Ships – Watercraft with means used in providing sailpower – Having specifically defined hull shape
Patent
1983-06-13
1985-10-01
Blix, Trygve M.
Ships
Watercraft with means used in providing sailpower
Having specifically defined hull shape
114102, 114 97, B63H 904
Patent
active
045438994
DESCRIPTION:
BRIEF SUMMARY
This invention relates to sails for marine or terrestrial vessels, and especially to self-trimming sailsets.
A known type of self-trimming sailset consists of a principal sail that is rotatable about an erect axis and an auxiliary sail or "tail vane" that is carried downstream of the principal sail. This tail vane is mounted on a boom that extends from the principal sail so that thrust on the tail vane rotates the tail vane and boom about the erect axis and causes rotation of the principal sail. In operation, the angle of the tail vane, with respect to the principal sail, is set, the resulting thrust of the wind on the tail vane urging the tail vane and boom towards the position of minimum drag for the tail vane and thus causing rotation of the principal sail to an angle of attack predetermined by the setting of the tail vane.
These self-trimming sailsets have advantages over conventional sailing rigs in terms of controllability, efficiency and drive, but tend to suffer from relatively poor downwind performance due to the inability of the tail vane to stall fully the principal sail.
The present invention is directed towards alleviating the aforesaid disadvantage of self-trimming sailsets.
According to one aspect of the invention there is provided a self-trimming sailset including an auxiliary vane capable of being positioned forwards (i.e. usually upwind) of the leading edge of the principal sail and such that thrust on the auxiliary vane causes rotation of the principal sail.
Another aspect of the invention provides a self-trimming sailset including at least one auxiliary vane that is capable of opposing the moment of the principal sail about its own axis as the principal sail is moved towards a stalling position.
The auxiliary vane is preferably rigid, most preferably a rigid aerofoil of symmetrical section that is pivoted ahead of its centre of pressure.
The sailset preferably comprises counterbalancing weights which may be incorporated into the auxiliary vane or be carried by a boom on which the auxiliary vane is mounted.
The invention will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1 is a schematic plan view of a self-trimming sailset in accordance with an embodiment of the invention;
FIG. 2 is an enlarged schematic plan view of the auxiliary sails of the sailset of FIG. 1;
FIGS. 3 and 4 show, respectively, in schematic plan view, the configuration of the sailset of FIG. 1 adopted for port and starboard tacking;
FIGS. 5 and 6 show in schematic plan view the sailset of FIG. 1 in the configuration adopted for port and starboard stalling; and
FIG. 7 shows a side view of the sailset of FIG. 1.
Referring to FIG. 1, there is a principal sail 1, shown as a symmetrical section aerofoil, which is freely rotatable about an erect axis 2, and a tail vane 3 mounted on a boom 4 that extends from the principal sail 1. In addition to the tail vane 3 there is a second auxiliary vane that in non-stalling conditions is positioned upwind of the principal sail. This second auxiliary vane, referred to herein as forward vane 5, also extends on a boom 7 from the principal sail 1.
The axis 2 of the principal sail 1 is positioned on the chord of the aerofoil section at a distance from the leading edge of the aerofoil that is within the zone in which the centre of pressure of the aerofoil generally occurs in non-stalled modes of operation. This zone will generally lie in the range from 22% to 40% of the chord length measured from the leading edge. The tail vane 3 is also pivoted about an erect axis preferably within the zone in which its centre of pressure generally occurs. The forward vane 5 is freely pivoted about an erect axis 6 the location of which is upstream of the zone in which its centre of pressure generally occurs, preferably in the range of 0% to 18% of the chord length measured from the leading edge although the forward vane 5 may be pivoted about an axis disposed forwards of its leading edge.
FIG. 2 shows an enlarged view of the extremities of the booms 4 and 7 ca
REFERENCES:
patent: 3247821 (1966-04-01), Craig
patent: 3968765 (1976-07-01), Menegus
patent: 4124180 (1978-11-01), Wolowicz
Blix Trygve M.
Swinehart Edwin L.
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