Calculating Air Volume for Boat Stability in Water

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Discussion Overview

The discussion revolves around calculating the air volume needed for pontoons to ensure stability and flotation for a 15' aluminum boat carrying approximately 300 pounds. Participants explore the principles of buoyancy and displacement, particularly in relation to Archimedes' principle.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant seeks assistance in determining the air volume required to float a specific weight, expressing uncertainty about the calculations involved.
  • Another participant states that 1 cubic centimeter of air displaces about 1 gram of water, equating to approximately 62.4 pounds of water displaced by 1 cubic foot of air, noting that the weight of the air itself is negligible.
  • A different participant emphasizes Archimedes' principle, suggesting that to achieve 300 pounds of flotation, one must displace an equivalent weight of water, while also mentioning the negligible weight of air-filled devices compared to heavier materials like wood.
  • One participant advises considering the total weight of the boat when calculating the necessary flotation and suggests oversizing the pontoons by 25%-50% for added stability.
  • The original poster acknowledges the relevance of Archimedes' principle in their considerations.

Areas of Agreement / Disagreement

Participants generally agree on the application of Archimedes' principle and the importance of displacement for flotation. However, there are varying perspectives on the specifics of calculations and considerations for additional weight from the boat itself.

Contextual Notes

Participants do not provide specific numerical calculations or detailed assumptions regarding the dimensions of the pontoons or the exact relationship between air volume and flotation capacity, leaving some aspects of the problem unresolved.

Who May Find This Useful

This discussion may be useful for individuals interested in boat design, stability calculations, and the principles of buoyancy in fluid mechanics.

champ2823
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Being that I have little experience in physics, but have grown a fascination for it, I am hoping you guys can help with a problem. A friend of mine wants to make a few pontoons to make his boat more stable. It's just a smaller 15' aluminum boat that he uses for hooping (catching lobsters).
He wants to know how much air volume he needs to float about 300 pounds. How much weight a specific volume of air will hold in water. What exactly would the equation be to figure that out? I'm guessing it's so simple that I've overanalyzed it. I'm hoping that I've made myself clear enoug.
 
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1 cc of air will displace about 1 gram of water. That works out to about 62.4 pounds of water displaced by 1 cubic foot of air. The weight of the air is negligible. I think that's all you need.
 
All you need is Archimedes principle. That is, the upwards thrust on a submerged object is equal to the weight of water that is displaced. So to provide 300 pounds of floatation you need to displace 300pounds of water (I'm not sure how much that is, I use metric). If you use an air filled device to displace that water, then the weight of the air is negligible. But if you use something heavier (say wood for example), then you need to add the weight of the wood to the weight of the boat.
 
I assume that means the boat will hold 300lb of cargo, so remember to factor in the weight of the boat when doing the calculations. And oversize the pontoons by 25%-50%
 
Ok thanks guys, I was looking at Archimedes principle and figured it had to do with that.
 

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