From: "Kim Schallhorn" Subject: COZY: Elevator Hinge Attach Points Date: Sat, 24 Jan 1998 15:05:59 -0600 I made a mistake in shortening my canard and the associated hinge attach points. When I shortened it, I mistakenly adjusted the hinge attach points by 3 inches on each side. I made the elevators per plans, without any length adjustments, thinking that I would cut the inboard side later. Now I'm ready for some indoor winter work, such as attaching and finishing the canard. I flip the plans back to the elevator attach chapter and discover that my outboard and middle hinges will be 3 inches off. The outboard hinge will be 6 inches in from the end of the canard, instead of the 3 inches called for in the plans. I don't think that the middle hinge will matter. It will also be 3 inches inboard from the plans point. It would be a mess trying to move everything out by 3 inches...... What do you think?????? Thanks, Daryl Lueck Cozy IV N797DL From: Marc J. Zeitlin Subject: COZY: Elevator Hinge Attach Points (fwd) Date: Mon, 26 Jan 98 10:05:22 EST Daryl Lueck writes: >I made a mistake in shortening my canard and the associated hinge attach >points. When I shortened it, I mistakenly adjusted the hinge attach points >by 3 inches on each side. >... The >outboard hinge will be 6 inches in from the end of the canard, instead of >the 3 inches called for in the plans. I don't think that the middle hinge >will matter. It will also be 3 inches inboard from the plans point. >What do you think?????? Given that the original canard had the hinge point 6" from the tip, I wouldn't think your modified hinge positioning would be a problem with the shorter canard. Just my personal opinion - I'd check with Nat on this, but I'd be surprised if he objected to your change. -- Marc J. Zeitlin Email: marcz@an.hp.com From: lschuler@cellular.uscc.com Date: Mon, 26 Jan 98 11:24:11 -0600 Subject: COZY: Elevator Hinge Attach Points (fwd) Daryl Lueck wrote: >snip >What do you think?????? >snip Think you might still be OK with the hinge locations as long as distance between the two outer points remained the same. The outboard hinge point on the full-length canard is 6" inboard of the end anyway; same as what you ended up with. (it should be 6.1" when setting the hinge-foam in the canard to allow for the 0.1" gap between the elevator and tip; but that's another issue). I think your only concern will be the length of the torque tubes at the inboard end. You'll probably end up cutting 3" off the there to get everything to line up again. Larry Schuler MK-IV plans #500 lschuler@cellular.uscc.com From: cdenk@ix.netcom.com Date: Fri, 27 Feb 1998 16:08:43 -0600 (CST) Subject: Re: COZY: Frustrated, If the trailing edge of the elevator is going to be a little heavy due to the repair, its necesary to increase the counterweight mass. The counterweight is the steel rod at the leading bottom edge of the aileron. Most have used 3/8" dia. and have heard of 7/16" dia. being used. It should be possible to hot wire a wing trailing edge, just enough to make an aileron from. shouldn't be too difficult and probably be less time than trying a repair. Most ailrons are difficult to balance under best of conditions, As I am writing, My thoughts go toward a new piece rather than repair. From: Marc J. Zeitlin Subject: Re: COZY: Frustrated Date: Fri, 27 Feb 98 17:40:31 EST Carl Denk wrote; >If the trailing edge of the elevator is going to be a little heavy due >to the repair, its necesary to increase the counterweight mass. The >counterweight is the steel rod at the leading bottom edge of the >aileron. Tom was talking about his canard and elevator. While I agree with you that it is most important to ensure that the balance is correct, I think it would be a lot easier to increase the weight of the lead on either the inboard (most easy) or outboard (less easy) counterweights for the elevators than it would be to increase the rod weight for the aileron, which as you point out is difficult. In Tom's case, here, I'd still go with the attempted fix and then balance the elevators carefully. In the case of ailerons with this condition, I might very well agree that redoing them could be the appropriate choice. -- Marc J. Zeitlin Email: marcz@an.hp.com From: lschuler@cellular.uscc.com Date: Mon, 16 Mar 98 09:15:17 -0600 Subject: COZY: Canard tips Finished glassing my canard tips this weekend and thought I'd pass along a couple observations/suggestions. The plans call for 2-3/4" thick foam for the tips. A line is drawn on the rear of the foam block after microing to the canard. The line is referenced