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Post by jrvance on Nov 14, 2005 15:08:33 GMT -8
funny you should bring up Bob Evans and force fins, my dad has known his wife since college and they are kinda family friends, and i live in Santa Barabara were the company is located and have been to there design/ distributing office
they are great fins, much more effectient than my paddles plus i got the friend discount eh
if you decide to buy them get the pro or more powerful models, i bought the original model and they are fine power wise, crampless, and easy to fin, however i would like a bit more power
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Post by nemrod on Nov 14, 2005 23:57:58 GMT -8
"It will be the difference in underwater swimming that bicycling is to running."
Well, a DPVis the difference between a bicycle and a motorcycle--teasing!
I did not really want to distract you with the FF. I just doubt more than 20% of the thrust from any fin is actually generated on the up/recovery stroke. I suppose the stiffer fins probably do better here and may well partly explain why Super UDT, Jet Fins and a few other stiff rubber fins are so tiring and cause cramping with some people, the leg muscles never get to "recover" on the upstroke. I think it may also explain why the limber split fins like Apollo and ScubaPro splits are generally found to be less tiring at moderate effort and so efficient overall is that they maximize downstroke thrust and provide a good recovery for the legs to rest on the upstroke. My fin concept would use two carbon fiber tapered shafts bonded into the rubber fin side rails on each side and connected under the heel--also imbedded into the rubber--- via a plastic strap. The center of the blade would not be split but would be designed to flex. The fin would have a built in curve fore to aft and also concaved on the upper surface as cast in the mold. They would have a shape not unlike the Viking A66 but I would probably put the foot pocket deeper into the meat of the blade and extend the length and width slightly to take advantage of the structural carbon fiber reinforcements. Why have the tapered shafts bonded into the rubber?--well, carbon fiber has a high reactivity---it is very springy----and fish have bones in their fins so why should scuba fins be made of stiff, heavy rubber or spineless plastic? Since I believe upwards of 80% or more of all thrust is derived on the downstroke I feel this design would optimize on that without having the weird recovery stroke of the FF or the overly stiff as a board feeling that you get with Jet Fins (classic) or UDTs or the odd spilled vortex that splits have. One thing, keep in mind, it has been said that bumble bees should not be able to fly but then when an investigation and application of reynolds flow numbers is factored in it is seen exactly why bumble bees do in fact fly very well. A scuba diver slogging along at 0.5 (or a lot less) MPH is never going to be able to operate in the hydrodynamic relm that a dolphin or tuna does at 20 MPH but perhaps there is still room for improvement. Given my understanding, such as it is, for a diver with the same square plate drag area to double his/her speed the energy applied would have to quadruple or the efficiency of the fin/propulsion device increase by a factor of four or some combination thereoff. I therefore think the biggest improvement in fins in the future will be comfort and better adaptation of what little ability the human body has in the underwater world. James
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Post by SeaRat on Nov 15, 2005 9:15:22 GMT -8
Nemrod, The latest results from pool finswimming competition is from Japan, and shows the winner, Mr. Serpuei of Russia, swam 200 meters in 1:27.05 seconds. This is 2.29753 meters per second, or 5.14 mph. So hitting 5 mph in a short distance is possible, with a diving start www.pref.akita.jp/tiiki/wg2001/result_/eng/re1030.htmlThe world record for 50 meters apnea (holding one's breath) from a diving (racing) start is 14.83 seconds. This is the fastest human in the water. That is 7.54 mph! www.pref.akita.jp/tiiki/wg2001/eng/sports/finswimming.htmlDivers must, absolutely must, get rid of a lot of "junk" in the water to become more streamlined. Your concept for fin design is great, but it is essentially the Murdock patent (take a look at that patent on the US Patent Office website). He also used rods, but I think he was using inflexible steel rather than a flexible one. But you're thinking in the right direction. Hopefully, I'll get some photos of my current fin modifications up this evening. John
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Post by nemrod on Nov 15, 2005 10:10:01 GMT -8
Returning to Voit Vikings, my copy of a 1961 SkinDiver shows a Voit display of several fins. The strap heel version of the Viking was the Model SA66. They were offered in black and have a strap heel like the UDT and were priced 13.95 dollars. They were new for that year was the claim. The standard A66 with the full foot pocket was called Viking Giant Fins.
