Freedivers getting softer?

Thanks a lot neshamah. Just one of my stupid questions!!!!

Sometimes it takes a total ignorant to come up with a revolutionary idea. I guess this was not it though HEHEHE

breaking the ice

Don't worry Chaca- I do that a lot - sometime I come out with a insignificant question- but is just to break the ice.
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Ahy veces es bueno romper los esquemas.

buen dia

Daniel

Muchas Gracias Daniel. Como que hablas español?????

hi

Oye muchacho si eso es lo que mas hablo soy cubano<AQUI> en el deeperblue es que estoy praticando my writing! con ustedes this is like a school for me-

bueno saludos
Daniel.
ps- o my abuelo era de las palmas gran canaria

Thanks Daniel!
The way you explained how the downkick is the primary source of power made a lot of things fall into place for me as I have been struggling a bit as I transition into longblade fins. In some respects I think I had it backwards because I find it's easier to cover great distances with longfins while on my back. Now I'm even more convinced that I simply must do some weight training on the muscles that propel the down kick (as well as dive more).

Might be a good thread or post if there is not one already: Which are the exact muscles primarily used in finning? What are the excercizes (particular Nautilus machines, free weights) that would build the muscles involved. Of course I know diving itself is probably the best, but we can't be in the water all the time.

It intrigues me that there is often references to the angle of the footpocket and the blade are required to keep the blade in line with the body. Now the obvious thought here is that the blade and legs will create the least drag in this position, while motionless. But there are two points that suggest this may not be relevant to constant ballast diving:

1. We only perform a few kicks to the point of sinking and are not required to drift in between kicks and then when sinking we are not attempting to gain a bunch of speed, so the drag is irrelevant and possibly helpful to maintain a slower speed.

2. On ascent, we kick steadily and with consistency. Therefore there is no moment of fin drag, since every moment is part of the motion of the kick.

Any thoughts on these points?

Also when you look at body structure of many dolphins, whales, and other acquatic animals, the blade of their fin does not seem to naturally follow the line of their body or the line of least drag. Ideas?

Re: the upbeat and donwbeat

Upbeat- The upbeat has to be viewed primarily as a preparation for powerful downbeat. Most...

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Interesting idea here, which seems like the most obvious, but maybe that is the problem. Maybe we have not done enough exploration on how to maximize efficiency with the upbeat and the downbeat, in terms of multiple stages of propulsion. The statement quoted first says we have to view the upbeat primarily as preparation, and later says MOST coaches believe in this. So, this also means that leaves room for some who believe otherwise. It seems very likely since there are trainable muscles used in leg curls, that the upbeat could be viewed as a dual purpose preparation for a strong downbeat and just as important an effective continuation of thrust.

It would be interesting to see what proportion of thrust a dolphin achieves on their downbeat, this being the more flexible direction of their tail, when compared to the more rigid upbeat. We have the rigid downbeat and flexible upbeat. If we saw the proportion as being a significant amount, then this might suggest there is the possibility of us developing a technique with a significant proportion. Of course we have different physiques, but it would be interesting if this has not already been explored thoroughly. And I don't think we can safely assume that just because people have been fin-swimming for a long time. Often energy is only invested into the tried and true techniques as long as they are keeping competitive with the pack.

My thoughts.

I don't agree with Daniel's statement. I realise that you don't get the same power on the upstroke, but to say you get none at all??
Do you really think in finswimming when trying to go as fast as possible they wouldn't take advantage of the upstroke as well ?

I've spent more then a year training with a finswimming club. With beginners that use legs only you can really see they only get power on the downstroke. It almost looks like they slowdown on the upstroke. When I watch some of the good finswimmers the whole motion is very smooth and constant speed. With myself when I first felt I was getting the hang of it was actually when I did get power from the upbeat as well. It doesn't come from the legs, it comes from the body, the hips coming down, so from the back and stomach muscles. You need to have good technique, and flexibility.

Even if you had no fin at all this motion provides some propulsive force. Watch normal swimmers take of from the blocks. Perhaps with the good finswimmers the propulsive force is like %70 downstroke %30 upstroke. Or maybe even 80/20. Still when you are talking racing or freediving even %20 is something you don't ignore when every m or second counts.

