Date: Tue, 9 Dec 1997 13:37:13 -0600 (CST) From: Tom Brusehaver Subject: COZY: Tolerances What tolerances are folks using as "acceptable"? I ask, having just finished step 5 in chapter 5 where it keeps refering you to figure 5 to make sure the lower longeron is attatched at the right place. I use several rulers, 6 and 12 inch steel, 3ft aluminium, Stanley tape measure (measures in 1/10's), and probably others. Measuring rulers against rulers, I have tolerances of up to 1/8" over a couple feet. I remember the one LG bulkhead with all the measurements on it was really far off (almost 1/4" for one of the measurements, and not the same in X vs. Y). The book says use felt tip markers, well some of mine are starting to mash down, and now they are probably 3/16" when they make lines (I am using pencils more and more). I guess I am leaning toward 1/8" is close enough, is it? From: Marc J. Zeitlin Subject: COZY: Tolerances (fwd) Date: Tue, 9 Dec 97 15:30:20 EST Tom Brusehaver writes: >What tolerances are folks using as "acceptable"? This is an excellent question, and one that has no general answer that I've ever been able to find. It's one of the infuriating things about the V.E./L.E./COZY plans from an engineering standpoint. >........ Measuring rulers >against rulers, I have tolerances of up to 1/8" over a couple feet. Wow. I've used a 25 ft. tape for the whole project, along with one carpenter's square. It never occurred to me to verify either of their accuracies, or check them against one another. >The book says use felt tip markers, well some of mine are starting to >mash down, and now they are probably 3/16" when they make lines (I am >using pencils more and more). Pencils (sharp) are good, or get the finest point permanent markers you can find and throw them away when the tip gets at all mashed. In 3 years I've spend $5 on markers - it's worth it. >I guess I am leaning toward 1/8" is close enough, is it? I won't make a recommendation for anyone else, but I'll tell you what I do. I try to get everything dead nuts to within the thickness of the line on the tape measure/square. That's about 0.010", as far as I can tell. However, when leveling wings, fuselages, or measuring large distances for squaring things up, I'll accept measurements within 1/32". I'll bet that this is tighter than any certified aircraft is built to. With the tape measure and/or a water level, this is doable with a few iterations. -- Marc J. Zeitlin Email: marcz@an.hp.com From: cdenk@ix.netcom.com Date: Tue, 9 Dec 1997 16:59:35 -0600 (CST) Subject: Re: COZY: Tolerances (fwd) Not only basic tolerances, but measure, adjust, remeasure, going around in circles till its as close as you can make it, and then come back the next day and do it again with important items. Date: Tue, 09 Dec 1997 19:03:01 -0800 From: "LCDR James D. Newman" Organization: INFINITY Aerospace http://www.flash.net/~infaero Subject: COZY: Re: Tolerances Hi Marc, Tom and All, >>Tom Brusehaver writes:<< >>What tolerances are folks using as "acceptable"?<< >Marc Zeitlin wrote:< >This is an excellent question, and one that has no general answer that I've ever been able to find. It's one of the infuriating things about the V.E./L.E./COZY plans from an engineering standpoint.< The following are a few tolerances (that came from RAF) I've come across in an Army airworthiness study of the _Long-EZ_ for their possible future needs: Eppler 1230 Main Wing: Incidence +/- 0.5 degrees Sweep +/- 1.1 degrees of each other Leading edge FS of the wing tip FS 156.0 +/- 1.0" (with a wing tip FS tolerance of +/- 1.0", this is one of the many reasons to put your winglets on latter after the wings have been mounted since the winglet chord tolerance of the 'A' and 'B' dimensions in the plans is +/- 0.05".) Ailerons Trailing Edge UP 2.1" +/- 0.3" TEU Trailing Edge DN 2.1" +/- 0.3" TED Canard (GU) Incidence 0.6 degrees +/- 0.3 Leading edge FS location FS 18.6 +/- 0.3" Elevator (GU) Trailing Edge UP 20 degrees +2 TEU Trailing Edge DN 22 degrees +/- 2 TED Rudders (the original square) Deflection each 6" +/- 0.5" Fixed Main Gear Toe-In 0.25 - 0.5 degrees per side Axle FS location FS 110.5 +/- 1.0" Info: I've measured the Roncz canard incidence with my inclinometer at ~3.87 degrees. >>........ Measuring rulers against rulers, I have tolerances of up to 1/8" over a couple feet.<< >Wow. I've used a 25 ft. tape for the whole project, along with one carpenter's square. It never occurred to me to verify either of their accuracies, or check them against one another.< >>The book says use felt tip markers, well some of mine are starting to mash down, and now they are probably 3/16" when they make lines (I am using pencils more and more).<< >Pencils (sharp) are good, or get the finest point permanent markers you can find and throw them away when the tip gets at all mashed. In 3 years I've spend $5 on markers - it's worth it. >>I guess I am leaning toward 1/8" is close enough, is it?