Weights and Wings

[Capt EO]

Hi All,

First of all, you guys have a lot of information here to digest. Good reading and a good way to weigh info for making the decision of what route to take on a purchase.

I've been out of the water world the last 18 years and now making a come back since meeting and making friends with an avid diver. When put back in the water, all equipment still worked as should be. Thing is, is my old vest type B/C has been outgrown and a tad too small now. After reading the posts you have here, I think I will make the move to a BP/W set up. So thanks for all the info on that subject.

On another note, I do have a question as to how to determine the correct amount of weight one should use. Since it is starting to get chilly in the area and most of the diving we have been doing is in spring fed waters, I'm in a wetsuit (5m) and my body characteristics have changed over the years. I've checked out the "stickey" calculator and can see how it is useful for a number of configurations. I'd like to get a refresher and point in the right direction as to how to find that ideal "starting" weight to use and then making the adjustments as one adds or takes away from a configuration. This way I can refine what option I'd need to look at for the BP/W configuration as far as SS or aluminum plate extra weights, etc.....

Thanks in advance

 

[rstofer]

There are a couple of methods that don't involve the old "10% of body weight plus 5#" which applies to a 7mm suit. For a 5mm wetsuit, PADI recommends starting with "10% of body weight". They indicate that an aluminum 80 tank may require 4 or 5 pounds more and that a steel tank may require less. I have no idea what tank they used to arrive at the recommendations.

There is the method that Tobin of Deep Sea Supply recommends. With an empty BC and a FULL tank, adjust your weight such that you float eyeball level. This implies that you will need to swim down the first few feet and it also implies you will be positive by the weight of air you consume when you end the dive. However, the method also allows you to make your 15' stop with a nearly empty BC because your wetsuit has compressed. This method was mentioned in the context of a 7mm wetsuit and you may need to adjust the weight a little for the 15' stop. BTW, this method is shown in the PADI Peak Performance Buoyancy video.

The other method is to drain the tank down to 500# and try to get neutral with an empty wing while hovering at 15'. This implies you will be positive by the amount your wetsuit decompresses between 15' and the surface. In theory, you would have to swim down the first 15' if your tank is nearly empty but the weight of the air will help you submerge when the tank is full.

It is convenient to include 2ea 2# of clip-on 'hang' weights when you start out so if you need to remove a bit, just hand them to your buddy. It works the other way if you are light. They can hand you some hang weights.

Richard

 

[dkktsunami]

The best method to determine proper weighting is with 500 psi in the tank at 10 feet. Ideally you would want to carry only the necessary amount of weight to hold this position. This represents doing a safety stop at the end of a dive. Of course any time you change equipment or wet suits, or move from fresh to salt, this number will change. Once you determine the proper amount of weight write it down in your log book along with the equipment worn and note fresh or salt. Once the weighting is correct then approach the subject of proper trim, affected by the position of the weight. If all goes well you should be able to hold a horizontal position in 10' of water with 500 psi.

 

[Capt EO]

Thanks Guys.....just needed that spark to dig the info out of the memory banks....Safe Diving!

 

[fnfalman]

Remember that a diver cannot just think about lead weight only. The type of tank plays a major role in dive weight as well as other heavy/dead weight accessories (like a big cannister light or one of those massive 2lbs dive knives that some still favor). Every tank from every manufacturer has different buoyancy characteristics, so it would behoove you to know which tank you dive with and what the buoyancy characteristics are like for when full and when empty.

Your weight calculation formula should include lead weight + tank buoyancy + exposure suit buoyancy + BC buoyancy + dead weight accessories + tank valve (usually 2lbs on average) + regulator setup (also usually 2lbs on average).

 

[a.Meere.diver]

The best method to determine proper weighting is with 500 psi in the tank at 10 feet. Ideally you would want to carry only the necessary amount of weight to hold this position. This represents doing a safety stop at the end of a dive. Of course any time you change equipment or wet suits, or move from fresh to salt, this number will change. Once you determine the proper amount of weight write it down in your log book along with the equipment worn and note fresh or salt. Once the weighting is correct then approach the subject of proper trim, affected by the position of the weight. If all goes well you should be able to hold a horizontal position in 10' of water with 500 psi.

Could you expand on this a little. Is this holding the position with any amount of air in BCD necessary and breathing normally, or is it with empty bcd?

I think I like this better than the "float at eyelevel while holding breath" method

 

[Capt EO]

I'll keep the "extra Baggage" calculations in mind....everything needs to be accounted for! Had been pondering them while tinkering with Sticky's calculator.

Seems one needs to play around with any configuration one would find themselves in and log each.

Thanks again for the input.....

 

[donacheson]

I've been away from this board for a few years, but it's interesting to see that this topic is still being beat to death.

IMHO, a diver's goal should be to be be neutral at the end of a dive just below the surface with an empty BC, a near-empty tank, and breathing normally. In that way, the diver is under control throughout the entire dive.

How a diver can easily achieve this is another story.

 

[cool_hardware52]

On another note, I do have a question as to how to determine the correct amount of weight one should use. Since it is starting to get chilly in the area and most of the diving we have been doing is in spring fed waters, I'm in a wetsuit (5m) and my body characteristics have changed over the years. I've checked out the "stickey" calculator and can see how it is useful for a number of configurations. I'd like to get a refresher and point in the right direction as to how to find that ideal "starting" weight to use and then making the adjustments as one adds or takes away from a configuration. This way I can refine what option I'd need to look at for the BP/W configuration as far as SS or aluminum plate extra weights, etc.....

Thanks in advance

As a couple others have mentioned for divers using a single cylinder and a buoyant exposure suit I suggest:

Eye level at the surface with no gas in the BC and a full cylinder.

This method relies on the compression of the exposure suit from the surface to 15 ft. to offset the weight of the gas the diver consumes. A typical single cylinder will hold about 5-7 lbs of usable gas, and a wetsuit that's 20 lbs positive at the surface (1ata) will easily loose 5-7 lbs at 15 ft (~1.5ata)

One of the key benefits of this approach is the divers ballast can be adjusted at the surface, at the beginning of the dive when there is access to spare lead.

It's a starting point, one might need to adjust up or down a couple lbs. but it will get the diver pretty close.

Tobin