Happy to hear you know all the basic kicks. The Extra Force applies almost the same "Push Thrust" on a frog kick as you "push" forward with it....the Jet Fin X Large size has enough of a larger blade, that a very powerful diver might prefer the slight increase in thrust per each "push" on the jets, versus the Extra Force....this is slight, but I am trying to be dead accurate with this....Modified Flutter is MUCH more effective with the Extra Force than with the Jets or Hollis....Reverse kick is MUCH more effective with the Extra Force--I can actually swim backward with these faster than many recreational divers swim forward at their normal pace--I have shot video of people following me, with me doing the reverse kick with the Extra Forces on.......As far as flutter, I agree it has little place in most cave diving....although there is a much smaller downward vector with the Extra Force, and they don't silt nearly as much as a jet or F1 would with the traditional flutter--and if you were using the Extra Force for a Flutter kick, it is much more efficient than the jets, and can be used to sustain much higher speeds for a very long time.... As to why you don't see them...they have not been marketed, and Dive Shops try to sell the manufacturer gear they specialize in...and have quotas on.....the Force Fins are also pricey, and hard for Dive Shops to get their heads around--they don't normally begin with what's best...they tend to begin with what they can make good profit with--then what is profitable AND GOOD.... There would be very low profit with the Force Fins, at any price point that would sell in their shops.....And...the Florida Cave community likes Jets...it would take some major DEMOs for any of this to change....
Hey Dan - happy that you know the basic cave kicks also. I have not tried the Extra Force fins so have to admit you may be right. I have tried the regular Force fins of about 10-15 years ago and did not think that they were anything special. Looking up the Extra Force fins I found them listed at $786.25. You did say they are pricey, but almost $800? I am quite happy with my sub-$100 OMS Slipstream fins and actually have been told that I need to slow down in them. Cave divers do spend a lot of money on equipment ( up to 10k+ for rebreathers, scooters for 2-6K+, over 1K for computers, etc.) and one would think that if the value to price ratio for the Extra Force fins made sense they would be all over it. As it stands, I don't know any cave divers that use them nor any shops in cave country that carry them.
Jacket BC's have soft backpacs, and poor control of the tank...it is a poor comparison..... a Halcyon backplate and wing on a single tank, actually sits on a STA, and is farther away from the tank than when the backplate is on doubles...
You did say that BM doubles are closer to one's back and did not specify a Halcyon backplate (BP) and STA. For single AL80s, a jacket BC is quite adequate and if using a BP with a wing that has grooves/channel the AL80 is fine also. For steel tanks (heavier) you do want a single tank adapter (STA) and when I used one the Oxycheck one was quite minimal and didn't extend the tank out very much, if at all.
...the vast majority of tech and cave divers here on SB are going to agree with me that when you get 6 inches off the bottom,double 80's with a 40 pound wing will be far more stable ( less likely to roll the diver left or right) than with a single tank....I am kind of shocked you have not experienced this yourself.
I don't know who this "vast majority of tech and cave divers" are, but the only way that doubles will be stable is if they start becoming positively buoyant which is fairly quickly with AL80s, single or double. Steel tanks, especially when full and heavy, as well as any heavy, negatively buoyant object on one's back will exert a turning moment (tendency to "turtle") on the diver. With doubles it is twice as much (assuming all else is the same). As for you being "shocked" that I have not experienced the stability of BM AL80 doubles, I never dove that configuration as all my BM doubles experience was with steel LP85s, LP95s, and LP108s. This hovering stability at 6" off the pool bottom I have achieved with singles (AL and steel) as well as BM and SM steels. All I can say is that is was a lot more difficult in BM doubles. I will admit, as I think about it, BM AL80s would probably be a lot more stable than BM steels, especially one they get breathed down and become more buoyant.
As to the SM direction, I see this if tight overhead restrictions are common issues for you....but where boat diving is also an issue, the BM doubles are much quicker to get in and out of the water with, and much easier for buddy teams to be able to help each other effectively with for gear familiarity issues. My friends from the WKPP were playing with SM back in 1993, but found limited situations where they had any use for it...though there were some passages with the kind of restrictions that DID have them using SM.....Point is, this is nothing new, and what was wrong with SM in 93, is still wrong with it today.
