CA1161874A - Flying disc - Google Patents

Abstract

FLYING DISC

ABSTRACT OF THE DISCLOUSRE
A molded flying disc with most of the weight concentrated in an outer annular ring. The central opening in the ring is covered by a thin sheet of material, such as plastic or cloth, stronger than a sheet of the molded material of the same thick-ness and diameter. The perimeter of the sheet is attached to the ring.

Description

1 8~ ~

Field of the Invention This invention relates to flying discs and particul-arly to toy discs thrown by hand in such a way as to have both forward and angular momentum.
The Prior Art The type of toy with which this invention is concerned is similar to discs marketed under the trade mark Frisbee by Wham-O Mfg. Corporation. Such a toy has a relatively flat, circular central plate with an outer rim curved away from the plate to form a shallow dish. The edge of the rim has a rounded cross section resembling an air foil. The thickest part of the air foil is not immediately adjacent the edge but is perhaps one-third or so of the distance from the edge to the plate.
The inwardly facing surface of the air foil section is sub-stantially flat in cross section and, therefore, defines a generally cylindrical surface. The entire disc is molded of a suitable thermo-plastic material, such as polyethylene, and the cylindrical configuration of the inwardly facing surface of the rim makes it easy to remove the disc from the mold.
While the central section has been referred to as a plate, it need not be perfectly flat, although it may be.
Frequently this section is molded to have a slightly convex curvature as viewed from the side away from the rim. However, the central surface is so nearly planar that, for descriptive simplicity, it will be referred to as planar hereinafter.
Interest in the type of discs with which this invention is concerned is based on their flight characteristics.
The shape of the disc gives it lift, when properly thrown, so ~i 1 :I B~7~

that it does not simply sink to the ground as would a smooth, spherical ball of the same mass thrown with the same force.
Some enthusiasts try to throw the disc so that it flies as far as possible, and contests are held for that purpose. Other enthusiasts like to throw the disc back and forth to each other, either keep them in the air or bouncing it off the ground somewhere between the players. Still other players try to cause their discs to follow unusual, curved flight paths.
As might be expected, the various requirements of different players have led to different designs of "Frisbee"
discs. A main difference is in the wè~ght, which may be as light as about 110 grams or as heavy as about 180 grams. Wind conditions have an important bearing on the particular disc that an enthusiast will select at a given time. Heavier ones are usually preferred in windy weather.
Although polyethylene does not shatter as would a more brittle material, it can be nicked particularly when it is bounced o~f a paved sur~ace or ~lies into an abrasive surface.
The resulting projections from the originally smooth surface can make the disc painful to catch.
The flight characteristics of a flying disc are a~ected by the air foil and sur~ace configuration, especially on the convex surface. Such discs are normally thrown with the rim extendiny downwardly from the plate, which is equivalent to saying that the convex surfaces face upwardly. For this reason the convex surfaces will be referred to as the upper ones and the concave surfaces as the lower ones in the following description.

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` " ~ 3 ~L874 There is a Right Hand Rule of Spinning Objects that is important in determining the flight path that will be followed by a spinning disc. It has been found desirable to mold slightly raised, concentrically circular ridges in the upper surface of a flying disc near the outer part thereof to reduce air drag and improve precessional qualities of the disc by counteracting the force produced by the Right Hand Rule just mentioned. U.S. Patent 3,359,678 to Headrick describes such ridges, which interfere with air flow and therefore are called "spoilers'~. It is thought that such concentric ring spoilers have the greatest effect when the forward velocity of the disc is greatest relative to the wind speed. Thus, the concentric ring spoilers are effective in flights for distance but are apparently not so much so in shorter flights.
Other publications that describe characteristics of "Frisbee" flying discs are the book FRISBEE by Stancil E. D.
Johnson, M.D. published by Workman Publishing Company, New York, and a paper entitled "Adaptation of the Frisbee Flight Principle to Delivery of Special Ordinance" by G. D. Stilley of Honeywell Incorporated and D. L. Carstens of the Naval Ammunition Depot, Crane, Indiana, and presented at the AIAA 2nd Atmospheric Flight Mechanics Conference at Palo Alto, California, September 11-13, 1972 (AIAA Paper No: 72-982).
Definition of the Invention In accordance with the present invention there is provided a flying disc comprising:

