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Archive for January, 2012

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.

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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

Cabin Frame, Part 6 – 5 hrs

January 28, 2012 Leave a comment

Saturday Jan 28, 2012

I was in the garage working on the project by 6 AM this morning. I was anxious to finally finish the cabin frame. The weather forecast for tomorrow is warm and I hope to get these part primed. First step was to finish match drilling the holes on the inner edge for the forward section. First I transferred the vertical centerlines from the holes on the aft sections below, then I measured up 1/4 inch from the edge of the flange. For each hole I measured the thickness of the frame at the hole location and made adjustments as necessary to get 1.5 inch overall, then drilled and clecod the hole. I repeated that for each hole starting at the top center and working my way down both sides.

Then I put the F-631E doubler plate on the forward side and match drilled that.

Speed picked up a bit when I re-drilled all the holes to #30.

Next I countersank all the edge and forward side holes for flush rivets. I used my countersink cage even though some people have written that it did not work well for them. It worked fine for me with a few adjustments to compensate for the radius of the frame.

Then I disassembled the frame for deburring and aligned the F-631D angle on the aft side of the top center of the arch and match drilled that.

Here is the pile of parts after deburring all those holes.

Categories: Cabin Frame, Fuselage

Cabin Frame, Part 5 – 2.5 hrs

January 27, 2012 Leave a comment

Friday Jan 27, 2012

It’s been quite a busy week. So it’s good to get back on the project tonight after a few days away. Tonight I drilled all of the outer holes on the forward sections of the cabin frame. Turns out the wood blocks did not work as well as I had hoped because the arch section so of the frame are not really flat. They have a bit of twist to them that makes it hard to get them to lay down flat on the blocks. I actually ended up measuring the thickness of the assembly at each hole and made small adjustments to get the 1.5 inch overall thickness called for in the plans. It just took longer than expected.

Categories: Cabin Frame, Fuselage

Cabin Frame, Part 4 – 1.5 hrs

January 24, 2012 Leave a comment

Tuesday Jan 24, 2012

Tonight a made six wood spacers to place between the cabin frame sections to set the overall thickness at 1.5 inches while drilling the holes in the forward pieces and the inner bands.

Then I transferred the hole markings from the aft sections to the forward sections in preparation for drilling. That’s all the time I had tonight and for a while because I expect my day job to keep me tied up for the next few days.

Categories: Cabin Frame, Fuselage

Cabin Frame, Part 3 – 1.5 hrs

January 23, 2012 Leave a comment

Monday Jan 23, 2012

Tonight I set up and drilled the holes for the upper band of the cabin frame. Of course I had to round the edges of the band as I did on the lower band and the process of marking the location for rivet holes was the same with the tape method only this time there were a few more holes. Do you think I have enough clamps on the table?

Once it was drilled I could not resist putting the forward F-631 channels on to see how they fit. I would say rather like a glove – but I can see the utility of some 1 and 3/8 inch spacers to put under the forward channels to control the overall thickness at 1.5 inch. I’m surprised Vans does not recommend doing this. It’s not that they advise against it. The plans are just silent on how to align the forward channels.

Categories: Cabin Frame, Fuselage

Cabin Frame, Part 2 – 4 hrs

January 22, 2012 Leave a comment

Sunday Jan 23, 2012

My project detour for today was to install the elevator bellcrank in the aft fuselage. It doesn’t really need to be done now but I felt like doing it anyway. It took 5 minutes and turns as smooth as silk.

Then back to the cabin frame. The first step today was to measure the width of the fuselage to determine how wide the arch should be. The plans say the nominal is 42 and 5/32 not including the two 3/16 angles on the ends. My fuselage measured 42 and 9/16 overall. When the two 3/16 angles are subtracted that leaves 42 and 6/32; or 1/32 over nominal. Not bad.

Then I paired up the F-631 parts and measured the width and height of the arch. The first pair was 3/16 too wide and the second pair was 1/32 too narrow. For some reason Vans gave me six of the F-631 channel parts in my fuselage kit and when I compared them they were not all the same size. So I tried different combinations until I found the best pairs. One pair was essentially right on the desired width but the other needed about 3/32 trimming. The height was too large in both cases and I had to trim all four pieces by almost 1/8 inch. Fortunately I had not drilled the access hole yet like the plans said because if I had they would have both been too low.

I marked the locations for the access holes. Notice there is a pilot hole close but not at the right location. This will make drilling the access holes a bit tougher.

So first I drilled a new pilot hole at the right location on the drill press with a block of wood behind it. That guided the hole saw pilot drill so the actual cutting of the 1.5 inch hole was easy.

Here are the two 1.5 inch access holes drilled and deburred.

Next I took a piece of  3/4 MDF and made a jig to hold the frame. I cut the basic arch shape into the jig so I could clamp the pieces down well with C-clamps. I started with the aft pair and clamped them up. I used a 3/4 x 3/4 x .125 angle as a straight edge to ensure the two lower edges were square and to allow me to measure the height at the center. You don’t see it in the picture below but I put the F-631 plate on next at the top joint of the channels and match drilled and cleco’d.

The preparing inner strap turned out to be a pain. This thing is too wide and the edges interfere with the inside radius of the channels. I had to sand 1/32 inch off the width and round the edges to get the strap to sit low enough to achieve the required 1.5 inch overall thickness of the frame. You can see the rounded edges in the picture below.

To locate the holes for the rivets on the inside edge I used the method described by Mike Bullock. I first put a piece of blue tape on the inside edge of the channel and marked the location for the first and last hole on each channel. Then I took the tape off, laid it out on the table and marked 19 equally spaced lines between the two end rivet marks. Then I put the tape back on and clamped the strap on the inside lip of the channel. Then I found a block of wood the right thickness to use as a guide to mark the vertical distance of each hole centerline off the surface of the MDF jig. I used a 12 inch #40 drill to drill through the channel and strap starting at the top center of the arch working down each channel clecoing as I went. Not too hard so far but a bit time consuming.