Brodhead Pietenpol Association

Original Posted By: Steven Dortch
Gerry;On most photos of J-3s that I've seen, there is a sort of horizontal slot justbelow the hole for the prop hub and then a round hole below that, and then theair filter. I have no idea what the horizontal slot is for but I believe thehole below it leads into the heat muff for carb heat since I believe it has amesh screen in the opening. Neither of those openings should have anything todo with cooling the engine or oil sump. However, the J-3 does not have a pressurecowl so there is cooling air entering through the eyebrows, sweeping downover the cylinders, the out the bottom of the cowling after going around theoil sump and carb.I think you can dispense with any additional cutouts. Test fly it and watch theoil and cylinder head temps and then decide if you need any additional openings.It's easier to cut new ones than to patch ones that you don't need.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 powerRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Sun, 16 Feb 2014 19:44:38 -0600Subject: Pietenpol-List: Eyebrow cowlings

Original Posted By: "taildrags"
The idea there is to help cool the crankcase. I went ahead and put one in mine.Kind of a horizontal oval. For all it takes to do it, it's probably a goodidea to go ahead and do it now.Don EmchNX899DERead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Eyebrow cowlings

Original Posted By: "taildrags"
Steve;The aft parts of the cooling eyebrows (both the ones that I replaced and the newones) touch the back sides of the cooling fins on the heads and cylinders. On my old ones, there were little grooves worn into the aluminum of the eyebrows...that's how close they were. The ram air that comes shooting in the frontneeds to change from velocity pressure to static pressure to get it to go downthrough the fins and around the cylinders and it will escape out the back throughany low-resistance openings it can find. Try to keep the baffles closeto the finned surfaces.In the case of supersonic airplanes like the Piet, this effect is exaggerated andcooling effects are especially important to control as the airplane approachesMach 1 and shock waves form ahead of the cooling eyebrows.All kidding aside, down in hot Texas, you need to direct all the cooling air aroundthe finned surfaces and don't let it shoot past them at the rear of the engine.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 powerRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Scouting for a new home

Original Posted By: owner-pietenpol-list-server(at)matronics.com
And be sure you have the inter-cylinder baffles in places to direct theairflow into the cooling fins rather than just escaping between thecylinders. Harry Fenton shows how to build the baffles on his website:http://www.bowersflybaby.com/tech/fenton.htmJack PhillipsNX899JPSmith Mountain Lake, Virginia-----Original Message-----

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