Cheers,
Wal

If I remember correct (Bevan should remember), Peter Pederson likes to have an angled fin, saying that having a more symmetrical stroke is reasonable and works better for him. I think he must have tried a few monofins in his life.
Although his main expirience is in dynamic, it seems to convert to depth quite well till I left Dahab.

hi

Walrus
You don't agree with me??

this is not my statement it come from a very well known swiiming cough and writer

this people are not going to say anything that hasn't sudied first by

well

70/30

I belive that one should use the upstrike as good as possible and I also belive that 70% of the propulsion comes from the downstroke if a good tech. is beeing used. I agree with Walrus that the power comes when the whole body makes undulations wich is driven from the abdomen, the hips and the back.

The ideal fin would be very soft on the upstrike and stiffer on the downstroke but I have no idea how to make such a fin

I definately belive that an angle in the blade is beneficial.

Angled is the way to go... for what?

I can understand saying this for Dynamic, much like fin-simming, where an effective glide is integral to the swim. However, remove that for a constant ballast dive, and then it seems all you are left with is, how does the angle assist on the actual stroke?

I think most of these fins are tested under dynamic conditions, and not near as much consideration of constant has been used. It would be interesting to see what we would find the most efficient fin to be if it was only tested using constant ballast technique as opposed to swimming technique.

Neshamah,

Walrus can disagree with you, because your words implied you agreed with the coach. Even though the ideas were based upon a coaches words, that does not alleviate your opinion of agreeing with the coach. So, Walrus plainly disagrees with your agreeance, which also implies he disagrees with the coaches suggestion.

Fair enough.

Hi Tyler

My opinion is that with an angled blade you can fall like a "dart arrow" in a very relaxed way. For me this means an easier descent.

The more hydrodynamic you can fall the less amount of ballast you have to take down. That means an easier ascent because I am less heavy at the deep water.

If the swimming can be done more effective that's the third argument.

What do you think, Tyler?? Is there something that I have not thought about here:hmm

My opinion is that with an angled blade you can fall like a "dart arrow" in a very relaxed way. For me this means an easier descent.

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We do not naturally keep our legs straight in relaxation. They actually prefer to remain bent, slightly. Have a look at no-fin dives during the sinking phase.

The more hydrodynamic you can fall the less amount of ballast you have to take down. That means an easier ascent because I am less heavy at the deep water.

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In my opinion, coming from a cold water diving location where generally people wear 3-7mm suits, the ballast is mainly used to overcome bouyancy, and in doing so also has you weighted plenty for the sinking phase. Meaning, streamlining on the descent is fairly irrelevant and depending on your weighting you might be too fast.

What you are suggesting, is that with bent legs and a non-angled fin, you would have to add weight above and beyond that necessary to overcome the bouyancy of your suit and lungs, and to obtain the desired descent speed at depth, correct? I have never heard of somebody being in a scenario where this occured. Of course maybe it has... it would be interesting to hear feedback on this.

But then it depends on what descent speed you expect. There is variances in belief as to how slow/fast should one's descent speed be. So, to this point, I would have to say that the drag, in my case, is irrelevant due to the reasons above. I wear enough weight to overcome my bouyancy and that happens to achieve a comfortable descent speed, with bent legs and a non-angled monofin. So, if you differ than that, then for your situation the streamlining could be effective, however by demonstrating that I do not require this, we would have to agree that angled fins, specific to this reason, can not be claimed necessary, only helpful for specific techniques, where the best technique is still debatable and not proven. Possibly remaining personal.

If the swimming can be done more effective that's the third argument.

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This argument I see only being valid if, by swimming we are including vertical movement through water in the definition of swimming and then only if, we determine that somehow it is more effective. The latter which is what I do not see any clear argument for. I am only addressing this argument towards constant ballast, since it is a totally different form of swimming.

If we can demonstrate that the angled-fin, may not undeniably provide an advantage in this arena, then we have to accept that we may require different fins for the different swimming activities. Or this may inspire ingenuity towards designing a better fin, with the technique of constant ballast driving such a design.

