15th November 2014 - Rain stops play

It has been a slow week as it hasn't stopped raining for more than a few hours at a time. However, I have got a little bit done. The new oil temperature sender was received and fitted so the engine could be ground run again.
The ground runs showed that, now the left magneto was working nicely,  the right magneto was probably also in need of some TLC. My engineers looked at it and established the points were badly pitted and needed replacement. With this done and the magneto re-timed the engine ran much better but #4 cylinder was still showing little compression when hand turning the propeller even with the engine warm, so I pulled the cylinder and had it looked at.
The bore, piston and rings all looked good. The exhaust valve was checked, usually the cause of valve leakage, but it was like new so all that was left was the inlet port. Once the inlet valve was removed, it was evident that both the valve and valve seat were covered with carbon. It looks like the cylinder has been run previously with inadequate valve clearance on the inlet valve. The valve was gently lapped and both it and the seat cleaned up nicely with no evidence of wear or damage. The cylinder was refitted and the head bolts torqued using my engineers borrowed socket extension. This has a curved shape and very thin ring to fit round the cylinders and allow the torque wrench to be applied - 25-ft pounds for the 3/8" bolts on the O-235 engine. All the valve clearances were checked and adjusted where required - a tight 5 thou clearance with the engine cold.
Then the engine was re-run and on checking afterwards the compression on cylinder #4 was much improved. This week, weather permitting, I hope to do a further engine run and then do a proper compression check with the differential tester.
I received the transponder back from Funkewerk this week. It had a display fault and although it was unused it was out of warranty - how many homebuilders suffer from things going out of warranty before they are ever used? Such are the timescales of homebuilding!
However, the service from Funkewerk was excellent, I received the transponder back within two weeks of sending it to Germany with a new release certificate and nothing to pay.
If the weather doesn't improve then the next job will be to upholster the seats - something that I can do inside in the warm.

3rd November 2014 - Seat belts and centre console

I only managed to get a bit of work done today before heavy rain brought an end to proceedings. I modified the panel at the bottom of the right hand door and eased the holes where the seat-backs fit over the fuselage structure and managed to get the seat-backs to fit slightly closer to the sides of the fuselage. Together these changes have made just enough room for the centre console to slide over the flap lever and between the seats. I only needed about 3/16" and the alternative was completely remaking the console. Before the console was screwed into position the lap-belts were fed through it and bolted to the central mounting point. The shoulder belts were then attached to the cables coming through the bulkhead at the back of the luggage compartment. The only things now left to complete the interior of the aircraft are  to screw into place the rear windows, make a "boot" for the bottom of the control column, and upholster the seat cushions.

2nd November 2014 - Seat backs painted and installed

Over the last few days I've painted the seat-backs and these have been test installed. Unfortunately the thickness of the fabric wrapping round the rear door post has removed the tolerance I had in the seat position and the centre console won't now fit between the seat-backs. This will require some "fettling" to solve but, as can be seen in the picture, darkness is coming early now that the clocks have changed so that will have to be a job for another day.

20th October 2014 - Door handles fabricated, doors installed

I made the internal door handles today. Using the ball turning attachment on the lathe I rounded both ends of two pieces of 8mm aluminium rod and one end of two pieces of 12mm aluminium rod. The 12mm rod was then cross-drilled and reamed to 8mm and drilled axially from the flat end with a 1/4" drill to match the latch spindle on the door. The 8mm rods were then pressed into the holes in the 12mm rod.
With the handles installed on the door spindles they were then cross-drilled with a 3/32" drill to take 12mm long 3/32" spring cotter pins (also sometimes called slotted spring tension pins). Then backing plates were "printed" to fit on the door and over the end of the 12mm rod. These were secured to the doors with double sided tape. The handles were then fitted and the cotter pins tapped in to hold them in place. Finally the doors were hung on the fuselage.
The second picture, taken through the passenger window, shows the pilot door shut. The handle lifts up to open to avoid it being opened accidentally.
Overall I'm quite pleased with the look of the cockpit and the way the doors fit into the framing.

29th October 2014 - Doors glazed

After superb weather over the last few days when I have been working in the garden, today it's raining so now the door paint is fully dry I completed glazing the doors. Like the rear windows, I'm just screwing and gluing the window to the frame. For the doors I'm using 5mm thick polycarbonate to add some structural stiffness. I've stuck some P-seal round the top, rear, and bottom of the door to seal it to the fuselage when closed. I've also applied P-seal to the fuselage along the front of the door jamb. Next job is to make some internal handles. As these will be used to pull the door in against the seal my original idea of printing them won't work so I'll get some aluminium rod and turn some up on the lathe - another item to add to the to-do list.

