DYN: Neutral buoyancy "weight" in neckweight?

[baiyoke]

Hi.

Just had a thought: I don't glide a lot in DYN for many reasons. But I remember from other threads people talking about a heavy neckweight being good for a long glide (perhaps mostly from push-off at ends of pool). Also a heavy neckweight might be good if there's a tendency to be tail-heavy and "skew" off sideways with feet/monofin.

So, I was thinking, it might help with a lot of neutral weight for a more consistant speed, direction and long glidephase... So fx, a bit exagerated, I could pack 20 kg lead + 17 liters of foam. Then I would have 3 kg weight buoyancy-like, but 20 kg to keep inertia. It might give a better flow.

Offcourse I would have to have good timing at turns, to not loose too much inertia there. And it would have to be very streamlined, not to make too much drag.

But it might give a better flow-experince...

Has anyone experimented with that?

 

[Simos]

I've seen this mentioned before here and there... I remember Eric and a few others said they had tried it (not to that extend but with 7mm if I remember correctly. Opinions/experiences seemed to be divided...

 

[Simos]

By the way I think the main benefit has to do with the push-off from the walls. If you exclude that, I doubt it helps to carry that much weight, probably the opposite...

 

[fabikp]

From the pure physical point of view it cannot help, just the opposite. But in practise - who knows ?

 

[trux]

From the pure physical point of view it cannot help, just the opposite. But in practise - who knows ?

I'd tell that it is just the opposite - from purely physical point of view the weight helps both at the push off the wall and druing the swim too, especially at DNF. The push offs are much more efficient than propulsion in water, hence the long glide may help you saving O2. At the swim, the high mass helps keeping the speed more constant, it means that at the same mean velocity, the speed peeks are lower than at a swim with low mass. And since the drag grows with the square of the velocity, reducing the velocity peeks saves energy too.

In reality, there are more aspects - including the comfort; the maximal muscle power you can exert without losing more than gaining; the additional drag due to the added weight and buoyancy; the influence on the elasticity of the wetsuit; the habitude; etc, etc. Hence, you need to experiment what suits you the best. Personally I did, and found that extremely heavy weight does not bring any interesting gain, but then again, I would have to train with it longer time, and optimize the style and equipment, to see a really objective result.

 

[fabikp]

Sorry, trux, but I hope physical statute of keeping the same ammount of energy cannot be overcome. In particular phases of the swim you may be right but overall it shouldn´t help. Like Simos tells, experiences was divided. Pavel

 

[trux]

Sorry, trux, but I hope physical statute of keeping the same ammount of energy cannot be overcome.

Sure it cannot, and it also isn't. But you have to realize that you are not swimming in vacuum. There is also drag, and under water it is very significant. Hence the speed and the propulsion efficiency have much more important impact on the energy expenditure than the acceleration of the same mass would have in vacuum. So, using the more efficient propuslion (push-off vs. swim) and reducing the velocity peeks indeed saves energy while no physical laws are being violated

 

[fabikp]

Yes, it does, but the push off needs more energy with more weight if you want to utilize greater momentum during glide and pushing more weight during swim consumes more energy too. But I must admit, that it would be neccessary to measure all parameters of the particular performance to know exact energy balance.

 

[trux]

At the few kilograms we speak here about, the difference in the energy spent on accelerating the extra weight it is negligible in comparison with the mass of water you move in front of you at each turn. But in the same time the momentum you gain allows you to glide longer, saving so energy during the swim phase when the propulsion efficiency is orders lower than that of pushing against the wall.

 

[baiyoke]

Agree with Trux all the way.

I did not think of a thick suit + weight, allthough that is also interesting. But to get the most benefit, the weight I think should be as much in front as possible, and because of the need to avoid being heavy in front, the boyancy should also be as close to the weight as possible I would say. Perhaps like a very tall triangular hat, wich would fit the arms posistion, especially in DYN:



(http://www.menards.com/main/store/2...re/3256/ProductLarge/sidepin_sp-99427_428.jpg)

Or perhaps more like this:



(http://www.raltech.co.uk/images/Helmet1.jpg)

 

[Simos]

I think the coolness factor should be weighed against any gains in performance

 

[baiyoke]

Lol Simos

Things can definately get ugly, allthough I think Aida would take steps quickly to avoid that...

