Question about “balanced rigs” and having all ballast unditchable

[lowviz]

...//... I can also go buy cheap tires and put them on a Ferrari and go 200 mph. They may or may not hold up, but if you get the correct rated tires for that speed then your percentage of survival just went way up. ...

Well that is kinda what this thread that you started has turned into. I see it as a reminder to the crusty ones and a wake up call to the fresh smiling faces.

"Trust but verify".

 

[johndiver999]

Then wear a drysuit.

Problem solved.

I don't disagree, but this is the Basic Forum.

I wonder what the ratio is between dry suits sold versus 7 mm wetsuits (for recreational divers). I would be surprised if the ratio is larger than 1:10. So saying that no 7 mm suits can be used below 40 or 50 feet might not be readily accepted.

Maybe the advice should be.. if you are daring enough to take a 7mm suit deep, you better have a handle on how much ditchable lead you should have?

 

[PfcAJ]

I don't disagree, but this is the Basic Forum.

I wonder what the ratio is between dry suits sold versus 7 mm wetsuits (for recreational divers). I would be surprised if the ratio is larger than 1:10. So saying that no 7 mm suits can be used below 40 or 50 feet might not be readily accepted.

Maybe the advice should be.. if you are daring enough to take a 7mm suit deep, you better have a handle on how much ditchable lead you should have?

The amount of people making a particular choice has no bearing on if it’s a poor choice or not.

A 7mm farmer John (that’s 14mm on most of the body) isn’t a great.

 

[boulderjohn]

The amount of people making a particular choice has no bearing on if it’s a poor choice or not.

A 7mm farmer John (that’s 14mm on most of the body) isn’t a great.

Because this post is in Basic, it is hard to respond in a way that is not more attuned to advanced diving.

Earlier on, there was a post about diving heavy steel doubles with a thick wetsuit and the problems involved. There was also a quote of an old GUE statement on a balanced rig, and that offered a comment on that--don't do it! If you are diving heavy steel doubles with a wetsuit and have a wing failure at depth, I am sorry, but you are in deep doodoo. You will not be swimming that puppy up, and I have a host of former tech students who have been required to try to swim up steel doubles without redundant buoyancy who will attest to that. It's a lesson everyone should keep in mind, whether you actually experience it or not. IN that case, you MUST have redundant buoyancy, and a drysuit provides that.

So let's try to keep things in basic for a while. If you are going to be diving thick wetsuits, especially farmer johns, you had better be prepared for the fact that you will have a significant problem with a loss of buoyancy at depth, and you need to be prepared for it. One way of preparing for it is to get a drysuit, and you will be shocked at how cheap they can be on the used gear market.

 

[northernone]

I
Maybe the advice should be.. if you are daring enough to take a 7mm suit deep, you better have a handle on how much ditchable lead you should have?

Exactly. Basic dive planning.

On a side topic not to derail the thread... It's difficult to catastrophically fail a 14mm wetsuit... In the same circumstances a drysuit could be fatal.

Looping back to the topic: it's likely less risky to teach proper weighting and quick detachable weighting systems as is introduced during the foundation of most dive training programs.

...We're not talking deco ceilings and overhead environments. The right equipment for maximizing the risk response possibilities for the dive conditions. A buoyant emergency ascent is better than drowned. So I keep the option open when there's no a cave ceiling above me.

Cameron

 

[Eric Sedletzky]

I don't disagree, but this is the Basic Forum.

I wonder what the ratio is between dry suits sold versus 7 mm wetsuits (for recreational divers). I would be surprised if the ratio is larger than 1:10. So saying that no 7 mm suits can be used below 40 or 50 feet might not be readily accepted.

Maybe the advice should be.. if you are daring enough to take a 7mm suit deep, you better have a handle on how much ditchable lead you should have?

It also depends on the type of 7mm wetsuit. A cheapo 7 mil will crush down to almost nothing at 100’ losing almost all it’s inherent buoyancy, and also causing you to freeze your ass, not good - that can cause cramps and make your legs next to worthless. Whereas a suit made from the famous Rubatex G231 (I own 3 of them), well that’s a different story.
Still, unless you know your equipment, the capabilities of your suit, keeping your NDL’s within a safe limit in case for some reason you must ditch weight at depth, staying in shape, and being properly weighted, I see no problem with going to 100’ or slightly deeper in a quality 7 mil wetsuit.
Remember, there was a time when there were no BC’s and divers routinely dived to depths way beyond that in wetsuits.
I’m actually surprised that a mention split fins vs freediving fins hasn’t made an appearance in this thread yet, with all the kicking like hell that would be going on!
...I guess it just did make it’s appearance

 

[ams511]

The way I was taught (and teach) the “balanced rig” concept is as follows:

Determine the minimum safe ballast required to be neutral at the safety stop with an empty-ish tank and zero air in the wing.

Distribute that weight as required for trim.

Ensure that you have some of that ballast ditchable equivalent to the weight of the gas at the start of the dive.

BCD failure at start of dive, ditch gas weight ballast and you will be neutral. This allows for a controlled ascent.

At the end of the dive? Leave the weight alone allowing for a controlled ascent.

If you have any issues at the surface ditch the weight and then gear if needed.

IF you are correctly weighted you should be positive at the surface equivalent to your suit compression. You should never end up significantly negative at the surface.

I may be missing something. Are assuming the diver is wearing a dry suit or a thin wetsuit? In cold water a diver in a 7 mil wetsuit can need 30 or more lbs of weight. An AL80 holds around 6 lbs of gas. On a dive to 60 feet or so, the suit will lose about 20 lbs of buoyancy If you have a problem, dropping 6 lbs may not be enough to make the rig light enough to kick up, let alone neutral. I know that is why many agencies recommend wearing nothing more than a 5 mil wetsuit and a dry suit for anything colder.

 

[ams511]

I’m actually surprised that a mention split fins vs freediving fins hasn’t made an appearance in this thread yet, with all the kicking like hell that would be going on!

That is because the powers that be banned Dan Volker. If he was here he would tell you that you that you could kick up an anvil if you use carbon fiber freediving fins.

 

[2airishuman]

Like @northernone I live and dive in an area where it is not uncommon for OWD students to use 7mm farmer johns on their open water checkout dives.

They are very much a "basic scuba" technology, and are in widespread use in this climate.

Drysuits pose their own buoyancy control problems, and cost aside, are not ideal for beginners. I stick to a wetsuit for a number of reasons, among them that I am difficult to fit and cannot expect to find an off-the-rack drysuit that fits well, let alone a used one.

 

[lowviz]

And the troll of the month award goes to @ams511!!!

Yeah, he would have something of substance to say. But, Hell, truth be known, I'm more of a VooDooGasMan kinda guy...