Fill and Finish MLG Legs

The next step on the MLG legs is to fill the surface, smooth, and get a coat of primer onto the surface.  I have deviated from the plans and I am using steel-braid brake line and AN hydraulic fittings for the brakes instead of the Nylaflow tubing.  I added four studs to the lower surface of the gear leg to attach Adel clamps to hold the brake line in place.  The studs consist of a MS24694 #8 x 1/2″ screw that is placed through the center of a thin 1″ square wafer of phenolic (or fiberglass). The wafer and screw are adhered to the surface with a dollop of thick cabo, and the squeeze-out is used to make a smooth fillet around the wafer. This is then covered with 2x bid. When cured, the edges are sanded smooth.

The coarse weave of the carbon fiber and fiberglass socks on the gear legs were filled with Velocipoxy+micro, and contoured with a spatula.  After this cured, the legs were sanded smooth and excess micro was removed. Then, cabo was added to Velocipoxy until a syrupy consistency was obtained.  This mixture was spread on the surface of the sanded micro  with a squeegee to fill pinholes.

The pinhole fill layer was then sanded again to eliminate any ridges left by the squeegeeing.  After masking the booties and the upper portions of the gear leg (where they fit in the socket), two coats of UV Smooth Prime were brushed onto the gear legs. These coats were sanded smooth with 320 grit paper – this is easy since the UV Smooth Prime is so soft.

Once the UV Smooth Prime coats (which fill all remaining pinholes) are sanded baby-skin smooth, the gear legs were sprayed with 3 cross-coats of Stewart Systems Eko-Prime, which is a water-borne gray primer.  Eko-Prime is harder than the underlying UV Smooth Prime, and should be hard enough to fly with.

Fitting Booties on MLG Legs

I purchased the aluminum “booties” from the factory, as this is an opportune time to install them.  The booties are supposed to help with dissipation and spreading of the thermal load due to braking during the landing rollout.  Some folks have experienced sag of their landing gear legs due to the temperature rise in the brakes during extended taxi and hard braking.

My first job was to remove the existing axle from the gear leg.  This was impossible to accomplish without a hydraulic press.  Once the axles were removed, the cut line on the bottom of the gear leg was marked to fit the inside shape and angle of the bootie, while replicating the position of the axle flange.  The gear legs were (gulp) cut with a jigsaw – no turning back now…  Then the edges and corners of the gear leg were sculpted to fit the interior shape of the bootie socket.

After reinstalling the gear legs into the fuselage and verifying that the height and angles of the axles were correct, the gear legs were glued into the booties with Velocipoxy + cabo, with a smooth fillet around the edges of the joint.  After curing, the holes were drilled for the bootie through-bolts.

Aileron Bell Crank Supports

The factory is replacing the push-pull cable aileron linkage with a new pushrod linkage. There are now bell cranks mounted on the landing gear bulkhead that connect directly to the control torque tube that passes through the keel tunnel.  These bell cranks transfer motion to two long pushrods that pass through the MLG bulkhead and the firewall, connecting directly to the aileron control surface torque tubes in the engine compartment at the trailing edge of the wings.

The mating surface on the MLG bulkhead had to be filled and leveled to make a good mounting surface for the bell crank mounting bracket.  Then holes were drilled through the bulkhead for the pushrods.  I now have to figure out some way to determine the position of the corresponding hole in the firewall bulkhead….

Powder Coating NLG Parts

In an effort to make a few things look spiffy, I sent a bunch of metal parts to a local shop to be powder-coated.  Most of these parts were for the NLG actuating mechanism, the NLG fork, and the NLG shimmy dampener.  I also got the aileron bell crank brackets and the MLG leg booties powder coated.  My aircraft is going to have black legs – sexy.

SCAT Hose Flanges

I refuse to buy a bunch of the expensive metal flanges for the attachment of SCAT/SCEET hose for heating and cooling.  So I bought one each of the two most probable sizes if hose I will be using, and used them as a template to make a mold so that I could replicate them in fiberglass.  Mold release wax was used liberally on the metal, and then a liberal layer of cabo on the surface (poor mans gel-coat) followed by 4x bid was laid up on the outside of the metal template to make the mold.  I added graphite to the epoxy to make the mold black.  After smoothing and filling and waxing, I could punch out replicas of the SCAT hose flanges.  I will use these on the various air boxes and ducts for the cabin heating and cooling system.

Header Tank Modifications

I think I have decided to use a Continental IO-550 engine.  The engine mount bolts for the TCM engines come through the firewall in the lower corners, and the standard header tank interferes with that location.  So I have to modify my beautiful header tank by cutting the corners off.

The cut line was marked, and the oscillating tool made short work of the cuts.  Two thick lay ups (8x bid) were used to make the new corner walls.  These were coated, sanded, and coated with EZ-poxy to form a fuel-tight inside wall, then were bonded to the header tank with a fillet of cabo and 2x bid around the perimeter. New mounting ears were also added.