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Vendors Corner => Aero Products => Topic started by: Dennis Saydak on May 26, 2011, 09:34:02 AM
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Hi Randy, I'm building a Buso designed Jaguar, which was designed for a side exhaust ST .46 engine. I am using a PA .40, which will be my first exposure to a rear exaust setup. Do I go with the cooling vent setup shown in the plan or something different? I don't know how much cooling this engine setup needs and I don't want to make side cooling vents unless they are absolutely necessary. Your suggestion please would be appreciated.
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I'm not Randy, but I'd say that in general if you make such a large change in the engine layout you'll need to make a change in the cooling system to match. As to specifics -- I dunno. My first inclination would be to follow basic principals (make lots of low-velocity air flow past the cooling fins and the exhaust pipe), or to look at a bunch of planes with similar engines, figure out which ones seem to cool well, then ask the owners if you can look at how the cooling air is managed. If you can find magazine plans that detail this -- good. Look at 'em.
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Thanks for the reply Tim. There are lots of plans that show a tuned pipe open tunnel layout but I don't recall a published design with a rear muffler installation. I've thought about replacing the internal V shape air deflectors shown on the plan with a couple of baffles along the exhaust pipe that are wider at the front to direct airflow over the pipe coupler. Perhaps it's just best to leave the entire area under the tank floor open and use side vents?
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Dennis,
I have always been told to have the rear opening at a minimum twice the diameter of the front. I would think 3-4 time the area and make sure you have good flow around the muffler and you'll be fine.
James
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My Jaguars I built I put all of the cooling vents in the top, bottom and sides. BTW I'm running a PA40 lite with header muffler. Great planes, great engine, lots of power!
-Jimmy
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Thanks Jimmy, did you put any sort of air deflectors under the tank floor or just leave that area open?
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No, I did not put deflectors on the bottom of the tank floor. Needed room for header muffler.
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BTW, I had a trim problem. After I changed tip weight and forgot that I had changed it because at first it flew really well, the best flying plane I've ever had, two crashes took off landing gear, then finally remembered I had changed the tip weight from 1 oz in the box to 3/4 oz and had bad problems in hard turns. Finally I checked tip weight box and found that I had changed it and forgot. Now I have 1 1/2 oz in the tip weight box and flies great! Put plenty of tip weight to start with. This is what worked for me anyway. Yours may differ.
-Jimmy
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Hi Basically you just want the air to flow past the muffler before it goes out of an exit, so where ever you put them, top, side, etc just put them back toward the back of the header muffler, You want the air to flow past the engine..and header muffler
Thanks for posting you plane, let up know how it is going
Randy
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Winter has arrived so it's back to building. I did more work on my Jaguar following the advice previously given. Thanks a bunch guys. #^
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Plane is really looking good :-)