The RX8 core is a good core to use as are Chrysler Doge pick up
cores. Large frontal area with thin cores. The Dodge core is 20" by
30" and is very very effective in a cross counter flow configuration
on the TTC engine. Two cores back to back.
Let's take the Dodge in a non cross flow config.
20 by 30 is 900 square inches.
We have learned more about this subject since Neil Ungar started
flying and on the time to climb engine. Neil complained about over
cooling. It appears we can reduce the intake area of the wedge
diffuser to 15%, of the frontal area of the core, from the 20%
recommended previously.
In other words 15% of 600 square inches is 90 square inches. The
core is 20 inches wide so the height of the 4.5 inches high and 20
inches wide.
Both Neil and the TTC rads are directly in the prop blast so if that
is not the case then you may note higher water temp when taxiing.
Here is the dodge core on top with the diffuser underneath. Yet
another 3D :-) It is far enough forward to give room for the intake
manifold behind it. This leaves room underneath for and oil cooler.
The exhaust out the back of the cabin may help to attach more air to
the aft sides of the cabin. This is a problem that was addressed by
vortex generators previously (or in addition).
Paul Lamar
Excellent recommendations, thank you! I was thinking of having the
radiators on the top/back (low pressure) of the upper cowling with a
long K&L duct. Your version may be easier. I will play with some
radiator models on the actual engine. The smaller the rad size the
easier it will be to fit. 20x30 will be a challenge.
In this model, it seems that two 20x30x1 counterflow radiators would
give a total volume of 1200ci? Is it correct that we need about
600ci for water cooling and 200ci for oil? If so, I assume that
using cross counterflow rads would each need to be about 1/2 the
Dodge size as long as I have 600ci?
My RX8 has twin oil coolers about 8x10x2. The single RX7 oil cooler
is about the same volume. The latter should fit up front if the
water cooler intake is a little higher.
Has anyone used 3D printing to create their engine cowling?
Scott Gettings
Those volume numbers depend on the thickness of the core. Thinner
core less cubic inches are required as thin cores are far more
efficient for a given volume. Dodge were leading the way with other
manufactures catching on.
This is a cross counter flow rad for a Tango
14" by 24" They are Dodge Neon cores.
Some what more compact at higher cost to make. You also need a
skilled tig welder.
-------------------------------------------------------------------------
Scott,
We should change the standard to square inches of frontal area
because all the recent cores are around 5/8 to 3/4 inch thick
including the RX8. Rad core frontal area is more correlated to
cooling than volume.
600 square inches frontal area for 250 HP single core. 2 x 300
square inches for cross counter flow. Two Neon rads are about that.
Maybe a bit more so they should handle a mild turbo charge.
BTW have you considered a 8" prop extension to help the air stick to
the cabin sides? You can lesson the angel at which they go back. If
you go back at 7 degrees and then cut it off flat that will
implement the Kamm effect. Same as the recent Preuses.
Paul Lamar
Hi Paul, I noticed during my re-search on the Glass Goose that the
Icon A5 also has issues back in the cabin sides. They have also used
vortex generators in that area, on the test planes. The GG has the
lower wing and the landing gear that also adds to the problems.
Steve Steve Carlisle
Yes. It is a result of the side by side seating. That Icon is almost
a scam. Be wary?
With the Glass Goose it would not be that hard to change it to fore
and aft seating and narrow the cabin. That lower wing is necessary to
keep the prop out of the water spray which will destroy it.
Here are a couple of great books on seaplanes. Extensive discussion
of the unique design issues.
Paul Lamar
Correction fore and aft seating.
The Kamm 7 degrees does not work out well both side by side and fore
and aft.
The first 3D is side by side the rest are fore and aft.
Of course to build it fore and aft seating one would have to start
over. Not practical for those already built.
Paul Lamar
IMHO if I were designing a sea plane I would scale something that
worked well like some of the Dornier's like the DO 26. Google it.
