46 CLASSIC BOAT APRIL 2016HISTORY OF HOLLOW SPARS
and were hollow, as were masts for the smaller classes. These
restrictions gave rise to such curious masts as that of Maudrey,
Fife’s 1913 15-M, that had a ‘built’ lower mast with a less dense
timber in the middle and a more dense one on the outside.
The Second International Rule of 1921 similarly allowed
hollows above the hounds only (for the top third of the mast);
later the smaller classes were exempted, but there were new
rules on minimum wall thickness and diameter as well. These
restrictions seem to have cemented the notion of sitka spruce as
being the best material for masts in the yachting public’s mind.
When the 1929 rule revision said, for example, an 8-M mast
had to be a minimum diameter of 180mm (0.590ft) at half-
height with a minimum wall thickness of 20% of the diameter,
and also prescribed the amount of taper in the mast, it forced
the spar-makers to use the lightest timbers available.
This general prejudice, along with the 20% wall thickness
‘rule’, is prevalent even today, despite more analytical methods
having been developed before this very conservative rule was
introduced. For example, McGruer had demonstrated that a
wall to diameter ratio of 1:8 to 1:10 was optimal with the
bentwood method. Even now, a thinner wall thickness in a
denser timber (such as Douglas fir) may be a better solution for
a given spar, but spruce remains the timber of choice, almost
regardless of the quality of the actual timber available.
As Olin Stephens knew well, the density of the timber used is
a key factor in mast design. His mast designs often included
notes on the weights of samples of timber used, to let him
control the final weight of the mast with wall thicknesses given
to^1 / 32 in precision, attention to detail that was typical and a
major factor in his success. Between 1850 and 1950, wooden
masts were ubiquitous except for the largest spars which were
made in steel, then aluminium. The earliest aluminium masts
tended to be riveted in sections, often by aircraft manufacturers
and were expensive (Glenn L Martin the aircraft manufacturer
made the aluminium masts for Starling Burgess’ J Class
Weetamoe and Rainbow that were said to have cost $20,000 in
1934 when a spruce one would have been $5,000), but by the
mid 1950s extruded sections were becoming available. These
reduced the cost and complexity of making masts and spars. The
limitation of working with a constant section (unlike a timber
mast which could be varied along its length) was offset by the
better material properties and sometimes by ‘cut & shut’ tapers
for the top section, and in a few years aluminium masts became
in their turn nearly universally adopted. But wooden mast and
spar building never quite died out, and the rise of the classic
scene in Europe and America has started something of a revival.Section of
McGruer spa
from an original
illustrationWhere are we today
Fortunately for those who prefer the gentle strum of
halyards on spruce to the infernal tapping so often
heard in a typical modern marina, the art of wooden
mast building never died out. In some countries it is
even enjoying something of a revival. It is possible to
have wooden masts or spars built in Britain by two
specialist companies, Collars of Oxford and Nobles
of Bristol, and numerous boatyards and boatbuilders
will happily quote for the work too.
Nobles base their spars on a principle developed in
the mid-1980s; now known as the bird-beak or
bird’s-mouth system, it is a refinement of the
barrel-stave system, in which each piece is jointed to
mate to the next and locks in. This prevents the
elements skidding as the clamps are applied. It
requires quite precise machining to make the
geometry work but the results have been very
reliable. It probably represents the only real
innovation in timber spar making, excepting the
glues used, since McGruer’s bentwood system.
Collars, based near Oxford, generally use variations
on the hollowed out method, but produce a very
wide variety of hollow and solid masts and spars, as
well as still building their original speciality, oars.
With modern glues taking much of the uncertainty
out (although gluing failures can and do still occur),
one main issue is sourcing the “clear and better”
grade timber needed. The majority of wooden spars
are of Sitka spruce or Douglas fir, imported mostly
from North America and Canada; Robbins and
Stones Timber in the UK regularly import suitable
stock. One company, Touchwood BV, based in the
Netherlands, specialises in supplying yacht spar
material and offers custom machining. Chantier
Pasqui of Villefranche in France enjoys a good
reputation and a loyal following amongst owners of
the Med-based classics. Brasker at Ventis in
Enkhuisen in Holland has built spars for an enviable
number of the largest yachts sailing today, including
Eleonora, Atlantic and Elena.