From: Jim Hocut Subject: COZY: Load Testing Canard Date: Thu, 2 Apr 1998 21:35:43 -0500 I was having a discussion with a fellow builder who happens to be my EAA Tech Counselor. It was suggested that for the dual purpose of a warm fuzzy felling and education we might consider load testing my canard. We were thinking it would make for an interesting hands on exercise for an EAA chapter meeting (no John, you may not take this as a commitment - we're just in the thinkin' about it stage). A couple of questions: 1) From the weight & balance spreadsheet I downloaded (thanks for making this neat stuff available on your web page Marc), I get a load of about 620 lbs. on the canard at max gross weight (2050 lbs.) and max forward CG (96 inches). Then, assuming a max load factor of 3 g's the canard will be expected to support 1860 lbs. Does all this sound reasonable? 2) What are some specific procedures for performing the load test? I assume that it would get more sand bags further inboard, but what would be the ratio between the inboard load to outboard load? Would it be a linear transition? I'm also under the impression that there would be no load placed in the center section, where the canard is enclosed in the nose section. If anyone else has done this, about how much deflection can be expected? Thanks, Jim Hocut jhocut@mindspring.com Date: Thu, 2 Apr 1998 22:59:13 -0500 From: Bill Theeringer Subject: COZY: Canard Testing Jim; Burt did a test like you describe to a "defective" canard around 1984. = He used 25 lb. lead shot bags and laid them cross ways on the canard from th= e attach points out to the ends. The second "course" was one or two bags shorter than the previous on the inboard sides so the whole thing approximated a slope with more bags toward the ends. Each bag was laid carefully and symmetrically on either side and the canard ends were measured for deflection and the G forces calculated. I believe the deflection was somewhere around 18 inches with 6 or 7 layers at the ends and 12 G's calculated load at the time of fail. I video taped the entir= e thing and the tape is around here some where. The only problem is I did = it in Beta. That was the format at that time that was supposed to survive wasn't it? I can loan it to you if you are interested. I think is about= an hour long. = Regards Bill Theeringer N29EZ Composite Aircraft Accessories HOME: 805-964-5454, SHOP: 805-964-5453 E Mail: Composite_Aircraft_Accessories@Compuserve.com PO Box 21645 Santa Barbara, CA 93121 Serving Sport Aviation=92s Cabin Heating Requirements Since 1991. Date: Fri, 03 Apr 1998 13:27:51 +0200 From: Chris van Hoof Subject: Re: COZY: Load Testing Canard Hi Team & Jim Hocut, Thanks for raising this issue. We (in South Africa) have to prove, on every first one (type) of Kit that the Main Spar as well as the Canard (in our case) can handle the design or published loads. All this is neccessary if you cannot provide our CAA (=FAA) with calculations of the theoretical loadings. Interesting the preferred method of testing around here is by means of cement bags. Each having an accurate mass of 50 Kg. Our Chapter President of 1996 (the late Marin Clark) was fortunately an aeronautical engineer. He advised that this was packed in a trianglar fashion on a KR2 derivative.(he worked out exact spreads) During the exercise, the Europa designer came to have a look, and recon'd that what we were doing was all wrong....his opinion was that the load imposed was too great at the calculated weight of 6G (in this case) in that while you are packing ever so slowly, you increase the load, but you do "drop" the bag (even one inch), this increases the load, he went on to say that by the time it was all packed and done, pictures taken, checked and started to offload, one had seriously overstressed the item being tested. His opinion was that if you stressed to any max., in real life this would be for a max of 30 seconds (i think i remember this figure) any more is too much. He also said he would prefer not to use an item that had been checked to its max. load in an airplane he was going to fly in. This is only my remembered version of happenings and Any mistake in the langauge used, or the value of the above is my fault...ie don't go knocking others of the pedestals on which i put them. Thanks. Chris #219 in SA see also http://users.iafrica.com/c/cv/cvh > EAA Tech Counselor. It was suggested that for the dual