Okay, here's a test that you might be able to do then: How effective are the various fins (using the 2 strokes mentioned) under a larger load, ie using heavy doubles with multiple stages. I believe the analogy usually used is that with gears in a car - ie the lower gears aren't exactly the fastest, but can move the car from a standstill.
Here's a scenario: You're loaded up with all your PJ gear and need to tow an unconscious diver from the water. Which fin would you think would be the most effective to move you through the water?
Speed isn't the only measure of the effectivity of a fin after all. I personally prefer greater control in the water than zipping from point A to B in a hurry.
Robert, I'm sure you really enjoy the Jet Fins, and feel that they are the best fin available. I can understand that, as they are a very good and comfortable fin, especially the Lightning Jet Fins. However, they were introduced in 1965 in the USA, and I began developing my scoop fin concept in 1968 while in the USAF in Okinawa and Korea. The USAF did not gain access to the Jet Fin until I was in the USAF Reserves in 1972. That is when I was issued a pair of Scubapro Lightning Jet Fins. Prior to that, and actually during all my USAF days, I was using a pair of modified White Stag "Super Stag Fins". The modification was to get the scoop fin from this fin. I used it on training water missions, and on one memorable actual mission out of Kunsan Air Base, Korea.
Drado, here is the write-up of one of my missions, which is close to what you described above. It was a helicopter deployment into the Yellow Sea off the east coast of Korea.
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Copyright 2012, John C. Ratliff
T-Sam-Sam[/U]
In Korean, the word “sam” means “three.” Their numbers sound like this for one, two, three...to ten. “Ill,” “Eee,” “Sam,” “Saw,” “Oh,” “Yuk,” “Chil,” “Pal,” “Koo,” “Sip.” So when we heard that a T-33 was missing, we heard from the Koreans “T” “Sam” “Sam.” The T-33 is a training jet, with straight wings rather than the usual (for jets) swept wings. This is an older design, and was meant to be a sub-sonic flying machine. But it handled well, and was used by the USAF for many years as a trainer. The Koreans used it in the same manner, but their next better bird was the venerable F-86. When we heard that the T-33 was missing after declaring an emergency, and scrambled. But it did not land.
It was quite a day, too. Early spring had produced “one of those days,” where the cold air was still after a storm, and the clouds were really a high fog, I loaded our water gear, just in case. Major Kekuna was our pilot for the day, and we headed out following the path the plane would have taken had it been on final in an emergency. Here’s how I described the mission in a letter home:
March 17, 1969
Dear Mom, Dad, Skip, Bill & Ken:
In my last letter, I told of our water training that we conducted a week ago last Thursday. Thursday last, on a mission we would rather wouldn't happen, we tested our procedures and found them very effective. It was stormy on the 13th of March when we received the scramble call. A T-33 jet flying from Kwanju had called into Kwanju with engine troubles. We scrambled with the fire suppression kit and orbited near the runway. A storm just off the end of the runway put visibility down to zero, with some icing. The ROKAF T-33 never landed, and Kunsan AB was unable to establish radar or radio contact. We landed, I got my skin diving gear, then went out for a search. After 15 minutes we found the victims life raft and helmets. No sign of life was observed. We landed in a mud flat, where the pilots and flight engineer (FE) put on exposure suits and I put on diving equipment. Then we went out for the recovery. The rest is in the rough draft statement I wrote for the ROKAF Accident Investigation Board.
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1625/JCR, Mission # Det 3, 41st ARRWg 007, March 13, 1969
I had very little visual contact with the victims or their equipment before my deployment into the water because I was busy putting on my diving equipment. I was in the door about 10 seconds before TSgt Maxwell tapped me out of the helicopter. The helicopter was in about a 15 foot Hoover when I jumped.
After entering the water, I swam to the victim and tried to lift him to the water's surface. He was too heavy. Underwater visibility was about six (6) inches. It was hard to determine which part of the victim (arm or leg) I was holding. It was his arm. I found one of his Capewell quick releases for his parachute, which was deployed in the water, and released it. Then I turned him over to get to the other release, and released it also. I tried to blow up his LPU, but couldn't find them. The victim's face was bloody and he didn't have a helmet on. After releasing the parachute, I swam him away from his life raft and parachute. I had to cut parachute suspension lines which ere tangled around his feet and my swim fins and the tether to his life raft. I signaled for a helicopter pickup of the first victim. The HH-43 helicopter lowered a rescue seat to me, which I disconnected, and hooked the hoist's hook to the victim's parachute harness.
After the first victim was aboard the helicopter, I looked around for the other victim. I saw a helmet, swam to it towing the rescue seat, but the victim wasn't there. I strapped the helmet to the seat. The second helicopter guided me to the second victim.
I swam to the second victim, swimming around his parachute to keep from getting tangled in the lines. I found some suspension lines beside the victim and cut them. I then cut the risers (on the victim's right side, I believe), disconnected the Capewell quick release from the parachute risers on the other side, and checked to see if the victim was tangled in lines. He was not tangled. I also tried to locate his LPU to plow them up, but again couldn't find them. Then I signaled for a second hoist pickup, which was accomplished the same manner as the first.
When the second victim was aboard, I swam to the rescue seat, strapped myself into it, and I was picked up.
Headquarters
Republic of Korea Air Force
Seoul, Korea
Letter of Appreciation
May 23, 1969
John C. Ratliff, A1C, AF18958305
Det 11, 41 ARRWg.
Kun-San AB.
I wish to take this opportunity to extend my sincere appreciation for the exceptionally outstanding and distinguished service rendered to our wing at the time of the unfortunate aircraft accident of a Korean Air Force T-33A in which two pilots were killed during March 13, 1969.
At that time, you immediately took off from Kun-San AB by H-43 and wee successful in locating the accident debris.
In addition, in spite of hazardous weather you courageously lowered yourself to the sea water below and successfully recovered the victims displaying a lack of concern for your own safety.
In recognition of, and with gratitude for, this outstanding service, I present this letter of appreciation with my best wishes for continuous development and success in the future.
Brig. General, Rim Soon-Hyuk
3rd Training Wing, ROKAF
Commander
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We found out later that the pilots had been ejected through their canopy upon impact, and probably died instantly of head injuries from that ejection. They had a malfunctioning altimeter, and when they came through the cloud cover thought they were about 2,000 feet off the water. In fact, they were less than 500 feet in altitude, and flew the plane into the water because of the optical illusion caused by the glassy smooth sea surface.
My scoop fin design worked very well on this mission. I suspect the Lightning Jet Fin would also have done well. But I'm not sure about the original Jet Fins, which were shorter and somewhat stiffer, and the 1972 Scubapro catalog showed only one size (slightly small for me with 1/4 inch boots on). This mission was not difficult, as the water was silky smooth (which resulted in the crash in the first place), with no current or waves. But it was about 200 yards between the two victims.
I took those White Stag Super Stag fins on parascuba jumps, and helicopter deployments throughout the late 1960s through the 1980s, when I began modifying the Mares fins. I went through three different membranes for that fin, and could use them tomorrow if I wanted.
One point on any fin, is that if they have a fin strap, you want that strap routed backwards through the buckle so that there is an "catch" point from the excess strap (it is tucked behind the strap). This helps in kelp too, but was really necessary where there are parachute lines in the water.
John