30th March 2009 - Stringers complete

Today I welded into place the front steel sections of the right fuselage side stringers and then brazed the supports for the aluminium rear sections to the fuselage cross members. The process I used for positioning all the supports was to clamp a length of steel 5/8" tubing acting as a dummy stringer to the fuselage and then position the mounts which are semicircular sections of the same tubing between the cross members and the dummy stringer. Because, as it's the same diameter, the dummy stringer won't sit down into the mounts it is then possible to apply flux and then braze the mount to the cross member without having to get the dummy stringer too hot or accidentally brazing it into place as well. The 2nd picture shows the way the braze metal wicks into the space creating a neat and strong joint. The mount is offset from the cross member to allow space to pop-rivet the aluminium stringer to it from the inside.

29th March 2009 - An Engine!

The big decision is made irrevocably - I've bought an engine. The engine was built in 1970 and is a Lycoming O-235-C2C originally out of a Grumman AA1 Yankee. Subsequently, it was installed in a pusher configuration Rutan Long-ez, hence the forwards facing exhaust pipes. Unfortunately both of these aircraft were written off - in neither case was the engine the problem, but hopefully it's third time lucky. The engine is first run and total time is only 820hours since new. I need to establish whether in the Long-ez accident the engine suffered a prop strike and needs a shock load inspection. In any event, the runout on the flange is not measurable and the prop was wood so hopefully there won't be any internal damage although the price paid allows for repair if necessary. The engine is rated at 115hp for upto five minutes and 108hp continuously. The C2C version of the O-235 is an interesting engine. It has the same cylinders and crankcase as the original O-235-C used in aircraft such as the Piper Colt, but has the same crankshaft as the current O-235-L2C and N2C. The crankcase has a conical engine mount which makes the engine mount easy to fabricate and uses much cheaper mount rubbers than the dynafocal mount engines. Now that I've got an engine I can order the tubing to fabricate the engine mount.

28th March 2009 - Fabric support tabs

Winter seems to have returned to the UK and it was too cold and wet to get the fuselage out of the workshop to make room for some of the aluminium forming needed so I did some of the little outstanding jobs on the control surfaces. First task was to close the ends of the rudder front spar. For some reason I'd left the 3/4" tubing that it used for the leading edge of the rudder open at both ends. This seems like it would encourage internal corrosion so I cut out two small disks of 4130 sheet and welded them into the ends of the tube to seal it. Next job was to fabricate and install two small plates either side of the spar and surrounding the hinge on the rudder. These will provide a flat surface for the fabric to adhere to around the hinge. These were made from 0.032" thick 4130 steel sheet. Finally today another 8 of these plates were fabricated and installed to repeat the process for the two elevators. These little jobs don't seem to show much progress but take time. Anyway, the tail surfaces are now completely finished so sometime soon I'll take them to a local specialist airframe sandblasting company to get them cleaned up ready for priming and covering. So that's another four items off the to-do list. I'm updating the list by colouring the completed items green to show progress. No additional items today which is good news!

26th March 2009 - Left rear window mount and left side stringers

That's four items off the list and one more well underway. First job today was to weld into place lengths of 1/2" * 0.035 tubing to form the front sections of the two left-side fuselage stringers. The top stringer could all have been aluminium but by using a length of steel tubing it was then possible to weld the support tabs for the bottom of the rear window frame directly onto it. The bottom section is only short but was needed to create a smooth joint into the fuselage side diagonal which is too close to the rear door post to allow the stringer to pass over it as is the case with all the other fuselage members. Two short stubs of 3/8" tubing were then welded into place, one on the back of the diagonal, and one into the 1/2" steel tube. These are used as the front mounts for the two lengths of aluminium tubing that are used for the rest of the stringers. Next tabs 248-262 were welded onto the fuselage members that surround the rear window to support the window frame. The first picture shows three stand-off tabs jigged into position on the diagonal. These are needed to create a smooth line for the frame from the upper longeron to the stringer. The second picture shows the last of the tabs after welding still held in the jig used to position it flush with the longeron. Final job today was to braze into place the supports for the rear sections of the stringers and to match drill the stringers onto the supports. As with all of the stringers, these will be pop riveted onto the mounts from the inside to keep a smooth line where the fabric lies over them.

25th March 2009 - The List!

