Today's Message Index:
----------------------
1. 12:58 AM - Re: cutting exhaust pipe (kurt schrader)
2. 02:21 AM - Re: model IV wing tanks (AlbertaIV@aol.com)
3. 03:03 AM - Re: model IV wing tanks (AlbertaIV@aol.com)
4. 03:47 AM - Heading south (Fox5flyer)
5. 04:15 AM - Re: Heading south (Lynn Matteson)
6. 04:48 AM - Re: model IV wing tanks (Lynn Matteson)
7. 06:48 AM - Re: Engine choices (Lowell Fitt)
8. 07:02 AM - Re: Engine choices (Lowell Fitt)
9. 07:56 AM - Re: Re: Engine choices (Harris, Robert)
10. 07:59 AM - Re: model IV wing tanks (Don Pearsall)
11. 09:23 AM - High Altitude Advice wanted. Nice pics Steve (Harris, Robert)
12. 10:00 AM - Re: Engine choices (kurt schrader)
13. 11:21 AM - Jet Thrust was: Re: cutting exhaust pipe (Randy Daughenbaugh)
14. 11:38 AM - SV: Jet Thrust (Michel Verheughe)
15. 11:45 AM - Re: Jet Thrust was: Re: cutting exhaust pipe (Steve Cooper)
16. 11:46 AM - Re: Jet Thrust was: Re: cutting exhaust pipe (kitfoxpilot)
17. 01:04 PM - Re: Jet Thrust was: Re: cutting exhaust pipe (paul wilson)
18. 01:31 PM - Re: Jet Thrust was: Re: cutting exhaust pipe (AlbertaIV@aol.com)
19. 03:40 PM - Re: Jet Thrust was: Re: cutting exhaust pipe (Randy Daughenbaugh)
20. 06:20 PM - Re: Jet Thrust was: Re: cutting exhaust pipe (Don Pearsall)
21. 06:44 PM - Re: High Altitude Advice wanted. (Steve Zakreski)
22. 07:27 PM - Motor mounts (roncarolnikko@webtv.net (Ron Schick))
23. 07:43 PM - Re: Model 5, Subaru and Batterry (Jeff Smathers)
24. 09:21 PM - Re: Jet Thrust was: Re: cutting exhaust pipe (paul wilson)
Message 1
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| Subject: | Re: cutting exhaust pipe |
--> Kitfox-List message posted by: kurt schrader <smokey_bear_40220@yahoo.com>
Thanks Torgier,
Those references are very good. Glad to see such
testing being done. I already learned there that
specifically the soob engine HP can be most
effectively increased by just a little better exhaust
valve grinding. Porting is important I knew, but I
didn't think it was the tops on effectiveness.
Lance, check that out in the ref! Or did you already
know it?
They also talk about exhaust wave speeds of approx
1700 feet per second. Definitely supersonic. Such
high speeds contain a lot of energy that can be used,
if we try.
But I wasn't completely right. The tests showed that
the turbo engines actually increased thrust over the
non turbo engines when at higher altitudes. I hadn't
thought of that. I thought the turbo exhaust was
always less jet.
But their 20 lbs of jet thrust, when sent down at 45
degrees, gives 14 lbs of thrust and 14 lbs of lift.
An 8 lb gain. You get all that for free, if you just
use it right. It is like reducing my plane's weight
by a good amount just by bending a pipe right. I'll
take it!
Kurt S.
--- Torgeir Mortensen <torgemor@online.no> wrote:
> Hi Kurt and all,
> ......................
> Well, as usually, Kurt is ABSOLUTELY right about the
> thrust from the exhaust system.
__________________________________
http://my.yahoo.com
Message 2
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| Subject: | Re: model IV wing tanks |
--> Kitfox-List message posted by: AlbertaIV@aol.com
In a message dated 1/11/05 4:30:24 PM Pacific Standard Time, lynnmatt@jps.net
writes:
<< I just got to thinking about this because I read on this forum just a
few days ago about someone's flaperons having their foam eroded away by
the ingestion of fuel....didn't I? And of course, if it WAS just one
incident, I'd say yes, we have no problem in this area.
Lynn >>
Lynn,
I don't recall seeing that but could have missed it. I seem to remember
once about a flapperon freezing up due to water intrusion. Then again, I
very well could be wrong on that too. I would tend to think that water might be
as big a problem if it didn't leak out and you climbed to a freezing altitude??
Don Smythe
N-998DS Classic IV W/ 582
Message 3
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| Subject: | Re: model IV wing tanks |
--> Kitfox-List message posted by: AlbertaIV@aol.com
In a message dated 1/11/05 7:13:02 PM Pacific Standard Time, wliles@bayou.com
writes:
<<
I've seen fuel get in the flapperon once. A friend had a Kitfox Model
IV (not JR this time) that was overfilled with fuel flowing off the back
of the wing onto the flapperons with fuel entering the slot. It took a
couple of days before it all eva >>
I stand corrected that gas in the flapperons has never happened. It
seems the gas you're talking about stayed in their a long time. Just wondering
if
there are some foams that gas won't destroy (like in the flapperons).
Don Smythe
N-998DS Classic IV W/ 582
Message 4
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--> Kitfox-List message posted by: "Fox5flyer" <morid@northland.lib.mi.us>
Just a quick note to the listers that I'm heading down to FL shortly and
when I have a good weather window I'll be flying a S5 back up here to NE
Michigan. Thanks to those who offered the stopping points.
Deke
Message 5
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| Subject: | Re: Heading south |
--> Kitfox-List message posted by: Lynn Matteson <lynnmatt@jps.net>
Here's a wish for good weather and fun flyin', Deke.
Lynn
do not archive
On Wednesday, January 12, 2005, at 06:43 AM, Fox5flyer wrote:
> --> Kitfox-List message posted by: "Fox5flyer"
> <morid@northland.lib.mi.us>
>
> Just a quick note to the listers that I'm heading down to FL shortly
> and
> when I have a good weather window I'll be flying a S5 back up here to
> NE
> Michigan. Thanks to those who offered the stopping points.
