The Math of Buoyancy

[Eric Roach]

I made a needle recently from a new piece of cherry and added the usual amount of lead to the tail and belly.

I know wood density between pieces can vary, but I was surprised to see the total weight of the finished plug was almost 1/2 oz less than usual. These needles are designed to sink, but this one floated.

Crisis? No. It behaves very similar to what I expect and it took some reluctant fish this morning.

This did make me think about the math of buoyancy...Suppose you have three plug blanks from the same type of wood in exactly equal shape. All have the same volume, but weigh differently because of the differences in density. You know from experience that the plug has the sink rate you like when the finished lure weighs 3.5 oz. If you adjusted the lead weight for each plug blank so the total weight for each equaled 3.5 oz, would you expect the sink rates to be the same?

Thanks for any feedback.

Eric