Abstract:
A multihull vessel has a center section; a pair of floats displaceable from normal positions laterally extended on either side of the center section upwardly to positions above the center section and inwardly toward the center axis of the vessel as well as downwardly toward any hull or sides of the center section and inwardly to positions below any superstructure of the center section; arms consisting of pivotally mounted and jointed members connecting the floats to the center section and capable of positioning and maintaining the floats at positions between fully raised and fully lowered; one or more masts displaceable from a fully vertical position to a fully prone position; elements of standing rigging of effectively adjustable length between mast and center section or floats and apparatus for adjusting singly or in coordination, even while underway, moored or capsized, with inboard, in-place and centrally located control device, any of the floats or masts to any allowable orientation with respect to the center section. Operations possible with such a vessel include: unaided righting of the capsized vessel, reducing the beam to that of the center section for trailering or accommodating a narrower berth or passage, lowering the mast for stowage or for accommodating a berth or passage of restricted height, and changing the relative positions of aforementioned elements of structure or rigging for improvements in performance, safety or comfort in various sailing attitudes.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to multihull vessels having a central section, which may be a cabin or other superstructure with or without an attached hull, and a pair of hulls or floats (hereinafter referred to as floats) oppositely spaced from the center section on pivotally mounted and jointed arms or outriggers (hereinafter referred to as float arms). 
     In contrast to a self-righting monohull vessel which maintains stability by having its center of gravity arranged below its center of buoyancy, a multihull vessel provides buoyancy to oppose heeling in the form of divided hulls or outrigger floats. A monohull sailboat with ballasted keel has no righting moment at 0 degrees of heel where heeling moment is maximum, has maximum righting moment at 90 degrees of heel where heeling moment on the sailplan vanishes and is unstable at 180 degrees of heel. A multihull vessel has large initial stiffness or resistance to heeling due to the lateral displacement of the center of buoyancy, but the righting moment decreases as the angle of heel increases and as more of the bottom of the vessel is exposed to the forces of wind and waves and the vessel is more stable at 180 degrees of heel than at 0 degrees unless additional buoyancy is provided above the center of gravity of the upright vessel. Unless the beam of the vessel can be reduced, a very large righting moment is required, usually in the form of often unavailable external leverage to bring the vessel back past 90 degrees of heel. 
     Flooding of one float is often proposed to negate the stabilizing effect of its buoyancy in the capsized position, but the disadvantages of this method are obvious, both in its performance and in subsequent recovery in a situation of continued duress. Various schemes exist to use topside buoyancy in the form of an enlarged watertight cabin, in the form of masthead flotation or in various other forms of fixed or inflatable buoyancy on or above deck. Several applications are known in which the floats are retracted or folded to the sides or under the center section to reduce the beam, but such methods are usually only for such purposes as preparing the vessel for trailering or for a narrower berth. Such methods cannot usually be performed with any ease while underway and external leverage is still usually required for capsize recovery. At least a couple of applications have been proposed in which the floats can be pivoted upward against resistance provided by resilient means to allow heeling of the center section for the primary purpose of preventing capsize. Such methods make no provision for moving the floats sufficiently inboard to make a fully capsized vessel unstable and make no provision for adequate means to lift the center section of such a vessel by such positioning of the floats. 
     It is believed that all of the prior art adjustable float multihull vessels are wholly dependent on concepts absent from the present invention which limit their range of applications in each case to very few of the potential improvements in performance, safety and comfort possible as secondary benefits of the present invention. These prior art multihull vessels require float adjustability which is either too resilient or which can only assume a few rigidly supported positions, which must either be automatically actuated or which can not be sufficiently expeditiously effected and which do not have the range and types of adjustability nor the flexibility of interaction with other rigging elements to achieve more than a few capabilities of the present invention. 
     It is an object of the present invention to provide means for varying the positions of floats from their normal extended positions, laterally spaced from the center section to provide stability in normal sailing attitudes, to positions raised above the center section, i.e., beneath the center section when the vessel is fully capsized (the term &#34;beneath&#34; being used here in relation to the capsized vessel), which would render the vessel unstable in an inverted or capsized attitude, and also to positions lowered to the sides of or below the center section of the upright vessel, which would reduce the beam for various purposes such as trailering or accommodating a narrower berth. 
     It is another object of the invention to provide means for adjusting the floats to and maintaining them in various orientations with respect to the center section at all heights between the fully raised and the fully lowered positions, which means are contained inboard and in-place as permanent components of the structure and rigging, require no equipment to be attached to or detached from the floats or arms to effect the adjustments and require no releasable restraints and a minimum of fixed limits on the rotation around joints within the float arms. Applications in addition to those alluded to above for reducing the beam in the extreme positions include alterations in float height, distance from the hull and attitude for fine adjustments to the vessel&#39;s performance in different circumstances and for more fundamental adjustments of the vessel&#39;s performance characteristics such as lifting the main hull of a trimaran nearly clear of the water to gain any performance advantages of a catamaran or rotating the floats to bring planing or hydrofoil surfaces into operational positions. 
     It is a further object of the invention to make elements of the standing rigging adjustable such that the position of a mast may be varied from fully vertical to fully horizontal (possibly in either the fore or aft directions) and such that adjustments of the mast can be carried out in a variety of ways, independently of or in conjunction with adjustments of the floats. Beside independent lowering of the mast for stowage and raising of the mast from the stowed position, the applications include lowering the mast as the floats are raised in a capsize recovery for the purpose of pivoting shrouds out of the way of the floats, lowering the mast to the deck in a capsize recovery for the purpose of utilizing shrouds to lift the floats with motive force possibly being supplied by masthead flotation, causing the mast to be re-raised during capsize recovery by the re-lowering of the floats and leaving the mast stowed on the deck as floats are re-lowered during capsize recovery, with raising and lowering referring to the vessel in its upright position. 
     It is a further object of the invention to bring control of rigging or other equipment which effects and maintains the adjustment of floats and mast to a central location where this control can be readily and selectably exercised in a variety of combinations of possible operations by the crew while underway or even capsized. 
     It should be noted that in all of the following description terms such as &#34;up&#34; and &#34;down&#34; or &#34;raising&#34; and &#34;lowering&#34; will be assumed to be defined in terms of the upright vessel, unless otherwise noted, even when it is being considered to be upside down in the water. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a multihull vessel comprising a center section, which may be a cabin, platform or other superstructure with or without an attached center hull; a pair of floats oppositely spaced from the center section; a plurality of float arms consisting of segments, arranged in fore and aft float arm assemblies for each float and pivotally connected at their ends to the center section, to the floats or to other float arm segments or fixedly attached at their ends or along their lengths to the floats or to other float arm segments; rigging connecting float arm segments which is fixedly attached at one end within the float arm assemblies and which is led via pulleys or other guides within float arm assemblies and the center section to means for controlling this rigging from a central location; at least one mast, normally connected pivotally to the center section; elements of standing rigging which can be effectively adjusted in length by leading the termination of this rigging or, optionally, of additional rigging, attached to or riding via pulleys on the standing rigging for the purposes of collapsing triangles formed by the standing rigging and masts, to means for controlling this rigging from a central location within the center section and finally, controls in a central location and which can be used to independently or simultaneously in various selectable combinations adjust the length of rigging which can vary the positions of either or both floats and the mast by any desired amount from those which may be described as fully raised to those which may be described as fully lowered. 