> Deke
>
>
Message 6
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| Subject: | Re: model IV wing tanks |
--> Kitfox-List message posted by: Lynn Matteson <lynnmatt@jps.net>
I thought about this sealing issue last night, and one method might be
to lay down a piece of clear plastic tape such as parcel tape, about,
say, 3" wide and 6" long, so that the sticky side is up. On top of this
lay a piece 1" wide by 4" long, sticky side down. Make a slice into the
very middle of this tape sandwich along the center, going in the long
dimension. Now you have a seal that can be slid over the hinge arm and
applied to the flaperon skin with the exposed 1" wide sticky area all
the way around. You will center the slit over the flaperon hinge arm
slot, both sideways and lengthwise, and stick it down. That should keep
out most of the fuel, water, bugs, and what-have-you, and wouldn't cost
an arm and a leg. It would require taking out the two bolts that hold
the arm to the hinge bracket, but could be done one hinge at a time, so
as to not cause any major downtime. The arm could certainly slide back
and forth in the slit, and the slit would be "self-healing" for the
most part. Maybe, like decals, the seal could be applied using soapy
water to allow for positioning, then squeegeed.
Lynn
On Wednesday, January 12, 2005, at 02:16 AM, kurt schrader wrote:
> --> Kitfox-List message posted by: kurt schrader
> <smokey_bear_40220@yahoo.com>
>
> What if we skinned the cat the other way? Attach a
> thin clear plastic cover to the flapperon bearing horn
> so it can rotate, and let it slide on the flapperon
> over the slot.
>
> Just thinking out loud...
>
> Kurt S.
>
> --- Lynn Matteson <lynnmatt@jps.net> wrote:
>
>> --> Kitfox-List message posted by: Lynn Matteson
>> <lynnmatt@jps.net>
>>
>> I just got to thinking about this because I read on
>> this forum just a
>> few days ago about someone's flaperons having their
>> foam eroded away by
>> the ingestion of fuel....didn't I? And of course, if
>> it WAS just one
>> incident, I'd say yes, we have no problem in this
>> area.
>>
>> Lynn
>> do not archive
>
>
> __________________________________
> http://info.mail.yahoo.com/mail_250
>
>
Message 7
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| Subject: | Re: Engine choices |
--> Kitfox-List message posted by: "Lowell Fitt" <lcfitt@inreach.com>
Deke, I'll go with your numbers. This is the first time I remember any
direct total weight published. The other numbers were told to me.
Lowell
----- Original Message -----
From: "Fox5flyer" <morid@northland.lib.mi.us>
Subject: Re: Kitfox-List: Engine choices
> --> Kitfox-List message posted by: "Fox5flyer" <morid@northland.lib.mi.us>
>
> The exact weight for the NSI EA81 with everything including radiator,
> radiator hoses, cables, motor mount, tanks, etc is 232 lbs. This isn't
> heresay. I weighed it myself just so I would know for sure. It appears
> that either somebody's scale is off by a whole bunch or the numbers got
> mixed up. Another year and the NSI will be over 400 pounds.
> Deke
>
> >
> > The only figure I have seen comparing the 912 and the NSI EA81 was
> > determined by Murle Williams who owns a builders support company and has
a
> > number of aftermarket items for the various Kitfox models.
> >
> > He had both engine installations handy at the time. He weighed both
> systems
> > on the same platform scale. On the same day, as I understand. The
> weights
> > included the engine with all components - fuel system, cooling system,
> > engine mount and fluids. Everything except the cowl. The weights are
as
> > follows.
> >
> > NSI EA81 304 lbs.
> > Rotax 912 UL 169 lbs.
> >
> > This might look like 200 lbs difference at first glance, but it is not.
>
>
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Message 8
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| Subject: | Re: Engine choices |
--> Kitfox-List message posted by: "Lowell Fitt" <lcfitt@inreach.com>
Kurt, Your response might be a bit misleading, and might be why we have had
such a hard time finding hard figures. The number I reported initially
was reportedly the whole monte on a platform scale. Not what two of you
would heft to bolt the "engine" to the firewall. Deke's numbers I can live
with as he apparently included everything, except I didn't understand that
it included oil and coolant at 7 and 8 pounds per gallon, nor the CAP that
everyone seems to add to the system.
Lowell
----- Original Message -----
From: "kurt schrader" <smokey_bear_40220@yahoo.com>
Subject: Re: Kitfox-List: Engine choices
> --> Kitfox-List message posted by: kurt schrader
<smokey_bear_40220@yahoo.com>
>
> Soobs aren't that bad. They are a viable engine
> choice, if you have the mission to match. I can't see
> 300 lbs as right for the weight.
>
> Like Deke, I also weighed almost everything I put on
> my plane, a Series 5. In this case, I installed the
> NSI turbo Soob and came up with a weight of 234 lbs
> installed. The turbo is usually a little heavier than
> that, but I found a few pounds to shave, and it came
> out nearer the non-turbo weight.
>
> Two of us installed the engine by hand including
> having one hand free to install the bolts. Neither of
> us are weight lifters. I doubt very much that we
> could have installed a 300 lb engine that way.
>
> As for batteries, I installed much more battery than
> it required. My origional battery was a "used up",
> turned in battery core that I used for all ground
> testing. It cost me $3, but started the engine every
> time and did all my avionics testing. The smallest
> battery I would want to use though is an 18 lb
> battery, since the engine has no mags. The good news
> is that the turbo engine is low compression and turns
> over easily. Maybe easier then the high compression
> Rotax?
>
> For performance, I claim an 800 lb useful load on
> wheels that I can climb at 750'/min and cruise at 98
> mph. I hope for more performance as I add the
> fairings yet to be tested. And I can load up the
> baggage compartment to 135 lbs without going out of
> CG. 150 lbs if I am careful.
>
> Of course it will climb much better at light weights.
>
> Overall, I can cruise quietly at 3200 rpm doing the
> missions I want to and not worry about high
> repair/rebuild costs. If I am on floats, I can use
> boat dock gas. And most of all, I've got 140 hp at
> 12,000', so short field T/O's with a load are doable
> out of mountain strips or lakes. That was my intended
> mission.
>
> Kurt S. S-5/NSI turbo
>
> --- Fox5flyer <morid@northland.lib.mi.us> wrote:
>
> > The exact weight for the NSI EA81 with everything
> > including radiator, radiator hoses, cables, motor
> > mount, tanks, etc is 232 lbs. This isn't
> > heresay. I weighed it myself just so I would know
> > for sure. It appears that either somebody's scale
> > is off by a whole bunch or the numbers got
> > mixed up. Another year and the NSI will be over 400
> > pounds.
