What makes a good foot pocket

I get to see a lot of different foot pockets because people bring me theirs to install carbon blades into. I'm always searching for an ideal foot pocket and I've come pretty close for myself. But it's still important for me to know how other foot pockets measure up against each other, to be able to recommend them to guys with a different foot than mine. Following are some points about foot pockets that I learned to pay attention to.

1. Fit.

This is the most individual factor because it depends on the user's foot size and shape. Here is where opinions on what's best will differ but there's one thing that's common to all; you want the f/p to fit as closely, all around, to your foot (or the sock that you're using) as possible. If the f/p is loose there's a lag in the transfer of energy to the blade and the fin will be softer (provide less propulsion) overall. It looks like this, at the 2nd stage of this cycle you still haven't transferred any energy to the blade.

2. Top Softness.

This is pretty straight forward. Too hard a rubber on the top is uncomfortable, and hard to get your foot into.

3. Tendon stiffness.

How much stiffness do the tendons add to the blade to make up the final fin stiffness. This is negotiable as stiffer tendons can be combined with a softer blade to produce an overall correct stiffness for you. But in general moderate stiffness tendons are preferred ie. not to be so stiff and interfere with the flexing of the blade, but stiff enough to give it support, at the same time channelling water away from the foot and helping stabilize the fin.

4. Weight.

How heavy the foot pocket is. Generally people prefer as light a foot pocket as possible. Old style foot pockets like Picasso made of natural rubber are heavy. Modern foot pockets made of synthetic material like OMER Stingray are significantly lighter. On the flip side natural rubber foot pockets are more durable.

5. Bottom stiffness.

This is the most overlooked aspect of foot pockets. If the bottom is too soft it will allow the back edge of the blade to push up through it, causing a lag in the transfer of energy to the blade. It will be overall the same affect as with #1 a loosely fitting foot pocket.

Footpocket bottom stiffness

Most divers are completely unaware of this factor. When you've never used another foot pocket and gotten used to the one you have that has a soft bottom, you will not realize how much energy you're wasting. Only if you try a foot pocket with a good bottom and then go back to a soft bottom will you notice the back of the blades pushing up through the bottom of the foot pocket on every kick.

When the bottom of the foot pocket is stiff and the foot pocket fit is good, the back edge of the blade is held to your foot as if it was clamped to the edge of a table. The transfer of energy is instantaneous. This also immediately increases the stiffness of the overall fin allowing a lighter blade to be used. The epitome of this concept is seen with these Sporasub foot pockets. The problem is that this puts too much stress on the blade at one point where the blade and the f/p are connected. Carbon and fiberglass blades will not withstand this and that's why Sporasub only offers these with plastic blades, which we know are not nearly as reactive as fiber blades. With ultimate fit there's also the trade off with the foot pockets being more difficult to put on.

The ideal foot pocket then is one that has a stiff bottom which holds the blade well, a pocket that fits the foot closely and is soft/comfortable on the top, and has moderate stiffness tendons that gradually distribute the stress of flexing over approximately the first third of the length of the blade, offering it support without adding too much stiffness. To achieve a hard bottom manufacturers have taken a few approaches.

1. Making the whole foot pocket stiff. This obviously makes it hard and uncomfortable. I had a pair of Sproasub foot pockets I bought in 2000 that were like that.

2. Making the bottom of the foot pocket with a stiffer rubber and the top with a softer rubber. This is by far a better approach. The rubber properties must be dialed in really well. I'm not an expert on foot pocket manufacturing but I imagine the process as pouring rubber into the mold in stages. First the hard rubber to fill the bottom part of the mold (bottom and tendons) and then softer rubber on top for the pockets.

3. An interesting approach from Seatec. I haven't seen these foot pockets in person.