Note: Descriptions are shown in the official language in which they were submitted.
CA 02789767 2012-08-14
MAST FOR SAILING VEHICLES
The present invention relates to a mast for dinghies, sailing ships and
sailing
vehicles of any type, which consist of two mast halves placed laterally apart
and
transversely to the longitudinal axis which are outwardly curved, arched or
run straight,
and merge at or under the top of the mast and reach the largest structural
width so that the
stay deployed centrally between the mast halves or the luff of the sail
creates a vertical
tension and the spokes deployed transversely between the mast halves support
the
transverse forces, wherein dimensional stability of this construction and
statistical
advantage is achieved with their arrangement and number. The design of the
mast profile
is provided preferably with an aerodynamic form in a known manner.
With the usual mast design form, the bending moment generated by the lateral
wind pressure on the mast is absorbed by a shroud bracing outwardly spread by
(several)
spreaders and the resulting forces are introduced through the shroud into the
hull of the
boat on the windward side.
Both the spreaders and the mast absorb the load created by the wind forces and
the
prestressing forces on the rigging and the stays. For aerodynamic and weight
reasons, the
mast and the spreaders should be maintained as slender or thin as possible.
However, in
order to avoid buckling, the technical thinness of the design is limited, so
that the mast is
in the usual construction form provided with a wide profile and a high weight
for
resistance to buckling, and by being placed in front of the sail, it is held
with the luff in a
mast rail, which has a negative influence on the incoming flow of the wind
relative to the
course of the boat on the wind. When airflow enters the sail, the flow is cut
off and
vortices are generated on the air side and on the downwind side in the area
behind the
mast.
The flow-related technical problem is known and attempts were made to solve it
in
various manners. This problem is solved in WO/03889 by an arrangement of
additional
profiles or a pair of special vanes arranged next to the mast, wherein this
solution of the
problem deals with the disadvantage of additional load, which increases the
heeling
moment.
In patents FR 1 524 392 A, US 3 724 412 A, GB 1 399 421 A and FR 2 751 609
Al, the static advantage is disregarded and a higher weight or a smaller
bending resistance
of the construction are considered acceptable.
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The object of the invention is therefore to improve the statics through the
design of
a mast in the manner described above, while positive flow characteristics are
also taken
into account.
With the mast design according to the present invention, the forces resulting
from
the wind pressure and from prestressing are transmitted through the arc shape
or through
the straight design of the mast halves in the form of pressure forces, and in
the form of
traction forces through spokes and through a centrally deployed stay.
Due to the ratios between the forces on which the construction of the
invention is
based, a ratio to the number of the employed spokes and to the frequency of
subdividing is
created for both mast halves which significantly reduces the propensity of the
mast halves
to buckling, which in turn results in a significantly thinner design of the
two profile halves
of the mast.
The resistance torque of the mast perpendicular to the wind direction must be
considered to be significantly higher due to the width of the construction
with the
construction design according to the invention.
Moreover, the static advantage of the construction according to the invention
is the
result of the significantly more resilient spokes relative to their thin
design which is
exposed to the tensile forces, as well as based on the abundance of the
arrangement of the
spokes, or on a better distribution of the forces throughout the entire length
of the mast
halves. The construction in accordance with the invention thus results in a
higher stability
of the mast relative to its weight.
In one variant of the construction according to the invention, the mast halves
run
straight or partially straight, and the tendency to buckling in a certain
direction is due in
this case to the asymmetric (inner) material stresses related to the profile,
in each case in
the direction of the convex side of the (open, semi-circular) profile of the
mast halves,
wherein buckling can be avoided with an appropriate arrangement of the spokes
or of the
pressure elements, in relation to their frequency.
Direct air flow to the sail is thus made possible because of the arrangement
of the
sail centrally between the mast halves.
In contrast to Utility Model G 92 07 461.8, the bifurcation of the mast is not
used
based on the present concept to increase the sail area by implementing the
beam through
the sail, but instead it is used to increase the stability of the mast itself.
The present
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construction thus enables static redirection very effectively, even with
extremely high
wind pressures.
The resulting aerodynamic advantage is obtained from the direct airflow to the
sail,
as described in a similar form in patents FR 1 524 392 A, US 3 724 412 A, GB 1
399 421
A and FR 2 751 609 A. In addition, the more slender design of both profile
halves of the
mast also makes it possible to attain a corresponding execution of the vane
profiles which
is more streamlined, so that a better airflow can be achieved to the main sail
with the
course on the wind. The airflow can be further improved when the construction
is realized
as a rotatable construction.
The spokes deployed on the inner side do not result thanks to the small, round
or
flat elliptical profile in any significant vortexes or air resistance values.
The sail can be raised on the central stay, or with lighter forms (small
dinghies)
hooked into the spokes along the length of the luff of the sail, but it can be
also freely
extended between the mast and the mast base (construction without a central
stay).
The introduction of the lateral wind forces in the hull of the boat takes
place either
directly via the mast base mounted on the deck, or additionally also through
the shrouds,
which can act in its turn deep at the height of center of gravity at the inner
stay the sail,
resulting in a further weight loss of the entire rigging and in a not
insignificant lowering of
the center of gravity of the mast and of the rigging.
Furthermore, control over Genoa sail is facilitated with the more slender
construction form of the spread mast and the deeper deployment of the
spreaders.
As shown in the diagram of Fig. 1, a boat is indicated in front view, which
comprises the construction form of the mast according to the invention
provided with two
mast halves 1 and with the inner stay 2, which is connected through frictional
force with
the arc ends (4) and with the mast base 5, and which tensions the curved mast
halves
vertically in the longitudinal axis. The spokes 3 provide for the bracing of
the mast halves
to each other, transversely and obliquely to the longitudinal axis. Optional
shrouds 6
additionally conduct the generated forces into the boat body 7. Fig. 2 and
Fig. 3 represent
the profile forms 8 and 9 of the mast halves in a cross-section normal to the
longitudinal
axis of the mast.
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