No the Caravan test was a simple wedged shaped duct. The K&W
duct has
a few
problems for our use. Number one is; it is only valid for rads
mounted
perpendicular to the axis of the duct. This means any tilting
of the rad becomes highly configuration sensitive and extensive
development would be required to insure uniform air flow through
the core. You could spend months with a test rig optimizing the
exact shape of the duct. Velocity taps should be used all
over the back side of the rad to insure uniform air flow.
The second major problem is the K&W is too long. In your case
it would be half the length of the fuse :)
BTW Those are real big problems with rads mounted on either
side of the PSRU in a tractor configuration. Thick or thin they
both have the same problems. Nobody is doing their homework on
this.
Paul Lamar
Joseph M Berki wrote:
Paul,
I will look and see if the wedge inlet is doable. I
will get
those dimensions for you also. If I tilt the tray horizontal and
the wedge
shape/scoop hangs down what is the dimension of the back side
diffuser? What does the wedge inlet look like from the
front/back?
I don't understand the first question.
Inlet area is 25% to 30% of the core area.
Can the scoop opening be smaller than the width of the radiator?
Yes but the inlet duct cross sections should be constant area up
to where
the wedge starts.
Does it need a large area/volume like the K&W?
No. One of the wedges advantages.
That is one of the reasons I tilted it so
a plenum could be built on the back side of the firewall
occupying the
space between the firewall and engine. I have some ideas for the
augmenter
(incorporate the muffler into the augmenter) but there are som
NACA
reports
I would like to look at but I think they will not be of much
help.
Joe
Joseph Berki wrote:
Paul,
The distance between the fuselage floor and the bottom of
the spar
at the aft landing gear bulkhead is 12.75" , at the firewall it is
11.5". I looked at the possibility of laying the radiator down
parallel to
the fuselage floor and let the wedge hang down into the air
stream. The
limiting factors were the lower motor mount hard points Clearance
for an
opening for cooling could be 16" max. The biggest radiator would
be 10" X
24" which would mean it would have to be 3" thick. I found a NACA
paper on
rectangular augmenters which would fit with the wedge in that
everything
could be rectangular but I don't think it would exit the air frame
correctly.
Joe
A sixteen inch wide opening would be OK but it must be about 4 or 5
inches
deep.
Does the structure look like this Long Ez? That does not give you
much room under the landing gear for an inlet duct. Do you want to
locate the inlet duct up and over the landing gear beam?
I think the biggest problem with this idea is the loss of
structural strength in the fuselage and the landing gear if you move
the inlet and inlet duct forward and above the landing gear.
BTW If I decided to design a canard airplane I would fasten the
landing gear to the spar anyway. Burt made a few structural
mistakes here and there. Particularly those silly aluminum angle
motor mount stringers only ten inches apart. Might be OK for
a Volkswagen engine. I digress.
Getting the back of the rad clear from obstructions is the next
problem.
How far is the engine from the firewall?
If the air is flowing through the rad properly a 500 cubic inch core
should work fine. That means only 2 inches thick. A 3 inch core
would
give a volume of 720 cubic inches. The back half of the 3" thickness
would be doing only 1/4 of the work so assuming you could get the
air to
flow through the 3" core it would be much less efficient and only
cool
a little bit better.
Why not move the augmentor aft under the psru?
That would give plenty of room under the engine for the rad.
Do you have a sketch of what you have in mind for the augmentor?
Paul Lamar
Joseph M Berki wrote:
Paul,
It is 10 3/8" from the Eshaft front bolt head to the
firewall. My
EZ is not like a long but mounts the main gear between two bulkheads
that
meet the main spar. The aft LG bulkhead meets it at the front while
the
forward LG bulkhead goes up about 4 to 5" and is tilted back and
meets the
spar about 1" up the front lower edge of the spar. This transmits
the LG
loads to the spar. The Cozy MkIV is like this and Rutan did this in
the
Defiant. I can make a 16" wide opening that will start at the aft LG
bulkhead and end at the firewall this permits movement of the rad/oil
cooler to this point. Here there is 12.75" from the fuselage floor
to the
spar bottom. The 12 X 24 radiator is now 10 X 24 if I use a 16"
opening. Farther up in the "hell hole" it is 18". There is no need
to go
above the gear. The augmenter will move back. It is a tube within
a tube
with air flowing around the outer tube and through the inner one.
The
space between the tubes is divided into two sections and is fed from
each
rotor. The exhaust travels around this space, not unlike the
tangential
muffler, and is discharged into the inner tube at an angle facing
rearward. I have no idea if this would work but it looked like a
solution.
OK I got it!! This picture did it for me.
Do away with those silly box sections and sections of the
fuselage that mount the lower motor mount tubes. Make steel
brackets that
picks up the landing gear bolts and fasten the tubes directly
directly to the landing
gear bolts. That is where the high G engine loads ultimately go
anyway.
That will allow a wider and shorter rad, giving more room above the
rad for clearance and solve a whole lot of pusher cooling problems
not to mention doing away with some heavy redundant structure.
Mount the rad horizontal like before. this should work on every pusher
ever built. You can add a structural bulkhead from the bottom aft
edge of the spar forward to just above the landing gear bolts if you
wish.
I'll do a 3D.
Paul Lamar
Here it is.
Looks like you can use a 16 by 19 by 2 inch rad and still get the
oil cooler along side. Nice and clean and simple.
Paul Lamar
It is indeed nice, clean and simple. The creative process seems to go
from complexity to simplicity. You will loose some of the available
radiator space to the louver frame. It makes the radiator about 1.5
inches wider. Jerry
Thanks Jerry. In my not so humble opinion it was a stroke of structural genius
given all the people that have redesigned Burt's original effort.
I just followed the load path.
Only 1.5 inches? I think it is more like three or four inches.
The pushers have been a pain in the butt to squeeze an adequate
size rad in up to now :) Perry's water rad works well because that big
fan sucks the air through like gangbusters.
Paul Lamar
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