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10-10-2020 - Shaun dives deep into the different types of fins that SOMMERSO offer and and unique structures between each type while offering insights of which may be right for you - (article below).
S O M M E R S O : The art of diving deeper.
It’s all in the Fin
Free-diving fins and foot pockets really do differ from person to person. Well-fitted foot pockets result in the best transfer of power (energy) to the blade, not to mention comfort for the wearer. In saying that, it is just as important to have the right blade to suit YOU. A fin or blade really needs to suit the user’s finning style or technique, and the purpose for which they are being used.
A lot of people bicycle kick due to it being natural and never having had someone teach them or critique their style. Bicycle kicking is a style of kicking that we all tend to use in the beginning, and as a result our fins don’t get enough purchase in the water due to either the material they are made from or the angle they are set at. So we bend the knee more to get the fin under the surface and gain traction with the water running over both surfaces of the fin. It’s very much like cavitation on a boat’s outboard; too much air under the fin/propeller, the less propulsion you get. You go nowhere.
“Purchase” is the amount of blade that is in the water when we kick on the surface. To get the right amount of purchase the fin needs to have the right angle from where the foot pocket ends and where the blade starts. This is important when you’re kicking on the surface a lot (mostly spear-fishers) however if you’re mainly line-diving then this is not as relevant. A spearfishing fin setup would generally have a blade angle between 28-32 degrees whereas a free-diving fin for line-diving, competition or pool training would be around the 20-24 degree angle. These numbers are just guidelines and can vary between divers and requirements. A blade’s angle should not exceed 32-36 degrees as this would play against our streamline position that we create when diving down.
The other style of kicking is straight leg finning. This is where you have your legs a lot straighter and the power comes from your hips in a rolling motion and your ankles. Some power still does come from the knee, as it will always bend. Arms positioned above your head with biceps tucked in close to your ears and hands clasped, will create the ultimate position when diving down. Repetition and stretching will increase your flexibility in this hold over time. But the key point here is that with the right blade or fin for your body weight, the straight leg finning technique will save you a lot of wasted oxygen and energy in your dives. Obviously doing this can increase your bottom time and increase your catch rate (when spearing).
Free-diving fins displace more water due to the large surface area compared to scuba fins. So having the right blade in the most comfortable foot pocket will have the desired effect in propelling you in the water.
Soft fins are great when they are matched to your style and body weight. They can reduce your lactic acid build up and conserve your oxygen levels throughout your dive because you are more relaxed and calm. If you’re overweighted or too heavy for soft fins they will give you less power, peak out quicker and require extra movement of your legs to get you anywhere.
Stiffer fins have their place especially if you are spearfishing or swimming against a roaring current. They will require more energy to be used; hence more oxygen being consumed and more lactic acid build up in your muscles. Therefore stiffness should match your muscular make up.
I know it’s hard to find the right fin for what I’ve just explained. That’s why I have endeavoured to create a method and system to match blade stiffness to body weight and style.
Free-diving fins come in a range of materials from plastic to carbon fibre.
Plastic or thermo plastic fins are low cost and are great for entry-level free-divers. They have limited flexural memory and are generally quite stiff. Whilst durable, you can expect to get sore ankles and muscles from plastic fins.
Fibreglass fins are generally the next step up from plastics. They are made from fibreglass matting and resin, and are more forgiving and responsive than plastics. When stepping up to fibreglass you should feel the difference in flow and propulsion with every kick. They have a slight lag when they return back to neutral and carry a bit of weight compared to other materials.
Composite fins are made from mixing fibreglass and carbon fibre together. Basically fibreglass is sandwiched between layers of carbon fibre and gives a fin some of the snappy return of carbon and soft response of fibreglass. These fins will be marginally lighter than fibreglass and also more expensive.
Carbon fibre fins are the lightest and most responsive of all fin materials. With a tensile strength higher than steel, they will flex way further and return back to neutral every time. Whilst they are more expensive due to the high quality of the construction fibres, expect to notice the power release and greater conservation of energy when using carbon fibre fins.
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I hope that this article has helped anyone that has wondered what the difference is between fin stiffness and angles, and whether carbon fibre fins are worth the greater expense.
And I know that there are a lot of guys out there that want a pair of fins that they know will get them off the bottom when hauling up a fish; this is why I have spent the last many years thinking, testing, over-thinking, more testing and with much success - created carbon fins to address these issues. Although I can’t address poor technique, I can ease the fatigue from stiff fins that result in build up of lactic acid.
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