Gemini 105Mc Owner’s Manual
33Copyright © 2004 Performance Cruising Inc.
From experience, once there starts to be any move-
ment in an ocean going situation, this small move-
ment rapidly expands to a serious problem. The
Cabospar rig requires the same effort to set and reef
as a normal rig. This rig will require the same effort
as a normal rig with a self tacking jib when sailing to
windward, will be less efficient on a reach (unless
the sheets are eased like normal rig with a self tack-
ing jib), but will be easier down wind when the rig
can be rotated to be at right angles to the wind eas-
ily. Unfortunately, the rig is grossly under-canvased
and spinnakers cannot be used. The rig has a few
unique advantages such as backing up. This rig is
ideal for a Pro.
Main Sail and Reefing
The standard main sail is fully battened and two reef
points. Lazy jacks are included. These sails cannot
be raised or lowered unless the boat is pointing into
the wind. Gemini's pilothouse and the lack of heeling
with wide flat decks makes sail handling easy.
Your 340 sq. ft. main sail is made of 7.3 oz. Dimen-
sion Dacron in a relatively soft finish for easier furl-
ing. The sail has a large roach and extends beyond
the backstay giving additional area which contributes
to greater speed and pointing angle. The sail has
three full-length battens which support the roach.
These battens are tightened by turning an adjust-
ment screw in the batten-end fittings at the luff of
the sail. The batten should be made tight enough so
that there are no vertical wrinkles across the bat-
tened area of the sail. To remove the batten from
the sail, the adjustment screw must be completely
loosened.
The lazy jacks installed on the Gemini mast collect
the main as it is lowered. It is not necessary to
neatly flake the main when storing it. Your main
will come with simple 3’ line sections for sail ties.
There are a number of additional sail tie options
available for purchase at your local marine supply
store. The included sail cover will minimize damag-
ing sunlight and keep your sail in good condition for
years to come.
Should your sail get dirty, you can clean the sail with
standard clothes detergent – making sure to com-
pletely rinse the sail afterwards. In the case of
grease, we have found gasoline to be the most effec-
tive means of breaking down the grease. The sail
can then be further cleaned with detergent.
Sails and Sailing
There are three types of sailing rigs: Masthead,
fractional, and rotating.
The rotating rig is the most efficient with the mast
being supported by a single large shackle on the
front of the mast, with the base sitting on a ball.
The mast, which is normally wing-shaped, can then
rotate in line with the wind. The main sail has a
large roach and full battens. The jib is fractional. As
there are no backstays with a rotating rig, it is not
possible to carry a large headsail. The power from
this rig comes from the main sail, which can be
large. The single side shroud must go to a wide base,
which is why it cannot be used on a narrow
monohull. The wide shroud base and lack of headsail
loads gives a low load system but unfortunately the
whole mast is supported at only one position. The
large fully roached main is very efficient.
The fractional rig is the next most efficient rig. The
side supports to this mast can be any system but the
headstay presents a problem. A permanent backstay
can only be attached to the masthead and will bend
the mast when the backstay is tensioned to support
the headstay. Monohull fractional rig boats will have
a crane at the top of the mast to push the backstay
back as much as possible to allow the main to be as
big as possible. Running backstays are necessary to
support the headstay and to prevent the mast bend-
ing. Large Genoas are not possible. Multihulls, with
their wide beam, are normally set up like the rotat-
ing mast, but fixed. The main sail is large with the
small genoa. Fractional rig boats have a high mast
failure rate.
The Gemini 105Mc uses the masthead rig. The mast-
head rig is the strongest because of the amount of
shrouds that support the mast.
With the rig on the Gemini, we have found a way to
retain the strength of the masthead rig but reduce
the windage and get drive from the top of the sail.
This new technology big head main sail works very
well. The backstays are moved back on a 12" crane
at the top of the mast. The main sail (7 ½ oz cloth
weight) has an elaborate headboard and a fully bat-
tened main that goes behind the single backstay.
This rig gives more power and can be used in higher
winds because of the reduced windage and lower
heeling moment.
There is a newly promoted type of rig called the
Cabospar. This is an un-stayed mast with the boom
being continuous around the mast, going forward to
the tack of the jib. The jib is self-tacking, being less
than a 100% jib. Without shrouds to keep the mast
Sails and Sailing
up, there are a lot of localized forces at cabin top.
None of the un-stayed mast boats produced to date
have been promoted as offshore boats.
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