----- Original Message -----
From: "Peter Cowan" <cowcam@pipcom.com>

> .Tracy and others, what is the theory behind so much liquid in the
external
> expansion tank? Thermal expansion of the initial coolant volume doesn't
> account for such a large overflow. So is vapor building up inside? If it
is
> there is no longer a liquid filled system. I don't get it.
> Peter

I'm not 100% sure what is going on but I think you would be surprised how
much the 50-50 coolant expands with heat.  I flight tested the new bottle
yesterday and verified that on cooldown the system was completely topped off
with coolant (no air at top of fill port.) This was never the case before.

This also accounts for another anomaly I've noticed over the years.   It
seemed like the water cooling was slightly better on the first flight after
topping off the system.  I was never sure because the next flight was
usually on a different day, different temperature, humidity, etc.  Now that
I've been paying close attention I have verified that only a few ounces
worth of air in the system makes a noticible degredation in cooling
performance  (about 5 degrees worth).   Not sure why this is happening
either but I'm happy with the results.  With more experimentation the answer
will probably come out.

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com