IIRC, Tracy used the thickest version
of the 'Sirocco' radiator for his 20B.
I'm embarrassed to admit that mine hasn't flown yet. But I am
making progress; painting is in progress now. I've already done
all the FWF, wiring, plumbing, etc and previously hung the wings
& tail to do rigging/final drilling, so assembly is what's
left after paint.
If you can get Dennis Haverlah off the tennis court, he can share
some experience with his wedge diffuser on a Renesis/RV7A. His is
under the engine, but diffuser design would be similar.
Here's a link to a flow test I did after building the diffuser.
https://studio.youtube.com/video/D0mUJdzzrG0/comments/inbox?filter=%5B%7B%22name%22%3A%22ENGAGED_STATUS%22%2C%22value%22%3A%22COMMENT_CATEGORY_NOT_ENGAGED%22%7D%5D
I have no idea on how *efficient* the design is, but I do get
equal airflow across the entire face of the core; something that
can be difficult to achieve in a lot of cases. With a round inlet
offset to one edge feeding a large flat exchanger, a turning vane
was essential for me. If you use a rectangular inlet that's as
wide as one face of the exchanger, you shouldn't need a turning
vane.
The non-intuitive thing is how 'tight' the wedge has to be at the
aft edge of the exchanger. Tracy warned me, so I made mine pretty
tight (~3/8" aft end) to start with. He happened to be visiting
about the time I pulled it from the mold, & said that it
didn't look tight enough. Sure enough, when I did a flow test, all
the air was coming out the aft 1/3 of the core. I used spray foam
to tighten up the gap to almost nothing at the aft end, and got
even flow after that. I started out trying to 'do the math' using
the K&W streamline formula to expand from the round inlet to
the bigger rectangle entry to the wedge, but transitioning from
round to rectangular while following the formula before starting
the wedge was...not fun, so I finally just tried to approximate
the expansion, then made a 'TLAR' turning vane to get some air
down to the leading edge corner that is away from the inlet.
The wedge ended up having a curved wall that looks a bit like the
K&W streamline wall in reverse.
Hope that's at least a little help. I can send you a link to my
google cloud account with pics of the diffuser if you'd like.
Charlie
On 11/23/2022 9:09 AM, Les C
lesphoto@hotmail.com wrote:
Thanks Charlie. I love the look of Tracy's set up, and if it
cools adequately, I'd like to pirate it for my plane. How did
your's work out?
Les Criscillo
Nurse, Pilot, Brewmaster, Maker
While doing some research online, I saw same good pictures
of the 20b installation in Tracy's RV-8. I am
particularly interested in the wedge diffuser he used for
his radiator cooling. I've been looking on the mail list,
but don't see anything referencing it or any other
information about the ducting. I have been planning on
using a ventral radiator with a scoop to provide the cooling
I'll need. I'm building a BD-4 and I may have enough room
in my cowling for both the wedge diffuser and cooling for my
oil. Does anyone have thoughts, suggestions or directions?
I've looked for the K&W book, but haven't been able to
find it or any copies of it.
Les Criscillo
Nurse, Pilot, Brewmaster, Maker
Hi Les,
For K&W, go to your local library & ask if they have a
lending agreement with an engineering school in your state; the
school will almost certainly have a copy. That's how I got
access.
If Tracy doesn't see this & reply, I'll try to send you
some info on my attempt to more or less copy his wedge
diffuser.
Charlie