US3765360A

US3765360A - Reinforced mast construction

Info

Publication number: US3765360A
Application number: US00240878A
Authority: US
Inventors: P Monfort
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-03-31
Filing date: 1972-03-31
Publication date: 1973-10-16
Anticipated expiration: 1990-10-16

Abstract

Mast construction for sailboat spars, flagpoles and the like, and a method of making the same. The mast includes an inner wood core generally cruciform in shape, and low density, rigid thermoplastic foam material positioned in the open areas of the core, with the exposed surface of the thermoplastic material being shaped to provide the desired mast contour. A plurality of reinforcing wires are secured around the foam material, and a resinous material is trowelled around the foam material and the cruciform core, with the resinous material when set imbedding the reinforcing wires and providing a smooth outer contour.

Description

Monfort 1 Oct. 16, 1973 REINFORCED MAST CONSTRUCTION [76] Inventor: PlattWIdiifoit, R. F. D. 2, WisCas set, Maine 04578 [22] Filed: Mar. 31, 1972 [2]] Appl. No.: 240,878

FOREIGN PATENTS OR APPLICATIONS 0/ 1860 Great Britain 52/727 Primary ExaminerGeorge E. A. Halvosa Assistant ExaminerSherman D. Basinger Att0rney-Donald D. Jeffery [5 7] ABSTRACT Mast construction for sailboat spars, flagpoles and the like, and a method of making the same. The mast includes an inner wood core generally cruciform in shape, and low density, rigid thermoplastic foam material positioned in the open areas of the core, with the exposed surface of the thermoplastic material being shaped to provide the desired mast contour. A plurality of reinforcing wires are secured around the foam material, and a resinous material is trowelled around the foam material and the cruciform core, with the resinous material when set imbedding the reinforcing wires and providing a smooth outer contour.

7 Claims, 4 Drawing Figures BACKGROUND OF THE INVENTION The present invention relates as indicated to a reinforced mast construction, and relates more particularly to a reinforced mast having particularly advantageous use as spars for sailboats, flagpoles and similar environments where constructional dimensions have traditionally resulted in relatively high material costs.

Heretofore, masts for sailboats and the like have been mostly of wood and metal construction, with aluminum in recent years finding increasing use for such purpose. Due to the rather complex stress requirements, the thickness and weight of the outer skin and metal spar designs have been greater than required for the compressive loading, in order to prevent buckling of the spar. The relatively standard spar design as a result is relatively expensive owing to the high material and fabrication costs.

The same remarks apply with respect to flagpoles, some of which are extremely long. Although flagpoles are obviously not subjected to the same stress considerations as masts for boats, the material costs in accordance with standard design are relatively high, not to mention the attendant problems of transportation of the pole from the place of manufacture to the place of use.

SUMMARY OF THE INVENTION With the above in mind, a primary object of the present invention is to provide a reinforced mast construction which can be made of low cost materials and which can be fabricated relatively inexpensively.

A further object of the present invention is to provide such a mast construction which accurately reflects the stress requirements in the mast, based upon intended usage. The weight and strength of the mast can be varied as desired along the length thereof to match the structural requirements in the mast, and localized areas or reinforcement can be provided where necessary to meet specific use requirements.

Yet another object of the present invention is to provide a mast construction and method of making the same which is without practical limit as to the length or cross section thereof. The mast can be tapered to the desired shape during the assembling method, and various cross sectional shapes such as round, oval, eliptical, or the like can be produced as desired in accordance with the basic concept of the invention.

A still further, more specific object of the present invention is to provide a mast construction in which a wood core of generally cruciform shape is provided, with such wood core being combined with and reinforced by plastic and wire materials the shape of which can be varied as desired. In accordance with the invention, such materials can be applied to the wood core quickly and easily, with the resulting mast construction being comparatively light in weight and low in cost while at the same time providing the necessary structural strength.

Although the above remarks in the following description are directed primarily to mast constructions for use in sailboats, flagpoles, and the like, it will be readily apparent that the method of the present invention and the product achieved thereby may find application elsewhere circumstances permit the use of relatively low cost materials in accordance with the present invention.

These and other objects will become apparent as the following description proceeds in particular reference to the application drawing.

