Time to upgrade: carbon bifin or monofin?

[efattah]

It doesn't matter if carbon has better material properties than fiberglass. If the stiffness profile is wrong, and the shape is wrong, then those factors overwhelm any intrinsic material advantage. For example, titanium may be lighter than steel, but if the machine is made incorrectly, then the titanium loses its advantage. A well made 'steel' machine will work better than an incorrectly made titanium machine.

As far as footpockets, I have used many types of open heel pockets, as well as monos with 'bifin' footpockets, and to me it is clear that the open heel footpocket works better. The foot itself must be able to flex to transfer power. With the bifin footpocket, the foot cannot flex. It is no wonder that Martin Stepanek chose open-heel footpockets for his latest record attempt, and he had easy access to both types of fins.

Think of the deepest dives in history:
Stepanek 96m, 100m: fiberglass fin w/open heel footpocket
Nitsch 94m, 95m, 98m: fiberglass fin w/open heel footpocket
Coste 90m, 92m: fiberglass fin w/open heel footpocket
Giankos 89m: fiberglass fin w/open heel footpocket
Musimu 87m, 88m: fiberglass fin w/open heel footpocket

Do I see a pattern here? What is the deepest dive ever done with a 'bifin' footpocket? To my knowledge the deepest ever is 78m by Mandy Cruickshank.

Similarly, look at the longest dynamics with mono; all with fiberglass fins and open heel footpockets.


Eric Fattah
BC, Canada

 

[feign]

Eric,

Earlier in the posts you gave a list of the top bifins. Were the Omer Bat fins among those you have tried to come up with that list.? I am curious how the bats compare to the C4's and waterway fiberglass. thanks

 

[Seal]

Originally posted by noa
Got some issues i don't understand... it seems many people use bi fins but mono kick with them. whats the use, if one preffers to mono kick, why not use a mono ?
Noa

You are right, in my case I should own and use a mono and I will get one. But for now I feel comfertable training with bi-fins. I like to be out swimming for 3-4 hours at a time. I don't know how well that would be for my feet? I think I read that Eric F. had some foot problems a while back because of over use of the mono's?

Well another problem was that I thought I would get some perfomance/limit dives in before getting the mono.

Jyri from special fins wrote this to me
"And if you intend to use mono for competition, then please:
Personal best in constant weight, if possible: m
Dynamic, if possible? m (you need it basically for dynamic?)"

And I haven't even got any dives where I have pushed myself even remotely so I thought I would get some more experience before getting a customised monofin. Am I wrong? should I be thinking of switching now to get the style right from the very start?

 

[derelictp]

I think that it's good to start with soft bifins.

If one starts with a stiff mono the best technique will be hard to accomplish, I made this mistake and after 3 years of monofinning I found that training with soft bifins have given me a real boost in my tech.

The better my tech have been the softer fin I wan't.


About fins/footpockets:
I have a blade which I put Sporasub footpockets on and it was so soft that I hardly got propulsion, the Sporasub pockets bent.
I switched to a FINIS footpocket and the fin was very good but almost a little bit hard. This is the fin I use now and it's an own produced carbon mono with 18 degree angle.

What I would like to say is before we get a footpocket where the foot is PERFECT connected to the blade we could use PLASTIC fins because one of the flexing parts in todays fins is RUBBER.

I have put very much effort in making/testing/buying fins and my problem is that it's hard to find somebody who is good at working with plastic/rubber and can easy make footpockets. Is there anybody out on this forum who knows who's making OMER/Sporasub pockets, if so I want to make contact and show my drawing of what I belive should be the perfect pocket....

(I've also found that an open heel solution is preferable but my construction differs much from todays open heel footpockets)

 

[Murat]

hey seal, how do you depart from bottom without touching with fins to the bottom? Do you use your speargun's tip? and let me remind you something, these fins have two year warranty so don't try to over-protect them in this 2 year period to see if they really will survive after 2 years

 

[Pablo]

derelictp:
Going this way, your feet are made of "meat" and softly joint bones... the only good way to join your blade to your body, is to screw inserts onto your tibias... not recommended!

You could mold any resin to the shape of your feet... something like 2 component polyurethane can be obtain in many degrees of flexibility (40 to 70 could be perfect), and they mold awesome. Could be a good start for a kit "DIY foot pockets"... could work!

A base to screw to the blade, an external shape and mold release wax! stick everything around your feet/socks (inside a plastic bag... or something like) and wait until set (1-2h). 48h later you have custom fitting foot pockets for your mono! glue the back straps to hold your feet inside... and done!

If the fitting (on swimming position) is perfect, hardness shouldn't be such a problem.

:duh :duh :duh

 

[derelictp]

I have made some (5) footpockets the way you described. I would like to work with a PRO on this to get better/faster results.
I have used 60-75A rubber.

A base screwed on the blade is very bad for the blades stiffness/bending line in my tests, it's very very imortant that the blade in all it's length is flexing and then it's very hard to get the BEST flex.

Thanks for your input though!!

 

[DeepThought]

Bi-dins & monokicking / carbon vs. fiberglass

I don't think that mono-kicking with bi-fins is wrong.
I descend/ascend with normal bi-fins technic, yet on the bottom, or even if gliding, if I just need another small propulsion, or a small change of course, I'll mono-kick. It feels like it takes less effort/create less co2, and moves me a longer way. It also feels like it helps me ride a current longer.
If you think about it, from a neutral position, a monokick is to move both legs (and body) in one direction, and then returning it back to the same posture and keep gliding (well, roughly), with bi-kicking you need to move both legs more than once to get the same propulsion, and getting the legs back to that neutral position doesn't create as much propulsion because it's not a complete cycle. so I feel atleast (I hope I managed to describe it).
Because you use other muscles, it might also keep the legs more fresh for the ascend, though I never had leg fatigue, so I can't really tell.

About carbon vs. fiberglass. I don't know which material has the best properties, but fiberglass is much less fragile and costs less. As long as carbon will cost as much and stay as fragile, fiberglass will be on the market.

Anyway, carbon/glass, bi-kicking or monofining, arms up and down, monofining style: more torpedo, or more "spanish dancer" ribbonish style, it seems that different speeds and different bodies require different styles.