Stevea
Well Known Member
Just finished trimming my epoxy/glass cowl to fit the -6A firewall and am starting to fit the cowl to firewall hinges. After searching my (ancient and mostly not helpful ) builders manual, scanning the -6 and -7 prints in my collection, I still can't figure this one out.
On the curved hinge section across the top of the firewall with the undersized pin installed (0.090" pin in 0.125" hole), what keeps the aft edge of the cowl in line with the forward edge of the top skin? I'm thinking in flight differential pressure loads and/or engine vibration and/or curvature mismatch between the cowl and firewall as possibly causes of movement. (My cowl is about 1/16" high in the center, a couple inches either side of center line, fits well everywhere else.)
With the cowl and firewall hinge halves aligned on center, there is +/- 0.0175" (0.035" total) vertical movement possible between the cowl and skin. OK, in reality the cowl can not really move below the skin by much because it will be stopped by the hinge eyelets on the firewall side. But......it can move up by some amount, depending on the initial alignment of the hinge halves. Has anyone offset the nominal position of the hinge halves using shims to prevent the cowl from moving up?
I have searched everything I could find about cowl fitting on the Van's Air Force site, the Matronics RV list, and my favorite "wonder how they did it?" builder websites. Lots of information, lots of great photos of the process......but nothing that answers my questions.
5753 flying.......somebody has to have figured this out....other than using camlocks
On the curved hinge section across the top of the firewall with the undersized pin installed (0.090" pin in 0.125" hole), what keeps the aft edge of the cowl in line with the forward edge of the top skin? I'm thinking in flight differential pressure loads and/or engine vibration and/or curvature mismatch between the cowl and firewall as possibly causes of movement. (My cowl is about 1/16" high in the center, a couple inches either side of center line, fits well everywhere else.)
With the cowl and firewall hinge halves aligned on center, there is +/- 0.0175" (0.035" total) vertical movement possible between the cowl and skin. OK, in reality the cowl can not really move below the skin by much because it will be stopped by the hinge eyelets on the firewall side. But......it can move up by some amount, depending on the initial alignment of the hinge halves. Has anyone offset the nominal position of the hinge halves using shims to prevent the cowl from moving up?
I have searched everything I could find about cowl fitting on the Van's Air Force site, the Matronics RV list, and my favorite "wonder how they did it?" builder websites. Lots of information, lots of great photos of the process......but nothing that answers my questions.
5753 flying.......somebody has to have figured this out....other than using camlocks