Message-ID: <19981219064130.25260.qmail@www05.netaddress.usa.net>
Date: Sat, 19 Dec 1998 06:41:30
From: Dan Schaefer <dfschaefer@usa.net>
To: lancair.list@olsusa.com
Subject: water level
Mime-Version: 1.0

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In reference to making the water level tool work just a teensy bit better: 

First, when the water is almost at the same level at both ends of 
the tube, the differential pressure is almost nil - so any resistance 
to free flow will leave a residual error. 

One of the major sources of such resistance is surface tension at 
the air/water/tubing ID interface (with some plastics that the tubing 
is made of, being far worse than others). This effect can be significantly 
reduced by mixing a small amount of detergent (liquid dishwashing 
type works fine) into the water before pouring it into the tube. I've 
also found that adding a bit of food dye to the water as well makes 
it much easier to read.

Also, if you remember your high-school chemistry lab work, the surface 
of the water inside the tube will form a curve with the low part in 
the middle. (This curved surface inside the tube is called the meniscus 
-in case you're interested) and you should use the bottom of the meniscus 
as your measuring level at each end - it provides the most accuracy.

Lastly, get ALL the bubbles out.

By the way, I read somewhere that the ancient Egyptians used a similar 
method to level the foundations of the Pyrimids, so there really isn't 
anything new under the sun - at least in this century.

Cheers, 

Dan Schaefer
N235SP