22nd November 2008 - Fuselage bottom complete

I started today by final welding the remaining bottom stringer stand-offs. Then all the stringer supports were drilled with a 1/8" drill. The stringers were positioned and cut to length before being match drilled to the supports. As can be seen in the picture these form a nice smooth curve ready to take the fabric. Next the firewall was replaced on the engine mount bolts and the lower part of the firewall was match drilled to it's mounting tabs. A sheet of 0.025" thick 6061-T6 aluminium was then match drilled to the bottom lip of the firewall. The positions of the bends to fit the shape of the stringer support bridge were marked and the sheet bent as can be seen in the picture. The position of the side bends were then also marked and the sheet bent up on each side and cut off just above the lower side mounting tabs. The sides were then match drilled to these tabs. The aluminium side cheeks will overlap the bottom sheet and attach to the same tabs providing a waterproof joint.

21st November 2008 - Bottom Stringer mounts

The extra piece of stainless steel channel I needed arrived this morning so I fabricated the support for the front end of the bottom stringers. These sit off the bottom of the fuselage by 1-5/8" to provide clearance for the control column torque tube. The mounts at station 48 are also fabricated to make the bottom of the stringer 1-5/8" below the bottom of the main fuselage structure. The rearmost mounts sits flush to the rear cross member. Then the remaining mounts for the stringers were cut to follow the natural curve of the stringer and welded or brazed, as appropriate, to the fuselage cross members and diagonals. There are about 5 of the stand-offs still to final weld tomorrow then the mounts can be match-drilled to the underside of the stringers ready to be pop-riveted into place before covering. You can see in the bottom picture a hole drilled through each mount into the stand-off. This is needed to allow the air to escape when welding otherwise as the tube heats the air inside expands and pops through the weld pool making it impossible to get a clean joint.Based on the plans, I don't think it is strictly necessary to put mounts on the diagonals but putting them there will help to provide support for the stringers which in turn support the fabric and further increase the stiffness of the fuselage.

19th November 2008 - Tank filler and stringer preparations

I started today by fitting the combing temporarily. Then using the filler cap template made previously to guide a holesaw I cut through the combing at an angle where the filler neck of the tank should fit. The tank was then installed to check the fit and the filler neck marked for final length. Once the neck was cut to size the tank was replaced and using the template as a surrogate for the window it was possible to check that the filler cap will sit nicely flush on the windscreen. The hole through the combing will be lined with some plastic edging to protect the silicon rubber connecting tube. With this job complete the tank can now be safe stored until the painting starts.

In order to give the brain a rest I then decided to make a start on the preparations for fitting the remaining stringers to the fuselage. First 20 or so 1-1/2" sections of 5/8" * 0.035" tubing were cut in half to make 40 stringer support mounts. Four of these were welded to short lengths of tubing which will act as stand-offs for the stringers under the fuselage to clear the control column torque tube. Eight 1-1/2" lengths of 3/8" * 0.035" tubing were also cut to act as the front supports for the stringers. Two of these were welded each side to the back of the rear door posts and two either side of centre of the top cross member at the rear of the cabin - just visible in the last photo. The remaining two will weld to the lower stringer support cross member at station 18" just behind the firewall on the bottom of the fuselage but I need to get some more stainless steel channel to make this.

14th November 2008 - Tabs and more tabs

It has been a slow week this week as I've got involved in another aircraft project that is taking time; see http://www.e-go.me/ for details. However, today I got down to installing the tabs that will support the firewall and the front fuselage cheeks. 43 tabs in all, so that's 239 so far on the fuselage. The front uprights of the fuselage cheeks don't need tabs as they will rivet to the sides of the firewall, a job for late in the build. I also brazed into place the two straps that will fasten round the top of the fuel tank - just visible in the second picture. Final job for the day was to install the capacitive fuel level sender into the fuel tank. Next job is to cut out the combing for the fuel filler tube and test fit the tank - then the tank can be stored out of the way until later.
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7th November 2008 - Firewall

The weather was finally good enough today to open the workshop doors and get access to the front of the fuselage so it was an opportunity to fabricate the firewall. First a piece of particle board was match drilled to the engine mount. Then the outline of the fuselage was carefully marked on the board which was cut out to act as a form block for the firewall. The firewall is a sheet of 0.018" stainless steel. It was match drilled to the form block and then the edges hammered down to form the lip which will be riveted to the fuselage sides and bottom and carry the mount for the cowl. At the top a strip of stainless steel will blend the gap between the windscreen and cowl. I'll need to weld about 16 tabs to the front of the fuselage to secure the firewall and may rivet some stiffening aluminium angle to the rear to carry the weight of the battery and other firewall mounted items. But those are jobs for another day - it is raining again!

5th November 2008 - Installed fuel tank

I went to collect the welded fuel tank today so it was time to install it and hope that it still fitted! The tank was initially supported using tie down straps whilst the stainless steel supports were pulled tight under the tank and match drilled to the rear supporting tabs to take 1/4" bolts. Then the tank was filled with water to "soak" test it and weight it down into the supports. The pictures show the four 1" diameter tubes installed through the tank which will be used to route the throttle, mixture and other controls and cables from the cockpit through the firewall. This thing is heavy when full so I think that I will install a pair of demountable angles bolted to plates welded onto the forward fuelage side diagonals to support the bottom outside edges of the tank just in case! Once the tank was installed and filled a 68mm hole was drilled in a piece of scrap aluminium. This was positioned symmetrically around the tank filler spout which had been deliberately left long. Then using a home made strap duplicator, the plate was match drilled onto the windscreen support tabs. The plate can then be clecoed onto the windscreen through the matching holes to provide the position for the cut out for the tank filler plate and tank cap

3rd November 2008 - Tank straps and the first stringer

Having understood the positioning of the tank, the lower supporting straps were bent into shape - these are fabricated from 1" wide stainless steel strip 0.035" thick. The front of the straps were brazed onto the firewall top cross-member. Tabs 195 and 196 were then welded onto the rear tank support cross member in line with the direction the straps should take across the tank. The rear ends of the straps were folded over and brazed to double the thickness. With the tank in place these will then be match drilled onto the tabs to position the tank exactly. Straps will then be fabricated across the top of the tank. The picture shows the two tank end formers held in place by the straps with the stainless steel covered by rubber strip to protect the tank from damage. Next job was to make a start on the fuselage stringers. These are 1/2" diameter aluminium tubing that will support the fabric. They are secured to the fuselage cross members by brazing semi-circular sections of 5/8" * 0.035" steel tubing to the cross members where the stringers cross. At the front a piece of 3/8" tubing is brazed to the back of the channel at the back of the windscreen and the stringer slots over this. At each junction the stringer was match drilled to the support from underneath and clecoed into position. Eventually, once everything is painted, they will be pop-riveted into place before covering. There are 9 of these stringers to install, including two at the bottom of the fuselage that mount on stand-offs to keep the fabric clear of the control torque rod and elevator and flap push rods. Oh well, that's one done!

2nd November 2008 - Back Underway

Finally I got the chance to get back into the workshop for a few minutes. First job was to refit the aluminium section that closes the gap between the combing and the firewall round the recently installed windscreen central support and the windscreen tabs. Jobs like this take significant amounts of time but don't seem to move the project forward much. Tuesday I should be collecting the fuel tank from the aluminium welder so next job was to prepare for the installation of the straps that will support the tank. The tank end blank was secured into position to provide the positioning.