BRIEF DESCRIPTION OF THE APPLICATION DRAWING In the application drawing,

FIG. 1 comprises a perspective view showing the progressive steps in forming the mast, with the upper portion of this figure illustrating the cruciform core by itself, and the relatively lower part of this figure showing the cruciform core covered by a rigid thermoplastic foam material of the desired shape;

FIG. 2 is a fragmentary perspective view showing a further step in the mast construction;

FIG. 3 is a cross-sectional view of the reinforcing and fill wire assembly employed in the fabrication method shown in FIG. 2, and

FIG. 4 is a transverse cross-sectional view through the completed mast.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in more detail to the application drawing, wherein like parts are indicated by like reference numerals, and initially to FIG. 1, the mast includes a generally cruciform shaped wood core generally indicated at 10 which includes a cross member 12 and

members

14 and 16 which extend along and form the major axis of the mast, in the construction thereof shown in the application drawings. The cross member 12 in the form shown is rabbetted to receive the members l4 and 16, which can be rigidly secured to the cross member 12 by gluing or by the use of mechanical fasteners, or both.

The length of the core 10 corresponds to the desired length of the mast and the core may if desired be tapered from end to end depending upon the use requirements. Such tapering can be accomplished readily by simply working down the exposed edges of

members

12, 14 and 16.

The next step in the fabrication process is to apply a preferably rigid thermoplastic foam material to the areas defined by adjacent sides of the

members

12, 14 and 16, as shown in the intermediate portion of FIG. 1. Separate blocks of such foam material, commonly designated at 18 are positioned in such areas, which blocks can be chamfered as indicated at 20 in FIG. 4 to define an open area between the foam material and the wood members. In this manner, the rigid foam material is reduced to the extent possible, thereby reducing the weight of the mast, while at the same time affording an exposed surface which can be contoured to provide the desired exterior surface.

The specific type of thermoplastic foam material employed for the blocks 18 is not critical, with styrofoam, polyurethane, and polyvinyl chloride being acceptable by virtue of the low density and relatively low cost characteristics. It is important that the material used be compatible with the final resin coating applied, as will be discussed in more detail hereinbelow.

The blocks 18 are preferably bonded to the

members

12, 14 and 16, with the exterior, exposed surface being thereafter contoured to provide the desired shape, as shown in the lower-most portion of FIG. 1. The cutting of the blocks to provide such shape can be accomplished in any known manner. For example, where styrofoam is the material employed, a hot wire can be employed for cutting the foam to the desired shape. Where other rigid foam materials are employed, other cutting means may be necessary.

Although only the lowermost portion of FIG. 1 illustrates the foam material fully shaped around the cruciform core, it will be understood that the entire length of the mast will be so shaped. Where the core is tapered as above described, the foam blocks will be similarly contoured to provide a smooth outer surface with the exposed edges of the core.

After the foam material 18 has been bonded to the wood core and shaped as described, longitudinally extending reinforcing wires commonly designated at 24, FIG. 3, are positioned over the exterior of the foam material. Positioned at each end of the mast is a terminating ring 26, only one of which is visible in FIG. 2, over which the adjacent ends of the reinforcing wires 24 are bent. The terminating rings 26 are prefabricated with a welded butt joint, and preferably are of wire at least twice the diameter of the longitudinal reinforcing wires 24. If the opposite end of the mast is tapered, the terminating ring 26 at such opposite end is of course of reduced size, and it will be further apparent that the reinforcing wires 24 will relatively converge at such reduced end.

The reinforcing wires 24 are preferably provided in the form of a wire mesh assembly, with a plurality of such wires being assembled in predetermined spaced relation by fill wires 28 disposed interiorly of the wires 24, as shown in FIG. 3. The fill wires 28 and wires 24 are preferably interconnected at their joints by spot welding. The ends of adjacent fill wires 28 are hooked as shown at 30 and 32 thereby enhancing the transverse tensile strength of the mast. Where the mast is tapered, the fill wires can be kinked or bent to accommodate the reduced spacing between the wires 24.

Areas of known localized stress can be accounted for in the manufacture of the mast through the provision of one or more reinforcement areas. In FIG. 2, a supplemental reinforcing wire 34 which is in the form shown of generally shallow V-shape, can be placed inside crimped at the ends thereto of the wires 24 and at additional areas if desired. Supplemental reinforcement is desirable in those areas where high stress can be anticipated, for example, where bolts are to be installed to attach shroud cables or halyard sheaves.

A particular advantage of the present invention is the ability to precisely determine the structural characteristics of the mast depending upon the end use of the same. For example, where the mast is intended to be used as a sailboat mast, the stress in the upper regions of the mast is considerably less than elsewhere. Thus, some or all of the longitudinally extending reinforcing wires 24 may be terminated at those regions beyond which the stress is negligible.

