Started Mounting Cabin Frame

I started today by fitting the attach angles to the bottom of the cabin frame.  These two angles are clamped to the outer edges of the channels and then drilled to each other.  After these were drilled, I countersunk the bottom face and riveted them together.

To ensure that the angles were mounted in the right position, I clamped some scrap angle to the longerons with some pieces of hinge material underneath to tip the angle back to match the slope of the side skin.

Here you can see that the angle is flush with the skin.

I then used some scrap 0.063″ aluminum (the thickness of the cabin frame channels) to space the attach angles back so that the forward edge of the cabin frame will be flush with the side skin.

I then drilled/reamed the attach angles to the rest of the structure.

I then temporarily installed the cabin frame to see how it fit.  As I measured yesterday, it was slightly narrow, but a small amount of pressure from a clamp could spread it into position.  The attach angles hang over the sides of the longerons.  I marked the overhang and then removed the attach angles to start filing them down.

I took a break from the filing and laid out a cover for the cabin frame channel.  I’m going to be installing a cover on this channel so that I can install a cabin light into it.

Finished Cabin Frame

I finished deburring and countersinking the cabin frame components this morning.  When our two year old went down for her nap, I came back out and primed all of the components and then started assembly.

I’ve seen several builders complain that their cabin frames came out wider or narrower than intended.  I think this is likely due to the slight amount of play in the splice plate rivet holes.  Although the play is tiny at the splice plate (in the middle joining the left and right halves of each channel), the amount of play at the ends of the channel will be much more (easily 1/4″ or more).  To help ensure that this doesn’t happen to me, I clamped the channels back in the sizing jig before squeezing the splice plate rivets.

After the front and back channels are joined with the splice plates, the straps can be clecoed into the forward channel so that solid rivets can be squeezed here.  After all solid rivets are squeezed, the aft channel can be installed and blind rivets can be squeezed.

I didn’t get any more in process pictures, but here’s the completed cabin frame.

Here you can see the solid rivets in the forward channel (lower) and blind rivets in the aft channel (upper).  After everything was riveted, I measure the channel and I was only 1/32″ narrower than the plans called for.  This appears to be more accurate than most people end up with.

Installed Master Cylinder Fittings

I received the AN822-3D fittings from Aircraft Spruce today and installed them in the master cylinders.  I then installed the hoses from the brake fluid reservoirs onto the upper fittings.  I searched everywhere for these fittings in black, but could only find them in blue.  I did find AN822-4D fittings in black, but I didn’t want to use 1/4″ lines here if I could avoid it.  I even briefly thought about having some re-anodized in black, but that would be ludicrously expensive and I couldn’t have re-anodized the hose end fittings.  I also replaced the AN816-4D fittings I previously installed in the parking brake with AN816-3D fittings.  Finally, I measured for the final brake hoses from the master cylinders to the parking brake.  I need to put in another order to Bonaco soon for these hoses as well as the manifold pressure hose and possibly the remaining fuel hoses.

Torqued Engine Attach Bolts

I’ve been deburring and countersinking pieces of the cabin frame, but this is boring and not worth pictures.  I did decide I’d go ahead and torque and cotter pin the engine attach bolts for some reason today.  You can’t get a torque wrench on these, but Van’s instructions are basically to tighten these down firmly against the internal spacer in the mount.  You can feel when these bottom out against the spacer.  I then tightened them slightly more to align the cotter pin slots.  Getting the cotter pins installed in the top two bolts was fairly trivial.  The bottom two were kind of a pain with everything in the way.  Do yourself a favor and install the cotter pins as soon as you hang the engine and not after the exhaust, control brackets, wires, etc. are in the way.

Started Countersinking Cabin Frame

I disassembled and deburred all of the channel holes in the cabin frame.  I then started working on countersinking all of the necessary holes.  These are the ones in the channels that are used to rivet on the splice plates.

I also did all of the outer holes along the forward channels.  These are a little trickier since the curve prevents using the countersink cage to set the depth.  Basically, these all need to be done freehand which makes these holes fairly time consuming.

Finished Drilling Cabin Frame

I fit the forward channels and filed the ends to ensure the center seam was tight.

I then transferred the lower hole locations to the upper channels.

I then fabricated some spacers out of scrap 2x2s that were sanded down to 1.375″ thick.  Since I’m fabricating the cabin frame flat on my bench, I used some scrap 1x2s and long screws to clamp the cabin frame down tight to the bench.

Here’s a closeup showing how the scrap wood is screwed directly to the bench.  These are positioned directly over the internal spacers.  This keeps the cabin frame thickness exactly 1.5″.

Finally, the top channel was drilled.

I then positioned the forward splice place and match drilled the channels to it.  This will eventually be installed on the inside of the channel.

Now that everything was positioned and drilled, I went back through and enlarged all holes to #30.

While I was doing that, Andre stopped by and fabricated a number of the attach angles.  These are used to attach the cabin frame to the fuselage.

Finished Drilling Aft Cabin Frame Channel

My buddy Andre came over today to help me rivet the aft top skin.  I got the honors of crawling into the tailcone to buck these rivets.  I’m a pretty big guy (6’4″ and 235 lbs), so this was a pretty tight fit and I was pretty uncomfortable by the end.  After knocking out all of the riveting, I also torqued and sealed the shoulder harness attach strap bolts.  I didn’t want to have to climb back in here again if I could help it.

Here’s the finished product. The forward row of holes (where the clecos are still present) is left open since the forward skin also attaches here.

Later in the evening after everyone else had gone to bed, I drilled the outer cabin frame joint strip drilled to the aft channel.  I need to make some spacers to temporarily fit between the forward and aft channels to ensure proper spacing.

Started Drilling Cabin Frame

I didn’t have much time to work on the plane today, but I did manage to get the inner cabin frame joint strip drilled to the aft channel.  I’m only drilling these out to #40 now, but they’ll get drilled out to #30 once everything is fit.

Installed Hoses from Bonaco

Sorry there were no updates for awhile.  I flew the family down to Carlsbad, CA to take the kids to Legoland.  It’s a fairly quick 3 hour flight from NorCal, and included a night IFR arrival, so that was fun.  We got back yesterday, but I was dead tired so I didn’t work on the plane.  My order from Bonaco did arrive while we were gone though, so I got started tonight by fitting the hoses.  Here is the right brake line.  I used strips of silicone tape (which only sticks to itself) to attach it to the gear leg.  I also used a tiny strip where the line crosses the joint between the gear leg and the engine mount to prevent wear on the line.

The line then runs straight across the fuselage and is attached to the two center engine mount tubes using some adel clamps.  I fit the cabin heat muff temporarily to ensure that the output tube wouldn’t interfere with the right brake line.

Here is where both left and right brake lines attach to the firewall penetrations.

Here’s the left brake line for comparison.  Notice that the line doesn’t need a big loop near the bottom for strain relief as the plans specify since we’re using flexible line.  There’s only enough slack at the bottom to allow the brake caliper to slide off the pins.

I also installed the 3/8″ fire-sleeved fuel line from the firewall penetration to the mechanical fuel pump.  This looks like the line bends rather sharply upward, but in reality it bends away from the camera before turning upward, so the curve is rather gentle.  Torquing these fittings was a pain given how much stuff is in the way.

Here’s a better view of the cabin heat muff.  You can see that it captures two pipes for better heat transfer.

I also installed the tee fitting into the brake fluid reservoir and then installed the brake lines.

Here is approximately where these lines will be routed.  These are 3/16″ stainless steel braided teflon lines with a black sheath over them to match the other all black brake components.  I have some AN822-3D fittings on order that will be used to attach these lines to the master cylinders.