A different kind of walk

[GPSGuided]

Six kilometres walk and crossing Sydney Harbour, a unique form of ‘bushwalking’. Apparently navigation was primarily by compass.

http://www.smh.com.au/nsw/rod-moore-wal ... 0rh5m.html

[johnw]

I overheard this guy being interviewed on the radio the other morning before he started, but unfortunately only caught the end of it.
Interesting "walk".

[GPSGuided]

Given the terrain, compass alone would have been a challenge. Then again, probably a much cooler warm at this time of the year.

[north-north-west]

Six hours at between six and 15 metres. Would have needed a lot of gas and probably a fair bit of deco. The technical details would be interesting.

[Wollemi]

Six hours at between six and 15 metres. Would have needed a lot of gas and probably a fair bit of deco. The technical details would be interesting.

How long does 'gas' last for? What is 'deco' - Decompression ?

[north-north-west]

Six hours at between six and 15 metres. Would have needed a lot of gas and probably a fair bit of deco. The technical details would be interesting.

How long does 'gas' last for?

It's highly variable, depending on size, fitness, mentality, depth, exertion levels and other factors including experience.

What is 'deco' - Decompression ?

Yes. This will vary depending on the gas used (most shallower dives are done on a peculiar gas mixture called 'air'), the time spent at various depths, safety factors and (sometimes) individual susceptibility. Gas mixtures with a higher partial pressure of O2 than air will shorten the required decompression time, all else being equal, but they present other potential problems.

Using anything other than air for anything other than strictly defined periods at certain depths gets you into the realm of technical diving, which is as complex a wormhole to enter as serious dSLR or medium/large format photography - and possibly even more expensive.

[north-north-west]

Back when I was learning to dive, the average Surface Air Consumption rate for your average adult human undergoing average continuous exercise (ie: finning) was considered to be around one cubic foot per minute. This is the uncompressed volume. In other words, the amount of air (or other gas) in what was then a fairly standard small aluminium cylinder (63 cu ft) would last around one hour at the surface. Half that at 10 metres. In 'bits of trivia you really don't need to know', 63 cu ft is roughly the same amount of air as in a phone booth. If you aren't old enough to remember phone booths I suggest Google.

Some of us, being a little smaller and having taken the trouble to get dive fit and learn ways to move with minimal exertion, use a lot less. My own SAC at the time I started my advanced and professional training was approx .5 cu ft per minute.

[GPSGuided]

I read that air was pumped to the 'walker' from a support boat above. It would be rather impractical to use oxygen tanks for that kind of duration I'd think.

[GBW]

Reminds me of Pat Mullin (Chris Lilley) and her ambition to roll from Perth to Uluru in a dingo proof cage.

[north-north-west]

I read that air was pumped to the 'walker' from a support boat above. It would be rather impractical to use oxygen tanks for that kind of duration I'd think.

Scuba tanks. And according to the article, it was surface supplied, from tanks. At depths of up to 15 metres you'd need some sort of booster pump to overcome the pressure differential. I'm assuming it was air or a mild Nitrox mix. Not pure O2 which is solely for use in rebreathers or very shallow stages of decompression.

As I initially said, the technical details would be very interesting, for those of us into technical diving stuff.

[GPSGuided]

Would there be something special? I understand that ‘surface supplied diving’ is pretty standard for professional divers on industrial jobs with diving helmets. Assume it’ll be the same setup. Yes, would be interesting to know his exact setup. Interested in a walk under one of the many Tassie lakes?

[north-north-west]

Commercial diving with helmets is surface supplied by compressor, not from tanks. Very different set-up.
Yeah, you would need a little specialised gear to work this. At fifteen metres you have two and a half times ambient pressure compared to sea-level. No standard scuba regulator will cope with that sort of pressure differential between the first and second stages. I think the limit for this sort of thing with standard gear and an extra long hose is around six metres.

The choice of gas is simply about reducing decompression times. A mild Nitrox mix will give longer without requiring deco, but there are limits with depth ranges depending on the amount of O2 added.

Plenty of inland sites in Tassie I'd like to explore. Caves mostly, although cave diving here is very different to most of what I did on the mainland. Diving leeawuleena would be grouse too, although the viz would suck.
Place I'd most like to dive is Port Davey. There's a big marine reserve there with some fascinating ecology, and sometimes rather awkward conditions. Be really interesting.

[GPSGuided]

Ummm... It's definitely one of those 'come prepared' activities.

Watching the recent BBC series The Blue Planet II recently and the under water world of Earth certainly has a lot to offer for those who are curious of nature. Tassie sounded like as good a place to start as the next.

[Lord Backcountry]

An intereting bushwalk alright!

I put the dive profile through V-Planner, a basic scuba planning tool.

Assuming 10 metre aveerage depth, 300 minutes underwater (the maximum time enabled), and 21% air gives zero deco required.

If I'm careful, I can get 80 minutes out of a standard 12.2 litre scuba (filled to 232 bar) tank on a very gentle dive at 10 metres. I've dived out to the wreck of the Currajong in Sydney Harbour and the bottom is pretty foul, sticky and muddy. Walking would be pretty hard work so I would double air consumption giving a need for 9 tanks. I can count 7, so he may have filled his tanks to above 232 bar.

Great adventure!

cheers

LBC

[GPSGuided]

With your prompt, took another look at the photo in the article. Interesting that he is carrying a tank as well being tethered with a supply line. Assume the tank on his back is for emergency use. A rather simple dingy as the support vessel.

[north-north-west]

An intereting bushwalk alright!

I put the dive profile through V-Planner, a basic scuba planning tool.

Assuming 10 metre average depth, 300 minutes underwater (the maximum time enabled), and 21% air gives zero deco required.

If I'm careful, I can get 80 minutes out of a standard 12.2 litre scuba (filled to 232 bar) tank on a very gentle dive at 10 metres. I've dived out to the wreck of the Currajong in Sydney Harbour and the bottom is pretty foul, sticky and muddy. Walking would be pretty hard work so I would double air consumption giving a need for 9 tanks. I can count 7, so he may have filled his tanks to above 232 bar.

Great adventure!

Deco is about more than average depth. Bouncing up and down between six and 15 metres adds to the issues, as does the extra exertion of trying to walk through all that muck. He'd also need extra weight around the ankles to keep upright enough to walk, which adds to the exertion levels. Plus he was underwater for six hours, which is 360 minutes.

I'd like to see the actual dive profile and know a bit more about the equipment.

(I'm going to be nice enough not to go all pedantic about '21% air' when you obviously mean 21% O2. )

[GPSGuided]

It was not his first time 'walking'. Shouldn't be too hard to get into contact with they guy.

http://www.theherald.com.au/story/49709 ... -the-kids/