Neshamah suggests fin-swimming has been studied, yet we probably all recognize that there has been much more interest in fin-swimming in terms of humans and hydro-dynamics as opposed to the same for constant ballast. The results could be dramatically different. If it is correct that human finning has not been studied towards fin angles with constant ballast differences in mind, then it is safe to say, that angled fins may not be more effective when applied to that practice.

So, those are my thoughts.

Cheers

What you say make sense Tyler!! I understand your thoughts and I agree with what you are saying. It's just not working for me this way.:head

I belive my point of view is much "colored" by the fact that I have very stiff feets. When I used straight fin's my legs had to be more than 45 degrees bent to get the fin in line with the body. I also "spinning" and turning if I relaxed with the straight fin I used back in 2001 so an effort has to be made to keep myself in the right position.

I like falling at speeds of approx. 1.2m/s at the deep part of the dive and I dive much in the cold waters of Sweden so we have the same situation.

The true is probably that some bodys are more suited for straight blades and some for angled blades.

Thanks for good thinking and explanation, Tyler!!

Cheers

Originally posted by tylerz
In my opinion, coming from a cold water diving location where generally people wear 3-7mm suits, the ballast is mainly used to overcome bouyancy, and in doing so also has you weighted plenty for the sinking phase. Meaning, streamlining on the descent is fairly irrelevant and depending on your weighting you might be too fast.

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Tyler,
Of course where I dive we need weights to overcome the bouyancy of the suits, however what would be the problem with sinking "too fast?" I can see the problem with overweighting ect, however in my opinion the faster the sink phase the better without increasing ballast. Unless equalization is a factor, then any streamlining would be free speed and free depth. The diver would reach the target sooner leaving more o2 for the ascent. Once again to clarify, I'm referring to streamlining during the sink phase, not increasing weight. If there is a problem with "too fast" that I'm not aware of, let me know, because I've been working on streamlining to that effect.

All other points make really good sense though. I've often thought that CB diving is so much different than dynamic that different fins would make sense. In fact I never use my stiff CW fins for dynamic, but rather a longer softer pair.

Aaron

I have no idea about fin angles, however as stated, I think that dynamic and CB are different enough to warrant different fin angles and possibly styles. I have thought about a mono that is very wide and not very long. (high aspect ratio) This style of wing is extremely efficient in airplanes (ie. sailplanes/gliders). However a style like that would also need to be fairly rigid to prevent the blade tips from just flexing up on the downstroke, and likely a different angle would be required for the up and the downstroke. Still to many problems with a design like that.

Good thinking all! I'm enjoying this thread!
Aaron

Hey Aaron,

Yes, good question! I think it has been mentioned elsewhere but the main issue is to do with squeeze, and secondary is equalizing.

At crushing depths, it is always nicer/safer to give your body time to adjust to the opposing forces (the lungs collapsing versus the rib cage/diaphragm/etc. naturally inclined to remain open). It is quite common that a dive greater than a previous PB, by only a few meters sometimes, is enough to cause squeeze in a diver. This demonstrates the sensitivity of change on the body, that we are dealing with. This also suggests, that it is useful to maintain a gentle rate of change.

Taking into consideration that as we go deeper there is less physical change due to the compression of air, it is then understandable that we work ourselves very gradually to the point of our maximum flexibility, before squeeze. So, the rate of change is constantly slowing down as we get closer to our max. This reflects, us dramatically slowing down our descent, if the change in volume was linear instead. Recognizing this similarity emphasizes the importance of our speed as a direct effect on lung squeeze.

There is the theory, as well, that after packing one has a higher risk of squeeze during the initial phase of descent, which can be eliminated with a decrease in speed. Pete Scott has the explanation on this one.

Anyhow, those are my thoughts so far.

PS. My descent rate is 0.7-1.0m/s; thinking of stabilizing it at 0.8m/s.

Cheers,

Tyler Z.

Thanks Tyler!

That explains it perfectly. My sink rate is about 0.9 m/s, but maybe I should be slowing down... I did get a squeeze about 3 months ago! I've re-read Peter's article on lung-squeeze since then and have been streching lots before diving, but I now remember him saying that speed of decent was a very big factor.

Thanks for the explanation,
Aaron