trim issues caused by buoyant fins

Guys,
I have a question related to getting my trim right. I currently have scubapro Nova Wings. They are brilliant fins, but have one drawback: They make my feet float, which makes it damn hard to manoeuvre (especially reversing). I'm using neoprene zip boots. I'm looking for a solution to bring buoyancy to neutral or negative. Can anyone give me a suggestion that will help keep my feet from floating up without the use of ankle weights? Are there solutions that allow me to continue to use the nova wings and my booties, or should I be looking into new fins?
I looked at the above and from further research i did online, the scubapro jet max fins, and equivalents are fairly heavy to use. The diverite EXPs seem to be quite stiff, but I have no idea if that's good or bad to be honest. Note that so far I've not been able to locate them where I am (I'm in Shanghai).
I heard the scubapro twin jets are slightly negatively buoyant (but haven't found those locally either). I can get the twin jet max, but I don't know if those are negatively buoyant or not.
Are there any other, more traditional fins, that are neutral or negatively buoyant?

PS, I got about size 45 (EU) or 11 (UK). That may limit what fins would be suitable.

Thanks!

Old time jet fins are slightly negative.

You can take them off and lay them on the bottom (in no current)!

As Okuma wrote;
- the old style classic jet fin or copies of it like turtle fins, etc (they are very stiff and hard to kick, they make my knees hurt after long dives)

i will add:
- Scubapro Twin Jet or copies of it like the Apollo BioFin
- Scubapro Twin Jet Max (less heavy but still sinking)

Basically all fins made of rubber are heavy, sometimes even too heavy

Chris

Have you tried reducing the amount of neoprene on your feet, either by reducing the thickness of the boots or even by swapping out the boots for neoprene shoes?

Did this just happen after you bought new fins or did you make other changes. Rather than your feet being too light perhaps your camera is too heavy or you can reposition weights and/or BCD. I used ankle weights for awhile for the same problem as you describe (and it hurt my lower back to try and stay horizontal) but I didn't really like them and they don't help you to travel light. After a buoyancy class at CocoView I realized how much your BCD can move up and down. Mine tended to ride up. I now have it tighter so it stays low (unfortunately no crotch strap) and perhaps because that brings the integrated weights closer to my feet I now dive without the ankle weights and have no issues.

Bart

OK, at the risk of reverting to dive instructor mode

The most probable cause of this issue is your leg position. If you bend your legs at the knee upward (to get in a good trim position) this pitches your centre of gravity towards your head and you will tend to tip you down at your head end.

If you gently extend your legs, this may well restore your centre of gravity. The trick is finding the position that allows for a good compromise between good trim/body position and forward/aft stability.

We used to do an exercise where you can go from head up to head down simply by extending or retracting your legs.

In my experience, having a small amount of buoyancy in your fins, will not cause you feet to float upwards-but having too much bend at your knee will.

Hope that helps.

Adam

I'm sure my camera weight/buoyancy affects my trim, but the point is to have a good trim with camera. My camera is a bit negatively buoyant (I have an EPL5 with nauticam housing, 2 Z240's, with either a 6" dome port or a macro port. I used INON 24cm floats with 24cm sticks, I now changed that to h2o floats, both 28, one 3 cm diameter, another 4,5 cm diameter. I tried 24 + 28cm INON floats but that was too buoyant. The new setup should be somewhere in between).

However, i don't think I should consider the camera buoyancy to be the problem. Because, when I stand on one knee on the bottom, that's a position thats difficult because my feet constantly want to float (i.e I need to push them down).

During photography It makes my positioning very uncomfortable as it tends to result in me arching my back more than is comfortable for a long period of time, which ends up sore at the end of the day.

I think with neutral or slightly negatively buoyant fins I might be in a more comfortable position.

I don't think your camera will affect your position or buoyancy at all! Ideally, you should be able to trim off without the camera and have no issues. Adding a camera may meant you need to add a tiny bit more air into your BCD, but most people would offset it by using breath control.

You mention "standing on one knee", do you mean kneeling? Generally, I would discourage you from contact with the bottom at all, as there is always the risk of environmental damage.

There is no "correct" position or trim, but most people start off from a fairly horizontal position, with their knees bent up so as to lessen the chances of disturbing sand/silt or marine life.

In this position, you may find slightly positive fins are an advantage!

Adam

Great post Adam!
I have seen a few people (mostly woman) with floating feet and the use of heavy rubber fins or ankle weights fixt that problem.