     A particular embodiment of the invention is a sailing trimaran (having a central hull) with float arm assemblies jointed twice in upper arms and pivoting at either end and jointed once in lower arms and pivoting at the inboard ends and with a single mast pivoting near the deck. This embodiment will now be described, by way of an example, along with various alternative or optional features and extensions of the basic structure, with reference to the accompanying drawings, wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a trimaran according to the invention at the ordinate of either the fore or aft float arm assemblies with the floats in the normal extended positions; 
     FIG. 2 is a cross-sectional view similar to FIG. 1 but with the floats raised upwardly and inwardly over the deck; 
     FIG. 3 is a cross-sectional view similar to FIG. 1 but with the floats lowered under the deck superstructure and inwardly to the sides of the center hull; 
     FIG. 4 shows in cross-sectional outline, except for the representation of the mainsail, a trimaran with fixed extended floats at a high degree of heel; 
     FIG. 5 shows in cross-sectional outline, a capsized trimaran with fixed or extended floats; 
     FIG. 6 shows in cross-sectional outline of a simplified representation of a trimaran with floats folded above the deck a sequence of stages in the righting of the capsized vessel; 
     FIG. 7 is a cross-sectional view of one float arm assembly and internal rigging for controlling the positions of the float; 
     FIG. 8 is a cross-sectional view of one float arm assembly and another embodiment of the internal rigging for controlling the positions of the float; 
     FIG. 9 is a perspective view of the pair of port float arm assemblies, an embodiment of one type of float position adjusting rigging with inboard means for controlling this rigging collectively for each float arm assembly and diagonal braces or stays between the port side of the superstructure of the center section and the deck of the port float, which are illustrated with dotted lines; 
     FIGS. 10, 11, 12 and 13 are fragmentary perspective views of alternate embodiments of float position adjusting rigging; 
     FIG. 14 shows in cross-sectional outline a trimaran according to the invention in a capsized position with floats raised with respect to the upright vessel downwardly and inwardly beneath the deck of the capsized vessel as far as taut main hull shrouds from a fully raised mast will permit; 
     FIG. 15 is a simplified and somewhat schematic perspective view of the center hull of a trimaran according to the invention with the mast partially lowered pivotally by means of adjusting the length of fore and aft mast stays; 
     FIG. 16 is a simplified perspective view similar to FIG. 15 illustrating means in the form of triangular frames pivoting along their base on the main hull for purposes of extending the leverage on the mast applied by the fore and aft stays above the deck or beyond the length of the main hull; 
     FIG. 17 shows in similar perspective view alternate means for effectively shortening the length of one of the mast stays; 
     FIG. 18 shows in perspective view from above a simplified representation of a trimaran according to the invention in which lowering of the mast is being used to effect the lifting of the floats by means of tensional force applied through float shrouds; 
     FIG. 19 shows in cross-sectional outline of a trimaran according to the invention the inward force on the floats due to tension on float shrouds after the mast has been lowered and the floats raised beyond the point at which the float shrouds would lie in a horizontal plane; and 
     FIG. 20 shows in a simplified, somewhat schematic perspective view of a trimaran according to the invention means for adjusting the length and effective point of connection on the floats of the float shrouds. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiments of the invention illustrated and described below all relate to but are not limited to sailing trimarans and FIG. 1 shows in cross-sectional outline a trimaran according to the invention with floats extended in normal sailing positions. The vessel comprises a center section or center hull 1 to which floats 2 and 3 are attached by float arm assemblies 4 and 5, a mast 6, center hull shrouds 7 between the mast and center hull and float shrouds 8 between the mast and floats. The mast 6 and shrouds 7 and 8 may be broadly described as comprising part of a standing rigging which may also include conventional stays, etc. The upper float arms 9 and the lower float arms 10, consist of float arm segments 11, 12 and 13 for the upper arms 9 and of float arm segments 14 and 15 for the lower arms 10, respectively. Segments 11, 12 and 13 of the upper arms 9 are pivotally connected to the center hull 1, internally in two joints and at the floats 3 and 4 pivots 16, 17, 18 and 19. Segments 14 and 15 of the lower arms 10 are pivotally connected to the center hull 1 and to each other at pivots 20 and 21 and fixedly to the floats 2 and 3. The segments and pivots are listed in order of increasing distance from the vessel&#39;s longitudinal axis through the center of gravity 22 and may be referred to unambiguously with such names as upper float arm middle arm segment 12 and upper arm inboard internal pivot 17, for example. 
     The float arm geometry illustrated in FIG. 1 is one embodiment of configuration of outriggers which has the capability of being used to both raise and lower the floats to a range of desired heights and lateral distances from the center hull. In the laterally extended position for this double arm configuration both the upper arms 9 and the lower arms 10 are understood to be fully straight. 
     As noted earlier, in all of the following descriptive terms such as &#34;up&#34; and &#34;down&#34; or &#34;raising&#34; and &#34;lowering&#34; will be assumed to be defined in terms of the upright vessel, unless otherwise noted, even when reference is being made to a vessel upside-down in the water. 
     FIG. 2 illustrates in cross-sectional outline the relative positions of the float arm segments 11, 12, 13, 14 and 15 when the floats 2 and 3 have been pivotally raised near to their extreme positions over the middle of the center hull 1 against the mast 6. The only internal float arm pivots required for raising floats 2 and 3 in this manner are the upper arm outboard internal pivots 18. The shrouds 7 and 8 have been left out of this illustration. 
     FIG. 3 illustrates in cross-sectional outline the relative positions of float arm segments 11, 12, 13, 14 and 15 when the floats 2 and 3 have been pivotally lowered toward the sides of the center hull 1 with the outboard float arm segments 12, 13 and 15 in substantially vertical orientations. Upper arm outboard float arm pivots 18 are not required for lowering the floats 2 and 3 in this manner. The shrouds 7 and 8 are not shown in this illustration. 
     FIG. 4 shows in cross-sectional outline, except for the representation of the mainsail, a trimaran with fully extended floats 2 and 3 at a high angle of heel caused by the force of the wind on the mainsail 23 and the center hull 1. The wind is represented by force vectors F and F&#39; on these respective centers at respective heights h and h&#39; above the shifted center of buoyancy. The resultant wind forces F and F&#39; are proportional to the effective vertical projections of the exposed areas of sailplan and undersurface, respectively. The gravity force vector M and the buoyant force vector B, applied at the respective centers of gravity and buoyancy, are displaced laterally from each other by the moment arm for righting l and are equal in magnitude at equilibrium. As the angle of heel increases beyond that angle at which only the windward float 2 comes out of the water, the displacement l decreases and the effective vertical projection of the vessel&#39;s exposed undersurface increases even as the vertical projection of sail area decreases. If the strength of the wind increases sufficiently, the heeling moment Fh+F&#39;h&#39; will exceed the righting moment Ml and the heeling moment will increase further as the angle of heel increases to 90 degrees and the righting moment decreases to zero. If the center of gravity becomes displaced to the leeward side of the center of buoyancy, the vessel will heel further by itself and will not reach a stable equilibrium again until it has capsized to 180 degrees of heel. 
