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  #11  
Old June 2nd 08, 12:45 AM posted to rec.aviation.piloting
Bertie the Bunyip[_24_]
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Posts: 2,969
Default Ram air

Tina wrote in news:7b4d9502-9229-4724-9b25-
:

The m20J is pretty slippery already and when it was introduced in the
70s was a big step up in efficiency in a production airplane.
Homebuilts do do an even better job of cleaning up aerodynamically.


Yeah, I've flown a good few 201s and 231s. Mostly the latter. They do
exactly as advertised!

The little seals on the flaps and so on were lipstick, the real gain
over the Mooney Executive had to do with the 201 getting a more
aerodynamic windscreen and engine cowling.


Well, I was talking about aftermarket stuff. There's lots for Mooneys,
but maybe they're all for the early airplanes. Havign said that, on a
relatively small engined but clean airplane, a small improvement in drag
reduction pays large dividends in efficiency. Not only that, they;re
cumulative, so if you make an improvement in one area, it's benefits are
compounded by one in another.


I think using ram air would not increase aerodynamic drag, B. Instead
of having the air moving at the airplane's airspeed plus prop induced
speed impacting the cowling, it could in fact be going into a hole.
It's only a 360 cubic inch engine turning at 2300 RPM or so. Isn't
that a demand of, let's see, at 23 inches mp at sea level that's
23/30 * 2300/2 * 360 / 12^3 or 180 cubic feet a minute?


Well, it's more than likely that Mooney saw a little opportunity to add
that feature when they were analising the flow around the inlet area and
saw a bit of wasted air they could put to good use. they don't like
waste, those guys.
Al's designs were almost all masterpieces. My own favorite is the
Alexander Eaglerock which was his first. A startlingly efficient design
for it's day and my favorite machine of the period. The Bullet was just
unreal, though. Someone's got one flying now. What i wouldn't give to
fly it! Of course, the final design was far removed from Al's original
anyway, so I guess it can't really join the long list of his beauties...

Bertie
  #12  
Old June 2nd 08, 12:47 AM posted to rec.aviation.piloting
Bertie the Bunyip[_24_]
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Posts: 2,969
Default Ram air

"Ken S. Tucker" wrote in news:94016f66-e3ab-
:

On Jun 1, 11:48 am, wrote:
On Jun 1, 4:35 am, Tina wrote:



The Mooney 201 has a ram air port, a half a foot under the prop
spinner. The POH tells us it can be opened at altitude for a very
modest increase in MP and we find maybe a half inch increase in
pressure. The idea of the thing is, if the port is looking right at
the air being thrust toward it by the prop (it can't be more than 6
inches or so behind it) as well as the air impact from the

airplane's
motion the air being 'rammed' into it should effectively lower the
altitude the engine thinks it's at. Well, a half inch of Hg is

about
500 feet or so. The question is, though, wouldn't you think there
would be a way to capture a great deal more of the ram air effect

and
really boost the engine performance? Who wouldn't like to fly at 24
square at 12000 feet without a turbo charger?


What makes me wonder about it is, even at 60 mph holding your hand

out
of the window of a car subjects it to a significant backward

pressure,
so the energy must be there.


The energy is there but it's no bigger than what Mooney claims.
Flat-plate drag at 100 knots is 29 pounds; dicide that by 144 square
inches and get around 0.2 psi, or about 0.4" Hg. Not much. AT 200
knots it will be four times that, which still isn't a lot.
In the 1970's Ford sold some cars with "Ram-Air Induction"
systems. A scoop mounted on the carb that stuck out above the hood,

to
ram vast volumes of air into the carb and get way more horsepower.
That's what they wanted you to believe. At 60 mph the pressure
recovery would have been laughably tiny, but Ford's profits were
impressive.


That was the good old days!
A jig saw and some sheet metal BLASTED your 427 cube
inch engine to over 600 hp!!!, and at 400-500 mph, you'd be
economizing on fuel to boot!.
Ken


And another happy ford customer.




Bertie
  #14  
Old June 2nd 08, 03:59 AM posted to rec.aviation.piloting
[email protected]
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Posts: 1,130
Default Ram air

On Jun 1, 8:06 pm, Gezellig wrote:
It happens that formulated :

In the 1970's Ford sold some cars with "Ram-Air Induction"
systems. A scoop mounted on the carb that stuck out above the hood, to
ram vast volumes of air into the carb and get way more horsepower.
That's what they wanted you to believe. At 60 mph the pressure
recovery would have been laughably tiny, but Ford's profits were
impressive.


