Date: Mon, 10 Apr 1995 18:12:57 +1000 From: allana@interconnect.com.au (allana@interconnect.com.au) Subject: Aerocad elevators I recently posted a query regarding the gap between the trailing edge of my canard and the elevators. My concern was that there was some variability between the lower part of the trailing edge and the top of the elevators. I've had a closer look now and found that my canard trailing edge is straight and true but my elevators are a bit uneven on top (above the torque tube). I bought the elevators ready made, along with a lot of ther prefab stuff, from Jeff Russell at Aerocad. These are the first (only) parts I've seen Jeff produce that are not exactly perfect. Everthing else he has delivered me looks and fits fine. The fix will be quite simple (now that I can see what is wrong!) so I'm not suggesting I am unhappy at having puchased the elevators. I am very happy with all the stuff that Jeff has produced and have and will highly recommend his workmanship and parts. Allan From: Marc J. Zeitlin Subject: elevator torque tube tips Date: Mon, 10 Jul 95 17:07:38 EDT People; I started building the elevator torque tubes yesterday, and here's a few tips: I had to file the corners of the NC-2 torque tube inserts to fit inside the cut-outs in the tubes. You might imagine that with the same vendor (Ken Brock making the inserts AND the tubes) you wouldn't have to modify anything to make them fit, but no. The corners of the NC-2's were square and did not fit in the milled round corners of the torque tube cut outs. I have not been incredibly impressed with the quality of the Ken Brock parts that I've seen - I kind of feel like I should be taking a micrometer to them all. Without making everything from raw stock myself (or contracting with a local machine shop) is there anywhere else to go for the KB recommended parts? Next, I cut 3" off the ends of the tubes (to match the shortened canard length - Brock still makes them the original length [for you who don't trust Nat's recommendations :-)]) and then pop-riveted the NC-2's to the torque tubes. The plans don't mention that there's a left and a right version and you better pay attention to the orientation of the NC-2's, or else the hinge rod won't fit. One of the NC-2's was not perfectly aligned (after pop-riveting) so I have to use a long drill and reamer to re-align the hinge pin hole a few thousandths. I'd recommend having the hinge pin installed when doing the pop-riveting to ensure alignment. Nat recommends putting vaseline or grease in the hinge pin holes to block epoxy getting in - I'd wait until seconds before installing the tubes into the foam so that all the filing and sanding chips and dust doesn't get stuck in the grease. Seems obvious, when you look at the grease grabbing all the filings and dust, and wondering what that'll do to the hinge pin when you insert it :-). Thought this might save a few of you a bit of time and effort. P.S. - When I'm done with the elevator hot-wire templates, I'll mail them to Marty K., and they can follow the canard templates around to Lee D., etc. -- Marc J. Zeitlin E-Mail: marcz@an.hp.com Date: Mon, 10 Jul 1995 19:36:37 -0400 From: JIMWHI@aol.com Subject: Re: elevator torque tube tips In a message dated 95-07-10 17:14:10 EDT, you write: >Nat recommends putting vaseline or grease in the hinge pin holes to >block epoxy getting in - I'd wait until seconds before installing the >tubes into the foam so that all the filing and sanding chips and dust >doesn't get stuck in the grease. Seems obvious, when you look at the >grease grabbing all the filings and dust, and wondering what that'll do >to the hinge pin when you insert it :-). Instead of vaseline, I stuck a piece of 1/4" Clark foam in the hinge pin slots to keep the epoxy out. The thought of using vaseline and inadvertently getting some of it underneath a structural layup somewhere is a scary thought indeed. The Clark foam is easily removed after the glass cures. Date: Tue, 11 Jul 1995 08:21:36 -0400 From: CCady@aol.com Subject: Re: elevator torque tube tips In a message dated 95-07-10 17:14:10 EDT, you write: >I had to file the corners of the NC-2 torque tube inserts to fit inside >the cut-outs in the tubes. You might imagine that with the same vendor >(Ken Brock making the inserts AND the tubes) you wouldn't have to modify >anything to make them fit, but no. The corners of the NC-2's were >square and did not fit in the milled round corners of the torque tube >cut outs. > > I filed the corners of the torque tube to get the inserts to go in and I was also surprised that I had to do modifications. You could almost make your own tubes and do ok. I didn't think to round the corners