HP Tank

[Slym]

So I suppose I am over estimating a steel tank and its capacity, I figured I would be able to dive within my no stop limits both times, for about the same time I would get on an AL.

Also this will be my first time in water up here, so it will also be my first time in a 7mm I figure already I will be having some buoyancy issues to figure out in the first few minutes of the dive. I am not too sure if I would be cutting it close with my weighing, I believe I need 16 pounds of weight in a 7 mm a (I am tall and stalking weighing about 155-160) my bcd is about 10 pounds so I would have to ask the dive shop about the tanks characteristics so I could figure out if I were overweight or not.

Given what you guys are saying I will probably go with 2 AL80s

Also Fogest: who are you getting certified with?

 

[rx7diver]

So I suppose I am over estimating a steel tank and its capacity, I figured I would be able to dive within my no stop limits both times, for about the same time I would get on an AL.

Also this will be my first time in water up here, so it will also be my first time in a 7mm I figure already I will be having some buoyancy issues to figure out in the first few minutes of the dive. I am not too sure if I would be cutting it close with my weighing, I believe I need 16 pounds of weight in a 7 mm a (I am tall and stalking weighing about 155-160) my bcd is about 10 pounds so I would have to ask the dive shop about the tanks characteristics so I could figure out if I were overweight or not.

Given what you guys are saying I will probably go with 2 AL80s

Also Fogest: who are you getting certified with?

The *buoyancy* (rather than the *weight*) of your empty BC is what's important. I suspect your BC is not 10 lbs negatively buoyant. Could be that a taller diver in a full 7 mm Farmer John wearing a HP 100 (is this correct? Not HP 130, correct?) with work perfectly. Any chance you can have your single HP 100 filled on-site? Or rent two HP 100's?

Safe Diving,

rx7diver

 

[tursiops]

@Slym, what weight do you normally use, with what equipment/tank? Is your only change to a 7mm (from a ?mm)?
All you can do is estimate....in the end you MUST do a weighting check at the beginning of your dive, so take along some extra 2 and 3lb weights.

 

[Slym]

The only in water experience I had was in the Caribbean in 3mm full suit, where I had no weight beyond my bcd. The BCD has an integrated weight that is 10 pounds. lol should have said that earlier sorry.

and there is no beating a weight check!

What I ended up doing is renting an AL80 and a HP130 from the shop so now at the minimum I will have 2 dives and at the most 3. The depth at the scuba park is 30' at the most I hear so we will see how things go tomorrow!!!!

It will certainly be a day of experiencing new diving, since I am pretty new and never have dove in cold freshwater before. The temp should be about 50 degrees and I will be in full 7mm with hood and gloves. I have extra weight with me for the AL should I need it (which I will)

Can't wait! If I like it enough, then a gear purchase is my next move!

 

[tursiops]

I'm guessing with an AL80 you'll need an extra 8 lbs when you go from a 3mm to a 7mm/hood/gloves, and another 4-6 lbs to go from salt to fresh water. So that is 12-14 lbs on top of the 10 already in your BCD....22-24lbs total.

Using the HP130 instead of the AL80 will drop the weight needs by maybe 9 lbs, so you are back down to the 16 lbs you are starting with.

HP130? Really? You previously mentioned HP100. Most of the previous comments (about take two AL80s) were based on a 100 being not much bigger than an 80. The 130 IS almost twice the 80, so two dives become reasonable.

The 30ft max depth is a big deal. There is no way you will hit your NDL. The PADI RDP gives 205 mins NDL for 35 ft. You'll freeze before then!

 

[Slym]

Well looks like I am getting a fair amount of diving in tomorrow!

And yea the dive shop ran out of HP100s so I am going with the 130 instead, figure I will give it a try, and when I heard the depth, I knew I would have no problem with NDLs as I am a pretty skinny guy, I will probably get cold... good thing the surface is around 31 degrees (that is today similar for tomorrow).

It should be a good day for experimenting with what I will like and not like. Should be a pretty safe environment too with all the divers around me so I should feel pretty comfortable.

Also I see you have quite a bit more experience than my 12 dives, but the estimation of 22-24 pounds seems a little high... I estimate with 10% of my body being 16 pounds. Then having the 10 pound bcd, about (roughly) 1.5 pound regs, I should only need 3 pounds in each pocket that will make me about 17 pounds. Doing a float check on the surface I should tell right away what I will need. that is with the AL80

With the HP130 I believe I will be over weight with no additional weights at the beginning of the dive. I'll see though. Please correct me if I am missing something, as I am still learning quite a bit, hence me posting this thread.

 

[rx7diver]

... and another 4-6 lbs to go from salt to fresh water.

This is backwards. turnips, I know you know this. Probably just a typo.

 

[rx7diver]

Slym,

I like to remind newish divers of the fundamentals they were taught in their open water course: If in trouble at the surface, release your weightbelt (release your integrated weights)! The tacit assumption is that by doing so you will become significantly positively buoyant at the surface and will remain at the surface—even if your tank is completely full and your BC is completely empty.

Depending, a HP 130 (or a LP 104) might not permit this. (See Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan, for example.)

Safe Diving,

rx7diver

 

[tursiops]

This is backwards. turnips, I know you know this. Probably just a typo.

Oops! You are exactly right. Shouldn't try and write in a hurry....
@Slym is correct that my numbers are high! By 8-12 lbs! (Subtracting rather than adding the salt-fresh conversion, which is about 3% of body weight.)

So my post should have said:
I'm guessing with an AL80 you'll need an extra 8 lbs when you go from a 3mm to a 7mm/hood/gloves, less about 4-6 lbs to go from salt to fresh water. So that is 2-4 lbs on top of the 10 already in your BCD....i,e, 12-14 lbs total.

Using the HP130 instead of the AL80 will drop the weight needs by maybe 9 lbs, so you will only need maybe 4 lbs in your BCD instead of 10.

My apologies.

 

[boulderjohn]

On days set up like this one, you will not really be doing normal diving. It's a great day to have fun and experiment. Take advantage of it! It's hard to have such an opportunity to play with weighting, buoyancy, etc. If I were you, I would be doing a series of small dives, playing with different configurations and talking to the experts who are on hand to give you suggestions.

To give you an idea of what you can learn, I once had a student do his OW dives with me in fresh water and using a 7mm suit. He had intentionally done his pool sessions with a 7mm suit so he would know exactly what he needed for the OW dives. When he told me that, I looked at his slight build and thought, "No way!" We got him down to 10 pounds as we experimented, and he was a much happier camper when we got there than when he started. (I never got to ask the instructor who did the pool sessions WTF.)