The Murphy Builders Site

Posted: **Sat Feb 18, 2012 10:38 am**

I hate to keep beating a dead horse but the responses from the list are
soooo helpful and I'm about to spend a bunch of money. Sorry about the
length of the email.

After lots of reading and GREAT advice from the list I think this is what I
would like to try. I would like to use a 22x16 two core double pass
radiator mounted somewhat horizontally, angled up about 30 degrees at the
front. I'll duct air to the bottom of the radiator with the 4x16" inlet
well back from the prop and an expanding duct to slow the air down and
increase the pressure as it arrives at the face of the radiator. The inlet
ducting will be well sealed. On the outlet side there is just no way to
duct the outlet air. There's engine mount bits, water pump, alternator,
etc. in the way. I was thinking I'd leave a big hole on each side of the
cowl, about 8x8", at the top-side of the cowl and sculpt a duct that starts
at those holes and travels back along the sides of the forward fuselage
section with 4x8" exits just forward of the doors. Might look funny, but
with some flame decals around the outlet ducts maybe I can make it look
cool. Hell, I don't care if it looks funny if it works.

That will give me a large area for the air to begin to escape equal to two
times the inlet area, and the exit duct will narrow the exit air down to a
total of 64 square inches, which is equal to the inlet size and will
accellerate the air, hopefully back close to where it was at when it
entered.

I also plan on two 4 inch holes in the nose cowl, as is normal for Lycoming
installations, to direct air to the upper part of the engine to keep the
heads cool and pull heat from around the headers. I'll put an oil cooler up
there somewhere as well. Hopefully, that will also give me good air for the
carb. I wonder if the air moving from the two four-inch inlets will
actually keep some velocity since it has a good path to the exit holes at
the top-sides of the cowl and give me a slight pressure drop?? That would
be neat. Of course if the air from the two 4-inch holes in the front
stagnates in the cowl somehow, that'll give me a pressure rise in the cowl
which would be bad. I was planning on no hole in the bottom of the cowl
except for the exhaust pipes. This would provide the only escape for air at
the top-sides of the cowl.

FYI - The guy at Griffin radiators gave me a rule of thumb for radiator
sizing of 1 square inch per HP. My max power of 425HP would then require
425 square inches of two core radiator. But I think my 22x16" radiator (352
square inches) will be OK since I plan to limit max power to 3 minutes.
Normal max continuous power will be at 75% which would be 319HP. I could
place a limit on max continuous operation at 85% and still be pretty close
to his rule of thumb at 361HP.

Question on the placement of the radiator inlets and outlets. Seems like it
would be good to have the inlets and outlets on the side of the radiator
that is the highest. This would provide a path for air to escape up the
outlet tube. If they were on the low side it seems like air could get
trapped on the high side of the radiator. Make sense?

One thing that might not be good is the placement of the outlets just below
the door windows. With the windows open the air from inside the cowl may
have a way into the cockpit. Normally, this would only be while the
airplane is on the ground. But, of course, if the windows are open perhaps
that mitigates this danger. There's also the engine fire scenario. Flames
licking at the bottom of the cockpit windows. <Shudder>.

I would love to hear opinions! Of course, no one on this list has opinions
do they? Thanks very much in advance for the intelligent, priceless
responses I'm sure to get.

Mike Kimball
N744MK (Just received my Registration from the FAA. I can put my N-numbers
on now! 7 = my lucky number, 44 = my serial number, MK = Mike Kimball) Now
my abbreviated call sign is "For Mike Kimball". Do you think the
controllers will notice I'm saying Kimball instead of Kilo?

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Posted: **Sat Feb 18, 2012 10:38 am**

Mike,

Other things to consider.