> > Deke
>
>
> BEGIN-ANTISPAM-VOTING-LINKS
> ------------------------------------------------------
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> Spam:
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> Not spam:
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>
>
Message 9
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| Subject: | Re: Engine choices |
--> Kitfox-List message posted by: "Harris, Robert" <Robert_Harris@intuit.com>
Hey Steve, Send us some more pics.
Robert
-----Original Message-----
From: owner-kitfox-list-server@matronics.com
[mailto:owner-kitfox-list-server@matronics.com] On Behalf Of Steve Zakreski
Subject: RE: Kitfox-List: Re: Engine choices
--> Kitfox-List message posted by: Steve Zakreski <szakreski@shaw.ca>
Refer to the picture of me over the mountains I posted two weeks ago. ;-)
SteveZ
Calgary
-----Original Message-----
From: owner-kitfox-list-server@matronics.com
[mailto:owner-kitfox-list-server@matronics.com]On Behalf Of
Lonnie_D._Tillinghast@oxy.com
Subject: Kitfox-List: Re: Engine choices
--> Kitfox-List message posted by: <Lonnie_D._Tillinghast@oxy.com>
Anyone perfectly happy with what they have and simply flying for the fun
of it???
Message 10
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| Subject: | model IV wing tanks |
--> Kitfox-List message posted by: "Don Pearsall" <donpearsall@comcast.net>
Don,
There are some gas tank floats and some carb bowl floats that are made from
foam. So obviously, they were made to withstand gas. However, it could be
that MTBE and alcohol might affect them.
Don Pearsall
-----Original Message-----
From: owner-kitfox-list-server@matronics.com
[mailto:owner-kitfox-list-server@matronics.com] On Behalf Of
AlbertaIV@aol.com
Subject: Re: Kitfox-List: model IV wing tanks
--> Kitfox-List message posted by: AlbertaIV@aol.com
In a message dated 1/11/05 7:13:02 PM Pacific Standard Time,
wliles@bayou.com
writes:
<<
I've seen fuel get in the flapperon once. A friend had a Kitfox Model
IV (not JR this time) that was overfilled with fuel flowing off the back
of the wing onto the flapperons with fuel entering the slot. It took a
couple of days before it all eva >>
I stand corrected that gas in the flapperons has never happened. It
seems the gas you're talking about stayed in their a long time. Just
wondering if
there are some foams that gas won't destroy (like in the flapperons).
Don Smythe
N-998DS Classic IV W/ 582
Message 11
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| Subject: | High Altitude Advice wanted. Nice pics Steve |
--> Kitfox-List message posted by: "Harris, Robert" <Robert_Harris@intuit.com>
Thanks for your pics Steve. I love your plane. You have inspired me to fly
GPS direct at high altitudes.
Do you have any advice on flying a Fox at high altitudes?
Robert
Message 12
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| Subject: | Re: Engine choices |
--> Kitfox-List message posted by: kurt schrader <smokey_bear_40220@yahoo.com>
Lowell,
You have a grudge. As I said, I weighed everything I
could, seperately when available. I weighed the
airframe first, then weighed it after I installed the
engine. I seperately weighed the firewall before
mounting it. I weighed the oil and the coolant. I
weighed the prop.
There was just no way to get to over 300 lbs with this
engine in any accurate measure, either the sum of the
parts, or the total after mounting.
Likewise I weighed the wheels, the landing gear, the
tires, rudder, elevator, wings, stabilizer, rudder
peddels, battery, battery box, my instruments.... on
and on. I know where my weight comes from. I even
weighed the parts before and after covering and
painting to know what a fabric job adds to my plane's
weight. It was a lot less than I thought.
I have an ounce scale to 1 lb. I have a 50 lb scale
for medium items. I have two 300 lb scales. Then I
used aircraft scales for the total weights.
Since the 25 lb CAP prop is used on some 912's and
other engines as well, it is a prop choice, not an
engine choice. I might test a different prop on my
Soob in the future just to see how they compare.
My coolant is 16 lbs. My oil was under 12 lbs. These
are plackarded under the cowl by type, volume and
weight, along with sparkplug type.
I really wonder if all these same weights and effort
toward accuracy are included in the 912 installation.
And the bottom line is that we each have what we chose
and we like it. No reason to attack someone elses
decisions. The soob is heavier, but stronger and a
much more proven engine than the Rotax by shear
numbers produced.
Even though it weighs more, I wanted something I could
trust and wouldn't cost the high price of the Rotax
over time. By memory now, I think I judged the weight
increase around 80 lbs tradeoff for the reliability
and lower costs I wanted. It was the engine package I
chose. And it came ready to install with engine
gauges provided. Maybe 200 hrs building time could be
saved.
You chose a different engine. Fine. Let's also chose
not fight about this. OK?
Kurt S. Happy in KY
--- Lowell Fitt <lcfitt@inreach.com> wrote:
> Kurt, Your response might be a bit misleading, and
> might be why we have had such a hard time finding
> hard figures. The number I reported initially
> was reportedly the whole monte on a platform scale.
> Not what two of you would heft to bolt the
> "engine" to the firewall. Deke's numbers I can live
> with as he apparently included everything, except I
> didn't understand that it included oil and coolant
> at 7 and 8 pounds per gallon, nor the CAP that
> everyone seems to add to the system.
>
> Lowell
__________________________________
http://info.mail.yahoo.com/mail_250
Message 13
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| Subject: | cutting exhaust pipe |
--> Kitfox-List message posted by: "Randy Daughenbaugh" <rjdaugh@rapidnet.com>
Added thrust from the exhaust pipe!
Well you learn something everyday! My apologies to Kurt for harboring some
minor doubts. And thanks to both Kurt and Torgeir.
But it raises a question: Wouldn't it be better to add an elbow and point
the exhaust pipe straight back rather than cut a 45 angle on a downward
pointing exhaust pipe like I did following Skystar's instructions and as Don
found in his airport survey? The EPG seem to suggest that the added back
pressure due to the 90 degree is not too bad.
Also, someone mentioned making a "jet engine" and adding water to vaporize
and add volume to the "jet" thus using some of the energy in the exhaust to
increase thrust. Who did this? Is there a reference? I am an
experimenter and interested.
Randy - Too darn cold to fly today.
.
-----Original Message-----
From: owner-kitfox-list-server@matronics.com
[mailto:owner-kitfox-list-server@matronics.com] On Behalf Of Torgeir
Mortensen
Subject: Re: Kitfox-List: cutting exhaust pipe
--> Kitfox-List message posted by: Torgeir Mortensen <torgemor@online.no>
Hi Kurt and all,
-And a happy new year..
