As for the Vredenburger - it existed as a fishing boat hull long before the navy bought it. I just wish I can remember the name of the boatbuilder - I used to pass his outfit regularly but have forgotten his name.
It's just come to me - Sachal - was the builder, at one time in the sixties arguably the world's leading experts in glass fibre fishing vessels. IIRC Sachal was formed by the amalgamation of three yards in the area. One of them was owned by someone my alzheimer-raddled braincell seems to recall as an old pal of my father's by name of Tully? or maybe Tallie?.
OK using that as a search criteria I found this in a 2009 document:
SACHAL & STEVENS (PTY) LTD : Sadly this boatyard, situated at Vredenburg, near
Saldanha, is to be auctioned off this month, complete with moulds for boats ranging in
length from 8 feet to 80 feet. Sachal Glass Fibre Industries was started about forty years
ago by the late Alfred Tallie, a Maltese boat builder, together with his brothers and a
partner, Charles Hutchinson. For years the company built a range of GRP boats for the
local fishing industry and also the S.A. Navy and the Army (4 Recce Regiment). After
Alfred’s death the firm was sold to become Sachal & Stevens, a company employing
computerised hull fairing and other computer aided design methods. Boats built by the
Company are to be found at ports all around the coast and also in Antarctica,
Mozambique, Zambia, Malawi, Angola, Seychelles and at St. Helena Island.