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fun and games with a manometer

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Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Sat May 28, 2011 12:35 pm Post subject: fun and games with a manometer

I built a U-tube water manometer this week, and finally got a chance  

to try it out (flying) today. Prior to today, I had used it to find a  

slight leak in my pitot system, which I fixed by tightening up the  

Nylo-Seal fittings while watching the indicated leak disappear. Ever  

wonder how much tightening is enough for those fittings? I have, and  

now I know....just use a manometer on the system during the assembly  

of the fittings, and you'll know when to quit tightening.



Today, I got a chance to fly briefly to test the Jabiru-dictated 2.4"  

of water column difference between the inlet air ducts (each side  

tested individually), and the exit-air area of the plane. I haven't  

had any cooling problems, so I just wanted to test how close my  

installation came to meeting that 2.4" measurement.  My installation  

was pretty close to right on the mark...it read about 2.3" to 2.6"  

depending on the bounce of the water in the tube. Pretty happy with  

that, I flew home to add a 1" lip to the bottom of my cowl exit. I  

bent a 20" length of sheet aluminum to a 60° angle, letting 1" stick  

out into the airstream below the cowl, and c-clamped it in place. (I  

didn't want to rivet it in place just to test the theory.)  I went up  

and flew some more...windy day, didn't want to fly too much....and  

now I saw about 2.5" to 3" on either of the two air ducts. But the  

really interesting thing about the last test, was that I saw a mark  

on the aluminum "lip" showing where it was contacting the left  

exhaust pipe. Normally, this pipe cleared the cowl/lip by about 1/2",  

but apparently during flight, my cowl flexes up enough to allow  

contact with the exhaust pipe. No big deal you say, and I agree, but  

if that lip is flexing up 1/2", what just happened to the carefully  

engineered 3:1 ratio of exit air-to-inlet air that shouldn't change?  

Kinda like having a wrong-way operating cowl flap for the exit air,  

I'm thinking. So I need to stiffen up the lower cowl exit flange so  

that it doesn't flex at all, and then do some more testing....maybe a  

center support for the cowl is in order...something that will be  

permanently attached to either the cowl or the airframe, but not  

both, so as to allow for removing the cowl without having to deal  

with another fastener down there.



If anybody's having trouble with overheating issues, yet you're sure  

of the "correctness" of your installation, you might think about the  

rigidity of things when air pressure gets applied.



Lynn Matteson

Kitfox IV Speedster, taildragger

Jabiru 2200, #2062

Prince prop (64 x 30, P-tip)

Electroair direct-fire ignition system

Rotec TBI-40 injection (sleeved to 36mm)

Status: flying with "Ramcharger" intake manifold...1110 hrs (since  

3-27-2006)

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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

zeprep251(at)aol.com
Guest

Posted: Sat May 28, 2011 8:28 pm Post subject: fun and games with a manometer

Lynn,

 Are you certain that the engine torque at max throttle does not rotate the engine in it's mounts far enough to cause contact with the cowl?

    G.Aman

  

     

  

    

     

  

     

  

    --

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Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Sun May 29, 2011 2:19 am Post subject: fun and games with a manometer

Absolutely, positively, pretty damn certain that isn't happening, G.  

This is a 4-cylinder Jabiru after all, and it doesn't move hardly at  

all, let alone 1/2"+ of movement. The cowl flex is the culprit. This  

cowl is a Skyfox cowl, and is unsupported across the whole bottom of  

the exit-air opening. It has a built-in lip of about 1", but it's  

only at about a 15-degree angle to the rest of the cowl, so it  

doesn't offer a lot in the way of stiffening.



Lynn Matteson

Kitfox IV Speedster, taildragger

Jabiru 2200, #2062

Prince prop (64 x 30, P-tip)

Electroair direct-fire ignition system

Rotec TBI-40 injection (sleeved to 36mm)

Status: flying with "Ramcharger" intake manifold...1110 hrs (since  

3-27-2006)





On May 29, 2011, at 12:24 AM, zeprep251(at)aol.com wrote:



 	  Quote: 	
		   Lynn,

 Are you certain that the engine torque at max throttle does not  

 rotate the engine in it's mounts far enough to cause contact with  

 the cowl?

 G.Aman

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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

zeprep251(at)aol.com
Guest

Posted: Sun May 29, 2011 7:52 am Post subject: fun and games with a manometer

Lynn,

 Just a thought.My 2200 is a pusher and I have to rotate the mounts in their sockets every couple years because they take a set that can be seen easily,especially the fronts.It drops the engine almost 1/4 "Do you have dyna-focal mounts in the Kit-Fox? .

             

  

     G.Aman

  

    

     

  

     

  

    --

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Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Sun May 29, 2011 10:33 am Post subject: fun and games with a manometer

They are not dyna-focal, but almost...the mounting bolts point  

straight ahead, so the rubbers sit vertically, and the holes through  

them, horizontally. I changed rubbers for the very reason you  

described....sag. The rubbers I got from USJabiru are soft, while  

ones I got from Sonex (and subsequently removed right after  

installation) are hard as a rock, and transmit vibrations. I went  

back to the Jabiru-supplied rubbers after feeling vibrations from the  

others. Last June I had the engine out for work, and the new  

rubbers...then a year old, and now two years old, are still without  

the tell-tale signs of needing to be rotated or replaced. The first  

set I used for 3 years and they were distorted when I finally  

scrapped them.



I made a brace today to keep the lower edge of the cowl from blowing  

upward and diminishing the exit-air area. It works well, but didn't  

make a lot of difference in the readings I was getting with the  

manometer. The 2.45-3.0" figure still stands....hard to nail the  

figure down because of the bounce of the liquid in the manometer. But  

the numbers are bearing out the validity of doing this test, coupled  

with the very good CHT temperatures....287-304 degrees F. during  

today's flight, and that's pretty typical. OAT today is 79 F.



