Tank Choice - 5.7L Alu vs 7L steel

[Ashes]

Is your 15L pumped to 200 or 230 bars?

Steel tanks are 232bar, typically 220-225 once in the water.
Alu tanks are 207bar, typically 200 in the water.

 

[stepfen]

Ok, This is all off-topic.
I can hold my decompression stops, buoyancy is good, weighting is good.

I know how to do gas planning, and my planning is telling me I need either more gas or less time.
When I was with the instructor, this is what we did, and I used a rented Alu 5.7L.

This topic is about the differences between Alu and Steel cylinders.

Has anyone dived with a 7L Steel slung on the left?
How does it carry compared to an Alu cylinder?

Sorry but to me what is off topic here is whether alu 5.7lt is better than steel 7l or whatever.
Just my 2c. All the best...

 

[Diving Dubai]

How does it carry compared to an Alu cylinder?

Google is your friend

XS Scuba AL 40 - Dry weight= 7.9kg, Buoyancy (full) -0.4kg Buoyancy Empty +1kg

Faber 5L - Dry weight= 5.8kg, Buoyancy (full) -2.0kg Buoyancy Empty -0.5kg

 

[Graeme Fraser]

Ok, This is all off-topic.
I can hold my decompression stops, buoyancy is good, weighting is good.

I know how to do gas planning, and my planning is telling me I need either more gas or less time.
When I was with the instructor, this is what we did, and I used a rented Alu 5.7L.

This topic is about the differences between Alu and Steel cylinders.

Has anyone dived with a 7L Steel slung on the left?
How does it carry compared to an Alu cylinder?

I'd recommend an Ali cylinder as it's reasonably neutral so less likely to affect your balance in the water. This is particularly noticeable if you're diving a wetsuit rather than a drysuit. Correctly positioned you hardly notice it's there. Also has less tendancy to 'pendulum'. However, I'd go with a 7L Ali rather than 5.7.

 

[Ashes]

I'd recommend an Ali cylinder as it's reasonably neutral so less likely to affect your balance in the water. This is particularly noticeable if you're diving a wetsuit rather than a drysuit. Correctly positioned you hardly notice it's there. Also has less tendancy to 'pendulum'. However, I'd go with a 7L Ali rather than 5.7.

Thank you, this was what I was interested in hearing.
I was wondering how a more negative cylinder would carry on one side. It sounds like it is noticeable.

We don't have a 7L Alu tanks. The next size up for 207bar tanks is the 11L.

 

[Graeme Fraser]

Thank you, this was what I was interested in hearing.
I was wondering how a more negative cylinder would carry on one side. It sounds like it is noticeable.

We don't have a 7L Alu tanks. The next size up for 207bar tanks is the 11L.

Give or take, and depending on the make, an Ali cylinder will be slightly negative when full and slightly positive when empty, whereas a steel will transition from negative to less negative. In water an 11L will exhibit the same characteristics as a 5.7L as, although heavier, it displaces more water. However, it will be slightly more cumbersome. Shame you don't have access to a 7L.

Realistically you need to weigh up what is more important to you, the capacity of an 11L or the neat package of the 5.7L. I'd still be reluctant to go down the steel route though.

Ideally, see if you can borrow or rent to see how you get on with each.

Just to chuck a complete spanner in the works, if you're looking to combine a 15L and xL stage for extra gas, you might want to consider a twinset instead. Purpose built for the job.

Good luck and let us know how you get on.

 

[Ashes]

Thanks.
The Alu 5.7L looks to be approx -1 to +1kg & 7.2kg dry
The Steel 7L is -3 to -1 kg & 7.5kg dry

If was needing more air then twin 11L side-mount would be the way to go.
I would love to go twin-set, but it is not practical on the local boats I know of.

The Alu 5.7L also seems to be the most popular for a deco stage.

 

[Marie13]

Thanks.
The Alu 5.7L looks to be approx -1 to +1kg & 7.2kg dry
The Steel 7L is -3 to -1 kg & 7.5kg dry

If was needing more air then twin 11L side-mount would be the way to go.
I would love to go twin-set, but it is not practical on the local boats I know of.

The Alu 5.7L also seems to be the most popular for a deco stage.

So a back mounted twin set wouldn’t work on your local boats, but it sounds like side mount would? Totally the opposite here on the Great Lakes. What kind of boats are you diving from?

 

[Ashes]

So a back mounted twin set wouldn’t work on your local boats, but it sounds like side mount would? Totally the opposite here on the Great Lakes. What kind of boats are you diving from?

The boats are fairly small, typically about 6-8m. and we are in the swell on the open ocean.
Changing a wing between twinsets on the ocean is not something I will be attempting.

To be honest, though, I haven't asked the operators what they think about someone diving side mount.

 

[Marie13]

The boats are fairly small, typically about 6-8m. and we are in the swell on the open ocean.
Changing a wing between twinsets on the ocean is not something I will be attempting.

To be honest, though, I haven't asked the operators what they think about someone diving side mount.

These are recreational dives, correct?

It’s pretty common practice here to get two recreational profile dives out of one twinset. I’ve done it myself. No switching out twinsets.