of the inserts but thats probably better. Cliff From: Marc J. Zeitlin Subject: More tips on elevator construction Date: Sun, 16 Jul 95 15:22:57 EDT People; I micro'ed the elevator cores to the torque tubes, and had to do things differently from the plans, so I thought I'd let you know what I did. The plans seem to indicate that you could slip the foam over the torque tubes, but I found that if I tried that, the foam would break. I had to slide the foam onto the tubes lengthwise. Of course, I could no longer keep the torque tube jigs in place, since they'd rip the foam to shreds as well, so I applied the micro to the foam (and a little to the tube), and then slid the foam all the way onto the tube. I cut away the foam near the hinge openings, put the hinge pin and the jig(s) in place, and then rotated the foam so that it was flat while the torque tube was rotated all the way onto the jigs. I may be dim, but it took me a few minutes of staring at the picture in the plans to figure out the orientation of the foam and the torque tubes with respect to the jigs. Finally, the dotted line (a little hard to see) gave it away. Make sure the tube is resting on the jigs while the foam is flat. Hope this helps - if you don't understand what the heck I'm talking about, ask away. Marc-0083 -- Marc J. Zeitlin E-Mail: marcz@an.hp.com Date: Wed, 18 Oct 1995 00:43:55 -0400 From: KSPREUER@aol.com Subject: Re: Jack's tips #4 - Canard Lift Loss In a message dated 95-10-11 00:23:35 EDT,Stet writes: << Subj: Re: Jack's tips #4 - Canard Lift Loss <> Keith's comments: Yes that is the phenomenon we had exactly. I was aware of it and had heard that others had experienced it also. I was not aware that they reccomended setting the stop so that Cl max was not exceeded. I had thought that changing the stop would be a good idea but never got to it. This phenomenon is part of the reason that I used the pumping technique for take off, thus ensuring that the elevator would pass thru the best position. I don't believe that the problem on my airplane was due to exceeding the 22.5 degree limit. We checked that several times. I suspect it had to do with a noticable concave shape on the upper surface of the elevator or perhaps with the size of the slot between the elevator and the canard. No data on that though. From: Marc J. Zeitlin Subject: Canard Issue (maybe problem?) Date: Wed, 25 Oct 95 17:09:15 EDT People; I've got an issue with my Canard which may or may not be a problem, and I'd appreciate any input from people who may be able to help. I've got a web page at: http://www.ultranet.com/~marcz/cozy_mkIV/canard_problem.html which describes the issue, and has a picture which will be better than any explanation I can give here (although I'll try). The problem is, I seem to have somehow cut the canard with the trailing edge (and the elevators) about 1/8" low, although I used the elevator mounting templates when attaching the elevator hinges. The angles are all correct, but the trailing edge of the top of the canard is about 1/8" lower than it should be, and since the gap between the canard and the elevator is the specified distance, the elevator ended up 1/8" low as well. Here's a diagram of what I've got in relation to what it's supposed to look like: (Picture and text at address listed above). As I said, the offset is about 1/8". The canard is smooth, the airfoil shape on the canard and the elevators match up with the templates (except for the last 1" of the canard where the top slopes down too far). So, my questions are: Do I need to completely remake my canard or the trailing edge? Do I need to remove the elevator hinges and raise the elevator 1/8"? Or can I just leave everything the way it is? Obviously, I'm concerned from an aerodynamic and safety standpoint, and want to make sure that I will be able to fly safely. If it's only a question of one or two knots in speed, I won't be concerned. If I need to perform some major rework, of course I'll do it, but if it's safe the way it is, I'll leave it. Thanks in advance for any input. I've written to Nat about this, and received a pretty reasonable reply, but I'd like more input. I'd be happy to post what Nat told me after I receive your opinions - I don't want to bias people beforehand. -- Marc J. Zeitlin Email: marcz@an.hp.com From: DMDS%mimi@magic.itg.ti.com Date: Wed, 25 Oct 95 17:22:00 CDT Subject: Canard Issue (maybe problem?) From: "Marc J. Zeitlin" marcz@hpwarhw.an.hp.com Subject: Canard Issue (maybe problem?) The problem is, I seem to have somehow cut the canard with the trailing edge (and the elevators) about 1/8" low, although I used the elevator mounting templates when attaching the elevator