to the top of the canard trailing edge. Problem is created when following the recommended change to the canard trailing edge. The foam comes out just a hair shy of being 1" above the canard TE. Since the foam gets sanded to shape, a little extra thickness will make it easier to place the block on the canard and achieve the 1" height above the canard TE. When cutting the block of foam, I'd recommend 3" thick rather than 2-3/4". Also, when sanding the blocks, I found that it may be best to have the block extend below the bottom of the canard (at about the spar cap) by about 1/8". It would be easy to sand away just a hair too much foam when shaping the underside and messing up an othrwise nice curved contour. This little extra foam would make it easier (safer) to shape and would be sanded flush with the canard in the process. Need to start with a thicker block though (see above). Larry Schuler plans #500 (futzing with canard/elevators since October) lschuler@cellular.uscc.com From: "Nat Puffer" Subject: Re: COZY: Canard tips Date: Mon, 16 Mar 1998 09:47:30 -0600 Dear Tom, What I find works well is to put a slight bend in the hinge pin, and then rotate it while seeking the hole. The bend should just be enough to overcome the sag caused by gravity. Best Regards, Nat ---------- > From: Tom Brusehaver > To: lschuler@cellular.uscc.com > Cc: cozy_builders@hpwarhw.an.hp.com > Subject: Re: COZY: Canard tips > Date: Monday, March 16, 1998 11:18 AM > > > > Finished glassing my canard tips this weekend and thought I'd pass > > along a couple observations/suggestions. > > > > The plans call for 2-3/4" thick foam for the tips. A line is drawn on > > the rear of the foam block after microing to the canard. The line is > > referenced to the top of the canard trailing edge. > > I did exactly the same thing this weekend and ran into exactly the > same trouble. 2-3/4" is not thick enough to make this easy, cut 'em > 3" thick and life will be much easier. > > The ends cannot go on "level", but the T.E. must be angled up slightly > to get the 1" above the reference point. I probably cut everything > and prepped the install for an hour. Then fiddled around for another > hour trying to get the whole tip covered so that sanding would work. > > Once the micro was dry, I started carving. I started sanding like the > plans say, but found rough cutting with a hacksaw blade much quicker. > I stayed at least a half inch up from the line, and then sanded the > last half inch. > > I have the bottom sanded but I am wondering, when to put in the tube > for the hinge pin. I am thinking it would be easist to 5min the tube > now, and finish sanding it and the foam at the same time. That way it > is in the "right" place. I don't think I should have the hinge pin in > while glassing the bottom. > > What is the trick to getting the hinge pin in? I can get it in easy > when I have the canard pointing nose down, but when the canard is > level, the pin sags and it won't hit the holes. This shouldn't be a > problem when working on the canard off the airplane, but should it be > necessary to remove the hinge pin, while the canard is on the > airplane, it will be impossible to put back in. Date: Mon, 16 Mar 1998 18:25:40 -0600 From: Mike Davis Subject: Re: COZY: Canard tips > > What is the trick to getting the hinge pin in? I can get it in easy > > when I have the canard pointing nose down, but when the canard is > > level, the pin sags and it won't hit the holes. If I may add a small building tip; read on. I added a slight chamfer to the NC-2 inserts to help guide the hinge pin into the hole. The chamfer is only needed on the outboard side and seems to help. I also "bored" the 3/16 hole with an end mill from the inboard side, holding short of breaking through. This eliminates the possibility of hitting the wrong hole when sliding the hinge pin through. I hope this helps someone because sliding the pin in can be a pain! Mike From: cdenk@ix.netcom.com Date: Mon, 16 Mar 1998 18:43:20 -0600 (CST) Subject: Re: COZY: Canard tips Mike Davis writes The problem is gravity prevails and the pin deflects enough to miss the hole. Rotate the canard about its long dimension, usually when the hole in the inserts is nearest down the pin will slip in. I wouldn't change the insert hole. That will reduce the bearing area increasing wear. From: cdenk@ix.netcom.com Date: Mon, 16 Mar 1998 18:52:51 -0600 (CST) Subject: Re: COZY: Canard tips Tom Brushaver writes Don't know why you would AND COULD do that. You are not going to get the elevator out without taking the center tube and offsets