I f*** up and I am ashamed

[Raphus]

I linked the SSI DM page some posts ago. It seems the course can be done in one week, not many dives required.

I know, I always read all posts before I write my own.
I meant, that it should not be done. It is possible. Especially, because he already had science of diving. But I is a bad idea.

 

[100days-a-year]

Every time I see the word " master " and " diving " together and see the qualifications I kind of grimace a bit, shake my head and sigh. Pretty much every other human endeavor the word " master " generally has a connotation of years of hard work and skill development and then a post like this comes along and scuba is once again a laughingstock.
The OP obviously is pretty clueless and the guide should be barred from work for at least long enough to reconsider their part in this fiasco. But the certifying agency bears a bit of culpability for succumbing to the business of stroking egos by erroneously conferring the title " master " on people who at best are neophytes and in this case and many other are a danger to themselves and others.

 

[Dody]

Every time I see the word " master " and " diving " together and see the qualifications I kind of grimace a bit, shake my head and sigh. Pretty much every other human endeavor the word " master " generally has a connotation of years of hard work and skill development and then a post like this comes along and scuba is once again a laughingstock.
The OP obviously is pretty clueless and the guide should be barred from work for at least long enough to reconsider their part in this fiasco. But the certifying agency bears a bit of culpability for succumbing to the business of stroking egos by erroneously conferring the title " master " on people who at best are neophytes and in this case and many other are a danger to themselves and others.

I think this talks about you

 

[Blackcrusader]

I think this talks about you

Except this thread is about you Dody. I understand you are very keen to get certifications. Personally I think you need more dives in different conditions before you went for your DM cert. Seems a bit rushed to me your training and even with that training you make very basic errors. Anyway you learn from your mistakes hopefully. I believe I was fortunate to have been in a BSAC club where 2 hour classes twice a week plus regular re-training / reviews of things you have learnt before were taught.

Maybe you should get into a club where you can dive regularly with more experienced divers. Try doing some night dives, they are easy and fun to do. You wrote you haven't done night dives yet? If you want to go diving and show a DM cert then operators expect that you know what you are doing, they expect you know when not to do an activity on a dive. Bring a dive torch on every dive as it can be used to signal people 10m away from you. Learn how to use the torch for different signals. This sort of thing a DM certified diver should know. Anyway enjoy your diving as I am doing very few dives this year.

 

[Steelyeyes]

I think the push for underweighting is to reduce bubble size in the BCD and thereby reduce drag. That's all fine and good but there is another way to reduce drag, swim slower. Drag is a cubed function of velocity in the water. It basically follows the third pump law. An example is that to double the speed of a fully submerged object it takes eight times the force. That means the slower you swim the less drag you have and you save a ton of energy, which translates to less air (gas) consumed and generally longer bottom times.

Everyone dives for different reasons but if you're there to see as much underwater life as possible slowing down pays off. Critters are less skittish, smaller things can be seen that are equally as intriguing as large things...although not as awesome as the manta my neighbor saw while teaching an advanced open water course at Bari's Reef yesterday.

 

[OrcasC205]

I think the push for underweighting is to reduce bubble size in the BCD and thereby reduce drag. That's all fine and good but there is another way to reduce drag, swim slower. Drag is a cubed function of velocity in the water. It basically follows the third pump law. An example is that to double the speed of a fully submerged object it takes eight times the force. That means the slower you swim the less drag you have and you save a ton of energy, which translates to less air (gas) consumed and generally longer bottom times.

No, the primary reason for reducing the bubble size in the BCD (and drysuit if you are diving dry) is that the more gas you are carrying in the BCD, the more variations in buoyancy there is with changes in depth. A large bubble provides more gas to compress or decompress with depth changes, making it much more difficult to control your buoyancy. It's much easier to avoid uncontrolled ascents if you are properly weighted.

The reduced drag is an added benefit, but as you mention there are a lot of other ways to reduce drag including proper trim and slowing down.

 

[boulderjohn]

I think the push for underweighting is to reduce bubble size in the BCD and thereby reduce drag.

No, the primary reason for reducing the bubble size in the BCD (and drysuit if you are diving dry) is that the more gas you are carrying in the BCD, the more variations in buoyancy there is with changes in depth.

OrcasC205 is correct about this. The closer you are to ideal weight, the easier it is to control buoyancy because the primary factor in that control is your breathing. The more air in the BCD, the more that air expansion and contraction in the BCD takes control.

In teaching OW classes, I was about 6 pounds over ideal so I could descend faster or control a student better. With that much extra weight, I could still do a demonstration in which I went from the bottom of the deep end (12 feet) to the surface and back down, with multiple stops along the way, just by controlling the amount of air I inhaled or exhaled. In the same pool while wearing double steel tanks while practicing tech diving, I could only control depth by my breathing for a few feet because the extra air required for that extra weight expanded or contracted more than my chest area could overcome.

That said, I also prefer to be a few pounds heavy.

 

[grf88]

I like to carry several extra pounds and I also dive slow, real slow, and I warn potential buddies of that. Multiple times I have had buddies tell me they were surprised how much more they saw during the dive. I never worry about drag unless working against a strong current but I also avoid that as well.

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[BlueTrin]

I don't know how a diver with that much experience lost buoyancy control on that dive, because when he told me about it, he did not know, either. The key is that it happened to an extremely experienced diver--they are not immune.

One small possible factor may have been his tendency to resist learning information that conflicts with his previous beliefs. He had been told emphatically by people he admired that altitude did not have to be considered on dives. On a dive we did together at about 11,000 feet/3,300 meter elevation, I talked about problems we had with buoyancy in shallow water, and I talked about the significant difference between buoyancy at that elevation and buoyancy at sea level, and he dismissed my statement, saying there was no real difference, despite the simple math of Boyle's Law. The dive on which he was paralyzed was at a significantly higher elevation than our previous experience together, and when we talked about it, I asked him if he knew the difference at that elevation according to Boyle's Law. He had not given it a thought. At sea level, a bubble of air at the depth where he had his trouble will increase 4 times when it gets to the surface; at the elevation he was diving, it will increase 7 times. I think that is significant, even though the difference at depth is not as great as that. Because his mindset was that altitude is not a factor, he had failed to take that into account.

After reading you I checked how many atm at 3300.

I was shocked to learned that it was only 0.67.

So you are saying diving at sea, 30m deep, we are at 4atm, so air will expand 4 times going to the surface.

But at 30m deep at 3300m, we are at 3.67atm and go to 0.67. So it will expand 3.67/0.67 so that’s a 5.5x expansion.

You said 7 times: where did I go wrong?

I have never considered altitude because I never dived at altitude …

 

[boulderjohn]

After reading you I checked how many atm at 3300.

I was shocked to learned that it was only 0.67.

So you are saying diving at sea, 30m deep, we are at 4atm, so air will expand 4 times going to the surface.

But at 30m deep at 3300m, we are at 3.67atm and go to 0.67. So it will expand 3.67/0.67 so that’s a 5.5x expansion.

You said 7 times: where did I go wrong?

I have never considered altitude because I never dived at altitude …

You misread what I wrote. I talked about two incidents, one at 3,300m, and the other at an elevation I did not name. I chose not to name it for a reason--it was a unique experience, and naming the elevation will name the people (for those in the know). But I realize that by reversing the process you did above, you would come up with it anyway. The incident in question occurred at about 4,900m.