hinges. The angles are all correct, but the trailing edge of the top of the canard is about 1/8" lower than it should be, and since the gap between the canard and the elevator is the specified distance, the elevator ended up 1/8" low as well...................... I don't have any qualified answers to give you, but I am curious how this could have happened and not have been noticed early on prior to glassing the canard foam core. I only ask so that we all may gain some insight here so please don't take it in a disparaging way. David From: Marc J. Zeitlin Subject: Canard Issue (maybe problem?) (fwd) Date: Thu, 26 Oct 95 8:54:23 EDT David DeSosa writes: >MJZ wrote: >>The problem is, I seem to have somehow cut the canard with the trailing >>edge (and the elevators) about 1/8" low................ > > >I don't have any qualified answers to give you, but I am curious how this >could have happened and not have been noticed early on prior to glassing the >canard foam core. Not clear. I think that as I used the templates to check the foam, everything looked fine. You glass the bottom of the canard first, and then cut off the "tail" of foam on the top, and then glass the top. I have a feeling that what happened was that the hot-wiring was fine, but then in the peel-plying, glassing, "tail" removal, and top glassing of the canard trailing edge, I slowly kept working it lower and lower, and didn't check with the templates until after finishing. It didn't occur to me that the slight discrepancy I saw (just in the trailing edge of the canard, before building the elevators) would be an issue. I swear that when I floxed the hinges into the canard, with the elevator in the original jig, the bottom of the canard and the bottom of the elevator were in line - at least I THOUGHT they were. The only thing I can say to others is to be REAL careful in the trailing edge work on the canard, and in floxing in the hinges - measure everything five times. (I hope that it wasn't my hot-wiring templates - I don't have them to check against the alignment jigs - Marty Kansky has them, and has probably used them by now. Marty - did I screw you up?). >........... I only ask so that we all may gain some insight here so >please don't take it in a disparaging way. No offense taken - I can call myself a moron as well as anyone :-). If this is the last big mistake I make while building this thing, I'll be thrilled. -- Marc J. Zeitlin Email: marcz@an.hp.com Reply-To: Nigel.Field@HQPSB.SSC.ssc-asc.x400.gc.ca Date: Thu, 26 Oct 1995 15:13:23 GMT From: Nigel.Field@HQPSB.SSC.ssc-asc.x400.gc.ca (Field, Nigel (1416)) Subject: RE: Canard Issue (maybe problem?) Marc Z asks: I've got an issue with my Canard which may or may not be a problem, and I'd appreciate any input from people who may be able to help. Marc , I think this is the problem you are describing. I encountered this problem 4 years ago when I built a short (110) inch Roncz canard for my VE using the RAF plans for the LE retrofit. When I cut off the fish tail and started to blend the top down to the slot I thought all the same things ... ie I had messed up somewhere but on close examination I found the problem was in the plan. This can easily be verified by taking a french curve and projecting the top airfoil curve with a pencil right to the trailing edge below the fish tail. If you dont have a french curve try a winglet template where it is curvy. Guess what its out by 3/16 inch. I corrected this by building the top back up with strips of uni and then raised the slot up to meet. It was a lot of extra work and weight. The canard flies perfectly but then I made other mods also which I can address separately if anyone is interested. I suspect the MK IV plans are a carbon copy of the RAF LE Roncz plans and include this error. I told my friend a year ago when he was building his MK IV canard and he called the Publisher of the Plans (POP). He was told that he had sold X hundred plans and this was the first he had heard of it and that there was no problem so he built it per plans and guess what folks, his was out 3/16 inch. On my Cosy Roncz canard I modified the airfoil templates by raising the slot to meet the top airfoil curve and it blended perfectly when I cut off the fish tail. The elevators still fit OK but I'm using a different hinge arrangement. (5.65c+/IDA-1.4.4 for ); Thu, 26 Oct 1995 08:45:20 -0700 Date: Thu, 26 Oct 95 08:45:20 -0700 From: Brian DeFord Subject: canard problem Marc, I have a NASA program which analyzes and can be used to design airfoils. I wonder if we could input the airfoil coordinates of the Roncz canard and compare the results to your "as built" canard. What I would need is the actual airfoil