off. A combination of hinges and tubes nestled together are not going to let it happen! To remove the pin and not support the elevator will put dangerous stress on the tube and offsets. Its not that hard to remove the canard. The longest time is spent removing old white RTV sealant. From: Cozy7971 Date: Mon, 16 Mar 1998 22:14:27 EST Subject: Re: COZY: Canard tips In a message dated 98-03-16 12:57:26 EST, cozy@extremezone.com writes: << What I find works well is to put a slight bend in the hinge pin, and then rotate it while seeking the hole. The bend should just be enough to overcome the sag caused by gravity. Best Regards, Nat >> I used the method that Nat suggests but elaborated a bit. I have a small battery operated variable speed drill. I chucked the hinge pin and let the drill do the rotating. Dick Finn Date: Mon, 16 Mar 1998 21:47:29 -0500 From: Ian Douglas Subject: COZY: Elevators Hi, I was just taking a look at the elevators I got with this semi finished project. It would appear that someone (owned by two others prior to me) was a little over zealous when sanding the elevators and managed to go through the glass to the micro in a couple of spots. What is the recommended repair for this (I know that the weight and balance of the elevators is critical). Is 0.25" of glass to glass bond enough on the canard TE and the elevators TE? I had them exray and ultra sound tested and that appears to be the smallest glass to glass join. -- Best regards, Ian D.S. Douglas MK0069 MK0626 From: "Fred I. Mahan" Subject: Re: COZY: Elevators Date: Tue, 17 Mar 1998 09:09:15 -0500 > I was just taking a look at the elevators I got with this semi finished > project. It would appear that someone (owned by two others prior to me) > was a little over zealous when sanding the elevators and managed to go > through the glass to the micro in a couple of spots. What is the > recommended repair for this (I know that the weight and balance of the > elevators is critical). The proper fix is to cut the elevators off of the elevator tubes, throw them away, and hot wire new cores. You can't lap on more glass or do a repair -- you'll make the elevators heavier. Fred in Florida Long-EZ N86LE Defiant project From: "Steve Campbell" Subject: Re: COZY: Canard tips Date: Tue, 17 Mar 1998 09:10:45 Nat is absolutely right here. One comment that I will add however is that I did not follow the plans directions the first time out. I did not sharpen the point of the hinge pin, since it already seemed pretty pointy. As a result I had a devil of a time trying to get it to work. Sharpened the pin tip and now it works, but still requires some twisting and probing. One minor "tip": I marked the hingle pin with a permanent marker to indicate the locations of the holes. This seems to help me find them by feel. Regards Steve On Mon, 16 Mar 1998 22:14:27 EST, Cozy7971@aol.com wrote... >In a message dated 98-03-16 12:57:26 EST, cozy@extremezone.com writes: > ><< What I find works well is to put a slight bend in the hinge pin, and >then > rotate it while seeking the hole. The bend should just be enough to > overcome the sag caused by gravity. Best Regards, Nat > ************************************************ Stephen A. Campbell, Professor, ECE University of Minnesota 200 Union Street Minneapolis 55455 (612) 625-5876 phone / (612) 625-4583 fax Campbell@ece.umn.edu ************************************************* Date: Tue, 17 Mar 1998 08:12:58 -0800 From: Eric Westland Subject: Re: COZY: Canard tips I can get the pins in every time, but does anyone have any neat tricks on getting the washers in position so they will stay? Also, when I shortened my canard, I could no longer use the inserts with the set screws that retain the pin because my elevator weights were in the way. Anyone else run into this and if so, what hinge pin retention system did you come up with? -eric Steve Campbell wrote: > Nat is absolutely right here. One comment that I will add however is that > I did not follow the plans directions the first time out. I did not > sharpen the point of the hinge pin, since it already seemed pretty pointy. > As a result I had a devil of a time trying to get it to work. Sharpened > the pin tip and now it works, but still requires some twisting and probing. > One minor "tip": I marked the hingle pin with a permanent marker to > indicate the locations of the holes. This seems to help me find them by > feel. From: lschuler@cellular.uscc.com Date: Mon, 16 Mar 98 16:52:18 -0600 Subject: Re[2]: COZY: Canard tips tgb@netco.com wrote (use your name next time): >I did exactly the same thing this weekend and ran into exactly the >same trouble. 