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Empennage Fairing Nut Plates – 2 hrs

Tuesday May 1, 2012

Tonight I had some help from my daughter Jennifer. On my list of things to do was to install the nutplates on the aft fuselage for the empennage fairing. So first we drilled all the holes for the nut plate rivets. Then we dimpled the nutplate rivet holes and the holes in the aft top skin and the corresponding fuselage bulkhead. That required the removal of the aft top skin which took a while. Once dimpled, we reclecoed the aft top skin in place. I think this is ready to rivet the aft top skin in place. I just need to review the plans to make sure nothing major needs to be done in the aft fuselage before I do.

I also did final installation of  the outboard screws on the roll bar with accompanying washers and lock nuts. I should not have to remove these again.

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Cabin Frame, Part 12: Done! – 2 hrs

February 5, 2012 Leave a comment

Sunday Feb 5, 2012

Sometimes sleeping on a problem overnight really helps me find a solution. In this case it was how to match drill the interior holes though the F-631C/D channel and the cabin frame. At some point I finally realized that I might be able to access the interior pilot holes through the holes I drilled yesterday on the outboard surfaces. The interior holes don’t line up exactly with the exterior holes but they are close enough to get a smaller pilot drill through. And that is exactly what I did as you can see in the photo below. After the pilot holes were drilled I drilled to full size from the inboard side of the frame. Problem solved! If I built another cabin frame I would still recommend not drilling the inboard pilot holes in the F-631C/D and just locating and drilling those from the inboard side of the frame at this stage. I hope that helps somebody else out there because I doubt that I will be building another RV-7A after this one is done.

I also riveted the F-732F reinforcement plate onto the F-732A channel (see below). The other row of holes will be riveted with the top skin. I did not get a picture but I also riveted the F-732E angles onto the F-732A channel.

For now I am leaving the cabin frame attached to the fuselage. The plans say to to store the parts for later but for now they are safer here than in my limited storage area.

Categories: Cabin Frame, Fuselage

Cabin Frame, Part 11 – 8 hrs

February 4, 2012 Leave a comment

Saturday Feb 4, 2012

This cabin frame has been a bigger job than I expected, but I am getting close to the end now. This morning I drilled out the holes on the top skin to the upper F-732A channel along with the F-732F spacer. These eight holes are #30 while all the other holes around it are #40.

I also match drilled the channel to the F-706 bulkhead through the two tabs on each side.

I could not find directions or dimensions for the four holes that connect the F-732A channel to the F-732D angle on the forward end so I just laid out a pattern by measuring off the full scale drawing. Then I clamped the F-732E angles on each side and match drilled those to the to the channel and the frame.

Then I decided to go ahead and make a cover to close up the bottom surface of the F-732 channel. I’m thinking that the open section looks kinda unfinished so I found some .025 scrap alclad left over from the wing walks and cut it to fit the channel. I laid out a pattern for four holes on each side and clamped the cover to the channel.

I used the drill press to drill the holes to #40 first.

Then I drilled them out to #19 for clearance for a #8 screw.

I didn’t take a picture but next I drilled holes to rivet K1000-08 nut plates to the flanges of the channel. Instead of dimpling the flange I just countersunk the rivet holes since the flange is .040 thick. On the other end of the channel I countersunk the holes in the spacer.

Next up was finishing the holes on the outboard sides of the F-631C/D channels. To hold the frame in place for drilling I put a clamp on the inboard side through the access hole. Then I drilled the aft holes on the outboard side of the F-631C to .187. I used my counter sink cage to countersink the holes for AN3 flat head screws and I used some #10 plain nuts to put those screws in to temporarily hold the channel in alignment with the F-631C/D. Then I clecoed the skin onto the side and drilled the two forward holes with #29 drill through the pre-drilled holes in the skin. I pulled the skin back again and drilled the skins holes out to #19 and countersank them for #8 flathead screws. Then I countersank the two forward holes in the F-631C/D for the #8 flat head screws. Finally I tapped the #29 holes for an 8-32 thread.

The aft screws go under the skin and the forward screws go through the skin from the outside. The outer skin looks like this.

The holes on the inboard side of the frame are another story altogether. These holes are pre-drilled on the F-631D angles on the inside of the frame!It would have made so much more sense to pre-drill these in the frame and then match drill through the angles. If I could do it again I would not pre-drill those holes in the F-631Ds. Some builders can get inside the frame through the access hole with a 90 degree drill but my Tight-Fit 90 degree drill is too large. That’s a no-go. I’m going to have to research my options on those two holes on each side.

The next couple of hours were taken up by cleaning, preping, priming and painting the canopy frame parts. I won’t bore you with all the details. The finished parts are shown in the photo below.

On Tuesday I decided to order the majority of the firewall forward kit before the annual price increases kick in at Vans. I deleted a few key things including the exhaust and the prop governor which I will order later after my engine selection is firm. I was amazed when the kit arrived on Friday. So I spent an hour or so doing inventory of the parts which all fit in one box. Everything was there. Here is the box after I pulled out all the extra paper.