coordinates if anyone has them. I could probably then determine what your canards coord's are based on your drawing. Let me know what you think. Regards, Brian Date: Thu, 26 Oct 95 10:48:11 EST From: "Wilhelmson, Jack" Encoding: 12 Text Subject: Re: Canard Issue (maybe problem?) Marc: MY OPINION ON YOUR CANARD. Yes, you do have a problem. The canard airfoil is very critical, and there are enough unknowns already in the elevator canard shape areas. It is my opinion that most of the differences in Cozy characteristics come from these unknowns. Anyway, first I have a question. How can you raise the elevator hinges .125"? Your drawing leads me to believe this is not possible. If it is possible, how much slot would be left? The slot is important to elevator performance. Date: Thu, 26 Oct 1995 14:03:00 -0400 From: Dick.Finn@FNB.sprint.com Subject: Re: Canard Issue (maybe problem?) Marc, It seems to me that a short while back Nat Puffer passed along a builder hint relating to difficulties in positioning the elevator hinges. I guess that a lot of people have had problems with elevator trave (myself included). I had already passed that point and solved the problem through a great deal of sanding. I plan to rebuild the elevators though as I am not comfortable with the quality. When I do I will pull the hinges and try it according to the suggestion. It seems that it might relate to the 1/8" discrepancy you noted though. The following is as I remember the suggestion. Oone of the builders mounted the elevators and canard in a jig with the elevators at full up travel (nose down). With everything held solidly in this position he installed the hinges in the canard. When removed from the jig he was able to obtain full up and down travel. I'm willing to bet that this relates to the 1/8" discrepancy (maybe not though). You might try a search through your on line copies of the newsletter to see what you can find. Let me know what you think--it may prove helpful when I rebuild the elevators. Dick Finn ______________________________ Reply Separator _________________________________ Subject: Canard Issue (maybe problem?) Author: marcz@hpwarhw.an.hp.com at INTERNET Date: 10/25/95 5:15 PM From: Marc J. Zeitlin Subject: Re: Canard Issue (maybe problem?) (fwd) Date: Thu, 26 Oct 95 17:41:31 EDT People; With regard to my canard "problem": Dick Finn wrote: > It seems to me that a short while back Nat Puffer passed along a > builder hint relating to difficulties in positioning the elevator > hinges.................. > ........... It > seems that it might relate to the 1/8" discrepancy you noted though. > The following is as I remember the suggestion. Oone of the builders > mounted the elevators and canard in a jig with the elevators at full > up travel (nose down). With everything held solidly in this position > he installed the hinges in the canard. When removed from the jig he > was able to obtain full up and down travel. I'm willing to bet that > this relates to the 1/8" discrepancy (maybe not though). I remember this from the newsletters. I did not use that method, and I have full up and down travel on my elevators - that doesn't seem to be the issue. This is really a shape problem, not a hingeline location problem. Jack Wilhelmson wrote: > Yes, you do have a problem. The canard airfoil is very > critical, and there are enough unknowns already in the > elevator canard shape areas. It is my opinion that most of > the differences in Cozy characteristics come from these > unknowns. Yeah, that's sort of what my feeling was, at first. Maybe still is; I'm not sure. > ...... Anyway, first I have a question. How can you raise > the elevator hinges .125"? Your drawing leads me to believe > this is not possible. If it is possible, how much slot would > be left? The slot is important to elevator performance. Well, I've had a couple of ideas. 1) I could move the hinges up AND back 1/8" in each direction, keeping the slot about the same size, and making the canard 1/8" longer. I would think (assuming that the airfoil shape was still OK, that the extra length would not be a major issue. 