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an annular member defining an open inner area and having an airfoil shaped cross section, and a thin sheet having an outer perimeter affixed to said annular member to cover the open inner area, characterised in that the thin sheet is of flexible plastics material tautly affixed in position and in that the annular member and the thin sheet are of different materials.
In a preferred embodiment of such a disc the air-foil shaped cross-section may be defined by different curvature on opposite surfaces, the member having a thickness that depends on the radial point at which the thickness is measured; and the said thin sheet has a lighter weight for a volume bounded by an area of unit size and by the thickness of said sheet at said area than the average weight of a volume of-said annular member bounded by an area of said unit size and by the thickness of said annular member at the thickest point thereof.
In another preferred embodiment of such a disc the said thin sheet comprises a perimet:er in substantially one plane; said annular member is curved in one direckion from said plane, whereby said sheet and said annular member combine to define a dish-shaped structure having a concave side and a convex side, said annular member comprising a rounded cross-section that is thickest at an annular position between the edge of said annular member and said perimeter of said thin sheet; and the disc also comprises a plurality of spoilers on said conve~ side, each of said spoilers extending in a direction comprising a radial component.

1 1 6~7~L

Further in accordance with the invention there is provided a method of attaching a peripheral region of a thin sheet polyester disc to an inner peripheral region of a polyethylene annular ring member comprising the steps of:
coating said peripheral region of said disc wi-th an adhesive in liquid form comprising neoprene and l,l,l-trichloro-thane solvent;
oxidi~ing said inner peripheral region of said ring;
coating the resultant oxidized region with said 0 adhesive;
allowing said adhesive on said disc and said ring to dry from approximately fifteen minutes to three hours; and pressing the adhesive-coated region of said disc against the adhesive-coated region of said ring with a pressure of between approximately 250 and 1000 pounds per square inch.
Particular preferred embodiments of the invention will now be described, by way o~ example, with reerence to the accompanying diagrammatic drawings.

-BRIEF DESCRIPTION OF THE DRAWINGS
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Fig. 1 is a top view of a disc according to this in-vention.
Fig. 2 is a cross-sectional view of a fragment of a disc of the type in Fig. 1.
Fig. 3 is a cross-sectional view of a fragment o~ another embodiment of a disc similar to that in Fig. 1.
Fig. 4 is a cross-sectional view of still another em-bodiment of a disc similar to that in Fig. 1.
Fig. 5 is a cross-sectional~view of the structure in Fig. 4 at a later stage o~ construction.
Fig.s 6-8 are enlarged perspective views of fragments of different embodiments of spoilers t:hat can be used.
Fig. 9 is a cross-sectional view of a fragment of a disc with an external snap-on rim cover, Fig. 10 is a cross-sectional view of a fragment of a disc with an illuminated snap-on ring.
Fig. 11 is a c~ ss-sectional view of a fragment o~ a disc with snap-in weighted rings.
Fig, 12 is a cross-sectional view of a fragment of a disc with an internally weighted rim.
Fig. 13 is a cross sectional view of modified attachement means for joining a central web to an annular rim to ~orm a Elying disc.
Fig. 14 is an enlarged cross-sectional view of a fragment of a disc ring and the edge of a laminated web, and means for joining them together.

