Twinset - 7 or 10?

[hilrosepaul]

Since this picture was taken
http://i641.photobucket.com/albums/uu140/hilrosepaul/misc%20diving%20pics/DSC00517.jpg

I've acquired a Buddy tekwing, gone to a standard hose configuration and am settling in withouth the Pony until I am happy with a 15.

I am also considering going twins (balance and all that). the question now is 7's or 10's ? (I won't do the manifolded or indie - there are almost as many opinions about that issue as there are are twinset divers ;) )

I won't consider 12s at this stage

Twin 10s will more than replace the amount of gas carried in a single 15 and pony, but I've heard 7s are more balanced.

[Roz]

The answer pretty much depends on how much of an air pig you are.

I dived twin 7's for about 10 years and truly loved them because they are a dinky little rocket pack. Sleek, very low profile, superb balance. It's almost like diving without anything on your back. Started on indies and switched to a manifolded set. (I am much happier diving a manifolded set).

I recently tried an 8 litre twinset from Silent Planet http://www.silentplanet.info/diving-cylinders/cylinders-overview at a Demo Day and suffered a bad case of lust. Bit more gas and still as nice to dive as 7's. I've also dived twin 12's when the diving demanded it. Mate of mine has two 7 litre twinsets. One for the morning dive, and one for the afternoon. Never dived 10's so I can't comment on that one. Sorry.

If you're able to beg, borrow, set, hire a 7 lire and a 12 litre twinset off someone, do. Dive them yourself somewhere gentle with an experienced babysitter who knows about diving twinsets and get a better physical idea of how they perform.

HTH.

[SoggyBottoms]

It depends entirely on what diving you do, and what diving you seek to do in the future.
The tank decision on 7's or 10's or 12's depends on your gas planning.
Don't include your pony in your gas planning as it's a bail option and not part of your available dive gas

So tell us about your diving and perhaps we can dig in a bit more. For instance...

Twin 7 300bars have considerable more capacity than a single 15 and will balance you well. However, getting a decent fill is a pain in the behind.

[hilrosepaul]

I'm theoretically qualified to 35m, but my deepest dive is 28.

Most of my diving is in the 20m range.

I tend to swap the 15 between dives; so ideally would like to do two dives on one twinset.

The impression I have so far is that for the sort of diving I do; 12s are overkill; 10s are physically short, 7s are nice, but can leave you a bit low on gas.

Twin 8s or 8.5s seem a good compromise though.

I've considered 300 bar 7's; but have heard it can be difficult getting 300 bar fills (especially on boats)

Moving to twins seems a big change both in terms of config and finances, so I don't want to get it wrong.

[pete stiff]

I have used twin 10's for quite a while, manifolded, and have liked them for balance and air usage. I have used a single 12 with twin valve posts for second dive using seperate backing plate, twin posts mrean I don't have to alter reg set up.
However I have just changed to twin 7s because my type of diving has changed (age thing you know) wouldn't go back to single though, except when pool training.
My twins10s are up for sale and are currently being tested.

[Nigel Hewitt]

My twins were twin 10s and they worked well for me.

Admittedly they were a 300s so a bit heavy carrying them out to the car but I displaced 4L less overall that twin 12s so my all up weight climbing the ladder back into the boat (the only point where all up weight hits you) was 4Kgs less.

I've never seen the attraction in twin 7s. It's a 15 with added faff. Yes the 'twinset' brigade will say you can shut down one side but you wouldn't do a dive on them you wouldn't do on a single anyway so what's the point? I suppose it keeps tank testers in extra fees...

[Gordon]

I voted single - get happy with the 15, then stick a pony on and you are good to 30m ish. I wouldn't rush to change anything - you've got all the kit you need to do 28m dives, and if it works?!
I've bought a small (5L) stage that I put 50% in, so when I do more than 30m on a 15+3, my pony only has to get me to 18m if it all goes brown and spinny.

