Monofin technique! Dynamic

[B-J]

Originally posted by Trux:

The ideal would be a very thin carbon construction of both the blade and the bridge between foot-pockets and the blade for adding the extra angle. I do not know how much your fin weights, but I guess that together with the weight it might be around 5kg, perhaps even more. Now, when you multiply the mass by the number of kicks during your swim, it represents already a pretty important amount of wasted energy.

I don`t think you would save that much weight if you made the fin in carbon instead of fibreglass. Isn`t it the rubber that weighs?

And then an additional question: Why are there made fins out of carbon? Very few monofins are made out of carbon, but there are plenty of bifins. I was in a store and the price was four times higher than fibreglass for the actual carbonfiber"texture." I found this on the Triton webpage.

Thus, for a fin as an energy conversing element the most important property is its ability to take over the energy in a form of reversible flexural strain in the most efficient way and to transfer that energy to water. As in a jumper’s pole or a bow the accumulated energy is transferred to another object. The best material for such energy system is the material which is able to accumulate maximum energy while having minimum mass. On the assumption that the specific index of flexible strain for aluminum alloy mass unit is 1, the similar indices for titanium, carbon and fiberglass are 2, 4.6 and 17 correspondingly. Therefore, it is desirable that fins for active swimming to be made of fiberglass

Triton Underwater Sport Equipment

 

[trux]

I don`t think you would save that much weight if you made the fin in carbon instead of fibreglass. Isn`t it the rubber that weighs?

Yes, and that's why I think it should be replaced with carbon or another material allowing less volume and less weight. I, of course, do not mean making the footpockets in carbon, but rather replacing those huge and ugly rubber fillings between the footpockets and the blade with something less voluminous and quite light. Or mounting the blade in a copletely different way - on the top of the feet; fixing on a prolongation of the shins; using lightweight profile; or something similar.

As for the weight of a carbon and fiberglass blades - that can make a nice difference too, but frankly told I cannot comment on the specific index of flexible strain referred by Triton - I did not manage to find any source speaking about it closer, so am not sure whether the information by Triton is really correct. Usually I heard the opposite views. I admit though that I did not see any scientific data, so it may have been subjective or biased opinions.

 

[laminar]

What about an airtight compartment of thin, flexible composite material and filled with gel that is slightly less dense than water. This would be the fairing on the monofin. The whole thing would then also have small airlock/o-ring openings at strategic places.



Simply insert lead shot one pellet at a time to create the perfectly weighted/balanced monofin. The lead shot will stay in suspension in the gel. Add more lead shot to make it negative.

Big plug to drain the whole thing and start all over again.

=Pete's open source high performance mononfin design. Any prize money won with the design must be donated to the "Pete's Beach Life Fund" charity.

 

[hunlee]

Hi all- Very interesting thread. Very technically advanced, I'd like to throw in a another angle...
I have been working on my mono DYN technique for a while and kinda have the Elisabeth style going quite well. Then I did a dive a few weeks ago at the Nordic Deep comp in Sweden, funny enough with Elisabeth in the lane next to me
I'd had a week of competing with daily maxes and DYN was an extra at the end, I decided to really just
focus on relaxing and not even think of technique, distance or anything technical.
Well, I had my coach the judges and the girls diving with me baffled! It was the longest dive I'd ever done, around 3 minutes. My technique was terrible... but I did a new PB of 150 and came up so strong my coach reckoned I could've done quite a bit more... and this fascinates me.
Seriously my technique was atrocious... moving arms up and down, bent knees, looked like an untalented beginner! So how much is feeling good and relaxed and how much is technique and equipment? 50 50? 40 60?

And from this my tip for those not pushing world records is to work as hard at feeling goooooood underwater as you do on technique.

 

[trux]

What about an airtight compartment of thin, flexible composite material and filled with gel that is slightly less dense than water. This would be the fairing on the monofin. The whole thing would then also have small airlock/o-ring openings at strategic places.

For the physics, I mean the loss of energy by building momentum / accelerating the fins, it is not its buoyant weight in water that is important, but the real mass (as if measured in vacuum). So using 2 or 3 kg of rubber, would cause the same energy loss as the same mass in neutrally buoyant gel, or the mass in lead.

Bill is though right that not the entire energy put into the acceleration of the extra mass is lost - the momentum stored in the extra mass then helps in the second half of the kick (the decelerating part), so the muscles do not need to drive the blade so strongly there - it will continue in the motion thanks to the built up momentum. That's true unless the momentum cumulated in the mass is that big, that muscle force needs to be used to decelerate it again. Still, light fin would be an advantage.

 

[sayNO2o2]

hey i just want to say thanks for all the tips!
i am kind of new to mono fins and dynamic and have picked up alot of great info just reading this thread. now looking forward to hitting the pool again to try some of this.

and a big two thumbs dave for those vids. thanks

 

[bite ya]

Going back to the relaxing bad technique message hunlee wrote, i agree with this. I have been really trying to perfect a technique that works for me and taken a lot of info out of this thread and messed about with it for a few weeks now in the pool. Whilst my distances are not great i did a simular test the other week and just tried to get back to feeling relaxed again, my dive time was far greater than it ever is but the distance remained the same. This made the experience more enjoyable and not so much like "training, here we go again"!!

Every month i take one training session out and go back to some basics, remembering what i started all this freediving for....enjoyment.

Saying all this, technique is so important as we all know and hopefully people like Mullins will aid lead the way in future fin design that will benifit us all as Herbert Nitsch is doing with his pioneering ideas for no limits.

Mullins, Trux and everyone else keep going cos i learning heaps!!!

Chris

 

[sayNO2o2]

hey i see a few ppl are wearing fast skin stuff. do most ppl wear a swim cap as well?

 

[bite ya]

I dont have enough hair to warrent wearing a cap!! I wear a cheap long john wet suit from Decathlon that holds a ton of water but hey it's all i can afford right now!

I will eventually get round to buying somthing more specific for dynamics...