     FIG. 5 shows in cross-sectional outline a trimaran with floats extended in the fully capsized position and illustrates that the vessel is intrinsically more stable upside down than rightside up. 
     FIG. 6 shows in cross-sectional outline of a simplified representation of a trimaran with floats 2 and 3 folded above the deck a sequence of stages in the righting of the capsized vessel. In the figure the center of gravity or mass 22 is represented by a solid dot • and the center of buoyancy 24 is represented by an open dot  . In the first stage of recovery the floats 2 and 3 are being &#34;raised&#34; above the deck of the center hull 1 thus placing the center of buoyancy 24 lower in the water than the center of gravity 22 of the capsized vessel. The situation shown with unbalanced forces of gravity M and buoyancy B could only occur if the floats 2 and 3 are placed above the deck faster than the vessel can be lifted in the water to make the volume of water displaced decrease until its weight equals that of the vessel. The center hull 1 would be lifted clear of the water in metastable upside-down equilibrium if the buoyancy of each float 2 and 3 fully submerged is greater than one-half the total displacement of the vessel. The righting sequence is possible with floats 2 and 3 of substantially less buoyancy as long as the center of buoyancy 24 can be positioned lower in the water than the center of gravity 22 of the capsized vessel. 
     In the second stage of recovery the center of gravity 22 is shifting away from the center of buoyancy 24 in the direction of roll, even though the center of buoyancy 24 is also shifting in that direction, as the vessel rolls away from the fully inverted position in which the center of gravity 22 was directly above the center of buoyancy 24. Little or no external leverage will be required to continue this roll away from an upside down position of unstable equilibrium if the floats are fully submerged in this position. The closer that the floats 2 and 3 can be positioned toward the center of the vessel and and the mast 6, if the floats are too buoyant to be fully submerged, the less external leverage would be required from the action of wind and waves to push the center of gravity 22 outboard of the separate centers of buoyancy of the floats 2 and 3 in the metastable equilibrium which would result from the center hull 1 being lifted completely out of the water. Furthermore, the higher the center hull 1 can be lifted out of the water, the more leverage can be supplied by wind and waves to roll the vessel past the region of metastable equilibrium. 
     In the third stage of capsized recovery the vessel is continuing its roll towards another metastable equilibrium on its side. The vessel could be left in this position for some time after capsize recovery since a relatively small vertical area is exposed to the wind. A very strong gust of wind might flip the vessel to the similar position on its lee side where it would likely remain until fully righted. In the final stage of recovery the vessel is brought to the fully righted position merely by bringing the floats 2 and 3 back to their laterally extended positions. 
     It will be noted that little or no buoyancy is required for the center section, which need not even be a hull, in order for this method to be implemented. 
     FIG. 7 is a cross-sectional view of one float arm assembly 5--either the fore or aft assembly--illustrating the simplest configuration of rigging which could be used with the float arm geometry shown in FIG. 1 to maintain the height of the float 3 at any position between the extremes represented in FIG. 2 and FIG. 3. Two types of rigging, float fold-down rigging 25 and float return-down rigging 26, are used to maintain all three internal joints under balanced opposing forces, both types of rigging terminating at points within the float arm assembly 5, spanning the space between the float arms 9 and 10 in one or more places and being led through pulleys or around shafts or sleeves to the center hull. In the illustrated embodiment the float fold-down rigging line 25 terminates at a point of connection 27 in the upper float arm 9, is led around a tension directing pulley or sleeve 28 concentric with the lower arm internal pivot 21 and thence around a tension directing pulley or sleeve 29 concentric with the inboard upper arm end pivot 16 and is brought inboard to suitable means for controlling its length. In a similar fashion the float return-down rigging line 26 terminates at a point of connection 30 in the upper float arm 9, is led around a tension directing pulley or sleeve 31 in the outboard lower float arm segment 15 and thence over tension directing pulley or sleeve 28 concentric with the lower arm internal pivot 21 and under tension directing pulley or sleeve 32 concentric with the inboard lower arm end pivot 20 to suitable means for controlling its length. 
     The float fold-down rigging line 25 is shortened to lower the float 3 toward the hull 1 and is principally used to control the height of the float 3 below the normal laterally extended position while the float return-down rigging line 26 requires little or no adjustment in length for changes in float height below its laterally extended position if the position of the point of connection 30 is calculated properly for the given float arm geometry. The float return-down rigging 26 is lengthened when the float 3 is raised above the deck of the center hull 1 and is shortened to lower the float again to its normal laterally extended position. This rigging is used principally to control the height of the float 3 above its laterally extended position while the float fold-down rigging 25 requires little or no adjustment in length as changes in float height above its laterally extended position are being carried out if the position of the point of connection 27 is calculated properly for the given float arm geometry. The float control rigging not principally adjusted in the two instances of float height adjustment above and below the lateral positions, respectively, can be adjusted for secondary corrections to the angles between float arm segments at the pivots not involved in each instance. The simple embodiment of these two types of float arm control rigging, 25 and 26, probably can not be designed to provide sufficient leverage, however, to raise the float 3, at least above the laterally extended position, and some other means must be provided to lift the floats in operational circumstances. Additional optional rigging internal to the float arm configuration 5 could be designed to raise the float 3 from a position below the laterally extended position as well as from the laterally extended position, but the preferred embodiments of the invention will employ rigging for raising the floats which is part of the float shroud 8 and which will be described below. 
     While sufficient upward force is being maintained on the float 3 either by the float shround 8 or by the buoyant force of the water, the simple arrangement of float-arm control rigging 25 and 26 can maintain the integrity of the float arm configuration 5 at any desired float height with the desired angles between the float arm segments at internal pivots 17, 18 and 21 and with no other constraint on the arc through which any pivot can rotate other than not allowing the inner upper arm segment 11 to swing any lower than its designed orientation in the laterally extended position of the float arm configuration 5. If back-buckling of upper arm pivot 18 against the lower arm segment 15 is to be avoided, pivot 18 could be prevented from forming a line with pivots 17 and 19 except in the fully folded-down position of the float 3 by adjustment of the return-down rigging 26; the arm segment 13 could be physically restricted from rotating counter-clockwise at pivot 18 above the line formed with arm segment 12 or, alternatively, the foot of the adjustable float shroud 8 could be located on one of the outboard float arm segments 12 or 13. 
