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Friday, February 15, 2019

Rear Bumper Fabrication Project – Part 4: A Good Part & Critical Decisions

Since the last update, we have had the opportunity to explore using alternative reinforcement materials and, more importantly, a completely different resin chemistry (vinyl ester) in the vacuum infusion molding process we use to produce our composite rear bumper.  After a number of scout procedures, the end result was molding characteristics I simply didn’t like and would not commit to trying any further.  So, not much to report on that front as it’s not got much to do with making a bumper!  Suffice it to say that in any future endeavor, we will stick to our first low viscosity epoxy resin choice and basic combination of reinforcement fabrics and not look back!

With that, the update is rather anticlimactic.  After extensive consideration, we have decided to stay with our 0.137” bumper molding as it is visually almost perfect and will allow greater ease in mounting than a thicker molded copy.  Now the focus will be shifted to developing a robust mount system that can be bonded into the bumper shell with panel bonding adhesive.

Work has begun to craft an aluminum mount that will add good structure to the bumper and provide a solid mounting base that can be easily bolted to the stock mounting locations with a full range of adjustability to allow optimum fit.  At the same time, this strategy will allow the bumper to be fit to the body with simple gap shims that will allow the bumper to be quickly and easily placed in position and aligned on the mounts with perfect body gaps maintained and little to no induced stress into the part while the panel adhesive cures.  Once we’re on top of this series of details, the remainder of bumper work should be relatively conventional insofar as confirming fit and edge finish followed by preparing the part for primer.  Feels good!

In the meantime, work will continue on completing the final bumper trimming, taillight bezel and bucket prep and fitting, backup light housing modification and fitting and final gapping of the doors with the hope of Spring weather allowing a deep-dive into the cleaning and metal prep work on the front sheet metal.  Feels like it’s getting traction again…….


  1. Wow Sven, that REALLY looks good!!! I look at some of the single shots up close - edge details look sharp and clean. Always my complaint regarding f/g parts. The internal matrix is so cool, it will be a shame to paint it!!! Yes, I'm hoping for some progress soon too. Com'on Spring!!!!

  2. I can't imagine the number of hours you've spent on the research and trials to come to the conclusion to proceed with the low viscosity resin. I'm sure the results will be amazing as all of your work is. Keep on keeping on Sven.