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Re: ?Sink rates/water temp. changes.
- Subject: Re: ?Sink rates/water temp. changes.
- Date: Fri, 02 Dec 2005 13:02:02 -0500
Gordy, thank you for the most elegant and scientific confirmation of my
meatball physics explanation of the same subject!
Bruce
Scientific Anglers/3M
4100 James Savage Rd.
Midland, MI 48642 USA
Tel: 989-496-1113
Fax: 989-496-3374
"Gordon Hill"
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Subject
?Sink rates/water temp. changes.
Rick:
Pursuant our conversation last night and with specific reference to your
question as to whether a sinking line sinks at a faster or slower rate as
water temperature decreases, I have done some research.
I took two tall glasses; filled one with water at 200degrees F., and the
other with water at 34 degrees F.
In each, I dropped equal 1" segments of the same class IV fly lines.
Then I did the same thing with equal 1" segments of an Intermediate fly
line.
The class IV segments each settled so fast that I, frankly, couldn't tell
if there was any difference in the sink rates.
I got the impression, after doing this many times, that the Intermediate
segments were very slightly different, the ones sunk in the 200 degree
water having a sink rate very slightly greater (faster) than the ones in
cold water. THE DIFFERENCE WAS SO SLIGHT, HOWEVER, THAT IT WAS HARD TO BE
SURE OF THIS.
I, then, accessed some information from the U.S. Hydrographic Office as
well as an article from the physics literature: THERMODYNAMICS: AN
ENGINEERING APPROACH..... by Yunas A Cengal, (U. of Utah) and Michael
Boles, (North Carolina State U.). Information gained was as folows:-
1.) Gravitational acceleration is 9.807 m/s squared at sea level. It
varies by LESS THAN 1% DOWN TO 30,000 meters. SO...this can be assumed to
remain a constant at 9.81 meters per second. This means that: THE SINK
RATE OF OUR FLY LINE DOES NOT CHANGE PERCEPTABLY WITH CHANGES IN ITS DEPTH.
2.) Liquids (including water) are incompressible, so have densities that
have negligible variation with pressure. (Density defined as mass per unit
volume.) Translation: CHANGES IN PRESSURE (SUCH AS ATMOSPHERIC PRESSURE)
YIELD NO CHANGE IN WATER DENSITY, THEREFORE PRODUCE NO CHANGE IN THE SINK
RATE OF THIS FLY LINE.
(I mentioned the above, because salt water fishermen are keenly aware that
changes in atmospheric pressure have a significant effect on tidal flows
and water depth in tidal areas. as well as the distinct impression that
game fish respond to changes in atmospheric pressure )
3.) Fresh water at 4 degrees C has a density of 1000 Kg/ sq. Meter. This
density DECREASES as water temperature increases. One "anomalie", is that
the reverse is true beween 0 C and 4 C, where the water density actually
increases as we go from 0 degrees C to 4 degrees C !!!!!
The measurements were: Density of freshwater increased from 999.85 Kg/M
squared at 0 degrees C to 999.98 Kg/M squared at 0.4 degrees C.......THEN
DECREASED TO 999.50 Kg / M SQUARED AT 12.0 DEGREES C !
4.) Now, the sink rate of an object in fresh water is proportional to the
difference in density between that of the object and that of the water.
Or: A MORE DENSE OBJECT (SUCH AS A SINKING FLY LINE) WILL SINK FASTER IF IT
MORE DENSE.
5.) Since the density of water of 4 degrees C decreases as the water
temperature increases, and the converse is also true (the density of the
water increases as the water temperature decreases....down to 4 degrees C),
and since objects sink faster in water less dense and more slowly in denser
water, it holds that: IN WATER BELOW 4 DEGREES C, OUR SINKING FLY LINE
WILL SINK MORE SLOWLY IN COLDER WATER AND MORE QUICKLY IN WARMER WATER. (A
PARADOX IS THAT THE REVERSE IS TRUE IN WATER BETWEEN 0 DEGREES C AND 4
DEGREES C.)
CONCLUSIONS I. Having said all this, the figures indicate that for
practical purposes, these differences are so slight as to escape our
actually being able to detect them.....so are of theoretical value, only.
II. What Bruce Richards told you is correct !
Advice to Masters candidates: Do NOT give a long answer like this on your
exam ! Keep it short and simple.
Gordy