US3083933A

US3083933A - Ski glider

Info

Publication number: US3083933A
Application number: US25369A
Authority: US
Inventors: Richard T Cella
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-04-28
Filing date: 1960-04-28
Publication date: 1963-04-02
Anticipated expiration: 1980-04-02

Description

April 2, 1963 R. T. CELLA 3,033,933

SKI GLIDER Filed April 28, 1960 2 Sheets-Sheet l Inventor le/c/mea Z CELL/4 Attorney April 2, 1963 R. T. CELLA 3,033,933

SKI GLIDER Filed April 28, 1960 2 Sheets-Sheet 2 NORMAL WIND LINE Q! 0 k N no N CAMBC R LINE SUPPORT PO/ N T A Horn 2 y tates This invention relates to gliders and more particularly to a glider suited for use with water skis.

An object is to provide a glider of the above type which is capable of lifting a skier from the water and returning him to the water without requiring any action or control on his part.

Another object is to provide a device of the above type which automatically lifts the skier from the water when towed at a predetermined speed, attains a height which depends in general upon the towing speed and which is capable of returning to the water in a free glide should the towing force be interrupted as by the stopping of the towing boat or the breaking of the tow line.

Another object is to provide a device of the above type which is not dependent for its safe operation upon any skill on the part of the rider.

Other objects and advantages will be apparent as the nature of the invention is more fully disclosed.

The invention provides a glider of the above type having a high degree of lateral and longitudinal stability. When disturbed from its normal free glide path as by a gust of wind, it will return to its free glide attitude in not more than two highly damped oscillations. Lateral stability is attained by providing a suitable wing dihedral. Longitudinal stability is attained by locating the weight of the rider at a predetermined point on the wing chord and suspending the rider from a pivot point so chosen that the center of gravity is located below the center of lift by the required amount to provide a righting moment tending to return the glider to its free glide attitude whenever the glide angle is disturbed. The pivotal suspension of the rider not only causes the weight to be applied constantly at the predetermined pivot point for producing the righting moment but also provides a safety factor as it prevents the rider from being thrown forward or backward due to a sudden change in the pitch angle of the glider.

The nature of the invention will be better understood from the following description, taken in connection with the accompanying drawings in which a specific embodiment has been set forth for purposes of illustration.

In the drawings:

FIG. 1 is a side elevation of a glider embodying the invention;

FIG. 2 is a broken top plan view of the glider;

FIG. 3 is an enlarged detail taken on the line 3-3 of FIG. 2 showing the construction of the supporting framework;

FIG. 4 is a section taken on the line 44 of FIG. 3;

FIG. 5 is a diagram illustrating the relationship of the various components of the glider;

FIG. 6 is a perspective view of the glider framework; and

FIG. 7 is a detail of the support bar.

Referring to the drawings more in detail the glider is shown as having a wing 10 composed of a framework of tubular members of strong light weight material such as aluminum which are joined together by welding, bolting or in any other convenient manner to form a rigid structure. In the form shown the framework comprises a series of cambered tubes 11 shaped to conform to the wing surface and spaced along the length of the wing. The tubes 11 are joined at their leading ends to a tube 12 extending along the leading edge of the wing 10 and at their trailing ends to a tube 13 extending along the trailing edge of the wing. A tapered strip 14 is disposed in back of the tube 13 to shape the trailing edge of the wing.

atet "ice The forward tube 12 extends substantially straight across the glider to points 15 near the wing tips, at which points it is bent upwardly at an angle of say 30 degrees to form a dihedral in the manner well known in the art. The rear tube 13 is similarly bent upwardly to form the dihedral and forwardly to conform to the desired shape of the wing tip. The entire structure is covered on both sides with a standard wing fabric 16 which is secured in place and stiffened with airplane dope as in the usual practice to form an air foil which is impervious to water so that the structure is buoyant. The center portion of the wing between the two central camber tubes 11 is left open to form an opening 17 for the rider. A tube 30 extends between the two central camber tubes 11 at the forward edge of the opening 17.

The framework or truss is formed by vertical struts 20 extending downwardly from the two central camber tubes 11 at a point about one-fifth of the distance from the leading edge to the trailing edge of the wing measured along a straight chord 21 as indicated in FIG. 5, and a similar vertical strut 22 located at a point about four-fifths of the distance to the trailing edge measured in the same manner. The lower ends of the

struts

20 and 22 are joined by horizontal tubes 23. A diagonal brace 24 extends from the top of the strut 20 to the bottom of the strut 22. Other braces may be provided if desired to impart rigidity. The lower ends of the struts 2i) are braced by a U-shaped tube 25 extending forwardly of the wing and the lower ends of the struts 22 are joined by a similar U-shaped tube 26 extending rearwardly of the wing to provide clearance for the rider.

