|
What is roster tail drag? how and where does it get
created? Is there anything about that written up on the
net?I'd like to know since I'm in the
process of figuring out where to put my radiators in the Long
EZ.ThanksMarko
Marko,
Think of rooster tail drag as drag that's created when air leaves the cowl at
steep angle. The air, instead of turning and moving along the side of the cowl
like you'd think it would, shoots straight out from the cowl for a small
distance [ 6" may seem small but it will create a huge drag penalty!]
Another way to think of it is when your driving and you throw that apple core
out the window, notice how it goes straight out for a little bit and then the
on-coming air slows it down and it 'appears' to go back.. Air leaving the cowl
of your plane will follow basically the same sort of path. So if we smooth this
exit we'll find that we reduce drag. Its one of the reasons that NACA ducts are
soooo popular, they create a very smooth exit [ the air is coming out
parallel to the side of the cowl and then as the duct narrows it is
accelerated and gradually pushed out into the normal airstream. So simple yet it
took years to understand it all.
My 2
cents
Jarrett Johnson
|