Been reading this one with interest, esp. those comments.
Well, as usually, Kurt is ABSOLUTELY right about the thrust from the
exhaust system.
Let's look at the very known engine, a Lycoming IO 360 (the one most
people know ??), -would you believe that this engine can add up to approx.
"20 LBS" in additional thrust from the exhaust??
This thrust gain is "significant" at cruise altitude.
OK., I'm not going to do any calculation here, but will refer to Cafe
Foundation, this is a "scientific group" making "aircraft performance
reports". This group Sponsored and Funded by the EAA (Experimental
Aircraft Association) and the FAA (Federal Aviation Administration).
Here is two documents related to this topic. The first one is The EPG
(exhaust pressure graph) and Aircraft Exhaust Systems.
If you go to this site, the document start downloading (pdf format) if you
click on the link:
http://www.cafefoundation.org/aprs/epg.pdf
This second report has actual data from an IO-360, the document start
downloading (pdf format) if you click on the link:
http://www.cafefoundation.org/aprs/EPG%20PART%20IV.pdf
Regards,
Torgeir.
On Sun, 2 Jan 2005 11:45:17 -0800 (PST), kurt schrader
<smokey_bear_40220@yahoo.com> wrote:
> --> Kitfox-List message posted by: kurt schrader
> <smokey_bear_40220@yahoo.com>
>
> Hi Don,
>
> I cut mine at the 45 degree angle too. The upper side
> is shorter on mine. I think it allows the exhaust
> pulse to release and expand a little more gradually
> reducing noise slightly over a straight cut. I am not
> sure if there really is another benefit from tip
> cutting, in spite of some claims. You have to
> consider what it does to the airflow around the
> fuselage and not just the exhaust flow.
>
> The bigger effect is to have the exhaust point down at
> 45 degrees. I read where as much as 10% of your
> thrust can come from the exhaust "jet". Pointed
> straight aft, you get 100% of it as thrust. Pointed
> straight down, you get 100% of it as lift.
>
> Whatever the jet benefit, due to the benefits of
> geometry, you get not 100%, but 141.4% of the
> thrust/lift benefit at that 45 degree angle. You get
> ~71% thrust and ~71% lift when at 45 degrees.
>
> Say mine was quite a small jet thrust in cruise - 10
> lbs due to my turbo reducing exhaust energy. At the
> 45, I still get 7.1 lbs of thrust and 7.1 lbs of added
> lift. Four pounds gained just by an angle? Easier
> than reducing 4 lbs of weight...
>
> Though mine is not quite 45 degrees, whatever the
> gain, I'll take it.
>
> Kurt S. S-5/NSI turbo
>
> --- AlbertaIV@aol.com wrote:
>
>> I seem to remember once about cutting the tail end
>> of the exhaust pipe at a 45 degree angle on the
>> backside of the airflow. This was either to reduce
>> drag or help promote good exhaust flow as it exits
>> (or both). Does anyone have any thoughts on this?
>> I had to weld a short extension on my exhaust pipe
>> and right now it is cut square.
>>
>> Don Smythe
>> N-998DS Classic IV W/ 582
>
>
> __________________________________
> Dress up your holiday email, Hollywood style. Learn more.
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>
>
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Message 14
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--> Kitfox-List message posted by: Michel Verheughe <michel@online.no>
> From: Randy Daughenbaugh [rjdaugh@rapidnet.com]
> Also, someone mentioned making a "jet engine" and adding water to vaporize
> and add volume to the "jet" thus using some of the energy in the exhaust to
> increase thrust. Who did this?
My father flew the C-119 Flying Boxcar for the Belgian Air Force from 1952 to 1961,
Randi. The two 3,500 HP Pratt & Withney engines needed water injection at
take-off. I think it was to cool the engine more than the extra "jet power."
Although it might have helped a bit, somehow. I know that US C-119 used JATOs
for short field operations in Vietnam. But that's another story.
Cheers,
Michel
do not archive
Message 15
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| Subject: | cutting exhaust pipe |
--> Kitfox-List message posted by: "Steve Cooper" <spdrflyr@earthlink.net>
Isn't it the scavenging effect of the angle cut that the author was
referring to? Especially on a two-stroke, the angle of the cut can have a
great deal of impact on performance...especially if the muffler system is a
marginal performer. Expansion Chambers use a similar method to scavenge
combustion from the cylinder making the next fuel/air mixture charge combust
more completely. NASA did a number of experiments at Dryden to establish the
delta for exhaust gas/slip stream pressure gradient analysis.
-----Original Message-----
From: owner-kitfox-list-server@matronics.com
[mailto:owner-kitfox-list-server@matronics.com] On Behalf Of Randy
Daughenbaugh
Subject: Jet Thrust was: RE: Kitfox-List: cutting exhaust pipe
--> Kitfox-List message posted by: "Randy Daughenbaugh"
<rjdaugh@rapidnet.com>
Added thrust from the exhaust pipe!
Well you learn something everyday! My apologies to Kurt for harboring some
minor doubts. And thanks to both Kurt and Torgeir.
But it raises a question: Wouldn't it be better to add an elbow and point
the exhaust pipe straight back rather than cut a 45 angle on a downward
pointing exhaust pipe like I did following Skystar's instructions and as Don
found in his airport survey? The EPG seem to suggest that the added back
pressure due to the 90 degree is not too bad.
Also, someone mentioned making a "jet engine" and adding water to vaporize
and add volume to the "jet" thus using some of the energy in the exhaust to
increase thrust. Who did this? Is there a reference? I am an
experimenter and interested.
Randy - Too darn cold to fly today.
.
-----Original Message-----
From: owner-kitfox-list-server@matronics.com
[mailto:owner-kitfox-list-server@matronics.com] On Behalf Of Torgeir
Mortensen
Subject: Re: Kitfox-List: cutting exhaust pipe
--> Kitfox-List message posted by: Torgeir Mortensen <torgemor@online.no>
Hi Kurt and all,
-And a happy new year..
Been reading this one with interest, esp. those comments.
Well, as usually, Kurt is ABSOLUTELY right about the thrust from the
exhaust system.
Let's look at the very known engine, a Lycoming IO 360 (the one most
people know ??), -would you believe that this engine can add up to approx.
"20 LBS" in additional thrust from the exhaust??
This thrust gain is "significant" at cruise altitude.
