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Hood Bonding

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  • Joe C.
    Expired
    • August 31, 1999
    • 4598

    Hood Bonding

    This question applies to midyear Corvettes. Why isn't the hood skin bonded to its inner frame with the same bonding resin used throughout the car. The material used is a semisoft, reddish-orange compound. What would be the consequence of bonding with polyester bonding resin?
    Thanks in advance.

    Joe
  • John H.
    Beyond Control Poster
    • December 1, 1997
    • 16513

    #2
    Re: Hood Bonding

    Joe -

    The inner is only bonded (with polyester resin bond) to the outer around its periphery; the material between the inner panel "beams" and the inside of the outer panel is a flexible mild adhesive, called "hood gumdrop adhesive" in the trade. If you use conventional polyester bond material at those locations, you risk distorting the outer panel surface from "bond burn".

    Comment

    • William B.
      Very Frequent User
      • April 30, 1975
      • 939

      #3
      What shoud you use for rebonding?

      My hood is not attached to the center bracing and vibrates often. What product should be used for repair? Or any advice on how to repair?

      Comment

      • Michael H.
        Expired
        • January 29, 2008
        • 7477

        #4
        Re: Hood Bonding

        John,

        Have to wonder why 63-64 hood reinf used bond and the 65-67 used gooey adhesive that never stuck to anything. I don't think I've ever seen a 63-64 that came loose other than from a collision but it seems all 65-67's become unattached. I know there was a "bond burn" issue that started in 63 but it was the fenders, not the hood that had the problem.

        Comment

        • Joe C.
          Expired
          • August 31, 1999
          • 4598

          #5
          I Have A Phenomenon With My Hood!!!

          John and Michael:

          I'd like to know what "bond burn" is, and how it manifests. I have a very strange phenomenon occuring with my 1965 hood.

          Joe

          Comment

          • Michael H.
            Expired
            • January 29, 2008
            • 7477

            #6
            Re: I Have A Phenomenon With My Hood!!!

            Joe,

            Bond burn occurs when the new panels are bonded together at the assy plant, usually due to a slightly over rich mixture of kicker in the mix. The bond becomes so hot that it actually begins to deform the panels that are being assembled. This typically shows up as ripples or valleys in the finished body. It was one of the main reasons why 63 was the last year that the front skirts were completely bonded to the fender tops.

            What's happening with your hood?

            Comment

            • George C.
              Expired
              • November 1, 2001
              • 568

              #7
              Re: I Have A Phenomenon With My Hood!!!

              I have just "glued" the hood on my 65 back together. I went to NAPA, Auto Zone and others and nobody had "hood mastic" or gumdrops. Based on information I found in the archives I went to Lowes and after reading the labels on about 20 different tubes, settled on an adhesive that said fiberglass and stays flexible. It took 3 days to set up, but I think it will work out ok.

              Now for my question, Bubba had solved the problem by using pop rivets which I drilled out and am in the process of filling. Can someone post a photo of the inner hood panel, I think the holes are supposed to be in the tabs where you put the adhesive but I don't know. There are two holes in each large tab, and 1 hole in the smaller ones.

              Thank you in advance,

              George

              Comment

              • Tracy C.
                Expired
                • July 31, 2003
                • 2739

                #8
                We call that "exotherm" in the composite biz *NM*

                Comment

                • Wayne W.
                  Extremely Frequent Poster
                  • April 30, 1982
                  • 3605

                  #9
                  Re: I Have A Phenomenon With My Hood!!!

                  Actually, except for the some very early units, 63 innerfenders were not bonded either. They had a black non hardening material on them at the top of the bonding strip.

                  Comment

                  • Michael H.
                    Expired
                    • January 29, 2008
                    • 7477

                    #10
                    Re: I Have A Phenomenon With My Hood!!!

                    Wayne,

                    I was reasonably sure that most 63 skirts were bonded to the underside of the fender tops with normal production bond but thought I'd get more info to be sure. I just talked to Bob Jorjorian and he happened to have an original front fender from a a 63 in the 8xxx ser # range. The area where the skirt was attached to the underside of the fender was definitely conventional hard set bond. The skirt is no longer present but the line of bond remains and it's rock hard.

                    I know this area went through a few changes later in the 63 production run so it is possible that much later cars used the process that you describe but I believe the majority of the 63 run used hard bond for this app.

                    Bob sent a pic and I can post it if necessary.

                    Comment

                    • Gerard F.
                      Extremely Frequent Poster
                      • June 30, 2004
                      • 3803

                      #11
                      Hood Gumdrop Adhesive

                      John,

                      Is there an available substitute for the hood gumdrop adhesive. It has been long gone on my 67 hood, and the hood bounces around.

                      Wondering if a roofing adhesive would do it, or would break loose with heat.

                      Regards,

                      Jerry Fuccillo
                      #42179
                      Jerry Fuccillo
                      1967 327/300 Convertible since 1968

                      Comment

                      • Wayne W.
                        Extremely Frequent Poster
                        • April 30, 1982
                        • 3605

                        #12
                        Re: Hood Gumdrop Adhesive

                        I dont know exactly where the change occured but I hardly ever see a hard bonded one. Most have a black porous material that is not the same as the bonding agent. It may have been as late as 10K but I doubt it. This is near the time when the front bonding strip was changed to the later style. Maybe the change was about that time.

                        Comment

                        • Tracy C.
                          Expired
                          • July 31, 2003
                          • 2739

                          #13
                          Re: Hood Gumdrop Adhesive

                          The black 3M windshield caulk (putty) should be pretty close.

                          tc

                          Comment

                          • Terry F.
                            Expired
                            • September 30, 1992
                            • 2061

                            #14
                            Re: Hood Bonding

                            Duramix makes plastic bumper adhesive that is rated as non-hardening as I recall. It is made for fixing gouges and stuff in rubber bumpers on new cars. Might look into it. Get it at auto paint stores. Terry

                            Comment

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