March 30th 2008 - More Welding

No pics/text for the next few days as I slowly final weld the fuselage

March 29th 2008

Made a small start on the welding with the tail spring support cross member

March 27th 2008 - Finished tack welding main fuselage structure

Finished the installation of the cabin overhead structure which means the main fuselage structure is now complete pending final welding. Then tidied the workshop as a week of cutting and grinding tube had left a black powder over everything. The fuselage seems very strong even with the joints only tacked.

March 27th 2008 - Internal fuselage structures

Got a lot completed today, all the internal structures supporting the seats and the controls are installed and tack welded, also the windscreen diagonals are installed and tacked and I'm about halfway through installing the support structure overhead the main cabin. Once this is finished then the fuselage main structure is ready for final welding. Based on the experience with the fuselage sides, I estimate it will take about 24-36 hours of solid work to complete the welding and a lot of Argon! I hadn't appreciated before starting the build that Argon is going to be a significant cost (c£500) whereas it looks like I'll only use about 3kg of filler rod (£25).

March 26th 2008 - More diagonals and internal cross members

Finished installing and tack welding the lower diagonals and completed the upper ones up to station 78. Installed two internal cross members. Another interesting cluster to weld (station 78 lower port side). The rudder bar join is touching the lower port diagonal from station 0 to 18. I'll need to work out how to solve this. Once the windscreen diagonals and the structure over the passenger cell are complete I will release the fuselage from the building board to complete the rest of the internal structure. It looks like it makes sense to finesse the length of the internal tie bars to get the door opening into a shape that will make it easier to construct the door and get a good fit.

March 25th 2008 - Diagonals to station 78

Cut, installed and tack welded the nine diagonals from the rear of the fuselage to station 78 - three top, three bottom and three internal. I can't really use the notcher any more as the joints are altered in shape by the existing welds so its cut and then file/grind to get a good fit. The detail picture shows the cluster at station 144 with 7 tubes meeting the longeron - should be fun final welding!

March 24th 2008 - Fuselage cross members

Installed and tack welded all the fuselage cross members today, in each case the lower member was inserted first and then the fuselage jigged to make sure the centre-line of the cross member was in exact alignment with the centre-line on the building board. The lower member was then very lightly tacked and the top member inserted and using a plumb line the fuselage was re-jigged to make sure the centres of the two cross members were vertically aligned and over the building board centre-line. Then the top member was welded to about 1/3rd of its circumference after which the bottom member was also part welded. Station 144 was done first as it sets the datum for the horizontal stabiliser, has most flexibility and also as I've been nervous that the tacks at the end of the longeron might let go and the fuselage sides spring apart. Next the top and bottom firewall cross members were inserted in the same way and a diagonal brace tacked in place to ensure they stay square. The remaining cross members were then installed in order from front to back. The rear spar carry through was fabricated and installed but not welded as this allows the wing incidence to be set. The welding is quite tricky as the current needed for the 0.028" wall tubing (20 amps) will not create a weld pool in the pre-existing clusters. The technique that seemed to work was to lay a bead along the end of the thin tubing using 20 amps then turn the current up to between 25 and 35 amps depending on the cluster to form the fillet weld. An advantage of TIG welding is that I can construct the fuselage with the lower longerons between stations 0 and 48 screwed down to the building board and part weld all the joints without setting fire to anything. This means that I'm very confident that the fuselage is perfectly symmetrical now and should mean that there is very little chance of anything going out of square when I do the final welding.

Easter Sunday

Spent today getting this blog up-to-date. No work on the aircraft but next steps are to tack in the remaining fuselage cross members and all the diagonals.
Design decisions so far are fairly limited but those identified/decided so far are as follows:

Made
Welding- all TIG, A31 rod
Longerons 3/4" OD 0.028" tubing - as per ACS plans
Doors and rear spar carry through - as per ACS plans (to avoid LAA mod if using Jim Clement plans)
Ailerons/flaps - conventional as per ACS plans
Wings - As ACS plans but with Douglas Fir spars
Front and rear door posts - 5/8" square * 0.035" tubing
Panel - Conventional vacuum gyro instruments: venturi driven
Lights - Nav lights and strobes, no landing lights

To be decided
Fuel tank - weld or rivet and pro-seal
Engine, Jabiru 3300? Lycoming O-320/O-235? Gemini Diesel (http://ppdgemini.com/)?
Wing tips - all wood or as per plans?
Covering material?
etc....

Day 14

Welded in place the rudder pedal mounts. Doing this before the upper and lower firewall cross members were in place allowed the rudder bar to be removed after tacking the mounts in place and the mounts final welded and cleaned internally to ensure free rotation. Once the firewall members are welded in place this will become permanent. Note mount on the toe brakes for the brake cylinders which are a pair of Cleveland 10-30 master cylinders

Day 13

Fuselage sides aligned and then tack welded at rear of longerons. Bottom longerons from 0 to 48 located on bench. Spacers to set top of firewalll and rear spar carry through. Tie bar to get centre of cross members directly over centre line using plumb bob. Lower cross members as 24 and 48 tack welded in place. Front spar carry through tack welded in place. Everything aligned so far! There is some confusion over the datum for the width measurements in both the ACS plans and the originals from Wittman. Measuring longeron tubing centre to centre I'm using 40" for the two spar carry thoughs and 37" for the firewall top cross member and 34" for the firewall lower cross member. The lower cross member at station 48 is 38" and of course the longerons come together at the rear fin spar at station 174 7/8. All other cross members will be filled in following the natural curve of the fuselage sides.

Day 12

Completed lay out of the second fuselage side and tack welded it. Looks just like the first!

Day 11

Starting to lay out the second fuselage side

Day 10 Continued

More clusters and the first side is complete. Still fits in the jig perfectly. The only change is that then curve of the bottom longeron has straightened between the clusters.

Day 10

Continuing to final weld the first side

Day 9 Continued

I would prefer the welding to be a bit tidier but I'm pretty confident that the joints are sound, as I said to my welding instructor when completing some of the less pretty samples - "I can guarantee it won't come apart"

Day 9

Decided to final weld the fuselage sides before assembling the fuselage. There are arguments on both sides, the major one anti is that the sides will distort when welding and become unequal, but one previous builder also commented that the sides will bend more evenly into the final fuselage shape if final welded. This makes sense, also I'm TIG welding and expect to get less distortion than those gas welding. So far so good. The side still fits perfectly into the frame with about half of the joints completed. I was right that the acute angles are dificult. Getting the weld pool to join the sides in the centre has taken repeated cycles
of adding material then turning over until the joint is perfect. I still feel very much a "beginner" welder so will be interested in what the experts think of these clusters. I'm getting an expert to come in and give my work a proper QA before proceeding to far.