Fred Klein wrote:
> Frans...this sounds really interesting...cheers for getting rid of the
> dog house...how bout some photos?
I guess more people are interested in seeing some preliminary work that
has been done.
Note that a lot of work still needs to be done. It is a sort of
"concept" that is ready now.
The idea is to reduce drag, and improve cooling at the same time.
Picture 1: the nasa-ducts in the top cowling. Inside is a deflector
screen. The air is aimed between the front and read cylinders, cooling
both efficiently and equally. The air is directed to the bottom, so the
heated air will hopefully not collect in the top cowling. The air
outlets (inlets?) on the side are closed off. If the engine is shut off,
the remaining heat will find its way out via the nasa ducts which are
actually higher than the side vents.
Note that the front openings will be used for taxi & landing lights, and
not as an air passage.
Picture 2: the cooling inlet and diffuser for the radiators. The idea is
here that the frontal area is reduced, the air inlet is in a better
position in the propellor wash (important for cooling on the ground!),
and drag is lowered because of the diffuser in front of the radiators.
The area where the original air duct was, has been filled with blue
foam, and then sanded until it had the shape the cowling should have. A
few layers of bid (inside and outside) to make it strong. Some (a lot?)
of filler is required to finalize it. The diffuser is also made from
blue foam, shaped, and with two layers of bid.
Picture 3: closeup of the diffuser. The area inside is funnel shaped
with a round curve, but that is hard to see. Every wall of the diffuser
can be seen as a wing. The air going inside is slowed down by expansion,
to match with the airflow the radiators can handle.
Picture 4: Underside/rearside of the radiator housing.
What you are seeing here are actually two air outlets: The opening for
the radiators is obvious. Directly behind it (towards the camera) is the
opening from the engine bay. Both radiators are in line with each other:
the oil radiator will only get air that has gone through the water
radiator. I believe that this is a good thing. (The reason that this is
sometimes done differently in the Europa is because of the bad
properties of the original cooling duct).
On the bottom panel you can see a hinge. Here will be attached an
adjustable cowl flap. In the cruise position, it will be in a direct
line with the bottom panel of the radiator housing. It will extend
considerably rearward, where the belly slopes down. The outgoing air
will be speed up, and hopefully smootlly mix with the air passing the
radiator housing because it has the same speed and direction. If more
cooling is required, the flap will move down, making a greater opening,
and causing some vacuum behind the flap to help the air out. Obviously,
in maximum cooling position it will create some drag, although it
wouldn't be worse than the factory cowling.
Note that the sides of the radiator housing will not be visible when the
cowling is finished, as it will overlap the sides of the radiator
housing. (Problem here of course is that the radiator housing is fixed
to the fuselage, while the bottom cowling needs to be removable. Am not
sure yet where exactly the seam will be made).
Picture 6: Here the shape is better to see. If the cowl flap is in
place, it will be in a direct line with the radiator housing, horizontal
with the flight direction. Because the belly of the cowling slopes down,
the air going to the exit will be compressed (read: "speed up") somewhat.
The complete air path is as follows: There is a small opening in front,
and behind the opening is a diffuser which has "wing-shaped" walls that
increase the area, thus slowing the air down. The slower moving air can
pass the radiators, and after that the air is speed up again, so when
the air is released, it has the same direction and speed as the
surrounding air.
Of course, al this is theory. Because the cooling properties of the
factory cowling are so bad, I believe that it would actually be
difficult to make it worse. So chances are that my cooling at least
gives some better cooling and aerodynamics.
Note that before I started with the Europa I had no experience at all
with making shapes and working with epoxy. I'm sure that a lot of people
can do a better job than I did, and I'm not really sure how things will
look after applying filler and sanding. I hope it is going to be ok.
Comments are welcome of course!
--
Frans Veldman
|