Stack questions

[jason]

Couple of questions about stacks for those of you who are experienced in such matters... By way of background, the stack I'm looking at is part of an oil-fired power generating station. It's about 350 feet high and is 30-50 feet wide at the base. Landing area is such that, if anything more than a fat one second delay is possible, it certainly won't be done in the near future.

My questions... First, this thing is one (and seemingly the most promising) of a line of three, and seems to be perpetually in use with lots of what I assume is primarily steam coming from the top. Are stacks hot when in operation? And given that we'll be leaving from a crowsnest maybe 20 feet below the top, should I be concerned about getting soot all over my gear? Or, for that matter, about breathing near the exit point? :P

Second, we've noticed that even in ~15 km/h winds, the air behind the stack (as visualized with the help of a pressure release or something that vents steam once in a while) seems turbulent, with pretty significant rotors as far as 30 feet or more downwind. What's the common wisdom on acceptable winds for a large stack?

Thanks all!

[imported_Tom Aiello]

Sounds almost identical to a set of stacks here. I've always wanted to launch a three way with one jumper off each stack. Ahh, to dream...

>Are stacks hot when in operation?

The outside of the stack is generally not significantly warmer than the surrounding area.

> And given that we'll be leaving from a
>crowsnest maybe 20 feet below the top, should I
>be concerned about getting soot all over my
>gear?

I'd be more concerned with soot on the climb, and then only if the ladder is inside the stack. I'm not sure if you've got an inside (high soot) ladder or an outside (higher bust) ladder.

>Or, for that matter, about breathing near
>the exit point?

I've been on stacks where that was a concern. Generally, it hasn't been an issue. If you bring a standard disposable dust mask (available at a hardware store), that should cover you for the time you'll be on the stack.

>Second, we've noticed that even in ~15 km/h
>winds, the air behind the stack (as visualized
>with the help of a pressure release or something
>that vents steam once in a while) seems
>turbulent, with pretty significant rotors as far
>as 30 feet or more downwind. What's the common
>wisdom on acceptable winds for a large stack?

I'd be more concerned about the landing area than the rotors. I generally exit stacks cross-wind, rather than downwind, to avoid the rotors. If you can't do that (because of the landing area, etc), I'd wait for a no wind day (or at least very light winds). Also, the rotors are greater between the stacks in the set, so if you must jump downwind, be sure you are jumping the last stack in the row (duh--otherwise you'd be looking at striking the next stack).


--Tom Aiello
tbaiello@mac.com