2) I could saw through the skins of the canard behind the spars, feather edge everything, and then tape the canard back together in the right place with a few layers of BID and then sand and micro everything flush. I'm not real happy with this idea. 3) I could build up the top of the canard where it's too low with glass, sand away the bottom part of the trailing edge, lay up new glass there, and then re-install the hinges 1/8" further up. Here's Nat's idea (he didn't seem REAL concerned, and didn't really want to commit): Fill the bottom of the canard with 1/8" micro where it leads into the elevator, and feather that forward a few inches to blend with the rest of the bottom of the canard. This would have the effect of rotating the canard a degree or so nose up, which I could correct for in mounting to the fuselage. He said that in developing the canard, John R. tested 6 different shapes, all similar, and they all did about the same thing aerodynamically. My interpretation would be that smoothness and un-waviness are more important than the exact shape, especially toward the rear where the airflow is turbulent anyway. If the slot is the right size, then the flow should still re-attach onto the elevator, keeping the elevator effectiveness. Who knows.... Brian DeFord wrote: > I have a NASA program which analyzes and can be used to design >airfoils. I don't have the coordinates - I'm trying to get in touch with John Roncz via email (to ask him about this) and maybe we could get the airfoils that way. We'll see - thanks for the offer. Nigel Field wrote: >I encountered this problem 4 years ago when I built a short (110) inch Roncz >canard for my VE using the RAF plans for the LE retrofit. ....... >............. Guess what its out by 3/16 inch. I >corrected this by building the top back up with strips of uni and then >raised the slot up to meet. It was a lot of extra work and weight. This is probably my preferred fix, if a fix is necessary at all. As I said, I'm interested in safety, not in the last 1 or 2 knots. Thanks for all the replies guys; I don't have the answer yet, but it's good to get opinions and ideas, and see that others have run into this issue. Keep those cards and letters coming in.......... -- Marc J. Zeitlin Email: marcz@an.hp.com Fri, 27 Oct 1995 10:28:01 +1000 Date: Fri, 27 Oct 1995 10:19:31 +0200 From: parkyn@citr.uq.oz.au (Nick Parkyn) Subject: Canard Issue (maybe problem?) Brian DeFord wrote: >> I have a NASA program which analyzes and can be used to design >>airfoils. Airfoil design using computer programs is not trivial - I know because I have done a lot of research on airfoils for hydrofoils and airfoils for multihulled yachts, designing custom airfoils using the best software available in the industry. Be careful there are only a very few programs that can accurately predict lift and drag. Accurate determination of lift would be very important in this application. I would not suggest this direction! Nick #0012 Fri, 27 Oct 1995 10:51:44 +1000 Date: Fri, 27 Oct 1995 10:43:11 +0200 From: parkyn@citr.uq.oz.au (Nick Parkyn) Subject: Canard Issue (maybe problem?) Does the canard you built match the shape of the templates on the plans! The critical airfoil templates should not be supplied on paper as it is not dimensionally stable - they should be provided on Mylar film. Significant dimensional changes can occur with paper! Nick #0013 (Smail3.1.28.1 #7) id m0t8r8d-000UmdC; Fri, 27 Oct 95 08:56 PDT (Smail3.1.28.1 #2) id m0t8r8d-000qDLC; Fri, 27 Oct 95 08:56 PDT Date: Fri, 27 Oct 95 08:56:11 PST From: Brian DeFord Subject: Re: Canard Issue (maybe problem?) Brian DeFord wrote: >> I have a NASA program which analyzes and can be used to design >>airfoils. Nick replied: >>Airfoil design using computer programs is not trivial - I know because I >>have done a lot of research on airfoils for hydrofoils and airfoils for >>multihulled yachts, designing custom airfoils using the best software >>available in the industry. Be careful there are only a very few programs >>that can accurately predict lift and drag. Accurate determination of lift >>would be very important in this application. >>I would not suggest this direction! The offer to Marc was for comparison purposes only, not for proof that the airfoil would fly as simulated. Marc did not include all of my message to him which would have made that more clear. I am trying to offer additional data for Marc to make his decision. I agree with you in principal that computer simulation is not trivial, however, I feel that comparing the two airfoils would give an INDICATION of what could be expected should he try to fly his canard shape vs. the intended shape. Brian Date: Sat, 28 Oct 1995 13:56:28 EDT From: RMWT64A@prodigy.com (MR JOHN G RONCZ) Subject: canard Marc, I think it will be OK, but then it's impossible to say for sure. You have essentially added camber to the airfoil, which will increase its lift some. The part I can't be sure of is what the effect will be of having the lower surface of the elevator sticking below the main element when the elevator is at zero deflection. I do think it will have some effect on hinge moments (stick force) and may have some effect when flying in rain. But if it were mine, I'd fly it the way it is and then fix