purpose of a > warm fuzzy felling and education > > 1) From the weight & balance >< a load > of about 620 lbs. on the canard at max gross weight (2050 lbs.) and max > forward CG (96 inches). Then, assuming a max load factor of 3 g's the > canard will be expected to support 1860 lbs. Does all this sound > reasonable? > 2) What are some specific procedures for performing the load test? I > assume that it would get more sand bags further inboard, but what would From: SBLANKDDS Date: Fri, 3 Apr 1998 08:24:54 EST Subject: COZY: Canard Testing I am not an engineer (dentist), but isn't loading the canard wing ends with weights, testing only the negative G's??? What value is that info? In real function, the canard is lifting up (not weighted down), with 1,2,3 or more G's pulling down on the Lift Tabs and stabilizing pins??? Example, a fully loaded aircraft in a 60 degree bank, is 2G's pulling down on the lift tabs, while the canard wing is developing lift at the outboard portions? Would a more accurate test be to support the canard, and then load the fuselage as in real flight to simulate 1,2,3 G's. It seems that a test of the Lift Tabs would be just as critical as the Ultimate Strength of the canard in Negative load???? It would be interesting to know the limits to the canard spar, but also know when the lift tab fails either at the bolt or the attachment to the spar.....This testing should be done by someone willing to sacrifice their canard!!! I agree that it would NOT be safe to fly in an aircraft that was tested to the limit of the part. Parts that fly should only be tested to the designers intended use (non-destructive testing), for example +4G's -2G's or whatever the range is. My $00.02 Steve Blank Cozy Mark IV #36 From: Marc J. Zeitlin Subject: COZY: Canard Testing Date: Fri, 3 Apr 98 10:02:48 EST Steve Blank (the dentist) correctly asks: >...... isn't loading the canard wing ends with >weights, testing only the negative G's??? What value is that info? It does have some value, but I don't think (I hope) that's what Jim was proposing. The canard (wing) does have to be able to withstand negative G's, and while the spar caps are not symmetric, you would get some useful information about the strength of the canard (wing) from loading in this manner. However......... > Would a more accurate test be to support the canard, and then load the >fuselage as in real flight to simulate 1,2,3 G's. Yes, but this is difficult to do (support the canard as in real flight, I mean). What's normally done is to turn the aircraft upside down, support the fuselage, and then load the BOTTOM of the canard (wing) with sandbags (or lead shot, or whatever heavy things you've got laying around) until you've got the correct loading profile for the positive G load that you've determined you'd like to test to. Usually you try to obtain a lift distribution that's identical to what the surface would see in real operation - this is normally close to elliptical, but the distribution can be constant from the fuselage to the tip to be very conservative (meaning that this will impose MORE of a load than would really be seen in service). The loading that Burt used on the supposedly defective canard that went to 12 G's was approximately elliptical (by reducing the # of bags toward the tips). > It seems that a test of the Lift Tabs would be just as critical as the >Ultimate Strength of the canard in Negative load???? It would be interesting >to know the limits to the canard spar, but also know when the lift tab fails >either at the bolt or the attachment to the spar..... You're absolutely right - it does no good for the canard to be able to withstand 12 G's if the lift tabs let go at something lower (other engineering considerations notwithstanding - like stiffness, torsional resistance, etc.). However, with the plane upside down and sandbags on the canard, you'll get the lift tab testing for free :-). >.....This testing should be >done by someone willing to sacrifice their canard!!! L. Wayne Hicks has suggested that we (as a group) chip in about $5/person (from over 300 people) to buy a new canard from a vendor and then test it to destruction. > I agree that it would NOT be safe to fly in an aircraft that was tested to >the limit of the part. Parts that fly should only be tested to the designers >intended use (non-destructive testing), for example +4G's -2G's or whatever >the range is. Kind of. It