Had a Trans Am, scoop was reversed, facing the windshield, had a flap
that opened when MP increased. They claimd that the reversed position
was at the low pressure point at the base of the windshield hence
enhancing the rammed air effect. I don't know, it was cool, the scoop
assembly was attached to the engine so that on acceleration you could
see the engine sitting down on its mounts as the scopp popped open and
lowere ever so slightly.


Locating the scoop at the low-pressure point wouldn't do much
for ram-air effect, would it? I think the real idea would have been to
make sure the driver heard that thing sucking loudly so it sounded
like a real powerhouse
I once converted a 14 foot outboard runabout to a 13 foot
inboard Cracker Box with a Chev 283 straight-shaft setup. The exhausts
were water-cooled and exited through the transom. Made so much noise
that I made two mufflers and quieted it right down. The carb's flame
arrestor stuck up far enough that I had a scoop on the deck, facing
away from the cockpit (which was at the back). Everything else was
covered. I dropped my Dad off on a gravel bar on a lake once, so he
could fish off it while I ran to the far end of the lake to try the
fishing there, three or four miles away. He told me he knew when I was
coming back; he could hear that Rochester Quadrajet four-barrel open
up and suck vast quantities of air; the boat got one mile per gallon
at full throttle with that huge carb. But went real fast. I sold it
years ago and I bet it don't go real fast no more, with fuel prices
the way they are now.

Dan
  #15  
Old June 2nd 08, 05:30 AM posted to rec.aviation.piloting
Ken S. Tucker
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Posts: 442
Default Ram air

On Jun 1, 7:59 pm, wrote:
On Jun 1, 8:06 pm, Gezellig wrote:



It happens that formulated :


In the 1970's Ford sold some cars with "Ram-Air Induction"
systems. A scoop mounted on the carb that stuck out above the hood, to
ram vast volumes of air into the carb and get way more horsepower.
That's what they wanted you to believe. At 60 mph the pressure
recovery would have been laughably tiny, but Ford's profits were
impressive.


Had a Trans Am, scoop was reversed, facing the windshield, had a flap
that opened when MP increased. They claimd that the reversed position
was at the low pressure point at the base of the windshield hence
enhancing the rammed air effect. I don't know, it was cool, the scoop
assembly was attached to the engine so that on acceleration you could
see the engine sitting down on its mounts as the scopp popped open and
lowere ever so slightly.


Locating the scoop at the low-pressure point wouldn't do much
for ram-air effect, would it? I think the real idea would have been to
make sure the driver heard that thing sucking loudly so it sounded
like a real powerhouse
I once converted a 14 foot outboard runabout to a 13 foot
inboard Cracker Box with a Chev 283 straight-shaft setup. The exhausts
were water-cooled and exited through the transom. Made so much noise
that I made two mufflers and quieted it right down. The carb's flame
arrestor stuck up far enough that I had a scoop on the deck, facing
away from the cockpit (which was at the back). Everything else was
covered. I dropped my Dad off on a gravel bar on a lake once, so he
could fish off it while I ran to the far end of the lake to try the
fishing there, three or four miles away. He told me he knew when I was
coming back; he could hear that Rochester Quadrajet four-barrel open
up and suck vast quantities of air; the boat got one mile per gallon
at full throttle with that huge carb. But went real fast. I sold it
years ago and I bet it don't go real fast no more, with fuel prices
the way they are now.
Dan


I confess to enjoying ancedotal stories.
As a monster nut brat I got some tin cans together
and built a pulse jet, complete with a flapping duct
input, and used a hair dryer for my air input source,
in my parents downstairs fireplace.
So I pour in some gas into the thing, lite it up,
turn on the hair dryer and holy poop, the duct starts
fluttering and flames are fluttering out the ass end!
It worked! It buzzed!

I probably used a pint of gasoline per minute of
operation, but that wasn't the point, it was actually
seeing the damn thing in operation.
Hands on is good stuff.
Ken
  #16  
Old June 2nd 08, 05:46 AM posted to rec.aviation.piloting
[email protected]
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Posts: 8
Default Ram air

On Jun 1, 6:35�am, Tina wrote:

What makes me wonder about it is, even at 60 mph holding your hand out
of the window of a car subjects it to a significant backward pressure,
so the energy must be there.

