webbah:
Hi all - I know there are various threads on this topic as I read through most of them. But I still want to ask about my specifics. I'm fairly new to diving with only 22 logged dives - most of those in warm water. I'm 5'9" and 232 lbs. My last warm water dives in a 3mil suit I used 18 pounds which seemed to be about right. But then I went in cold water this past weekend with my new 7mil suit and booties and thick gloves on an AL80 with 38 pounds and felt like I had trouble getting under but then was scraping the bottom at 50 feet. I didn't feel comfortable at all.
Is it all about gradually attempting to drop some weight with the main focus on relaxing while I try and get below the surface? I'm afraid to get all geared up with two or more less pounds and not be able to drop.
Tips? Suggestions?
Thanks in advance!
Wearing more weight with a heavier suit is to be expected but you know that.
Scraping bottom at 50 feet in a heavier suit is to be expected if you do not add air to you BC. Any suit will loose buoyancy as it crushes with the pressure of depth. To compensate for this you have a Buoyancy Compensator and adding air to it is not a sin, in fact with a suit and depth of any significance it is a necessity. I assume air in the BC would have gotten you off the bottom since nearly any BC has the lift to deal with that configuration. Unless you have the lungs of a big gorilla you will not do all of the compensation with lung volume management.
Here is my suggested weight check:
Remember to set your weight so that you bob vertically at eye level at the end of your dive with an empty BC, an average breath, your feet still (crossed) and about 500 PSI in your cylinder. A deep breath should get your mask out of the water and a deep exhale should sink your mask. Do all of this while breathing from your regulator. The end of the dive is the defining moment for your weight requirement and you want just enough to let you stay down in the shallows with a light cylinder.
The short cut to getting started is to do this when getting in the water and add 5 pounds for the weight of the air you will be lacking at the end of the dive. The saturation of your gear, relaxation and a host of variables can skew this so be sure to repeat it at the end.
Once you get this right have a 2 pounder that is clipped or in a pocket. At the end of a dive with a near empty tank and while in the shallows remove the 2 pounds, If you begin to feel unstable and prone to surfacing against your will then you know that you need that 2 pounder If you cut it to the bone you may find that you have a hard time staying down in surge so don't get carried away. Also be mindful of any accessories such as light that you may or may not carry on each dive, they too are part of the buoyancy and trim equations.
Carrying an extra 2-4 pounds of weight above the absolute bare minimum will not be a meaningful bother once you get the hang of buoyancy control in the first place. Being grossly overweighted will make you unstable and is dangerous. Being slightly over weight is much safer than being slightly under weighted.
Regarding you, your suit and your gear no numerical answer of value can be given here.
As a reference my delta between a 3mm full suit and a 7mm with 2X on the core is about 20 pounds
Pete