But i agree 100% with you that photographers should have light feet to avoid kicking the bottom and its life and stirring up the sediments.

That is one of the the reasons why i prefer to use my drsuit to take pictures as i can ajust my horizontal buoyancy on-the-fly to adapt the situation.

ksporry:
to verify your floating feet problem you can try to hover full streched and vertically, if you your feet still go up you can try to move the tank or remove trim weights.

Kneeing on the bottom is generally a bad habit and will damage marine life and probably you too and you will stirr up sediments.
There are some places in the world where kneeing is "allowed" and that is on sandy patches where you may watch shark feeding in the carribbean for example.
Sandy bottom sems to be dead, but this is completely wrong and damage to marine life (or you kneeing on a Weever orsimilar) can still happen!

In any case, you will look much more cool and professional if you are able to hover above the bottom than kneeing like a student during his dive course.

Any good and experienced instructor of any dive agency can help you to archieve that and this course is calld Peak Performance Buoyancy or can be integrated in

the Digial Underwater Photographer.

A 45° or 90° viewfinder will help you to hover above the bottom and taking pictures of things on the bottom in front of you.

Chris

I like my fins to be neutrally buoyant. There are many reasons for this. If you loose a fin it will stay mid-water is one (It happened to me during a fast descent and had to go back and pick it up)

In both my wet and dry set up I have never issues of light feet. Those could be due to a number of factor including your body mass and muscles however in order to minimize issues you have the option of ankle weights (very popular for dry-suit divers)

Just to give you an idea of my set up I use full foot spearfishing fins (longer than normal but not as long as freediving or apnea) with 2.5 mm neoprene socks when I dive wet.

On dry set up I have a fusion dry suit with scubapro rock boots that are negative as well. Never had any issues of light feet even diving dry.

When I need to do a shore dive I use scubapro tropic and try to avoid tall boots, I had a set of traditional typhoon 6.5mm and they did make my foot lighter though not to the extend you mention.

I use mares avanti quattro power full foot or quattro open heel since years and I never wished I had a different fin

My feet float significantly in steel twin tanks and a little bit with a single tank. I tried many, many different things. The "stretching legs out" thing is a furphy in my opinion - if your feet float, straightening your legs puts your feet further away and increases the lever effect. I ended up head first in the substrate within 30 seconds, each and every time (sorry Adam). I tried ankle weights without success, and switched to the original Jetfins. I also changed the socks/boots that I wore with my drysuit.

The thing that did help was making my head float more. I achieved this by adding 2 x 3lb weights to my weightbelt, and therefore having 6lbs of air in my wing. I also modified my wing to reduce the space for air near the bottom and push. A friend of mine changed from a shell drysuit to a neoprene drysuit to achieve the same thing and trimmed out much more easily afterwards. What thickness wetsuit are you wearing?

I have size 42 feet and wear XL Jetfins. I like them because they're short and stuff, so easy to maneuver and good for power. I know a number of cave divers who really like the grey DiveRite fins for similar reasons, and because they are not as heavy as the Jets.

Hi Liz,

Interesting. I assume that your comments relate to wearing a drysuit, rather than a wetsuit?

I guess one important point in this expanded discussion is the role of the head position too. It is effectively a 10lb weight. Moving it up and looking forward (craning your neck back) will help to bring you into a head up position, looking down will help to tip you forwards.

Head up/head down is definitely directly related to leg position. If you extended your legs and still ended up face down (wearing a drysuit?) then you have some dynamic instability caused by excessive air movement in your buoyancy system. Back mounted wings (as you correctly identify) do allow air migration and if there is too much air, this can cause a head down posture. A drysuit makes things worse.

I have yet to see anyone with actual floaty feet. I don't believe that anyone gets into a swimming pool and finds that their feet float (with or without positively buoyant fins) upwards while their torso and head sink! This means that the issue related to by the OP must be due to excessive air in the feet (with a drysuit) or body position (without a drysuit) causing their feet to float up.

Carrying weight requires the addition of more air to achieve neutral buoyancy. This further adds to potential buoyancy shifts as the air moves around the buoyancy system. It is interesting that you record that with steel doubles, the situation is exacerbated-this is perhaps due to the fact that they are very negatively buoyant and hence you are adding significantly more air to offset this? The reason that ankle weights failed to prevent the issue may well have been due to the fact that you added more weight, requiring more air and hence more instability...