25th October 2014 - Rear windows and baggage compartment

It has been a superb autumn day today so I was able to get lots done working outside. The first picture shows a last view of the inside of the fuselage before the baggage compartment panelling is installed.
The first job was to cut out a pair of rear windows from 2mm thick polycarbonate sheet. These were drilled and countersunk to match the cut-out in the fuselage.
I don't want to use any sort of frame which just adds unnecessary weight so the windows are going to be bonded and screwed to the aluminium panels.
In order to make sure that the join stays flat I drilled some scrap pieces of aluminium angle to match the holes in the fuselage and then applied a bead of Dow Corning 738 adhesive/sealant to the inside of the frame. The window sheeting was then clecoed through the window frame and into the aluminium angles. I'm going to leave it like this for at least a week for the silicon sealant to fully set. Then the aluminium and clecoes can be removed and replaced with #6 stainless screws.
With the windows in their final location I could then re-install the baggage compartment panelling. The aircraft looks very different and much closer to finished once the inside of the fabric is hidden.

24th October 2014 - Rework and a few more "to-do" items

The first job today was to check out/fix the problems from the engine run.
A battery charger was attached to the alternator "B" lead and turned on. This confirmed that the ammeter sender was the wrong way round so it was then just a case of unbolting the two connections and reversing them. A repeat test with the charger confirmed this was now correct.
The CHT/EGT gauge was unscrewed from the panel and the connections of the two thermocouples reversed. Looking at the Westach instructions I can easily see why I got this wrong - the pinout in the instruction sheet doesn't really match my version of the instrument. The change was then tested successfully by using a heatgun on the two thermocouples.
The oil temperature sender was removed from the engine and the heatgun used directly on it - nothing. A 1K ohm rheostat was then connected in its place and the gauge responded as expected (low temperature=high resistance and visa-versa). Checking the sender with a multimeter showed it was open circuit so a new one has been ordered. This will take a week to arrive.
The intermittent fault with the fuel gauge was more of a problem. I had fitted a co-pilot PTT switch to the panel a few days ago. This required removing the KMD150 GPS and then reaching though the side of its rack to get to the back of the extreme left of the P2 side of the panel. I suspected that I must have disturbed a connection in doing this. The only way to find it was to remove all the instruments and the radio from the right side of the panel. In each case they had to come out through the side of the GPS rack. Once they were out I was able to establish that the problem was the positive voltage supply to the fuel gauge so this connection was re-made and the gauge started working again. Then everything had to be refitted. I just hope I haven't disturbed anything else! Next time the engine is run I will see if the vibration causes any more problems.
Once everything was back together I could get on with some new jobs. The lower cowl was test fit with the spinner and propeller in place. In no way would it go on because of the way the baffles fit under the lower edge of the airduct and into the spaces either side of it. I'll think about this some more but at the moment it looks like the propeller will have to come off any time I want to remove the lower cowl. This is less than convenient but certainly not a "show-stopper".
Then a hole was drilled in the cowl, just visible in the bottom right in the picture, to allow a fuel tester to be applied to the gascolator drain.
Pieces of baffle material were pop-riveted to the front of the airbox. These will fit over the internal extension to the port I made in the front of the lower cowl airscoop to roughly seal it and create a small ram-air effect.
Finally, pieces of heat resistant material were glued to the cowl using high temperature tank sealant where the exhaust pipes are closest. The edges were sealed with self-adhesive aluminium tape.
The lower cowl was then fitted in place and the propeller and spinner backplate re-fitted. The backplate only has 1/8" clearance from the cowl which confirms that without a different approach to the baffles it cannot be removed and refitted with the propeller in place.
I'll next run the engine once the new temperature sender arrives in about a week, Then I'll also look to adjust the vacuum regulator and further diagnose the low compression on cylinder 4. I've decided that the rear of the exhaust pipes are short enough not to require any further support so I've removed that item from the to-do list. New items have been added in red.