Size of hose feeding radiators, and what type. A stock auto hose is an
accident waiting for a place to happen. Also use the right clamps. How many
GPM flow from the water pump. Any idea what the head pressure is in your
system? If you are building a taildragger, do you have a line running back
to your reservoir tank to keep water moving and forming a steam pocket in
the block? Most successful people are running air down to the radiator and
out the bottom. This also keeps oil or radiator leaks from going into the
exhaust/turbo/in-flight fire areas. One of the big mistakes is that they
don't leave enough room behind the radiator. Some people are also going with
cowl flaps to help keep a low pressure zone around the radiator. The
radiator is ducted separately to insure a clean set up. I'll be using two
smaller holes in the cowl (blast tubes) to keep the turbo cool and feed the
intercooler. I'll be mounting the oil cooler next to the radiator. The big
question is how thick the radiator should be. The drag in the cooling system
say to go small, while others say up to 2.5 inches is ok. No one really has
that one figured out yet... The rule of 1 sq inch per hp is a standard rule.
The real world shows that this is the barely getting by in auto installs for
aircraft. It might work great when you have the skis on. I'll have a much
larger radiator.

Most of the people flying water cooled engines have the same take off. Lots
of power, drop the nose to keep the airspeed up to keep air through the
radiator. There may be some places where you can't fly that profile. Loon
Creek in Idaho caught my attention on that point. When you can take off for
a long climb without going hot on oil or water on a hot day, you got it
made.

Looked at a V-8 but seemed to be way heavy, even with aluminum heads and
block. Several guys have built 20bt's (3 rotor Mazda's) that come in wet,
about 10-20 lbs heavier than a 0 540, and produce 285-350 hp.

If you want I can send you the K and M formulas for laying out a system. It
is pretty big.

My 2 cents. US. dsbarno@vbe.com

Barny
MGDQ 20bt SR 103

----- Original Message -----
From: "Mike Kimball" <mkimball@gci.net>
To: "Rebel Builder's List" <rebel-builders@dcsol.com>
Sent: Wednesday, June 08, 2005 4:57 PM
Subject: Super Rebel V8 cooling

I hate to keep beating a dead horse but the responses from the list are
soooo helpful and I'm about to spend a bunch of money. Sorry about the
length of the email.

After lots of reading and GREAT advice from the list I think this is what

I

would like to try. I would like to use a 22x16 two core double pass
radiator mounted somewhat horizontally, angled up about 30 degrees at the
front. I'll duct air to the bottom of the radiator with the 4x16" inlet
well back from the prop and an expanding duct to slow the air down and
increase the pressure as it arrives at the face of the radiator. The

inlet

ducting will be well sealed. On the outlet side there is just no way to
duct the outlet air. There's engine mount bits, water pump, alternator,
etc. in the way. I was thinking I'd leave a big hole on each side of the
cowl, about 8x8", at the top-side of the cowl and sculpt a duct that

starts

at those holes and travels back along the sides of the forward fuselage
section with 4x8" exits just forward of the doors. Might look funny, but
with some flame decals around the outlet ducts maybe I can make it look
cool. Hell, I don't care if it looks funny if it works.

That will give me a large area for the air to begin to escape equal to two
times the inlet area, and the exit duct will narrow the exit air down to a
total of 64 square inches, which is equal to the inlet size and will
accellerate the air, hopefully back close to where it was at when it
entered.

I also plan on two 4 inch holes in the nose cowl, as is normal for

Lycoming

installations, to direct air to the upper part of the engine to keep the
heads cool and pull heat from around the headers. I'll put an oil cooler

up

there somewhere as well. Hopefully, that will also give me good air for

the

carb. I wonder if the air moving from the two four-inch inlets will
actually keep some velocity since it has a good path to the exit holes at
the top-sides of the cowl and give me a slight pressure drop?? That would
be neat. Of course if the air from the two 4-inch holes in the front
stagnates in the cowl somehow, that'll give me a pressure rise in the cowl
which would be bad. I was planning on no hole in the bottom of the cowl
except for the exhaust pipes. This would provide the only escape for air

at

the top-sides of the cowl.

FYI - The guy at Griffin radiators gave me a rule of thumb for radiator
sizing of 1 square inch per HP. My max power of 425HP would then require
425 square inches of two core radiator. But I think my 22x16" radiator

(352

square inches) will be OK since I plan to limit max power to 3 minutes.
Normal max continuous power will be at 75% which would be 319HP. I could
place a limit on max continuous operation at 85% and still be pretty close
to his rule of thumb at 361HP.