     If the inboard internal upper arm pivots 17 and the internal lower arm pivots 21 are not provided, the floats 2 and 3 cannot be lowered below their extended position and the float fold-down rigging 25 would not be required. The same rigging could, however, be used for lifting the floats if these pivots are either not provided or the arm segments are temporarily physically restrained from rotating around these pivots. Similarly, if pivots 18 are not provided, the floats 2 and 3 cannot be raised for above the extended position and the float return-down rigging 26 would not be required. The same rigging could be used in this instance however to re-raise the folded floats 2 and 3 back to the laterally extended position. 
     Referring now to FIG. 8 auxiliary tension directing pulleys 33, 34, 35, 36, 37, 38 and 39 may be introduced along the lengths of the various float arm segments 11, 12, 13, 14 and 15 in addition to the single such pulley 31 in FIG. 7. Tension directing pulley or sleeve 40 may be introduced concentric with the upper arm outer internal pivot 18 in addition to those in FIG. 7 concentric with pivots 16, 20 and 21. The points of connection 27 and 30 of FIG. 7 may be moved to any points 27a and 30a outboard of all the tension directing pulleys. In the embodiment illustrated in FIG. 8 the float fold-down rigging 25 is led from the terminal point 27a in the upper arm over pulley 33, under pulley or sleeve 40 at upper arm outer internal pivot 18, over pulleys 34 and 35 in the internal upper arm segment 12, under pulley or sleeve 28 at lower arm internal pivot 21, over pulley 36 in upper arm segment 11 and over pulley 29 at upper arm inboard pivot 16 to suitable means for controlling its length. Similarly float return-down rigging 26 is led from terminal point 30a in the lower float arm under pulley 37 in the lower arm outboard segment 15, over pulley or sleeve 40 at pivot 18 in the upper arm under pulleys 31 and 38 in lower arm outboard segment 15, over pulley or sleeve 28 at lower arm internal pivot 21, under pulley 39 in the lower arm inboard segment 14 and under pulley or sleeve 32 at lower arm inboard pivot 20 to suitable means for controlling its length. 
     Tension directing pulleys 33 and 34 on either side of pulley or sleeve 40 at pivot 18 and tension directing pulleys 38 and 39 on either side of pulley or sleeve 28 at pivot 21 can be used to increase the opposing perpendicular forces at these joints. The positions of all of the auxiliary tension directing pulleys 31 and 33 through 39 can be calculated according to known methods of analysis for designed float arm geometry or can be experimentally adjusted to provide a balance of forces at all internal float arm pivots 17, 18 and 21 which will maintain the desired relative orientations of all float arm segments 11 through 15 within close limits throughout the range of float heights. Furthermore, sufficient force can be applied with the float arm control rigging 25 and 26 at the internal pivots 17, 18 and 21 to raise the float 3 without additional rigging (internal or external to the float arm configuration 5) when some or all of these auxiliary tension directing pulleys are properly located. The physical constraint on rotation of the inner upper arm segment 11 may even be removed by positioning either auxiliary pulley 35 or 36 on the opposite side of upper arm inner internal pivot 17 from that at which it is depicted in FIG. 8. 
     The optimum positioning of auxiliary tension directing pulleys 33 through 39 will minimize the amount of tension required on each of the two rigging lines 25 and 26 to maintain the float 3 at any desired position. It will also minimize the amount the secondary line (25 or 26) must be adjusted to fine-tune the angles between the arm segments at internal joints 17,18 and 19 after a larger adjustment of the primary line (26 or 25) is made to change float height above and below the laterally extended position, respectively, as described above for the configuration in FIG. 7. It will further minimize the amount that joints 16 through 21 will &#34;work&#34; or flex to readjust to varying forces on the float 3. In practice not all of the auxiliary pulleys 33 through 39 might prove necessary to satisfy all the foregoing requirements within acceptable limits. 
     In principle, float shrouds 8 would not be required for the configuration of float arm rigging in FIG. 8 either to maintain the integrity of the float arm assembly 5 at a given float arm height or to assist in the raising of the float 3 as mentioned for FIG. 7 and described below. Float shrouds, if used, would have to be lengthened or repositioned in some way to allow lowering of the floats below the extended positions. Without the float shroud 8 under tension to stiffen the disposition of float arm assembly 5, the joints 16 through 21 should flex or &#34;work&#34; slightly to readjust the angles between arm segments 11 through 15 in response to varying bouyant forces on the float 3. This flexibility of the float arm assembly 5 could be exploited as a load equalizer or shock absorber to produce a more comfortable, even safer ride in choppy seas. It should be noted that if the float shroud 8 is held under tension, it will slacken as the bouyant forces are increased and an almost constant upward force on the float and, therefore, a fixed set of angles between the float arm segments 11 through 15 will be maintained up to the point at which the bouyant forces equal the float shroud tension. 
     FIG. 9 is a perspective, somewhat schematic view of the pair of port float arm assemblies 5, illustrating the embodiment of FIG. 7 of the float fold-down rigging 25 for these arms, one particular embodiment of a system for common adjustment and control of all four float fold-down rigging lines and illustrating diagonal stays 41 between the float 3 and the center section 1. The diagonal float stays 41 are pivotally mounted at pivots 42 located in the center section superstructure 43 on a common longitudinal axis with lower float arm inboard pivots 20 and are fixedly mounted at points 44 on or near the deck of float 3, the superstructure 43 and the deck of float 3 being shown in dotted outline. 
     The diagonal float stays 41 are located in a substantially horizontal plane under tension when the float 3 is in its normal laterally extended position with the lower arms 10 in an essentially straight orientation. The stays 41 will remain under tension at an oblique angle to a vertical transverse plane as float height is changed without altering the angle between lower float arm segments 14 and 15 at pivots 21 and will remain in an essentially common plane with lower float arms 10 in such a circumstance to provide resistance to fore and aft bending of float arm assemblies 5. If lower float arm joints 21 are buckled at least slightly downward and if upper float arm joints 18 are buckled at least slightly upward with float fold-down rigging lines 25, float return-down lines 26 and diagonal stays 41 all under tension and all of fixed length, rigid float arm assemblies 5 can be maintained with no rotation of float arm segments around any pivots. This rigid package of float arm assemblies 5 could even be maintained in some circumstances without tension on float fold-down rigging lines 25 if float shrouds 8 are maintained under tension or if upward (bouyant) force is applied to the float 3. If lower float arm joints 21 are buckled slightly downward as just described, with diagonal stays 41 under tension, the float 3 could be raised by shortening float fold-down rigging 25 while allowing float return-down rigging 26 to lengthen if auxiliary pulleys 33, 34, 35 and 36 are appropriately positioned, as previously discussed for FIG. 8. Releasable or adjustable devices such as lever locking mechanisms or turnbuckles could be employed with diagonal float stays 41 to switch or adjust these stays between lengths at which the lower float arms 10 could pass through positions in which they are fully straight at joints 21 to positions at which they must remain buckled at joints 21. 