23rd October 2014 - First engine run

The replacement coil for the left magneto arrived today. My local aircraft engineering company is also certified for maintenance and release of magnetos, so under their supervision the new coil was fitted and I learned how to re-assemble the magneto and time the rotor arm correctly. The magneto was then put on their test bed and a healthy spark demonstrated.
Back home the propeller was used to turn the engine until it was at top-dead-centre on cylinder one. A TDC position is marked on the flywheel but will correspond to either cylinder one or cylinder two. As my engine has conventional tappets it was easy to check which by removing cylinder one's rocker cover and ensuring that both valves were closed. The crank was then rotated until 25 degrees before TDC which is the standard firing position for this engine. The magneto was also then positioned in the firing position for cylinder one using a special pin though a hole in the top of the magneto to locate a matching hole in the rotor arm drive gear. The magneto was then inserted into its position in the accessory housing at the back of the engine.
Then the flywheel was repositioned in the 25 degree before TDC position. When timing an impulse coupled magneto it is essential that the engine is moved past the point at which the impulse coupler trips and then rotated back to the 25 degree position. Using the magneto timing device  I made a few days ago, the magneto was then turned until the points were just opening and the magneto clamped into position.
As a final check the plugs for the left magneto were removed (cylinder 1 & 3 top, cylinder 2 & 4 bottom) and the engine rotated with the propeller. A spark duly appeared at the correct plug and at the correct time allowing for the delay of the impulse coupling (this is a mechanical device that delays the spark when engine revs are low to allow for easier starting).
Then it was time to try and start the engine. First job was to secure the aircraft to ensure it couldn't run away. To do this it was chocked but also chained to the back of my car! My neighbour, Daryl, kept watch to ensure that no-one came close to the propeller. The elevator trim was moved to hold full up elevator to ensure the tail wouldn't lift.
I've fitted a conventional pump primer to the engine which feeds all 4 cylinders; 4 strokes were used. Then with the master on and then left impulse-coupled magneto on the starter button was pushed. A few coughs and splutters ensued but the engine didn't want to run. Then Daryl saw some liquid under the aircraft. This proved to be water and further inspection found that the airbox was full of it! Obviously the recent rain had somehow ended up in the airbox and the poor engine was trying to start on a fuel/air/water mixture. The airbox should have had a small hole in its lowest point - it has now! To solve the problem temporarily the airbox was disconnected and left hanging down below the carburettor. The spark plugs were removed and dried. The engine was turned over on the starter without the plugs in to ensure there was no water in the cylinders and then the plugs refitted.
Finally it was time to try again and this time the engine started perfectly. It ran for a few seconds on the prime before running out of fuel, presumably because the float chamber in the carburettor had been completely empty. However, after re-priming the engine started and with the right magneto also on began to run smoothly.
Then it was time to do some preliminary checks:

• the cylinder head temperature was registering off the scale but the exhaust gas temperature gauge was not moving - looks like the thermocouples are wired the wrong way round. 
• the bus voltage looked good but the amp meter was showing a large discharge - I had a 50:50 chance of getting the current sensor round the correct way and had guessed wrong.
• The oil pressure was good but the oil temperature seemed pegged. Either the vernatherm hasn't opened or there is a fault in the temperature gauge or sender- another thing to check
• The fuel gauge had stopped working - presumably a bad connection somewhere
• The vacuum gauge was reading a bit low but the gyros were definitely spinning up

With these basic checks completed the engine was stopped and an external inspection carried out:

• No oil leaks
• Nothing coming loose
• High cylinder head temperature confirmed as a wiring error
• Good compressions on cylinders 1, 2, and 3 but not on 4
• Crankcase still cool so oil temperature not yet confirmed as an issue

Given that there was nothing untoward the engine was restarted and run again for ten minutes. This time the engine was run up to 2000 rpm to allow for proper mag-checks which were well within limits. A very quick burst at full power saw a static RPM of 2250. Time to stop annoying the neighbours and pack up for the day.

18th October 2014 - Magneto Woes and Timing

Yesterday I finalised all the jobs on the check-list needed to attempt a first engine start. However, things did not spring into life as hoped.
The engine starts on  the left magneto only which has the impulse coupler but nothing happened. Fault finding showed that the secondary field winding in the magneto coil was open circuit and no spark was forthcoming. I will liaise with my engineer Monday to see if the coil can be replaced or a serviceable magneto will need to be procured.
When the new magneto is refitted it needs to be timed to the engine so that the points open at 25 degrees before top dead centre.
To do this a circuit is required that can tell if the points are open or not measuring from the P-lead connection. The problem is that when closed the resistance to ground is zero, when they are open it will be the primary coil resistance which is roughly 0.7ohm.
Commercial magneto timing testers are widely available but expensive and based on very old technology so I decided to build my own.
As with the commercial offerings, the key to the design is to feed the P-lead with an alternating current. The inductance in the primary will then act differently to the short to earth and the difference can be measured.
The circuit uses a picaxe microchip to generate a 2KHz square wave which is applied to the P-lead through a 330 ohm resistor. The voltage on the P-lead is then rectified using a schottky diode, converted to DC using a simple single pole filter and applied to an analogue input on the picaxe. This continuously measures the voltage and if it is above a threshold level (6% of the microprocessor supply voltage) lights an LED. The circuit is powered by a single 3V coin cell and works perfectly. Total cost approximately $5!

