Quote:
Originally Posted by deniseO30
to figure out how much floatation (for example)a barrel would have.. is it something like the gallons it holds? The weight of a gal of water is about 9 lbs. so a 30 gal barrel would displace 30 gals of water X 9? = 270 lbs? I'm sure I'm wrong but it seems logical enough. ...

That's pretty much exactly it, you're not wrong at all. The bouyancy of a given volume is exactly equal to the volume of water it displaces. The volume measurement can be taken in any convenient unit of measure, be it gallons, liters, cubic feet, or steres (cubic meters). It all depends on what's convenient. If you had a 55 gallon drum, and assumed 8.5 pounds per gallon (actually it's closer to 8.3, but 8.5 makes the math easier) then you'd be pretty much right on the money at 467.5 pounds of displacement. That is, an empty 55 gallon drum will displace about 460 pounds less the weight of the drum itself and even the polyethylene drums weigh 10 pounds or so. It would be safe to assume you get approximately 450 pounds of displacement per drum. So, theoretically, to lift a 3500 pound boat you'd need 8 drums. Of course, as previous posters indicate, finding attachments and restraints for 3500 pounds of displacement isn't always easy.