6th November 2011 - Carburettor heat control

One more little job completed today. A semi-circular shaped hole was cut out in the top of the airbox and one half of a piece of hinge match drilled to its straight forward edge. Then an aluminium flap was created to completely fill the normal entrance to the airbox when at right angles to the airbox top. This took lots of iterations of filing and testing to exactly fit the shape of the fibre-glass bottom of the airbox. Once this was a good fit it was match drilled to the other side of the hinge. The holes were then deburred and dimpled to take countersunk rivets. These were set so that the flush surface is inside the airbox to provide minimal disturbance to the airflow when in the normal open position. Then an actuator arm was rivetted to the top of the flap and drilled for a cable connection. The top of the airbox was then bolted to the carburettor and the actuator cable measured and cut. The system is designed so that the cable pull holds the flap open against the airflow when carb heat is required. In the normal closed position the control is fully forward and the cable is assisted by the airflow to keep the flap tight to the top of the airbox and allow the cold air into the carburettor. The hot air intake is mounted over the semi-circular cut out and is spaced off it to allow the heated air to spill into the cowl when carb heat is not required. When heat is required the suction of the carburettor will ensure hot air enter the airbox. The six tabs on the underside of the airbox top-plate hold the K&N filter in position.

4th November 2011 - Lower cowl nearly complete

It has been slow progress over the last few days. The weather has been poor so I haven't been able to get the fuselage outside and I'm spending time waiting for resin to cure. Finally though the airscoop is fully bonded to the cowl and the air intake created and lined up with the airbox. The process for creating the air intake is to cut the hole in the airscoop to match the intake to the airbox then shape and insert a foam plug that projects into the airscoop. Glass cloth is then laid up around this plug to create a tube on the inside of the airscoop that matches the airbox. The airbox will then have a rubber seal riveted around the intake that fits over the tube in the airscoop that has been fabricated. This ensures that outside air is rammed into the airbox by the propeller and speed of the aircraft increasing the effective air pressure at the carburettor and therefore the engine power. I just need to wrap one final layer of glass round the lips of the air intake to protect them and final fill and sand then the lower cowl will be finally ready for priming.

1st November 2011 - Brakes and cowl

The first job today was to complete the installation of the brakes. The top end of the master cylinder pistons were connected to the brake bars on the rudder pedals. Then the fluid intakes were connected to the "T" junction on the fluid reservoir. Finally, the fluid outlets were connected to the AN fittings screwed through the floor. These will then connect to the brake lines running down inside the leg fairings. Next the front cheek panels were covered on the inside with the same self-adhesive felt fabric as the baggage compartment walls. These were then clecoed into place ready for riveting to the firewall.
The posting on the 26th October shows how I had had to cut the airscoop in half horizontally in order to increase its depth. Yesterday, I had put a first layer of glass on the inside of the gap to join the two halves and put a slurry of resin and microballoons on the outside to level up the surface. I had also put a first layer of glass over the joint between the top section of the airscoop and the cowl proper. Today, the joints were sanded to create a key and two extra layers of glass were glued into place over both the joints. The three layers should be enough for a final result but I'll check it tomorrow to see if I think it needs one extra layer. Then the cowl was inverted and a slurry of resin and microballoons used to filet the intersection between the airbox and cowl. This can be easily sanded once set to get a clean smooth joint. Any resin left over from each layup is mixed with some white pigment and painted onto the inside of the cowl. Once completed properly this will seal the inside of the cowl and allow any drips from the engine to be easily seen. Finally three layers of glass were applied to the joint in the airbox. Once this is set I will filet the inside of the joint to make sure that the air can flow smoothly into the filter.

31st October 2011 - Spraying the underside

It was good weather today so the aircraft was tipped on its nose once more to spray the underside with the white EkoPoly topcoat. The paint has gone on pretty well with no runs or other serious blemishes. However the edges of the finishing tapes are very obvious. Before I do any more painting I'm going to have to make sure these are really stuck down and lie as flat as possible. However, this sort of learning experience is one of the advantages of doing the bottom first. This is not a view that is going to be routinely seen!

While the paint was drying I made a start fibre-glassing the cowl and airbox with the vinyl-ester resin that arrived this morning. Pictures of this tomorrow. Once the paint was properly dry the brake master cylinders were installed on their pivot and the front lower skin was positioned and clecoed and screwed into place. The fitting to the rear left of the skin is the fuel tank breather inlet and there is a hole to the rear right which will take the transponder antenna. I'm not fitting this yet as they are very vunerable and there is a high likelyhood I would break it off before ever flying. In order to fit this later I've drilled a 1" access hole in the inner front floor which will be filled with a rubber bung but will allow the transponder antenna to be installed and also, if required, serviced or replaced once the aircraft is in service.