Monday, September 26, 2011

Which Is Heavier?

I made a comment in response to a post on Chiff & Fipple which suggested the black whistles would be lighter than the white whistles. Jem, who has handled both thought the opposite. So I thought I'd find out. I trimmed a length of both pipes to the length of a C body and went looking for my gram balance to weigh them on. 


Oh darn, that's right, I sold that a year ago. Hmm.... how to fairly compare them? They seem so close, a subjective bounce-in-the-hand approach isn't going to work.  Maybe I could float them and see which floats higher? The OD is so very similar. But the black pipe is just enough smaller that a pair of calipers clamped on the pair holds the black pipe and lets the white slide thru. Just. 


Obviously I need a constant OD thing to float to compare the two. Well, lookie there, a section of PVC pipe. Imagine me having a section of PVC pipe lying around. I taped the bottom closed and floated each test piece in water. 




Darn near the same. The black line, submerged in the photo above, is where the water level of the black pipe fell, and the blue line is the white pipe. For practical purposes they are the same weight. I am going to use the same machining dimensions for the two pipes, so aside from the very minor differences in the weight of the material I will remove, the weight of the two whistles will end up the same for practical purposes. 


So now we know. 


Which brings up a related story. I once owned a kayak that was yellow deck over a yellow hull. When I weighted it, it was four pounds heavier than the factory spec. So I called them and asked if that could possibly mean the boat was holding water in the fiberglass or something. "Hmmm... is the boat yellow by any chance?"  "Well, yes, it is." "That explains it. Yellow boats are heavier than other colors."  "What?" "The yellow gel coat is more translucent than the other colors, and we have to put on a thicker layer to keep the fiberglass from showing through."  


So now you know.