder hinges onto both winglets - use Clickbond studs and fiber-nuts instead.
    2. Remove the non-flush rivets holding the rudder hinges to the left rudder and replace with flush rivets.
  3. Raise the incidence angle of the canard one degree to remove the elevator down deflection during cruise.
  4. Make a removable canard cover, inspired by what Bill Kastenholz has on his COZY MKIV, and similar to what I believe Velocities have. This will allow me to remove the forward fuselage cover without having to remove the canard.
  5. Add cooling air exhaust scoops on top of cylinders 3 and 4. Bill Seibold told me that his CHT's dropped 20-30F when adding these exhaust scoops to his O-320 powered COZY III, so I figured I'd try it.
  6. Replace the bolts in the rudder pedal cross torque tubes with taper pins, to remove the little bit of play in the system.

Hidden Rudder Belhorn - Right Winglet:

I used the hidden rudder belhorn as sold by CG Products. Very nice workmanship, as with all their products. I followed the standard installation instructions for the hidden belhorn. The hardest part was lining up the belhorn in the hollowed out rudder and getting it to line up with the end of the cable conduit in the wingtip. But the installation is pretty straightforward - no real gotchas. I've still got more than the 4" minimum deflection of the rudder as required in the plans.

Sorry - I have no pictures of the hidden belhorn installation, but it looks pretty much like it does in the installation instructions.

Rudder Hinge Attachment Modifications:

  1. I removed the nutplates from the hinge half that mounts on the winglet. First I made a "cover plate" from 3 BID that form fit on the back side of each hinge. Then I used the acrylic adhesive that came with the Clickbonds to bond them in place on the INSIDE of the winglet flange. Since this would offset the hinge centerline inward, I angled the studs rearward so that the hingeline could stay in it's original position. I then covered the stud bases with flox, put the "cover plate" over them, and attached the perimeter of the cover plate with 2 BID all around. The studs are bonded to the winglet and encapsulated with the flox and BID. Probably way overkill. Right now, it looks like crap, but once I fill and sand the exposed holes with micro, there will be no exposed fasteners for the rudders.
  2. One by one, I drilled out the rivets, c'sunk the rudder, and replaced them with flush rivets. Took a couple of hours.

New flush rivets for Rudder Hinge

Rudder Hinge held onto Winglet with Clickbonds and nuts, after glassing in place


New Removable Canard Cover:

I then carved some wing styrofoam to shape for a new canard cover, made some depressions 1.25" near the top of the canard, and then glassed a 4 BID flange 1.25" high to the canard, covered that with Peel Ply, and then glassed 2 BID over the top, lapping over the fuselage top, flanges, and nose door. After cure, I carved the back to shape, keeping the foam about 1" thick, and glassed the back with another 2 BID, with another layer of BID on the side flanges where it would mount to the canard flange. I also laid up 2 BID on the back side of the canard flanges for strength. 4 camlocs later, I had a removable canard cover and access to the 5 screws on the front of F-28 holding the fuselage top on.

Canard Incidence Angle Change (Increase 1 degree):

I removed the canard and sawed off the canard cover and foam, then sanded the canard top. I calculated the deflection that I wanted for the TE of the canard to get 1 degree of increased incidence, marked the existing TE position on F-28, and then sawed off the alignment tabs. I sanded most of the BID off of both the front and rear of the alignment tabs, as well as the mating areas of the canard TE. I then fixtured the canard in place, lowered the TE the required amount, and 5-min epoxied the tabs back on. I then glassed all the required BID back in place on the canard and alignment tabs. Next, I put a flox bed under the LIFT tabs on F-22, because they were no longer flush, being angled 1 degree. This ensures that the whole lift tab is flat on F-22, and is not under any bending stress when in flight.

This is the original canard and canard cover

Here are the old lift tabs, after canard cover removal

This is the canard positioned with the TE down to get the 1 degree of increased incidence, after the alignment tabs were sawed off

Carved foam for new canard cover

Glassed exterior of canard cover

Glassed cover in place on canard flanges - held with Clecos

Bottom of new canard cover - ready for glassing

Bottom of new canard cover glassed, in place on canard with Clecos, showing new lift tabs

Canard in place with new cover flanges

Finished canard cover with micro - just needs paint


New Top Cowl Air Exhaust Scoops for Cylinders 3 and 4:

I measured the position for the scoops, cut out the outline, and then hot-glued some foam in place to bend the cutout down. I then glassed 3 BID over the sides of the scoop area and dug out the foam. This was one cure cycle, and maybe 6 hours of work, total.

This shows the cutout scoop with the foam holding it in place for glassing the sides

These are the two new air exhaust scoops in the cowl top

Exhaust scoop over the cylinder head as seen from behind


Replace Rudder Torque Tube Bolts with Tapered Pins:

I used a tapered reamer and replaced the 4 bolts in the rudder pedal cross torque tubes with taper pins. Took a couple of hours, max. NO play in the system anymore. Not that I could feel it in flight, but it always bothered me when working on the rudder system.

No pictures for this - it's pretty self explanatory.

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