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Post by mossback on Dec 21, 2005 19:17:56 GMT -8
Is all this string for a specific reason? I mean, how much difference will there be for a vintage diver if the diver uses stock fins or mod'd fins? I've seen the split fins at the LDS here and first thing I think of is "another gimmick".
Are ease and less effort or just more speed the goals here? How does that equate to air usage?
I can see the advantage if scoops add to one's air supply by not using up as much air to go the same distance........but that would really be a signifiant (sp) difference between stock (say the old power plana's or even the old Jets) and John's scoops.
Is there that much difference to add say 5 minutes of air to my usage? That is what I'd be interested in knowing.
I like to cruise lesurely and look and photograph stuff. Very rarely do I have a need for fast acceleration and then I expect to burn a heap of air.
I appreciate John's work and efforts and his belief in his invention and I also think he is the real life Mike Nelson of diving , but how will his scoop fins affect my diving?
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Post by SeaRat on Dec 21, 2005 20:10:39 GMT -8
Mossback, In a word, "cramps"--that is the difference between the Duckfeet (especially the AMF Voit version, or the USD Aqualung fin) and the scoop fin. In the US Navy Underwater Swimmer's School in Key West, we had to make both surface and underwater swims. In the surface swims, we could see where we were going, but the underwater swims were compass swims. We swam 500, 1000, and 1500 yards in those swims. I wore my own Duckfeet, and wore them upside down. The divers wearing the USD Aqualung fins suffered because of the stiffness of the blade. I began this quest in 1968 because of poorly designed foot pockets, and the power blades, causing cramps in long swims. At the time I was snorkeling and scuba diving around Okinawa reefs, and we would swim out 1/4 mile to the reef off Naha Air Base to do our snorkeling or diving. The issued fins were terrible, much worse than the older Swimmaster Duckfeet, and on long swims many would experience foot cramps. I figured there had to be a better way, and developed the scoop fin with that in mind. With the scoop adaptation to the flat blade design, the fin is much easier on the feet no matter how far you swim. But it does give better performance over the whole spectrum of performance points for a fin. Basically, because the angle of attack is so much better (see the diagram on page 1), there is less pressure on the foot, and better performance for the fin in pushing water behind the diver. Here is one of the divers using the USD Aqualung fin in the US Navy School for Underwater Swimmers: Nemrod, If you want to make the modificaton for the scoop fin, what I've done is to take measurements off a center line. At the toe of the fin, I measure the actual measurements between the two outside ribs. I then take the center measurement to get the length, but cut it a bit longer just in case I need the extra material. I measure either side of the centerline, half the measured distance across the toe of the fin. For the second measurement, I use a piece of string, and place it across the outside part of the fin between the two ribs, with the bow I want in the material (usually about a semi-circle). I use half that measurement off the centerline, and mark the material perpendicular to the centerline. I then connect the outside marks and cut the material. That should get you the type of scoop fin you will like. John
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Post by nemrod on Dec 22, 2005 1:22:50 GMT -8
"I like to cruise lesurely and look and photograph stuff. Very rarely do I have a need for fast acceleration and then I expect to burn a heap of air."
These ideas may not be a fit for you then. I don't think we are demanding a person put scoops in their fins, lol. The above quotation does not fit me, especially in the past. Some people see diving as a hobby for relaxation to "cruise lesurely" and some see it as a sport for adventure. I am in the later and I may well need rapid acceleration and speed, the ability to buck a current, push my video camera agaisnt the stream, tow my buddy should they become ill, shove myself and all my equipment through the water at decent speed. Not only that, a more efficent or faster fin may be a goal but a more comfortable and practical fin may also be a goal. AND, I think your missing the point, we are modifying the fins as an experiment so we can compare identical fins with only one difference, the split or the scoop--one at a time. This was never a suggestion that divers modify their fins for diving, we are modifying fins that are on their last leg anyways to use as an EXPERIMENT. I and I don't think SeaRat intended or meant for you to cut up your fins and on another point, if the split is a gimmick then what about the "jets" in Jet fins and Rocket fins and all that--gimmick! These are just experiments using somewhat antedotal methods and trial and error. AND further since SeaRat has been doing all this for an age --it is therefore a continuing vintage experiment that has spanned what--about 40 years huh SeaRat? James
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Post by mossback on Dec 22, 2005 8:19:40 GMT -8
Nemrod
I think you have partially misunderstood my comments.
I consider diving in any form an adventure, I however, at my age am not interested in blasting thru the water unless the situation calls for it, i.e. the current along the Palancar wall in Cozumel, chasing after a turtle at the stetson bank in the gulf, etc.
My first pair of fins were Voit vikings, they were great but I soon learned that they would work me to death when I needed the extra push. When I aquired a set of Jets from a Marine buddy who rotated back to the states, I quickly understood why they were called Jets!
Yeah, they were hard to start, but boy could you sail thru the water. I used those until I aquired a set of Power Plana's in the mid 80's that I've been using ever since.......