Gordon

[paul_c]

i know people who dive twin 7s and they realy are only for single dives regardless of how good you are on gas unless they are short and shallow.

personaly i think twin 7s are a good way to gain self bail out redundancy without having a source of gas (pony) which isnt used as planned gas. thats an oh XXXX supply. which is totaly different



i had a set of twin 10s 232 bar which was nice for me, but i needed to top up for a second dive (decanted from a 15 232 gave me around 140 bar) especialy if i was doing deco stuff it was enough for the dive but nothing
extra left over.

length wise it was a bit of a pain kitting up but i got used to it, and it was alot more stable than a single 15 when i got used to it.



i now dive twin 12s which tbh gives me enough for 2 decent dives.

may i ask why you are discounting twin 12s?

[hilrosepaul]

....may i ask why you are discounting twin 12s?

For the type of diving I do, (20m or so, recreational, looking at the squidgy stuff if there is any), twin 12s seems overkill; not to mention really heavy to lug around out of the water.

[paul_c]

its actualy the same MASS as a 15 and lead vs a twin 12s. or adda litle extra.

to go from twin 10s to twin 12s i have added a whiole 3/4 of a kilo. and thats for trim

i dive twin 12s for everything from a shallow 6m bimble to 45m deco dives. i just end up with lots of spare gas on shallow ones

[Gareth]

A lot of the previous posts have summed things up for you, so I'll repeat:D .

Yes it is dependent on the diving you are doing. But going on the basis that you are doing SD diving, no deeper thatn 35m with a little decompression.

If you are already using a 15 & a 3. The twin 7's won't be much if at all heavier. They will however be far better balanced. You won't have 'additional testing' because you already have a 3 & a 15 to test anyway. What you will find is that you do have an extra fill. On your current setup you probably only fill the 3 once every 3 - 6 months. With the 7's you will normally fill both after every dive.
The downside of twin 7's is that you will have insufficent gas for a second dive if doing two dives off a day boat. The solution is either
* a second set of 7's
* Keep your 15l, & invest in a decanting whip, then you can top them up after a dive.
* your existings set up, & swap over. But this will be lots of faff, even with a dual outlet.

Over the years we have had a lot of twinsets in the branch, even from back before they where in vouge. Twin 7's have proved very popular with some of the more sensible members (who don't hold with long deep dark dives:D ). For some of the women, the improved balance (over a 12 & 3), has made them an instant hit. A set of 7's, a 15 & a whip has been enough to make them firm favourites.

If you are looking for deeper dives, or dives involving long decompression stops then the 7's are to small. Basically there is insufficent gas.

What you need to do is look at the diving you are doing, look at what you want to do over the next 12-24months. Do the gas calculations. Then you are in a position to make a decision. If you have the opportunity to pick up a second hand twin set, this may well force your hand.

One last thing, check what your BC can accommodate. A slimline may start to struggle with a set of 10's. Also whilst the Buddy twining bands work, if you have a maniflod the cylinders will need proper SS bands to stop them twisting & straining the manifold. To be honest in my view proper SS twining bands are much nicer regardless.

Gareth

[Maria]

Your diving is in the 20M range.... what's wrong with a single 10? :D

[Kris2]

Hi Paul, nice to see your sorting your kit. Why dont you keep things simple for a while. dive a single 12 and side sling your pony.use standard reg hoses rather than the 2m miflex.
as your ponys side slung the hose is stowed neatly as well and you wont have the problems you were with it mounted on your tank.
When you get the urge for twins you can try my 12,s that are also on a buddy wing.never tried twin 10,s but apparently they are harder to trim than 12,s.
best wishes, chris.

[hilrosepaul]

Your diving is in the 20M range.... what's wrong with a single 10? :D


I turn into a hoover underwater - that's why I moved from a single 12 to a 15. I've dived 10's on holiday in 20 degree plus water, wouldn't like to do it here

[hilrosepaul]

Hi Paul, nice to see your sorting your kit. Why dont you keep things simple for a while. dive a single 12 and side sling your pony.use standard reg hoses rather than the 2m miflex.
as your ponys side slung the hose is stowed neatly as well and you wont have the problems you were with it mounted on your tank.
When you get the urge for twins you can try my 12,s that are also on a buddy wing.never tried twin 10,s but apparently they are harder to trim than 12,s.
best wishes, chris.

Thanks for the offer Kris.

I've ditched the pony for now and have reverted to a single 15 with standard hoses.

I've also had a couple of offers re twin 7s - just need to do some thinking now.

Follow on question - how much could I expect to be forking out for a decanting whip and a twinning kit for a Buddy Tekwing?