16th October 2014 - Voltage Regulator installed

Although you can buy voltage regulators fairly cheaply, particularly second hand, I decided to build my own. There is a single chip solution available, the L9911 from ST Microelectronics. This is constructed with an easily mountable package like a large transistor and the pins are on a 0.1" pitch so it is easy to mount on standard stripboard (Reinforce the tracks with solder as currents up to 3 amps will be flowing). The tab on the package is earthed so this can be fastened directly to the aircraft chassis via the aluminium project box I have chosen. Some thermal conductive paste was used to ensure that any heat generated would be dissipated to the firewall. The regulator needs a light or LED connected between the "ignition" pin and the regulator supply which it senses and this turns it on. I used a panel mount LED with a 1K ohm resistor as a current limiter.
Unlike most aircraft regulators it needs a phase input from the alternator which you take from between any one of the pairs of diodes. Some alternators have a connection for this. Mine didn't but it was easy to add an extra wire to the alternator. The regulator uses this to sense that the alternator is turning and switch the field in sync with the rotation. This helps to reduce any chance of radio interference. The regulator also only applies a small current to the field if the alternator is not turning unlike most aircraft regulators which apply full current any time the voltage is below the regulator set-point. The LED illuminates if the alternator is not turning and goes out when the regulator senses the phase input.
Other than that you only need to connect the +ve supply and the field output as per any other regulator. The large capacitor is used to smooth the regulator +ve supply which it uses to compare with the set-point and control the field current. Total cost of the completed regulator, including the box, was less than $20.
Today, I also installed the oil temperature sender and replaced the internal battery in the KMD150 GPS. This is a bit of a fiddle as it requires the unit to be stripped down. However, the new battery should last about 8 years. There are good instructions on the web how to do this if you google "KMD150 battery replacement".
So that is another three items ticked off the check list:-)

6th October 2014 - Final To-Do List

The bad weather today gives me an opportunity to pull together a list of all the outstanding items to complete the build. Many of the items will just take a few minutes to do but there are a number that will take a few days each. However, overall the end is in sight :-)

I'll mark items in green as they are completed. 

Engine:

1. Build and test a voltage regulator for the alternator. I'm doing this using the L9911 chip.
2. Install the voltage regulator and re-install alternator
3. Install ignition leads
4. Install Oil temperature sender
5. Install grommet in baffles for engine breather tube
6. Install additional bolts for the starter motor and propeller spacer and wire safe-tie where applicable
7. Install the propeller and spinner, safe-tie the propeller bolts
8. Test installation of lower cowl with spinner in place, trim front of baffles as required
9. Install the seal which will connect the airbox to the lower cowl
10. Drill the cowl for access to the gascolator drain
11. Partially fill the fuel tank, check the fuel flow with gravity and the electric fuel pump
12. Calibrate empty setting on fuel level gauge
13. Remove/clean/reinstall  the fuel tank filter
14. Remove/clean/reinstall the gascolator filter
15. Test run the engine checking; oil temperature and pressure indications, cylinder and exhaust gas temperatures, vacuum system, charging system.
16. Mount a high power TVS across the alternator output
17. Install the over-voltage crowbar circuit
18. Procure, fit, and test replacement oil temperature sender
19. Adjust vacuum regulator to get vacuum into "green" arc, if not possible replace regulator and/or vacuum pump as required
20. Remove/clean/reinstall the carburettor filter
21. Compression test the cylinders, rectify if required
22. Remove engine, paint, reinstall
23. Inspector sign-off for engine installation
24. Inspector sign-off for fuel flow

Cowls and Spats

1. Install heat shield to inside of cowl where close to exhaust system
2. Prime cowls, fill pinholes, sand and re-prime until smooth
3. Paint cowls with Insignia white Eko-Poly
4. Apply glass cloth reinforcement to top of leg fairings
5. Prime and topcoat leg fairings
6. Prime and topcoat wheel spats
7. Fabricate, paint, and install intersection fairings for wheel spats to leg fairings
8. Fabricate, paint and install intersection fairings for leg fairings to fuselage

