Ideal Trim

Ideal Trim

By Jason Caldwell

There is often a lot of discussion between divers on what constitutes good and bad

trim. Why is trim even important I hear people ask? This article will try to explain a

few of the reasons why ideal horizontal trim is important and show a few techniques

to allow you to achieve and maintain it.

What is ideal trim?

Being in ideal trim is diving in a horizontal position with your body parallel to the

floor of the cave whilst presenting the minimum amount of physical resistance to the

water ahead of you as you move through it.

Why is this important?

The benefits of ideal trim include:

• Less gas usage throughout the dive

• An ability to be able to move quicker through the water with less effort

• Increased manoeuvrability ‐ Being able to turn around quicker to assist a

diver behind or ahead of you

• Less silt disturbance, as fin wash is not pushed towards the floor of the cave

but behind the diver

• Better general visibility of your surroundings in all directions

How do you achieve ideal trim?

Achieving ideal trim is a combination of physical techniques and equipment set‐up.

When the entire combination of these are used, ideal trim is not only easy to

achieve, it is very easy to maintain throughout your diving. Anyone can have nice

trim for a moment, but it takes practice and effort to maintain it.

Equipment

Initially, it is important to set your equipment up to allow you to have your weight as

evenly distributed as possible. This is best achieved conducting a balance test.

Balance tests are done by starting in a horizontal position in a fresh water site like a

sinkhole and remaining perfectly still. You may tip forward, backward or stay

perfectly level. Have a buddy help you, so you know that you are indeed level.

Make sure that if you normally have a light, a reel or something else on your

equipment, that you do this test with all of that in its normal position, as every part

of your equipment configuration impacts on your trim position.

Placement of tanks, tank bands and weighting systems play a huge part in how easily

horizontal trim is achieved.

Many divers are head heavy, and this results in them having to compensate by

dropping out of ideal trim or they will tend to nose dive. This can be due to tank

bands being too low or choosing higher mounting holes in their back‐plate or softpack.

It is often done to allow one to reach their tank valves easier. The top tank

band should be mounted as high as possible, which is just before the tank shoulder

curve. It allows the tanks to sit closer to the diver’s centre of gravity. The top

section of a scuba tank, where the valve screws in, is considerably thicker than the

walls. This along with manifolds/valves and regulators makes the upper portion of a

twinset heavier than at the base. V‐weights can also contribute to this, as they put

the weight in the upper portion of the tanks. Tail weights offer a great alternative

and are mounted from the bottom band bolt hole to within 20mm of the base of the

twinset. Even if you don't require weight in fresh water, you may find that 1 or 2

kilos on a tail weight make all the difference when it comes to achieving ideal trim

position. Divers often use heavy 'old style' rubber fins to further change this centre

of balance point. Ankle weights should be avoided at all costs as they are a band aid

solution to the larger issue and reduce the finning efficiency whilst increasing muscle

fatigue.

Divers who are feet heavy are often wearing a weight belt and may find that a tail

weight can benefit them too. Sometimes a smaller tail weight with a medium V

block weight will assist in finding their ideal level balance point. Other methods

involve changing soft packs and aluminium back plates for stainless steel models.

Once you are satisfied your tanks are in the right position, try adjusting weighting

configurations till you feel more comfortable in the level position. Check and

recheck until you are able to remain motionless and yet stay in relatively ideal trim

position.

Physical Techniques

While equipment configuration plays an important part, there are a number of ways

you can adjust your body position to make subtle changes to your trim. You may

need to do this in addition to adjusting your equipment.

Some techniques for achieving ideal horizontal trim are to:

• Keep your head up with your eyes looking in a forward position

• Contracting the lower lumbar region (arching your back) and gluteusmaximus

muscles (buttocks) to ensure your knees are level with your torso

• Keep your fins flat and parallel with your torso to ensure they assist with

control and stability

This does take work to maintain and can often result in one having a slight aching in

the lower lumbar region after the dive. In time and with practice, these muscles

grow stronger and this mild discomfort will become less or nonexistent.

If you are head heavy, you can extend you feet out and move your arm position back

to change your centre of balance point. Equally, if you are feet heavy, you can tuck

your legs up a little and extend your arms forward.

What else impacts on trim?

• Using your drysuit as you main point of lift has an impact on trim. A drysuit

will tend to collect gas in the shoulder region and make your feet drop down.

A wing is designed to sit under your tanks and lift them evenly without

automatically dumping gas like a drysuit can. Use your wing as your primary

lift device, whilst simply putting enough gas in your drysuit to allow you to be

warm whilst having a full range of movement.

• Tight undergarments and tight drysuits can make a diver need to compensate

by having to add too much gas during the dive to be able to move freely.

Check these are fitting correctly on dry land whilst not wearing tanks or a

harness, by squatting down on the ground and reaching behind your back.

Any tight areas around the knees or arms will be further compounded on the

dive.

• Task loading the diver will virtually always compromise their trim position

with the knees dropping and fin wash hitting the cave floor. This can add to

an already small problem in a cave situation as the silt cloud begins to

surround the dive team. Staying higher in the water column can help

minimise this situation.

Are there times when you need to drop out of trim?

Yes, there are times and places where dropping out of trim makes perfect sense.

• When you are motionless on deco, dropping out of trim may be a little more

comfortable

• When you are moving in a narrow inclined tunnel, you need to move out of

trim to negotiate the passage

Where possible, stay in ideal trim and you will find it becomes easier in time.

Conclusion

If you can work to maintain ideal trim, you will find that you become more efficient

in your gas usage, be able to react to your buddies much easier, have a lot better

overall visibility, you will create less silt and will be able to cover more distance with

considerably less effort. Remember, it will take practice and effort, but the rewards

extend well beyond those contained within this article and will stay with you forever.