Facnor’s CF fits on the
back of a conventional
mast, offering an
economical conversionFor the past 15
years or so,
Seldén’s Furlin
RB system
has used a
tensioned luff
spar with a
bearing at the top and a
bottlescrew at the bottom
reefing. It has a bearing at the top
and a bottlescrew at the bottom,
and is often used with mainsails
that have full-length vertical
battens to give a positive roach.
Significantly, the other makes
you’re most likely to see – Z Spars
and Sparcraft – have adopted a
very different approach. They
have both chosen to keep
things simple, sticking with an
untensioned luff spar that’s not
even connected to the top of the
mast, thereby eliminating the
need for an upper bearing. It’s
effectively free-floating at the top,
held in position by the halyard
swivel when the sail is hoisted.
Sparcraft maintain that this
reduces compression loads
and, therefore, weight.
Both the Z Spars system and the
Sparcraft Stoway have been used
by leading production builders,
though Z Spars’ has been best
suited to battenless or short-
batten sails rather than those with
full-length battens (this is now
changing with the new mast
sections). So if you buy a
second-hand Legend with an
in-mast reefing system by Z Spars
and a hollow-leech, battenless
mainsail, don’t assume that you
can fit a new main with full-length
battens and a positive roach to
increase the area, because it
might not work. It’s principally a
function of the size of the slot in
the back of the mast.
While the Seldén system now
dominates the market in terms of
new boats, and has proved itself
over many years, it inevitably
needs more care and
maintenance than the simpler
alternatives and it also costs more
to buy. For example, Z Spars
(whose system has much in
common with Sparcraft’s) make
the point that all the component
parts are easy to replace and that
even a complete new system to fit
inside the existing mast can be
bought for as little as £550.
As is often the case, you have
the choice of paying for more
complex engineering that offers
additional features, or opting for
economy and simplicity.Options for upgrading
If you have an existing in-mast
system, you might well be able to
upgrade it without changing the
mast or rigging. That will depend
on its age, and you will need to
talk to the supplier to see what’s
possible. Most Seldén in-mast-
reefing masts from the past 25
years can accept the latest Furlin
RB system. Those less than about
10 years old can usually be
upgraded without the need even
to change the standing rigging or
move the spreaders, but each rig
needs to be looked at individually.
Z Spars and Sparcraft (the latter
having bought Isomat and
Francespar, and now a sister
company of Facnor) have
changed their systems relatively
little over the years, so again
there’s a good chance that an
existing one can be replaced or
upgraded inside the same mast.
That’s all very well if you already
have in-mast reefing – but what
if you have a conventional rig and
want to convert to in-mast? In this
situation you can remove the
existing rig and start again from
scratch – that’s the expensive
route – or consider the Facnor CF,
which fits behind the mast.
Like the Sparcraft system it’s
fundamentally a rotating luff
spar with the halyard
swivel at the top, but
this time it lives in its
own separate housing
fitted to the track of the
existing mast (without
the need for any holes
to be drilled). It’s not as
elegant as an integral
system, and windage
is inevitably added,
but it’s a lot
less expensive.In-mast reefing
➜
I
n-mast systems won’t
tolerate stretched and
baggy old sails. The bulk
caused by the stretched
fabric will lead to increased
friction at the very least, and
eventually to jams. Owain
Peters from Kemp Sails says
that a sail can be recut once –
usually having a crescent cut
out of the luff – but after that
it’s time for a new sail.
With a fully-battened sail
there’s even less tolerance
for stretch, because once the
battens are no longer parallel
with the slot in the back of
the mast they’re unlikely go
through. When designing the
sail, the sailmaker needs to
make sure each batten meets
the mast perfectly parallel as
it’s rolled in. That calls for
accurate measurement.
The luff length needs to be
measured carefully, too. It’s
common to see in-mast sails
with their head well below the
top of the mast, possibly due
to caution on the part of the
sailmaker. Excessive luff
length would lead to
problems with the Seldén
system in particular if the
halyard swivel ended up
being pulled against the
top bearing.
Because of the limitations
imposed by factors such as
the width of the slot in the
back of the mast, in-mast
mainsails often need to bemade with a lighter fabric
than would be used for a
conventional mainsail.
Particularly if you’re planning
to sail long distances, bear in
mind that chafing patches have
to be sacrificed. Chafe can be a
problem with full-length vertical
battens, and Peter Sanders is
one sailmaker who wouldn’t
recommend them for offshore
cruising for this reason.Fractional rigs
Given that a luff spar needs to
rotate freely inside the mast,
there are limitations to the
amount of pre-bend that can
be set into a rig before the
system no longer works. As
a rule, fractional rigs are
designed to be set up with
more pre-bend than masthead
rigs, though the newer,
high-fractional configurations
are generally both stiffer and
straighter than the whippy,
low-fractional rigs of the 1970s
and 1980s. If a rig is of the type
that needs more than a minimal
amount of pre-bend, in-mast
reefing might not be an option.
Apart from the issue of the luff
spar accommodating the bend
in the rig, a sail for in-mast
reefing can’t be cut with the
necessary luff round because
the extra fabric won’t roll in
flat – just like an old sail
that has stretched.More than minimal
pre-bend might
rule out in-mast
reefing, but
here’s a Sanders
sail on a
Legend with a
Z Spars rigSails for in-mast reefing