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If you  were diving in the ocean and you had to move a 2000# rock towards the beach. You had  a bunch of 55 gal. drums,how many would it take?

5

4
with steel drums displacing 9.07 ft3 and weighing 60lbs you get 520 lbs of net lift. 2000/520 = 3.84 drums
with plastic drums displacing 9.42 ft3 and weighing 20 lbs you get 583 lbs of net lift 2000/583 = 3.43 drums
wooden drums typicly only come up to 30 gal. so I ruled out this material

What is the displacement of the 2000# stone?..With this, one can figure out the needs to make it neutrally boyant..what i do not know is your safety margin....This is a public safety question, and even if 4 or 5 barrels will make it lift,  is it the safe way of doing it..what if one of them breaks loose..your rock would drop like a rock. :..my guess is that you would use several extra barrels using them at less that complete capacity..thereby adding in a safety margin

It was A dumb question.  It  displaced 20 cu/ft and it was in 101 feet of water. how  many ATM is that? 55 gal drums will lift a little over 400#. and because its  so deep why don't we make a staged lift.  Here is a wild idea lets do it as a tidal lift also.
grumpie......
PS joe and lisa think out side the box BUT kiss

When you say "Tidal lift"  I take it you want to rig at low tide so that incoming tide raises the rock and takes it in??  The point of it being at 101 ft?  That's just over 3At.  The 55 gal. drums are not like lift bags that have no volume until inflated...They would logically stay at surface and have lines dropped down to attach to a web or rig around the rock.  It's a rock...it's not going to displace more or less water as it is raised?!?!  It cannot be filled with air to displace itself...This has to be one Nice rock for you to want it in your front yard!!!  Goodnight!

displacement of 20cf
weight 2000lbs

20cf x 64. lbs/cf= 1280..existing boyancy
2000-1280=720lbs downward force
720lbs/64.lbs/cf= 11.25cf needed to make neutral
using the calcualtion of 9.0 cf per barrel
im going with 2 barrels..in perfect conditions...but this is not to say that this is the safe answer..this is the mathematical answer...i think the given displacement of the rock may be off though....
What is the SAFE answer?

101 ft sw..3 ATA water pressure , but 4 ATA absolute

I'd  like to say   3  barrels   but before I did that,   the question I would ask   is   

1.  why   do we need to move a rock from a 101 ft. deep in the ocean?
2.  how far will we need to move it?
3.  How are we going to secure it?
4.  Can't we just drop a new rock :

I think the math Dive Capt Dave ..... did is correct.   More is usually safer.  I do also like the idea of a tidal lift.  How are we going to move it closer once we do lift it:?   pulling or towing?

maxfactor

hey grumpie,
any chance you will add closure to this string..just curious
thanks
dean

sorry ..just got your private message
thanks
dean