Question on the placement of the radiator inlets and outlets. Seems like

it

would be good to have the inlets and outlets on the side of the radiator
that is the highest. This would provide a path for air to escape up the
outlet tube. If they were on the low side it seems like air could get
trapped on the high side of the radiator. Make sense?

One thing that might not be good is the placement of the outlets just

below

the door windows. With the windows open the air from inside the cowl may
have a way into the cockpit. Normally, this would only be while the
airplane is on the ground. But, of course, if the windows are open

perhaps

that mitigates this danger. There's also the engine fire scenario.

Flames

licking at the bottom of the cockpit windows. <Shudder>.

I would love to hear opinions! Of course, no one on this list has

opinions

do they? Thanks very much in advance for the intelligent, priceless
responses I'm sure to get.

Mike Kimball
N744MK (Just received my Registration from the FAA. I can put my

N-numbers

on now! 7 = my lucky number, 44 = my serial number, MK = Mike Kimball)

Now

my abbreviated call sign is "For Mike Kimball". Do you think the
controllers will notice I'm saying Kimball instead of Kilo?

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Posted: **Sat Feb 18, 2012 10:38 am**

Mike Kimball wrote:

I hate to keep beating a dead horse but the responses from the list are
soooo helpful and I'm about to spend a bunch of money. Sorry about the
length of the email.

After lots of reading and GREAT advice from the list I think this is what I
would like to try. I would like to use a 22x16 two core double pass
radiator mounted somewhat horizontally, angled up about 30 degrees at the
front. I'll duct air to the bottom of the radiator with the 4x16" inlet
well back from the prop and an expanding duct to slow the air down and
increase the pressure as it arrives at the face of the radiator. The inlet
ducting will be well sealed. On the outlet side there is just no way to
duct the outlet air. There's engine mount bits, water pump, alternator,
etc. in the way. I was thinking I'd leave a big hole on each side of the
cowl, about 8x8", at the top-side of the cowl and sculpt a duct that starts
at those holes and travels back along the sides of the forward fuselage
section with 4x8" exits just forward of the doors. Might look funny, but
with some flame decals around the outlet ducts maybe I can make it look
cool. Hell, I don't care if it looks funny if it works.

This sounds like it has a high (better than most) chance of success to
me. Generally I think the exit should still be at least 20% larger area
than the intake. (velocity recovery is never perfect due to internal
duct drag). I'd be tempted to make the inlet a little larger for ground
cooling but in fact you are well within what lots of folks have used
successfully.

That will give me a large area for the air to begin to escape equal to two
times the inlet area, and the exit duct will narrow the exit air down to a
total of 64 square inches, which is equal to the inlet size and will
accellerate the air, hopefully back close to where it was at when it
entered.

I'd suggest not narrowing so much. As I understand it, the actual exit
area where the exit ramp terminates in free air should be at least 20%
larger than ALL inlets that exit there. Velocity recovery is never
perfect due to internal duct drag.

I also plan on two 4 inch holes in the nose cowl, as is normal for Lycoming
installations, to direct air to the upper part of the engine to keep the
heads cool and pull heat from around the headers. I'll put an oil cooler up
there somewhere as well. Hopefully, that will also give me good air for the
carb. I wonder if the air moving from the two four-inch inlets will
actually keep some velocity since it has a good path to the exit holes at
the top-sides of the cowl and give me a slight pressure drop?? That would
be neat. Of course if the air from the two 4-inch holes in the front
stagnates in the cowl somehow, that'll give me a pressure rise in the cowl
which would be bad. I was planning on no hole in the bottom of the cowl
except for the exhaust pipes. This would provide the only escape for air at
the top-sides of the cowl.

Yes I found this a tricky decision too. I eventually did keep my
radiator exit air separate from cowl ventilation exit air so that I had
independant control over what was coming out of the radiator. Don't know
if it is worth it but I suppose you could separate the top couple of
inches of your exit ramps so that only cowl ventilation air went out the
top (or bottom) portion. (A horizontal sheet metal divider or baffle
within the exit cowl?). In any event don't forget to add the area of
your 4" round inlets to the rad inlet when calculating the exit area.