They are ok for crusing and the power is there for a fast push if I need them (with a short stroke by the way) and I don't remember ever getting cramps. I've used them in that current I spoke about, towing my then 12 year old around like a sack of potatos while he just eyeballed everything and chasing that turtle at the flower gardens a year ago.......with my same son, grown now, following behind me using split fins.....his d rings, fancy scubapro vest etc. dragging thru the water..........I out distanced him.........he was in much better condition that I also as I darn near emptied my tank after that, over breathing my reg etc.
The scoop sounds interesting and has promise, perhaps I would not have exerted so much energy and burned so much air but y'alls experments don't yet document any type of energy usage.
Don't know how you would do that, save for air usage vs time and stress conditions of dive.
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Post by nemrod on Dec 22, 2005 9:56:34 GMT -8
I have some Power Plana graphites from the mid 80s, I don't consider them vintage for myself, others may vary. They are still my most used fin when I am not in "vintage mode". I think my UDTs are my primary Vintage fin. I notice in the photo submitted above by SeaRat the diver has UDT fins on. That is an idea, UDT vs Plana, in the pool at high noon!
An instrumented robotic manikin in a hydro tunnel that can measure among other things caloric energy consumption would cerntainly settle all this--maybe---but I cannot afford one and my main interest at this time of continuing this experiment is to try SeaRats idea out in the pool as a continuation of his long going vintage fin experiment. I don't expect to measure air consumption and---Power Planas are not vintage even at the Flower Gardens, LOL--and if and when I buy some Apollos they will not be part of my vintage diving. I don't always dive vintage--I have modern gear--for the times and places it is called for. James
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Post by nemrod on Dec 31, 2005 17:20:35 GMT -8
SeaRat, I finally got around to cutting my UDT and SkinDivers. The first experiment and it is an EXPERIMENT with these junk (rotten) fins will be splits. The rubber is old and cracked but they should work for the experiment. The first step is to swim them agaisnt unmodified UDT and SkinDiver fins. This first test will be with SPLITS. I was not into making them pretty. This is a test, not for actual diving, pool tests only. When the tests are done they will be THROWN away. There is no giant purpose to this other than fooling around to see if there are any decernable difference when comparing identical fins with and without splits. After this I will attempt to insert a scoop type membrane into the UDT fins and then swim them agaisnt unmodified fins. Again, since I am throwing them away, there is no reason to go into great effort to make them pretty. Maybe I can get them in the pool next weekend. I will send pics to Linda to insert if she can get to it of the split fins. I just used a Band Saw on the UDT and on the SkinDiver I drilled a hole at the end of the split and then cut with a razor knife. These are actual vintage fins, not Power Planas or Super Jets or Apollos or ScubaPro Splits or other non vintage scuba diver fins. My swims will be underwater in basic gear at as constant an effort as I can manage and timed by my wife. I will not use my arms or swim on the surface. James
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Post by SeaRat on Jan 1, 2006 0:29:05 GMT -8
Nemrod,
After you test them this way, you might want to cut the UDT fins up closer to the foot pocket. But you should see some effect this way too.
I swam last week three times with different fins, and will report it here later. It's pretty late right now, and I just watched the ball drop.
HAPPY NEW YEAR EVERYONE!!!
SeaRat
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Post by nemrod on Jan 1, 2006 16:39:50 GMT -8
John, the reasoning behind not cutting the UDT all the way is that one of my thoughts many posts back was to leave the central rib half length to aid stiffness. It seems that one of the complaints about split designs is lack of acceleration due to insufficient stiffness. Well, we all know the UDT is stiff so I wanted to try it this way. Yeah, I can cut it all the way after the first test. I suspect these fins may not last the duration of testing--anyone have some nice UDT fins I can cut up--lol?
Did anyone see the rescue action in the floods where the rescue diver was wearing the blue and yellow Churchill fins in Calif. --on FOX news.
I stil love my UDT fins I got from Dan. I think for vintage diving they are still king of the hill at least for warmer water diving. I can see how fellows needing serious boots might prefer a Jet or such as that. Think about it--as a vintage diver we don't have much choice of fins. Used--ebay SkinDivers and Vikings, Jet fins and Rocket fins are vintage or vintage like and the Churchills, UDT such as sold on this site are of course vintage type but anything else is not really very vintage that I see commonly available. Sorry, clear or neon Power Planas may be great fins, I have some black graphite ones but they are not vintage in appearance, just don't feel right with them on in my vintage gear and modern Planas on my toesies. James
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Post by mossback on Jan 1, 2006 17:28:44 GMT -8
James and anyone else who would be in the market.....ScubaPro still sells the Jet Fin......pull up their site.........second or third from the bottom of the list of different types of fins.....about 2 models under their new split Super jets are the old tried and true JET Fins........still for sale.......I called one LDS for price.........over $100 per pair........forget ebay, which is a gamble on old fins.....I've a 5 dollar pair of jets that are junk....but won another pair for 8 dollars that are pretty new...but for Brand New out of the manufactures box JET fins......Leisure Pro has them for $69.95.......at least last month they were that price..........ahem............
