"So sorry to hear about all three of these people."

Linking these two together, this 3rd guy will blame himself for a very long time; that is the nature of such incidents, increasingly as time passes.
The one who survives asks himself how that came to be, and, and ............. it goes on for a long time.
I hope that he continues to ride, all in due course.

+ for any single one of the unfortunate chain of events it can be survived (while those involved don't even realise how close they have got to a non-happy ending) but putting them all together becomes a litany of decisions, chance and choices - "there by the grace of" go all of us.

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Dave

How terrible for them, I was there in May and it was hot then. No way i'd take a big bike on the dunes it's madness.

Above 40C you won't notice if your sweating or not because it evaporates so quickly.
Piss straw colour twice a day, minimum.
Caffeine drinks such as coffee or cola will make your pee clearer so may give a false impression of how dry you are
Don't wait to drink until your thirsty, by then you are already well into a fluid deficit. Drink regularly, your not drinking because your thirsty, your drinking to stay alive.
These guys didn't dehydrate and get heat stroke in 40 minutes, they were already into the advanced stages when their friend went for help. This will have been developing for sometime.Look for the early signs such as headache, lack of concentration and irritability.
Be aware that if you've had a close call with heatstroke, your still at risk of going into organ failure for several days, so stay somewhere you can get help if you need it.
when your working hard, digging out etc, strip down to loose light clothing, then put your stuff back on when you need it. It's a fag but you need to try and stay cool.
If your getting a bit desperate, piss on a rag and wrap it around your neck and/or pack it in your groin to aid cooling (if you can piss!!)
Don't start on a deficit (because you've been out on the lash the night before for example)
Drink plenty when you can, i.e when your at a water source, so you have a good positive balance on board when you start. Once away from the source, don't drink large volumes at once as you'll just piss it back out again, little and often.


That's my advice off the top of my head born of 23 years as an Army medic, and seeing plenty of full blown heatstrokes

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1990 Landcruiser H60. Full rebuild completed 2014