To me, and to quite a few divers, cave or otherwise, SM is not just about tight overhead restrictions, although there are places that SM can access that BM can not (Jug Hole cave, for instance). SM is more about not having 100+ pounds on your back getting in and out of the water, it is about the freedom of movement with much better trim and stability without having that same rigid 100+ pound anchor on your back, it is about the safety and redundancy of two separate gas supplies and the ability to see/trouble shoot any leaks in front of you instead of guessing (I know, Dan, that you don't guess and can troubleshoot/resolve any regulator or valve issue behind your back in seconds - 2 maybe?) what is happening behind your back, and it is not having to necessarily rely on your "similarly well-trained" buddy to save your bacon. No, SM is a totally different mindset of diving which in my opinion is better.
In ocean, I suppose for anchor diving where you have all the time in the world to get in and out of the boat, the SM is fine. In more challenging Drift Diving conditions, the extra time required for the SM divers, is often going to cause them to miss the wreck on the bottom....you need to be able to jump off the platform and be 30 feet down in the next few seconds....
Easy with Back Mount.
Quite a few years ago when I had a cruising sailboat, I did a lot of diving from it - Florida, Bahamas, etc. A sailboat freeboard can be quite tall (3, 4 feet or more). A lot of times I would just jump in all geared up or throw the kit overboard tied to a line and put it on in the water. Getting out was the same, I would remove the kit in the water and tie it off. After climbing aboard, I would haul it up. SM off a boat is the same, you can attach the the tanks in the water or jump in all geared up. You also have the option to climb up with all your gear (same as BM), take something off - like a tank, tie it off, and climb aboard with the other tank attached, or you can remove all your cylinders before climbing up. SM gives you many options and it does save your body. I HAVE seen divers unable to climb into a boat on their own wearing BM doubles, especially in rough seas.
BTW, once you get proficient in SM, you can also be all geared up standing on a platform ready to submerge quickly for a drift dive. I did 2 summers of tech (mostly drift) diving with FAU Ocean Engineering in Boca Raton as an undergraduate, but that was before SM.
My friends from the WKPP were playing with SM back in 1993, but found limited situations where they had any use for it...though there were some passages with the kind of restrictions that DID have them using SM.....Point is, this is nothing new, and what was wrong with SM in 93, is still wrong with it today.
I guess the point is ... your friends from the WKPP (assuming that it includes "King" George) were wrong about SM in 1993 and are probably still wrong about it today, unless, of course, they have changed their minds - doesn't sound like you have. Anyway, looks like Halcyon has just come out with a really nice SM rig, the Contour. If only GUE would now adopt a SM track (in addition to BM) it would certainly go a long way to put a lot more people in their camp.
---------- Post added February 14th, 2014 at 06:44 PM ----------
While we are on the topic, this is me with the LP 108 during my safety stop on the one dive I did with it. I tried to hover as best I could but still found myself kicking my fins a bit to keep nice and level...
Hey Chris, that is perfectly normal, at least at first. To be perfectly motionless and horizontal requires at least two things - body control and a trimmed out weight distribution.
For body control, you need to deal with back arch/hip position, legs not dropping, the proper amount of knee bend, position of your feet and arms. All will affect your fore-aft trim. It can sometimes be counter intuitive as to what is happening. For instance, if your feet are dropping, it could be that you are foot heavy or it could be that you are foot light (head heavy) and are dropping your feet to compensate.
Trimmed out weight distribution: the best way to deal with this is to find a pool you can use, put on all your gear, empty your wing and sink flat to the bottom in the shallow end (3 to 4 foot). Assume your ideal horizontal diving position (from photos or books) and slowly add air to you wing in short bursts - give the wing and yourself time to react. Eventually you will begin to rise. If your upper body rises first (while trying to stay straight/horizontal), you are foot heavy, if your legs rise first, you are head heavy. For this to work, the wing lift needs to be as close to your center of buoyancy as possible - otherwise your trim will be different if your wing is full (beginning of dive) and when it is empty (end of dive - safety stop). You may need to adjust your wing and or tanks to achieve this - also type of exposure suit (wet or dry) and light or heavy fins affect this also. Once this is adjusted, final adjustments can be made with trim weights (a couple of pounds), typically with movable weight pockets on your harness.
Once you get your weight properly distributed, proper body position is a lot easier to maintain. Ideally you should be able to hover motionless, remain horizontal, and rise/fall with just your breathing.
BTW, all this is a lot easier with side mount as your tanks are a lot closer to your body's center of buoyancy. Also, take video of your pool sessions. The feedback can be very different than what you think you are doing!
Good luck and have FUN!