Unless you can find a Heiser tank, I've only run across one and it made my PST 95 feel light.
New tank throwing off my trim
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Unless you can find a Heiser tank, I've only run across one and it made my PST 95 feel light.
I do wear light fins. That's just what I bought when I was shopping for fins before open water class. They seem to work fine for me. Here's a photo of one of my dives (USS Mohawk, Gulf of Mexico). No problem staying horizontal with this configuration.
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...
If you have access to a pool, try moving the tank down as far as you can get it. See where that leaves you. One of the instructors at the LDS where I bought my 108's showed me how to fix my trim. Before I fixed it: Get in the pool, get horizontal, and stop moving entirely.. the result is my head would dip down and eventually I'd flip over completely. Now, it just feels "right." No kicking to maintain trim position.
vicp
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I dive full cave in Florida's cave country and have yet to see anyone use Force fins. Usually Jets, Dive Rites, OMS Slipstreams, Hollis, etc. Paddles, not splits. Kicks used in cave diving are frog, modified frog, modified flutter and back kick. Power flutter kicks typically have no use in cave diving as they will stir up silt leading to zero visibility. I have not used the Extra Force Fins (so do not know how well they do these kicks), but as I said, I have not seen them at the Florida cave sites.
True, mostly steels (typically "cave-filled" LPs).
Not too many 80s in Florida caves, seems that is what is used in Mexico (never been there, but want to go).
Not really. You have a backplate and a wing in between. A single tank with a jacket BC is closer to your back.
Nonsense. Back-mounted (BM) doubles are way less stable then a back-mounted single. If the wing is too large (coming up the sides of the tank or "taco-ing", it will trap air and be less stable. Using wings that are too large just exacerbate BM doubles stability. I dove BM singles for years, including LP108s with no trim or stability issues other than adjusting for a slightly different weight distribution. When I started diving BM doubles, I had to spend hours in a pool (with video) practicing and adjusting weight, band height, wing position, changing tanks and wings to get stable(to keep from "turtling") and in trim.
You can hang/hover motionless in ANY successful configuration (BM doubles, singles, or even better yet - sidemount). The notion that BM doubles act as "gyro stabilizers" is total BS. If anything, it requires more practice, attention to equipment & configuration, and body control to remain stable in BM doubles.
If the OP is considering overhead training/diving, side mounted (SM) doubles should be given serious consideration. I would suggest avoiding BM doubles altogether as there is no advantage to them (only disadvantages in my opinion) plus many of the stability/trim issues with BM doubles do not exist in SM. SM is also a lot more fun!
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- 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....
- 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..... And....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.
- 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.
- 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.
vicp
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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.
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.
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.
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....
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.
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 ----------
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!
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The original Force Fins were NOT fins I liked...in fact in the late 90's, I had a Force Fin Challenge I created that anyone wearing Force Fins that could stay with Jim Abernthy and me on a spearfishing cruise pace( not a race--just the way we swim), could have a free week of diving and hotel stays....There were none that could do this, because this fin was created to be a small gear--like a bike in a gear to allow pedalling up a steep hill...so it would not go nearly as fast as freedive fins, no matter who was using them....The thing is, Bob Evans than made many other models, with DIFFERENT GEARING, most notable to me being the Excellerating Force Fins, and the Extra Force Fin( my favorites of Bob's fins)....When you kick slow, they take no effort --when you amp up the frequency and power of the kick, they become exponentially more thrust producing--the opposite of splits, and far more thrust productive than jets.
When out of sight, and out of mind......Cave divers have not seen these fins, and most will buy what their instructors pushed at them...or their buddies.....For a change of this magnitude, some serious DEMO sessions would be needed....and I am planning on getting some GUE's to try these Extra Force Fins, and to comment on them.... Have some patience
I am just discussing double 80's....as these are the tanks for tech in ocean--I am against big steels in ocean due to buoyancy issues and the very different issues encountered on tech dives in open ocean with currents. It has been demonstrated so many times that the double 80 with a 40 pound wing is more stable than an 80 ( or a lp 120) that it is silly to argue about it here--I don't see anyone believing you on this.
This being a practice absolutely impossible to use where drift diving is the norm, and where precision drops put you on amazing dive sites.....your plan would be impossible to set you up for the right descent trajectory to hit wrecks or good reef areas.
In places with no currents at all, your plan will work fine. In my favorite dives off Palm Beach, your plan won't work ( Boca is more like Lauderdale with much less current) ....Similar in great places I have dived off of Tobago, and in Fiji, where the currents concentrate amazing hordes of marine life not possible to find in the still water ocean playgrounds for SM divers---places like Lauderdale or Key Largo.
For very rough seas, and particularly for serious exposures where avoiding DCS has to be on the minds of the tech diver, you really don't want to do any exertion.....Good tech boats will have the tech divers get out of their BM doubles in water, and the safety divers will deal with getting the gear on the boat.....George Irvine, Bill Mee and I commonly used this for many hundreds of tech dives off of Palm Beach , and Lauderdale on each of the charter boats we frequented. Doppler studies would show actual showers of bubbles coming off when the major muscle contractions of climbing on to a boat with heavy gear was engaged in( we had the studies done on us around 1996 when we were optimizing our best practices for DIR in deep ocean)..If the boat could not field a safety diver on a given day, one of the tech divers would take their turn as the safety diver for that day...and at the duration into the dive where the team was expected to be at 40 or 30 feet on deco, the safety diver would splash...check the team, and then begin the shuttling process of stages and anything else that needed to get on the boat.... The charter boat you choose, is very important for tech....
We see SM divers trying this all the time...they are normally picked up by the charter boat, and re-dropped multiple times...they often just can't do challenging dive sites in high drift.
Chris-I'm lucky --ive dived al80's and steel 10.12 and 15l tanks.
In my experience diving with a 15 feels heavy and cumbersome in the water.Ponderous would be the best way to describe the initial feel after diveing other tanks.
logically youy are trying to turn a bigger surface area.
You do get used to it with time.
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