Date: Tue, 09 Jul 2002 21:13:22 -0400 From: "Marc J. Zeitlin" Subject: COZY: Engine Mount Reinforcement Issue David M de Sosa writes: >I have recently discovered that the four 1" square aluminum engine mount >reinforcement blocks were never installed >........The upper left and right...... The question is, is it better to cut >through from the front side of the firewall or the back or does it matter? I'd cut through from the inside for the uppers and patch the inside. You'll put so much glass over these areas later that this won't matter. Use a 1 BID patch (That's what the original glassing was) with the flox, and you'll be fine. >The lower left and right reinforcement locations are not so straight >forward to deal with. One of the nice things about glass work is that ANYTHING is fixable. Here's what I would do. Cut out a square hole through the glass and plywood on the exterior of the lower mount points, and leave the bazillion layers of glass on the inside alone. Scarf the 3 layers of UNI and 3 layers of BID toward the inside, bottom, and top of the hardpoint for a distance of 5 inches in all directions. Next, flox the hardpoint in place and lay up the 3 layers of 4" wide UNI. The first layer should start 2" from the beginning of the scarf area around the fuselage side, and continue to a point 1" - 2" past the hardpoint on the firewall. The second layer should start 1" from the beginning of the scarf area and stop at the same point as the first layer. The third layer should start at the beginning of the scarf area and stop at the same point as the other two. Next, layup the 1st layer of BID overlapping the UNI on the firewall and 1" outward onto the scarf areas in all directions. Layup the second layer of BID 1" further in all directions from the first layer. Now, what you've got is a patch that's at least as strong as the original layups, with the same # of glass layers in the same orientation, with the hardpoints in the right place and no extra thickness where the engine mount will touch the firewall. Hope this helps. -- Marc J. Zeitlin mailto:marc_zeitlin@alum.mit.edu http://users.rcn.com/marc.zeitlin/