OK., I'm not going to do any calculation here, but will refer to Cafe
Foundation, this is a "scientific group" making "aircraft performance
reports". This group Sponsored and Funded by the EAA (Experimental
Aircraft Association) and the FAA (Federal Aviation Administration).
Here is two documents related to this topic. The first one is The EPG
(exhaust pressure graph) and Aircraft Exhaust Systems.
If you go to this site, the document start downloading (pdf format) if you
click on the link:
http://www.cafefoundation.org/aprs/epg.pdf
This second report has actual data from an IO-360, the document start
downloading (pdf format) if you click on the link:
http://www.cafefoundation.org/aprs/EPG%20PART%20IV.pdf
Regards,
Torgeir.
On Sun, 2 Jan 2005 11:45:17 -0800 (PST), kurt schrader
<smokey_bear_40220@yahoo.com> wrote:
> --> Kitfox-List message posted by: kurt schrader
> <smokey_bear_40220@yahoo.com>
>
> Hi Don,
>
> I cut mine at the 45 degree angle too. The upper side
> is shorter on mine. I think it allows the exhaust
> pulse to release and expand a little more gradually
> reducing noise slightly over a straight cut. I am not
> sure if there really is another benefit from tip
> cutting, in spite of some claims. You have to
> consider what it does to the airflow around the
> fuselage and not just the exhaust flow.
>
> The bigger effect is to have the exhaust point down at
> 45 degrees. I read where as much as 10% of your
> thrust can come from the exhaust "jet". Pointed
> straight aft, you get 100% of it as thrust. Pointed
> straight down, you get 100% of it as lift.
>
> Whatever the jet benefit, due to the benefits of
> geometry, you get not 100%, but 141.4% of the
> thrust/lift benefit at that 45 degree angle. You get
> ~71% thrust and ~71% lift when at 45 degrees.
>
> Say mine was quite a small jet thrust in cruise - 10
> lbs due to my turbo reducing exhaust energy. At the
> 45, I still get 7.1 lbs of thrust and 7.1 lbs of added
> lift. Four pounds gained just by an angle? Easier
> than reducing 4 lbs of weight...
>
> Though mine is not quite 45 degrees, whatever the
> gain, I'll take it.
>
> Kurt S. S-5/NSI turbo
>
> --- AlbertaIV@aol.com wrote:
>
>> I seem to remember once about cutting the tail end
>> of the exhaust pipe at a 45 degree angle on the
>> backside of the airflow. This was either to reduce
>> drag or help promote good exhaust flow as it exits
>> (or both). Does anyone have any thoughts on this?
>> I had to weld a short extension on my exhaust pipe
>> and right now it is cut square.
>>
>> Don Smythe
>> N-998DS Classic IV W/ 582
>
>
> __________________________________
> Dress up your holiday email, Hollywood style. Learn more.
> http://celebrity.mail.yahoo.com
>
>
--
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/
Message 16
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| Subject: | Re: cutting exhaust pipe |
--> Kitfox-List message posted by: "kitfoxpilot" <kitfoxpilot@comcast.net>
There is a book called "speed with economy" by Kent Paser. It covers many
aerodynamic mod and engine mods that improved the performance of his Bushby
Mustang II. He did a lot of work with his exhaust system to take advantage
of exhaust thrust.
As far as water vapor and jet engines, some Boeing 707 were equipped with
water injection to aid take off thrust.
Scott Miller
Series 7
Seattle
----- Original Message -----
From: "Randy Daughenbaugh" <rjdaugh@rapidnet.com>
Subject: Jet Thrust was: RE: Kitfox-List: cutting exhaust pipe
> --> Kitfox-List message posted by: "Randy Daughenbaugh"
<rjdaugh@rapidnet.com>
>
> Added thrust from the exhaust pipe!
>
> Well you learn something everyday! My apologies to Kurt for harboring
some
> minor doubts. And thanks to both Kurt and Torgeir.
>
> But it raises a question: Wouldn't it be better to add an elbow and point
> the exhaust pipe straight back rather than cut a 45 angle on a downward
> pointing exhaust pipe like I did following Skystar's instructions and as
Don
> found in his airport survey? The EPG seem to suggest that the added back
> pressure due to the 90 degree is not too bad.
>
> Also, someone mentioned making a "jet engine" and adding water to vaporize
> and add volume to the "jet" thus using some of the energy in the exhaust
to
> increase thrust. Who did this? Is there a reference? I am an
> experimenter and interested.
>
> Randy - Too darn cold to fly today.
>
> .
>
>
> -----Original Message-----
> From: owner-kitfox-list-server@matronics.com
> [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of Torgeir
> Mortensen
> To: kitfox-list@matronics.com
> Subject: Re: Kitfox-List: cutting exhaust pipe
>
> --> Kitfox-List message posted by: Torgeir Mortensen <torgemor@online.no>
>
> Hi Kurt and all,
>
> -And a happy new year..
>
> Been reading this one with interest, esp. those comments.
>
> Well, as usually, Kurt is ABSOLUTELY right about the thrust from the
> exhaust system.
>
> Let's look at the very known engine, a Lycoming IO 360 (the one most
> people know ??), -would you believe that this engine can add up to approx.
> "20 LBS" in additional thrust from the exhaust??
>
> This thrust gain is "significant" at cruise altitude.
>
> OK., I'm not going to do any calculation here, but will refer to Cafe
> Foundation, this is a "scientific group" making "aircraft performance
> reports". This group Sponsored and Funded by the EAA (Experimental
> Aircraft Association) and the FAA (Federal Aviation Administration).
>
> Here is two documents related to this topic. The first one is The EPG
> (exhaust pressure graph) and Aircraft Exhaust Systems.
>
> If you go to this site, the document start downloading (pdf format) if you
> click on the link:
>
> http://www.cafefoundation.org/aprs/epg.pdf
>
> This second report has actual data from an IO-360, the document start
> downloading (pdf format) if you click on the link:
>
> http://www.cafefoundation.org/aprs/EPG%20PART%20IV.pdf
>
>
> Regards,
>
> Torgeir.
>
>
> On Sun, 2 Jan 2005 11:45:17 -0800 (PST), kurt schrader
> <smokey_bear_40220@yahoo.com> wrote:
>
> > --> Kitfox-List message posted by: kurt schrader
> > <smokey_bear_40220@yahoo.com>
> >
> > Hi Don,
> >
> > I cut mine at the 45 degree angle too. The upper side
> > is shorter on mine. I think it allows the exhaust
> > pulse to release and expand a little more gradually
> > reducing noise slightly over a straight cut. I am not
> > sure if there really is another benefit from tip
> > cutting, in spite of some claims. You have to
> > consider what it does to the airflow around the
> > fuselage and not just the exhaust flow.