depends upon what limits the part has been tested to. You've got the "design limit" (what the part is expected to see in worst case operating conditions), and then you've got the "ultimate" limit. Usually, the "ultimate" limit is the "design limit" multiplied by a safety factor of 1.5, or some other number determined by the confidence level of the designer (or the FAA, for certified planes). So, if an aircraft had been designed to withstand a G loading of 4 positive and 3 negative, the ultimate loads that you would test to would be 6 positive and 4.5 negative. For homebuilt aircraft, finding the "design limit" is not always a trivial endeavour :-). We must also remember that it's based on _design_ gross weight, and since we each set our own gross weight ......... I wouldn't have any problem whatsoever flying in a plane that had been tested to the "design limit", but I wouldn't be so comfortable in a plane with components that had seen the "ultimate limit". -- Marc J. Zeitlin Email: marcz@an.hp.com Date: Fri, 03 Apr 1998 09:24:12 -0800 From: hrogers@slac.stanford.edu (Howard Rogers) Subject: Re: COZY: Canard Testing >Jim; > >Burt did a test like you describe to a "defective" canard around 1984. He >used 25 lb. lead shot bags and laid them cross ways on the canard from the >attach points out to the ends. The second "course" was one or two bags >shorter than the previous on the inboard sides so the whole thing >approximated a slope with more bags toward the ends. Each bag was laid >carefully and symmetrically on either side and the canard ends were >measured for deflection and the G forces calculated. I believe the >deflection was somewhere around 18 inches with 6 or 7 layers at the ends >and 12 G's calculated load at the time of fail. I video taped the entire >thing and the tape is around here some where. The only problem is I did it >in Beta. That was the format at that time that was supposed to survive >wasn't it? I can loan it to you if you are interested. I think is about >an hour long. > >Regards > >Bill Theeringer >N29EZ > >Composite Aircraft Accessories >HOME: 805-964-5454, SHOP: 805-964-5453 >E Mail: Composite_Aircraft_Accessories@Compuserve.com >PO Box 21645 Santa Barbara, CA 93121 >Serving Sport Aviation=92s Cabin Heating Requirements Since 1991. Bill, you and I must have been at this same event. I remember a couple of more details about it: The canard was, indeed, supported upside down, so the loading could simulate positive g. The method of support was a simple angle iron frame with mount points for the canard (no need to turn your whole airplane upside down). Unfortunately, there was unsufficient room for deflection provided by this frame, and when the canard bent far enough, it contacted the frame, on one sied, and formed a sharp fulcrum, which was the point of failure, and stopped the test at that point. If you witnessed the same event I did, your video tape should show this, as well as some of the shot bags sliding off (due to the slope of the severly deflected canard). Though 12 gs was reached, it was generally agreed that more would have been achievable, had the frame been a little better constructed to avoid interference. It was also interesting to note that the mode of failure was not catastrophic (like snapping completely off, for example). Hard to say if such a failure would have been possible to fly home from, but it would be better than snapping completely off! Bottom line, for me, was that this canard was hell for stout, and I won't worry about snapping MINE off! I'm not sure why we are considering testing these things to destruction when they are so obviously "overbuilt". Howard Rogers --A&P 2005148 Date: Fri, 03 Apr 1998 13:32:27 -0500 From: Paul Krasa Subject: Re: COZY: Load Testing Canard I am not sure I agree with your statement. Micro cracking of the matrix is normal in composite structures. The strength of a composite in tension comes from the fiber, not the matrix. The thing to worry about is delaminations and fiber breakage. Paul Long EZ 214LP At 13:04 4/3/98 EST, KEN SARGENT wrote: > > While performing the load test, add load slowly and listen to the > canard with a mechanical stethoscope. If you hear a sound like rain > on a tin roof, this is resin matrix cracking, and will occur at the > fatigue limit for the structure. It also means some damage has > occurred. > > Ken Sargent > Cozy #555 > ken_sargent@wda.disney.com > > >______________________________ Reply Separator _________________________________ >Subject: COZY: Load Testing Canard >Author: Jim Hocut at DISNEY-WDW-INTERNET >Date: 4/2/98 9:47 PM > > >I was having a discussion with a fellow builder who happens to be my EAA >Tech Counselor........... >.......It was suggested that for the dual purpose of a warmon? I'm also >under the impression that there would be no load placed in the center >section, where the canard is enclosed in the nose section. If anyone >else has done this, about how much deflection can be expected? > >Jim Hocut > > > > > > > From: "Nat Puffer" Subject: Re: COZY: Canard Testing Date: Fri, 3 Apr 1998 11:51:42 -0600 Before you all start busting canards, you should take into account that t= he fuselage is a lifting body, and supports more weight than a Long EZ, because it is wider. Also, you should get a loading schedule. It would be wrong to put more weight per sq. ft. at the tips. That's where the spar c= ap is the thinnest, remember, and also in normal flight, some of the lift is spilled off the tip of the canard. Also, you should be very careful what kind of a frame you build. If it is not properly built, to give a little = as the canard is loaded (like the fuselage does) the lift tabs could fail as= a result of a twisting motion. When all is said and done, if the testing isn't done correctly, the results are meaningless.=20 Regards, Nat From: cdenk@ix.netcom.com Date: Fri, 3 Apr 1998 22:16:19 -0600 (CST) Subject: RE: COZY: Canard Testing Numerous countries including Germany require testing, the COSY newsletter about 5 years ago had articles and photos of the tests. I don't see any reason for testing unless the strength is in question, and then it definitely is easier to build a new part. This falls in the realm of reinventing the wheel. The design as drawn is well proven, both from load tests, and many hours of experience in the air. As has been slightly touched on the mail, to duplicate the actual air loading is difficult if not impossible, therefore any gravity load testing fall more into a political requirement that some official can hang his hat on. In building and bridge constuction, its not unusual to run full scale load tests. The accepted loading is 85% of the calculated failure load. The normal factor of safeties for concrete are 1.7 for live loads, and 1.4 for dead loads. A workmanship and material variability factor of .7 to .9 is also applied. Date: Mon, 06 Apr 1998 07:56:44 +0200 From: Rego Burger Subject: COZY: Canard Testing Well said NAT you beat me to it. I was getting worried with some of the thinking....Also what some folks don't realise is the stress from a "test" load can ruin the part beyond flight safety. The amount of stretch in the glass has it's limits. Glass / Foam cores can take more overload than metal and seem to be in shape...up to 8 times the normal load... try fly it and it can snap at an abrupt 2 G load...."But I loaded it to 8 G before"...aaaaah! Splat! Also because a test sample broke at 9 G does not mean you can fly up to 9 G every day....its a sign of the strength it can handle. Airframe life is more cyclic than a once off extreme load experience. We may get 80000 hrs of 2G cycles out of them...not that it's linear but for illustration: We may then get 40000hrs exposed to 4G cycle periods and only 10000 exposed to 6G cycles or more. Some aerobatic aeroplanes are limited to 2000hrs of aerobatics to give an example, while in "normal" class flying the limit is 40,000hrs. If you built your canard according to plans I would not dare place heavy sand bags on it if you intend to fly it! Take a plastic ruler and bend it back and forth...eventually it will snap. If you fit an accelerometer in your craft avoid anything above 2G anyway, If you want the thrill of High G flying build an aerobatic aeroplane. Rego Burger, web site: http://home.intekom.com/glen/rnb.htm (home e-mail) mailto:rnb@intekom.co.za RSA Date: Sat, 4 Apr 1998 13:06:32 -0800 (PST) From: "Mr. Radon" Subject: Re: COZY: Canard Testing On Fri, 3 Apr 1998, Nat Puffer wrote: > Before you all start busting canards, you should take into account that the > fuselage is a lifting body, and supports more weight than a Long EZ, > because it is wider. Also, you should get a loading schedule. It would be > wrong to put more weight per sq. ft. at the tips. That's where the spar cap > is the thinnest, remember, and