---------------------------------------------------------- JabiruEngine-List Digest Archive --- Total Messages Posted Sat 05/28/11: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:35 PM - fun and games with a manometer (Lynn Matteson) 2. 09:28 PM - Re: fun and games with a manometer (zeprep251@aol.com) ________________________________ Message 1 _____________________________________ Time: 01:35:55 PM PST US From: Lynn Matteson Subject: JabiruEngine-List: 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) ________________________________ Message 2 _____________________________________ Time: 09:28:04 PM PST US Subject: Re: JabiruEngine-List: fun and games with a manometer From: zeprep251@aol.com 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 -----Original Message----- From: Lynn Matteson e-list@matronics.com> Sent: Sat, May 28, 2011 1:36 pm Subject: JabiruEngine-List: 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=C2=B0 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) ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message jabiruengine-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/JabiruEngine-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/jabiruengine-list Browse Digests http://www.matronics.com/digest/jabiruengine-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.