     The embodiment of one method for bringing control of float fold-down rigging 25 to a central location, as illustrated in FIG. 9, has the control rigging line brought from upper arm inboard pivots 16 via fixedly located tension redirecting pulleys 45 and block and tackle 46 with a common fall 47, all under the deck of superstructure 43, to a single winch 48, which could be in the cockpit. The float return-down rigging lines 26 could be handled with a similar arrangement of control means. In this example both fore float arm rigging lines 25 are brought to a common pulley in block and tackle 46 and are constrained to adjust in length by the same amount as are both aft float arm rigging lines 25. With this arrangement of the control block and tackle 46 fore and aft rigging lines 25 and hence joints 16 through 21 are fore and aft float arm assemblies 5 are permitted to adjust by different amounts in response to different forces on the fore and aft ends of the floats 3. Such tension balancing adjustments would occur in addition to those between the two types of float control rigging 25 and 26 within one float arm assembly 5. 
     An alternate arrangement of block and tackle 49 is illustrated schematically in FIG. 10 for common control of float arm rigging lines 25 or 26 in which both fore and after lines are constrained to adjust in length by equal amounts. The rigging lines for only one float are shown joined at a common point but the same lines from the other float could also be brought to this point using additional tension redirecting pulleys 45. Independent block and tackle arrangements 46 or 49 of the types shown in FIG. 9 and FIG. 10, respectively, could be employed separately for the starboard and port floats 2 and 3 using common or separate winches 48. It is certainly possible even to have separate block and tackle and/or winches for each of four rigging control lines of each type. 
     Separate, additional take-up rigging could be provided for each individual float control rigging line 25 or 26 which is brought to any of the arrangements by block and tackle 46 and 49 for controlling any type of float control rigging lines such as float fold-down rigging 25 or float return-down rigging 26 together for fore and aft float arm assemblies 4 or 5 and separately or together for starboard float arm assembly 4 and port float assembly 5. As illustrated in FIG. 11 these could consist of lines 50 from pulleys 51 riding on the control lines 25 or 26 between pairs of tension redirecting pulleys 45a, fixedly located on opposite sides of float control rigging lines 25 or 26 from pulleys 51, to winches 52, located on the same side of control rigging lines 25 or 26 as tension redirecting pulleys 45a. 
     Alternate auxiliary means for providing common control of fore and aft rigging lines of one type for one float independently are illustrated in FIG. 12 using take-up rigging of the type illustrated in FIG. 11. Only a section of float arm rigging lines 25 or 26 are shown leading to block and tackle of either of the types shown in FIGS. 9 and 10. 
     In this embodiment control lines 50 from take-up pulleys 51 riding on float arm rigging lines 25 and 26 between tension redirecting pulleys 45a fixedly mounted on opposite sides of the rigging lines 25 or 26 are controlled by a single winch 54. One control line 50 of fixed length terminates at pulley 53 around which the other control line 50 is led to the winch 54. This arrangement provides independent control of one float of the force-balancing type in which fore and aft float rigging control lines 25 or 26 are permitted to adjust in length by opposite amounts in response to different forces at the ends of the float 3. The adjustment provided by this arrangement is additional to that provided by any common float control block and tackle such as those illustrated in FIGS. 9 and 10. In this arrangement twice as much tensional force will be applied on one line 50 as on the other. Should this not provide an advantage, a second pulley could be provided for block 53 and the load on this line 50 could be divided by leading it around this additional pulley to a fixed termination. 
     Further alternate auxiliary means for providing common control of fore and aft rigging lines of one type for one float independently are illustrated in FIG. 13 using an arrangement similar to that illustrated in FIG. 12 except that the additional adjustment in length of float arm rigging lines 25 or 26 must of be of equal amount. Control lines 50 from each take-up pulley 51 are joined at a common point, one of these lines 50 being led around fixedly mounted tension redirecting pulley 45, and thence to a single winch 54 via a common fall 55. 
     In place of the single fall 50 or 55 leading to winch 54 in FIG. 12 or FIG. 13, a block and tackle arrangement could be inserted if additional mechanical advantage is desired. 
     Either or both auxiliary means for providing common control of fore and aft rigging lines for one float illustrated in FIGS. 12 and 13 could be used with either primary means for providing common control of fore and aft rigging lines illustrated in FIGS. 9 and 10 for floats 2 and 3 separately or commonly and could be provided in addition to means for individual rigging line control illustrated in FIG. 11 in any combination, but it is readily apparent that certain combinations offer no conceivable advantage. 
     Any of the block and tackle arrangements illustrated in FIGS. 9 through 13 for control of float arm rigging lines 25 or 26 could be located in the floats 2 and 3 with appropriate means for bringing the fall from such block and tackle arrangements to winches or mechanisms for controlling the winches at a central location. To bring float rigging lines 25 or 26 to these arrangements in the floats, fixed terminations 27, 27a, 30 or 30a could be replaced with auxiliary pulleys. 
     Means other than block and tackle and centrally located winches could be employed to control float arm rigging lines 25 or 26 from a central location. These could include electric-motor-driven winches anywhere inboard of the entry into the center section superstructure 43 of individual rigging lines 25 or 26 with appropriate electrical switches or controls at the central location or mechanical systems employing gears, shafts, chains and sprockets and cranks for operating such winches. 
     Means other than rigging lines and pulleys within the float arm assemblies 4 and 5 could be used to control the orientation of float arm segments 11 through 15. In particular, hydraulic pistons suitably mounted between pivoting terminations at points along the arms 9 and 10 and at points on or in the center section superstructure 43 or floats 2 and 3--either between segments in the same arm internal or external to the float arm assemblies 4 and 5, between segments in upper arms 9 and lower arms 10 internal to the float arm assemblies 4 and 5, between an arm segment and the center section or the floats or even between the center section and the floats--could be employed in suitable combination to perform any of the functions previously described in terms of float arm control rigging lines 25 and 26, replacing or supplementing such rigging. Hydraulic pistons could even be substituted for any of the float arm segments 11 through 15 and changes in the variable length of such segments could be effected for any purposes of controlling float height, float attitude or float displacement from the center section. Hydraulic fluid lines could be brought from these pistons into the center section 2 to hand-driven or electric-motor-driven pumps which could be operated from a central location to control the action of these pistons. 
     Various current or voltage regulating devices, servo-mechanisms or other electrical sensors, magnetic relays or other electrical switching circuits such as digital logic circuits could be employed to operate electrical winch motors, electrically-driven hydraulic pumps or electrically-driven geared devices to translate the position or movement of various levers or sensing devices into changes of float position or attitude in any of the modes or combinations described herein. Hydraulic switching circuits employing differential hydraulic valves activated by mechanical means such as levers or by such electrical systems could be designed according to known methods of analysis to control the action of any of the hydraulic pistons from one common, manually or electrically driven pump in any such selectable modes or combinations of float adjustment. 
