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blade stiffness

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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New Member
Mar 8, 2023
Hi everybody!
this has been asked before but considering my case I do it again:

I have my hands on a pair of CETMA Mantra fins ( full carbon) . Everything is just what I want, except for the blade stiffness. They are medium

For now I use Cetma Prana with a soft blade.

I go for experience underwater going to 40 m regularly( but no competition, no spear fishing) My PB is 59 m with Bi-Fins

I am 181 and weigh 75 kg
But: I have a long history of triathlon and cycling with 12.000 km per year in my active years. Means I have relatively strong legs with a lot of endurance.

What do you say about the medium stiff blade for me?
Thanks all!
Welcome to the forum! I don't have any advice to give you other than to say that today's fin manufacturers ought to be providing better descriptors of blade hardness than "soft", "medium" and "hard", which are better than nothing, I suppose, but still likely to vary widely as metrics from one company to another.

As early as the mid-twentieth century, fin reviewers were supplying measurements on the Durometer Shore scale of blade hardness:


It cannot surely be beyond the wit of Man to come up with an industry-wide scale of fin stiffness. This topic has been discussed here before at Freedive blades hardness numbers.
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What is the purpose of your activity: going as deep as possible and swimming mostly vertically? In this case get mediums. Otherwise get them soft. My personal best was achieved in Mares Avanti Tre $35 dollar fins. It was only 32 meters but after trying several carbon fins and owning 3 pairs of fiberglass, carbon and sandwich I realized that fins are not a limiting factor in the depth I was able to achieve. Ultimately it is the amount of burnt oxygen per unit of energy required to kick. Stiffer fins make you reduce the kick amplitude - otherwise you'd overload your legs. So it is a tough call - probably a footpocket comfort is equally if not more important than stiffness.
By the way my weight is 120-125 kilos, mostly muscles. People of my size are poor divers - too much oxygen needed. I just came back from a trip where I took my old Avanti Tre after using carbon for many years. Once again, they did not limit me. I had to work more frequently but they are very easy on the legs so I am now thinking about using them again for spearing.
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