> >
> > The bigger effect is to have the exhaust point down at
> > 45 degrees. I read where as much as 10% of your
> > thrust can come from the exhaust "jet". Pointed
> > straight aft, you get 100% of it as thrust. Pointed
> > straight down, you get 100% of it as lift.
> >
> > Whatever the jet benefit, due to the benefits of
> > geometry, you get not 100%, but 141.4% of the
> > thrust/lift benefit at that 45 degree angle. You get
> > ~71% thrust and ~71% lift when at 45 degrees.
> >
> > Say mine was quite a small jet thrust in cruise - 10
> > lbs due to my turbo reducing exhaust energy. At the
> > 45, I still get 7.1 lbs of thrust and 7.1 lbs of added
> > lift. Four pounds gained just by an angle? Easier
> > than reducing 4 lbs of weight...
> >
> > Though mine is not quite 45 degrees, whatever the
> > gain, I'll take it.
> >
> > Kurt S. S-5/NSI turbo
> >
> > --- AlbertaIV@aol.com wrote:
> >
> >> I seem to remember once about cutting the tail end
> >> of the exhaust pipe at a 45 degree angle on the
> >> backside of the airflow. This was either to reduce
> >> drag or help promote good exhaust flow as it exits
> >> (or both). Does anyone have any thoughts on this?
> >> I had to weld a short extension on my exhaust pipe
> >> and right now it is cut square.
> >>
> >> Don Smythe
> >> N-998DS Classic IV W/ 582
> >
> >
> > __________________________________
> > Dress up your holiday email, Hollywood style. Learn more.
> > http://celebrity.mail.yahoo.com
> >
> >
>
>
> --
> Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/
>
>
Message 17
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| Subject: | Re: cutting exhaust pipe |
--> Kitfox-List message posted by: paul wilson <pwilson@climber.org>
At 12:20 PM 1/12/05 -0700, you wrote:
>--> Kitfox-List message posted by: "Randy Daughenbaugh" <rjdaugh@rapidnet.com>
>
>Added thrust from the exhaust pipe!
>
>Well you learn something everyday! My apologies to Kurt for harboring some
>minor doubts. And thanks to both Kurt and Torgeir.
>
>But it raises a question: Wouldn't it be better to add an elbow and point
>the exhaust pipe straight back rather than cut a 45 angle on a downward
>pointing exhaust pipe like I did following Skystar's instructions and as Don
>found in his airport survey? The EPG seem to suggest that the added back
>pressure due to the 90 degree is not too bad.
==============
I used the slash cut on some rocket nozzles - a long time ago. NASA did
much research on the subject of these kinds of nozzles. An elbow is bad due
to the losses but the slash or cut we are talking about had little
degradation. All that happens is the flow is deflected. If anybody wants to
get into the exact math I can dig out the documents. The trouble is the
paper is 1000+ miles from my winter home and I wont have access until next
spring. The issue is that one needs to predict the angle of the gas with
respect to the slash angle and that requires some flow measurements and
some math.
But for a low velocity for the engine exhaust, a gentle bend would be a
good way to go as opposed to the slash we used for supersonic rocket
exhaust. Just point the exhaust straight back. Keep the pipe radius large
to avoid losses and back pressure. The exhaust heating up the fabric would
also be another issue. Remember that the exhaust fares to a larger diameter
than the pipe as soon as it exits the pipe. This effect gets much bigger at
altitude so significant clearance is required. So the pipe must stick out
further into the air stream and this means more drag. The pipe can be close
to a metal plane but not so in the KF.
Ever noticed the turboprop engines . They go to a lot of trouble to make
the exhaust pipe aerodynamic since to sticks out in the air stream in order
to have point gas aft for the thrust augmentation.
With regard to increasing the energy of the exhaust gas, The supersonic
nozzle will create back pressure and mess up the engine performance. adding
fuel would help, but that is another technology beyond the scope of non-
rocket designers.
Paul
Message 18
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| Subject: | Re: cutting exhaust pipe |
--> Kitfox-List message posted by: AlbertaIV@aol.com
In a message dated 1/12/05 11:22:15 AM Pacific Standard Time,
rjdaugh@rapidnet.com writes:
<<
Well you learn something everyday! My apologies to Kurt for harboring some
minor doubts. And thanks to both Kurt and Torgeir.
>>
Duh,,,me to Kurt. I did razz you a bit on this one.
Do Not Archive
Don Smythe
N-998DS Classic IV W/ 582
Message 19
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| Subject: | cutting exhaust pipe |
--> Kitfox-List message posted by: "Randy Daughenbaugh" <rjdaugh@rapidnet.com>
Paul,
Thanks! That helps.
I appreciate you pointing out the danger to fabric. Potentially dirty too.
Randy Do not archive
.
-----Original Message-----
From: owner-kitfox-list-server@matronics.com
[mailto:owner-kitfox-list-server@matronics.com] On Behalf Of paul wilson
Subject: Re: Jet Thrust was: RE: Kitfox-List: cutting exhaust pipe
--> Kitfox-List message posted by: paul wilson <pwilson@climber.org>
At 12:20 PM 1/12/05 -0700, you wrote:
>--> Kitfox-List message posted by: "Randy Daughenbaugh"
<rjdaugh@rapidnet.com>
>
>Added thrust from the exhaust pipe!
>
>Well you learn something everyday! My apologies to Kurt for harboring some
>minor doubts. And thanks to both Kurt and Torgeir.
>
>But it raises a question: Wouldn't it be better to add an elbow and point
>the exhaust pipe straight back rather than cut a 45 angle on a downward
>pointing exhaust pipe like I did following Skystar's instructions and as
Don
>found in his airport survey? The EPG seem to suggest that the added back
>pressure due to the 90 degree is not too bad.
==============
I used the slash cut on some rocket nozzles - a long time ago. NASA did
much research on the subject of these kinds of nozzles. An elbow is bad due
to the losses but the slash or cut we are talking about had little
degradation. All that happens is the flow is deflected. If anybody wants to
get into the exact math I can dig out the documents. The trouble is the
paper is 1000+ miles from my winter home and I wont have access until next
spring. The issue is that one needs to predict the angle of the gas with
respect to the slash angle and that requires some flow measurements and
some math.