My major objective over the next few weeks is to get the fuselage finished to the stage of being ready for priming prior to covering. This means getting all the fixings that will be needed welded or brazed into place so that the painting doesn't have to be re-done as bits are added. To this end I've prepared a "to-do" list of the jobs to be completed. Some of them are quick and easy, others will take significantly more time to complete (poor project management practice I know) but getting everything down in a list should help in avoiding missing too much. So steps needed as of today (I'm sure more will be added) are:

1. Weld in place left forward sections of fuselage side stringers (1/2” * 0.035” 4130 tube)
2. Weld in place left mount tubes for rear sections of fuselage stringers
3. Braze in place left stringer supports
4. Match drill left stringers to supports
5. Weld in place right forward sections of fuselage side stringers (1/2” * 0.035” 4130 tube)
6. Weld in place right mount tubes for rear sections of fuselage stringers
7. Braze in place right stringer supports
8. Match drill right stringers to supports
9. Fabricate right window mounting angles
10. Fabricate right front window
11. Fabricate right fuselage cheek panel
12. Fabricate left seat outer filler panel and install mount tabs
13. Fabricate right seat outer filler panel and install mount tabs
14. Fabricate left rear window surround and install mount tabs
15. Fabricate right rear window surround and install mount tabs
16. Fabricate left rear window
17. Fabricate right rear window
18. Order tubing to fabricate engine mount
19. Fabricate engine mount
20. Fabricate left above door panel and install mount tabs
21. Fabricate right above door panel and install mount tabs
22. Fabricate left window to main screen angle
23. Fabricate right window to main screen angle
24. Fabricate left above-door panel to main screen angle
25. Fabricate right above-door panel to main screen angle
26. Fabricate and install left strut fuselage mount
27. Fabricate and install right strut fuselage mount
28. Cut antenna mount panel to final size
29. Install baggage compartment mount tabs
30. Purchase baggage compartment panelling
31. Fabricate baggage compartment angles
32. Fabricate baggage compartment walls and floor
33. Fabricate and install rudder hinge fabric support plates
34. Fabricate and install left elevator hinge fabric support plates
35. Fabricate and install right elevator hinge fabric support plates
36. Fabricate windscreen to firewall seal angle
37. Fabricate left door panelling
38. Install left door window support tabs
39. Fabricate left door window
40. Fabricate right door panelling
41. Install right door window support tabs
42. Fabricate right door window
43. Install cable support tabs - panel to autopilot servo
44. Install cable support tabs - panel to strobe pack
45. Install cable support tabs - strobe pack to left wing root
46. Install cable support tabs - strobe pack to right wing root
47. Install cable support tabs - panel to antenna
48. Install cable support tabs – panel to control column
49. Install cable support tabs - panel to front underside panel for transponder antenna
50. Install cable support tabs - strobe pack to rear of vertical stabiliser
51. Fabricate and install mounts for flexible brake pipe terminations
52. Fabricate and install rear battery mount (option for forward CofG)
53. Fabricate and install firewall battery mount (option for rearward CofG)
54. Install cable support tabs – firewall forward to rear battery mount
55. Fabricate and install leg intersection fairing mount tabs
56. Fabricate co-pilot control column extension
57. Fabricate and install VOR antenna mount in vertical stabiliser
58. Close rudder front spar tubing top and bottom
59. Install pitot tubing support mounts
60. Install static tubing support mounts
61. Install static port plates
62. Fabricate and install rear left seat belt mounts
63. Fabricate and install front left seat belt mounts
64. Fabricate and install rear right seat belt mounts
65. Fabricate and install front right seat belt mounts
66. Redo left front window
67. Fabricate left internal above door panel
68. Fabricate right internal above door panel
69. Rework undercarriage mount to level fuselage
70. Fabricate and install rear spar carry through cover
71. Fabricate left rear window sill and fuselage diagonal cover
72. Fabricate right rear window sill and fuselage diagonal cover
73. Redo between seat fill panel and tabs
74. Space door latches off door frames by an additional 1/8"
75. Redo upper fuel tank straps
76. Check all tabs are drilled to final size and install all missing nutplates
77. Install mounts for tank breather line
78. Install mount for transponder antenna
79. Install support for firewall mounted gascolator
80. Install support for firewall mounted tranducer manifold
81. Install support for firewall mounted master and starter relays
82. Install support for firewall mounted brake reservoir
83. Install support for firewall mounted cabin heat valve
84. Install support for firewall mounted electric fuel pump
85. Fabricate shoulder seat belt attach cables
86. Cut out side panels and flap lever cover to clear seat belts
87. Fabricate and install shoulder seat belt attach cable support through baggage compartment rear bulkhead
88. Drill firewall for throttle control
89. Drill firewall for mixture control
90. Drill firewall for carb heat control
91. Drill firewall for power cabling
92. Drill firewall for sensor and transducer cabling
93. Drill firewall for cabin heat control
94. Drill firewall for primer pipes
95. Install support for firewall mounted vacuum regulator
96. Install support for firewall mounted fusible link mounting

And that's all there is to it!

