Weight placement
To solve the weight placement, I chose to locate the weight around the lung area. It’s a bit of a tricky location and might be disadvantageous due to the flexing of the chest when inhaling and exhaling. Only tests will find out if I find this comfortable or not and if it doesn’t effect my normal breath-up.

Balancing
One of the solutions for unbalanced tilting that caught my eye is already widely used in the shipbuilding industry and is called a keel. The principle behind this solution is to spread the center of gravity, by placing a weight below the structural keel. For ships the use of a keel brings stability and improves the directional movement of the ship. My interest lies with the stability problem it solves; when a sail ship is sailing, the wind will make it tilt, the keel will counter act this by it’s weight. That’s exactly the behavior I want my prototype to have when I’m doing a dynamic performance. So when I tilt over, due to a slightly rotated push-off while turning, the weight underneath the chest will be counteracting this and ensure my alignment in the horizontal plane. So from the balance point of view it is best to place the weight underneath the body, or at least on the lowest point of the chest.

Optimal arm placement
In the 2 preceding points I opted for the placement of the weight around the lung area and at the lowest point of the chest in the water. This will solve my discomfort and inability to fully stretch the arms over my head as well. Because the area around my neck will be clear of any objects what so ever. Ofcourse the question remains; “Will the new weight placement introduce a new discomfort or is it easier to live with?”.

Commence the Testing
As we’re already testing and have been testing with a few different setups, I’m going to continue to test for a while longer to see if he new approach really brings what it should. I will report about my findings in a 3rd article as soon as I think it’s a good point in time to share it with you all. I’ve already shared some insight from my setup through pictures, but my experience still needs to increase a little more to share. How would you like to see the solution tested in comparison to the neck weight? Please leave your ideas in the comments and I’ll see if I can include this in the tests.

PS. Current design lacks the safety feature, so I cannot compare this in the tests.

This is a post by Sanne Buurma.

This is the first article in a series about finding a better design for the weight needed in a dynamic pool freediving performance. This article focusses on my discomforts and dislikings about the current design, which I blindly followed when I first started freediving. The next article in the series will focus on the way I intend to solve these problems into a new solution and the design around it. In the 3rd article I will focus on the testing we’ve done so far with different setups, to see if they actually solve my problems. The 4th article will show how the design evolved through time by incorporating our findings in the test phases. Finally in the 5th article I hope to present a solution with an easy design, so other freedivers can try and build one of their own and see if they benefit from it as much as I do.

The prototype I had recently tested, started out with an idea to get rid of my discomfort in wearing a weight belt around my neck. There are a few reasons why I dislike the neck-weight solution;

1. Weight placement
2. Unbalanced alignment
3. Blocking optimal arm position

Weight placement
Why I think the weight placement at the neck is wrong, comes from the lung placement in a human body. The center of mass for a human being is located in the lower abdominal regoin, where as the center of buoyancy of the body immersed in water is located in the middle of the lung area. Which is a substantial distance apart when placed horizontally, besides the fact that it differs a between different body types. If you want to compensate this and bring balance to the scale, next thing you want to think about is weight placement.

When a person of average build tries to float horizontally on the back with arms along the sides of the body, the center of mass is nearly level with the center of buoyancy. Many people have more body weight in their legs and hips because of the high proportion of muscle tissue there, so their center of mass is near the hips. Thus when trying to float in a horizontal position, gravity pulls the hips and legs downward while the buoyant force of the water pushes the chest area (center of buoyancy) upward. The body rotates until the center of mass is directly below the center of buoyancy, resulting in a diagonal body position. At that point, the person should float motionless.

A human bodies’ center of buoyancy is a point around which the buoyancy forces are balanced. My problem with the neckweight is that my back-muscles are over compensating to keep a straight back. Compare it to holding a crate of beer out in front of you with straight arms or holding it close to the chest, you’ll find that holding it closer will require less effort to keep your back straight. Now imagine the same for the dynamic freediving position of the body with arms fully stretched; would you hold a weight for compensation in your hands? My point is not that the neck location is wrong, but focusses more with being able to last longer if the weight is located closer to the point around which the buoyancy forces are balanced.

Unbalanced alignment
The second reason for disliking the neck weight is the unbalance it introduces into the glide phase. It’s a fact that it is hard to ensure the lead to be equally distributed throughout the tube and requires proper craftsmanship. If it is not equally distributed, in the glide phase I find myself tilting left or right depending on which side has a little bit more weight. Even when the weight is distributed equally, I still find myself tilting, but this is caused by different strength in my arms or imprecise arm movement.

These phenomenons would pose no problem to the dive, if they were corrected by the weight. But the tilting during a glide phase is not corrected by the neck weight, because of the equally distributed lead. If I am to introduce a correcting & dampening factor for the neck weight, that would solve the problem of tilting, which is now neglected by the old designs.

Lately some improved neck weights, the one Daan calls the ‘Big Fat Bastard’ version 3, already solves a part of these problems, but introduces another discomforting factor; when you make a powerful arm stroke the weight is accelerated a tat slower than your body and lags behind your motion, than when it is accelerated it swings back giving your lower jaw a nice blow.

Blocking optimal arm position
The third problem I have with a neck weight is that in most cases the tube filled with lead will make it close to impossible to strive for optimal arm position. I myself don’t have a particular large gap between my arms when I place them in optimal position. Which is making it very hard for me to fully stretch my arms out without choking myself with the neck weight.

Although this sounds a minor detail, swimming with comfort is an important factor, the BFB 3 solves the problems with the old design by keeping the parts around the neck very thin. But a thin wire like solution, introduces a smaller surface area which has to distribute the weight on to your neck.

My 2 cents
These are just my dislikings with the current and old designs, there’s nothing wrong with them as people are swimming extremely far with them. I just hope to set sail on a journey to improve the sport of freediving by sharing my ideas. I am not the only one out here trying to improve this, so let yourself be heard and post your ideas in the comments.

I’ll share my thoughts on how I think I’m able to solve my problems & dislikes with the neck weight in the next article in this series.