The energy is there and in a simplified discussion it is called
stagnation pressure, the sum of static pressure and ram air
pressure. As you go faster, static stays the same, ram goes up with
the square of velocity, as discussed already. Your airspeed
indicator uses the two pressures and does the math for you. On the
Tango 2, a homebuilt, we have a ram air scoop below the spinner and a
Y-valve and door for filtered or ram air. When I go to ram air at
150 kias, my manifold pressure goes up about .6 inch. Theoretically I
should recover 1.08 inches. I only have a single buttlerfly Y-valve;
we think some of the air is following the path of least resistance and
going back up the filtered tube. Another Tango 2 has a double
butterfly Y-valve that close off the escape route back through the
filter. His ram rise is about 1.1 or 1.2 inches, which is more than
stagnation. We put his ram air tube a little lower and closer to the
prop as discussed in SPEED WITH ECONOMY by Ken Paser. This seems to
capture the increased pressure behind the blade as it passes the
inlet, timed with the intake valve opening. When we are side by side,
flat out, when he goes ram air he pulls away from me.
I normally don't go ram until I climb above the haze layer and my
power drops below %75. At that point the power goes up about 4-5% and
I can feel the acceleration.
As someone else mentioned, you can't put a funnel out there and
get even more boost. Any excess will just flow around the inlet and
possibly increase drag. We don't know if our setup is optimum, but it
helps. Other homebuilters I've talked to report similar results. Oh,
for a wind tunnel and a lot of money.

Denny
Team Tango
  #17  
Old June 2nd 08, 06:25 AM posted to rec.aviation.piloting
Maxwell[_2_]
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Posts: 2,043
Default Ram air


wrote in message
...
On Jun 1, 8:06 pm, Gezellig wrote:
It happens that formulated :


The biggest performance advantage to ram air was always recognized as COLD
air, not increased pressure. That's why racers began using the base of the
windshield for an intake, instead of forward a scoop. They could get plenty
of cold air without increasing the frontal area of the vehicle. It's
actually a HIGH pressure area, hence the reason so many vehicles have there
fresh air intakes located there.


  #18  
Old June 2nd 08, 06:25 AM posted to rec.aviation.piloting
Maxwell[_2_]
external usenet poster
 
Posts: 2,043
Default Ram air


"Bertie the Bunyip" wrote in message
...
"Ken S. Tucker" wrote in news:94016f66-e3ab-
:

On Jun 1, 11:48 am, wrote:
On Jun 1, 4:35 am, Tina wrote:



The Mooney 201 has a ram air port, a half a foot under the prop
spinner. The POH tells us it can be opened at altitude for a very
modest increase in MP and we find maybe a half inch increase in
pressure. The idea of the thing is, if the port is looking right at
the air being thrust toward it by the prop (it can't be more than 6
inches or so behind it) as well as the air impact from the

airplane's
motion the air being 'rammed' into it should effectively lower the
altitude the engine thinks it's at. Well, a half inch of Hg is

about
500 feet or so. The question is, though, wouldn't you think there
would be a way to capture a great deal more of the ram air effect

and
really boost the engine performance? Who wouldn't like to fly at 24
square at 12000 feet without a turbo charger?

What makes me wonder about it is, even at 60 mph holding your hand

out
of the window of a car subjects it to a significant backward

pressure,
so the energy must be there.

The energy is there but it's no bigger than what Mooney claims.
Flat-plate drag at 100 knots is 29 pounds; dicide that by 144 square
inches and get around 0.2 psi, or about 0.4" Hg. Not much. AT 200
knots it will be four times that, which still isn't a lot.
In the 1970's Ford sold some cars with "Ram-Air Induction"
systems. A scoop mounted on the carb that stuck out above the hood,

to
ram vast volumes of air into the carb and get way more horsepower.
That's what they wanted you to believe. At 60 mph the pressure
recovery would have been laughably tiny, but Ford's profits were
impressive.


That was the good old days!
A jig saw and some sheet metal BLASTED your 427 cube
inch engine to over 600 hp!!!, and at 400-500 mph, you'd be
economizing on fuel to boot!.
Ken


































































































































































You're clueless.



  #19  
Old June 2nd 08, 06:26 AM posted to rec.aviation.piloting
Maxwell[_2_]
external usenet poster
 
Posts: 2,043
Default Ram air


"Bertie the Bunyip" wrote in message
...
Didn't know any production aircraft had that. Well, to some extent
almost every lightplane does . that's why the carb air intake faces
forwards in most of them.Everything is a balancing act with an airplane.
More air = more drag. You could try putting a couple of woks with tubes
out the back to boost your MP, but you're going to pay for it. !Moooney
must have spotted an area of the cowl that would not penalise you in
this way and decided to utilise it. Really clever homebuilders do a lot
of this kind of stuff as well as, and probably more more importantly,
dealing with cooling drag.
Have you put the other speed mods on your airplane? I think there's
nearly ten knots available in seals and various other tidy it up
fairings.

Bertie


Dumb ass.

Its because the size of the scoop increases volume (not pressure), and you
already have too much.


 




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