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
Hi, are you talking about AOI ?
Steve Carlisle
No :-)
"Angle of Incidence (or AOI) is the angle between the blade chord line
and the
plane of rotation of the rotor system." ???
I am talking about the panels behind the cockpit relative to the
direction of flight
that are greater than 7 degrees. The Glass Goose is an example.
There are a limited number of single engine sea plane configurations
that minimize drag.
None of them have that configuration.
Lake, Coot and Sea Wind. High mounted engines that allow more or less
perfectly stream lined
fuselages. The High mount is necessary to keep the prop out of the
water spray.
The Coot did not take full advantages of the possibilities. Also the
prop could have been
driven by a longer belt lowering the weight of the engine and moving the
prop higher.
See the attached picture. These airplane have rather bad handling due to the
weight and thrust of the high mounted engines relative to the wing.
More power causes
a nose down moment as does landing in water due to the inertia of the high
mounted heavy engine.
IMHO the Sea wind is the best of the group.
For twins there is more variation. Gull wings are a good one Dornier DO
26, Martin PBM,
and an Italian lite sea plane that I don't remember the name of.
The next category is pylon mounted wings with multiple engines. The PBY
is the best example.
Dorneir D18D is another. These usually have some high drag strut bracing.
BTW if the pilot and passenger are semi reclined the cabin top of the
Glass Goose AKA
Sea Hawker could be lowered and the wing supported with a short pylon
above the cabin top which would benefit the aerodynamics some what.
Then the deep fuselage with wing mounted engines. There is a whole raft
of those including
the Spruce Goose and the Martin Mars. The only feature that causes extra
drag is
the step and the extra deep or high fuselage. As they get bigger this is
less of a problem.
All the older strut mounted high wing sea planes are high drag.
The Dorneir Wal was the best of the group.
Sea planes are a difficult design problem due to the two mediums it must
operate in.
Paul Lamar
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