Panel

1. Install P1 headset power outlet
2. Remove Transponder, return for repair to display, refit
3. Replace battery in KMD150
4. Update database in KMD150
5. Set Mode S address for G-CIJY  in transponder
6. Install P2 PTT switch in panel

Fuselage

1. Print knobs for the fresh air vents and install the vents.
2. Get new lens for rear navigation light, paint lens holder and install
3. Rework fabric cover over left door internal structure. I'm not happy with the current result.
4. Apply EkoFill/EkoPrime to left door internal skin
5. Topcoat left door with white EkoPoly
6. Mask fuselage as required and paint internal areas behind rear door post and in front of rear window
7. Redo fabrication and installation of two-off door and  two-off rear fuselage side windows using polycarbonate sheeting rather than acrylic
8. Install windows in rear fuselage and doors
9. Repaint seat floor panels and install
10. Repaint left door jamb panel and install
11. Fabricate internal door handles and install
12. "Print" and install covers for the areas in the fuselage where the elevator torque rods pass through the fuselage fabric.
13. Install baggage compartment panelling
14. Install seat belts and install cover over flap lever, must be done at the same time
15. Paint seat backs
16. Install seat backs and panel between seat backs
17. Install doors
18. Install wings and design/fabricate/paint/install fairing to cover the gap between the wing and fuselage
19. Design/fabricate/paint/install strut to wing intersection fairing 
20. Install GPS antenna
21. Install radio antenna
22. Inspector sign-off for Fabric and dope for quality

Controls

1. Make drainholes in control surfaces
2. Assemble wings to aircraft and install flaps and ailerons
3. Inspector sign-off for complete mainplane structure
4. Inspector sign-off for flying control assembly

Trimming

1. Re-paint spinner and paint backplate to match
2. Purchase and install self-adhesive registration lettering for G-CIJY to fuselage and left wing
3. Design small-scale colour trim to "finish" aircraft
4. Purchase and install self-adhesive fine-line colour trimming
5. Polish paintwork
6. Fabricate and install boot for control column
7. Upholster seat backs and seat bottoms, use velcro to fix in place
8. Cut carpet to fit foot well and get edges bound, secure with velcro

Preparation for test flight

1. C of G check
2. Component record datasheet completed
3. Identify test pilot
4. Request permission to test fly from LAA
5. Transport to suitable airfield
6. Compass swing

Other

1. Calibrate full fuel setting on fuel gauge when tank is first filled
2. Install/UV block/prime/paint tapes to join horizontal stabilisers to fuselage once angle of incidence of horizontal stabilisers is finalised.

5th October 2014 - Putting it all together: empennage complete

I've had a great couple of days continuing to final assemble the aircraft. The list of jobs done includes:
- Installing the transponder antenna in the front underside panel. This was done through a 1" hole previously drilled in the forward floor which was then sealed with a blanking grommet.
- Installing the rear floor panel.
- Drilling a 1" hole in the combing over the location of the fuel sender to allow this to be calibrated. This was then sealed with another blanking grommet.
- Installing the combing.
- Installing the main window
- Installing the fuel filler cap and inner and outer surround plates.
- Installing the front side windows.
- Installing the window surrounds and over-door panelling.
- Opening up the two access panels, one for the elevator push-rod connect and one on the underside to allow bolting the leading edges of the horizontal stabilisers. This was done with a scalpel cutting radial lines from the centre to the support ring. The "orange" segments of fabric were then trimmed to about 1/2" and folded and glued onto the inner surface of the support ring. The cover for the elevator pushrod connection access panel is just visible in the third picture.
- Installing the rear spar carry through inner and outer covers. These together make a box which acts as a channel for the cables to and from the wings. The radio and GPS antenna will mount in the outer cover. In the third picture the outside temperature sensor can be seen coming out of the box and secured in the space which will be between the fuselage and the wing.
- Installing the tailwheel.
- Installing the rudder and the tailwheel pushrod.
- Attaching the rudder cables.
- Installing the horizontal stabilisers and bolting the leading edge into the best estimate position to get the correct incidence for the first test-flight. The inside of the spars of the horizontal stabilisers and the inside of the tube on which they mount were both treated with ACF-50 corrosion preventative spray before assembly.
- Cutting holes for the elevator horns to enter the fuselage and installing the elevators. Bolting the elevator horns to the elevator pushrod.
- Installing the baggage compartment floor.
- Registering the aircraft with the CAA. The registration will be G-CIJY.