The final step in the formation of the mast comprises the trowelling of a liquid resinous material 36 over the foam blocks 18 and exposed ends of the wood core, fully encapsulating the reinforcing

wires

24, 28 and 34. The resinous material should be selected so as to be compatible and non-reactive with the foam blocks 18, and within this limitation the particular material employed is not critical. The material can be set at either ambient or elevated temperatures. Where the foam blocks 18 comprise styrofoam, epoxy resin is the preferred resinous material. Where polyurethane material is used for the foam blocks 18, polyester resin is the preferred material. Concrete mortar could alternatively be employed, although such material would undesirably add to the overall weight of the mast. When the material is trowelled over the foam and wires as described, the provision of a smooth outer surface completes the mast construction.

I claim:

1. Mast construction for sailboat spars, flagpoles and the like, comprising:

a. an inner wood core generally cruciform in shape;

b. low density, rigid thermoplastic foam material positioned in the open areas defined by adjacent legs of said cruciform wood core, the exposed surface of said thermoplastic material being shaped to provide the desired mast contour;

c. a plurality of reinforcing wires disposed longitudinally on the exterior of said foam material and transversely spaced around the circumference thereof;

d. means for interconnecting said reinforcing wires to enhance the resistance of structural stress in the mast, and

e. resinous material around said foam material and said cruciform core and imbedding said reinforcing wires thereby to provide a smooth outer contour.

2. The mast of claim 1 wherein said rigid thermoplastic foam material is shaped and arranged on said cruciform wood core so as to provide an open area adjacent the center of the cruciform thereby to provide a hollow, relatively light weight mast.

3. The mast of claim 1 which is tapered in cross sectional thickness from one end thereof to the other.

4. The mast of claim 1 wherein said means for interconnecting said reinforcing wires comprises fill wires extending circumferentially within and secured to said reinforcing wires, the ends of adjacent fill wires being attached to rigidify said reinforcing wires and enhance the transverse tensile strength in the mast, and terminating rings disposed at each end of said mast around which the reinforcing wires are hooked.

5. The mast of claim 4 wherein said terminating rings are pre-fabricated and shaped to correspond to the shape of the opposed ends of the mast, with the diameter of said terminating rings being at least twice the diameter of said reinforcing wires.

6. The mast of claim 4 further including supplemental reinforcement means secured to said reinforcing wires in the areas of said mast more likely to be subjected to greater stresses.

7. The method of making a light weight mast for sailboat spars, flagpoles and the like comprising the steps of:

a. providing a wood core cruciform shaped in cross section;

b. applying to the exterior of said core a low density, rigid thermoplastic foam material bridging the legs of the cruciform core at the terminal portions thereof;

c. shaping the exterior of said foam material to provide the desired exterior contour of said mast;

d. positioning reinforcing wires longitudinally along the exterior of said foam material in transversely spaced relation;

e. interconnecting the intermediate and end portions stantially to imbed said reinforcing wires so as to of said reinforcing wires, and provide a mast having a smooth contour of the def. covering the exterior of said foam material and said sired shape.

core with a resinous material of a thickness sub-

Claims

1. Mast construction for sailboat spars, flagpoles and the like, comprising: a. an inner wood core generally cruciform in shape; b. low density, rigid thermoplastic foam material positioned in the open areas defined by adjacent legs of said cruciform wood core, the exposed surface of said thermoplastic material being shaped to provide the desired mast contour; c. a plurality of reinforcing wires disposed longitudinally on the exterior of said foam material and transversely spaced around the circumference thereof; d. means for interconnecting said reinforcing wires to enhance the resistance of struCtural stress in the mast, and e. resinous material around said foam material and said cruciform core and imbedding said reinforcing wires thereby to provide a smooth outer contour.

7. The method of making a light weight mast for sailboat spars, flagpoles and the like comprising the steps of: a. providing a wood core cruciform shaped in cross section; b. applying to the exterior of said core a low density, rigid thermoplastic foam material bridging the legs of the cruciform core at the terminal portions thereof; c. shaping the exterior of said foam material to provide the desired exterior contour of said mast; d. positioning reinforcing wires longitudinally along the exterior of said foam material in transversely spaced relation; e. interconnecting the intermediate and end portions of said reinforcing wires, and f. covering the exterior of said foam material and said core with a resinous material of a thickness substantially to imbed said reinforcing wires so as to provide a mast having a smooth contour of the desired shape.