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GLOC)
I and several others (total 5) are off to Scapa this year for at least 4 mix dives (the remaining 6 being Nitrox) and we have a couple of options with regards to gas availability. Gas planned for use is 18/45 with 50% deco.
1. Pay for He on the boat at 3p per litre (O2 is 1p per litre)
2. Take enough twinsets with gas in them (we are taking a Transit but that could be converted into a LWB transit!)
3. Take J's/get J's delivered and cascade
4. Take J's/get J's delivered and boost
We used Air products a couple of years ago & picked them up on the island, it woked well for us, although it did involve a trip to Kirkwell to pick the J's up and then another to drop them off at the end (they might deliver to the quayside now). We already have an account so the price was the same as we pay at home.
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If we fill our own tins with He, the skipper doesn't want it done on the boat but the quayside, O2/air tops will be carried out by him.
don't forget to factor time into your plans, you will (presumably) need to haul your twins off & back on again (easier at high tide than low tide!) as well as the time for the actual filling. It would be better if the skipper would allow the J's onboard, as you can use travelling time for filling (but I can understand his/her reluctance if you are removing a potential for profit from them).
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So, here comes the difficult questions. Once I have worked out the litreage (sp?) of gas required, how do I work out how many J's I need to order if we are going to cascade?
I cheat, I allow Simon to work it out for me!
Lawrence Orchard wrote a spreadsheet many years ago, which is still vaild, you can download a copy from here:
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Finally, how much difference does it make if you use a booster (Haskell?) and does anyone know where we can hire one?
For one week it would probably be far more hassle than it's worth. I would be surprised if you saved enough to make it worth while. Don't forget you would also need a means of driving the thing.
cheers,
Paul