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RV-7 Construction Log
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Date:  3-20-2014
Number of Hours:  1.80
Manual Reference:  p. 8-7
Brief Description:  Forward Fuselage - Firewall Fitting

Another couple of rounds of longeron twisting, and think I may have finally got the firewall fit to the forward fuselage. I started today by measuring the longeron angles with the firewall clamped in place from the last work session. The left side was about 17 degrees, but the right was only about 13 degrees. WTF? After removing the firewall from the fuselage and measuring the angles on the engine mount brackets, I found both were 17 +/- a few tenths of a degree. With the firewall removed, the relaxed angles of the longerons were about 16 and 12 degrees for the left and right, respectively.

When re- twisting the longerons, I noticed that the twists relax a few degrees in the short amount of time it takes to twist the other side. For the final fit, I finally got both sides twisted to about 19 degrees, but by the time I refitted the firewall, they were back to 17.

I lightly clamped the brackets to the longerons with the firewall slightly forward of its final position so I could check the fit between the forward ends of the brackets and longerons (photo 1). I then re-clecoed the side skins and made a first cut at setting the fore-aft position of the firewall. The instructions have you check for 5/8" from the forward edge of the side skins to the forward face of the firewall, as well as align a centerline on the bottom stiffener angle through the second row of holes in the bottom skin. I can't get both at the bottom, because with the centerline centered in the bottom skin holes, the forward face of the firewall is about 11/16 aft of the side skins. I think I'll go with 5/8" firewall setback at top of the side skins, and the bottom angle centered in the skin holes.
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Fit at the forward end of the longeron.

Fit at the forward end of the longeron.

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Fit of the upper left engine mount bracket.

Fit of the upper left engine mount bracket.

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Upper right.

Upper right.

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