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Jeff,
It would be a good time to check the
airflow distribution across the face of the radiator with a leaf blower and a
tuft of yarn on a stick as was described by Bobby the other day. Did you
check this prior to adding the dividing vane?
Bill
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net]
Sent: Monday, May 18, 2015 7:54 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Return to
Flight - 2
I spent several hours yesterday working
on the inlet plenum. First the pinch was removed and reprofiled with a
gentle slope. Then I decided to divide the airflow front and back by
adding a divide vane. I simply cut a notch on both sides of the plenum, slipped
in a sheet of aluminum and glassed over the seams. Also added some foam
core on the inside to aid the back half of the core ... see attached
photos. Still have to examine the outlet diffuser (or none) and/or cowl
flap, plus check cowling to see if any inlet area is being wasted.
Jeff
From: Bill Bradburry
[flyrotary@lancaironline.net]
Sent: May 16, 2015 9:18 AM
Subject: RE: [FlyRotary] Re:
Return to Flight - 2
Jeff,
One other thing that I just noticed.
I was looking at your photo to see what you were saying about the oil pan
clearance as regards the pinch and I happened to see that you have a double
pass radiator and the inlet/outlet are on the rear of the radiator. That
means that you can have an air pocket in the forward radiator tank and if large
enough it could also be in the cooling area. There are several ways you
can address this if you can not/don’t want to turn the radiator around,
you can install a bleed hose in the forward tank and take it to the bottom of
your swirl tank. Or just to get the air out after a fill, you could raise
the tail of the plane between runs to let the air rise to the swirl tank.
That might take several tries.
I am putting most of my money on
addressing the pinch.
Bill
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net]
Sent: Saturday, May 16, 2015 7:26
AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Return to
Flight - 2
Thanks for the replies guys; all good
points to consider and I'll try to address your comments.
Yes, I could remove the outlet plenum but the radiator air would now combine
with oil cooler air and pressure inside the cowl, right now it"s isolated.
The right nostril feeds my stock Mazda oil cooler; left nostril feeds a Fluidyne
- having extra oil cooling there is a possibility to scavenge more air
for the radiator.
Yes, the pinch IS a problem and is there mainly because of the oil pan behind
it; also thought the pinch (or downward turning vane) would help the front portion
of core.
I have a manometer that was used on previous setup - just clear plastic tubing
with red food coloring - it's difficult to do 1 step at a time because I'm
using a test pilot - need to make best efforts even it means combining
solutions.
No, I haven't done any flow testing and yes I should.
Back to the drawing board ... will post when more results available.
Thanks again ... Jeff
From: Charlie England
[flyrotary@lancaironline.net]
Sent: May 15, 2015 10:42 PM
Subject: Re: [FlyRotary] Re: Return
to Flight - 2
Hi Jeff,
First, a caution: I'm a long way from flying, so this is untested in flight.
But I did a similar thing to what Bobby said, and used a leaf blower to
pressurize my rad plenum. I used a thread on a stick to check outflow from the rad
core. Looking at the drawing of your wedge plenum, I'd bet that almost all the
air is coming out the last 5 or 8 inches of the core. Before I made mine, I
asked Tracy
about his RV-8 plenum. He said to pinch the back down tight; that he had to
stuff open cell foam in the back of his to even the flow, so I did (I thought).
He happened to be here as I was getting ready to glass the mold, and commented
that it was probably too thick at the rear. (It was *much* tighter than your
drawing shows.) Sure enough, when I checked flow, all the air came through the
rear of the core. To get even flow from front to back, I re-shaped the inside
of the wedge until the last couple of inches almost touch the core.
Also, in order to spread flow across the core (side to side, perpendicular to
the inlet flow), I had to install a turning vane in the inlet duct. For
reference, I'm building an RV-7 with a Sam James cowl made for a Lyc; not the
rotary cowl with a chin inlet for the rad. So my ~4.5" round inlet
transitions to more or less rectangular cross section with slightly increased
area where it arrives at the front edge of the core. Then it's a concave wedge,
pinching down to almost a knife edge at the back end of the core.
No idea if it will actually cool, but I do know that the airflow coming out of
the core is pretty evenly balanced when using the leaf blower to push air
through it.
Pics below. The trailing edge is a lot thinner than it looks, because there's
'filler' on the inside to thin the wedge.
FWIW...
Charlie
http://s1155.photobucket.com/user/rv7charlie/media/1d6b1e19.jpg.html
http://s1155.photobucket.com/user/rv7charlie/media/slobovia12a_zps3194777e.jpg.html
http://s1155.photobucket.com/user/rv7charlie/media/pdrop2012_zpscbc0ae13.jpg.html
http://s1155.photobucket.com/user/rv7charlie/media/4seatback_zps033399e2.jpg.html
http://s1155.photobucket.com/user/rv7charlie/media/Slobovia14_zps413ea84e.jpg.html
On 5/15/2015 2:17 PM, Jeff Whaley wrote:
Actually I
don’t have any really good pictures because I took it apart … but
attached is a side-view after removal of the inlet diffuser on top and also a
sketch of approximate scale and shape of what I tried to make, (I don’t
have a damper plate or cowl flap yet). The top shape isn’t quite
right; needs to be pinched more at the rear, also am considering a turning vane
to direct more air through the front half. Trying to make air bend 90
degrees twice isn’t easy but I chose this orientation because of the
desire to add a damper at the output for winter operations. I could drop
the rear of radiator and bring air in through the bottom, spilling out over the
engine but would lose the ability to have a damper – I don’t like
the idea of inlet dampers. On top of it all, my climb speed is usually
only 90 mph; I don’t have the ability to get extra pressure from
increased airspeed. P.S. the radiator is the Griffin 2-58185-X, same as several other
installs on this list.
The top plenum was
out in the SUV; hopefully more attachments in next post …
Jeff
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Sorry to hear that Jeff. My
apologies if you have already posted pictures of the your installation and
the diffuser, but could you post some now?
Dave Leonard
On Fri, May 15, 2015 at 8:19 AM, Jeff
Whaley <flyrotary@lancaironline.net>
wrote:
|
From: Jeff Whaley
Sent: Friday, May 15, 2015 11:19
AM
To: 'Bobby J. Hughes'
Subject: Return to Flight - 2
Well, the second
flight occurred last night with same results as before; one short low-level
circuit due to insufficient cooling … looks like Al Wick made the correct
prediction.
There are 3 things I
can try with the current configuration: 1) Increase inlet area 2) Increase
outlet area (adjustable cowl flap) 3) Re-profile the pinched diffuser. I
will do all 3 and see what happens.
If all of the above
show remarkable improvement then repositioning the radiator is the only
alternative.
Jeff
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that we may correct our internal records. Please then delete the original
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This message, and the documents attached hereto, is intended only for
the addressee and may contain privileged or confidential information. Any
unauthorized disclosure is strictly prohibited. If you have received this
message in error, please notify us immediately so that we may correct our
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