~ 1 61874 DETAILED DESCRIPTION OF THE INYENTION

~ Fig. 1 is a top view of a decorated disc shaped lilce a Frisbee ~l5 - and comprising an annular member 21 and a circular central sheet, or web 22 the perimeter of which is joined-to the radiall~ inner part of the member 21. The top surface of the annular member 21 has¦a circular array of spoilers 23, which are illustrated in this figure as a series of raised, narrow ridges each of which extends in a substantially radial direction. Several embodiments of suitable spoilers will be described farther on in this description.
The central openings in the annular member 21 is covered by a disc of strong, lightweight material, such as Mylar or Estar brand film k~6t~n~ n (a trademarlc of ~W;~eA Kodalc Co.), or similar polyester film that has !
a good strength-to-weight ratio, or a film of other suitable materials, such as acrylic material or polycarbonate materials, or a laminate of L
polyethylene and polyester, or even cloth, such as denim. The Mylar and other plastic films need only be of the order of about 007" to about .Oll" thiclc, which is thinner than even the thinnest polyethylene web that can be satisfactorily molded integrally with the annular outer section.
The use of a lightweight, but strong central web 22 has, as two of i~s most important advantages, substantially greater tear strength ànd lighter weigh~ than a thin, integrally molded polyethylene web, which means that for a polyethylene molded annular member 21 of exactly the same confi~uration, the two--part disc tannular member and web) will stand up under greater l ~ 61~7~
abuse than an inteyrally molded, one-part disc. The greater concentration of weight in the outer annular member, or ring, results in increased angular momentum which, in turn, results in greater stability and flights of longer duration and distance for a given impetus. A mylar web 22 with a thickness of only .007" using .003" laminating material weighs approximately 12 grams and can replace an integrally molded central web portion weighing about 50 grams in existing discs, thus resulting in a weight reduction of about 24%. Since the reduced weight is in the central region and not in the outer ring, the weight of the latter automatically is a greater per-centage of the smaller total weight, which yields longer flight times, slower velocity, and slower drop rate. This allows two players throwing such a disc back and forth to each other more time to catch it. Furthermore, the mylar or other plastic web is very smooth, which reduces drag and results in flights of still greater distance.
Tests made to determine the puncture strength of mylar webs attached tautly across the opening formed by removing the integrally molded central polyethylene web of a Wham-O
SuperPro Frisbee disc and to compare the strength so measured with the strength of the .079" thick integrally molded central web of mold ~60 SuperPro Frisbee discs were carried out as follows~ The round, or shank, end of a .089" drill bit was cut off perpendicular to its axis and the intersection of the cut-off end and the cylindrical side was left sharp and not beveled. The bit was placed in a drill press vice with the t~

~ 1 ~18~14 squared-off end facing upwardly, and the vice was placed on a bathrocm scale. The zero adjustment knob of the scale was turned to bring the scale pointer to zero, and the inte-grally molded web of a .079" thick mold #60 "SuperPro Frisbee"
disc was forced down on the drill bit until the web ruptured.
The scale reading just before rupture was noted, and the same experiment was performed on five such discs. The average of the five scale readings thus obtained was 19.4 pounds.
The same set-up was then used to rupture .007"
thick laminated circular mylar webs the peripheries of which had been attached tautly to the inner perimeter of SuperPro rings. Six such mylar webs were ruptured and the average rupture pressure was 25 pounds, which is 26% higher than the rupture pressure of the polyethylene, even though the mylar was much thinner.
A similar set of experiments was performed using a blunt presser, the .116" diame-ter relatively spherically rounded end of a miniature toggle switch lever. In this set of experiments five Frisbee discs of a type having a integrally molded polyethylene web thickness of .074" were used, and the average rupture pressure was 32.6 pounds. The average of six readin~s of the same type of mylar subjected to the same presser was 50.67 pounds, which indicated the mylar was 54 stronger than the much thicker polyethlene in withstanding pressure from a blunt instrument.
Still another advantage of mylar is that it is a suitable photographic base on which to reproduce artistic designs or ~3 --, l 1 ~1874 personal photographs or commercial messages. Fi~. 1 shows a simplë de-sign, the yin and ynag of Chinese antiquity, but this is only a simple illustration7 Person photographs can be printed on a Mylar or the like su~h as Kodak Extacolor I.D. Print Material #4023 with a white back Ester base to provide incontrovertible proof of ownership in case the disc is commingled with other discs on a beach or other public play area. Designs on the plastic or cloth webs can also be printed by sillc screening, and cloth webs can be embroidered.
One surface of the Mylar can also (or alternatively) be given a reflective coating to serve as a signalling mirror or even a solar stove by covering the concave side of the disc with a rubber membrane that closes the space airti~ht and then pulling the central part of the membrane to create a spherically concave despression in the Mylar to concentrate re- !
flected sunlight. Another alternative is to leave the Mylar or other plas-tic web transparent but form one or both of its surfaces into a Fresnel lens to concentrate the sun's rays.
Fig. 2 shows part of the annular ring 21 in cross section. In this embodiment the perimeter of web 22 is glued to the upper surface of the inner perimeter of the ring 21 and the radially inner ends of the spoilers Z3 terminate at the periphery of the web. The adhesive may be neoprene with 1, 1~ l-trichloroethane as a thinner. The part of the sur-face of the ring to which the web is to adhere is oxidized, either chemi-cally or by being directly heated with a flame just long-enough to malce that part o the surface of thè ring 21 sli~htly shiny. To apply the flame, the rin~ may be mounted on a turntable and rotated at about 20 to 100 r.p.m.
for several seconds, time enouGh for the turntable to rotate from about two to twenty re~olutions with propane gas flame playing on the surface to be oxidized. The oxid;zed inner annular part of the rin~ 21 is coated with the adhesive as is the part of the web 22 to be joined to tha ring. The adhesive is allowed to dry for about 15 minutes to 3 hours on the web and the ring before they are brought into contact with each other. Then the adhesive-coated outesmost annular part o~ the web 22 is pressed against the adhesive-coated innermost annular part of the ring 21 with a force of about 250 to 1000 lb./sq. in. pres.sure for about 10 seconds or longer.
A pressure of 500 lb./sq. in. for 15 seconds has been found quite satis- I.
- factory.
While one inner section 24 of the ring 21 is relatively straight in this cross sectional view and, therefore, cylindrical, or even slightly ~

