Another builder is having problems with his magnetic compass - very large errors. He asked me if I knew anything about degaussing the roll bar. I have been saving info on degaussing for a number of years, as it is a potential problem that I may need to deal with once my aircraft is finished. I decided to put this info on my web page, as some other builders may find it useful.
First, the Sacramento Sky Ranch has some apparently good info on their web site - Degauss Instructions.
I've collected the following information from a variety of e-mail lists, but I have never actually used any of it. So I have no idea whether any of it is good stuff, or complete garbage. Use at your own risk. If you use any of it, I'd appreciate it if you let me know what worked and what didn't.
Read on for the collection of info.
Date: Sun, 9 Mar 1997 01:32:49 -0500 (EST)To: This email address is being protected from spambots. You need JavaScript enabled to view it.: Re: RV-List: Magnetic Roll Bar Brace==> RV-List message posted by: KBoatri144Some avionics shops have degaussing equipment which can be used on yourairframe. A friend of mine had the same problem with his sliding canopyRV-6a and used a degausser to solve the problem. I can verify that hiscompass was way offbefore degaussing, and now it's almost perfect. Kyle Boatright ===================================================================Date: Sun, 09 Mar 1997 12:06:11 -0800To: This email address is being protected from spambots. You need JavaScript enabled to view it.: Re: RV-List: Magnetic Roll Bar Brace==> RV-List message posted by: Bud NewhallTed French wrote:> In considering ways to demagnetize this> brace I thought of wrapping it with many turns of wire & introduced an> alternating current through the wire, thus erasing any residual> magnetism in it. > Ted French> RV-6A C-FXCS 60+ hoursTedCheck out Sacramento Sky Ranch http://www.sierra.net/skyranch/ They rent a degaussing probe for $75 a week. Also read the article theyhave posted on how to demagnatize your aircraft. Very informative.Bud Newhall-- __|__ __|__ ____(+)____ ____(+)____ ' ' ' '===================================================================To: "This email address is being protected from spambots. You need JavaScript enabled to view it.'" Subject: RE: RV-List: Magnetic Roll Bar BraceDate: Tue, 11 Mar 1997 23:16:49 -0700==> RV-List message posted by: "Darrell L. Anderson" Radio Shack has a bulk videotape eraser that "should" work as a degaussingtool. It works good on bulk erasing of computer disks, too! Just pullthe trigger, work it around the object, and slowly pull it away beforereleasing the trigger.D. Anderson===================================================================To: Subject: Re: RV-List: Vertical Card CompassesDate: Sun, 4 Jan 1998 19:53:19 -0600--> RV-List message posted by: "Dennis Persyk" ----------> To: This email address is being protected from spambots. You need JavaScript enabled to view it.> Subject: Re: RV-List: Vertical Card Compasses> Date: Sunday, January 04, 1998 5:42 PM> > --> RV-List message posted by: Denny Harjehausen > >> Does twisting help rid the magnetic field from electric wires? Is> there a distance from the compass for wires that would help?> > Happy building & Merry Flying!> denny-->> RV-6> Denny, Twisting the wires will only help if the ground (or minus) and plus arerunning together; a couple of turns per inch will suffice. Actuallyrunning them parallel together is enough, but twisting will ensure thatthey don't move around with vibration. However you still need to haveseveral inches separation from the compass because the cancellation is notcomplete up close.The magnetic field will be proportional to the current, so high currentwires (landing lights) are the worst.The field strength will fall off as 1/r, where r is the distance from thewire. If the wire starts out 1 inch from the compass and you move it 2inches away, the strength is halved; if you move it three inches away it isreduced to 1/3. The problem is that the earth's magnetic field is pretty weak compared tothe fields produced by current-carrying conductors or accidentallymagnetized parts. Many of the weldments in my 6A came magnetized. Theycan easily be unmagnetized with a degaussing coil, purchased or home made. The compensating magnets in compasses can correct for tiny, constantmagnetic fields or effects of ferrous metal, but larger effects just swampout the earth's signal and then you have unreliable compass readings.Dennis Persyk 6A instrument panelBarrington, IL===================================================================Date: Mon, 14 Feb 2000 08:59:28 +1100To: This email address is being protected from spambots. You need JavaScript enabled to view it.: RV-List: De-gaussing, Roll bars and Compasses--> RV-List message posted by: Dr Leo Davies Dear List,This is a note about a problem solved. It seems nobody else has had theproblem but I am so please with solving it that I felt like leaving anote in the archives.I had a