10th October 2011 - Fitting the cowl: part 1

I'd bought a cowl from Brian Alley back in September 2009 (The cowl arrives) and it has been stored in its shipping crate since then. Today I decided to make a start cutting it to fit. The first job was to get the join at the front to fit and cut out for the prop extension. Lots of sanding and use of a rotary burr on the inside angles got this to a good fit. The inside of the air intakes and the front of the sides were then match drilled together to fix the position of the joint between the cowl halves. Then the spinner backplate was installed on the prop drive extension to set the length for the cowl and first the lower cowl and then the upper cowl cut roughly to length. Temporary aluminium strips were clecoed to the firewall top, sides and bottom. Then the lower cowl was positioned and drilled and clecoed to the side and bottom aluminium strips. The upper cowl was then positioned and the correct overlap between the back of the upper and lower cowl established and the two halves match drilled and clecoed together. Then it was a case of marking minor changes to the rear of the two halves to centre vertically and horizontally the spinner backplate in the cowl opening and to ensure that there was an even gap of about 3/16" between the front of the cowl and the rear of the backplate, removing the cowl, making the adjustment, rechecking and repeating and repeating and repeating.....
Eventually a good fit had been established and it was time to take some pictures despite dusk falling. The next jobs are to properly cut and make the side joins, to fit the airscoop which will feed air to the carburettor, and to match drill and rivet permanent mounting strips to the firewall which will carry the cowl mountings.
I hope the pictures show what a super product Brian has produced. His cowl carries the lines of the fuselage perfectly and then blends them into the spinner surround. It also fits perfectly width-wise at both the top and bottom. Of course the overlap of the sides can be adjusted to make them fit perfectly as well. Using my O-235-C2C engine and a 4" propellor extension I had to cut off about 1-1/2" from the back of the cowl.

7th October 2011 - Carburettor control mount

The outer shields of the throttle and mixture controls need terminating on the engine close to the carburettor leaving the inner core to operate the carb levers. This needs some sort of bracket fabricating which was the task for today. One standard way of doing this is to bolt the bracket between the carburettor and the sump which is the approach I have adopted. First holes for the air intake and the attach bolts and a relief hole for the throttle arm to match the depression in the sump were cut out of a flat sheet of 0.071" 4130 steel using the CNC router (top of the picture). Then the routes of the cables were marked onto the sheet and the positions of the cable outer support tabs established. The tab for the mixture cable is at the very bottom of the picture and the tab for the throttle above and to the left. An angle grinder was then used to cut along the sides of the tabs and they were bent up into position. The throttle cable operates at right angles to the bracket base but the mixture control is at an acute angle of about 75 degrees. Next two pieces of steel were welded between the tabs and to the base to support them. Then the carb was positioned on the bracket and the vertical position of the cable runs marked to give a straight run and two pilot holes were drilled in the tabs. I've ordered a pair of "cable safes" from ACS which will clamp the outer cable through the holes in the tabs. The pilot holes will be enlarged to fit these when they arrive. I'm using bare end control cables as these can be cut to exact length. Finally some lightening holes were cut out to save a bit of weight.

The view of the bracket is from the bottom of the engine with the front at the top and the cables coming in from the bottom.

6th October 2011 - Aligning the alternator

It is incredible how much time seemingly simple jobs can take. The bracket on the engine I bought was originally intended for a generator and it was not possible to get the pulley of the alternator aligned with the flywheel with it as supplied. In order to rectify this it was necessary to cut off both mounting tabs and re-weld them further back and wiith a slightly different spacing. After repeated tack welds and test fits a perfect alignment was achieved and the welds completed. The bracket bolts to three of the crankcase joining bolts at the front of the engine and the original design has a tie bar from the front generator mounting bolt to the starter motor, presumably to stop the generator applying a twisting force to the case bolts and risking damaging the engine case. This bracket was not supplied with the engine so this was fabricated from some 0.090" 4130 steel sheet. Then an old over-long alternator belt was cut and used to measure the belt length required to get the alternator adjustment somewhere in the middle. This was then joined with tape and taken to the local car part shop where a 914mm belt matched the test length. Back home this was fitted in place and was exactly the right length. So a full day's work and one very small step forward!