i, -lOa-tapered, in its full, three-dimensional form, a higher inner surface part 26 is distinctly curved to fit better on the tips of the fingers of a person throwing the disc.
In Fig. 3 the web 22 is captured between the inner part 27 of the ring 21 and the under side 28 of the sectiion of the ring beneath the spoilers 23. In fact, the spoilers 23 in thi;s embodiment may, instead of being integrally molded with the ring, be individuaL strips of suitable material, suc-h as a cloth.based tape, one surface of which is coated with pressure-sensitive adhesive that is capable of sticking to the material 22. As a further alternative, the peripheral region of the web 22 may be molded within the inwardly extending part of the ring 21 and not merely between the spoilers 23 and an unbroken annular region therebelow.
Fig. 4 shows an annular member 21 modified by having a plurality of projections 28 molded near its inner perimeter and extending substantially parallel to the axis of the annular member. The web 22 has plurality of holes 29 that fit over the projections 28. For adequate dispersion of s~resses~ there should be preferably about SO pins 28 and holes 29.
Fig. 5 shows the same structure as Fig. 4 but at a later step of manufacture after the pins 28 have been heated and flat-tened out. Fig. 5 also shows a cross-section of an annular ring 31 of paper having pressure-sensitive cement on its lower sur-face so that it can be sealed over the flattened pins.
The mylar webs 22 attached to annular rings 21 as shown 7 ~

in Figs. 1-5 are not only more resistant to rupture by either a rounded punch or a sharp-edged punch than are the integrally molded polyethylene webs but are more resistant to deflection.
For example, a two-pound weight resting in the center of a Frisbee having a web thickness of about .055" causes a deflec-tion of about .4411. A laminated mylar web attached to the outer ring of the same type of Frisbee~after the integrally olded web has been removed is deflected only about .l6", which po1~h~$~
iS about 36% of the deflection of the much thicker ~ e~ Ls~ ~-web. It has been suggested that too thin a web (of the inte-grally molded type) is deflec-ted too much in flight, which inter-fers with its flying charac-teristics. The much more rigid we~
of taut mylar avoids this disadvantage.
Figs. 6-8 show radial spoilers that may be used instead of the spoilers 23 that extend partly in a radial direction and partLy tangen~ially. The spoilers in Figs. 6-8 are integrally molded on the upper surface o the annular member 21. In Fig.6 the spoilers 32 have a rectangular cross section; in Fig. 7 the spoilers 33 have a rounded, and in fact, a sinusoidal, cross section; and in Fig. 8 the spoilers 34 have a triangular cross section. The spoilers should be balanced about the axis of t~e disc but they may or may not be uniformly angularly spaced apart. For example, the spoilers as shown in any of Figs. ~-8 could be separated into three groups with those in the first group having one angular spacing, those in the second group having a second spacing, and those in the third group having -l2-1 87 ~