     In this description of float arm assemblies 4 and 5 of the preferred and allternate embodiments of the present invention several assumptions would appear to have been made. In particular, the axes of all pivots and auxiliary pulleys within the float arm assemblies 4 and 5 are presented as being parallel to the longitudinal (fore and aft) axis of the center section 1. The float arm segments 11, 12 and 13 of upper float arms 9 and segments 14 and 15 of lower arms 10 may be assumed to have longitudinal (lengthwise) axes which are respectively collinear when the arms are &#34;straight&#34; in the normally laterally extended positions for sailing and which lie in vertical transverse planes. Internal float control riggings lines 25 and 26 may be assumed to lie in these same vertical planes. The axes of all pivots 16 through 21 and auxiliary pulleys and sleeves 28 and 31 through 40 are thus assumed to be perpendicular to these vertical planes and may also be assumed to intersect the longitudinal axes of the float arm segments 11 through 15. Virtually no constraint was assumed to limit the rotation of the arm segments around internal pivot axes from an angle of 0 degrees between the longitudinal axes of adjacent arm segments to an angle of 360 degrees between such segments due to the physical nature of the arm segments and the joints or due to interference from pulleys or rigging elements. Finally, the location of the various auxiliary pulleys 31 and 33 through 39 may be assumed to be fixed along the length of the float arms 9 and 10. 
     The implementation of preferred and alternate embodiments of this invention is not constrained by these assumptions. Float arm segments could be laterally displaced from each other and would thus not physically constrain the limits of rotation of adjacent arm segments around internal joint axes. Auxiliary pulleys could be displaced above, below or beside longitudinal axes of the float arm segments or outside of the float arm segments if necessary to produce tensional forces on float control rigging lines 25 and 26 between tension directing pulleys or sleeves within the float arm assemblies 4 and 5 which will achieve the balance of forces on the float arm segments 11 through 15 required to maintain the desired orientations of these segments or if necessary to locate the float control rigging elements where they will not interfere with desired rotation of float arm segments. The axes of float arm pivots 16 through 21 could be inclined slightly from the horizontal with the planes of the float arm assemblies 4 and 5 rotated through the same angle from their vertical planes to remain perpendicular to the pivot axes so that floats 2 and 3 would move fore or aft in a desired manner as float height is altered by rotating float arm segments 11 through 15 around these joints. Pivots 18 could be configured as hinges with axes displaced below the arm segments 12 and 13 so that these segments could be folded against each other in the extreme raised position of the floats 2 and 3. One or more float arm segments 11 through 15 in each float arm assembly 4 and 5 could be a U beam into which adjacent arm segments could recess and thus rotate through angles from 180 degrees (straight) to 360 degrees (fully folded) with respect to the U beam segments. Such U-beam shaped segments could be extended past the joints with adjacent arm segments to limit these segments from rotating to angles of less than 180 degrees (back buckling) with respect to the U beam segments. Finally, any of the auxiliary pulleys 31 and 33 through 39 could be mounted in assemblies which move in or along the arm segments on sliding tracks or which pivot to alter their displacement above or below the longitudinal axes of the float arm segments along which they reside. Such assemblies could be locked temporarily in place by manually operated means and, in the absence of such locking mechanisms or with such locking mechanism released, these assemblies could be provided with resilient means which would allow the assemblies to move in response to varying forces and thus to contribute to maintaining desired orientations and response of float arm segments. 
     It is further assumed for most of the applications of this invention herein described that inner arm segments 11 are never permitted to rotate lower than positions substantially parallel to, and probably recessed within and flush with the deck or upper surface of the center section 1. It is also assumed that, except for possible slight back-buckling previously described, float arm segments adjacent to internal pivots 17 and 21 will maintain substantially collinear (or parallel) orientations with respect to each other when the floats 2 and 3 are raised above the normal laterally extended sailing position and that a similar relation will apply for internal pivots 18 when floats 2 and 3 are lowered below the lateral position. 
     There are applications in which exceptions to these last assumptions would be desireable. In particular, the longitudinal planes most closely approximating a symmetrical bisection of the floats 2 and 3 could be caused to rotate a small amount around the longitudinal float axes, increasing their inboard tilt with respect to the vertical by a downward buckling of internal float arm joints 21 and probably also of joints 17 to lessen the effect of increasing heel on the trim of the leeward float. Such downward buckling of joints 17 would require internal float arm segments 11 to rotate below positions parallel to the deck. Protruding edges within center section superstructure 43 or other mechanisms restraining arm segments 11 could be displaced or released for such an application. In one application requiring asymmetric adjustment of float arm assemblies 4 and 5 it is desired to raise one float over the deck of the capsized vessel further than the other toward, or past, if possible, the center line of the center section 1 for the purpose of recovering from capsize in a chosen direction. In another application requiring asymmetric float arm adjustment it is desired to lower one float under the superstructure 43 of the center section 1 further than the other toward or past the keel, if possible, for the purpose of deliberately capsizing the vessel in a chosen direction. Downward rotation of inner upper arm segments 11 for such a float past the normal limiting position parallel to the deck might be required to move the float further toward, or past, the keel than would be possible in a symmetric operation of the floats. 
     There are applications in which it may be desired to lower floats to the sides with the outboard sides of the floats at or below the level of the keel of the center hull, the floats being oriented with outboard sides relatively horizontal to enable the vessel to act as a shoal draft vessel of width no greater than that of the center section or to provide greater stability and comfort in a standard-width berth. Such a capability for positioning the floats at or below center hull keel depth (with center board raised, if any is used) could also be utilized to provide support for beaching, storing, launching or transport. 
     With a float arm configuration according to the present invention, permitting floats 2 and 3 to be retracted to the sides of or below the center section and to be supported by self-contained rigging or mechanisms, it would be possible to attach, temporarily or permanently, to the outboard sides at the gunnels of such floats, wheels, skates, skis, bumpers or skids and to switch the vessel into a mode of operation appropriate to these devices merely by lowering the floats. 
     Additional extendable, jointed or pivoting members could be added to the basic configuration of float arm assemblies 4 and 5 illustrated in FIGS. 1, 2 and 3 or to alternate embodiments of such assemblies as described herein to extend the degrees of freedom by which float position or attitude may be varied without special adjustment of the basic configuration. An example of such application is the rotation of floats around their longitudinal axes to bring hydrofoils or planing surfaces into operational position. To permit such an application the outer ends of the lower arms could be made pivotally attached to the floats or to the upper arms instead of fixedly attached to the floats. Suitable extendable or jointed means could be provided between upper and lower arms or between either arm and the float, according to pinciples, already described, of the present invention, to effect such float adjustments. 