5th October 2011 - Installing the engine

As a change from covering I decided to install the engine. This needs to be in place to fit the cowl and build the baffles which control the cooling airflow around the engine. Both of these are likely to be biggish jobs. The engine had been returned from the shock load inspection without cylinders which were not part of the inspection and were stored separately. In this state it was easy to manually lift the engine up onto a bench and then the aircraft could be positioned to align the mounting bolts. Once these were in place the cylinders were installed together with the fuel pump, the vacuum pump, the magnetos, the starter, the priming lines, the tacho drive, and the cylinder head temperature sender. I still need to make a bracket to support the throttle cable and mixture cable before I can mount the carburettor. Also, the alternator I'm going to be using doesn't align with the flywheel pully using the standard Lycoming mount so this will need to be modified. The engine is unpainted at the moment. Once everything is set up and the cowl and baffles are complete I will remove the engine as a complete unit and paint it before final assembly of the aircraft.

3rd October 2011 - The last priming?

The weather was good today so I got the last bits and pieces primed with the epoxy primer. This included the ailerons , flaps, rudder connection tabs, and spinner.
The spinner is a spun aluminium construction so has numerous rings of concentric surface texture. Once the basic primer coat was dry I applied numerous coats of a high build primer, sanding between each coat, to slowly bring the surface up to a smooth level. Tomorrow the paint from Stewart should arrive so I will have a first go at painting the spinner to a final colour.

2nd October 2011 - Fuselage covering complete

Over the last few days I've been adding the finishing tapes to the fuselage. The rivets for the top surface arrived in the post yesterday so they were inserted and the finishing tapes stuck in place over them. Then the finishing tapes along the join between the fuselage sides and bottom were applied. This was fairly messy laying on the ground and gluing over my head - the glue doesn't wash out of your hair but you can pick it off bit by bit. Finally the tape over the rudder post was applied.
The other little job completed was the bit of rework on the counterbalance on the left aileron. This was slightly out of alignment with the aileron and would have stood proud above the wing surface with the aileron in neutral position. So this was cut off the aileron spar and re-welded in the correct position.
Next job is to prime the aileron and flaps ready for covering them. The weather in the UK should be good for another couple of days so hopefully I will be able to get this done soon.

29th September 2011 - Rivet holes and more tapes

The stringers along the top of the fuselage need drilling for the pop rivets which will keep the fabric attached. I'm using 48" lines of rivets at 2" spacing on the outer stringers and 54" of rivets at 2" spacing along the centre stringer as per advice from Jim Clement. So the challenge was to drill 70+ holes in the centre of the circular stringers accurately spaced out without the drill bit wandering off centre and wrecking the fabric! After a bit of thought I decided to make a jig which would align the drill along the centre of the stringer and provide the spacing. I used a semi-circular router bit in the CNC router to machine a shallow channel in a bit of scrap aluminium. Then the router bit was exchanged for a 1/8" drill bit and the router programmed to drill two holes exactly 2" apart in the centre of the channel. The channel accurately located the jig over the stringers. Once the first hole was drilled in a stringer a spare drill bit was inserted through the jig into the ready drilled hole and then the second hole drilled through the other hole in the jig. Then it was just a case of moving the jig one space, with the spare drill bit popped into each new hole in turn and drilling through the other hole. It took about 30 minutes to make the jig and less than 10 to then drill the holes. I also then applied the finishing tapes over the bottom stringers and those on the left side of the aircraft. I now need to wait for the rivets to arrive from ACS before I can finish up the top of the fuselage and also still need to do the finishing tapes along the bottom longerons. I've also run out of 2" finishing tape which I need to complete the horizontal stabilisers and will also need for the elevators, flaps and ailerons so an order went in for another 50yds of that as well.