a third spacing. The three spacings could be selected to set up sound vibrations o the proper relative frequencies to produce, for example, C, E, and G notes, resulting in a C major chord.
The radial spoilers also strengthen the ring 21 by act-ing as rip stops for any rip in the tangential direction and within the radial extent of the spoilers~ The radial spoilers also reduce the tendency to follow a path that curls at the Fris6~ içce end of a flight, as ~ et are wont to do.
Figs. 9-11 show discs 21 with snap attactments. In Fig. 9 an external snap-on cover 36 fits over the down-turned rim of the ring 21 to protect it and to add weight at the periphery of the disc. The cover 36 also changes the curvature o the outer surface of the air foil. However, the original cross section o the ring 21 may be formed with a flatter air foil so that the snap-on cover provides only an ordinary amount of curvature. In addition, the cover 36 may be of uniform thick-ness throughout to avoid changing the air foil shape.
Fig. 10 also shows a snap-on external ring 37 that is generally hollow and contains one or more light-emitting diodes 38 and a printed circuit 39 to control the light of the L.E.D.'s to produce an interesting stroboscopic effect at night. Except for the electrical components, the ring 37 is hollow, which pro-vides enough bouyancy to be certain that the disc will float if it falls into water.
Fig. 11 shows a disc with two snap-in rings 41 and 42 for 8 ~ 4 extra weight.' The rings may be graded in some specific ratio, such as 10 gram intervals. For example, the ring 41 may be representative of 10 gram, 20 gram, and 30 gram weights. The ring 42 is additionally weighted by a loop of steel 43 that is .25" wide and .010" to .020l' thick. In fact the ring 21 may be molded of polyethylene. The snap-in rings are molded to have a tight interference fit with the down-turned rim of the ring 21. Also, the'inner surfaces of the ring toes in slightly.
The toe in angle is known as the Angle of Francioni.
' Fig. 12 shows a ring 21 with a steel band 44 molded into it to add weight. The total weight may be 200 grams.
The weighted rings 21 in Figs~ 11 and '12 are less in-Fr ls~ s c sclined to remain deformed than are regular~ ~, If de-formed in any direction, the spring 'back immediately into their proper shape, This minimizes wobbling during ~light.
Figo 12 also illustrates an arrangement for printing infor-mation photographically on the web 22. The web may be photo-sensitized mylar coated on both surfaces with sheets of opaque paper 46 and 47 attached by pressure-sensitive adhesive to the mylar. The top paper 46 layer is peeled off to allow the photo-sensitized mylar to be exposed to the desired image, and then the latent image is developed. -The bottom paper 47 is prefer-ably removed before the latent image in the mylar is developed.
Fig. 13 illustrates still another way to attach the web 22 to the ring 21. An annular ring 48 of paper is coated top and bottom with pressure-sensitive cement. It is then placed ~ :1 6187~ 1 on the ring ~1 to be affixed to the top surface of the rin~ 48. ~ ¦
Fig. 14 is an enlarged view of just the innermost part of the outer ring 21 similar to that in Fig. 1, for example but showing only the part ~o which the web is attached. The web, indicated by reference numeral 49, includes a central disc 51 of artwor~, such as a'photograph, print drawing, painting, etc. on any suitable material, such as a plastic photographic film base or even paper. The central disc 51 is entirely enclosed by two laminated discs 52 and 53 of somewhat larger diameter than the disc 51. The laminated disc 52 is a sheet of extruded polyester and polyethylene. The layer 54 of polyester is on the outside and is ~pprox-imately 005!' thiclc, while the layer 56 of polyethylene is approximately, c t~_~a5~-thick and is on the inside~in contact with the disc 51. The other extruded disc 53 has corlesponding layers of 005~ thick polyester 57 and .002" thiclc polyethylene 58, and an annular band of the edges of the poly-ethylcene layers 56 and 58 are sealed together to encase the disc 51 snugly.
The annular peripheral region of the polyester layer 54 is sealed adhesively to the inner annular perimeter of the upper surface of the ring 21 by coating with neoprene plus 1, 1, l-trichloroethane the surfaces to be joined. The procedure has been described previously and need not be repeated. Fig. 14 also shows t~o members 59 and 61 to apply pressure to ~' join the disc 49 to the ring 21. The member ~ is a disc of steel or other suitable material capable of withstanding high pressure and has an up-turned rim 62 with a frusto-conical upper surface 63 having an included angle ~ of between 150 and 180. The outer peripheral region of the layer 54 and the inner peripheral region of the ring 21 are pressed to~ther by the members 59 and 61. The frusto-collical chape of the surface 63 helps to stretch the disc 49 taut so that it will remain that way after the pressure is removed.
~ hile this invention has been described in terms of specific embodi-ments, those skilled in the art will be aware of further modi~ications that can be made within the true scope of the invention

