Bardo and Boris sitting in a tree... ;)

[Janos]

Originally Posted by Clare Gledhill

We do 30 minutes on the bottom (plus a descent time which you would include on your calcs as a 35 minute dive) so only 5 to 10 minutes less than you on twin 12s and bottom stage. One twin set lasts two days but we kill a bottom stage on each dive. Gets us round the fill problems too.

But do you not breathe some of the twinset on the way back up? Doesn't this (admittedly only slightly, assuming you don't breathe much of it) compromise your second dive?

One of the big reasons I went CCR became clear after my suspected bend last year. I could have been diving Nitrox, but didn't because of the logistical hassle, and so dived air.

Now you could argue that I could have sat out some of the dives, waiting for my twinset to fill but that wasn't an option. Generally if I go away for a weekend diving in the UK, the first fill is Nitrox, because I get that from the local shop. Fills throughout the weekend tend to be progressively weaker air tops, just because the dive shop closes.

The breather has obviously solved this, but it comes into it's own when you start talking mix. Often it's cheaper for me to top up my dil bottle with 18/52 then it is to air top it (as I'll have to drain it again before the next mix dive). So I now dive 18/52 for everything. Even if it's a 30m dive.

Gas costs and logistics are now no longer an issue for me. That's been a change in attitude on my part. Now you could argue that a breather isn't necessary to make that change in attitude. There are other ways. But a breather makes it sooo much easier.

Thing is, with OC everything is planned to the knife edge. "Rock bottom" and "Minimum gas" and even END. If you stay too long then you are significantly cutting into your into your reserves. CCR gives you time. Trapped in the wreck? Spend two hours cutting yourself free? On CCR you can make it (although don't expect any biscuits left when you surface).

Janos

PS - Mark - I'm afraid I must disagree re the 50m thing - for me the OC / CC switching point is between 30m and 40m (I'm not sure quite where). But definitely if you are diving regularly below 40m then I think CCR is significantly safer. Above 30m it's OC. The main reason being the time that CC gives you.

[Mark Chase]

People always come back telling me they get Trimix for less money than I can get it at raw Helium cost from Lindy Gas. I on the other hand have Kent Diving (86mile round trip) or Dive Machine in Tunbridge (70mile round trip)


Soooooooo I phoned Kent Diving and asked for a set of twin 18s of 16/55 and two ali 80s of 50% and 100%


And gledders is correct I was way out on the prices I used from my OC days two years ago.


















£145 Just for the twin 18's

An Ali 80 of 100% was 24.00
An Ali 80 of 50% was 14.00


Bringing the bull for the gas for the above dive to £183.00

I do apologies for my gross error.

Oh yes and the 170miles of driving I have to do to get my fills works out at another £59.50 using the 35p a mile method or £26 in petrol if you ignore the other expense of driving a car.

So add another 13.00 per dive brings the cost of a 70m dive to £206.00 for the gas.Thats per dive. Two dives £412.00 in gas. Same dive on a CCR £28.00 in gas & lime and throw in a £5.00 for the anual cost of cells and batteries. £33


Sooooooooooo £412.00? or £33.00?

On OC I managed to do about 6 60m+ dives a year

On CCR I booked 32 this year and managed 21. Bassed on Kent Divings figures I would have to do 75 60m+ dives a year to equal the cost of doing 6 OC 60m+ dives.

ATB

Mark Chase

[And]

Hi

The gas price of £38 is probably the 'remix' charge at UE, Portland. If you turn up with 70 bar (I think) in your twins it is cheaper for a fill. The twinset is breathed a bit on the dives, but we really only care about the 'minimum gas' or 'rock bottom' quantity, which is about 130-150 bar on these kind of depths, depending on the ascent.

Therefore you save your reserve over a number of dives, at the cost of carrying more bottles, and when you are swimming those bottles, you have higher breathing rates, so there is an element of diminishing returns.

As far as rebreathers being safer than OC, I've done that debate too many times to join in again. Nice report Bardo, although when I did the try dive on AndyP's Inspiration, I didn't like all the bulkiness of the kit, and reduction in visibility due to the breathing hoses. It was like swimming through treacle. The horrorbox looks a bit better in this regard, but I am happy with OC. It serves me well for the mixture of wreck and cave diving I do.

Andy

[Mark Chase]

Originally Posted by Spike Jackson

Where do you get your gas Claire? My LDS is considered really cheap for trimix and a twinset of 18/45 costs me £45 per fill. The deco fills would work out considerably more than yours too.

We used to say £1 per He % for garage fills so twin 12s of 18/45 would cost £45. or 22.50 for a 12 so twin 18s would cost about £67.50 for a garage fill. 02 was 0.6p a ltr so a 10 of 100% would be about £15.00 and a 50 would be arround £8.00

So this dive on garage fills works out at £90.50 in gas. This takes no account of the time required for filling or profit and I doubt if it covered anythnig for the compresor, loombe, trimix analisor etc etc. It was just a bunch of M8's filling gas.

However this was two years ago and gas has gon up a lot since then. i am being quoted 1p a ltr for 02???

ATB

Mark Chase

[Al_Star]

Clare is quoting Breakwater prices in Portland which can be found on their website.