problem with my compass correction card. It had things writtenon it like,"For 360 degrees steer 240 degrees" I could see that IFR renewals weregoing to be a problem. Can't you just see the examiner being pleasedwith a 110 degree difference between the DG and the compass.The problem was clearly the roll-over bar in my RV6A with slidingcanopy. How it got turned into a big bar magnet I don't know but smalltool could be left parked on its underside.An electronics qualified person (thanks Karl) suggested degaussing theroll bar and loaned me a thing like a magic wand used for de-gaussingelectronic bits. I waved it at the roll bar and it reduced my deviationto about 60 degrees. Still not good.One day...... I noticed a man in a hanger testing the armature from agenerator (alternator... who knows). He was using a "Snap-On Tools"armature tester but he called it a "growler" because of the impressive50 hz hum it made (On your side of the big pond this would be a 60 hzhum). After studying this thing for a while I determined that it wasputting out a rapidle alternating magnetic field like Karl's wand but onsteroids. It also had attractive open jaws that could be slid along aroll bar.After determining that the roll bar needed protecting with masking tape(the growler also bites anything paramagnetic) I moved the growler alongthe roll bar (after removing the compass....hemm hemm).Problem solved ... just like that. My compass now reads withing 2degrees of heading all round the rose.So...... if'n your local magnetic field is stronger than the Earths mayI recommend (shameless plug) borrowing a "Snap-On" armature tester.Sorry for the long post.Cheers,Leo Davies.===================================================================Date: Mon, 14 Feb 2000 09:21:06 ESTSubject: Re: RV-List: De-gaussing, Roll bars and CompassesTo: This email address is being protected from spambots. You need JavaScript enabled to view it.> RV-List message posted by: JRossOne simple, inexpensive way to check for unknown magnetic fields can be accomplished quite easily. A steel paper clip can be bent into an "L" shape and taped to a thread. The single wire is taped to the thread with a small piece of scotch tape. The thread can be held up and the paper clip moved near any steel component in the cockpit, such as the canopy frame. The paper clip will point to any magnetized object. Be cautious as this must be done in a hangar with no drafts, and be certain that you do not magnetize the paper clip by testing the process (practicing) near any magnet.Hope this helps,Jon Ross 80094===================================================================To: Subject: RE: RV-List: degaussingDate: Sun, 14 Oct 2001 07:29:55 -0600--> RV-List message posted by: "John & Teresa Huft" Ask your local machine shop. After they use the magnetic chuck on thesurface grinder, they often need to degauss the part. It is a cube, 18inches on a side, that hums ominously.John-----Original Message-----To: This email address is being protected from spambots. You need JavaScript enabled to view it.: Re: RV-List: degaussing--> RV-List message posted by: Finn Lassen Radio Shack used to sell a tape eraser. If they still do, that *might* work.The more powerful the better. You may have to work it for a long time.Remember to turn it on at a distance, then slowly move it all the way to themetal, all over, around and along it, and then *slowly* move it away to agood distance before you turn it of.Works well on TVs, monitors, This email address is being protected from spambots. You need JavaScript enabled to view it. wrote:> --> RV-List message posted by: czechsix>> How do I degauss the rollbar for my RV-8A? I'm about ready to attach it> to the fuselage....wondering if it would be easier to get it degaussed> before it's attached? Who would have the necessary tools/equipment to do> such a thing? If it's not too expensive and helps my compass to read> more accurately, I figure it's worth it....>> Thanks,>> --Mark Navratil> Cedar Rapids, Iowa> RV-8A fuselage>>===================================================================Date: Sun, 14 Oct 2001 09:09:30 -0500To: This email address is being protected from spambots. You need JavaScript enabled to view it.: Re: RV-List: degaussing--> RV-List message posted by: Charlie and Tupper England Find someone who works for a TV or computer repair shop.Picture tube degaussers are coils of wire, ~1' in diameter.MUCH more powerful than tape head degausers, but if youdon't use proper technique, you can turn the roll bar into afairly strong magnet. Get the tech to do your degaussing foryou, or be sure you understand the instructions on how touse the tool.Charlie===================================================================To: This email address is being protected from spambots. You need JavaScript enabled to view it.: This email address is being protected from spambots. You need JavaScript enabled to view it.: Mon, 1 Apr 2002 07:52:49 ESTSubject: [rv8list] Re: Compass swingScott:I suspect