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Counterbalance

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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samdive

Mermaid, Musician and Marketer
Nov 12, 2002
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We are trying to design a counterbalance retrieval system for saltfree - ideally one that can be used to "follow" the freediver up on every ascent rather than one just use if they don't surface - we have a huge, fixed pontoon to dive on a flat lake from so size is not a problem, what is a problem is having someone strong enough to pull the counterbalance back up for the next dive

has anyone designed anything like this? anyone got any ideas? we are working to about 80m depth but with the bulk of dives between 40m and 50m. Divers are all on a lanyard.

At present we use full scuba cover and FHOF safety but this is getting expensive and tricky to organise so we're looking for an alternative.

any ideas gratefully received

Sam
 

Longfins

Well-Known Member
Oct 28, 2001
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Hi Sam,

The counterbalance as the Performance Freediving folks set it up is roughly as follows:

2 long beams w. various braces in between (similar to Worlds)
2 sailing clutches facing opposite directions (clutch arm facing each other)
2 sailing blocks (pulleys)
3 sets of weight. One on the competition end, one on the counterbalance end. The two weghts give the line equal tension and allows for depth adjustments up and down between dives. The third is carabinered to the counterbalance end but sits on the platform or boat so when the need comes the weight is dropped and catches on the second weight at the bottom. The 2X weight on the counterbalance end will then bring up the competition line. Ex. 3X 30 lbs weight sets = 30 lbs on comp end and 60 lbs on counterbalance end when activated. Length marks are drawn on the beam to easily adjust the rope length.

This set up is usually used for deepest-diver-goes-first, and the line is adjusted manually - comp line getting shallower and shallower - until the last dive, then the counter balance end is hauled up only once. It doesn't really allow for the counter balance to follow the diver up, because it's difficult to haul double the weight when the dive is over. The question is, is there really a need to do so? If that's the case, a winch would be a good investment.


Just some ideas.

Peter S.
 

Longfins

Well-Known Member
Oct 28, 2001
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Here's a quick illustration of one end of the counterbalance. The other side is a mirror image of this end, i.e. the rope can be locked to prevent movement in either direction.

brown pieces = 2"X6" beams and reinforcement pieces (many omitted for clarity)
gray = steel bolt
white = sailing clutch
red = rope
green = sailing block / pulley

hope this helps,

Peter S.
 

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jome

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Jul 5, 2004
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Just a thought. But if you're using this in freshwater, ie no currents, I guess the weights don't have to be that big? Coupled with a pulley it should be no problem adjusting it and hauling it up.

Or you could attach a pony+liftbag on the counter balance and then have one diver drop down and fill it at the end of the session :) (or attach a timer or some kind of remote to it)
 
O

octopus

Guest
It is worth asking Alun. If I remember correctly, the lads were experimenting with counter balance system at Dorothea. It worked rather well.

ideally one that can be used to "follow" the freediver up on every ascent rather than one just use if they don't surface

The principle of operation should be rather similar for system that "follows" the diver. It is just matter of when to activate it.
As for pulling the weigth up every time...well...it could be good training. :D
 
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donmoore

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Aug 19, 2002
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one that can be used to "follow" the freediver up on every ascent rather than one just use if they don't surface

Sounds to me like a DRUM system may fit the bill more than a counter balance. Eric Fattah started a thread on an in-the-water system http://forums.deeperblue.net/showthread.php?t=39062&highlight=reel+pole where he incorporated a reel and a pole. In that thread I suggested a commercial fishing bottom reel (frequently called bandit gear), because of extra strength and pull. Some of them have clutches for free wheeling. If you went with an electric, which might be all right in fresh water, you would have to check the retrieval rate.

Some local commercial fishermen make their own out of motorcycle wheel/rims, etc.. Since the diameter is fairly large, I would think, even if it had no clutch, you could reel it down fast enough to stay up with the diver. The trick would be timing the RPMs and coming up with a formula how fast you needed to go down and up.

If you put a weight of about 6 - 12 ounces on the line it would keep the line tight while reeling down without any drag on the diver. The desire would be to keep a little slack between the diver and the weight.

The idea is neat. The diver basically has a set time for the dive and they will arrive at the surface at the end of that time regardless if on their own power or by the DRUM system.
don
 
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Panos Lianos

New Member
Oct 31, 2004
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Hi Sam,

I agree with longfins: Is there really a need for the set up to be activated for each dive? Remember you are not talking about no-limits here, where the depths are really great. Maybe the best thing for you to do is to set up a system and only activate it if a dive takes more than anticipated, depending on the depth that each diver announces before his dive and his equipment (bi-fins, monofin, no fins etc).