But for a low velocity for the engine exhaust, a gentle bend would be a
good way to go as opposed to the slash we used for supersonic rocket
exhaust. Just point the exhaust straight back. Keep the pipe radius large
to avoid losses and back pressure. The exhaust heating up the fabric would
also be another issue. Remember that the exhaust fares to a larger diameter
than the pipe as soon as it exits the pipe. This effect gets much bigger at
altitude so significant clearance is required. So the pipe must stick out
further into the air stream and this means more drag. The pipe can be close
to a metal plane but not so in the KF.
Ever noticed the turboprop engines . They go to a lot of trouble to make
the exhaust pipe aerodynamic since to sticks out in the air stream in order
to have point gas aft for the thrust augmentation.
With regard to increasing the energy of the exhaust gas, The supersonic
nozzle will create back pressure and mess up the engine performance. adding
fuel would help, but that is another technology beyond the scope of non-
rocket designers.
Paul
Message 20
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| Subject: | cutting exhaust pipe |
--> Kitfox-List message posted by: "Don Pearsall" <donpearsall@comcast.net>
Now that we are talking about far-out exhaust ideas, one thing that always
intrigued me was using the exhaust as a vacuum source. In theory, wouldn't
putting a venturi in the exhaust pipe(s) work to create a vacuum source for
instruments the same way as an external one? The exhaust vacuum source would
be instant as soon as the engine is started, while the external one doesn't
start working till about 30 mph.
Has anyone done this or seen it done, or has any theories about it?
Don Pearsall
http://www.soundappraisal.com
-----Original Message-----
From: owner-kitfox-list-server@matronics.com
[mailto:owner-kitfox-list-server@matronics.com] On Behalf Of Randy
Daughenbaugh
Subject: RE: Jet Thrust was: RE: Kitfox-List: cutting exhaust pipe
--> Kitfox-List message posted by: "Randy Daughenbaugh"
<rjdaugh@rapidnet.com>
Paul,
Thanks! That helps.
I appreciate you pointing out the danger to fabric. Potentially dirty too.
Randy Do not archive
.
-----Original Message-----
From: owner-kitfox-list-server@matronics.com
[mailto:owner-kitfox-list-server@matronics.com] On Behalf Of paul wilson
Subject: Re: Jet Thrust was: RE: Kitfox-List: cutting exhaust pipe
--> Kitfox-List message posted by: paul wilson <pwilson@climber.org>
At 12:20 PM 1/12/05 -0700, you wrote:
>--> Kitfox-List message posted by: "Randy Daughenbaugh"
<rjdaugh@rapidnet.com>
>
>Added thrust from the exhaust pipe!
>
>Well you learn something everyday! My apologies to Kurt for harboring some
>minor doubts. And thanks to both Kurt and Torgeir.
>
>But it raises a question: Wouldn't it be better to add an elbow and point
>the exhaust pipe straight back rather than cut a 45 angle on a downward
>pointing exhaust pipe like I did following Skystar's instructions and as
Don
>found in his airport survey? The EPG seem to suggest that the added back
>pressure due to the 90 degree is not too bad.
==============
I used the slash cut on some rocket nozzles - a long time ago. NASA did
much research on the subject of these kinds of nozzles. An elbow is bad due
to the losses but the slash or cut we are talking about had little
degradation. All that happens is the flow is deflected. If anybody wants to
get into the exact math I can dig out the documents. The trouble is the
paper is 1000+ miles from my winter home and I wont have access until next
spring. The issue is that one needs to predict the angle of the gas with
respect to the slash angle and that requires some flow measurements and
some math.
But for a low velocity for the engine exhaust, a gentle bend would be a
good way to go as opposed to the slash we used for supersonic rocket
exhaust. Just point the exhaust straight back. Keep the pipe radius large
to avoid losses and back pressure. The exhaust heating up the fabric would
also be another issue. Remember that the exhaust fares to a larger diameter
than the pipe as soon as it exits the pipe. This effect gets much bigger at
altitude so significant clearance is required. So the pipe must stick out
further into the air stream and this means more drag. The pipe can be close
to a metal plane but not so in the KF.
Ever noticed the turboprop engines . They go to a lot of trouble to make
the exhaust pipe aerodynamic since to sticks out in the air stream in order
to have point gas aft for the thrust augmentation.
With regard to increasing the energy of the exhaust gas, The supersonic
nozzle will create back pressure and mess up the engine performance. adding
fuel would help, but that is another technology beyond the scope of non-
rocket designers.
Paul
Message 21
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| Subject: | High Altitude Advice wanted. |
--> Kitfox-List message posted by: Steve Zakreski <szakreski@shaw.ca>
Robert
Not really. I find it the safest place to fly and I find it very relaxing
up there. Usually no turbulence, no aircraft, no towers, above most control
zones, above a lot of the clouds, and virtually always within gliding
distance to a safe landing, out of the influence of most mountain waves, and
you can see bad weather many many miles away.
And the visibility is usually spectacular! Even the clouds look
spectacular.
Obviously there are oxygen requirements above 12,500 asl in the USA.
(10,000 asl in Canada ...go figure).
In Canada, there are many areas where anything above 12,500 asl is
controlled airspace, so you need to be in contact with ATC. But there are
also many areas where you can cruise way up at 18,000 if you're so inclined.
Typically I go high eastbound, low westbound to favour the prevailing winds.
A 40 knot headwind can almost double the length of a flight for a Kitfox.
Then again, when it is a tailwind...
When fly to Toronto, I often see a 105 knot true airspeed but a 145 knot
ground speed. ATC often ask to confirm I'm really a Kitfox.
I often carry portable oxygen, but I can't say I use it much. I hear so many
horror stories, but after a lot of serious experimenting I can't say I can
feel any altitude affects until 15,000 asl and even then it is minor. I
live at 4000' asl so maybe that helps. I'm not promoting anyone busting the
regs, but I am saying that going to high altitude is very often the safest
place to be.
One enemy of high altitude is an aircraft fire...so make sure you make your
fuel system as perfect as possible.
SteveZ
Calgary
-----Original Message-----
From: owner-kitfox-list-server@matronics.com
[mailto:owner-kitfox-list-server@matronics.com]On Behalf Of Harris,
Robert
Subject: Kitfox-List: High Altitude Advice wanted. Nice pics Steve
--> Kitfox-List message posted by: "Harris, Robert"
<Robert_Harris@intuit.com>
Thanks for your pics Steve. I love your plane. You have inspired me to fly
GPS direct at high altitudes.
