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.

20th October 2008 - Windscreen mounts, tabs 161-194

I bought some more Argon this morning, so first job was to complete the weld across the back of the channel that will support the rear of the windscreen. This and the channel on top of the rear spar carry through were then drilled for screws to fasten the aluminium panel which will close the gap between the windscreen and the top fabric. This will sit on a neoprene seal to ensure that the joint is watertight. Next I welded tabs 161 -194 onto the side and front windscreen bows. These were then drilled with an 1/8" drill as was the centre windscreen bow. The windscreen was then positioned into the rear channel and starting from the back was match drilled onto the tabs with a cleco positioned into each hole as it was drilled. The drill used was a special version for drilling acrylic. This has a much steeper angle on the point and does not grab the plastic in the way a normally ground drill can. Finally, the windscreen was clecoed into position front to back. Next job is to trim the edges back to the windscreen bows but this will have to wait for a bit as I'm probably not going to get anything done over the next week or so but normal service should be resumed first week in November.

19th October 2008 - Left side window frame

I started today by jigging and tack welding into place strips of stainless steel behind the channel that supports the back of the windscreen. Then started final welding this into place when my Argon ran out when about a third of the way across so the rest will have to wait for another day. With no welding possible there was no option but to bend some aluminium so I started on the framing for the left side window. This sits on the outside of the fuselage butting against the window bows at the top and the stub longerons at the bottom. First job was to create a section of angle to support the bottom of the window from the inside. This will screw onto the tabs already in place to support the side of the combing. The outside of the window at the bottom will be supported by the aluminium skin that cover the first 18" of the fuselage. Next the two sections of angle that surround the top front door post were fabricated. the rear one is a U section that will screw to the outside of the window; the internal dimension of the U has to be equal to the diameter of the door post (3/4") plus the thickness of the window (2mm). The front one is a "step" shape that forms the support on the inside of the window; in this case the thickness of the step needs to be exactly 3/4". A 2mm spacer was sawn out of wood to mimic the thickness of the windscreen and can be seen clecoed between the two sections. It took two goes to bend the rear section to exactly the correct width but the front one worked first time. The front/back dimension of the box created around the door frame by the two sections is about 1-1/8" to allow room to duct the cables and pitot tube up to the wing root from behind the panel.

18th October 2008 - Windscreen

I started work today by installing the piece of stainless steel channel that forms the top of the fuselage over the rear spar carry through. This has the front edge of the top fabric wrapped round it and a section of spruce inserted into the bottom to anchor the fabric. Then a section of aluminium sheet screws through the section and into the spruce to close the gap to the back of the windscreen. This sheet will also provide a suitable mounting for the GPS aerial. Next the windscreen itself was clamped into position using a piece of wood to keep the rear edge flat. The windscreen is a sheet of 4mm acrylic (perspex). The centre windscreen bow was then shaped to fit against the natural curve of the windscreen. This took quite a few iterations but eventually there was a good fit from front to back. The windscreen was then removed and a suitably sized stand-off fabricated for where the centre bow passes over the front spar carry through. Then the centre bow was welded into place; front, back and to the stand-off. I was unconvi9nced that the aluminium sheet would provide a neat rear edge to the windscreen which wants to bow and the sheet would probably not be strong enough to fully prevent this so I welded a second piece of stainless steel channel on edge to capture the rear of the windscreen, keep it in a straight line and anchor it against the three windscreen bows. This works very well as can be seen in the picture. Next I need to weld 30 or so tabs to the outside windscreen bows and across the top of the firewall. The windscreen will be match drilled to these and then cut to final shape. I've have made work for myself by using the channel at the back of the windscreen as to create a seal to the aluminium top panel I will need to weld a ledge to the back of it across the entire width to create a weather seal rather than just using tabs.

17th October 2008 - Left windscreen bow and wing attach brackets

My TIG welding machine will only do DC welding whereas you need AC for aluminium so yesterday I took the completed fuel tank to the local aluminium welding guru to be finished. Today was another beautiful autumn day so Paul and I took the Vans from Andrewsfield (pictured) to Old Buckenham for lunch. We flew along the east coast before cutting inland and the third picture is of Southwold, one of the most picturesque Suffolk villages. I did get a bit of work done later in the day and welded the left front spar attach bracket and left windscreen bow to the fuselage.

14th October 2008 - Rear spar carry through tie rods, left wing attach brackets

Now that the position of the rear spar carry through has been established fairly accurately the last couple of tubes that form the main fuselage structure could be added. The right one welds between the rear spar carry through and the upper fuselage diagonal just in front of station 78. The left welds back to the top fuselage cross member at the station. Later plates that form the upper seat belt mounts will be welded between the rear of these tubes and the longerons. Next the wing attach brackets for the left side of the fuselage were fabricated. Again it took much longer to make these than seems reasonable but it is critical to get the dimensions exact to fit inside the spar attach brackets.

13th October 2008 - Right side door

As previously noted the left side door had been made too tall and would not have opened under the wing. To get this correct for the right door I made a template of the bottom half of the main wing rib. This was attached to the root rib template referenced via the cord line. A straight edged piece of scrap timber was then clamped to the fuelage stretching horizontally across the door opening to define the position of the top of the door opening. This was set 3/8" lower than the bottom of the main rib template to allow for the door panel to overlap and create a good seal. Then the right door was fabricated in the same way as the left. See http://tailwindbuild.blogspot.com/2008/08/14th-august-2008-left-door.html , http://tailwindbuild.blogspot.com/2008/08/17th-august-2008-seat-bottoms.html , and http://tailwindbuild.blogspot.com/2008/08/18th-august-2008-left-door-latch.html for details. Finally the left hand door was shortened to the same dimensions as the right so it should now open!