Amazing Underwater Flight!

[ricki]

There have been some updates on Tom Lightfoots use of the Aqueon in a free diving competition on http://forums.deeperblue.com/freediv...st-past-6.html

Originally Posted by trux

I just added the results of the last CAFA competition and see that Tom Lightfoot competed in DYN and in CWT with the Aqueon! I do not know whether anyone else ever did, but the results are quite good (rather close to Tom's competition PB's in DYN), and may be well unofficial Aqueon competition records (100m DYN and 40m CWT):

APNEA.cz ranking - CAFA Western Regional Competition II 2011

I wonder how Tom managed to do the DYN turns - in a pool with shallow ends it may be quite challanging with the Aqueon.

DYN 100 m With Aqueon 09/18/2011
This is swimming horizontally in a 25 m pool for distance.

CWT 40 m With Aqueon 09/17/2011
This is a vertical free dive with constant weight

Originally Posted by trux

Just got some new details about Tom's performances with the Aqueon: the DYN swim was in a 25m pool with the ends 120 cm deep! It must have been pretty challenging since the rear rigid blade is exactly 120 cm wide too! Additionally, the fin is quite heavy, it means all those turns certainly cost Tom quite a bit of energy.

Originally Posted by Tom Lightfoot

Hi Trux and Rick,

I'd been toying with the idea of competing with the Aqueon since I got it. I spent a fair bit of time training with it three years ago but haven't used it much since then. The CAFA competition seemed like a golden opportunity to put some numbers up despite a lack of recent training with it.

To be perfectly honest, the Aqueon in its current form is no revolution in underwater propulsion. The improvement in efficiency is more than eaten up in increased drag, incredible mass (>20lbs) and difficult maneuverability. Still, it is a fun device to fly and I'm glad I dusted it off for the comp.

The constant ballast dive was the most daunting, both for me and for the organizer. The wide wings of the Aqueon don't mix well with the lanyard and the descent line. One has to be keenly aware at all times where all of these things are, especially at the start and turn. A back flip with head to the wall is the only way to start as it finishes with the diver facing the line with minimal risk of entanglement. The sink phase was very slow so I had to pump the blade occasionally to keep some forward momentum. At the turn I had to swing my body well clear of the plate to avoid knocking the bottom camera. On the start of the ascent I typically feel like I don't have much power against the negative buoyancy but at 20m and shallower I feel like I can outrun anything with the Aqueon.

Dynamic apnea presents its own challenges, especially in a 25m pool. Obviously the turns are inherently difficult. The only way to turn is to keep level and straight. Any tilt would drive the wing tips into the bottom and any bending of the knees would hammer the front blade into the bottom. It is therefore necessary to scull with the hands to finish the turn. The aqueon is not very efficient at low speed so it is necessary to push a bit harder than otherwise ideal.

The Aqueon takes a life of its own at medium fast speed. The blade suddenly grabs the water and you propel yourself more by leaning against the blade than by moving it. You have to forget everything you know about the monofin; pump entirely from the legs and relax the upper body.

Tom

Originally Posted by ricki

Thanks for undertaking this experiment and reporting back on your approach and impressions. Congratulations on your world record Aqueon performances. You are the first to do so to my knowledge.

What aspects of the Aqueon design would you work in modifying for DYN and CWT if any? Things like going to composite materials to reduce weight (momentum too though), changing the foils to a swept back tapered configuration (more whale caudal fin-like) with a deflectable trailing edge vs. the current orthogonal wooden foil setup relative to the kneel of the Aqueon, positive securing of the foils to avoid accidental loss during performances. What other ideas come to mind? Cal told me that others had tried some of these mods with limited change in performance characteristics. Then again I doubt they were concerned about competitive considerations.

Thanks and congratulations again!

Rick





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[ricki]

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Originally Posted by ricki

Good points, particularly about sliding the foils out on the axel by accident. Worse what if one falls off at depth?! Something more positive with less friction would be a strong advantage. Your suggestion of a mobile ankle mount is intriguing if I follow your meaning. That would allow more deflection of the front foils with less effort, hence easier, tighter and faster turning of the Aqueon. Also, you probably noticed the boards can become uncomfortable, it would be nice to avoid that with your ankle mounts. As DARPA ran off with Cal's idea, some study of their more contemporary design would be helpful in considering changes.


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From: Ares Homepage

Sweeping back the front foils would impact your displacement in strokes but it would also reduce drag. I think the ability to feather the trailing edge of the foils would provide some strong advantages as well providing less turbulence through strokes. The rear stabilizer serves to provide resistance to excessive pitch oscillations through the sinusoiding of the front foils. You simply need something of adequate reactive force to stop you from seesawing in place through the motion of the front or propulsion foils. Going with symmetrical foils made sense from a production and performance standpoint using wood construction decades back when Cal developed this. With synthetics you could variation size, aspect ratio, etc.. Perhaps you could come up with something which would provide the necessary pitch stabilization without the excessive width. Perhaps something longer again with trailing edges that could also be feathered. I don't think fins would provide sufficient surface area to do this at least not with the current front foils. In the case of a monofin, I am less certain. When I mentioned narrowing and increasing the length of the stabilizer I was thinking of something roughly in the shape of an odd monofin. It would need to likely have more blade resistance than a monofin you would like to use on its own though, I think? It seems if your stabilizer was too long it would create excessive drag from projected area. This is one good reason to try to stick with narrower, longer foils as are currently in use.

Good stuff to work on! Other ideas out there?

Rick