Al,
I have the Spal 11” medium thickness fan.
970 CFM.
If I understand correctly, your Velocity has no way to
move air through the radiators when sitting on the ground except your
fan…?? True??
Somewhat true. The prop does
create negative pressure behind the cowl which draws air through the radiator
that is in the cowl – I was actually surprised by how much – WAG,
maybe 500 cfm at taxi rpm of about 2000 - 2200.
How well does it cool when you are on the
ground? Are you hot by the time you get to the runway ready for takeoff?
On a 70F day, I can startup, listen to
ATIS, talk to ground, taxi the 2700 ft to run-up area, do the runup checks; and
the temps will be about 170 -175 – no fan. If I get immediate clearance
I proceed to takeoff. If I have to wait, I’ll turn on the aux fan,
and that will keep the temps stable at 1000 -1200 rpm idle, probably indefinitely.
Oil temp will go 10 – 20F higher. My rule of thumb is that if the temps
get to 170-175 while I’m on the ground, I turn on the fan; so on a hot
day that may happen by the time I start the run-up.
Since installing the fan, I have never
shut the engine down while waiting for takeoff clearance. I suspect that
on a 90+ day, with much of an anticipated wait; I’d shutdown – just
off the fuel pump, and sit there. When clearance comes, pump on, touch the
starter and it goes. I know – it makes you nervous; but the thing starts
easily.
Al
Bill B