How much weight?

[sockeye02]

How much weight would you use? PADI teaches floating at eye level on the surface with lungs fully exhaled and BCD deflated, but I find if I did that firstly I'd have great trouble descending, and secondly I'd also have great trouble staying at 5m for my safety stop. The last time I tried it I had to swim inverted frantically in order to keep my safety stop.
For background, I dive tropical waters in a 3mm long wetsuit and usually use AL80 rental tanks.
Thanks for advice!

 

[DevonDiver]

There are some great posts/threads already on the board that cover this, so it is worth spending 10 minutes with the search function to find them.

The problem with conducting a weight check at the beginning of the dive is that it does not allow for the increasingly positive bouyancy of youyr cylinder as you consume the air during the dive. This means that even with a perfect weight check at the start, you can become too bouyant at the end of the dive.

To counter this, you can either approximately 'guestimate' an extra amount of weight to add to your belt to achieve correct bouyancy at the end of the dive...or... you can conduct the bouyancy check at the end of the dive and get your weighting spot on.

Quite often, new divers will conduct a buoyancy check - achieve the correct weighting - and yet still have a problem descending. This is often caused by one or more of several common problems:

1. Inadvertant finning, creating upward thrust, preventing descent (crpss your legs if you have to).
2. Deep breathing, causing increased buoyancy on descent (remember to exhale fully as your begin your descent).
3. Failure to completely empty air from the BCD. Remember to hold the deflate valve at the highest possible point above your head. Allow some extra time for air to work its way out.

There are also a couple of other methods that you can use to check your weighting....

1. Be consious of how much air you need to add to your BCD once you finish your descent and obtain neutal bouyancy. Anything more than a couple of quick 'squirts' and you are just adding air to compensate for being overweighted.

2. Try and hold neutral bouyancy with your tank on the minimum reserve pressure (50bar/500psi). Remember not to fin or scull with your hands. Keep your breathing steady and relaxed. Add or subtract weight, until you can hold a motionless stop with the minimum air reserve.

 

[sockeye02]

Thanks for the quick tips!
I did search but what I took back was basically that being properly weighted at the start of the dive according to the PADI suggestion would result in me being neutrally weighted at 5m (safety stop) at the end of the dive with 500psi, something I did not experience in real life hence thought I'd ask for additional advice

 

[DA Aquamaster]

Right, the PADI suggested technique works really well - if done at the end of the dive with about 500psi in the tank. If you do it with a full tank, you will have about 4 lbs of weight in the gas in the tank, that you will not have at the end of the dive.

If you float at eyeball level with full lungs, you will sink when you exhale and, with a neoprene exposure suit, you will be very close to neutral with mid to full lung volume at 15 ft.

 

[stairman]

Lots of things effect weighting even when you think you have it down. Fresh/ salt water, different wet suits etc. Many dont take the time to hold a safety stop at 15ft. with 500 to 700 psi and try to compensate with an extra 5 lbs. Being able to hang at 15 with 500 is more important than being slightly overweighted but the more you dive the better this understanding becomes. Writing your findings in your log book sure helps with different scenarios you encounter.

 

[TheScubaBOB]

PADI teaches us to use too much weight.

I started using 30lbs in a cold fresh water quarry with a 7mm wetsuit.

When in the Philippines, I used 30lbs in the warm salt water of Subic Bay.

I thought I was properly weighted.

Then I did the Peak Performance Buoyancy Specialty and instantly dropped to 14lbs in cold fresh water with a 7mm wetsuit.

The first 5 feet required a little effort.

Then I switched from Aluminum to Steel Tanks. With my LP PST 120 Tanks I used 8lbs (9 if I have my AL30 pony bottle).

What really fixed my "beginning the descent" issues was learning to parachute fall down into the water column.

Basically dump all air, lean forward (in parachute position) and exhale. I just begin to slowly drift down.

I've also found it helpful to "flush" my wetsuit with water a few times right after I get in. To do this just open your neck seal and let water in then with a little movement help it work it's way through your wetsuit. This reduces trapped air in your wetsuit.

For the record, I'm 6'2" tall and weight about 235lbs (yeah a little generous around the middle).

 

[MauiScubaSteve]

PADI does not teach!

Instructors teach!

There are plenty of PADI instructors who do not teach their students to use too much weight.

Many new divers do all three of the things mentioned in Devon's post; upward fin thrust, too large a breath without exhaling fully and failure to release enough/all the air out of the BC.

For new divers who learn horizontal fin thrust, proper breath control and BC air release slowly, a couple extra pounds helps them.

The key is to use enough weight to stay down at the SS. With experience most divers use less weight. Good instruction quickens the learning curve.

 

[TheScubaBOB]

PADI does not teach!
Instructors teach!

The weighting guidelines that got me to 30 lbs are in the PADI Manuals, therefore PADI as an Agency that Certified Divers endorses my diving with 30lbs of lead.

PADI expects it's certified Instructors to teach the standards they endorse, ergo the PADI {Standards} teach us to dive heavy.

True some instructors don't use the PADI stanrards for weighting. In fact my 17 year old daughter only needed 24lbs on OW 3 & 4 because I put her in a brand new wetsuit (the instructor was very keen to not use even a single pound extra). Before that she was using 18lbs. Now since I have reduced her weight to 14lbs.

 

[rstofer]

If you are diving Singapore with more than about 6# of weight, you are probably overweighted.

We're talking T-shirt diving so no wetsuit. The body is essentially neutral so all you need to compensate for is the 4# of positive buoyancy of an Al 80 when it is empty. 6# is more than enough. Actually, I wore a Lycra dive skin.

Yes, I used to dive Singapore, Malaysia, Thailand and the Maldives and I never wore more than 6#. That was enough to keep me planted to the bottom for photography. And I'm 6'1" and was over 200# even back then.

You can set your initial buoyancy as eyeball level with an empty BC and full tank if you wish. There are those that recommend it because you will lose buoyancy at 15' due to wetsuit compression. But this is usually discussed in the context of a 7mm wetsuit which loses a LOT of buoyancy

Still, you know that the Al 80 holds 6# of air so if you set your buoyancy at eyeball with a full tank, just add 6# to whatever you are wearing. Later on when you know how much your wetsuit compresses, you can probably remove a couple of pounds and still hold a stop.

Cross your ankles while you are adding weights to prevent finning.

I love Singapore! The best of times...

Richard

 

[k374]

It is my opinion that the PADI course does not sufficiently cover controlled ascents and descents or equalization. It's just in there like an afterthought.