[Fiona]

For balance alone don't even think about 15 and a pony. I used to use twin 7's but you really need two sets for a days diving which makes everything a bit expensive in terms of servicing.

I tried 10's but they were too short and I am only short, but I know a lot of men use them, as Roz said twin 8's are very nice in terms of length and balance.

In terms of gas planning a pony in an emergency is pretty useless.

[MattS]

I've also had a couple of offers re twin 7s - just need to do some thinking now.If you are going for 7s, get 300 bar, is my advice. Even if you can't get them filled above 232, it's less weight on your belt. Another option for indi 7s, is to get 3 x 7Ltr cylinders and swap the empty for the 2nd dive. Personally I wouldn't use 7Ltr indis unless I was really desperate, due to the lost gas plan.

My first twinset was twin 10s indi on a Buddy Slimline, they got manifolded after a year and yes they were a PITA to trim out. I currently have a set of 7 x 300s manifolded for general stuff and a set of 12 x 232s for 35m+ stuff. I am though, a 5' 6" short arse and breathe like a girl. Love the 7s, but not sure I would want them as my only twinset.

If it were me. I would probably want to get the breathing down to a sensible rate before moving on from a single.

[Gareth]

Prehaps I should have asked this earlier.

Are you certain that you have got your weighting & trim sorted?
I have seen people buy twins in the past due to high air consumption issues. When you look closely they are carrying far to much lead, & have trim or technique issues.
The other major problem can be one of mental comfort, if you are stressed then your air consumption will be high (or hogher than it needs to be).

Is there a particular period when air consumption is high during the dive? Rather than just being in the water!


Gareth

[hilrosepaul]

Prehaps I should have asked this earlier.

Are you certain that you have got your weighting & trim sorted?
I have seen people buy twins in the past due to high air consumption issues. When you look closely they are carrying far to much lead, & have trim or technique issues.
The other major problem can be one of mental comfort, if you are stressed then your air consumption will be high (or hogher than it needs to be).

Is there a particular period when air consumption is high during the dive? Rather than just being in the water!


Gareth

Even though I turn into a hoover underwater; my primary reason for considering twins is balance rather than gas consumption.

I have a couple of questions, which hopefully aren't too silly:-

How do you go about mounting twins on a Buddy Tekwing? would I still need to use Buddy Twinning Bands and Blocks; even if the twins already have steel bands?

My Tekwing has two cambands - will I need two sets of blocks and bands?

[Gav S]

Even though I turn into a hoover underwater; my primary reason for considering twins is balance rather than gas consumption.

I have a couple of questions, which hopefully aren't too silly:-

How do you go about mounting twins on a Buddy Tekwing? would I still need to use Buddy Twinning Bands and Blocks; even if the twins already have steel bands?

My Tekwing has two cambands - will I need two sets of blocks and bands?

Independants mount with bands and the blue blocks (two sets) and there would no need or benefit in metal bands as well.

I must say I'm not certain about manifolded sets. A manifolded set must have the metal bands in place for solidity of the manifold but in theory could then mount as a unit to the wing with the two sets of buddy bands but no blocks. However, I am not actually sure if the spacing of the cam-band slots in the wing would match, in terms of width, the spacing of metal twinning bands - presumably if these did not agree with each other the cam bands could/may stress the twinning bands.

I am not getting into the cylinder size debate...:) except to say if you have a manfolded set you must be able to reach the valve or else you are in effect diving a single cyl; and, avoid indy 232 bar 7s (basic gas calculations to see why).

Personally I am tempted to say indy 232 12s for you - simple, logical redundancy at this stage and you'll get two dives a day without a fill. They break down for lugging about. You'll get well planned deeper dives out of them if you want. Use them as singles on an old BCD for shallow shore dives, training days etc.

...or manfolded 232 7s, if you have access to fills on all of your dives, can reach the valves, have access to advice and are prepared to practice.

[Richard Whitcombe]

Twin 7s are ok but have one massive drawback - unless you own 2 sets you need access to a fill after every dive which can often rule out all-day RIB and charters.

To be honest, for 25-35m range id just take a single 12 or 15 and side sling a 3l pony and be done with it.