2-3/4" is not thick enough to make this easy, cut 'em >3" thick and life will be much easier. >The ends cannot go on "level", but the T.E. must be angled up >slightly to get the 1" above the reference point. I probably cut >everything and prepped the install for an hour. Then fiddled around >for another hour trying to get the whole tip covered so that sanding >would work. One of my problems was also keeping the bottom aligned with bothe the canard and the elevator. The additional thickness would help tremendously. >Once the micro was dry, I started carving. I started sanding like >the plans say, but found rough cutting with a hacksaw blade much >quicker. I stayed at least a half inch up from the line, and then >sanded the last half inch. Hadn't thought of a hack saw; maybe just too scared of taking too much off. I used a wood rasp. Works real fast on styro. >I have the bottom sanded but I am wondering, when to put in the tube >for the hinge pin. I am thinking it would be easist to 5min the tube >now, and finish sanding it and the foam at the same time. That way >it is in the "right" place. I don't think I should have the hinge >pin in while glassing the bottom. I ended up with very thin foam on the tip right at the foam. Considered wraping it with box tape and filling the foam with flox. That may have worked well, but also figured getting the pin back out after cure would damage the foam too much; so I didn't. I removed the center spool piece from the elevator assembly so I could insert/remove the pins from the center. Used some 3/16" ID brass tubing I had (hobby shop stuff). Don't know if that was the right thing to do, but the thin wall is better than any plastic tubing I could find and certainly strong enough. I will be drilling/reaming these back out next weekend before glassing the remaining exposed foam in the elevator area. You are correct about not leaving the pins in while glassing the bottom. Don't; unless you will never want to be able to remove them. >What is the trick to getting the hinge pin in? I can get it in easy >when I have the canard pointing nose down, but when the canard is >level, the pin sags and it won't hit the holes. This shouldn't be a >problem when working on the canard off the airplane, but should it >be necessary to remove the hinge pin, while the canard is on the >airplane, it will be impossible to put back in. The plans suggest bending (actually just bowing in a slight curve between the two inside hinge points) the pins just a bit. Then when inserting them, just rotate slightly while banging into the inserts; you'll eventually find the right hole in the inserts. Just be carefull not to bend them too much and cause excess wear in the hinges or inserts. The bow is not needed when the canard and elevators are upright (ie normal), so maybe they can be straightened out a bit later to keep the wear down.... Larry Schuler Plans #500 lschuler@cellular.uscc.com From: lschuler@cellular.uscc.com Date: Tue, 17 Mar 98 16:25:19 -0600 Subject: Re[2]: COZY: Canard tips Dick Finn wrote: <<< What I find works well is to put a slight bend in the hinge pin, and then rotate it while seeking the hole. The bend should just be enough to overcome the sag caused by gravity. Best Regards, Nat >>> >I used the method that Nat suggests but elaborated a bit. I have a small >battery operated variable speed drill. I chucked the hinge pin and let the >drill do the rotating. Just a thought: Nifty trick, but I'd be a bit careful about doing this if the inserts are not lubricated a tiny bit. When twisting and pushing my pins in (dry), I noticed some resistance in spots. Probably due to non-perfect roundness of the pins I suppose. Go too fast and the pin becomes a drill of sorts and may cause some unnecessary damage to the inserts. Yeah, I'm a perfectionist. Probably why I've been working on the canard/elevators since October (besides work)..... :-) Larry Schuler Plans #500 lschuler@cellular.uscc.com Date: Tue, 17 Mar 1998 21:46:02 -0600 From: Mike Davis Subject: Re: COZY: Canard tips cdenk@ix.netcom.com wrote: > > On 03/17/98 19:06:57 you wrote: > > > >cdenk@ix.netcom.com wrote: > >> > >> Mike Davis writes > >> The problem is gravity prevails and the pin deflects enough to miss the hole. Rotate the canard > >> about its long dimension, usually when the hole in the inserts is nearest down the pin will slip in. > >> I wouldn't change the insert hole. That will reduce the bearing area increasing wear. > >The small chamfer doesn't reduce the bearing area enough to be concerned > >about. The pin doesn't rotate in the NC-2's anyway. Believe me, the > > > > Its not only wear, but the pin bearing (resting) on the aluminum. The extreme would be a knife edge, > which would crush. There is quite a bit load on the pin, and I wouldn't want mine to deform from not > enough bearing area. If my memory is right, normally there is 2 x .25" length x 3/16" dia. = .075 > sq.in. At roughly a factor of safety of 6 and 22,000 yield strength of aluminum = 250 allowable > load, I said roughly. WIth vibration, the pin does have some clearance in its hole, it certainly > could elongate the hole if there isn't enough area for the load. Now calculate the bearing load on the bronze bushing in the NC-3 hinges..... I took statics, strength of materials and structures too. I rest my case. Date: Wed, 25 Mar 1998 21:07:18 -0500 From: Ian DS Douglas Subject: COZY: Elevator Weight Hi there, I was just looking over in the plans and I am unable to find the max weight for the elevators. It says that the weight is important and that they should point down once painted other than that?!? Mine currently weigh 3lbs - 7.5 oz but I have to do some repairs (posted earlier). With my dremel and 45 deg. wire brush tool I am able to remove a single layer of glass with very good precision. What I want to know is what is the max allowed weight is and if I am already close (still determining fix vs rebuild). The shape is right on with templates, the balance is good, and all of that brock hardware doesn't have to be stripped and cleaned of old foam and glass if the max weight is achievable. -- Best regards, Ian D.S. Douglas MK0069 Date: Wed, 25 Mar 1998 21:20:42 -0500 From: David Domeier Subject: Re: COZY: Elevator Weight Ian, The numbers you are looking for are on page 34 of the Owners' Manual. Max elevator weight is 3.9 lbs. Looks like you are in good shape. The elevators should balance 12 to 25 degrees nose down. dd From: Iflycozy Date: Wed, 25 Mar 1998 22:35:37 EST Subject: Re: COZY: Elevator Weight I have a stupid question. In determining the elevator angle when dangling them upside down with wire from their hinges, do you measure the 12 to 25 degree angle from the top (bottom side) of the elevator or from the bottom (top side)? iflycozy@aol.com Date: Thu, 26 Mar 1998 10:00:57 +0200 From: Rego Burger Subject: COZY: Elevator Weight This magic angle of 12-25 degrees...to balance the elevator? Is it the angle of attack on the canard and is it a positive or negative angle? Rego Burger, web site: http://home.intekom.com/glen/rnb.htm (home e-mail) mailto:rnb@intekom.co.za RSA From: "Nat Puffer" Subject: Re: COZY: Elevator Weight Date: Thu, 26 Mar 1998 11:12:32 -0600 Dear Ian, It is very important for control surfaces (elevators and ailerons) to be balanced, so they either hang level or slightly nose down when suspended from their hinge points. The reason for this is to prevent flutter, which can cause catastrophic failure of structure. We don't give an absolute weight limit in the plans, because it is the distribution of the weight that determines balance. In other words, two elevators could have the same weight, but one would balance nose down, and the other trailing edge down. You need to be very careful during the construction to remove all excess epoxy (with a hair dryer), particularly near the trailing edge. You will need less fill material if you use peel ply. The top shape of the elevators is supposed to be concave (curved inward). Under no circumstances should you fill in this surface with micro to make it flat! Use the counterweights shown in the plans and check the balance before painting. If it is nose down, you have done good work. If not nose down, it is permissible to sand through part of the second layer of glass, top and/or bottom. The sanding will be most effective if concentrated toward the trailing edge. Painting will affect the balance. It is permissable to add a few layers of lead tape over the balance weights to offset the change in balance due to painting. As a consolation, we have never heard of a case of elevator flutter with either the Cozy or Long EZ, so it is very rare. With the ailerons, we want to over-balance. The ailerons seem to be more susceptible to vibration (different from flutter) than the elevators, and this causes wear of the hinges. Hinge wear can be compensated for by inserting thin-walled teflon tubing and a smaller diameter hinge pin. Regards, Nat ---------- > From: Ian DS Douglas > To: Cozy Builders > Subject: COZY: Elevator Weight > Date: Wednesday, March 25, 1998 8:07 PM > > Hi there, > > I was