the roll bar may be magnetized. If you can find a degaussing unit this may work. Or the use of compensating magnets that can be purchased as a kit. I had a similar problem with my V-35 Bonanza, it turned out the control column was magnetized. This can happen easily, all it takes is a live wire to touch the steel (for a second) part in question. Degaussing the control column worked fine, the problem went away. The technique used at the Piper factory in steel tube airplanes was to intentionally spark a tube in the fuselage somewhere in order to balance the magnetic field. This was mentioned in my Cub Club newsletter recently, but it is the same theory. Try making a homemade sensor with a paper clip and thread, this will most likely reveal the magnetic culprit. Hope this helps. Best,Jon>===================================================================To: From: "Rick Jory" Date: Tue, 17 Jun 2003 13:29:57 -0600Subject: Re: [rv8list] Mag CompassA fellow RV builder made a degaussing "coil". Basically, this consistedof a long, very very long length of insulated wire that's coiled up likeyou would a garden hose . . . I don't know how many "coils" he had, butthe resulting bundle of wire was about two inches in diameter and thecircle that the coil made was about 12 inches in diameter. The wire wasterminated to a standard wall outlet plug. You basically plug this intoa 115 v outlet . . . you can feel the wires vibrate but they don't gethot (due to the length of wire) . . . and you simply pass this from oneside of the roll bar across to the other side (i.e. going from the leftside of the cockpit over to the right side). And that's all there is toit. You keep the coil a couple of inches from the roll bar, but I don'tthink this is that critical. For what it is worth, I first ran a BoyScout compass around the roll bar to see if it was magnetized . . . andthis really didn't show me much. So, just for kicks I tried the "coil". . . and this fixed the compass problems I was having. The compass wason the 8A's panel, upper left corner (panel mount, not on the glareshield).Good luck.===================================================================To: This email address is being protected from spambots. You need JavaScript enabled to view it.: Wed, 18 Jun 2003 07:50:24 -0400Subject: Re: [rv8list] Mag CompassHi All!Degausing coils are just inductors without any material to concentratethe field. (Such as steel in a transformer.) This means that the fieldsproduced are quite dispersed and you have to be careful not to magnetizesomething while you are operating these degausers.The way I was taught to operate one of these devices is as follows:1) apply power with the coil at right angles to the area you want todemagnetize and at least six feet away.2) Slowly turn the coil so that it is parallel with what you want todemagnetize and then slowly bring it close to the object.3) Move the coil in small circles and slowly withdraw it until you aresix feet away.4) Turn the coil at right angles again and disconnect the power.Note 1: If you want to magnetize something, just place it near the coiland turn off the power. (Handy if you need to magnetize a tool; you candemagnetize by following the above steps.)Note 2) For those of you who are visual people, you can operate thedegausing coil near your color TV. (TV on!) Then you can see the prettypatterns that the coil produces and see how far away it actually has tobe before it does not affect the TV. (All color TV's have a smalldegauser built in; that's what produces that brief hum when you turn onthe set. They use a circuit that reduces the current flow to the coilwith time to emulate moving the coil away from the set.)Hope this helps and doesn't confuse!Daniel===================================================================From: Stephen CrowTo: This email address is being protected from spambots. You need JavaScript enabled to view it.: Thursday, June 19, 2003 7:50 AMSubject: Re: [rv8list] Degaussing coilHere's a few degausing coil URL's........Google rides again!Steve C.http://www.oscarcontrols.com/degauss/ -homebrew -cheapesthttp://www.starkelectronic.com/gc9317.htmhttp://www.elexp.com/cpt_1dgc.htmhttp://www.toaei.com/Home_Appliances/home_appliances_degaussing_coil.htmhttp://www.jensentools.com/product/group.asp?parent_id=2595http://www.twobits.com/degauss.html+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ----- Original Message ----- From: Joel Harding To: This email address is being protected from spambots. You need JavaScript enabled to view it. Sent: Thursday, June 19, 2003 12:29 AM Subject: [rv8list] Degaussing coil I hooked my coil up to 115 volts, but instead of just a vibration, it immediately emitted a loud buzzing noise and started to become warm, at which time I discontinued the operation, and decided to consult you guys again. I'm speculating that my coil probably doesn't have as many windings and doesn't provide enough resistance. So what would you recommend to tame this rattlesnake ? Joel Harding
