Question for chassis engineers about seam sealer and structural adhesives.
Question for chassis engineers about seam sealer and structural adhesives. It is my belief that seam sealer and undercoating does not contribute to the structural integrity or stiffness of a unitized vehicle. Both being utilized to simply combat moisture intrusion and corrosion. I would like to discuss the effect of removing all seam sealer and undercoating in an effort to reduce weight. We have all seen how much extra sealer and undercoating is applied at the factory in haste.
I am currently thinking some form of water barrier will be needed where panels are spot welded together. Would there be any advantage to applying a thin bead of panel bond or stronger structural adhesive instead of just reapplying a more efficient (than factory) bead of seam sealer? Could the structural adhesive perform similarly to the stich welding techniques employed by extreme race car builders?
Sorry to ramble, but now I am wondering about the effectiveness of stitch welding vs the typical use of subframe connectors. To me, stitch welding for improved structural performance implies that prior to stitching; the structure was flexing / rippling where the panels meet. Essentially straining and pulling against the factory spot welds. Builders then apply a continuous bead or stitches to convert spot welded sheet metal to a pseudo tube frame.. I find it hard to believe that any modern unitized structure is moving where panels are joined, even under racing conditions. It seems more likely that flex is a result of a chassis designed with poor placement of its structural members, braces and gussets etc.. Leaving heavy subframe connectors and strut tower braces as our only option to improve stiffness of poorly designed platforms.
I am currently thinking some form of water barrier will be needed where panels are spot welded together. Would there be any advantage to applying a thin bead of panel bond or stronger structural adhesive instead of just reapplying a more efficient (than factory) bead of seam sealer? Could the structural adhesive perform similarly to the stich welding techniques employed by extreme race car builders?
Sorry to ramble, but now I am wondering about the effectiveness of stitch welding vs the typical use of subframe connectors. To me, stitch welding for improved structural performance implies that prior to stitching; the structure was flexing / rippling where the panels meet. Essentially straining and pulling against the factory spot welds. Builders then apply a continuous bead or stitches to convert spot welded sheet metal to a pseudo tube frame.. I find it hard to believe that any modern unitized structure is moving where panels are joined, even under racing conditions. It seems more likely that flex is a result of a chassis designed with poor placement of its structural members, braces and gussets etc.. Leaving heavy subframe connectors and strut tower braces as our only option to improve stiffness of poorly designed platforms.
Last edited by RADONE; Sep 21, 2013 at 10:09 PM.
It is my belief that seam sealer and undercoating does not contribute to the structural integrity or stiffness of a unitized vehicle. Both being utilized to simply combat moisture intrusion and corrosion. I would like to discuss the effect of removing all seam sealer and undercoating in an effort to reduce weight. We have all seen how much extra sealer and undercoating is applied at the factory in haste.
I am currently thinking some form of water barrier will be needed where panels are spot welded together. Would there be any advantage to applying a thin bead of panel bond or stronger structural adhesive instead of just reapplying a more efficient (than factory) bead of seam sealer? Could the structural adhesive perform similarly to the stich welding techniques employed by extreme race car builders?
Sorry to ramble, but now I am wondering about the effectiveness of stitch welding vs the typical use of subframe connectors. To me, stitch welding for improved structural performance implies that prior to stitching; the structure was flexing / rippling where the panels meet. Essentially straining and pulling against the factory spot welds. Builders then apply a continuous bead or stitches to convert spot welded sheet metal to a pseudo tube frame.. I find it hard to believe that any modern unitized structure is moving where panels are joined, even under racing conditions. It seems more likely that flex is a result of a chassis designed with poor placement of its structural members, braces and gussets etc.. Leaving heavy subframe connectors and strut tower braces as our only option to improve stiffness of poorly designed platforms.
I am currently thinking some form of water barrier will be needed where panels are spot welded together. Would there be any advantage to applying a thin bead of panel bond or stronger structural adhesive instead of just reapplying a more efficient (than factory) bead of seam sealer? Could the structural adhesive perform similarly to the stich welding techniques employed by extreme race car builders?
Sorry to ramble, but now I am wondering about the effectiveness of stitch welding vs the typical use of subframe connectors. To me, stitch welding for improved structural performance implies that prior to stitching; the structure was flexing / rippling where the panels meet. Essentially straining and pulling against the factory spot welds. Builders then apply a continuous bead or stitches to convert spot welded sheet metal to a pseudo tube frame.. I find it hard to believe that any modern unitized structure is moving where panels are joined, even under racing conditions. It seems more likely that flex is a result of a chassis designed with poor placement of its structural members, braces and gussets etc.. Leaving heavy subframe connectors and strut tower braces as our only option to improve stiffness of poorly designed platforms.
However the Urethane used to bond windshields does offer structural support in that area.
Panel adhesives only work when used properly between two panels. Applying them over the top would give no gain in strength.
Now with that being said, Have you ever seen a Body in white??? There typically offered from the factory to be used for racing applications only. The also don't typically get the seam sealer and under coating that a full production body would receive.
As far as automobile structures go Keep in mind they are designed to rigid only up to a certain point. They need to have area's that can flex and distort in a crash. This is how they maintain their Crash Safety standards. Go look up the high speed crash videos they do for automobile testing were they slow the video's down. You will actually see the structural parts of the car transmitting the energy around the outer shell.
Here is a few of the many videos on You tube. Watch the roof and glass area distort and flex during the impact. The last one explain the testing process
