Dialing in wetsuit buoyancy at aquatic park (SF)?

[Chuck Tribolet]

Unless you can stand up in the water, I certainly wouldn't put on a wetsuit with 25# of weight and then submerge to eyeball level.

One school of thought is to have a full tank, all your gear and then set your buoyancy to float eyeball high with an empty BC and moderate breath. The idea is that your wetsuit will lose enough buoyance at 15' to overcome the gain in buoyancy from a empty tank. To submerge, you kind of kick up and bounce down.

Richard

I gotta say "baloney" to your first paragraph. When I was a wet
suit diver, I had WAY more than 25 pounds to sink the suit. 34
pounds IIRC to sink three 7 mm layers (hooded vest, farmer john,
beaver-tail jacket). Most divers can kick up or down 10-12 pounds.
I've gone to the bottom in the tropics to recover the 10ish pound
weight belt the boat driver dropped. Oh, and now that I think
about it, my 2 pound negative camera was already on board, so
12 pounds.

Would it be a good idea to do your first dive in a new wetsuit off
a boat in 120'? NO!

On your second paragraph:

1. You assume that you never want to be neutral above 15'.
2. The proper way to submerge is that, you do a dolphin dive, go completely vertical,
let the weight of your legs drive you down, and kick like hell.

Finally: Something that's really important for small boat diving
where you take your tank off before getting on the boat is that
the tank+BC be negative (so you are positive) at the end of the
dive. An AL80 and no weight on the BC will be positive (so you
are negative) at the end of the dive. You don't need to have
ALL your weight on the BC, but about 8 pounds negative is cool.

 

[dannobee]

I'm with Chuck on this one. When I was diving wet (7mm) with an AL80, I used 30 lbs of lead.

25 lbs probably isn't too far off for a smaller person. Take more as it's likely that you'll need more.

Since you have to start somewhere, the PADI baseline is 10% of your body weight plus 5 lbs (assuming AL80 tank and BC, not backplate/wing).

I'd probably be more inclined to dive Ocean Beach than Aquatic Park, but that's just me.


.

 

[supersand]

Hey maybe you experienced divers can give me a guesstimate:

In hawaii diving with a 5mm shorty with sleeves, Al80 tank, and a BC I was using 24lbs. I only got in 8 dives including the 4 open water checkout dives and the weight seemed to work well definitely not underweighted even at 500psi. Perhaps I might have even been able to shed a couple pounds.


I'm 6'4" and weigh about 280lbs (lots of built in insulation for cold water diving) and in Monterey I'll be using a hooded 7mm wetsuit (no vest, I'll see how cold it is) plus booties and gloves and I'll be using an Al80 rental tank. Good thing is that I have a ss backplate/wing with extra plates that weighs in at 16lbs. Im thinking around 20lbs on the belt with a composite weight total of 36lbs.

Do you guys think its in the ballpark?
Perhaps I'll head on down to the dive shop anyways. Doesn't that chlorine devour wetsuits though?

 

[astrofunk]

Doesn't that chlorine devour wetsuits though?

Put your wetsuit on and then rinse yourself thoroughly in the shower before jumping in. Then rinse again afterward. Your suit'll survive.

 

[rstofer]

I gotta say "baloney" to your first paragraph. When I was a wet
suit diver, I had WAY more than 25 pounds to sink the suit. 34
pounds IIRC to sink three 7 mm layers (hooded vest, farmer john,
beaver-tail jacket). Most divers can kick up or down 10-12 pounds.
I've gone to the bottom in the tropics to recover the 10ish pound
weight belt the boat driver dropped. Oh, and now that I think
about it, my 2 pound negative camera was already on board, so
12 pounds.

I have a 7/8mm semi-dry wetsuit and I use 20# of weight with a 6# plate and HP 100. I am at least 4# overweight by any metric because I sink like a stone. I am planning to drop back to 16# the next time out. But I do think that 1 piece wetsuits are somewhat less buoyant than Farmer John's.

That would leave me with 33# of ballast at the start of the dive and 24# with an empty tank.