"Divers must, absolutely must, get rid of a lot of "junk" in the water to become more streamlined"
Yes, but how, and it is certainly contrary to the current styles of diving. Even at that I doubt most divers including most of us have the fitness level needed to sustain any efforts on the level of the Fin Swimmers your talking about. As versatile and amazing as the human body is as an engine it is awfully limited.
Go look at some carbon fiber fishingrods and compare those to antique steel fishing rods---I think tapered cf shafts or rods would perform far differently from a steel rod. To bad having molds made is so terribly expensive and of course designing a foot pocket sizes that work etc. I understand that Seal teams currently use Apolo splits with the split taped with duct tape? I have read this several times but I know nothing about that sort of thing. Apollo fins are not vintage but at least they are rubber. James
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Post by SeaRat on Nov 15, 2005 13:37:43 GMT -8
Nemrod, Here's the Murdock patent drawing: John
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Post by duckbill on Nov 15, 2005 22:25:26 GMT -8
It seems that most basic fins are designed, to a lesser degree, along the same priciples. Most basic fins have more or less rigid, raised reinforcing ribs along the outer margins (and maybe some along the interior for stiffness), and thinner webbing between. The main difference is in the flexibility and amount of intermediate webbing. The more flexible and looser the material, the more the "scooping". But, it seems, most all fins "scoop" to some degree by design. Thanks again for the great information on the Vikings. I've learned quite a bit. There were more Viking variants than I realized.
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Post by SeaRat on Nov 16, 2005 9:30:24 GMT -8
Duckbill,
Actually, the scoop concept is fairly new. Most fins on the market use a flat concept of one type or another, some with ribs to "channel" the water. For instance, the old White Stag fins were completely flat, as were the Voit Viking fins (top surface). The original gum rubber Duck Feet fins did use a scoop effect, but only after they were worn for some years and the inner gum rubber got softer. US Divers had a really stiff knockoff on the Duck Feet, which were really awful, especially since the US Air Force bought them and made us use them for a time.
The original Jet Fin from ScubaPro again used this concept of a flat blade, but put a channel inside to propell water along the bottom of the blade on the down stroke. As competition came about, USD produced the Rocket Fins with an opening which relieved the pressure, but without the channel (which was the patented part of the Jet Fin).
More recently, finswimming and free diving fins (bi-fins in finswimming terminology) were developed which were quite long. They use a sine wave theory of propulsion and a flat blade. The monofins also use this theory, whereby the long blade forms a wave of material which pushes the water backwards. This works pretty well, but in my opinion, not as well as the scoop fin theory.
The scoop fin hasn't really been developed commercially yet, although the split fins are close. This theory of propulsion has water being displace by the scooping action of the blade, with a flexible interior allowing more water to be channeled than any previous design, and on both the down stroke and the up stroke.
John
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Post by duckbill on Nov 16, 2005 11:42:02 GMT -8
The original Jet Fin from ScubaPro again used this concept of a flat blade, but put a channel inside to propell water along the bottom of the blade on the down stroke. As competition came about, USD produced the Rocket Fins with an opening which relieved the pressure, but without the channel (which was the patented part of the Jet Fin). John Interestingly enough, just yesterday I passed on bidding on a pair of White Stag Jetfin copies. I was all set to put in a bid, when I noticed that the way they seemed to get around ScubaPro's patent was by reversing the channels! The channels on these guys would propel the water back on the UP stroke, totally defeating the whole concept of aiding the non-power stroke. Note: I'm using the term "up" here to indicate that it is opposite the stroke of the Jet Fins and Rocket Fins. I'm a little unclear which is "up" and "down" when you are speaking of strokes in a belly-down prone swimming position. Perhaps someone can clarify the definitions for me. Is the power stroke (kicking the leg back) the up stroke, or the down stroke?