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Post by SeaRat on Jan 1, 2006 18:27:04 GMT -8
The interesting aspect of the ScubaPro Jet Fin is that it has been in continuous production since 1965 (according to the 1986 catelog I am reading right now. The vents are there to "jet" water backwards out of what ScubaPro says is the "dead area" of the fin, or the area that doesn't provide propulsion. Their catelog explaination is too long to quote in total, but I will quote part of the 1972 catelog explaination: ScuabPro has about 6 pages of explainations of the Jet Fin concept (with the original, the Lightning Jet Fins, and the Sea Wing) in their 1986 catelog. They do say, concerning the Lightning "Jet Fin": It is interesting to note that Cousteau's book, World Without Sun was published in 1964. It documents the Conshelf II project in 1963. Their divers are using Jet Fins exclusively throughout this book, and throughout the movie of the same name. Georges Beuchat, of Marseille, France, filed his original patent on April 25, 1962, and apparently produced the fin in that time frame. His US Patent, #3,183,529 was granted May 18, 1965. I have a pair of Lightning Jet Fins, and swam them last week along with my original UDT Duckfeet. Both performed well, although the Duckfeet would not fit in my fin boots (I used simple socks). I noticed immediately that there is a dead area in the Jet Fins stroke that is on the upstroke, which I had to get used to. The UDT Duckfeet really did not have this dead area, but did not have quite the thrust of the Lightning Jet Fin, which was a very large fin (Super Jet Fin, Shoe sizes 10-14). The Duckfeet fins are what I would consider "vintage" fins, as that design began in the 1950s, and was prevalent in the 1960s. The Duckfeet are a very nice fin. I tried them both right-side up and up-side down in the pool last week, and now do prefer them right-side up. This has more to do with their fit, as I was wearing thin socks, and not the rubber "booties" we had in the U.S. Navy Underwater Swimmer's School. They provided very adequate thrust when I wanted it, and still responded after all these years (my pair have some very minor checking on the heel strap, and I've had to use Shoe Goo on two tears on the outer ribs). But the gum rubber is still pliable on these fins, and I enjoyed using them in the pool. The Jet Fin, while in the 1960s era, represented a departure from the truely "vintage" fins. While ScubaPro was promoting the blade design, equally important was the foot pocket design, which supported the foot all the way to the heel, and is copied by virtually every modern fin that came after it (except full-foot fins). This, in my opinion, was a major advance in helping divers avoid foot cramps. I got these when I was in the US Air Force, and still have them. They have not deteriorated one bit, except for some minor cracking in the strap. What is interesting is that they sold for $62 in 1986. What is that in today's dollars? And yet, we can still get them for just over $100 per pair retail, and $69 from LeisurePro? That sounds like a very good deal from where I sit. Here's the ScubaPro Lightning Jet Fin I've had since the latter 1970s. Compared to the scoop design, though, the Jet Fin lacks good propulsion on the upstroke. It is great on the down stroke, and a very good performer for the frog kick (more on that later). But not on the upstroke in a crawl kick. The scoop fin works both directions almost equally (see the diagram at the beginning of this thread). SeaRat
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Post by Ron Hearn on Jan 1, 2006 21:27:23 GMT -8
Hi SeaRat
Man you sure are vinatge LOL. What are the lases for on the fins, to ketch fish.
Ron
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Post by SeaRat on Jan 2, 2006 12:14:47 GMT -8
Hi SeaRat Man you sure are vinatge LOL. What are the lases for on the fins, to ketch fish. Ron Lases??? SeaRat
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mudhog
Regular Diver
Posts: 18
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Post by mudhog on Jan 2, 2006 12:41:19 GMT -8
Learn something new every day, now I need to find a pair of Lightning Jets to go with my old style Jets. BTW I just painted the vents on mine to tell then apart from any others, Krylon Fusion.
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Post by SeaRat on Jan 3, 2006 21:19:22 GMT -8
I just bought a pair of large ScubaPro Sea Wing fins off e-bay for just over $20, including shipping. I'll be using them in trials too.
SeaRat
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Post by Nemrodalt on Jan 7, 2006 18:22:18 GMT -8
Well, I got the modified fins in the water today. I may go back tomorrow. Thing is I really am not getting any measureable differences though I "feel" the splits are working better in the SkinDiver set. I tried to swim only a single lap and either this is not enough distance to reveal a speed difference or there is no difference. I swam such a short distance so as not to tire myself and introduce that as an error. Well, I guess I will need to swim a further distance to rule that out. A few tenths of a second are not statistically relevent to me and that is all I am getting--except with the NEW model UDTs purchased from our host Vintage Scuba, they are showing more speed by about 1.5 seconds. This is my first attempt, obviously I have underestimated the diffuculty of getting legitimate results. N
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