The invention concerns a design of a mast for a sailboat, wherein the mainsail's mast rope is inserted into a hollow profile on the outside of the mast.

In most existing mast designs the position of the mast profile in front of the plane of the sail causes turbulence or the creation of a back eddy over the sail's lee side. Wing sail rigs with a rotating mast have almost no turbulence, since their aerodynamic design is very good, but this rig is only suitable for multi-hull boats. The field of turbulence is extremely wide and extends over the entire height of the sail, and turbulence in this area results in very poor tractive power for this part of the sail. The aerodynamic conditions are highly unsatisfactory.

The object of the invention is to improve these conditions and thereby provide increased power to the mainsail of a Bermuda-rigged sailboat.

This object is achieved with a device which is characterized by the features presented in the patent claims.

By means of the solution according to the invention an aerodynamic design is obtained which is close to ideal. The field of turbulence is completely eliminated and the construction provides full tractive power over the sail, and in addition tractive power over the actual mast construction up to the foremost point on the mast. The construction approaches the most ideal aerodynamic design, the bird's wing shape.

The construction consists of a round mast tube about which an aerodynamically shaped profile can rotate within a sector of 180 degrees, and inside which are various fastening alternatives for the mainsail, in which roller reefing on the inside of the profile is a possibility. This is a further advantage which is achieved with the special design according to the invention.

The invention will now be described in more detail by means of an embodiment which is illustrated in the drawing:

Fig. 1 is a side view of the uppermost part of a mast designed according to the invention, fig. 2 is a detail drawing of the top of the mast viewed from in front, fig. 3 is a side view of the lower part of the mast,

fig. 4 is a view from in front of the mast with a fastening device for shroud and horns of the crosstrees, fig. 5 is the mast viewed from above in a section A-A in fig. 1 , fig. 6 is a cross section through mast and profile at the intersecting line A-A in fig. 1 , and fig. 7 is a cross section along line D-D in fig. 3 through boom and mast/profile.

The mast design is illustrated in the drawing where fig. 1 shows a side view of the mast's 1 uppermost part down to and including the fastening device for shroud and horns of the crosstrees. The horns of the crosstrees are only shown as a cross section where they are situated in the centre of the bracket. The uppermost part of the profile is illustrated in a "transparent" manner, the roller stay and the attachment of the sail being visible, since this version of the profile is designed internally for a roller mainsail.

Fig. 2 illustrates the top of the mast viewed from in front. The top shrouds are attached to a transverse beam in order to provide space for the rotation of the profile.

Fig. 3 illustrates a side view of the lower part of the mast from the neck of the sail down to the attachment on deck. Details will be presented in the following description.

Fig. 4 is a view from in front on an enlarged scale of the fastening device 24 for shroud and horns of the crosstrees 23.

Fig. 5 illustrates the mast on an enlarged scale viewed from above, from a section through A-A in fig. 1. The ring with which the profile is attached is not included, nor is the inside of the profile. Through the horns of the crosstrees 23, which are made in one piece, can be seen the stippled attachment bracket 24 to which the horns of the crosstrees 23 are screwed. On the underside on each side the bottom shrouds can be seen. The profile has been swivelled out the maximum distance to the port side, and the turning sector and the profile's position to starboard are illustrated as dotted lines.

The detailed description of the invention is based on fig. 6. The same reference numbers are used in all the figures.

Fig. 6 shows an enlarged cross section of mast 1 and profile 2 through the intersecting line A-A in fig. 1. Here a possible design is shown of the interior of the profile intended for use as a roller reefing application. The cross section of the profile

2 has a substantially triangular external shape, where the longest sides 4 are of equal length and slightly convex. The third side 5 is extremely concave corresponding to a sector of a circle, adapted to be permanently mounted on a tubular section, a ring 13. The two longest sides 4 are not connected to each other in the corner between them, but are terminated smoothly and roundedly directly above each other, leaving a slot opening 6, through which the roller sail passes.