You can have the counter weight hanging at a certain depth, so the safety freediver can swim over to it and release it when a dive takes more than it should and the freediver is still out of site. I will try to make a drawing and post it here, but my computer drawing skills are not great!

By the way, shouldn’t the whole thing be called “Counter Ballast” instead of “Counter Balance”?
 

Panos Lianos

New Member
Oct 31, 2004
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Here is the basic idea. The guy at 20m is the safety diver!
 

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samdive

Mermaid, Musician and Marketer
Nov 12, 2002
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thanks a lot guys - keep the info coming. I would like, ideally to bring it up each time but I know that might be tough. We are using a busy quarry and diving at least one weekend a month, usualy more so dropping it and leaving it is not an option...

thanks for the help

Sam
 

Longfins

Well-Known Member
Oct 28, 2001
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Just adding to the database: Here are some pictures of my current counter balance.

First picture shows the comp end - 25lbs bottom weight, light, bottom plate (lexan) on the line.

Second picture shows the two rope clutches that halt the line running either way. Note that the comp end off to the left has been deployed and is locked down. The counterweight end still has to be attached and dropped with the rope bag. My buddy is in there to provide a sense of scale.

Third picture shows the counter weight end, deployed. The comp end and the counter weight end have the same weight (25 lbs) so the depth can be easily adjusted by running the line through the clutches one way or the other. A 23 lbs counterweight is attached to the float with a snap shackle (small, below the pulley) and carabinered to the line. When the red loop is pulled, the weight is dropped onto the one below and together (48lbs) pulls the comp line and the diver up; the crash test dummy (me) was dragged from depth at around .65 m/sec.

Fourth picture shows the rig on my kayak. The separator bar is actually a extendable handle tha collapses to half its length, making it very easy to transport out to the site instead of dragging it out there. My buddy carries the other float.

Peter S.
 

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donmoore

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Aug 19, 2002
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I am preparing to build a counter system for use on a boat. A few questions. What is the reason for the large lexan plate? It seems like the large size would increase the drag in the event of a diver recovery.

With the so much under the water (the underside of buoy, the beams, the sailing block) doesn’t that make the diver have to orientate himself and try to miss it all in the last few feet of the dive?
Thanks,
Don
 
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Longfins

Well-Known Member
Oct 28, 2001
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Don,

Good questions.

The primary reason for a bottom plate is to prevent your lanyard from catching anything at the bottom - the light, a knot on the weight, etc. - a real danger. It only has to be bigger than the lanyard carabiner or line loop. Mine is a little bigger more for psychological reasons. It gives me a place to put my hand when I reach my 'target'. It's transparent so the light below it can shine through. It doesn't have to be that big (8" dia) at all.

The separation boom, ~9' long when completely extended, between the floats is the only hazard during ascent unless you can somehow keep it out of the water. You have a boat so - cool! When I ascend I make sure I can see the line behind my comp line so I know I'm in the clear. It's also your buddy's responsibility to steer you around so you are on the clear side.

Peter S.
 

donmoore

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Aug 19, 2002
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Thanks Peter,
That all makes good sense. What about the carabineer clip and lanyard setup? Should I use a marine snap clip out of 316 stainless with stainless spring, or an aluminum for like rock climbing? Seems a rock climbing clip, since it was not made for salt water, might not have enough corrosion resistance, but in the video’s I have seen, they look like they are using aluminum because the clip is light enough that its descend rate is less than the diver and is being pulled down by the diver.

It looks like in the Worlds they had another quick release besides the carabineer and the Velcro wrist strap. What is that? What about a swivel?
Don

PS Any web links of clips and other stuff would be helpful.
 

dallasdiver

Well-Known Member
Feb 3, 2004
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Don
This is a picture from which I copied Alun George's lanyard setup. Works well and can release instantly from velcro strap or snap shackle.
[ame="http://forums.deeperblue.net/showpost.php?p=417169&postcount=35"]DeeperBlue Forums - View Single Post - saltFree UK National Freediving Championships 2004[/ame]
 

Longfins

Well-Known Member
Oct 28, 2001
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Don,

The only competition requirement for carabiner is that it has a 1/2" opening (competition lines are typically 1/2" dia) and is non-locking. That's probably why you see in the comp video that the carabiners are climbing / aluminum kind; if you use SS carabiner of that size it gets to be expensive and heavy. Of course if you don't consider competition then you can use whatever you like. I use the lightest aluminum / climbing carabiner I can find, but it's anodized so it will resist the salt water a little longer.