It is impossible to diagnose this 100% without actually being in the water with someone. What I can categorically state is that if you are correctly weighted, moving your feat away from the centre of gravity and looking up will bring your feet down and head up and viva versa. All the divers I have done the beloved Peak Performance Buoyancy course with over the past 14 years will attest to the act that it works!

Adam

Yes, all drysuit. Although I have the same issue when diving in the tropics in bathers (swimsuit, swimmers, etc). I'm a cave diver so being able to hover motionless was essential to my health and happiness underwater. I spent a lot of time getting things right with cave diving instructors, GUE folk and others. Here's the list of things I tried and the outcome:

Less air in the drysuit (to the point of squeeze bruises). Impact: minimal, extra chilly on deco

Kneepads/gaiters on the drysuit. Impact: good and I could put some air in

Thicker socks and tighter booties. Impact: good

Moving doubles down as far as I could. Impact: minimal (they were already there)

Jetfins. Impact: some, not huge.

Ankle weights. Impact: minimal and very irritating

Head pressed between tank valves, arching back and clenching butt cheeks. Impact: some, plus a sore back

Additional weight and duct tape around the bottom of my very large doubles wing (both sides). Impact: fantastic

Moving to sidemounts. Impact: haven't had a problem since My rEvo also seems fine as a backmounted unit.

Tanks are heavy and valves are the heaviest bit, increasingly so as you breath the gas out of them. When you put valves behind your head, your head sinks. I agree that if you lift your head and upper body your whole position in the water will change. I'm very unconvinced that stretching out floaty feet helps this. With properly adjusted twins, Jetfins, squeezed drysuit, a full breath, kneepads and a fully arched back I could (just) hold a hover with bent knees and feet up. I could then gently extend my legs and pitch my head straight down into the ground, changing nothing else.

Generally I'd agree that less weight is better and managing extra air is a PITA. It's worth noting that I went from zero weights to 2 x 3lb weights to fix the problem. I originally put the weight on to practice a doubles removal and swim underwater at depth so I wouldn't float away from my tanks. When I discovered the difference in hover-ability, I didn't take them off again.

Apologies for high-jacking your thread ksporry....all I wanted to contribute was that if adding more weight to one end doesn't work, try adding more buoyancy to the other! Good luck with it.

 

You mention "standing on one knee", do you mean kneeling? Generally, I would discourage you from contact with the bottom at all, as there is always the risk of environmental damage.

 

 

 

There are some places in the world where kneeing is "allowed" and that is on sandy patches where you may watch shark feeding in the carribbean for example.

Sandy bottom sems to be dead, but this is completely wrong and damage to marine life (or you kneeing on a Weever orsimilar) can still happen!

 

Actually, I don't just kneel or stand anywhere. This is always during instruction sessions and always on sand or dead rock/rubble. Never anywhere where it could potentially do harm to aquatic life. I'm very conscious about aquatic life when I'm diving, which is why I flag this up as an issue that I'm hoping to address with new lightweight but slightly negatively buoyant fins. (if I can't fin backward, that introduces more risk).

I also did get my PPB, but I got that before I got my own gear. The 2 PPB dives do not teach a diver sufficient trimming or buoyancy effects of gear and its use.

 

Carrying weight requires the addition of more air to achieve neutral buoyancy. This further adds to potential buoyancy shifts as the air moves around the buoyancy system. It is interesting that you record that with steel doubles, the situation is exacerbated-this is perhaps due to the fact that they are very negatively buoyant and hence you are adding significantly more air to offset this? The reason that ankle weights failed to prevent the issue may well have been due to the fact that you added more weight, requiring more air and hence more instability...

 

This is an interesting point that I may try out. I don't use a dry or wet suit. I only dive with a rash guard and shorts as it's usually 28 degC in the water.

However, I did get the feeling that I could do with less weight (e.g. at the end of the dive I still have some air in my BCD to keep me neutral, and that's with a 15l tank). Currently I'm on 4kg. I'll try to reduce that to 3 and see if my trim gets better as a result.

As a note, a camera can definitely affect buoyancy and trim. If the camera is 1kg negatively buoyant then thats extra weight. I actually used that to trim my position with my previous BCD. If i wanted to be more head down I pushed out my camera, and if I wanted to be more feet down I pulled it in. With my current camera rig, BCD and fins I'm nicely horizontal, except my feet want to go up.

So I'll try out that theory about less weight and less air before changing more gear...