On the inside of the profile, some distance from the slot 6, three wall pieces 7,8 and 10 extend from the long sides. The first two form a defined space or a channel with a slot 9 through which an extra mainsail can be mounted. A halyard A for hoisting this sail runs in the channel. The walls have smooth surfaces and the slot openings are rounded to permit the sail and the mounting blocks for the extra mainsail to slide easily without becoming worn. The walls 8 and 10 also serve as a rear demarcation of the space for the roller stay 3, and prevent it from being pulled backwards by the traction in the sail when loaded by wind.

The space for the roller stay 3 is defined in front by a semicircular wall 11 , which connects the long sides 4 with each other. This wall touches and is "merged" with the concave end wall 5 in the triangle. On each side there is thus formed a new channel 12 defined by the partition wall against the roller stay space 11 , the front part of the long side 4 and half of the concave end wall in the triangle. On one side of these channels halyard A runs to the extra mainsail hoisted on blocks in the slot 9 and on the opposite side halyard B runs to the roller mainsail which is hoisted on stay 3. Inside the ring 13, whose interior is lined with a hard-wearing sliding coating, can be seen the cross section of the mast 1. Inside the mast, not shown, runs the boom tricing line, two jib halyards and a spinnaker halyard, in addition to cables for instruments, lanterns, antennas, etc.

The profile is mounted on a base, see fig. 3, reference number 14, which is mounted against the mast 1 with bearings which absorb both radial and axial forces. Immediately above the base the halyard A for the extra mainsail exits. The halyard B for the roller mainsail exits on the opposite side.

In order for the profile to work, line connections between profile and cockpit must be slack when under sail. Thus full handling of the sails from the cockpit is dependent on a remotely controlled line brake 17 developed for the mast design, and a roller drive gear with stop 15, also remotely controlled.

From the boom comes the sail tricing line 18, passes through a line brake 17, and continues to the cockpit. From the roller drive gear 15 a peripheral line 16 runs to the cockpit. The roller drive gear is equipped with a stop, and from the stop arm a line 21 goes down to the line brake. The stop arm is actuated from the line brake as a step two in operating this line brake which is operated by line 19 which goes to the cockpit.

From the neck of the sail and downwards the rearmost part of the profile's lateral surfaces is cut away into the partition wall against the roller stay space, except for a section 20 between the sail's neck and the boom attachment where the channel for the extra mainsail is kept. From the boom attachment and downwards, the cutting surface and the partition wall with opening are hidden behind a strip which is folded over the corners and attached to the sides of the profile. The roller drive gear 15 is attached to and through this strip.

A version of the profile for a traditional mainsail only, or a mainsail which can be rolled down into the boom, is not illustrated in the drawings, but the cross section of this version of the profile is the same as that shown, apart from the internal design.

The profile has to be capable of being trimmed to the correct position during sailing. The correct angling of the profile in relation to the sail can be achieved by means of several alternative trimming solutions.

A simple method of trimming the profile can be achieved by using an adjustable angle limiter on the joint between the boom and the profile. See fig. 3, reference number 22, and fig. 7 which show the boom and mast/profile as a cross section through D-D in fig. 3, viewed from above. Here the profile has been swivelled out to the side until the angle limiter 22 stops the swing. The joint must be in the direction of the boom where the angle between joint and boom must be of such a size that the tractive power from the joint results in a backwardly directed force component through the boom which is less than the forces which cause angling of the profile. The angle limiter is adjusted by means of turnbuckles to an angular swing which is suited to the depth of the sail. This adjustment is then suitable for all wind directions and joint lengths, but should be adjusted when the depth of the sail is altered. After the profile has reached maximum rotation to the side, longer joint lemβtns will lead to an increasing deviation between the sail's plane and the profile's plane. This occurs, however, with wind directions where the pressure of the wind against the sail's windward side constitutes the dominant driving force for the boat.