Gestalt said..Footstrap plugs getting evolution. Will use these on my next build because it ditches the silly screw issues. First photo from sanded. not sure how the Flikka ones work in the second image.. does anyone know.. are they held in by the sandwich?
The welded plate things have been around for a while. Big Head fittings or similar are used extensively in the marine game. Technifast in the UK also do a really good range. I'd assume those square corners in the image would be rounded off prior to installation. Rules of point loading 101...
The Bigheads are normally placed into the laminate late-ish during the construction sequence and mostly used on parts created from female moulds. As example, if the top of the Bighead is to be flush with the exterior of the finished job, you de-core and bring the inside and outside skins together in the local area while the part's in the mould. Next there's local reinforcement placed in way of the Bighead then it's glued into place. Lastly its bonded over with a cover laminate. Structural laminating complete at this stage. Once the part is released the service hole is opened and lightly re-taped using a bottom tap to clean out any glue. Finally its countersunk to keep the laminate back from the edge entry so you get metal on metal threading.
Guess you can tell I've done 1000s of these... Mostly on high performance yachts and anything pre-preg.
www.ecfibreglasssupplies.co.uk/bighead-inserts-and-fasteners?srsltid=AfmBOoq8oGZHhsFmTW4PCGs8EF_L4ZS2OQArpqEtFvddcFebwtwd1esQ