<< There's a cute saying that has been floating around for years concerning scratch built aircraft: Measure it to the thousandth (X.XXX); mark it with a felt pin; cut it with a chain saw. HTH. Infinity's Forever, JD From: lschuler@cellular.uscc.com Date: Tue, 09 Dec 97 21:11:32 -0600 Subject: COZY: Tolerances (fwd) --simple boundary Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Marc wrote: >snip >Wow. I've used a 25 ft. tape for the whole project, along with one >carpenter's square. It never occurred to me to verify either of their >accuracies, or check them against one another. Marc, talk to the folks in your machine shop... Most all tapes from the same manufacturer will be the same; but if you buy one from a diferent manufacturer, compare before using. Same is true for most any measuring device unless it's absolutly tracable to the National Bureau of Standards (ie. Expensive). Kind of like looking at your watch and then three others and noting that none are the same. Depends on the source. I have seen a number of diferences between linear measuring devices over the years. Was building some cabinets for my sister's house; measured using her tape; went home and built the cabinets with my tape; time to instal, they wouldn't fit the opening..... Took a while to figure out what happened, but over an 8 Ft length, the two tapes were almost a 3/8" different! Good quick check of a new tape is with a machinist's dial-micrometer over a 2 or 3 inch span "AND" compare it to the one you are replacing. When I first ordered parts from Wicks I bought two decimal tapes at the same time and stuck one in a drawer. It will only be needed "when" (not if) I break the first one. Per Murphy it will happen when I really need it. FWW: My decimal tapes are from Stanley and so is the one I use around the house and built my shop with; they both match. Can't say if they are "True" but at least I'll be able to get the plane out of the shop when it's done. :-) Larry Schuler MK-IV Plans #500 --simple boundary Content-Type: text/plain; charset=US-ASCII; name="RFC822.TXT" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="RFC822.TXT" Received: from gatekeep.uscc.com by cellular.uscc.com (ccMail Link to SMTP R8.00.01) ; Tue, 09 Dec 97 14:36:14 -0600 Return-Path: Received: from www.uscc.com (www.uscc.com [204.179.101.2]) by gatekeep.uscc.com with ESMTP id PAA12966 for ; Tue, 9 Dec 1997 15:29:46 -0500 (EST) Received: from palrel1.hp.com (palrel1.hp.com [156.153.255.235]) by www.uscc.com with ESMTP id OAA15547 for ; Tue, 9 Dec 1997 14:30:41 -0600 (CST) Received: from hpwarhw.an.hp.com (hpwarhw.an.hp.com [15.57.193.122]) by palrel1.hp.com (8.8.6/8.8.5tis) with SMTP id MAA15749 for ; Tue, 9 Dec 1997 12:32:52 -0800 (PST) Received: by hpwarhw.an.hp.com (1.37.109.8/15.5+IOS 3.22) id AA00519; Tue, 9 Dec 1997 15:30:22 -0500 Received: by hpwarhw.an.hp.com (1.37.109.8/15.5+IOS 3.22) id AA00513; Tue, 9 Dec 1997 15:30:21 -0500 From: "Marc J. Zeitlin" Message-Id: <9712092030.AA00513@hpwarhw.an.hp.com> Subject: COZY: Tolerances (fwd) To: cozy_builders@hpwarhw.an.hp.com (Cozy MK-IV Builders) Date: Tue, 9 Dec 97 15:30:20 EST Mailer: Elm [revision: 70.85] Sender: owner-cozy_builders@hpwarhw.an.hp.com Precedence: bulk Reply-To: "Marc J. Zeitlin" --simple boundary-- Date: Tue, 09 Dec 1997 21:37:32 -0600 From: Cozy_driver Organization: Composite Parts Subject: Re: COZY: Tolerances (fwd) Marc J. Zeitlin wrote: > > Tom Brusehaver writes: > > >What tolerances are folks using as "acceptable"? > > This is an excellent question, and one that has no general answer that > I've ever been able to find. It's one of the infuriating things about > the V.E./L.E./COZY plans from an engineering standpoint. > > >........ Measuring rulers > >against rulers, I have tolerances of up to 1/8" over a couple feet. > > Wow. I've used a 25 ft. tape for the whole project, along with one > carpenter's square. It never occurred to me to verify either of their > accuracies, or check them against one another. > > >The book says use felt tip markers, well some of mine are starting to > >mash down, and now they are probably 3/16" when they make lines (I am > >using pencils more and more). > > Pencils (sharp) are good, or get the finest point permanent markers you > can find and throw them away when the tip gets at all mashed. In 3 years > I've spend $5 on markers - it's worth it. > > >I guess I am leaning toward 1/8" is close enough, is it? > > I won't make a recommendation for anyone else, but I'll tell you what I > do. I try to get everything dead nuts to within the thickness of the > line on the tape measure/square. That's about 0.010", as far as I can > tell. However, when leveling wings, fuselages, or measuring large > distances for squaring things up, I'll accept measurements within 1/32". > I'll bet that this is tighter than any certified aircraft is built to. > With the tape measure and/or a water level, this is doable with a few > iterations. > > -- > Marc J. Zeitlin Email: marcz@an.hp.comWhen measuring, avoid stacking measurements. In other words if you measure from F0 to F22, don't start againt at F22 to measure to F28. Got the Idea? Go back to F0 each time and you will not be adding those little errors. Establish the fuselage centerline early on. Marc's interpretation of allowable tolerances should work great. Date: Tue, 09 Dec 1997 20:34:02 -0800 From: "LCDR James D. Newman" Organization: INFINITY Aerospace http://www.flash.net/~infaero Subject: COZY: Re: Tolerances Hi Larry and All, >When I first ordered parts from Wicks I bought two decimal tapes at the same time and stuck one in a drawer. It will only be needed "when" (not if) I break the first one. Per Murphy it will happen when I really need it.< Eventually, the little hook tab on the end of the taper measure elongates making for inaccurate measurements, or comes off. So, for very accurate measurements that I'm concerned about, I start my measurements using the "1" instead of hooking the tab over the end of something and relying on the end of the tape measure being accurate, just add 1" to your measurement - and don't forget to add the 1". As they say, measure twice (sometimes 3 times), cut once. If I don't have an extra set of hands, I clamp the tape measure down with the "1" on the start point and of course, check that it did not move 2 or 3 times. Infinity's Forever, JD