15 or 18ltr

[lawrence]

I've been using twin 12s for a few year now but have reached the stage that I need a bigger set. I was using 15s in the Red Sea last week and once the trim was sorted, found them quite nice to use. Being 6ft, they were a little short for me when sat on the bench, in the water though, fine.

However, it's been mentioed to me that 15s are 'not very DIR' and 18 are moor suitable. Can anybody eloborate on this, or share their experience with twin 18s?

Cheers,

Lawrence

[Rick Huggins]

Surely the dive/gas planning dictates what the correct cylinders to use are?

[Garf]

my experience with twin 18's


Picked them up. Swore. Put them down. Ran away and hugged my twin 12s

[Fraser]

Hi Lawrence,

What sort of diving are you thinking of using twin 18's for?

Fraser.

[Howard Radcliffe]

There is nothing non DIR with 15's. If they are weighted correctly and they have enough gas in for the dive your're doing, then they are fine. I would think that 18's are overkill, unless you are going very deep 80m+ or you are doing long bottom times at depths over 65m.

The good thing about 18's is they are a nice length for kitting up, I find 15's quite short and they look a bit dumpy 18's are the same diameter as 15's so you arent increasing your profile in the water for the extra gas.

The down side to 18's is they cost more to fill up.

[Mark]

Originally Posted by lawrence

I've been using twin 12s for a few year now but have reached the stage that I need a bigger set. I was using 15s in the Red Sea last week and once the trim was sorted, found them quite nice to use. Being 6ft, they were a little short for me when sat on the bench, in the water though, fine.

However, it's been mentioed to me that 15s are 'not very DIR' and 18 are moor suitable. Can anybody eloborate on this, or share their experience with twin 18s?

Cheers,

Lawrence

You may find that an AL80 of backgas and your twin 12's is a much more flexible way to go which can/will save you a fair amount in fill costs.

Regards,

Mark.

[lawrence]

Fill costs are not an issue- this is for work. They're intended fro 90m dives. However we'd also use them for very long bottom times at shallower depths, where for us they'd have the advantage of simplicity over twins + al80 of bottom gas- we want to just drop down, do the work with as simple a configuration as possible.

[NotDeadYet]

Originally Posted by lawrence

Fill costs are not an issue- this is for work. They're intended fro 90m dives. However we'd also use them for very long bottom times at shallower depths, where for us they'd have the advantage of simplicity over twins + al80 of bottom gas- we want to just drop down, do the work with as simple a configuration as possible.

I used to use twin 20's, hence the reason I built my rebreather. They are feckin' heavy, forget getting back in a boat with them. Even taking them off in the water is a nightmare to haul them back up. On a cave diving trip to France a few years ago it took about 40min of absolutely knackering effort to haul them up a 3m pitch. You're looking at around 50kg fully rigged.

Lovely balance in the water though.

[Howard Radcliffe]

For 90m dives, I'd go with the 18's. You might want to get down to the gym and do a lot of squats!!