At last year's Worlds they started requiring a diver-side quick release as there had been some prior incidents of diver lanyards getting caught at the bottom and kept the diver from ascending. You see a snap shackle at the diver wrist-side so one yank and you're free (I don't see it in the rules though). This safety feature was, of course, pioneered by own very own Alun George! :)

Peter S.
 

donmoore

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Aug 19, 2002
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Thanks for all your help. Here is an excellent science experiment of a kid that I thought might be of interest to some http://www.selah.k12.wa.us/SOAR/SciProj2002/KyleW.html . What he did was measure the time it took for different shapes to drop in a 4.267 meter PVC tube of water. All weight shapes had the same displacement of water. The result was really interesting. It turns out that sphere (ball) was the fastest shape. Almost double of cube shape. It was even slight faster than an egg shape.

Its widely know that a tear drop shape is the most arrow dynamic shape. But water is 800 times more denser than air, so it only makes sense that the best shape for hydrodynamicsis not the best shape for aerodynamics. I think the reason a sphere is the best is because it has the least surface area, reducing the surface drag.

So getting back to my question. I notice the AIDA rules say, lanyard “can be semi-elastic or non semi-elastic”. I plan on making my counter weight a ball out of melted tire irons. I have a tire shop saving them for me right now. If the speed of pulling a diver up is important, it just makes a more sense to make it in ball than using a cage of tire irons or other shape. If sphere is almost twice as fast as cube than the speed could be substantially more than a cage of diving weights. Also all the shapes started the 4-meter drop at a speed of zero. The speed in the last meter of the drop was probably more than double the speed of cube. Therefore the top speed of sphere could easily be 3 or more times the speed of cube

If the diver was in trouble some distance up from the bottom plate on the ascent, the speed at which the bottom plate would hit the carabineer might be pretty substantial. Do you think? In that case (I already have a had shoulder surgery!) wouldn’t some elastic in the lanyard be beneficial to help absorb the shock?

Thanks for your thoughts and experience,
don
 

Longfins

Well-Known Member
Oct 28, 2001
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Hi Don,

I wouldn't necessarily agree with Kyle W's conclusion. :) Although he was thorough in his data collection and observations, he neglected to tell us the frontal surface area of the shapes that he used. What he probably doesn't know is that drag is a function of drag coefficient (governed by shape) as well as surface area (smaller = less drag). He might have been curious as to why the small sphere sink time changed more than the small cube's sink time, which is also related to the diameter of the water column he used, which would contribute to the development of the terminal velocity (we don't know that either.)

I would agree that the sphere is a good shape up to a point. But there are other factors that contribute to the terminal velocity of the diver being rescued - diver's surface area, diver weight, comp line weight, counter weight, rope weight, drag from bottom plate, rope friction through the pulleys (and blocks), rope friction through water, change in diver buoyancy, and so on. If you're only concerned with weight drag right now, consider the submarine torpedo, which as you know has a small FRONTAL surface area as well as drag-reducing geometry. Small TOTAL surface area of a sphere alone won't do it.

Note: I have shoulder problems too, and hate the thought of it getting wrenched when the ascending line catch my lanyard. When I tested my counterbalance I chickened out and grabbed the line just before the lanyard caught so it would go easier on my shoulder! :) I've never tried an elastic lanyard.

Keep us updated on your counterbalance development. I'm very interested.

Peter S.
 

Octo

DancinLikeNo1isWatching
Apr 17, 2001
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Don,

If you are very concerned about wrenched shoulders, the best solution might be to use a waist lanyard.

Peter,

Beautiful rigging my man!
 

donmoore

New Member
Aug 19, 2002
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Thanks both Peters. Peter S., all those items I’m sure make a difference, but for right now I would like to focus on making the counter weight shape the most efficient. Seems like a pretty easy question for a person with the right science background. Know any submarine scientist?

I believe speed also has a lot to do with the best hydrodynamic shape. I know in boats that lengthening a boat that runs in at a displacement speed has very little effect on drag, but for a planning boat it can.

Other Peter,
The waist lanyard would definitely help the shoulder, but the idea with a wrist lanyard is that the head would tilt forward and want to close the mouth. The movement of water would be hitting the back of the head and thus not force water down the mouth. This is what Kirk Krack and Martin Stephanic said to me when I asked them about their counter balance system at a PFD course. If you were dragged up by the waist, I don’t know what would happen. If the mouth came open and the face was in the direction of movement, it could force water in the lungs and stomach and cause drowning.
don
 
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