FYI - The guy at Griffin radiators gave me a rule of thumb for radiator
sizing of 1 square inch per HP. My max power of 425HP would then require
425 square inches of two core radiator. But I think my 22x16" radiator (352
square inches) will be OK since I plan to limit max power to 3 minutes.
Normal max continuous power will be at 75% which would be 319HP. I could
place a limit on max continuous operation at 85% and still be pretty close
to his rule of thumb at 361HP.

Of course if you have the room a larger rad is not going to cost more
but I'm willing to bet you are already as large as you can fit in
comfortably.

Question on the placement of the radiator inlets and outlets. Seems like it
would be good to have the inlets and outlets on the side of the radiator
that is the highest. This would provide a path for air to escape up the
outlet tube. If they were on the low side it seems like air could get
trapped on the high side of the radiator. Make sense?

Yes I moved the water outlet to the top of the rad water tank to avoid
needing a separate vapour vent line. A LOT of difficulty has been seen
by guys that don't make provision to vent vapour from anywhere that it
can be trapped within the cooling system back up to the high point where
the fill cap is.

One thing that might not be good is the placement of the outlets just below
the door windows. With the windows open the air from inside the cowl may
have a way into the cockpit. Normally, this would only be while the
airplane is on the ground. But, of course, if the windows are open perhaps
that mitigates this danger. There's also the engine fire scenario. Flames
licking at the bottom of the cockpit windows. <Shudder>.

Personally I would lower the side exits to mid cowl or whatever is
convenient. There should be no exhaust gases there anyway but with
normal prop rotation you still don't want the heat to come in the pilot
window on the ground. (OTOH I did add a reverse scoop at the top rear of
my cowl to let hot air out after shutdown though so maybe your approach
is fine)
Flames out the bottom of a Lycoming cowl are going to come through the
aluminum floor pretty darn quick too. I did keep the fuel header tank
out of the cowl so I think the all one can do is shutoff the fuel and
cross your fingers as you dive unless you put in a race car fire
suppression system. Fires are more smoke than flames anyway though we
hope ;(

I would love to hear opinions! Of course, no one on this list has opinions
do they? Thanks very much in advance for the intelligent, priceless
responses I'm sure to get.

Priceless as in not worthy of a price I presume. Or is that worthless?
Very confusing ;)

Mike Kimball
N744MK (Just received my Registration from the FAA. I can put my N-numbers
on now! 7 = my lucky number, 44 = my serial number, MK = Mike Kimball) Now
my abbreviated call sign is "For Mike Kimball". Do you think the
controllers will notice I'm saying Kimball instead of Kilo?

There is a fellow hereabouts that loves it when the current ATIS is
information is Whiskey. His callup is then "This is SEX with Whiskey!

Ken

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Posted: **Sat Feb 18, 2012 10:38 am**

Just a thought. A friend of mine has suggested. Griffin will make radiators to whatever spec we choose. I would love to hear others on the list speak to his suggestion.

Have griffin construct a radiator that has built in both oil and traditional radiator cooling. This keeps the coolant and oil at the same temp. When the system is first fired up, the oil will heat the radiator/Propylene Glycol. Once running they are both maintained at the same temp for more uniform engine temp. This also eleminates the need for additional ducting for an oil cooler. It is not clear to me if you would need a larger radiator/oil cooler. Mike in your converstions with Griffin was this discussed?

Rick Muller
SR70

-------------- Original message --------------

I hate to keep beating a dead horse but the responses from the list are
soooo helpful and I'm about to spend a bunch of money. Sorry about the
length of the email.

After lots of reading and GREAT advice from the list I think this is what I
would like to try. I would like to use a 22x16 two core double pass
radiator mounted somewhat horizontally, angled up about 30 degrees at the
front. I'll duct air to the bottom of the radiator with the 4x16" inlet
well back from the prop and an expanding duct to slow the air down and
increase the pressure as it arrives at the face of the radiator. The inlet
ducting will be well sealed. On the outlet side there is just no way to
duct the outlet air. There's engine mount bits, water pump, alternator,
etc. in the way. I was thinking I'd leave a big hole on each side of the
cowl, about 8x8", at the top-side of the cowl and sculpt a duct that starts
at those holes and travels back along the sides of the forward fuselage
section with 4x8" exits just forward of the doors. Might look funny, but
with some flame decals around the outlet ducts maybe I can make it look
cool. Hell, I don't care if it looks funny if it works.