Tomorrow it is due to rain all day so I'll compile a to-do list for completing the build and post that on the blog.

2nd October 2014 - Panel Updated with new radio

Over the last couple of days I have:
removed the SL30 and the Sigtronics intercom and all their wiring;
replaced the intercom with the new Funkwerk ATR833 radio (it includes an intercom which is supposed to be quite good) and rewired the four headset sockets;
moved the KMD150 up in the radio stack;
fabricated, painted and installed a blanking panel below the KMD150;
wired the KMD150 audio warning output into the radio's auxilliary input;
installed the compass on the central window support using a home "printed" mounting bracket;
turned down on the lathe the throttle knob which was just fouling the P2 control column. The pictures show the before and after configurations.
Overall, 16 hours work, additional cost, and no functional advantage - thanks EASA!

29th September 2014 - Wheels and brakes complete

Once all the masking paper was removed from the fuselage the first job inside was to re-install the strobe power pack. This is behind the back of the baggage compartment so needs to be in place before the interior can be refitted.
Next the spat attach brackets and spacers were removed, degreased, primed, and top coated. Once dry they were re-installed and the brakes refitted and the bolts wire-wrapped.
Then using a simple pressure system the brakes were filled with fluid from the bleed nipples. By filling from the bottom up there should be no possibility of airlocks.
Both brake peddles seem completely solid with no evidence of any air in the system so that seems to have worked.
It is great to be putting things together into their final state. Unfortunately the next job is to replace the radio in the panel. EASA have decided that all new aircraft registered now can only have  8.33MHz capable radios fitted. So my Garmin/Apollo SL30 will have to be replaced with a different unit.

18th - 28th September 2014 - Painting the fuselage

We have had a spell of calm dry warm weather so this has provided the opportunity to finish paint the fuselage.
First a coat of smoke grey EkoPrime was sprayed onto the fuselage and rubbed down with 320 grade open coat sandpaper. Then over three days the top and fin, the bottom and the two sides were gloss-coated with Insignia White EkoPoly.
As I'm doing all the painting myself and don't have any sort of paint shop available the spraying was done outside. As always a range of small insects embed themselves in the paint before it dries but these can be polished out once the paint is fully hardened without leaving too much damage.
Overall, I'm reasonably pleased with the finish I have been able to achieve. It isn't professional quality but it is more than acceptable and I have the satisfaction of knowing that I have done everything on this build myself.
With the painting complete I can now remove all the masking and start to put the aircraft back together.

16th September 2014 - No longer baffled except for one thing!

The baffle material was riveted into place and the the edges rounded. In the four places where the sections of baffles meet the overlap in the material was screwed together rather than riveted to allow the sections to be removed. The inter-cylinder baffles were fitted and tie rods threaded to pull the under sections of the cylinder baffles together. Vans supply stainless steel rod for the tie rods and assume you will have a 6-32 die cutter to hand. Holes were cut in the rear baffles to mount the plates through which the plug wires will pass
The idea of the baffles is that the air flowing in through the ducts in the cowl is forced between and round the cylinders ensuring even cooling. The flaps in front of the no. 1 and no. 2 cylinders try to balance the cooling front to back.
Once all this was finished the top cowl was fit into place when my mistake was revealed. My perfectly placed Oil filler flap was on the wrong side of the rear baffle. It provided access to the rear cylinder and nothing else!
Luckily mistakes in fibreglass are reasonably easy to correct. The section of the cowl around the door was cut out as a rectangle together with a  similar sized section behind it. The rectangular piece was then cut in half so that I had a piece with the door and its surround and a second blank piece.
With the cowl fastened to the bench with some plastic sheet below it, the two pieces were then glassed back into the cowl in the reverse direction. A bit of filler made good the joints. Then a coat of primer was applied to the whole top cowl to reveal the inevitable pinholes in the fibreglass. A mixture of micro-balloons and resin is used to fill the pinholes. The picture shows it prior to final sanding. This is a mind-numbing job so I'll be doing it a bit at a time as motivation occurs.

14th September 2014 - Baffled by baffles: day 4

Once the spacing to the cowl was checked and rechecked the final cut of the baffles was made and the edges smoothed and deburred. The second picture, taken through the oil filler door shows how the front section follows the line of the cowl with the 1/2" spacing. Then a start was made on cutting and fitting the baffle material before darkness stopped work.

