Return-Path: Received: from marvkaye.olsusa.com ([205.245.9.220]) by truman.olsusa.com (Post.Office MTA v3.1.2 release (PO203-101c) ID# 0-44819U2500L250S0) with SMTP id AAA11627 for ; Wed, 2 Dec 1998 16:58:45 -0500 Message-Id: <3.0.3.32.19981202165905.02d802f4@olsusa.com> Date: Wed, 02 Dec 1998 16:59:05 -0500 To: lancair.list@olsusa.com From: CHRISTOPHER_ZAVATSON@udlp.com (by way of Marvin Kaye ) Subject: No hard points?? X-Mailing-List: lancair.list@olsusa.com Mime-Version: 1.0 <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> Marv, You will "squash that insulation big time" using the approach in the manual. I didn't like the idea and I wanted a perfectly flat SS firewall when finished. The way I accomplished this was to make spacers which were inserted in the Fiberfrax every place a bolt passed through. For the six engine mount bolts I stacked up AN970 washers to equal the thickness of the Fiberfrax and riveted them together. For all other bolts mounting hardware to the firewall, I machined stand-offs from aluminum rod. The three layers of Fiberfrax were glued together and cut to size. Then I transferred the mounting hole patterns and used aluminum tubing to stamp out holes in the Fiberfrax to accept all of the stand-offs. You have to know where all of your mounting bolts are going to be located, so I waited to very near the end to install my SS and Fiberfrax. In the mean time I had all of my firewall forward items installed on spacers to position them as if the Fiberfrax were installed. I didn't glue in the Fiberfrax or the SS. They are merely clamped in place by every bolt passing through them and could be removed and modified, if needed. In general, it is poor practice to have soft, compliant materials being compressed by critical fasteners. In the firewall case, we also have a sheet of plywood being compressed. So, no matter what you do with the Fiberfrax, you do not have an ideal joint. Torque on the engine mount bolts should be checked regularly because these compliant materials can creep and cause loss of clamp load. You will want to stack at least 2 AN970 washers under the nut otherwise the nut will want to pull through when torqued. AN washers are not particularly strong and a single AN970 washer cannot sufficiently distribute the load when compressing a plywood core. Chris Zavatson N91CZ ----- Marv, You can post the above. I didn't know how what would happen to the attachment. Chris Attachment Converted: "d:\eudora\attach\chris.bmp" [Thanks for the detailed explanation and the photos... looks great. I'll upload the pics to the LML homepage Attachments area later tonight. ]