Another weighting question

[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!

 

[scubatoys]

You're doing it right... It is really not possible for anyone out here to tell you a whole lot, as there are such differences in wetsuits, body types, etc.

Just the fact that you are paying attention to the weight you are using, and working at your buoyancy is a great sign. As you get more comfortable, you will probably see you can take off a few pounds every now and then. Just keep at it and keep up the good work!

 

[boulderjohn]

Here is the problem with the 7 mm suit. You need a bunch of weight to get below the surface. As you descend, your wet suit compresses significantly. At depth, you don't need all that weight any more, and you end up adding a lot of air to your BCD to compensate for it.

When you start returning to the surface, your wet suit expands and all that air expands. If you aren't careful, you can get a runaway ascent.

 

[markfm]

One rule of thumb is that the weighting is about 2 lb per mm for a full suit. For a multi-X L, maybe it's more like 2.5 - 3lb.

So, changing from a 3 to a 7 is a 4 mm difference -- I'd expect anywhere from about 8 to 12 lb more lead, somewhere in the 26 - 30lb total lead range.

There's also fresh to salt delta. If the 3 mm was fresh, and the 7 mm is salt, for the same tank you would expect about a +7 lb lead change, based on your weight.

So, a 3mm fresh to a 7 mm salt might be a net of +15 - +19.

Perhaps some significant air pockets in the 7 mm, else unconscious body stiffness in the much thicker suit (poorer body form)? You're relatively new, and that's a good chunk of neoprene.

Good luck -- weight has a magic way of dropping over the early dives!

 

[DBailey]

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!

At the end of you dive, try to do some weight checks then. If you are able to stay in the water (i.e. shore dive and water stays in suit), and take off weight and check your buoyancy with an emptier tank, you'll be getting closer to your ideal weight. Plus you won't have the anxiety of not being able to descend and delaying the dive.

 

[scubadmike]

HI my name is Mike [scubadmike] When you have an ex.-suit on this is a very big factor!! Also salt water & fresh water is also a big factor.. Keep track in your log book..Time of year/salt water/fresh water/How your drest...Sounds like you started in the right track...YOU GOT TO EXPERMENT!!!Every body chemestory is dirfrent!!

 

[spectrum]

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

 

[Garrobo]

The answer is to never dive in cold water. Go south and use a one or two millimeter shorty and you could probably get down to less than 10 pounds of lead. Anyway that has been my experience.

 

[amajamar]

One rule of thumb is that the weighting is about 2 lb per mm for a full suit. For a multi-X L, maybe it's more like 2.5 - 3lb.

So, changing from a 3 to a 7 is a 4 mm difference -- I'd expect anywhere from about 8 to 12 lb more lead, somewhere in the 26 - 30lb total lead range.

There's also fresh to salt delta. If the 3 mm was fresh, and the 7 mm is salt, for the same tank you would expect about a +7 lb lead change, based on your weight.

So, a 3mm fresh to a 7 mm salt might be a net of +15 - +19.

Perhaps some significant air pockets in the 7 mm, else unconscious body stiffness in the much thicker suit (poorer body form)? You're relatively new, and that's a good chunk of neoprene.

Good luck -- weight has a magic way of dropping over the early dives!

What is the delta between salt and fresh wearing a 7MM wetsuit?

 

[spectrum]

What is the delta between salt and fresh wearing a 7MM wetsuit?

Regardless of the gear in question but when wearing the same gear for fresh water or salt you take the total dry diver pre-dive weight (you all of your gear, weights and a full air cylinder) and divide by 40. This is what you add for salt or remove for fresh dependinf where you baseline is. This is based on the typcal salt water specific gravity of 1.026. For most divers this is 6-8 pounds.

Pete