also in normal flight, some of the lift is > spilled off the tip of the canard. Also, you should be very careful what > kind of a frame you build. If it is not properly built, to give a little as > the canard is loaded (like the fuselage does) the lift tabs could fail as a > result of a twisting motion. When all is said and done, if the testing > isn't done correctly, the results are meaningless. > Regards, Nat Have to agree absolutly with Nat on this issue. I think the best and cheapest way to go here is to get a University involved. Being a realitivly recent graduate, I know there are many bright, willing and capable students ready to tackle an interesting progect as this. We did a few tests at the CU. Talk to a few department heads in the Aero or ME wings and see if they are interested. My senior progect involved a design assignment with a small buisness, loads of knowledge and practical exp. gained. BTW - it fun to break things like that. ROY Date: Mon, 06 Apr 1998 10:15:52 -0400 From: "Johnson, Phillip" Subject: COZY: Load Testing Canard Jim Hocut Writes: Snip> 1) From the weight & balance spreadsheet I downloaded (thanks for making this neat stuff available on your web page Marc), I get a load of about 620 lbs. on the canard at max gross weight (2050 lbs.) and max forward CG (96 inches). Then, assuming a max load factor of 3 g's the canard will be expected to support 1860 lbs. Does all this sound reasonable? End< I think that the figure of 620 lbs is a bit high. Thats 50 lbs per square foot for the canard. That would make the wing loading on the main wing only 16.25 lbs per square foot when at gross weight. I.e. the canard is working 3 times harder than the main wing. It is understood that the canard should be working harder than the main wing but this number seems excesive. Before load testing it is important to determine an accurate wing loading. Nat, you are the designer and you must have completed the calculations, perhaps you could provide the data before someone breaks a perfectly good canard. Phillip Johnson From: Jim Hocut Subject: RE: COZY: Load Testing Canard Date: Mon, 6 Apr 1998 11:53:45 -0400 On Monday, April 06, 1998 10:16, Johnson, Phillip [SMTP:phillip.johnson@lmco.com] wrote: > > > I think that the figure of 620 lbs is a bit high. Thats 50 lbs per > square foot for the canard. That would make the wing loading on the > main > wing only 16.25 lbs per square foot when at gross weight. I.e. the > canard is working 3 times harder than the main wing. It is understood > that the canard should be working harder than the main wing but this > number seems excesive. Before load testing it is important to > determine > an accurate wing loading. Nat, you are the designer and you must have > completed the calculations, perhaps you could provide the data before > someone breaks a perfectly good canard. > > Phillip Johnson I didn't mean to say that we were definitely going to load test a canard, only that the idea was being discussed. Now I think we'll satisfy ourselves with watching that video of Burt loading up a canard to some humongous load factor before it snaps. That 620 lbs was arrived at before Nat pointed out that the fuselage (as a lifting body) provides some lift. Date: Mon, 6 Apr 1998 22:01:20 -0400 From: Bill Theeringer Subject: COZY: More Canard Loading I found the Missing Tape of the canard destruct test by Burt in July of 1985. There were 3 canards tested. The first was a canard that had too dry a layup. The second was the original canard from 79RA and the third was a flying canard from I don't remember where. The 25 lb. lead shot ba= gs were evenly distributed in rows of 10 per side starting inboard at about where the fuselage would be and working outboard until fail. The first canard failed with 69 bags per side which was over 12 Gs. The second canard had 59 bags per side when the bags all fell off. The third had about 60 per side when the battery in the cam corder died. As I remember= it broke in the center shortly after that with a loud bang. = The tape will go to Jim Hocut tomorrow and will make the loop before comi= ng back home. = Bill Theeringer N29EZ See our award winning Long EZ with Jim Newmans excellent retractable gear= at = http://www.flash.net/~infaero/infgear.htm Composite Aircraft Accessories HOME: 805-964-5454, SHOP: 805-964-5453 E Mail: Composite_Aircraft_Accessories@Compuserve.com PO Box 21645 Santa Barbara, CA 93121