Categories: Cabin Frame, Fuselage

Cabin Frame, Part 10 – 2 hrs

February 3, 2012 Leave a comment

Friday Feb 3, 2012

Before drilling the F-631C/D channels to the F-705 bulkhead I decided to drill through the pilot holes with a #30 drill. That will give me a thicker guide hole which will help keep the drill perpendicular to the surface. I did that on the drill press to make sure the guide hole is true.

Then I put the entire cabin frame arch back on the bulkhead and rechecked the alignment of my outline markings for the F-631C/D channels. I just had to make sure it was repeatable to confirm that I had the correct position marked. With that looking good I removed the arch and clamped the F-631C/D channels in place on the bulkhead. The drilling was the easy part. I started with a #30 drill (seen below) then opened them up to 1/4 inch.

A quick check of the alignment with the arch showed that the position still looks good. That’s a big relief!

Categories: Cabin Frame, Fuselage

Cabin Frame, Part 9 – 2 hrs

February 2, 2012 Leave a comment

Thursday Feb 2, 2012

Tonight I worked on fitting the F-631C/D channels to the fuselage and the cabin frame arch. With the top skin clecoed on I used a scrap piece of angle to help me align the arch to the front edge of the skin as you can see in the photo below.

To get the arch to fit properly you have to cut away a bit of material on the outboard edges of the arch to allow the vertical wall of the F-631C/D to sit flush against the side of the arch. You also have to trim some material off the outboard side of each F-631C/D to make it’s contour follow the side of the fuselage. This was an iterative process. In this photo below you can see the right edge of each channel has been rounded and tapered to the aft edge. I used my disc sander to do this, checking periodically to make sure I did not over trim.

This photo shows the trimmed surfaces better.

If you don’t trim enough on the sides of the arch the whole arch will not sit low enough. I found that I had to trim until the aft edge of the arch sat all the way down on the longeron. After iterative trimming I finally got the arch where I think it should be. Here you can see it clamped in place for a fit.

The next challenge was figuring out how to drill the two 1/4 inch holes through the bottom of the F-631C/D and the top of the F-705 bulkhead. This is critical because it establishes the fore/aft and side to side alignment of the arch. I don’t have a 90 degree angle drill that is small enough to go in through the aft access hole. Unfortunately my Tight-Fit drill is too large. So I decided to  follow the process described by Bruce Swayze and marked the outline of each F-631C/D on the top of the F-705 bulkhead with everything clamped in place and aligned. Then remove the arch and use the outline to place the F-631C/D channels in the right place and drill through the bulkhead. This is dicey because there is the potential for slip and other small alignment errors. In the photo below you can see one channel aligned to the outline mark. It’s too late to drill tonight and I want to sleep on this before pulling the trigger, so come back next time to find out how this turns out.

Categories: Cabin Frame, Fuselage

Cabin Frame, Part 8 – 1.5 hr

January 30, 2012 Leave a comment

Monday Jan 30, 2012

The next stage in the cabin frame construction is to mount it to the fuselage. The primary attachment is through two pairs of angles, F631C and F-631D that mount to the F-705 bulkhead. One of the angles mounts inside the frame and one mounts outside on each side. So the plans say to clamp the angles to the frame and drill two holes through the base for “keeper” rivets. This process is primarily to get the spacing correct between the uprights but there is also an element of fore-aft offset and twist that comes into play. I messed around with the alignment for close to an hour before finally getting satisfied. One thing I noticed on the drawing is the outboard (larger) angle sits slightly further aft than the inboard (smaller) angle. When I set them up that way they seemed to align better with less twist. In the photo below you can see how I clamped the parts to the frame.

Then I drilled through the two pilot holes on the bottom angle and countersank for flush head rivets.

Then I squeezed the rivets to hold the angle pairs in alignment. Here is one of the two sets.

Categories: Cabin Frame, Fuselage

Cabin Frame, Part 7: Arch Completed – 6 hrs

January 29, 2012 Leave a comment

Sunday Jan 29, 2012

Another early day in the shop. I spent some time scuffing the parts with scotchbrite this morning and then I washed them all with Simple Green. The sun was beaming down by 8 AM and the weather was great for priming so into the booth these parts went and I put on a good coat of Stewart Systems Ekoprime white. They dried quickly and here they are back on the bench “curing up”.

After lunch I began final assembly of the cabin frame arch. First I riveted the aft sections together with the F-631D angle.

Then I riveted the forward sections together with the F-631E doubler and clecoed on the inner bands.

You can see in this photo that I was able to squeeze all the forward rivets with my pneumatic squeezer. I started at top center again and worked my way down each side.

Then I clecoed the aft section onto the forward section.

You use CS4-4 flush pop rivets to join the two sections together. Boy my thumbs were aching after squeezing all those pop rivets with the manual rivet puller.

Categories: Cabin Frame, Fuselage