Weight

[Phil_C]

....in the general case, if one can not descent legs first, he/she is not properly weighted. May be you guys should ask yourselfs why you are descending head first, because you like it that way, or because you cannot do it otherwise.

Cheers

You will open a can of worms with this comment - actually good form is to descend AND ascend in horizontal trim and there are all sorts of good reasons why you should aim to do this. My first dive of the day I might have the buoyancy issue until the neoprene gets saturated, after that everything is horizontal - down and up. From a DCI point of view medical evidence shows that horizontal trim is better than vertical for ascents, and there is a lot of anecdotal evidence that says horizontal trim throughout is best.

Once my wetsuit is fully flooded and wet I can go down or up in any orientation I want with ease.

In my drysuit it is always down and up in horizontal trim to set the bubble up from the start. - Phil

 

[NoviceDiver1]

You will open a can of worms with this comment - actually good form is to descend AND ascend in horizontal trim and there are all sorts of good reasons why you should aim to do this. My first dive of the day I might have the buoyancy issue until the neoprene gets saturated, after that everything is horizontal - down and up. From a DCI point of view medical evidence shows that horizontal trim is better than vertical for ascents, and there is a lot of anecdotal evidence that says horizontal trim throughout is best.

Once my wetsuit is fully flooded and wet I can go down or up in any orientation I want with ease.

In my drysuit it is always down and up in horizontal trim to set the bubble up from the start. - Phil

You are right here Phil, absolutely right. I take it back.

 

[chillyinCanada]

Novice diver1, I do it that way because I prefer it. I can do it the other way but choose not to for the most part. I do most of my dives with little to no air in my bc. At around 30', I make sure to dump any little bit that may have been added throughout the dive. Then I ascend to my stop horizontally. Hold my stop and then very slowly ascend to the surface, again horizontally.

 

[Rich Keller]

I use a regular AL 80. I think I have this issue because the difference the suit makes when expanded and compressed may be quite significant.
In most cases this is a minor inconvenience indeed, but in some cases it matters. If the waves are 4-6, then it causes significant exertion, which increases heart rate and air consumption not only during the descent, but throughout the dive. In addition, I lose sight of my buddy, which is my wife, and I really do not like that, especially if the viz is low.

The issue is defiantly suit compression. I have never dove a 12mm suit so I can not exactly address this from personal experience. You also did not mention how much weight you used in the past to overcome the buoyancy problem above 10' so it is hard to come up with exact numbers for you. The difference between a full tank and a tank at 500psi is 5.8lbs to 5.86lbs depending on the tank manufacturer. Do you think that you are making up that gain with the difference between the suit compression at 10' vs 15' assuming that is the depth of your safety stop? Are you using a foam or crushed neoprene suit? There are a few outside the box solutions that might work for you, again being dependent on how much more weight you need. First, if your wife is negative at the start of the dive, go down holding her hand so you are reducing your effort and not losing sight of her. Second, if you are dropping a weighted line to your 15' stop you could ride that down or go hand over hand down the anchor line instead of swimming. Third, you could go down with something like a sand bag and just dump it once you get below the 10' mark. Another thing you might want to consider is that if a hard 10' swim at the start of your dive is effecting the rest of your dive there may be a health issue involved here as well.

---------- Post added December 8th, 2013 at 01:24 PM ----------

As for swimming down head first, that is just something I have always done. When I started diving BCDs had not been invented yet so there was no hovering involved in diving at that time. We also did not have dive computers so using the tables meant that the amount of time it took to descend was counted as time spent at the deepest part of the dive so we did not spend too much time descending.

 

[NoviceDiver1]

The issue is defiantly suit compression. I have never dove a 12mm suit so I can not exactly address this from personal experience. You also did not mention how much weight you used in the past to overcome the buoyancy problem above 10' so it is hard to come up with exact numbers for you. The difference between a full tank and a tank at 500psi is 5.8lbs to 5.86lbs depending on the tank manufacturer. Do you think that you are making up that gain with the difference between the suit compression at 10' vs 15' assuming that is the depth of your safety stop? Are you using a foam or crushed neoprene suit? There are a few outside the box solutions that might work for you, again being dependent on how much more weight you need. First, if your wife is negative at the start of the dive, go down holding her hand so you are reducing your effort and not losing sight of her. Second, if you are dropping a weighted line to your 15' stop you could ride that down or go hand over hand down the anchor line instead of swimming. Third, you could go down with something like a sand bag and just dump it once you get below the 10' mark. Another thing you might want to consider is that if a hard 10' swim at the start of your dive is effecting the rest of your dive there may be a health issue involved here as well.

Hi richkeller,
"Do you think that you are making up that gain with the difference between the suit compression at 10' vs 15' assuming that is the depth of your safety stop?"--you lost me here I admit it

"Are you using a foam or crushed neoprene suit?"--I have no idea

My wife has the same issue, so holding on to her is not an option, not to mention that her fins are positively buoyant...

We rarely use lines, if there is one then the solution is pretty self-evident.

This thing with the sandbag is actually a great idea, definitely worth trying, thanks a lot.

My resting heart rate is in the low 40s. I try to maintain it at a similar level throughout a dive so that I prolong the duration of the dive. Any sort of exertion makes my dive shorter, so I want to avoid exertion period.

