SAIL.SailMagazine

If you’ve ever built a model airplane using components cut from balsa, you’ll know what’s involved in constructing an AC45 wingsail. The process is very similar. First you cut out the parts, then you painstaking assemble them into the framework of the wing, then you apply the skin material and shrink it to a tight fit. Here, aerofoil-shaped wingsail ribs, cut from carbon fiber/Nomex honeycomb sheets by a CNC machine, await assembly.

Photo by Peter Nielsen

These spools each hold a few thousand dollars’ worth of pre-preg carbon fiber sheet. “Pre-preg” means pre-impregnated with epoxy resin, which does not  “kick” until heated. The same technique is used to make the hulls and for the wings—a 1mm thick carbon fiber skin sandwiching a Nomex core.

An AC45 wing has two elements. The forward element is a 70ft structure that can be broken down for transportation in a 40ft container. The aft element has three independent flaps; the molds for the leading edges are seen here.

After the Nomex core and pre-preg carbon fiber skins have been laid into the molds, the spar sections have been wheeled inside the oven, where they’re vacuum-bagged and baked at temperatures of up to 300 degrees to cure the epoxy resin and bond the skin and core together.

A wing element takes shape on a jig. This is the forward element. The ribs are glued into place.

Then the rib assembly is bonded to the spar.

These are the three sections of the aft wing element, awaiting their skins.

Core Builders Composites honcho Tim Smyth explains how the plates that control twist in the wing elements work.

Once finished, the sections of the wing are packed into shipping containers and sent off to the teams. Here, France’s Team Energy gets a first look at its wing inside the container.

Photo by Gilles Martin-Raget/Oracle

The light weight of the wing sections is evident in this shot.

Photo by Gilles Martin-Raget/Oracle

The forward element is assembled and the twist control lines are led up the spar.

Photo by Gilles Martin-Raget/Oracle

Because the lightweight plastic film is so easily damaged, it is applied immediately to assembly and shrunk with a heat gun.

Photo by Gilles Martin-Raget/Oracle

“Now which bit is next?” The forward element is being assembled.

Photo by Gilles Martin-Raget/Oracle

“Did we forget anything?” The wing is assembled and ready for action.

Photo by Gilles Martin-Raget/Oracle

It helps to have a windless day, but the installation goes off without a hitch.

Photo by Gilles Martin-Raget/Oracle

And they’re sailing!

Photo by Gilles Martin-Raget/Oracle