     FIG. 14 illustrates in cross sectional outline of a trimaran according to the invention the relative positions of floats 2 and 3 and of affected elements of float arm assemblies 4 and 5 when said floats have been pivotally &#34;raised&#34; as far inward &#34;over&#34; the center section 1 of the capsized vessel as center hull shrouds 7 will permit in a fully taut condition with the mast 6 in an erect position. In the illustrated example the combined bouyancy of the floats in this position is sufficient to lift the center section 1 out of the water. It can readily be seen that the center of gravity would be situated higher than the center of bouyancy in this orientation and that, as long as the largest fraction of the volume of both floats remains underwater, the equilibrium at 180 degrees of heel will be unstable. If, in heeling from the fully inverted position, one float partially emerges from the water while part of the superstructure on the side toward which the keel is leaning submerges a compensating amount, an angle of lean will be reached at which the resultant center of bouyancy moves laterally toward that side through a distance greater than that through which the center of gravity moves. Beyond that angle of lean the center of bouyancy will provide a restoring moment to keep the vessel capsized in metastable equilibrium. If the separate centers of bouyancy of the floats remain relatively widely spaced, as shown in FIG. 14 with hindrance provided by shrouds 7, correspondingly large external leverage must be applied to right the vessel. If the floats 2 and 3 can be brought sufficiently close together &#34;over&#34; the center section 1 to reduce the region of metastability to a few degrees around 180 degrees, sufficient leverage to right the vessel could be provided by a wind which is relatively light compared to that which capsized the vessel. 
     The simplest solution for removing the hindrance provided by shrouds 7 would be to release or relax said shrouds. This method could possibly result in dismasting or damage to mast 6 or center section 1 where it is stepped. An alternate solution for removing the hindrance of shrouds 7 to bringing floats 2 and 3 together &#34;over&#34; the deck of the center section is provided by pivotally lowering (with respect to the upright vessel) said shrouds toward the deck of said center section along with mast 6. The lowering and subsequent reraising of mast 6 is a basic component of the present invention with various applications both when performed independently of changes in float position and when performed in conjunction with the raising and subsequent relowering of floats 2 and 3. 
     FIG. 15 is a perspective view of a trimaran according to the invention wherein a mast 6 pivotally mounted at its base 56 and elements of standing rigging are shown in somewhat schematic representation together with the center section 1 in outline to illustrate a method in its simplest form for raising and lowering mast 6 and shrouds 7 as a unit. The shrouds 7 are attached to center section 1 at pivots 57 which are transversely collinear with mast pivot 56; thus the shrouds 7 and the line through pivots 56 and 57 form a triangle bisected by the mast 6 and thus shrouds 7 remain under constant tension in a common transverse plane with mast 6 as the angle between the mast and the vertical is varied from 0 degrees to 90 degrees in either the fore or the aft directions. Forestay 58 and backstay 59 are adjustable in length between the masthead and the bow and stern, respectively, with means for adjusting these lengths being represented by winches 60 and 61 in the bow and the stern, respectively. One stay may be reeled out to increase its effective length by a given amount while the other stay is being reeled in by a compensating amount to effect a corresponding change in the angle which the mast makes with the vertical. 
     In order to bring the floats 2 and 3 as close together &#34;over&#34; the deck of center section 1 as the float arm geometry will allow without the floats being interfered with by the shrouds 7 under tension, it would be necessary to lower the mast 6 to an angle with the vertical at which the distance between shrouds is less than the distance between floats at the height of least separation of the floats. When the mast 6 has been lowered far enough toward the deck to intercept the transverse vertical plane within which the fore or aft pair of port and starboard float arm assemblies 4 and 5 are situated and within the space between raised float arms 9 and 10, interference of the shrouds 7 with upper float arms 9 must be considered. The base of the triangle between shrouds 7 need not actually be shorter than the distance between port and starboard inboard upper arm pivots 16 in order for such shrouds not to interfere with upper float arms 9 as the floats 2 and 3 are raised. It is sufficient for the transverse width of the triangle to be less than this distance at a height above pivots 16 equal to the fore and aft distance between the shroud pivots 57 and the float arms 9 which shrouds 7 must accommodate in order for shrouds 7 to be able to remain taut without interfering with float arms 9 when floats 2 and 3 are raised and the mast 6 is sufficiently lowered. 
     By placing the shroud pivots 57 sufficiently lower than the mast pivot 56 or further toward the end of the vessel toward which it is desired to lower the mast, the shrouds 7 would become sufficiently relaxed to accommodate the floats without fully lowering the mast. The distance by which to displace shroud pivots 57 to fully accommodate floats 2 and 3 at a chosen minimum angle of the mast with the vertical can be calculated according to known methods of analysis. A combination of narrower base shrouds which remain taut and of wider base shrouds which are stepped to relax as the mast is lowered or of releasable shrouds might be employed. Alternatively, means might be provided in the form of sliding tracks in the fore and aft direction to permit varying the amount by which shroud pivots 57 are biased fore or aft of mast pivot 56. 
     As the mast 6 is lowered toward one end of the vessel, the perpendicular distance between pivot 56 at the base of the mast and the stay 58 or 59 extending to the other end of the vessel decreases. As the triangle between the mast and this stay collapses, the moment for reraising the mast becomes zero no matter what force is applied to the winch 60 or 61 to which this stay is attached. The simple method illustrated in FIG. 15 can therefore not be used unaided to reraise the mast 6 after it has been lowered all the way to the deck of the center section 1 and means would have to be provided for propping up the mast or the stay. 
     FIG. 16 shows in a similar view a pair of modifications to the method illustrated in FIG. 15 for changing the angle of the mast with the vertical in which either fore or aft mast stays of either fixed or variable length could be stepped on the apexes of triangular supports which are pivotally connected around axes along the base of these triangles transverse to the center line of the vessel and in which rigging from the underside of such triangular supports could be used to control the height of the apexes of such triangles and hence the effective lengths of the mast stay. In one embodiment of such a modification forestay 58a of fixed length is stepped at point 62 on the apex of triangular support 63, which lies parallel and flush with the fore deck of center section 1 when the mast 6 is in its normal vertical position and rigging 58b from the underside of triangular support 63 is led via tension directing pulleys 64 within the center section to a winch or other means (not shown) for adjusting the length of line 58b. The use of such fixed length forestays 58a could make possible the use of roller reefing mechanism 65. In the other embodiment of such modification backstay 59 of variable length is led via tension directing pulleys 66 at the apex of triangular support 67 and in the center section 1 to a winch or other means (not shown) for adjusting its length. The triangular support 67 in this modification extends aftward from the stern of the center section 1 and is used primarily to extend the base of the triangle between the mast 6 and the backstay 59 but rigging 59a,  which is led from the underside of triangular support 67 via tension directing pulleys 64 to a winch or other means (not shown) for adjusting the length of line 59a and which is used to control the height of the apex of triangle 67, provides alternate means for adjusting the effective length of backstay 59. 
     FIG. 17 shows in similar perspective view of center hull 1 and mast 6 with forestay 58 and backstay 59, led via tension directing winches 64 to centrally located winches 60 and 61, as described for FIGS. 15 and 16, alternate means for changing the effective length of backstay 59 in the form of block and tackle 68, extending between pulley 69, which rides on the backstay 59, and a point near the base of the mast 6 with the fall of block and tackle 68 being led to winch 70. Without changing the actual length of backstay 59, using the primary method described for FIGS. 15 and 16, the triangle between mast 6 and backstay 59 can be collapsed by shortening block and tackle 68. This alternate arrangement provides better leverage as well as better mechanical advantage than the primary method of shortening backstay 59 as the triangle between mast and backstay becomes nearly collapsed and the head of the mast extends substantially beyond the end of the vessel. An additional advantage is that backstay 59 remains fixed in length so that the mast 6 could be easily restored to the same trim angle when the forestay 58, which would have to be allowed to lengthen as the mast 6 is lowered, is shortened again to its former length. When not in use, block and tackle 68 could be relaxed or released from pulley 69 and stowed on deck. A similar arrangement could be used for the forestay 58 if it is desired to lower the mast 6 toward the bow. 