---------- Post added December 8th, 2013 at 01:34 PM ----------

Yeaah...a man of knowledge and experience detected. Cheers and thanks a lot for the input!

 

[Rich Keller]

The thing I am having a problem understanding is how you can be so buoyant at the start with a full tank but yet have no problem holding a 15' stop with a near empty tank at the end of the dive. The difference in tank weight between full and 500psi is almost 6lbs. If you are so buoyant at the beginning and at the end you are almost 6lbs more buoyant I would think holding a stop at 15' would be a problem. Again I have no experience diving 12mm suits but I do not see how the additional suit compression of another 5' can make up for this much buoyancy. As for your heart rate you could try a three-four count breathing method to lower that. Take in a full breath over a period of four seconds, hold it for four seconds and let it out over a period of four seconds. This will not save on air directly but it will reduce your heart rate and once it is back down where you want it you will save some air during the rest of your dive.

 

[NoviceDiver1]

The thing I am having a problem understanding is how you can be so buoyant at the start with a full tank but yet have no problem holding a 15' stop with a near empty tank at the end of the dive. The difference in tank weight between full and 500psi is almost 6lbs. If you are so buoyant at the beginning and at the end you are almost 6lbs more buoyant I would think holding a stop at 15' would be a problem. Again I have no experience diving 12mm suits but I do not see how the additional suit compression of another 5' can make up for this much buoyancy. As for your heart rate you could try a three-four count breathing method to lower that. Take in a full breath over a period of four seconds, hold it for four seconds and let it out over a period of four seconds. This will not save on air directly but it will reduce your heart rate and once it is back down where you want it you will save some air during the rest of your dive.

aha..I think I got it.

What I think matters is not the 5' difference, rather the depth of the dive and the duration of the dive. 15' suit buoyancy will be greater at the beginning of a dive than at the end of a dive. The greater the depth and the duration of a dive, the greater the difference. For an average dive of around 50 min at 80', this difference will be quite large. If the decrease in suit buoyancy is equal or greater than the increase in tank buoyancy, than the outcome is no change or a net decrease in buoyancy,resulting in a relatively comfortable safety stop, for me usually around 17'.. I hope I am making sense out of this..

I have been doing something similar in terms of breathing, it helps in deed.Thanks a lot.

 

[Rich Keller]

Yes the suit at 15' on your way down will be a little more buoyant then it would at 15' on your way up after a dive but I still do not see how that can make up for the additional 6lbs of buoyancy you are getting from a near empty tank. How much additional weight did you use to overcome the excess buoyancy above 10'?

 

[NoviceDiver1]

I did not use any additional weight.. I went down head first.

---------- Post added December 8th, 2013 at 02:48 PM ----------

btw do you think it will make any difference if I partially fill up the bc with water on the surface and empty it when a comfortable depth is reached?

I did increase the weight by two pounds for one of the dives, but I think it was more than obvious that I was too heavy once we passed 10-15 feet. In addition, I do not think it made a significant difference over the first 10 feet. I still had to descent head first.

 

[Phil_C]

btw do you think it will make any difference if I partially fill up the bc with water on the surface and empty it when a comfortable depth is reached?
.

Yes - you could well end up killing yourself !

The BCD is designed to have air in it for buoyancy or be empty and provide no lift - you put water in it and it will have no difference in weight with the water around it so it will not help you descend - but you MAY NOT be able to empty it under water, leaving you with a BCD that cannot carry out it's primary purpose.

When you start to put air in it the weight of the water may be too great for the air to push the water out through the bottom dump valve - the air may go out through the upper dump valve due to the overpressure valve opening first. This means you will put air in, and it will come out through the over pressure valve without pushing the water out and filling with air.

This could mean that you do not have enough buoyancy to get neutral of bring you to the surface if you need it. - Certainly very bad practice and possibly fatal if things go wrong. = Phil

---------- Post added December 8th, 2013 at 10:42 PM ----------

Thinking more on your last comments - much as you can learn a lot from an internet forum there are some things which are best learnt from practice with either a mentor or an instructor/dm one on one. You are diving a very heavy wetsuit combination, which gives you significant issues around buoyancy, especially in shallow water where the greatest change in pressure takes place (from 0-30 foot a doubling of pressure).

This means that in shallow water (0-30 foot) you will experience greater buoyancy swings with your chosen suit than say between 30-60 foot or deeper. For this reason the best advice that can be given is to do a proper buoyancy and weight check with a near empty tank at 15 foot. If this means you have to do a dive just to work on this, then so be it. If you are not sure how to do this for your combination try to find someone (DM/Instructor) to show you - long term it will make your dives more comfortable and safer.

All the solutions about 'breaking' the surface at the start of a dive are fine and safe - but ONLY if you have your buoyancy neutral for your safety stop at 15 foot with a nearly empty tank at the end of a dive.

Anything else weight wise will only be a guess and can be wildly wrong and even dangerous - Dive safe - Phil

Go back to the basics - do a proper weight check for your suit combination, then work on techniques to get you down when you first get in. Otherwise I see a real risk of a runaway ascent of other problems because you have too little or too much weight. - Phil