[sjc]

10s are typically dumpy cylinders, and on a rib are a bit hard work as you can't easily sit the bottom of the cylinder on the tubes (especially if you've removed the boots) whilst kitting up.

7 232s are great, 7 300s are also great, but hardly anywhere gives you a decent 300 bar fill.

7s fit nicely in a bottle rack, 10s a bit more greedy, 12s take the p on a rib

I have all 3, all useful for different occasions.

Steve

[kdtan]

i couldnt help looking at your picture wonder - if you are wearing a long hose - why does it also look like you have your secondary rigged for donating? its hanging v low and coming through under your shoulders (not to mention being yellow and all that).

[TerryH]

i couldnt help looking at your picture wonder - if you are wearing a long hose - why does it also look like you have your secondary rigged for donating? its hanging v low and coming through under your shoulders (not to mention being yellow and all that).

Yes it's a bit messy, but he does say that it's an old pic and he's now
changed the config.

[paul_c]

i couldnt help looking at your picture wonder - if you are wearing a long hose - why does it also look like you have your secondary rigged for donating? its hanging v low and coming through under your shoulders (not to mention being yellow and all that).


i have mine like that as it permits the non techy divers in the club, in an emergancy to grab the reg the see from muscle memory.

the necklace it sits on has been made so that it WILL ping off if pulled hard to let them have it.

[Tristan]

Here is my 2p.

I started diving with a 15L with a 3L Pony which was more than adequate for a variety of diving. Then I upgraded the 3L for a 5L Faber so it conformed to the rule of 1/3's when Wreck diving.

Great set-up but balance was not as good as it could be. Completed a Twinset course and got Twin 12's which was great and the redundancy should there be a problem was brilliant and it really does give you a safe feeling on deeper dives.

Twin 12's proved to be fairly heavy and not ideal for the diving I was doing 2 years ago as alot of it was shore diving so I sold the 12's and went back to a Single 15L with a 3L pony again :rolleyes:

I have recently started diving fairly deep again and I have just bought another Twinset (Twin 10's) for the deeper stuff and I am keeping the 15L / 3L for the shorediving and shallow stuff but I have the option of the Twinset for the deeper diving.

Ideal if you can afford two set-ups but budget for increased servicing costs and wife trouble :)

Twin 7's are a good compromise but as mentioned if looking for a 300bar fill it may become difficult. Maybe Twin 7's with a 7L Aluminum Stage?

[Tristan]

And consider carefully which harness to use with a Twinset. Dont be suckered into the DIR route and end up with 2 seatbelt straps digging in because 'no breaks' is super safe! I have personally never known a shoulder strap pinch clip to give up and if it did with a Twinset you have the waistband AND a crotch strap not to mention the other shoulder strap holding the set on so its not the end of the world. With my first Twinset I had the Halcyon kit and I agree it is very good quality gear but I think the DIR following should be taken with a pinch of salt.

Although I agree with some of the thinking some of it is rubbish in my opinion. Getting out of a set and comfort is equally important in my opinion. I have opted to go for a Scubapro X-Tec Pro Harness this time round with a single break in one shoulder to aid getting it on/off and more padding than seatbelts ;)

[paul_c]

you had the harness far to tight then. mine is actualy hanging off me and still keeps me in it.

[Tristan]

No it wasn't too tight just a case of bare 'seatbelt' harnesses are generally uncomfortable compared with others when supporting close to 35kg..

[ChristianG]

I have personally never known a shoulder strap pinch clip to give up
It wasn't the shoulder strap but I lent my wings-style BCD to a quite hefty lad to try out and it came back with the pinch clip broken on the waist strap. Come to think of it, he never did offer to get it repaired - Tsk!

Mind, that Wing (? - it was a very early version, circa '92) had been built for me and although I was a tad taller than the lad I was in no way his peer when it came to pure beef. He must have been a good 120kg in those days when I've never broken the 95kg barrier.

[Nigel Hewitt]

Dont be suckered into the DIR route and end up with 2 seatbelt straps digging in because 'no breaks' is super safe!
ROTFL.
I had a 'discussion' with a purest on a boat once about my harness break clip and as a result deliberately did a whole dive with it undone.
It was a bit wobbly climbing back up the ladder but it worked.

He didn't like the inverts one bit but I don't think he noticed the two SPGs.