just looking over in the plans and I am unable to find the max > weight for the elevators. It says that the weight is important and that > they should point down once painted other than that?!? Mine currently > weigh 3lbs - 7.5 oz but I have to do some repairs (posted earlier). > With my dremel and 45 deg. wire brush tool I am able to remove a single > layer of glass with very good precision. What I want to know is what is > the max allowed weight is and if I am already close (still determining > fix vs rebuild). The shape is right on with templates, the balance is > good, and all of that brock hardware doesn't have to be stripped and > cleaned of old foam and glass if the max weight is achievable. > -- > Best regards, > Ian D.S. Douglas > MK0069 Date: Fri, 27 Mar 1998 09:14:57 -0500 From: Ian DS Douglas Subject: Re: COZY: Elevator Weight Nat, Thanks for the quick reply. I had thought that balance was of higher impotance than the overall weight (keeping the elevators under 4 lbs should not be a problem). When measuring the nose down angle is the line drawn from: the the centre of the torque tube to TE; a water line; or the top or bottom skin? -- Best regards, Ian D.S. Douglas MK0069 From: "Nat Puffer" Subject: Re: COZY: Elevator Weight Date: Sun, 29 Mar 1998 11:15:38 -0600 Dear Cozy Builders, Perhaps an explanation of why flutter occurs when control surfaces aren't properly balanced is in order. Let's say the elevator on the canard is trailing edge heavy. That means its c.g. is aft of the hinge point. So you hit an upward thermal gust which suddenly produces more lift on the canard and causes it to deflect upward (dihedral). If the c.g. of the elevator is behind the hinge point, the elevator tends to lag behind, just as though you pulled back on the stick. This produces even more lift and drives the canard upward until it reaches an elastic limit. Then the stored up energy causes the canard to return to its original position. But because the c.g. of the elevator is behind the hinge point, the elevator lags behind again, as though you pushed forward on the stick, causing the canard to deflect downward (anhedral), . When the canard reaches its elastic limit, it tries to return to its normal position, but the unbalanced elevator keeps driving it up and down, farther and farther each time until the canard fails. Now, catastropic failure of a composite canard or wing doesn't happen very often, like in a metal airplane, because glass can absorb much more energy without breaking than can metal. However, flutter can be a very terrifying experience even if the shaking doesn't break something. So it is worth the effort to make sure your control surfaces are balanced nose-heavy. The effect of flutter is sort of like resonance, where something is excited at the same frequency as its resonant frequency. In this case, the energy can build to very high levels and result in rapid fatigue failure of the resonating part. Best regards, Nat ---------- > From: David Domeier > To: Rego Burger > Cc: cozy_builders@hpwarhw.an.hp.com > Subject: Re: COZY: Elevator Weight > Date: Saturday, March 28, 1998 7:34 AM > > Rego, > > re "This magic angle of 12-25 degrees...to balance the elevator? Is > it the angle of attack on the canard and is it a positive or negative > angle?" > > Neither, Rego. > > It has something to do with how airflow coming across the canard > hits the elevators. I've tried to imagine the elevators being neutral > in balance and I think therein lies the danger of flutter. If the > elevator is loaded (balanced) nose down, it tends not to flutter because > it is not in that neutral zone, balance wise, where it can be induced by > top to bottom air flow. In other words the elevator does not vibrate > because it is loaded into the top air flow. It would seem that if it > were loaded the opposite direction it would also not flutter - but I do > not understand all the forces in play here so I would not think of > loading it nose up, trailing edge down. We know an elevator balanced > nose down will not flutter. Logically, it would seem the most dangerous > elevator is one balanced to neutral, but I don't know that for sure. > > dd > Date: Sat, 28 Mar 1998 08:23:55 -0500 From: David Domeier Subject: Re: COZY: Elevator Weight RE "I have a stupid question. In determining the elevator angle when dangling them upside down with wire from their hinges, do you measure the 12 to 25 degree angle from the top (bottom side) of the elevator or from the bottom (top side)? iflycozy@aol.com" I "think" this is the correct way to check elevator balance... 