Claims (40)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A flying disc comprising an annular member defining an open inner area and having an airfoil shaped cross section, and a thin sheet having an outer perimeter affixed to said annular member to cover the open inner area, characterised in that the thin sheet is of flexible plastics material tautly affixed in position and in that the annular member and the thin sheet are of different materials.

2. The disc of claim 1 wherein the air-foil shaped cross-section of the annular member is defined by different curvature on opposite surfaces, the member having a thickness that depends on the radial point at which the thickness is measured;
and wherein the said thin sheet has a lighter weight for a volume bounded by an area of unit size and by the thickness of said sheet at said area than the average weight of a volume of said annular member bounded by an area of said unit size and by the thickness of said annular member at the thickest point thereof.

3. The disc of claim 1 comprising means to hold said thin sheet tautly in position covering said open inner area.

4. The disc of any one of claims 1 to 3 in which said sheet is mylar having a thickness between approximately 0.0075"
and approximately 0.011".

5. The disc of any one of claims 1 to 3 in which said sheet is Lexan having a thickness between approximately 0.0751' and approximately 0.011".

6. The disc of any one of claims 1 to 3 in which said sheet has a plurality of spaced holes near its perimeter and said annular member has a plurality of correspondingly spaced pins each extending through one of said holes, respectively, to hold said sheet in place on said annular member.

7. The disc of any one of claims 1 to 3 in which the peripheral region of said sheet is adhesively attached to said annular member.

8. The disc of any one of claims 1 to 3 in which said annular member has a plurality of pins located adjacent the inner perimeter thereof and extending generally parallel to the axis of said annular member, and said thin sheet has a corres-ponding plurality of apertures to fit over and engage said pins.

9. The disc of any one of claims 1 to 3 in which said annular member has a plurality of pins located adjacent the inner perimeter thereof and extending generally parallel to the axis of said annular member, and said thin sheet has a corres-ponding plurality of apertures to fit over and engage said pins, and in which said pins are deformed to hold said thin sheet securely in place thereon.

10. The disc of any one of claims 1 to 3 in which said annular member has a plurality of pins located adjacent the inner perimeter thereof and extending generally parallel to the axis of said annular member, said thin sheet has a corresponding plurality of apertures to fit over and engage said pins, and in which said pins are deformed at their outer ends to form heads thereon of larger cross-sectional dimension than the holes in said thin sheet to retain said sheet in place on said annular member.

11. The disc of any one of claims 1 to 3 in which said thin sheet comprises a base for graphic representations.

12. The disc of any one of claims 1 to 3 in which said thin sheet has a layer of photo-sensitive material on one surface of said sheet.

13. The disc of any one of claims 1 to 3 in which said thin sheet has a layer of photo-sensitive material on one surface of said sheet, and in which said layer of photo-sensitive material is covered with a peelable layer of opaque material.