Examples from bicycling:

http://www.recumbents.com/wisil/racing2002/Michigan2002-Edge.fairing.jpg

http://www.motoredbikes.com/attachment.php?attachmentid=34889&stc=1&d=1331482987

 

[B-J]

In addition to increasing the weight of the diver, it should be possible to improve the hydrodynamic of the human body. In DNF you could put a lot of foam on your lower back and get more streamlined. Depending on how big your ass is I really, REALLY can`t understand why AIDA doesn`t make a rule that restrict this. For instance max 5mm suit (or other material.) Isn`t that what they do in triathlon? It is such a waste that athletes use time and energy pursuing this aproach.

 

[Mullins]

They're probably waiting to see if anybody bothers to do it, B-J. It's been talked about a lot over the years but nobody seems to have had the inclination to actually try it, except perhaps for Wes - who only went as far as strapping both legs together.

Aside from the effort involved, the thought of looking like an oversized rubber phallus probably puts people off a bit too.

 

[baiyoke]

Weel, I haven't been in this sport for long, but it is not my impression that athletes are taking big steps towards this... I haven't seen streamlining in other than the suit and the neckweight.

I'm sure aida will take action if it happens (if it gets too crazy). But maybe it is difficult to precisely formulate rules without seeing the need first. Until then, and even beyond that point, it is still entertaining to think about what COULD be done in this wonderful sport Especially in the science-forum:

I can know see that a kind of head-held fairing could be made much easier than the before mentioned lead+foam. All you need is..... water. Imagine a helmet a lot like the bicycling time-trial-helmets, but a double one. Going down the back, and also going out in front, closing the gap between the arms. It could be made of any material almost (doesn't have to be lightweight), and function as a neckweight of say 4 kilo. So it is relatively lightweight on land. But in water it is filled with 20 liters of water, and then you got a 4 kilo neckweight-fairing with 24 kilo to keep inertia in the front, streamlining the body.

Another very simple solution for contant in a "normal", but heavier, neckweight would be sand. If you put 10 kilo of sand in a fat-boy neckweight, it would weigh approximately 5 kilo when submerged, but give 10 kilo of inertia. Probably not very streamlined though.

Anyhow, I have seen people working on different kinds of neckweights than the tire-tube style, because they don't like it. Perhaps a helmet-like is the future, and then adding some streamlining would be a small step. Except the risk of looking like a christmas elf...

 

[baiyoke]

Aside from the effort involved, the thought of looking like an oversized rubber phallus probably puts people off a bit too.

rofl

Doesn't put off Herbert in the quest for depht though... ;-)

I was thinking more in terms of something like the "Alien"-look...

 

[trux]

I guess that one of the reasons people do not use any such fairing is that it is very impractical and unconfortable. So what you perhaps gain in drag, you may lose twice in comfort, it may limit your feeling of the water, hinder your turns, or distract you otherwise. But I think it is good the rules are still open to it. If someone comes with such a fairing that brings more than takes away, why not. We can then make separate categories, or ban it, but it would be a pity to ban it in advance before seeing it.

Anyway any such rules or measures against fairing are rather futile. I already found how to bypass it even if it the fairing is banned in the rules. Look at my photo from the WC09 (© Kimmo Lahtinen). There is no artificial fairing or artificial added buoyancy. All 100% organic matter. Well, I admit the shape still needs some fine-tuning, but I am working on it:

 

[baiyoke]

He he he... lol Trux

BTW I've allways thought that freediver women look more streamlined, with their naturally curvy figure in a wetsuit, but I suspect it only looks that way......

This is MY vision of a combined future fairing-neckweight (well, something like that...):