Post by SeaRat on Nov 29, 2005 22:08:53 GMT -8
As stated in the Viking thread below, I wanted to put one thread together about the scoop fin (my name) idea, which I've now been diving continuously since 1968. This is not something you can get in any catelog, as these are home-made. Isn't that the tradition of the Vintage Diver anyway? So, here's my 1970 slides and explaination of the scoop fin.
Theory[/U]
The theory of the scoop fin is simple; the fin increases dramatically both the volume of water moved, and the force vector pushing the diver backwards. Here is my Disclosure of Invention, dated 1 July 1971:
Well, that was the disclosure. Here's the drawing that went with the disclosure:
Theory[/U]
The theory of the scoop fin is simple; the fin increases dramatically both the volume of water moved, and the force vector pushing the diver backwards. Here is my Disclosure of Invention, dated 1 July 1971:
On the market today are many swim fins, most of which have the same basic design. They have a thick, flat rubber blade which is further stiffened by rubber ribs. Two ribs are placed on the outside edges of the blade, and the blade area in usually further reinforced by one or two ribs in the center of the blade. The fins are made in varying degrees of flexibility to match the strength of the swimmer. However, each of these basic designs present an essentially flat blade to the water. In the stiff "competition" fins, it's almost like moving a piece of plywood through the water. The ribs of these models are used to channel the water "down" the fins. However, much of the water seems to flow or "fall" off to the side instead of traveling rearward to propel the diver. There are two or three fins on the market which offer improved variations of this basic design. One opens the blade for a couple of inches below the toe and puts a hinged blade behind. The water flows through the blade's opening, opens the hinged blade and flows rearward. Another excellent variation is a fin which uses two overlapping blades. Water is forced between the two fdins and "jetted" to the rear through the opening The disadvantage of these variations is that they work only on one protion of the kick, the downstroke. On the upstroke, the vent is closed and the opening is wrongly oriented. The only difference between today's fin and those fo fifteen years ago, excepting the two variations above, is that they are somewhat larger, and the foot pockets are larger and more comfortable.
A little over three years ago, I began looking into the possibilities of different swim fin designs. I also spent some hours watching aquarium fish swim, paying close attention to the movements of their tail fins. What most impressed me about the swimming movements of te fish was that the tail fin never persented a flat surface to the water. Rather, the outside spines of the tail are fairly rigid while the inner "blade" area is flexible. This allows the fin to "cup" or "scoop" more water at a given rib interval.
I immediately set about modifying a pair of fins which had a flat plastic blade. I cut the inside of the blade out, leaving an inch or so for the outside ribs. I then had a sheet metal, horseshoe-shaped cover made to fit over the ribs as a backing for a soft, flexible rubber blade. For the rubber I used an old car innertube. These fins were tested, first in a swimming pool, then at a beach and finally on at least two open sea dives, one to 70 feet and one to a depth of over a hundred feet. In the pool, over a distance of twenty yards, tthey appeared to give somewhat greater speed with less effort. They worked very well and were comfortable on all open sea dives, the only drawback being that when the metal horseshoe was bent while walking on coral after the dive, the fin had to be taken off and straightened.
Since 1968, when these fins were made, I have also modified two other pair of fins, each of different brands. Each has flexibel ribs, thus differnig fromthe first pair. Both have shown excellent handling qualities, improved comfort and performance. In addition to this, I have found that the fins, even when forcefully slapped down onthe water's surface, give very little splash. In the swimming position, when the fin is brought to the surface of the water onthe upstroke, the blade is flexed down. At the surface, when the downstroke begins, the blade is stationary until the ribs pass its lowest point, at which time it flips and scoops downward. If the outside ribs come a couple of inches out of the water on the upstroke, the flexible blade is still underwater. Only the ribs break the surface and splash on the downstroke. If the whole fin is brought completely out of the water, the flexible blade sohtens the splash by giving away when it hits the water's surface.
SUMMARY
Instead of a fin blade which is flat, this fin is designed to have fairly stiff outer ribs, lighter inner ribs ()or none at all) and a very fglexible, rubber impregnated canvass blade which is pulled ight at the end of the footpocket, but generally gets looser until at the fin's tip, the canvass is almost semi-circular in shape. On the stroke, the canvass flexes away from the direction of the stroke, thus giving more surface area in contact with the water, more volume of water under the control of the fin's outer ribs and a better angle of attack to the fgin. The canvass flips at the end of the storke nd therefre is useful on both the upstroke and the downstroke of the diver's kick. In addition, because of the fin's design there is much less splash when the water's surface in brokesn.
Signed,
John C. Ratliff
A little over three years ago, I began looking into the possibilities of different swim fin designs. I also spent some hours watching aquarium fish swim, paying close attention to the movements of their tail fins. What most impressed me about the swimming movements of te fish was that the tail fin never persented a flat surface to the water. Rather, the outside spines of the tail are fairly rigid while the inner "blade" area is flexible. This allows the fin to "cup" or "scoop" more water at a given rib interval.
I immediately set about modifying a pair of fins which had a flat plastic blade. I cut the inside of the blade out, leaving an inch or so for the outside ribs. I then had a sheet metal, horseshoe-shaped cover made to fit over the ribs as a backing for a soft, flexible rubber blade. For the rubber I used an old car innertube. These fins were tested, first in a swimming pool, then at a beach and finally on at least two open sea dives, one to 70 feet and one to a depth of over a hundred feet. In the pool, over a distance of twenty yards, tthey appeared to give somewhat greater speed with less effort. They worked very well and were comfortable on all open sea dives, the only drawback being that when the metal horseshoe was bent while walking on coral after the dive, the fin had to be taken off and straightened.
Since 1968, when these fins were made, I have also modified two other pair of fins, each of different brands. Each has flexibel ribs, thus differnig fromthe first pair. Both have shown excellent handling qualities, improved comfort and performance. In addition to this, I have found that the fins, even when forcefully slapped down onthe water's surface, give very little splash. In the swimming position, when the fin is brought to the surface of the water onthe upstroke, the blade is flexed down. At the surface, when the downstroke begins, the blade is stationary until the ribs pass its lowest point, at which time it flips and scoops downward. If the outside ribs come a couple of inches out of the water on the upstroke, the flexible blade is still underwater. Only the ribs break the surface and splash on the downstroke. If the whole fin is brought completely out of the water, the flexible blade sohtens the splash by giving away when it hits the water's surface.
SUMMARY
Instead of a fin blade which is flat, this fin is designed to have fairly stiff outer ribs, lighter inner ribs ()or none at all) and a very fglexible, rubber impregnated canvass blade which is pulled ight at the end of the footpocket, but generally gets looser until at the fin's tip, the canvass is almost semi-circular in shape. On the stroke, the canvass flexes away from the direction of the stroke, thus giving more surface area in contact with the water, more volume of water under the control of the fin's outer ribs and a better angle of attack to the fgin. The canvass flips at the end of the storke nd therefre is useful on both the upstroke and the downstroke of the diver's kick. In addition, because of the fin's design there is much less splash when the water's surface in brokesn.
Signed,
John C. Ratliff
Well, that was the disclosure. Here's the drawing that went with the disclosure:
.....maybe we should have some races 