14. The disc of any one of claims 1 to 3 in which said thin sheet has a layer of photo-sensitive material on one surface of said sheet, in which said layer of photo-sensitive material is covered with a peelable layer of opaque material, and comprising a second layer of opaque material on the other surface of said sheet.

15. The disc of any one of claims 1 to 3 comprising a reflective layer on one surface thereof.

16. The disc of any one of claims 1 to 3 in which said thin sheet comprises a Fresnel lens.

17. The disc of any one of claims 1 to 3 comprising balanced weighting means near the outer perimeter of said annular member.

18. The disc of claim 1 wherein the said thin sheet comprises a perimeter in substantially one plane;
said annular member is curved in one direction from said plane, whereby said sheet and said annular member combine to define a dish-shaped structure having a concave side and a convex side, said annular member comprising a rounded cross-section that is thickest at an annular position between the edge of said annular member and said perimeter of said thin sheet; and the disc also comprising a plurality of spoilers on said convex side, each of said spoilers extending in a direction comprising a radial component.

19. The disc of claim 18 in which said spoilers extend radially with respect to the axis of said disc.

20. The disc of claim 18 in which said spoilers have a generally rectangular cross-section.

21. The disc of claim 18 in which said spoilers have an undulating exposed surface.

22. The disc of claim 18 in which said spoilers have a serrate cross-section.

23. The disc of claim 18 in which said spoilers extend over the perimeter of said central sheet.

24. The disc of claim 18 in which said spoilers are defined by grooves in the surface of said convex side.

25. The disc of claim 24 in which said grooves extend radially.

26. The disc of claim 18 in which said spoilers comprise ridges raised above the adjacent surface of said convex side.

27. The disc of claim 18 in which said thin sheet is a web of material having greater puncture resistance for a given thickness than the material of said annular section.

28. The disc of claim 27 in which said web is laminated comprising a layer of polyester and a layer of polyethylene, said annular member is an annular ring of molded polyethylene, and the peripheral region of said polyester layer is adhesively attached to an inner annular surface portion of said annular ring.

29. The disc of claim 28 in which at least one of said layers of the laminated web is transparent.

30. The disc of claim 18 comprising a snap-on outer ring removably attached to the outer perimeter of said dish-shaped structure.

31. The disc of claim 30 in which said snap-on outer ring has a ridged inwardly facing surface and the outer perimeter of said dish-shaped structure has a ridged surface that interlocks with the ridged inwardly facing surface of said ring.

32. The disc of claim 30 in which said snap-on outer ring is curved to fit around and substantially enclose the outer perimeter of said dish-shaped structure.

33. The disc of claim 30 in which said snap-on outer ring is transparent and comprises light-emitting means.

34. The disc of claim 18 comprising at least one removable ring fitted into said annular member to be held in place therein.

35. The disc of claim 34 in which said removable ring comprises a metal ring within a plastic cover.

36. The disc of claim 34 comprising a nested plurality of removable rings, the outermost of said nested plurality being fitted into the inwardly facing surface of said annular member to be held thereby.

37. The disc of claim 18 comprising a ring having a specific gravity such that the specific gravity of the entire disc is less than that of water.

38. The disc of claim 18 comprising an additional annular ring coated with adhesive on both radial surfaces and adherently joined by such adhesive to the outer perimeter of said thin sheet and the inner perimeter of said annular member.

39. The method of attaching a peripheral region of a thin sheet polyester disc to an inner peripheral region of a polyethylene annular ring member comprising the steps of:
coating said peripheral region of said disc with an adhesive in liquid form comprising neoprene and 1,1,1-trichloroethane solvent;
oxidizing said inner peripheral region of said ring;
coating the resultant oxidized region with said adhesive;
allowing said adhesive on said disc and said ring to dry from approximately fifteen minutes to three hours;
and pressing the adhesive coated region of said disc against the adhesive-coated region of said ring with a pressure of between approximately 250 and 1000 pounds per square inch.

40. The method of claim 39 comprising stretching said inner peripheral region of said ring and the juxtaposed annular portion of said disc over a frusto-conical surface having an included angle of between approximately 150° and 180°
with said ring between said frusto-conical surface and said disc while applying said pressure.