30 years ago, Sparcraft masts were fabricated with spreaders in line and 4 low stays; the mast was being held at the front and at the back, and the spreader bars were not solicited. Sparcraft used to have stainless steel and riveted plates which still hold very well today – an example is the mast of Arpege, the Dufour boat.
In 1988, the Beneteau Group launched the First 35s5 yacht which had a fractional mast and swept back spreaders. The chainplates on this boat were very narrow in order to sail better upwind. Sparcraft launched their s/s bars for spreaders with integrated anchoring of D1 and D2. The stepping of this type of mast required a considerable pre-bending in order to reconstitute the lack of low stays on the boat, in order to avoid that the mast bends backwards.
Then in 2004, Beneteau launched a premium yacht range destined to charter boats – The Cyclades. In order to minimize compression in the mast, as well as the size of the standing rigging and to get rid of the tie rods in the boat, the chain plates were moved to the maximum of the beam of the boat. As a result, the spreader bars started to elongate, so designers had to make their housing inside the profiles. For that reason, Sparcraft had to stop making the stainless-steel bars and replaced them with aluminum ones – which are the current ones on their rigs.
What is not always common knowledge is that 90% of masts equipped with Sparcraft spreaders with s/s bars are not tuned properly, as they don’t have enough pre-bending. This is why there have been many requests to change these old profiles.