Actually the Schneider cup racers found out a long time ago floats
were lower drag than sea planes.
I also think a coot is a better than a glass goose.
Paul Lamar
Hi Paul, I stumbled across this amphibian concept, made in
PlaneMaker, for Xplane. It likely has no turbulence issues, a lot
like the SeaRay amphibian. Applying this parasol wing and aft cabin
mods together with interplane struts would also lift the prop out of
the water, no need to put a prop dam on the empenage.
Inline image 1
Steve Carlisle
Looks like it violates the 7 degree rule.
Paul Lamar
The Rotary Engine free News Letter. Powered by Linux. If you want off
the list PLEASE let me know and I will remove you. ACRE NL web
site.
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Copyright 1998-2016 All world wide rights reserved.
On Aug 13, 2016, at 12:36 PM, Scott Gettings <
sgettings@cfl.rr.com
<
mailto:sgettings@cfl.rr.com wrote:
*Subject:* *Glass Goose Sea Hawker cooling systems.*
The RX8 core is a good core to use as are Chrysler Doge pick up
cores. Large frontal area with thin cores. The Dodge core is 20" by
30" and is very very effective in a cross counter flow configuration
on the TTC engine. Two cores back to back.
Let's take the Dodge in a non cross flow config.
20 by 30 is 900 square inches.
We have learned more about this subject since Neil Ungar started
flying and on the time to climb engine. Neil complained about over
cooling. It appears we can reduce the intake area of the wedge
diffuser to 15%, of the frontal area of the core, from the 20%
recommended previously.
In other words 15% of 600 square inches is 90 square inches. The
core is 20 inches wide so the height of the 4.5 inches high and 20
inches wide.
Both Neil and the TTC rads are directly in the prop blast so if
that is not the case then you may note higher water temp when
taxiing.
Here is the dodge core on top with the diffuser underneath. Yet
another 3D :-) It is far enough forward to give room for the intake
manifold behind it. This leaves room underneath for and oil cooler.
The exhaust out the back of the cabin may help to attach more air to
the aft sides of the cabin. This is a problem that was addressed by
vortex generators previously (or in addition).
Paul Lamar
Excellent recommendations, thank you! I was thinking of having the
radiators on the top/back (low pressure) of the upper cowling with a
long K&L duct. Your version may be easier. I will play with some
radiator models on the actual engine. The smaller the rad size the
easier it will be to fit. 20x30 will be a challenge.
In this model, it seems that two 20x30x1 counterflow radiators
would give a total volume of 1200ci? Is it correct that we need
about 600ci for water cooling and 200ci for oil? If so, I assume
that using cross counterflow rads would each need to be about 1/2
the Dodge size as long as I have 600ci?
My RX8 has twin oil coolers about 8x10x2. The single RX7 oil cooler
is about the same volume. The latter should fit up front if the
water cooler intake is a little higher.
Has anyone used 3D printing to create their engine cowling?
Scott Gettings
Those volume numbers depend on the thickness of the core. Thinner
core less cubic inches are required as thin cores are far more
efficient for a given volume. Dodge were leading the way with other
manufactures catching on.
This is a cross counter flow rad for a Tango
14" by 24" They are Dodge Neon cores.
Some what more compact at higher cost to make. You also need a
skilled tig welder.
-------------------------------------------------------------------------
Scott,
We should change the standard to square inches of frontal area
because all the recent cores are around 5/8 to 3/4 inch thick
including the RX8. Rad core frontal area is more correlated to
cooling than volume.
600 square inches frontal area for 250 HP single core. 2 x 300
square inches for cross counter flow. Two Neon rads are about that.
Maybe a bit more so they should handle a mild turbo charge.
BTW have you considered a 8" prop extension to help the air stick to
the cabin sides? You can lesson the angel at which they go back. If
you go back at 7 degrees and then cut it off flat that will
implement the Kamm effect. Same as the recent Preuses.
