From: dhill36@juno.com Date: Wed, 2 Feb 2000 23:55:53 -0500 Subject: COZY: Ch 7: Mating the side layup to bottom layup Dear Cozyites, Got a question: Got the bottom layup completed, finally. Due to some rather poor planning I have ended up with the 1st ply of UNI even along the 1/4" edge of the exposed longeron and the 2nd ply of UNI 1" or slightly more beyond the 1st ply. I had wanted to do the reverse. The bottom came out great but I am wondering if I should be concerned that my side layups will not be able to 'grab' each ply separately???? Over the past two years I've read an awful lot of stuff, archives, Rutan's Moldless Composite... book, etc. and I can't ever remember reading anything about this type of question. If I glue, with 1" overlap, two sheets of plywood together I think that the strength (in tension) would be less than if the plys were interlocked. Is this a valid analogy?? Dana Hill CZ IV #676 Ch 7 ________________________________________________________________ YOU'RE PAYING TOO MUCH FOR THE INTERNET! Juno now offers FREE Internet Access! Try it today - there's no risk! For your FREE software, visit: http://dl.www.juno.com/get/tagj. Date: Fri, 04 Feb 2000 18:46:23 -0500 From: "Marc J. Zeitlin" Subject: COZY: Ch 7: Mating the side layup to bottom layup Dana Hill wrote: >..... I have ended up with the 1st ply of UNI even along >the 1/4" edge of the exposed longeron and the 2nd ply of UNI 1" or >slightly more beyond the 1st ply. I had wanted to do the reverse. The >bottom came out great but I am wondering if I should be concerned that my >side layups will not be able to 'grab' each ply separately???? No. Just make sure that when you overlap the next plies, they overlap the SHORTEST of the layers that you're attaching to. This will ensure that there's never fewer than the recommended # of plies in the layup. > If I glue, with 1" overlap, two sheets of plywood together I think that >the strength (in tension) would be less than if the plys were >interlocked. Is this a valid analogy?? Yes, and you're right, it's not quite as strong. In this case, it doesn't really matter. -- Marc J. Zeitlin mailto:marc_zeitlin@alum.mit.edu http://www.ultranet.com/~marcz/ From: CozyBuilder@aol.com Date: Mon, 8 May 2000 15:40:57 EDT Subject: COZY: naca scoop or armpits Time to build the NACA scoop. What does that stand for anyway? I read the archives and some say it's tricky, some of the dimensions in the plans are wrong, and if some could do it over, they would have used armpit scoops. I think they come from aerocad 1. what are they. 2. are they recommended over the plans naca 3. If i go with plans naca, anything I should know other than what plans say about it? Jay #858 Escondido CA Finishing ch 6 (taping joints for bottom) My Website http://www.cozybuilder.com Date: Mon, 8 May 2000 15:44:34 -0500 From: "Tom Brusehaver" Subject: Re: COZY: naca scoop or armpits Time to build the NACA scoop. What does that stand for anyway? NACA was the predesessor to NASA. NACA stands for National Advisory Committee for Aeronautics. They did research. See I read the archives and some say it's tricky, some of the dimensions in the plans are wrong, and if some could do it over, they would have used armpit scoops. I think they come from aerocad There are lots of planes flying with NACA as the cooling method. It may not be wrong. 3. If i go with plans naca, anything I should know other than what plans say about it? This is all my opinion, others may disagree with me, I may be quite wrong, but I'll offer them, and others can disagree all they want, and someone may convince me to do things differently. The NACA scoop allows the cooling air an efficient entry point into the motor. The motor needs a certain amount of air to interact with the surface of the motor, to provide cooling. Running the air through the various baffles and fins, and all allows some control of what air does cooling, at a cost (drag). The air needs a way in, and a way out to work, the NACA scoop provides a low drag entry point, and the openings in the back of the motor offer an exit point for the air that made it in. Some people wrongly open up some of the baffles thinking they will reduce the drag, or improve cooling. If lots of air comes into the cowl, and flows straight out, it may or may not provide any cooling. There can be dead spots of air (ie between cylinders) where hot air will accumulate, and other areas where cold air will flow by. From: "Todd Carrico" Subject: COZY: Re: naca scoop or armpits Date: Mon, 8 May 2000 17:00:17 -0700 > Time to build the NACA scoop. What does that stand for anyway? > I read the archives and some say it's tricky, some of the dimensions in the > plans are wrong, and if some could do it over, they would have used armpit > scoops. I think they come from aerocad > 1. what are they. > 2. are they recommended over the plans naca > 3. If i go with plans naca, anything I should know other than what plans say > about it? > NAACP scoops work of capturing boundry layer air and providing a place to slow it down without spilling over and creating drag. The arm pit scoops work by taking air from the high pressure area in the junction between the fuselage and the wing. Jeff Russell may have to step in here, but I remember reading something that said to the effect "Arm pit scoops are simpler to make than the NACA scoop, and that it was difficult to mold it into the tub". He is offering a molded fuselage, but I am not sure if he figured out how to mold in the duct or if it part of post processing. In defense of the plans, the NACA scoop seems to work. If you go this route then you can use the plans baffle which have gotten lots of praise. If you go with the arm pit scoops you need to use the baffle plans for the AeroCanard installation, but I am not sure if an IO-360 is baffled the same as an OF-360. I think the real story is what you do with the air after you get it into the engine compartment, and slowed down enough to cool, but that is beyond the scope here. tc From: CozyBuilder@aol.com Date: Fri, 12 May 2000 21:45:58 EDT Subject: COZY: naca joggles Are the joggles only on the straight part of the bulkhead and scoop? or, do they continue around the curve of the L.G. bulkheads? Jay #858 Escondido CA Starting Ch 7 NACA scoop My Website http://www.cozybuilder.com From: jhocut@mindspring.com Date: Fri, 12 May 2000 23:35:17 -0400 Subject: Re: COZY: naca joggles > Are the joggles only on the straight part of the bulkhead and > scoop? or, do they continue around the curve of the L.G. bulkheads? As I recall, approximately halfway around the curve is about right. You'll want the joggle (for installing the LG cover) to extend to near the midpoint of where the gear legs are going to be. If by chance you extend it too far it's no big deal to fill later. Jim Hocut Cozy Mk IV # 448 - stuck on ch. 19 awaiting completion of my yearly spring chores