Dive Charter with Dive Dorset - Recreational, Technical Scuba Diving

18/45 remix in twin 12's (turn up with 70 bar) £28.20
18/45 in bottom stage £20.10 (missing from the site but what they charge)
50% nitrox £7.10
100% £12.10

I can get 20 mins of bottom time out of an AL80 stage so I then spend the next 10mins on back gas. That gives me 30mins on the bottom (excluding descent). As I only use my twinset for 10mins of bottom time and the deep stops it will do 2 days before it needs a refill. Typically I get my 50% bottle filled after a dive although you can make it do 2 dives if you've been relaxed on deco. The 02 definitely lasts a couple of dives

£28.20 / 2 = £14.10
Bottom stage = £20.10
50% = £7.10
£12.10 / 2 = £6.05

Total gas cost for a dive £47.35

I always get remix prices and to solve the travel problem I simply leave with a full cylinders at the end of the trip. Then when I'm back for the next trip I've already got the gas. This does rely on dedicating a twinset and bottom stage to trimix.

TBH - this is what I do. I'm not trying to find silly prices, this is where I get fills along with a lot of other sensible people. If you are unfortunate enough to not get better prices try buying your fills down on the coast! Sorry Mark - I know you need to justify the cost of the rebreather to yourself

Cheers
Al

[Al_Star]

Sorry for the hijack Bardo - looks like you had fun!

[Mark Chase]

Originally Posted by And

Hi

As far as rebreathers being safer than OC, I've done that debate too many times to join in again. Nice report Bardo, although when I did the try dive on AndyP's Inspiration, I didn't like all the bulkiness of the kit, and reduction in visibility due to the breathing hoses. It was like swimming through treacle. The horrorbox looks a bit better in this regard, but I am happy with OC. It serves me well for the mixture of wreck and cave diving I do.

Andy

The safety issue is simple enough. Whats more likely to kill you on a 60m+ dive? running out of gas or a CCR failure. Based on my OC experience I hated the time pressure of the limited gas supply so for me it was a no brainier.

Now having dived a CCR for two years I cant get my head around what it can do to go that badly wrong. Sadly having read about so many good divers getting killed on them I wait in fear of the "issue" thats going to put me to the test. This fear keeps me honest but I don't know if thats enough to avoid the issues.

What I will say is I have personally witnessed several very good divers taking massive risks on faulty CCR equipment that i wouldn't take. I have also been privy to information about some of the incidents that (if found to be true) makes you wonder what the hell the diver was thinking when they jumped in.

On the secondary issues of drag clutter restricted visibility etc, I agree totally. It is far far nicer to dive on OC than CCR YBOD

There are ways around the issue like rear mounted lungs and smaller units like the KISS or the Meg. I am in the market for some rear mounted lungs at the moment. When i get them you should have another go with the deco weeny travel frame and the clear frontal area. I dived the rear lungs last week and they were superb. The Travel frame is a major leap forward in drag reduction and trim.

Sadly I cant do anything about the breathing loop

The Boris is about the same size as the YBOD but I am told it swims better. However I am also told the low down weight is difficult to trim out (same as on the YBOD) but there is no provision for a counter balancing top weight.

By comparison my YBOD had a 2.5Kg top weight. My Decoweeny frame has none and i was able to ditch the 2.5Kg totally.

ATB

Mark Chase

[Clare Gledhill]

EDIT - bloody hell - team posting here - beaten to it by Al

Originally Posted by Spike Jackson

Where do you get your gas Claire? My LDS is considered really cheap for trimix and a twinset of 18/45 costs me £45 per fill. The deco fills would work out considerably more than yours too.

And is right - Breakwater is a good source for gas and do remix prices. I quoted the prices from memory and find that they are actually cheaper than I quoted. A twinset of 18 45 is £28.20 on a remix (43 from empty) see HERE

Two deco gases - well last time I dived I got a 40 of O2 and a 7 of 50 per cent for £20 but I had to top the 50 per cent bottle a bit for the second day so I chucked in another fiver to the calcs to make up for this.

Day 1 - kill the bottom stage, then use 40 bar or so of backgas (plus 40 or so on ascent) leaving you with 150 for day 2.

Day 2 - kill the bottom stage again then swicth to backgas until we hit minimum gas which we set at 100 bar for this dive. As day 2 was closer to 70 metre average the extra gas meant we got the same bottom time as day 1 - 30 minutes on the wreck. When we surfaced after the ascent and air breaks I had 60 bar in the set which is not enough for a remix again.

The O2 bottle did me both days no problem. I have a lowish SAC but not that low and everyone on the boat did the same dives with similar bottom times without issue.

I've dived like this on three trips now. Taking stages is not just about keeping gas costs low though. Logistically it is easier to get a load of stages on and off boats to be filled.

Anyway - sorry for the thread hijack - which is a bit daft really as the one thing I won't argue with is that gas costs in the Oroboros will be a tiny percentage of what I pay to dive OC.

Glad you had fun jason

[Mal Bridgeman]

Originally Posted by Mark Chase

Whats more likely to kill you on a 60m+ dive? running out of gas or a CCR failure.

OOG at 60m without a team who have planned their gas will result in the high percentage you hint at.

However your statement is not supported by experience though. Last year, for example, all UK OC fatalities occured at 30m or less. All fatalities over 30m were on Rebreathers.

Mal

[Janos]

Originally Posted by Mal Bridgeman

However your statement is not supported by experience though. Last year, for example, all UK OC fatalities occured at 30m or less. All fatalities over 30m were on Rebreathers.

Mal,

This statement is meaningless unless you can tell me how many dives occured on OC and CC, above and below 30m.

It's almost as meaningless as saying there have been no fatalities on the Classic KISS.

Janos