30th August 2014 - Baffled by baffles: day 3

Day 3 of the baffle construction saw the basic structure completed. The left front baffle was completed and the centre section of the right front baffle extended. Balanced on the top of cylinder 1 you can see the spacer I "printed" to fit on a Sharpie pen which I used to mark a cut line around the top of the baffle to provide the 1/2" clearance to the cowl.

28th August 2014 - Baffled by baffles: day 2

I'm behind on the blogs but work has continued. On the 28th I spent another day on the baffles. The right rear baffle was riveted together and then work started on the right front baffle where it passes behind the flywheel.
As before the kit from Vans needed significant modification to fit my O-235-C2C engine. However, using the kit has made it much easier than starting from scratch. As can be seen the panel that extends along the side of the flywheel is not long enough so this will need an extension riveting into place. This is because the Tailwind cowl requires a 4" prop extension unlike the Vans cowl..
A first cut of the top of the baffles was made to allow the cowl to be fitted into place. This was done by repeatedly cutting and then test fitting the cowl until it would just sit in place. Eventually the baffles will be trimmed to leave a 1/2" gap to the cowl which will be filled with the flexible rubber baffle material.

27th August 2014 - Baffled by baffles: day 1

The Vans baffle kit arrived today so I could make a start fitting it. Vans only do a kit for a dynafocal mount O-320 engine and I'm using a straight mount O-235-C2C so I expected that some "fettling" would be needed. The first obvious problem was that the mounting holes where the side baffles bolt onto the cylinders were in completely the wrong place although the cut-outs for the rocker covers were thankfully completely accurate. So cover plates for the incorrect holes were fabricated and riveted into place. Then correctly placed holes were drilled and the doublers  and strengthening angles riveted into place. Next the rear left baffle was test fit. This needed many-many iterations of trimming to fit round the parallel engine mount. Finally a good fit was achieved and it was riveted to the rear left-side baffle.
There is a mounting bracket, just visible in the picture, screwed to the rear two top engine join bolts. This also required much adjustment to fit on the bolts and clear the engine crankcase but eventually it was in place and the left rear baffle was match drilled and clecoed to it. This will be bolted up when the baffles are finally installed.
The right rear baffle was easier to get fitted snugly around the engine. It will need a spacer to rivet it to the rear-right-side baffle but that is a job for tomorrow. 8 hours work on the baffles so far!

21st August 2014 - Exhaust system complete

The extra 45-degree section of exhaust arrived today together with a 6' length of 2" scat tubing (this stuff is so expensive!). This allowed me to finalise the exhaust, seal all the joints with exhaust putty and clamp everything up with heavy duty clamps. Then the scat tubing was cut to provide links between; the carb air box and the air muff, the air muff and the cabin heat valve on the firewall, and the air muff and a flange which will be riveted to the baffles to get a source of fresh air. This pretty much completes the engine install apart from the baffles. The other little jobs are just to route the engine breather, plumb the vacuum pump, and connect the fuel pump pressure relief overflow.
No pictures, but I have also been working on tidying up the joint between the lower and upper parts of the cowl. As delivered the step overlap is not deep enough to get a smooth transition so additional fibreglass has been bonded onto the lower cowl to build it up. Next job will be to blend everything together with copious amounts of filler.

19th August 2014 - Cabin and Carb Heat Muff - part 2

The 2" holesaw that I had ordered arrived today so I was able to drill three holes in the heat muff. Three lengths of 2" aluminium tubing were cut and welded into the holes. This completes the heat muff. 2" scat tubing will be used to plumb up the air intake (bottom right), the cabin heat (bottom left) and the carburettor heat (top left).

18th August 2014 - Left exhaust pipe, oil filler door

The exhaust system is now complete pending arrival of one extra 45 degree bend and some heavy duty clamps for the overlap joints.
The left system is constructed the same as the right except that the bend which angles the exhaust inwards and down is a 60 degree angle rather than 45 as the cylinders on this side of the engine are further to the rear of the engine. For final assembly I'll use a jointing paste on the overlap joints.
With the exhaust complete, I used the extra time today to cut out the oil filler door flap from the upper cowl. The removed section was riveted to a section of hinge and this and some stainless steel strip was riveted to the cowl to mount the door and provide a lip for it to sit on. A hole was then drilled through the door and the strip and a catch installed. I still need to  fibreglass the strips onto the cowl to provide extra support and get rid of any gaps.