Paul Lamar
Hi Paul, I noticed during my re-search on the Glass Goose that the
Icon A5 also has issues back in the cabin sides. They have also used
vortex generators in that area, on the test planes. The GG has the
lower wing and the landing gear that also adds to the problems.
Steve Steve Carlisle
Yes. It is a result of the side by side seating. That Icon is almost
a scam. Be wary?
With the Glass Goose it would not be that hard to change it to fore
and aft seating and narrow the cabin. That lower wing is necessary
to keep the prop out of the water spray which will destroy it.
Here are a couple of great books on seaplanes. Extensive discussion
of the unique design issues.
Paul Lamar
Correction fore and aft seating.
The Kamm 7 degrees does not work out well both side by side and fore
and aft.
The first 3D is side by side the rest are fore and aft.
Of course to build it fore and aft seating one would have to start
over. Not practical for those already built.
Paul Lamar
IMHO if I were designing a sea plane I would scale something that
worked well like some of the Dornier's like the DO 26. Google it.
Actually the Schneider cup racers found out a long time ago floats
were lower drag than sea planes.
I also think a coot is a better than a glass goose.
Paul Lamar
Hi Paul, I stumbled across this amphibian concept, made in
PlaneMaker, for Xplane. It likely has no turbulence issues, a lot
like the SeaRay amphibian. Applying this parasol wing and aft cabin
mods together with interplane struts would also lift the prop out of
the water, no need to put a prop dam on the empenage.
Inline image 1
Steve Carlisle
Looks like it violates the 7 degree rule.
Paul Lamar
I agree, and the 7 -degree rule will be a problem with any
center-pod pusher aircraft. This aircraft is very similar to the GG,
except that the inter-wing distance is much greater than the GG
(which is a known problem partially compensated by increasing the
upper wing AOI by a few degrees.)
I made some more detailed measurements on my GG. The widest point
of the pylon is just ahead of the upper wing leading edge and is
43.5" wide. At the leading edge it is slightly narrower at 42.5".
The walls regress at about 7-10 degrees for about 10", then rapidly
angle in at about 27 degrees to the tip. The total length of the
pylon from the leading edge (LE) to the aft tip is 46".
The current prop position using only Tracy's redrive is 48" from the
LE, or 2" past the tip of the pylon. Most builders add a 6"
extension, which would make the prop hub 8" behind the pylon.
Looking at the pylon structure, it would seem safe to shorten it by
about 10" without affecting the structure. Limiting the wall
regression to 7 degrees would give us about 4" taper on each side,
which altogether would give a flat Kamm area about 37" wide. This
could put the prop from 12" to 18" behind a flat Kamm rear end. The
engine cowling would also have areas that exceed 7 degree taper and
may present a challenge.
I wonder if the lowered overall drag of a Kamm rear end also means
cleaner air for a prop at some certain distance behind the flat
wall? The prop is only 62" so may be easily blanked out. Some
builders have used simple, vertical "turning vanes" just outside the
separated boundary layer, usually mounted in between the upper and
lower wings. Some have used these in addition to the stock VGs. Is
there a practical way to model the airflow at the prop with these
various options (I"m not sure that pressure measurements or tufting
would give the answer for the prop airflow itself).
Regarding the radiators: the distance from the LE to the front
engine pulley is 14". The top of the engine is also 14". A Neon
radiator is actually 16.5x26", so a rad of this size would need to
angle up over the engine just a little to fit, which could be done
by raising the cowling a little. The 26" width would not be a
problem.
Thanks,
Scott Gettings
I adjusted the dimensions here and there and had another idea. I
came up with a new diffuser that would handle three heat exchangers
in box formation.
The rads are 20 by 12. You might find them in a small Honda. The top
rad can be the oil cooler. The water rads are merely in parallel.
Parallel is better in theory but you might have to adjust the flow
in each rad to equalize the inlet temperature..