That will give me a large area for the air to begin to escape equal to two
times the inlet area, and the exit duct will narrow the exit air down to a
total of 64 square inches, which is equal to the inlet size and will
accellerate the air, hopefully back close to where it was at when it
entered.

I also plan on two 4 inch holes in the nose cowl, as is normal for Lycoming
installations, to direct air to the upper part of the engine to keep the
heads cool and pull heat from around the headers. I'll put an oil cooler up
there somewhere as well. Hopefully, that will also give me good air for the
carb. I wonder if the air moving from the two four-inch inlets will
actually keep some velocity since it has a good path to the exit holes at
the top-sides of the cowl and give me a slight pressure drop?? That would
be neat. Of course if the air from the two 4-inch holes in the front
stagnates in the cowl somehow, that'll give me a pressure rise in the cowl
which would be bad. I was planning on no hole in the bottom of the cowl
except for the exhaust pipes. This would provide the only escape for air at
the top-sides of the cowl.

FYI - The guy at Griffin radiators gave me a rule of thumb for radiator
sizing of 1 square inch per HP. My max power of 425HP would then require
425 square inches of two core radiator. But I think my 22x16" radiator (352
square inches) will be OK since I plan to limit max power to 3 minutes.
Normal max continuous power will be at 75% which would be 319HP. I could
place a limit on max continuous operation at 85% and still be pretty close
to his rule of thumb at 361HP.

Question on the placement of the radiator inlets and outlets. Seems like it
would be good to have the inlets and outlets on the side of the radiator
that is the highest. This would provide a path for air to escape up the
outlet tube. If they were on the low side it seems like air could get
trapped on the high side of the radiator. Make sense?

One thing that might not be good is the placement of the outlets just below
the door windows. With the windows open the air from inside the cowl may
have a way into the cockpit. Normally, this would only be while the
airplane is on the ground. But, of course, if the windows are open perhaps
that mitigates this danger. There's also the engine fire scenario. Flames
licking at the bottom of the cockpit windows. .

I would love to hear opinions! Of course, no one on this list has opinions
do they? Thanks very much in advance for the intelligent, priceless
responses I'm sure to get.

Mike Kimball
N744MK (Just received my Registration from the FAA. I can put my N-numbers
on now! 7 = my lucky number, 44 = my serial number, MK = Mike Kimball) Now
my abbreviated call sign is "For Mike Kimball". Do you think the
controllers will notice I'm saying Kimball instead of Kilo?

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Posted: **Sat Feb 18, 2012 10:38 am**

A Modine oil to water heat exchanger that sits on top of the oil filter
between engine and the oil filter will accomplish the same thing and
doesn't require plumbing any oil hoses. These units are used by some
automotive oem engines with turbochargers as well. My 5/8" coolant line
goes through this on its way to my cabin heater. One extra water
connection. Because the water temperature going to the main radiator
will be higher with this, it can make the main radiator actually reject
more heat (more cooling). More cabin heat also becomes available when
needed. The stainless steel versions of these work well despite the
occasional claim otherwise by people who do not understand liquid to
metal heat exchange.

Another (cool) idea is to arrange the cabin heater so that cabin heat
can be dumped overboard to provide supplemental cooling if required.
Especially useful on the ground if you have a fan in the circuit.

Ken

rickhm@comcast.net wrote:

Just a thought. A friend of mine has suggested. Griffin will make radiators to whatever spec we choose. I would love to hear others on the list speak to his suggestion.

Have griffin construct a radiator that has built in both oil and traditional radiator cooling. This keeps the coolant and oil at the same temp. When the system is first fired up, the oil will heat the radiator/Propylene Glycol. Once running they are both maintained at the same temp for more uniform engine temp. This also eleminates the need for additional ducting for an oil cooler. It is not clear to me if you would need a larger radiator/oil cooler. Mike in your converstions with Griffin was this discussed?

Rick Muller
SR70

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