A support bar 27 extends between the diagonal braces 24 at a point located 28% of the distance along the chord 21 from the leading edge of the wing as shown in FIG. 5. A seat in the form of a U-shaped tube 28 is pivoted to the support bar 27 so that a rider seated in the swinging seat always hangs vertically downwardly regardless of the pitch angle of the glider. are also mounted on the support bar 27 to permit a rider to support his weight by his hands if he so desires. A pair of

braces

31 and 32 extend laterally from the bottom of the strut 22 to about the midpoint of the wing spans.

A stabilizer 35 is formed by camber tubes 36 joined at their leading ends by tube 37 and at their trailing ends by a tube 38 to form a framework which is covered by a wing fabric 39 as in the case of the wing. Rudders 40 which may be formed of sheet aluminum for example are rigidly secured at the tips of the stabilizer 35. The stabilizer is carried by tubes 41 which form an extension of the tubes 23 and bracing tubes 42 which form an extension of the center camber tubes 11 and are attached to the tubes 41 at a point in advance of the stabilizer.

The support bar 27 is located at a point so selected that the weight of the rider is shifted forwardly and backwardly in response to any upward or downward tilting of the nose of the glider by an amount to produce a moment which restores the glider to the proper glide path.

It has been found that the support point should remain between one-fifth and two-fifths of the distance along the chord 21 from the leading to the trailing edges of the wing when the attitude of the glider varies between 30 degrees above to 40 degrees below the normal glide angle. For this purpose a line 44 is drawn from a point on the camber tube one-fifth of the distance along the chord 21 from the leading edge at a rearward angle of 30 and a line 45 is drawn twofifths of the distance along the chord 21 from the leading edge from a point on the camber tube at a forward angle of 40. These lines are found to cross at a point 46 which lies on a vertical at the 28% point in the chord 21. The support bar 27 is positioned at this point and when so located causes the riders weight to Straps 29 1 automatically serve as a stabilizing force to maintain the glider on its proper glide path without requiring any control on the part of the rider.

In use the water. skier carries the glider by holding the support bar 27 and when he reaches the proper speed the glider will lift him from the surface of the water. He may then seat himself in the swing seat 28 or hang from the straps 29 as he desires. He will remain aloft as long as the towing speed is maintained and will descend when the speed is reduced. Should the towing force be interrupted as by the stopping of the towing boat or by the breakage or release of the towing cable the glider will immediately assume the free glide attitude and will retain this attitude until the rider is returned to the surface of the water. Should the glider be disturbed meanwhile as by a gust of wind the riders weight will restore it to the proper glide path within not over two highly damped oscillations without requiring the exercise of any control or skill on the part of the rider.

What is claimed is:

1. A glider for water skiing or the like comprising a rigid air foil and a stabilizer mounted and supported by a supporting framework to form a rigid unit, a truss mounted below said framework and a transverse support bar carried by said truss, means pivotally suspending a rider from said support bar, said air foil having an opening for the rider above said support bar, said bar being located at about the intersection of the first line drawn from a point on the air foil one-fifth of the distance from the leading edge thereof at a rearward angle of about 30 degrees to the vertical and a second line drawn from a point on the air foil about two fifths of the distance from the leading edge thereof at a forward angle of about 40 degrees to the vertical, said point being adapted to produce a righting moment whenever the pitch angle of the glider is disturbed from its proper glide path.

2. A glider for water skiing or the like comprising a wing composed of a rigid framework of light weight tubular material and an air foil covering said framework on both sides, said air foil being impervious to water whereby said wing is water buoyant, a stabilizer of similar construction rigidly attached to said wing, said stabilizer carrying a pair of sheet metal fixed rudders, a truss of light weight tubing mounted below said wing and carrying a transverse support bar, means for pivotally suspcnding a rider from said support bar, said support bar being located at about the intersection of a first line drawn from a point on the air foil one-fifth of the distance from the leading edge thereof at a rearward angle of about 30 degrees to the vertical and a second line drawn from a point on the air foil about two-fifths of the distance from the leading edge thereof at a forward angle of about 49 degrees to the vertical, said point being adapted to pro duce a righting moment Whenever the pitch angle of the glider is disturbed from its proper glide path.

3. A glider for water skiing or the like comprising a rigid air foil, a truss rigidly fixed to said air foil and a stabilizer fixed to said truss rearwardly of said air foil and adapted to control the pitch angle of said air foil, a transverse support bar carried by said truss and a seat for a rider pivotally suspended from said support bar, said support bar being located below the center of lift of said air foil and at a point between one-fifth and two-fifths of the distance from the leading to the trailing edges of said air foil, said point being selected and adapted to produce a righting moment for restoring the air foil to its proper glide path whenever the pitch angle of the glider is disturbed.

References Cited in the file of this patent UNITED STATES PATENTS 881,837 Whitehead Mar. 10, 1908 1,230,620 Summers June 19, 1917 1,233,227 Harris July 10, 1917 2,792,191 Perry May 14, 1957 OTHER REFERENCES Aerodynamics of the Airplane, Clark B. Millekan, 1941, pp. 141-143 and 149.

Parade, Washington Post (Sunday edition of April 12., 1959), page 43 relied on.