Update 27th March 2009, added 59,60,61 completed 1,2,3,4

Update 28th March 2009, completed 33,34,35,58

Update 30th March, completed 5,6,7,8, added 62,63,64,65

Update 31st March, completed 10, 22, 23

Update 1st April, completed 24,36

Update 3rd April, completed 9,11,20,21,25,28

Update 11th April, completed 18

Update 13th April, completed 37

Update 14th April, completed 14,16,39, added 66, N/A 38,41,57

Update 18th April, completed 61

Update 20th April, completed 69, added 67, 68, 69

Update 21st April, completed 15, 17

Update 23rd April, completed 19

Update 24th April, completed 62,63,64,65

Update 28th April, completed 12, added 70

Update 7th May, completed 67

Update 10th May, completed 29, 31, 70, 71, added 71, 72

Update 11th May, completed 13, 68, 72, added 73

Update 12th May, completed 40, 42, 66, added 74

Update 14th May, completed 26, 27, added 75, 76

Update 15th May, added 77

Update 16th May, completed 51,75

Update 17th May, completed 43, 44, 45, 46, 47, 48, 49, 50, 59, 60, N/A 52, 54, deferred 30, 32

Update 18th May, completed 77, 78, added 78

Update 25th May, completed 73, 85, added 79-94

Update 30th May, completed 74, 76, 86, 87

Update 16th July, completed 32, added 95, 96

Update 21st July, completed 82, 83, 88, 89, 90, 91, 92, 94, N/A 55, 93

Update 22nd July, completed 53, 80, 81, 96

Update 24th July, completed 79, 84, 95, deferred 56

21st March - Left cheek and window

First lttle job to check off the list today was to drill the panel behind the windscreen to take the GPS and Comm antenna. Strictly these are too close together but hopefully with a notch filter on the GPS input it should be OK. Also, the ground plane for the comm antenna is not really big enough but with rag and tube fuselages this is always a problem. I'll test the standing wave ratio (SWR) once everything is installed to check it's OK, otherwise it may be necessary to glue some aluminium foil to the inside of the fabric to extend the ground plane. Next job was to trim the main windscreen back to the outer screen supports. This was done with a cut-off wheel in the angle grinder, then reducing grades of abrasive were used to get smooth edges. Next a piece of 2mm lexan was cut to make the side window and drilled to the tabs underneath the top stub longeron. The window was also then drilled to the window-frame pieces made earlier http://tailwindbuild.blogspot.com/2008/10/19th-october-2008-left-side-window.html. Finally a piece of 0.025" thick aluminium sheet was cut to overlap the bottom of the windscreen and match drilled to the windscreen support tabs, the door frame support tabs, the lower longeron support tabs and the firewall edge. The rear edge of the sheet was bent to a right angle to wrap neatly round the back of the door frame and slots cut out for the door hinges. Eventually the front of the cheek will be riveted to the firewall and the bottom riveted to the under side panel http://tailwindbuild.blogspot.com/2008/11/22nd-november-2008-fuselage-bottom.html

15th March 2009 - Fuselage top complete

First job today was to match drill aluminium angle supports to the steel plates to support the bottom of the fuel tank. First the fuel tank was installed and 2/3rds filled with water to weight it into position. Then the angles were clamped to the mounting plates and drilled for 3/16ths bolts. The angles will have rubber strips glued to them to cushion the tank edges and are only designed to really support the tank if the main straps gave way.
Next job was to braze the supports for the left and right top fuselage stringers. The middle ones having been installed previously - http://tailwindbuild.blogspot.com/2008/11/3rd-november-2008-tank-straps.html
Note the offset of the bottom of the rudder to the left of the aircraft compared to the centre stringer to counteract engine torque. In hindsight, for esthetic reasons, I should probably have also offset the central stringer but I don't suppose this is a view which will often be seen in the finished aircraft. Then the panel that closes the gap between the rear of the windscreen and the fabric of the fuselage top was match drilled to it's support tabs. Finally the windscreen was drilled for the tank filler cap using a holesaw through the jig made earlier http://tailwindbuild.blogspot.com/2008/11/5th-november-2008-installed-fuel-tank.html This was done in a slow turning hand drill and then the hole sanded smooth to ensure that there are no stress risers that can propogate cracks.
This means that the top surface of the aircraft from the firewall back is now structurally complete and ready for painting and covering. Next on to the sides.