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Post by SeaRat on Nov 16, 2005 13:51:44 GMT -8
Hi Duckbill,
I'm headed out the door (at work) taking some industrial wastewater to the lab for sampling (my day job in environmental health and safety), but saw your post and decided to reply real quick. When a person is snorkeling, horizontal on the surface getting ready to either swim or dive, up is toward the surface, and down is toward the bottom. So when I say the "down kick," I'm talking about when a diver is swimming horozontally and kicking the fin toward the bottom. The upstroke is the other half of the kick, toward (and sometimes breaking) the surface. The same goes for underwater swimming, down--toward the bottom; up--toward the surface with the diver horizontal and facing down.
John
PS--I looked for those White Stag fins, and couldn't find them on e-bay. I did find some Force Fins though (I need to replace a missing one from the 1980s).
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Post by Seahuntjerry on Nov 16, 2005 15:49:50 GMT -8
Hi, The orginal vikings had an oval hole in them on the side below your ankle and were made to fit your right and left foot. They were used on SEahunt in the first few years,I have a pair. Kemp's Cow
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Post by duckbill on Nov 16, 2005 21:20:21 GMT -8
I heard that Voit Vikings were used in Sea Hunt, but I couldn't remember them being the basic A6s. Thanks for that information. So, one more variant to add to the list!
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Post by duckbill on Nov 16, 2005 21:25:06 GMT -8
PS--I looked for those White Stag fins, and couldn't find them on e-bay. Thanks for clarifying the "upstroke"/"downstroke" definitions. Now we are on the same page. Here is the link for those White Stag fins I told you about: cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7194891946Now I have a question about Jet Fins which I will post in a new thread, so we can keep this one on the Viking track. See you there.
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Buzz
Senior Diver
Posts: 64
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Post by Buzz on Nov 17, 2005 6:59:09 GMT -8
I have been testing my Vikings against some of the other fins that I have (about 25 sets) in my local YMCA pool in the evenings. I usually paddle around the pool at a nice sustainable speed for about an hour every other night. My Vikings and a pair of Oceanic Pros are by far the most comfortable fins that I have. They are also the less tiring of all the ones I have too. However......I borrowed a pair of split fins (Tusa Zooms) and they are seriously faster than any paddle fin could ever be. I couldn't believe how fast they are.I will be buying a pair. Split fins will rule!!.....I'll keep my Vikings for vintage dives.
Buzz
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Post by SeaRat on Nov 17, 2005 11:04:41 GMT -8
Buzz,
Split fins are good, but the scoop is better ;D I found some more interesting information on the Vikings in the second edition of Dive, the complete book of skin diving yesterday evening. More later.
John
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Jack The Frogman Wilhelm
Guest
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Post by Jack The Frogman Wilhelm on Nov 17, 2005 12:35:33 GMT -8
Hi all, haven't posted on here for a while but the subject of Voit Viking fins always gets my attention. I have three pairs of these type fins. Two pairs of A6s in size Medium/Large and Large and a pair of the A66s in size Medium Large. Bought a pair from Dan and the other two pair off Ebay for rediculously high prices. I love all three pairs, fit great. Just came back from a dive trip to the island of Dominica in the Lesser Antillies and used my size large A6s for every dive I did. These fins are fantastic, and I have no idea why they're still not sold by Voit. I've often wondered if we could get Voit to manufacture a special production run of these fins for us to buy. As for when these fins were made till, I bought a pair in the summer of 1971 when I worked in Beach Haven, New Jersey (Long Beach Island) for the summer. How long after that they were available I don't know. Great discussion on the subject, take care all, Jack.
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