Do you have any advice on flying a Fox at high altitudes?
Robert
Message 22
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--> Kitfox-List message posted by: roncarolnikko@webtv.net (Ron Schick)
Since all of the recent discusions on engines, I have been trying to
locate a c-75 to 90 as this sounded like a good engine choice for my 92
speedster. Unfortunately the few I have found seem really expensive. Now
I find myself again looking at my VW parts and think I may commit to
using the parts I already have. One of our fellow members has a motor
mount from an Avid Mk4 and I was wondering if anyone knew if it would
bolt up to the kitfox 4. It is one of those parts I can build, but if it
fits might work well for both of us. Being the Speedster model I will be
eating up the runway anyway. It would definately be for that "differrent
mission". Thanx again Ron
do not archive
Message 23
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| Subject: | Re: Model 5, Subaru and Batterry |
--> Kitfox-List message posted by: Jeff Smathers <jsmathers@cybcon.com>
Trey,
Its either a battery or ballast. My CG on my KF5 w/ NSI EA-81 and CAP140
with a 26lb. Genesis Odyssey battery in the tail came out perfect. You can go
with a lighter battery but you better weigh more than 180-200 lbs in the seat.
and plan
on putting your ELT in the tail.
Jeff Smathers N456JT 853lbs total wt. 800 on mains and 53 on the tail wheel.
Trey Moran wrote:
> --> Kitfox-List message posted by: "Trey Moran" <ffmoran@centurytel.net>
>
> Question for Model 5 builders or flyers with Subaru EA81 engines, preferably
with a Stratus, but will take info on NSI. I don't like the idea of putting the
battery in the tail and was hoping someone has put the battery more forward
and can provide cg info. It would also be helpful to have cg numbers, including
weight and arm for the battery, for a plane with the forward swept wing so
I could do some what if cg calculations.
>
> Trey Moran
>
Message 24
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| Subject: | cutting exhaust pipe |
--> Kitfox-List message posted by: paul wilson <pwilson@climber.org>
The use of the exhaust for alternate vac is available as a kit. Cant source
it for you but I know that it was a big discussion for Cesnas back a while
ago. I think a little experimentation using a venturi could be adapted for
a sole source of vac. A neat idea because it will deliver vac whenever the
engine is at full speed. Not so good during landing when the engine is at idle.
For alternate vac the kit included a trick vac valve to make the switchover.
Paul
===========
At 06:19 PM 1/12/05 -0800, you wrote:
>--> Kitfox-List message posted by: "Don Pearsall" <donpearsall@comcast.net>
>
>Now that we are talking about far-out exhaust ideas, one thing that always
>intrigued me was using the exhaust as a vacuum source. In theory, wouldn't
>putting a venturi in the exhaust pipe(s) work to create a vacuum source for
>instruments the same way as an external one? The exhaust vacuum source would
>be instant as soon as the engine is started, while the external one doesn't
>start working till about 30 mph.
>
>Has anyone done this or seen it done, or has any theories about it?
>
>Don Pearsall
>
>http://www.soundappraisal.com
>-----Original Message-----
>From: owner-kitfox-list-server@matronics.com
>[mailto:owner-kitfox-list-server@matronics.com] On Behalf Of Randy
>Daughenbaugh
>To: kitfox-list@matronics.com
>Subject: RE: Jet Thrust was: RE: Kitfox-List: cutting exhaust pipe
>
>--> Kitfox-List message posted by: "Randy Daughenbaugh"
><rjdaugh@rapidnet.com>
>
>Paul,
>Thanks! That helps.
>
>I appreciate you pointing out the danger to fabric. Potentially dirty too.
>
>Randy Do not archive
>
>.
>
>
>-----Original Message-----
>From: owner-kitfox-list-server@matronics.com
>[mailto:owner-kitfox-list-server@matronics.com] On Behalf Of paul wilson
>To: kitfox-list@matronics.com
>Subject: Re: Jet Thrust was: RE: Kitfox-List: cutting exhaust pipe
>
>--> Kitfox-List message posted by: paul wilson <pwilson@climber.org>
>
>At 12:20 PM 1/12/05 -0700, you wrote:
> >--> Kitfox-List message posted by: "Randy Daughenbaugh"
><rjdaugh@rapidnet.com>
> >
> >Added thrust from the exhaust pipe!
> >
> >Well you learn something everyday! My apologies to Kurt for harboring some
> >minor doubts. And thanks to both Kurt and Torgeir.
> >
> >But it raises a question: Wouldn't it be better to add an elbow and point
> >the exhaust pipe straight back rather than cut a 45 angle on a downward
> >pointing exhaust pipe like I did following Skystar's instructions and as
>Don
> >found in his airport survey? The EPG seem to suggest that the added back
> >pressure due to the 90 degree is not too bad.
>==============
> I used the slash cut on some rocket nozzles - a long time ago. NASA did
>much research on the subject of these kinds of nozzles. An elbow is bad due
>to the losses but the slash or cut we are talking about had little
>degradation. All that happens is the flow is deflected. If anybody wants to
>get into the exact math I can dig out the documents. The trouble is the
>paper is 1000+ miles from my winter home and I wont have access until next
>spring. The issue is that one needs to predict the angle of the gas with
>respect to the slash angle and that requires some flow measurements and
>some math.
>
> But for a low velocity for the engine exhaust, a gentle bend would be a
>good way to go as opposed to the slash we used for supersonic rocket
>exhaust. Just point the exhaust straight back. Keep the pipe radius large
>to avoid losses and back pressure. The exhaust heating up the fabric would
>also be another issue. Remember that the exhaust fares to a larger diameter
>than the pipe as soon as it exits the pipe. This effect gets much bigger at
>altitude so significant clearance is required. So the pipe must stick out
>further into the air stream and this means more drag. The pipe can be close
>to a metal plane but not so in the KF.
> Ever noticed the turboprop engines . They go to a lot of trouble to make
>the exhaust pipe aerodynamic since to sticks out in the air stream in order
>to have point gas aft for the thrust augmentation.
>
> With regard to increasing the energy of the exhaust gas, The supersonic
>nozzle will create back pressure and mess up the engine performance. adding
>fuel would help, but that is another technology beyond the scope of non-
>rocket designers.
>
> Paul
>
>
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