Looking back at the temporary lip that I made....1" deep, 20" long,  

and at a 60-degree angle to the wind...might have been what caused  

the cowl to deform and touch the exhaust pipe. After all, that's a  

pretty good "airbrake" sticking down into the airstream, and being  

mounted to a flexible cowl, it would want to take the easy route and  

deflect upwards to avoid the wind.



Lynn Matteson

Kitfox IV Speedster, taildragger

Jabiru 2200, #2062

Prince prop (64 x 30, P-tip)

Electroair direct-fire ignition system

Rotec TBI-40 injection (sleeved to 36mm)

Status: flying with "Ramcharger" intake manifold...1110 hrs (since  

3-27-2006)

On May 29, 2011, at 11:49 AM, zeprep251(at)aol.com wrote:



 	  Quote: 	
		   Lynn,

 Just a thought.My 2200 is a pusher and I have to rotate the mounts  

 in their sockets every couple years because they take a set that  

 can be seen easily,especially the fronts.It drops the engine almost  

 1/4 "Do you have dyna-focal mounts in the Kit-Fox? .



 G.Aman

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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

BobsV35B(at)aol.com
Guest

Posted: Sun May 29, 2011 11:11 am Post subject: fun and games with a manometer

Good Afternoon Lynn,

  

 You mentioned that you used a sixty degree lip. Seems to me I once read  that anything beyond thirty degrees of "lip" actually decreases the airflow. It  causes too much turbulence in the area. No knowledge from me. just a memory from  a long time ago.

  

 Happy Skies,

  

 Old Bob

  

 Do Not Archive

  

  In a message dated 5/29/2011 1:33:13 P.M. Central Daylight Time,  lynnmatt(at)jps.net writes:

  	  Quote: 	
		  -->    JabiruEngine-List message posted by: Lynn Matteson    <lynnmatt(at)jps.net>



They are not dyna-focal, but almost...the    mounting bolts point  

straight ahead, so the rubbers sit vertically,    and the holes through  

them, horizontally. I changed rubbers for the    very reason you  

described....sag. The rubbers I got from USJabiru    are soft, while  

ones I got from Sonex (and subsequently removed    right after  

installation) are hard as a rock, and transmit    vibrations. I went  

back to the Jabiru-supplied rubbers after feeling    vibrations from the  

others. Last June I had the engine out for work,    and the new  

rubbers...then a year old, and now two years old, are    still without  

the tell-tale signs of needing to be rotated or    replaced. The first  

set I used for 3 years and they were distorted    when I finally  

scrapped them.



I made a brace today to keep    the lower edge of the cowl from blowing  

upward and diminishing the    exit-air area. It works well, but didn't  

make a lot of difference in    the readings I was getting with the  

manometer. The 2.45-3.0" figure    still stands....hard to nail the  

figure down because of the bounce    of the liquid in the manometer. But  

the numbers are bearing out the    validity of doing this test, coupled  

with the very good CHT    temperatures....287-304 degrees F. during  

today's flight, and that's    pretty typical. OAT today is 79 F.



Looking back at the temporary lip    that I made....1" deep, 20" long,  

and at a 60-degree angle to the    wind...might have been what caused  

the cowl to deform and touch the    exhaust pipe. After all, that's a  

pretty good "airbrake" sticking    down into the airstream, and being  

mounted to a flexible cowl, it    would want to take the easy route and  

deflect upwards to avoid the    wind.



Lynn Matteson

Kitfox IV Speedster, taildragger

Jabiru 2200,    #2062

Prince prop (64 x 30, P-tip)

Electroair direct-fire ignition    system

Rotec TBI-40 injection (sleeved to 36mm)

Status: flying with    "Ramcharger" intake manifold...1110 hrs (since     

3-27-2006)

On May 29, 2011, at 11:49 AM, zeprep251(at)aol.com    wrote:



 	  Quote: 	
		   Lynn,

 Just a thought.My 2200 is a pusher and I have    to rotate the mounts  

 in their sockets every couple years    because they take a set that  

 can be seen easily,especially the    fronts.It drops the engine almost  

 1/4 "Do you have dyna-focal    mounts in the Kit-Fox? .



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Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Mon May 30, 2011 4:57 am Post subject: fun and games with a manometer

Hi Bob-

You're probably right about the 60° lip, and I can't find the source  

of where I got that notion. I just checked the Bingelis books, and it  

wasn't there. Plus, a 60° lip looks out of place and  draggy. I did  

the one flight with the "lip" and removed it, proving nothing.  

Yesterday I built a brace that screws to the firewall, and projects  

down to contact the cowl, and this will keep the cowl from being  

blown upwards, if indeed it ever was (without the added lip, that  

is). This provides two things....it keeps the cowl a bit further away  

from the pipes, and provides a fixed outlet area, not a variable one.



Lynn Matteson

Kitfox IV Speedster, taildragger

Jabiru 2200, #2062

Prince prop (64 x 30, P-tip)

Electroair direct-fire ignition system

Rotec TBI-40 injection (sleeved to 36mm)

Status: flying with "Ramcharger" intake manifold...1110 hrs (since  

3-27-2006)

On May 29, 2011, at 3:08 PM, BobsV35B(at)aol.com wrote:



 	  Quote: 	
		   Good Afternoon Lynn,



 You mentioned that you used a sixty degree lip. Seems to me I once  

 read that anything beyond thirty degrees of "lip" actually  

 decreases the airflow. It causes too much turbulence in the area.  

 No knowledge from me. just a memory from a long time ago.



 Happy Skies,



 Old Bob

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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

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