14th March 2009 - Rudder cable lead-outs, engine decision

Another three smaller jobs today. First was to create a pair of rudder lead outs. These will allow the rudder cables to exit the fuselage but still ensure that the fabric covering can attach securely around the exit holes. Two lengths of 5/16" * 0.028" steel tubing were bent into shallow "S" curves. Then two steel plates were cut out from 0.040 steel sheet. The sheets were slotted to allow the tubes to pass through at a shallow angle and the tubes brazed into place. Then the plates were positioned on the rear fuselage side uprights in line with the run of the rudder cable and brazed into place. The 5/16" tubing is a perfect fit for flexible plastic brake pipe which will protect the rudder cables through the steel tubing. Note, I'm not going to use electrical earth cable for the rudder but it was convenient to use to line up the plates:-) Once the fuselage is covered, shaped plastic fairings will cover the external section of the lead-outs to create a neat finish. I still need to clean off the flux from brazing hence the scruffy appearance.
Next job was to position and weld into place tabs 244 -247 which provide the mount for the strobe power pack. There will be strobe lights in both wingtips and possibly the tail (if the dollar exchange rate improves!). The power pack only weighs 1lb so won't impact weight and balance much. I positioned it just behind station 78 to keep any interference away from the radios and antenna. The rudder cable will pass over the top of the strobe pack, but I added an additional cable guide, to the left of the picture, to make sure it can't possible touch.
Final job today was to weld two plates to the fuselage diagonals just behind the firewall. These will be drilled to mount two sections of aluminium angle which will support the ends of the fuel tank. This isn't in the plans but it seemed to me that the stainless steel bands that support the tank might one day crack or the braze give way and a loose fuel tank could really spoil your day so a little belt and braces wouldn't be a bad thing.
The big decision of the last week is that I'm definitely going to go with a Lycoming O-235 engine. These are available mid-time at a sensible price, are rock-solid reliable, weigh the right amount to make the weight and balance work and as I've already installed a Lycoming in my Vans RV9A - I know what I'm doing with this make of engine. The various versions of the O-235 range from about 108 to 118hp which should give about a 150mph cruise in a Tailwind. I still can't build the engine mount until I find a specific engine as there are two types versions - straight mount, or dynafocal. The other engine considered include:
Continental O-200: 100hp, less available and overall more expensive: purchase cost, rebuild cost, TBO.
Continental O-300: 145hp, very heavy, mods to wing spars needed to meet LAA requirements, 6 cylinder so very expensive rebuild cost, reliability not as good as Lycoming
Jabiru 3300: 120hp, very light so may cause W+B problems, expensive as no significant second hand market, power developed at 3300rpm so difficult to prop to get maximum effect.
Rotax 912/914: 100-115hp, very light so may cause W+B problems, expensive as no significant second hand market, engine runs at high revs so uses a gearbox. Complex install, both air and water cooled.
Lycoming O-320: 150-160hp, mods to wing spars needed to meet LAA requirements, good value but inconsistent with my objective of building a light responsive Tailwind rather than one for out-and-out cruise performance

13th March 2009 - Autopilot servo

I was out of the country last week so no progress but I've got no excuses for the next few weeks. While I was away I started making a list of the tasks to complete the fuselage structure but when it got over 50 I gave up and decided it was more effective to just get on with building so today I did just that. First, I final welded the rear spar attach brackets. I've been puzzling whether to do these now as the plans suggest leaving them until the wings are attached in order to set the wing incidence. However, most people build the wings before the fuselage so need to do the adjustment at the attach brackets. I've decided to match the wings to the fuselage rather than the other way round. Once I'm ready to build the wings I'll level the fuselage precisely set out the spars supported as though built into the wing structure and then match drill the wing spars to the fuselage. I can use a laser level to set the spars before drilling. In this way I can both make sure the wing incidence is perfect and also make sure the flap torque tubes clear the upper longerons before the wings are built - that's the theory anyway! It was also easier doing this fairly tricky welding before the area gets any more cluttered.
Second job was to create the mount for the wing leveller autopilot servo. I'm using a Trio Ez Pilot, same as in my RV9A. This unit is fairly competitively priced and works superbly. What does an aircraft with no engine, propellor, wings, or covering need? an autopilot obviously. Actually it is convenient to do all these sorts of jobs while the internal structure is fully accessible. First a attach bracket fabricated from 0.071" 4130 plate was cut out, drilled, and welded to the aileron control horn. The three holes drilled in this will allow the sensitivity of the autopilot to be tuned. Tabs 240-243 were then welded to the rear of the lower cross member under the back of the seats and to the diagonal just behind this. Two pieces of 3/4" * 3/4" * 1/8" aluminium angle were then cut to sit on top of the cross member and diagonal and match drilled to the tabs. Next the autopilot servo was positioned to allow a straight linkage from the servo horn to the aileron horn and match drilled to the support angles. Finally the servo pushrod was fabricated from 1/2" aluminium tube as per the instructions for the autopilot. Note the large washers under the bolt heads that connect the ends. These ensure that even if the Heim joints fail, the pushrod will be retained on the bolts. The Trio instructions call for a control throw of 1.5-2.4". I've got 2" so that should work well.