> >  > Mike, my fan is a pull through  on the opposite side of the rad

from

 > >  > the inlet duct and rad plenum.
 > >  > The intake scoop has a volume that is roughly 1/3 the volume of

the

 > >  > rad plenum so I think the air will not be moving that fast.    On

the

 > >  > exit side of the rad,  you have the entire interior volume of the
 > >  > fuselage.     Air entering the scoop at 200 m.p.h. will slow to

66mph

 > >  > at the rad face and then slow even more on the exit side.  While I

am

 > >  > not going to blame anyone else if this does not work,  credit for

the

 > >  > design of my cooling system goes to many members of this group
 > >  > particularly Paul and Bill Freeman who probably don't even

remember

 > >  > the excellent engineering they freely provided while this design

was

 > >  > coming together.    --Jerry

 > I don't think you can count on the volume of the fuselage to make any
 > difference at all. The velocity of the air flowing through the fan is
 > porportional to the volume and inversely porportional to the cross

section

 > area OF THE FAN. If anything, a larger volume behind the fan will tend

to

 > reduce the pressure, which will allow more volume and INCREASE the fan
 > speed.
 >
 > I'm not an engineer, so this is just my intuitive understanding. You
 > engineers out there, please correct me if I am wrong.
 >
 > Dick Gregory

 It will make a difference if the * cross sectional area * of the exit

duct is

 too small. The volume per se has nothing to do with it. I think Jerry is

mis

 using the term volume. I think what he meant to say was he had plenty of
 exit duct area.

 Paul Lamar

OK, but that is still a secondary effect. You want the most air possible to
flow through the radiator during high cooling demands. This means higher
volume through the fan, if it is there. The larger the fan diameter, the
lower the air velocity, and the slower the fan will want to spin.

So you guys have convinced me to try to get the the air to draw from the
exit duct, powered by the prop. I understand that the rule of thumb is to
have an exit area 1/3 to 1/2 of the rad area. How close to the prop should
the opening be, and where should it be vertically in relation to the prop
diameter?

How close is a good question. For a start I would make it as close as possible.
About one half out of the prop radius should be about right. PL

If my ground tests show adequate cooling under power with no airspeed, I
will leave it like that. However if I have ground cooling problems, the fans
go in before the first flight.

I am trying to avoid initial cooling problems by using an adequate if not
overkill system from the start. For example, my rad will have 390 sq in and
I am using the mazda oil cooler. My inlet scoops will start out large and
get trimmed as experience will allow.

I still haven't seen my engine. I guess the truck must have got lost because
it was supposed to be here Thursday. I am calling this afternoon to see if I
can trace it.

Dick Gregory

The AirCraft Rotary Engine NewsLetter.              Powered by Linux.
ACRE NL web site.
http://home.earthlink.net/~rotaryeng/            http://www.linux.org