Replacing a mast can be a confusing business, but getting the right one can have a transformative affect on your boat’s performance as Sam Fortescue explains
It had never occurred to me as a sailor that the mast of my Sadler 34 was an upgradable piece of kit. In my mind it was as integral as the keel or rudder and had little potential for better performance. Or so I believed. It has been a horizon-broadening experience to speak to leading mast builders and installers to hear just what is at stake with good spar design.
On the cruising side, most of us will have a solid aluminium spar stayed with wire rope. Older boats up to 35ft might have a single set of lateral spreaders, while larger yachts could have two or three. Modern boats tend to have more spreaders, often swept back to add extra stability. But a growing minority of luxury bluewater cruisers are being fitted with carbonfibre spars from the off. And in many racing classes, you simply wouldn’t be competitive without it.
The vast majority of new masts are supplied to new boats, but there is a small refit market as well. Usually, the existing aluminium mast has been damaged or run its natural life and needs to be replaced but occasionally there is demand for an upgrade from aluminium to carbonfibre. Advanced Rigging & Hydraulics of Port Hamble has lots of experience here, and performed the work for the First 40 and Hylas 54 detailed in the box-outs that follow.
Aluminium craft
Aluminium is a relatively soft metal with a high strength to weight ratio – all characteristics that suit it for spar making. The process involves extruding a long, hollow form by pushing warmed aluminium through a precisely shaped die. Single sections can be produced up to about 20m in length, so taller masts must be spliced together. There are many alloys available, but one stands out for marine use.
“We use 6000 aluminium because it’s easy to extrude and has good corrosion resistance, good aesthetics,” says Selden MD Steve Norbury. “All of the grades in that series have the same modulus, so there’s no gain in stiffness by going to a different grade. Higher modulus aluminium alloys don’t extrude, or corrode more easily.”
There is vigorous online debate about the suitability of different 6000-series alloys. Some say that 6061 is susceptible to faster corrosion with its higher (0.4 per cent) copper content. It is commonly used, however, alongside lower copper 6063 and 6082 types. Silicon is added to all these to soften the alloy for extrusion.
“Aluminium