They are recessed into the cabin top with water pipes coming out
under the spar.
I have another idea to get the air to stick to the pylon sides. A
page out of the SR71 design book :-) More about that later.
Paul Lamar
I'm always intrigued by your ideas!
In the GG, the upper wing leading edge is a major structural element
(also part of the wet wing), so I doubt it could be safely or
practically modified as drawn. However, a pair of smaller oil
coolers might fit on the sides without cutting into the wing, with
the larger water cooler on top, extending back over the engine. I
have seen some motorcycle radiators that are curved, which might
offer some advantages to flat radiators. Most don't advertise their
dimensions.
Looking forward to seeing what you come up with regarding the pylon
airflow. I'll look for some pics for turning vanes.
Scott Gettings
One third oil cooling two third water cooling :-)
Turning vanes in general don't help much. They have skin friction
drag.
Well one could put the whole cooling system underneath the engine.
I'll see what that looks like.
Here it is. This is seven degrees. Could be more moving the rads
closer together.
---------------------------------------------------------- Scott,
what do you think about mounting the rads in the back panel?
This will help the drag problem as it is hard to generate significant
pressure on a panel that is highly porous. At the same time one is
increasing the cooling air flow through the cores.
I went to the Chev dealer and checked out the rad cores for the 98 HP
cheap Chinese Chev Spark. At least I think it is assembled in China
at under $14,000 :-) The parts made for most cars are made in China.
They were 12 to 14 inches high by 22 to 24 inches wide. Very thin of
course. Modern heat exchangers.
I think you will find it difficult to get smaller rads from recent
cars. Apparently all the automotive cooling engineers read my book
:-) The Neon rad was the pioneer I think.
Paul Lamar
Hey Paul. I did more measurements and pictures. I mocked up a 14x26"
radiator, and placed it in several positions. Obviously I could not
put this in the potential Kamm flat area without cutting off the pylon tip.
As the pix show, it isn't feasible to bring a volume of air from the
front of the cowling down under the engine, nor have both the exhaust
and cooling underneath. The support bridge takes up a lot of space.
And the engine is pretty tight in the wing cutout.
However, the air might be able to come in from the sides. If I cut off
the pylon tip a couple of inches after the bridge (supports the rear
engine mounts), the pylon would then have a flat area about 13" wide,
and would be from 12" to 18" from the prop.
Adding new pylon walls at about 7-10 degrees would give a flat Kamm area
for radiators of about 3 feet in total width at the aft end. I'm
thinking the new walls might serve as ducts to bring air from the sides
to one or two radiators in the rear, flat area about 2-3" behind the
bridge. Side ducts might need to be far enough forward that they
obscure the rear windows -- not a critical issue. For the ducts, 15% of
300 sq in would be 45 sq" of duct on each side that would need to out in
the airstream. Maybe 3"x15" or 2" X 23"? This would seem to block the
airflow around the bottom 1/2 of the prop, but would allow for a smaller
cowling that would disturb the upper airflow less.
It would be nice to have a virtual wind tunnel to study the multiple
factors in play!
Scott Gettings
I think trying to bring the air in from the sides would aggravate the
separation of flow
now causing a problem for drag and the prop. The exhaust pipe can be
insulated as well
as the ducts and scoops bringing the air to the rad cores.
The ducts and scoops can go under the wing spar and forward of the
leading edge.
No problem. Gives you room for a stock oil cooler up top.
Putting the rad on top will add to the frontal area and add drag.
The scoops can be faired in nicely without adding frontal area.
There is room to add the side suction feature and bring the sides into
about
12 degrees.
I think it is cool looking. Looks like a bug :-)
Paul Lamar
The Rotary Engine free News Letter. Powered by Linux. If you want off
the list PLEASE let me know and I will remove you. ACRE NL web
site.
http://www.rotaryeng.net You Tube
http://tinyurl.com/beqqxas
Copyright 1998-2016 All world wide rights reserved.