it if it has some bizarre behavior. BE CAREFUL! John Roncz Mon, 30 Oct 1995 11:08:33 +1000 Date: Mon, 30 Oct 1995 10:59:57 +0200 From: parkyn@citr.uq.oz.au (Nick Parkyn) Subject: Re: Canard Issue (maybe problem?) Sorry, I am not trying to be non-constructive, negative or not helpful. If you really want to do this, you would should model the canard airfoil and elevator as two separate elements. This would require multi-element airfoil analysis program. If you have a single element airfoil software - it will not be a very useful exercise. You need to accurately determine CL values for elevator / main airfoil configuration. The gap and shape would need to be the same as the actual implementation that Mark has. The problem here is that that most software cannot accurately determine the lift coefficient and it is suggested that this may be as much as 20% out on the optimistic side. You could compare the values obtained with the correct shape, but you would still need to know the accurate actual CL values to determine if it was a "safe" configuration. Any significant differences in the canard really means you have to conduct a new flight test program! The gap is also quite critical. I recall a report once where mylar gap seals were tried on the elevators of the canard (not a Rutan or Cozy design) and it caused a deep stall condition. If you wish to try it and you have got the right tools, thats great! - you must just be careful that what you determine from the results is in fact correct! This is often based on your own experience with the software that you are using! John Roncz is an EXPERT and had extensive experience with the software he used to design the RM1145 (Roncz Canard) and knew the values were correct - it was still flight tested by RAF. By comparison the GU canard was computer designed and wind tunnel tested to determine accurate CL values. Nick #0015 > >Brian DeFord wrote: > >>> I have a NASA program which analyzes and can be used to design >>>airfoils. > >Nick replied: > >>>Airfoil design using computer programs is not trivial - I know because I >>>have done a lot of research on airfoils for hydrofoils and airfoils for >>>multihulled yachts, designing custom airfoils using the best software >>>available in the industry. Be careful there are only a very few programs >>>that can accurately predict lift and drag. Accurate determination of lift >>>would be very important in this application. > >>>I would not suggest this direction! > > >The offer to Marc was for comparison purposes only, not for proof that the >airfoil would fly as simulated. Marc did not include all of my message to him >which would have made that more clear. I am trying to offer additional data >for >Marc to make his decision. I agree with you in principal that computer >simulation is not trivial, however, I feel that comparing the two airfoils >would >give an INDICATION of what could be expected should he try to fly his canard >shape vs. the intended shape. > >Brian > Mon, 30 Oct 1995 15:09:33 +1000 Date: Mon, 30 Oct 1995 15:00:59 +0200 From: parkyn@citr.uq.oz.au (Nick Parkyn) Subject: Re: Canard Issue (maybe problem?) Marc, I looked at your diagram in your web page. I do not think it would be wise to fly with that canard as it is. It seems that the lower edge of the elevator is below the lower edge of the main foil at zero elevator deflection. This will cause excessive drag and may alter the flow through the gap and I would think adversely affect elevator loads and performance at positive, negative and zero deflection. I would suggest that you cut the glass skin along the span on the upper surface a short distance from the trailing edge and along the midpoint of the trailing edge and remove the upper trailing edge corner. Bond some Styrofoam onto the canard and shape it in position, then glass over it and fair. Use a 100:1 or more taper on the glass joints the upper surface joint is the most critical. If you run the joint on the surface where it is still slightly low, this will allow some fill to cover the joint. If you did not have to change the position of the trailing edge upper lip you could have re-profiled it with lightweight filler - some composite gliders have used around 3mm of fill in places to reprofile wings. The beauty of composites is that they are relatively easy to fix! I hope these suggetsions are helpful! Nick................ From: Marc J. Zeitlin Subject: Canard Issue (maybe problem?) Date: Mon, 30 Oct 95 11:27:03 EST People; First, I'd like to thank everyone who took the time and effort to think about and respond to my questions regarding the canard / elevator displacement issue. I've received a bunch of good suggestions, as well as opinions regarding safety. I'll list them in my completely subjective determination of quality, and summarize and paraphrase: 1) From Nigel Field and Nick Parkyn: This is important - don't fly like this. Fix it by adding foam and/or glass to the top of the trailing edge of the canard to build it up to the correct shape. Sand away the bottom of the trailing edge of the canard, and then re-glass to join with the new glass from the top surface. Now, the canard is correct. Then rip out the hinges and re-install them 1/8" further up. Then, re-do the wingtips to match the new trailing edge and elevator. 2) From John Roncz (THE MAN): (Incidentally, I got a response from him within 24 hours - I was VERY happy!). John said (after looking at the web page picture) that if it was HIS plane, he'd fly it, see if it exhibited any bizarre behavior, and then fix it if it did. He felt that it might raise the effective angle of attack slightly (the way it is) and that the hinge moments might increase slightly, affecting the stick forces. He didn't think it would be significant, however. (Some other respondents had the same basic comments). 3) From Nat Puffer: Nat didn't want to commit to what the changes might be, but suggested building up the BOTTOM of the canard 1/8" with filler to blend into the bottom of the elevator. Some people suggested (and offered) to perform Computer analyses of the two different airfoils to try to predict what might happen. Given my experience with Finite Element Analysis and Fluid Dynamics codes, I don't think that the uncertainty involved here would tip the balance one way or the other as far as what I should do, and would involve as much work on the part of myself (and others) as just fixing the damn canard :-). So, what am I going to do? While I'd really like to ignore it, and follow John Roncz's suggestion, I've about run out of money for a while so I can't work on the landing gear (the next chapter in the ad-hoc schedule). This will give me a month or two over the winter to follow Nigel and Nick's recommendations (and many other people's suggestions) to fix it, and NOT fly as it is, and it'll cost less than $100 to do so. What's an extra month over 4-5 years, when my safety's at stake, eh? :-). Thanks again to everyone - I really appreciate it. I urge everyone to check their airfoils against the templates before and after hotwiring and sawing off the "fishtail" - had I done that, I'd have saved myself a lot of work. -- Marc J. Zeitlin Email: marcz@an.hp.com From: Marc J. Zeitlin Subject: Canard problem - one last time Date: Tue, 7 Nov 95 10:06:13 EST People; This will be the last question on this topic, I promise! :-). I received a response from Vance Atkinson (Nat and Vance are interesting guys - they both write their responses on the back of the letters I send them - maybe writing paper is expensive out west?) regarding my canard shape problem. Surprisingly (or maybe not so) he suggested almost exactly the same fix as Nat did - fill the bottom of the canard with micro to build it up to the level of the elevator, then cover the micro with one layer of REALLY light boat fiberglass to keep the micro from cracking. He said that he had fixed a similar shape problem on a V.E. a while back (the bottom spar cap stuck down below the bottom of the canard about 1/8", so they re-profiled the bottom of the canard after checking with Mike Melville) and that the plane flew fine with no noticable differences. So, since this fix is substantially less work than the re-doing of the canard trailing edge, moving the hinges, and then re-doing the wing tips, I need somebody to shoot holes in it so that I won't do this instead :-). For those of you who have no idea what I'm talking about, check out: http://www.ultranet.com/~marcz/cozy_mkIV/chapters/chap11_2.html for a picture and a description of the problem. Thanks again - sorry to bring this up once more - this'll be the last! -- Marc J. Zeitlin Email: marcz@an.hp.com Date: 7 Nov 1995 16:14:17 U From: "Judd Stewart" Subject: Re: Canard problem - one las RE>Canard problem - one last time 11/7/95 Marc, My philosophy is " The best that I can do is Just/Barely ACCEPTABLE" Do what makes you feel comfortable. When your rolling down the runway on the first flight there will be a zillion things going through your mind, I personally don't want to worry about the "aerodynamics " I think structure and propulsion are enough. I'd opt for the redo instead of the patch! I know it will take me a hundred years and countless thousands of extra dollars to get in the air, but the bottom line is it's my butt up there not somebody sitting at the other end of wire! My two bits "Mr. Conservative"