Forestay Attachment and Wet Preg: Engineering the Pin Into a Carbon Longeron
Attaching a forestay to a carbon longeron built from recycled mast sections isn’t a standard job. There are no off-the-shelf fittings for this configuration — the geometry is specific to this mast, this boat, and this longeron position. Shayne spent a lot of time considering options before settling on a transverse pin and dual-slot arrangement that transfers load directly into the large unidirectional carbon planks that run through the back of the original mast section. That’s where the strength is, so that’s where the load needs to go.
The pin is 19mm Nitronic rod — salvaged from the old standing rigging, which is exactly the kind of material reuse that underpins this whole build. Nitronic is the right choice here: stronger than standard stainless in tension, better corrosion resistance, and it plays slightly less badly with the carbon than regular 316 would. The slots for the toggle took more fitting than expected — careful grinding, checking, grinding again — but it needs to be right because this is the load path for the entire rig.
The reinforcing patches around the pin connection were laid up using wet preg — a technique Shayne learned in New Zealand before prepreg became the standard method for race boat construction. The principle is straightforward: rather than building the laminate directly on the part where resin content is hard to control, you wet everything out on a table first. A template marks the exact size and stagger for each layer. The carbon is cut, wetted out, built up into a complete multi-layer patch with all the overlaps precisely positioned, then sandwiched between two sheets of plastic. You walk the whole wet assembly out to the job and apply it in one hit, then bag it. You know the fibre-to-resin ratio is correct before the laminate touches the part. It’s more controlled, more repeatable, and produces a better result than wet layup directly on a complex surface.
The inner forestay attachment — the point for the storm jib and small jib — went in at the same time. A soft loop around the uni plank inside the longeron, a thimble and friction ring, a two-to-one purchase to the furler unit. That arrangement means the inner forestay is completely removable when not needed and simple to set up when it is. In heavy air, instead of rolling away the big headsail and destroying its shape, you pull up the storm jib or trinket from the inner attachment and sail on something designed for the conditions.
The pin cover arrangement was still being refined at the end of this video — Shayne wanted to square the pin up, increase the bearing area, and improve how it locked off. That was added to the list before departure.
In the Members Library
The full front end rebuild series — from the first beam sections through to sea trial — plus the extended engineering detail behind the pin and slot design, the wet-preg lamination process step by step, and load calculations for the forestay attachment.
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