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RV-7 Construction Log
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Date:  2-15-2014
Number of Hours:  5.90
Manual Reference:  p. 8-6, 8-4
Brief Description:  Center Fuselage & Longeron Bending

I started today by drilling the right outboard F-715 seat rib to the F-704 and the side skin. I then removed the side skins, and match drilled the top flange of the outboard seat ribs through the floor pans, using the method suggested in the instructions (photo 1).

Next, I spent some time looking at longeron bending on the Orndorff RV-7 fuselage video, then proceeded to set up to use that method to bend mine. I started by choosing the smoothest ends of the longerons, and made them the front. I clamped the two longerons back to back about every 18 inches for about half the length, and then added a few clamps and tape wraps on the aft half.

I then carefully measured the three points called out on drawing 18 (photo 2). The forward most point is where the downward bend is located; the next one back is where the shallow bend starts; and the aft most is the end of the shallow bend. I marked the points with masking tape to get precise lines, then marked both longerons for left, right, forward, and aft, and marked the sections between the marks for the type of bend they'd be getting.

The actual bending was quite a bit more difficult for me that it is for George in his video. I'm not quite tall enough to really get my weight on the longerons while they're in the vise, so I tried Karen's aerobics step, which helped, but I still had trouble getting enough weight on both sides to effect much of a bend. I tried clamping the longerons to the vice aft of where I was trying to bend, but it got tedious unclamping and reclamping when checking the bend. The best method was to have Karen lean on the longerons aft of the vice while I pushed with both hands on the forward end. After about a dozen iterations we got the bend to match the curve on drawing 17 within the width of the line (photo 3).
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Positioning the rib flange for drilling through the seat pans.

Positioning the rib flange for drilling through the seat pans.

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Longerons clamped together in  preparation for using the Orndorff method of bending.

Longerons clamped together in preparation for using the Orndorff method of bending.

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Longerons match the drawing within the width of the line.

Longerons match the drawing within the width of the line.

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