16th August 2014 - Cabin and Carb Heat muff: part 1

The straight section of pipe on the right exhaust is the only place that will take a sensibly-sized cabin and carburettor heat muff.
A 8" length of 4" diameter aluminium tubing was used as the outside of the muff. Two end plates were cut using the CNC router from 16SWG 6061-T6 aluminium sheet to fit the ends of the 4" tube and with  2" holes asymmetrically placed to position the heat muff clear of the lower cowl.
1.5" lengths of 2" aluminium tubing were welded into the holes. The forward one was positioned inside the muff to allow it to slide forward as far as possible on the exhaust pipe. The rear one is on the outside and once welded slots were cut into it to allow it to be clamped to the exhaust pipe using a worm drive jubilee clamp.
Then the end plates were welded onto the 4" pipe to complete the muff hot air box. Next step is to cut an inlet hole for the fresh air supply and two outlets; one for the cabin heat and one for the carburettor heat. These will have short lengths of 2" aluminium tube welded into place to take the 2" high temperature scat tubing which will be used to plumb everything up.

15th August 2014 - Right side Exhaust fabricated

I've decided to build a 2-pipe exhaust system with cylinders 1 and 3 feeding into one tailpipe and 2 and 4 into the other. This isn't as efficient as a crossflow system (1 & 2, 3 & 4). However,it is much easier to construct. The system is made from the mild-steel custom exhaust build parts available from jetex.co.uk.
As a start, I bought 2-each of 1m straight , 90 degree bend, 60 degree bend, 45 degree bend, and 30 degree bend.
Then it was a case of slowly fitting and cutting the sections in an iterative fashion until a route was established that cleared the cowls and routed out of the slot in the bottom of the lower cowl.
In the event I used a 90 degree bend off cylinder 1 connected to a 45 degree bend to angle the exhaust in and down. A 30 degree bend was used from cylinder 3 which was fit and welded to a machined hole cut in the 45 degree bend (took over a couple of hours to get a matching hole and end-profile). Next a section of straight pipe was welded on. This will take the hot air box for the cabin and carburettor heaters. Finally another 45 degree was used to create the tailpipe angling the exhaust down and away from the fabric under the fuselage.
I still need to make a support for the rear of the exhaust. This has to be connected to the engine rather than the airframe so that as the engine moves on the mount it doesn't stress the exhaust.
The routing for the left side will be similar but because the 2 and 4 cylinders are more to the rear a sharper angle will be needed before the straight pipe and this will also be shorter. I think this means that worst case I will need to buy two extra 45 degree bends, best case is just one more.

14th August 2014 - Spats and brakes

The Tailwind has taken something of a back seat recently however, finally some progress.
Some time ago I bought a pair of second hand Vans' spats. These are the original non-pressure-recovery versions. These were drilled for fastening to some sort of mount on the inner side of the wheel and onto the axle nut on the outside. The challenge then was to fabricate some sort of mounting bracket and fasten it to the airframe in some way.
Before I could start I needed to find some way of jacking up the wheel so I could work on the axle. I found a bit of spare steel tubing of about the same diameter as the undercarriage leg. This was cut in half and some scrap plate welded on and drilled so it could be clamped to the leg. Then a bit of angle iron was welded on at an angle so that a car jack could be used to lift the wheel. This works well but marks the paint so I will have to line the inside with some rubber.
The spat mounting plate needed to be kept clear of the brake disc so 1/2"-long spacers were cut out of some steel tubing. The 1/4" bolts that secured the brake mounts were then replaced with longer ones to take the spacers. A bit of scrap aluminium was then progressively cut to fit the bolts and clear the brake caliper. The wheel was then replaced and  the spat test fit. Holes were drilled in the mounting plate and the spat clecoed into place. This was then repeated for the second gear leg. The spats were positioned so that they were horizontal with the aircraft in normal flying pitch.
The development mounting plates were then removed and a final version drawn up on the computer in Cambam. Then the CNC router was used to cut final versions out of some 2mm 6061-T6 aluminium sheet.  Nut-plates were riveted into place for the spat mounting screws and the plates mounted in place. They will have to come off again to be painted.
AN822-4D right angle fittings were installed in the top of the brake calipers . Finally, some 1/4" soft aluminium tubing was bent and cut to make the brake pipe. The ends were flared, making sure that the AN nuts and sleeves were in place first. The brake pipe will be taped to the rear of the undercarriage leg and covered by the leg spat. The loop of pipe is to ensure that flexing of the leg will not break it.