Speaking from personal experience, ( i used to dive an 18 + 2 pony's).. there is no benifit in using twin 12's as far as quantity ofgas goes, but in every other way twins are better.
better balanced, im tall but still found the 18 a bit hefty,also the 18 gets quite floaty when down to 50bar.
if like i did, you plan to dive the 18 with a bc, good luck, i found it was a pain to dive with (never tried a single 18 on a wing - might be ok) since getting the twins ive not done any single tank dives,put my bc up for sale and use my 18 to top up my twins for a second dive.
twins & wing is the way to go!
I've always been of the opinion no point using a sledgehammer to crack a nut, ie If I'm only doing shallow stuff from the shore or unlikely to do any decompression I don't see the point in staggering around with the extra weight of twins. For the majority of diving I do and withy my air consumption a single cylinder and pony is adequate.
However if you want redundancy twins have got to be the way to go, agreed.
Having had a few conversations with Dave Willo he testifies his wings backplate and twins are more comfortable than his single ever was. Hmmmmm interesting
Nigel/Duncan, just curious - how much does your 18 weigh? Is it taller than a 12?
I'm buying a 2nd 12 now. My reasons are redundancy, quantity of air and balance. I've tried 2x12 and the position is much more stable. I hope to lose some lead, and I like the fact I'll usually have more gas than dive time.
Hopefully some of the old and bold will give you their reasons from experience...
Nige how you're well, and hope you might be able to join us at St Abbs this year eh?
Anyhow, I have moved onto twin 12's and find that the wieght is almost the same as the 15 and pony weighed. With that combination I used 3kg of wieght, now about 4lbs and the twinset, balance is much better, although I didn't realise there was a problem with that until I went to the twinset. How much would the 18 and Pony with clamp weigh?
The only problem I need to decide now is whether to invest in a pair of twin 10's for 2nd dives and sell the 15's and pony setup.
do i dive with the isolation valve open or closed could i use the twins as a single and then use a pony as a independant air source so there would be no changing regs all these questions and no answers!
When I first bought manifolded twins I dived using them as independants, breathing one tank to 100bar then switch regs, all the time practising to reach the isolation valve.
Then when I could reach the valve I periodically throughout the dive openned the valve and then shut it untill I could do it easily. Now that I can do it easily I leave it open.
I `m not really sure thats the right way to do it but it suited me.
Since then I `ve seen new twinset divers on boats diving with the isolation valve open and no pony and admitting that they cannot reach the valve easily.
I'm with you on that, my twin tens are very comfortable, I plan to use them for everything including shore diving, plus you don't have to deal with that off-balance feeling I used to get with using a pony
treat me like a numpty and tell me what is the best possible set up i can use I have twin 12s 3lt pony din conection and reg.I have 2 sets of regs one with air intergrated dive computer. what be the best set up to use.
I dive with a dry suit so on my main reg i have reg and oct, dive computer,bcd feed,dry suit feed,on my other set of reg I have reg,oct,and console.helpppppppppppppppppppp !