how fast to ascend...

[birdwrasse]

i know the rules, but what i'm looking for is a way to learn to ascend without watching my sunto cobra or sunto mosquito... if there is a failure in both or even a failure in my primary air source, and switch to my redundant air source...

i usually swim up slowly, but sometimes it feels like i'm not moving anywhere, and when i check the computer, the depth reading isn't changing...

i know the computers are conservative on the ascention rate, say 40 ft per minute and you can go up to 60 ft per minute... when i watch the computer and i'm getting close to the slow indicator coming on, i slow down, but the starting and stopping on the ascention is not giving me the right perspective on speed. when i do a shore dive, it's not a big deal because i just follow the bottom in...

the muscle memory will develop in time, but am wondering if anyone uses a special technique to learn this speed without a computer... i know about the smallest bubbles, but if there was an emergency, i'm wondering how practical that one would be... staying calm would work in this case, but again, just want to learn as much as possible...

knowing this too will help in avoiding getting bent, i'm assuming...

thanks,


--carlos

 

[jeckyll]

Watch the small floaty bits in the water (as long as there is no great amount of current) as a reference point

Or of course a backup depth gauge. I picked up an analog Mares (Burdon tube) used off ebay for around $20. Works great. Requires no batteries.

Good luck.

Bjorn

 

[birdwrasse]

the extra depth guage is a really good idea... a manual one wouldn't cost much, and i can attach it to my redunant air source... does that attach to a LP or HP, port...? my 1st stage regulator (the redundant one) only has one HP port, and there is a pony bottle guage there... i guess i'd have to find a depth and pressure guage combo if i have to use the HP port...

 

[rawls]

You can ascend at 60 ft per minute but should go at a slower ascent rate, especially as you get to about 2 ata....about 30 ft a minute...maybe even slower...Boyles law... If all is lost...computer, depth gauge, then ascend with others. If there are no others then don't ascend faster than your smallest bubbles....

 

[stevetim]

If towing a line, I just use one revolution per second on the reel. I'm talking about the 3" diameter hand reel.

Without a reel I swim horizontally, and check wrist CPU every 10 kicks.

 

[kidspot]

I watch my gauge and count slowly to 2 between every foot until 10ft. Then I count slowly to 6 between every foot I ascend. I find this a lot easier than following the graph my computer shows.

I tried watching the "floaty" stuff in the water but it seems to move around a lot in the surf over here.

Aloha, Tim

 

[birdwrasse]

You can ascend at 60 ft per minute but should go at a slower ascent rate, especially as you get to about 2 ata....about 30 ft a minute...maybe even slower...Boyles law... If all is lost...computer, depth gauge, then ascend with others. If there are no others then don't ascend faster than your smallest bubbles....

is there a way to make a lot of small bubbles and keep them coming up in front of your mask so you can see them moving... my regulator deflect the air the left and right of me, so i'd be swimming in spirals...

 

[jeckyll]

the extra depth guage is a really good idea... a manual one wouldn't cost much, and i can attach it to my redunant air source... does that attach to a LP or HP, port...? my 1st stage regulator (the redundant one) only has one HP port, and there is a pony bottle guage there... i guess i'd have to find a depth and pressure guage combo if i have to use the HP port...

Wrist mount would be the way to go. I keep mine on my right wrist, with my computer on my right forearm.

I'm not sure what this has to do with an SPG.

 

[diebeste]

the extra depth guage is a really good idea... a manual one wouldn't cost much, and i can attach it to my redunant air source... does that attach to a LP or HP, port...? my 1st stage regulator (the redundant one) only has one HP port, and there is a pony bottle guage there... i guess i'd have to find a depth and pressure guage combo if i have to use the HP port...

They do not have to attach to anything on your regulator. You can mount them on your wrist, clip to your BC, or whatever. You might be confused with some combination gauges that show tank pressure and depth. They attach to an HP port to show the residual tank pressure; they generally have a hole in the back to pick up the water pressure (and therefore the depth).

Keep in mind that different depth gauges have different error rates based on altitude, and fresh or salt water. This includes your dive computer.

About the difference between HP and LP port - your tank has an internal air pressure of between 300 bar (some HP steel tanks, full) and 0 bar (empty), but generally above 20 bar or so. This is too high for your second stage to allow you to breathe off it, so it is reduced to between 9 - 12 bar (depending on your brand of 1st and 2nd stages), called the IP and available on the LP ports of your 1st stage. This allows your primary 2nd stage, octo, power inflator, etc to work with lower pressures. To measure the pressure of your tank, however, you need access to the full pressure (HP port). This is used for air gauges.

As an aside, the HP holes are generally very small (the gauges require the pressure, not a lot of air), so rupturing an HP hose will result in loss of air, but not immediately catastrophic. The LP holes are much bigger, to allow you access to a lot of air if required. So rupturing an LP hose (of which you generally have at least 3, and possibly even 4 with a dry suit) generally leads to a catastrophic loss of air. Think empty tank in less than 1 minute.....

 

[ChrisA]

a 30 foot per second rate is about ideal. You can do this easy if you move up one foot then count "one-onetousand, two-onethousand" then move up one foot and count out two seconds again. repeat until you reach the surface. This is dead easy if you have an anchor chain but you can do it if you have any visual reference or of course a depth gage. Just count out 21 seconds per foot.

If all else fails just make sure your smallest bubbles are going up faster than you are and yo will be OK.