On your second paragraph:

1. You assume that you never want to be neutral above 15'.
2. The proper way to submerge is that, you do a dolphin dive, go completely vertical,
let the weight of your legs drive you down, and kick like hell.

Unless I am mistaken, the method I proposed is exactly what Tobin at Deep Sea Supply recommends. Check it out on the BCs forum. Eyeball level with a full tank and empty wing at the start of the dive. It certainly seems to assume that there is no need to be neutral above 15' with an empty tank but perhaps tanks are never really empty and wetsuits don't decompress quickly.

The kick-vertical and drop down (do not invert) is also his recommendation. We discussed this and he mentioned that inverting is a poor idea in a kelp forest and that it was less likely to result in entanglement if I dropped straight down. Sounds good to me!

Somehow, I can't imagine Tobin making recommendations that don't work. I have a little more tuning to do to get down to the weight he recommends.

Richard

 

[rstofer]

Finally: Something that's really important for small boat diving
where you take your tank off before getting on the boat is that
the tank+BC be negative (so you are positive) at the end of the
dive. An AL80 and no weight on the BC will be positive (so you
are negative) at the end of the dive. You don't need to have
ALL your weight on the BC, but about 8 pounds negative is cool.

Another way to put this: Your BC (whatever) with a full tank and any integrated weights should be buoyant with the bladder fully inflated without support from the diver. You should be buoyant (at least with your head above water) without the BC but wearing your weight belt or harness. None of this includes accessories such as lights and cameras.

There is a problem when you get geared up in the water and use a weight harness. It goes on FIRST! So, you are wearing all of your ballast and none of your flotation at some point during the process. Being negative could be life threatening.

In the old days when I could actually wear a weight belt, I didn't deal with this correctly. I wore a 30# belt to sink a jacket style, non-weight integrated BC and an Al 80. There was no chance I could float on the surface without the BC. This was a mistake! A warm water diver's approach to Monterey.

Obviously, if you could put 20# of lead on a BP/W with a 10.5# tank, 6# plate and a 2# regulator, a 30# lift wing would be totally inadequate for floating the BP/W. So, don't put all of the weight on the BP/W even if you could. Besides, ditchable weight is a good thing.

With a 7 mm wetsuit, it is unlikely you will become neutral or negative with 15# of ballast (but CHECK). So, put the 15# on your hips (or in a separate weight harness) and then you can carry the other 5# (or whatever, maybe nothing) on your BP/W.

The BP/W with a full HP100 is about as much as I care to lift due to old age and a bad back. I prefer to carry most of my ballast in a weight harness.

Richard

 

[John_B]

Provided you have 3 significant digits

Measure with a micrometer, mark with chalk, cut with an axe!

 

[mikemill]

My axe:

 

[rstofer]

Of course it's made in Arizona! What a terrific state for gun owners.

Richard

 

[Eric Sedletzky]

Hey maybe you experienced divers can give me a guesstimate:

In hawaii diving with a 5mm shorty with sleeves, Al80 tank, and a BC I was using 24lbs. I only got in 8 dives including the 4 open water checkout dives and the weight seemed to work well definitely not underweighted even at 500psi. Perhaps I might have even been able to shed a couple pounds.


I'm 6'4" and weigh about 280lbs (lots of built in insulation for cold water diving) and in Monterey I'll be using a hooded 7mm wetsuit (no vest, I'll see how cold it is) plus booties and gloves and I'll be using an Al80 rental tank. Good thing is that I have a ss backplate/wing with extra plates that weighs in at 16lbs. Im thinking around 20lbs on the belt with a composite weight total of 36lbs.

Do you guys think its in the ballpark?
Perhaps I'll head on down to the dive shop anyways. Doesn't that chlorine devour wetsuits though?

Reading all this up to this point, I would say what you described above would be a good starting point. I would just go in at breakwater on a calm day and see if you sink when you let all the air out of your BC. If you do then I would lighten it up a bit. You want to float a bit at the beginning of the dive with a full tank. The final way to tell if you are perfectly weighted is at the end of the dive if you can hold a stop at 15 feet with all the air let out of your BC and keep a perfect stop with your breath control alone, then you know you got it.