     FIG. 18 shows in perspective view from above, a simplified representation of a trimaran according to the invention in which mast 6 is being lowered toward the stern around pivot 56 near its base using any of the means (not shown) discussed for FIGS. 15, 16 and 17 and in which float shrouds 8, stepped forward of the mast and of fixed length are causing floats 2 and 3 to be pivotally raised around inboard pivots 20 of lower float arms 10. Other components of standing rigging or of float arm assemblies, which change length or orientation in conjunction with the operation illustrated in FIG. 18 but which are not essential to understanding the action illustrated, have already been discussed in detail and are left out of this simplified representation. The distance by which float shrouds 8 must be stepped forward of the mast 6 to cause floats 2 and 3 to be raised to a given angle of arms 10 with the vertical and for a given point of connection on the mast 6 for shrouds 8 can be calculated with standard methods of analysis. As the mast 6 is being lowered to an angle of inclination at which the shrouds 8 lie in a horizontal plane an upward component of force is generated to lift the floats 2 and 3. As the mast 6 is lowered further the inward component of force due to shroud tension will be generated to pull the floats together in a continuation of the pivoting action, as illustrated in FIG. 19--making special rigging to do this unnecessary. A similar operation could be carried out with the mast 6 being lowered toward the bow and with the shrouds 8 being stepped toward the stern. The distance by which the shrouds 8 are stepped forward or aft of the mast 6 could be made variable by terminating the shrouds 8 on a mechanism which slides in a track on the deck of floats 2 and 3. The position of float shrouds 8 could thus be adjusted to alter the amount by which floats 2 and 3 will be raised (or allowed to lower) for a given angle of the mast 6 and the means for controlling the adjustment mechanism could consist of a manual locking/releasing device or of a block and tackle arrangement. 
     After floats 2 and 3 have been raised above the deck of center hull 1, as illustrated in FIG. 18, by lowering the mast 6 to create a lifting tension on the floats, the return of the floats to their laterally extended positions, using means previously described (return-down rigging 26), can be used to re-raise the mast. An upward force will be generated on the mast 6 by shrouds 8 until the mast has been sufficiently raised for float shrouds 8 to lie in a horizontal plane. When the mast has been raised past this angle, a forward component of force will be applied at the head of the mast by the shrouds 8. Any action employing the float shrouds 8 in the raising of the mast 6 would be additional and optional to means described for FIGS. 15 through 17. 
     The motive force for &#34;lowering&#34; the head of the mast (with respect to the upright vessel) toward the deck of the center section 1 could be provided, when the vessel is capsized, by means of bouyancy of fixed size or of inflatable size and permanently mounted at the head of the mast or hoistable by means of a halyard. With such bouyancy in place and with means provided for releasing one of the stays 58 or 59 the motive force for raising the floats above the deck according to the description of FIG. 18 could thus be provided. If the release of said stay and inflation or hoisting of said flotation device is made self-initiating by appropriate means, the vessel could be made essentially self-righting, at least to the stable position on its side with floats raised, as illustrated in FIG. 6(d). The final stage of recovery from capsize would require lowering of the floats 2 and 3 to the normal, laterally extended position. 
     It has been assumed for the method described in FIG. 18 for raising/lowering floats 2 and 3 in conjunction with lowering/raising the mast 6 that the length of the float shrouds 8 would be kept fixed, at least during the operation. If the lengths of said shrouds are also made variable under helmsman&#39;s control, with the extensions of said shrouds being led via pulleys on or in the floats 2 and 3 and thence to winches or equivalent devices, the manipulations of mast angle and float height can be made independent of each other at the helmsman&#39;s disgression. The effective length of said shrouds could be decreased by such means to raise the floats without changing the angle of the mast if the mast stays are not released. If, on the other hand, the mast is lowered to the deck in a capsize recovery as the means for raising the floats above the deck, as described for FIG. 18, the winches for controlling float shrouds 8a could then be released so that the mast could be left on deck while the floats are independently relowered. If the float return-down rigging 26 is not released, the mast can be lowered/raised independently by means for adjusting the length of these shrouds. 
     FIG. 20 shows in simplified perspective view of a trimaran according the the invention, the center hull 1, floats 2 and 3, mast 6 and one float shroud 8a employing block and tackle arrangement 71 to vary the effective length of shroud 8a between a point on mast 6 and float 2. Block and tackle configuration 71 is connected at a plurality of points along the length of float 2 by single pulley blocks 72. The upper block 73 consists of a plurality of pulleys, one for each float deck pulley 72, and the shroud 8a is led in turn around each of the pulleys of block 73 to one of the pulleys 72. The fall of block and tackle 71, which is the extension of shroud 8a, is led via tension directing pulleys or other means (not shown) from one of these deck pulleys 72a to a winch or other means for adjusting its length from a central location. Block 73 is suspended between its points of connection on float 2 and mast 6 at a location in which a balance of forces will be attained in the plane of the rigging. As the angle of the mast 6 with the vertical is altered or the length of the shroud 8a is varied, both the effective length of an equivalent fixed shroud 8 and the effective point at which it would step on the float 2 may vary. By appropriate location of pulleys 72 along the float 2 an improved relationship between upward forces and longitudinal forces on the float 2 can thus be realized over an arrangement with a fixed single point of connection to the float 2 throughout the whole range of angles which mast 6 can assume with respect to the vertical. Not only can the upward component of tension exerted by the mast 6 on shroud 8a be increased relative to the longitudinal component; the twisting moment on float 2 around the points of connection of float arm assemblies 4 can be reduced. Additional control over this relationship can be obtained by placing any of the pulleys 72 on a sliding track, as illustrated schematically for pulley 72a, so that its fore and aft position can be adjusted. If the change in float height for a given change in mast angle with no change in shroud length is not sufficient for the given location of the set of pulleys 72, the distance from any of the pulleys 72 or from the mast 6 to block 73 can be constrained in an alternate embodiment of block and tackle configuration 71 by replacing the segment in question of shroud 8a with one of fixed length or by otherwise replacing any of the pulleys 72 or 73 with a fixed termination for shroud 8a or now separated lengths of tackle in the block and tackle arrangement 71. 
     Any subset of physical features and principles described or mentioned herein which may be reasonably used in combination to achieve operational capabilities expressed, implied or readily apparent in the use thereof may be considered to be an embodiment of the present invention insofar as there can be shown to be any degree of originality in the function or application of said features and principles separately or in conjunction with any other features of such subset.