So, I’m sitting here watching one of my favorite MST3K experiments: Mitchell!
In it, there’s a police helicopter equipped with pontoons for water landings. My question: is there a formula to calculate the size pontoon need to float a certain object?
astro
July 14, 2002, 7:01pm
2
Here
Small part of above cited article about density and bouyancy quoted below.
I need a formula to calculate the following. Given a series of sealed tubes of known diameter and length, how can I determine the amount of weight they would support individually and collectively in water (i.e. for a dive float in a lake at camp)?
This is similar to several previous questions posted in this topic. Check above.
To start with you need to know the volume of the tubes. If these are cylinders the formula for their volume is
V = l * pi * r2
Volume equals length times pi times the radius of the end of the cylinder squared. Let’s say that the end of cylinder is 16 centimeters in diameter and it is 100 cm long. The radius is 8 cm, so using 3.14 as an approximation of pi we get
Volume = 100 * 3.14 * 82 = 100 * 3.14 * 64 = 20,096 cubic centimeters. This is just over 20 liters. (One liter = 1,000 cubic centimeters.)
According to Archimedes, an object will support weight equal to the weight of the amount of water it displaces. One cubic centimeter of water weights about one gram. In our example, if the tube were fully submerged it would displace 20,096 grams or 20.096 kilograms of water, which is the weight it would support.
Now there are some details: The diameter and length need to be measured on the inside of the tube. If the walls are thin compared to the size of the tube, this won’t be significant. Part of the weight that the tube is supporting is the weight of the tube itself. We’re not experts on building floats, and there are no doubt many important details to take into account in order to build a sturdy and safe float. You should definitely check with people who know about these things before going ahead with the project.
Weight of object W.
Find volume of water which equals weight W.
Calculate cylindrical object which will hold that volume, more or less.
Note that this object will sink because of the weight of cylinder+air in cylinder. Double volume: easiest accomplished by adding second cylinder on other side
Viola!
Y’now, it isn’t the quantity so much as the quality. I knew this girl in Da Nang who could…
Oh, sorry, I thought we were talking about poontang.