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RV-3 Seat Pan Notes


VAF Moderator / Line Boy
We?ve been busy with various home improvement projects (balance is important in life ? at least according to Louise!) ever since we flipped the canoe a few weeks back, but that doesn?t mean I haven?t been looking at the RV-3 now and again and doing little tasks every other day or so. On of the great mysteries of this build is how you can start out with a glance at the drawings on a particular part and have absolutely no idea how you?re going to fabricate it ? yet if you look at it over time, letting the brain proess it in the background, eventually, you come up with a way to nibble away at it until voila! You have a part!

The seat pan has sorta? been like that. It is a curved piece of metal that has to fit between aluminum angles at the bottom sides of the fuselage and conform to the seat ribs. There is a tab in back that slides through the F-30 bulkhead to overlap with the baggage compartment floor. The raw stock has a creased bend where there is a transition from the curve to the ledge in the back ? otherwise it is an oversized rectangle. Go ahead ? start cutting! The secret ? as always ? is careful measurement and trimming a little at a time until it fits. Here are a few random notes from how I did it:

1) It took awhile to realize that it can?t fit from side-skin to side-skin ? you can?t install it that way. The width is based on the INSIDE dimension of the angles which are riveted to the tops of the side seat ribs. This is actually easy to measure. It?s also the reason we riveted the outside seat rib extensions on a few months back ? the form ledges on which the side of the seat pan sits.

2) I started laying out the cut lines by marking a centerline from front to back. All measurements were then taken from this. I found the exact center of the fuselage as well ? be careful, it is NOT the center of the middle rib ? it is the flange. This means the center row of rivets is slightly off center. I laid out the rear corner cut-outs for the seat belt anchors pretty much to plans ? but measure as well. The width was measured form the centerline, and I had no noticeable taper at all. I used a dress-makers tape to measure the distance from the aft ?break? line, down and back up the curve of the seat rib to where the forward break line will be. I marked this on the flat plate. Oh ? the back edge will be long, hanging over the rear of the F-305 flange by maybe 5.8?. I left it that way until I had drilled and clecoed the floor in place ? it was easy to trim mark for trimming then.

3) Before fitting, I place the forward edge on the floor and started to bend the pan to give it a semblance of the eventual curvature.

4) I carefully measured from the centerline on the center rib to figure out where the center line of holes needed to go, and laid these out on the floor plan. I then drilled them in advance, and marked a rivet line on the rib flange. Just like lining up wing ribs, I then sighted the lien through the holes to drill.

5) Before drilling any holes, make sure that the aft ?break? line is nestled nicely onto the break in the ribs. Two people help ? one to hold the pan ?down? and ?aft?, and the other to drill. I drilled al the hoes on the aft level portion first (where the flap torque tube will go), then had Louise push down (and back) hard on the curved portion to make sure the pan was in contact with the curve of the ribs before drilling each hole, working from back to front.

6) Very carefully measure and mark each ?middle? rib in the same manner, drilling holes in the floor (on the bench) and then match drilling to the rib lines. Once you drill the side flanges, you can take the center and mid lines of clecos out and sit in the fuselage for the first time! Airplane noises are mandatory.

7) After drilling to the curved portions of the ribs, the forward ?Break? line turned out to be exactly where I had measured it, and I used a neighbor?s three-in-one metal break to bend it about 30 degrees, which was perfect. I have yet to cut off the excess material in front ? it looks to be about two inches, but I will simply mark it to where I want it (I will be doing modified steps and stick mixer close-out panels ala Randy Lervold) ad cut it off straight when ready.

8) Louise is building the seat back while I am doing the floor, and she let me know that she had to have the hinge installed on the floor to make further measurements ? I was standing in the way of progress! This was very easy to place (right at the aft ?break?, according to the drawings), drill, and rivet. It unfortunately covered a couple of my floor mounting holes, but they were easily back drilled through the hinge once it was riveted in place.

All in all, this turned out to much more straightforward than I expected. There are no compound curves, and one you cut the width right, it slips right in. Additional hint - mount the stick mixer first, so you can play with the controls while making those airplane noises!



Now it's on to the Baggage Floor! (You can see the beginning of the template)

I have been off the air for about a month now. Working in Zurich and looking for a place to build. I take a look at VAF and there is a post that inspires me to press on with my Swiss cheese RV3 (It must be built light) from Paul as eloquent as ever.