1. Insert the hinge rod into the elevator. It should protrude out both ends of the elevator. 2. Place each end of the rod on a surface where the rod can roll with the balance of the elevator. I used 2 old wraught iron lawn chairs with curved backs placed upside down. 3. The elevators are balanced right side up as they are installed on the canard. The elevator should balance 12-25=B0 trailing edge up, nose down, as measured on the flat bottom side of the elevator. This is a neat trick, lying on your back looking up at the bottom of the elevator while trying to gently place an angle finder on the bottom without desturbing it too much. I had to add some weight to both of my elevators, but they still come in at less than 3.9 lbs. Hope this helps. dd Date: Sat, 28 Mar 1998 08:34:53 -0500 From: David Domeier Subject: Re: COZY: Elevator Weight Rego, re "This magic angle of 12-25 degrees...to balance the elevator? Is it the angle of attack on the canard and is it a positive or negative angle?" Neither, Rego. It has something to do with how airflow coming across the canard hits the elevators. I've tried to imagine the elevators being neutral in balance and I think therein lies the danger of flutter. If the elevator is loaded (balanced) nose down, it tends not to flutter because it is not in that neutral zone, balance wise, where it can be induced by top to bottom air flow. In other words the elevator does not vibrate because it is loaded into the top air flow. It would seem that if it were loaded the opposite direction it would also not flutter - but I do not understand all the forces in play here so I would not think of loading it nose up, trailing edge down. We know an elevator balanced nose down will not flutter. Logically, it would seem the most dangerous elevator is one balanced to neutral, but I don't know that for sure. dd Date: Sun, 29 Mar 1998 16:20:31 -0500 From: Ian DS Douglas Subject: Re: COZY: Elevator Weight Nat asked me to send this to the group to help clear up some measurement references... "Ian, The commonly accepted reference is the chord line. See page 11-1 figure 1 for elevators and 19-9 Fig. 22 for ailerons. In the case of the elevators, the chord line happens to be parallel with the bottom surface. Regards, Nat" -- Best regards, Ian D.S. Douglas MK0069 From: lschuler@cellular.uscc.com Date: Mon, 30 Mar 98 10:46:56 -0600 Subject: Re[2]: COZY: Elevator Weight Nat Puffer wrote: >snip >In the case of the elevators, the chord line happens to be parallel with the >bottom surface. I hate to point this out and don't wish to start any word wars; but, I think accurate descriptions are necessary for understanding how our planes work. File this one in the FWW department or in the bit-bucket as appropriate: I believe the "chord" of any airfoil is an imaginary, straight line drawn from the most forward point to the most rearward point. If that is true, the bottom of the elevator is certainly not parallel to it's own chord line. The bottom is however, very flat; and, is used as the "reference" for determining hinge insert position, it's relative position to the canard and deflection angles. On the other hand, if the elevator is allowed to float relative to the canard (is installed), AND the chord referd to is of the overall canard and elevator combined, THEN one might be able to move the elevator (and the resulting chord line) such that the canard/elevator combined chord is indeed parallel to the bottom of the elevator at some elevator angular deflection. I havn't worked out the geometry, but I would bet that at some point along the elevator arc that the canard/elevator chord line is parallel to the bottom surface of the elevator, and that the line would also 'be' the bottom surface (or very close to it depending on the thickness of the TE). Feel free to correct my understanding. Larry Schuler lschuler@cellular.uscc.com From: Jim Hocut Subject: COZY: CH 11 - Elevator Offset Date: Thu, 17 Sep 1998 13:21:28 -0400 I finally got around to assembling my elevator stuff yesterday and noticed a small discrepency in the Brock parts others may want to make note of. The torque tube offsets are made slightly different than the drawings, a 1/8" shoulder has been added where the offset is inserted into the torque tube and spool piece. No big deal, but the spool piece will need to be 1/4" shorter than called out in the plans, and the torque tubes 1/8". (The plans DO say to check all these dimensions before bolting everything together, but maybe this tidbit of information might save someone some head scratching in the future). Jim Hocut jhocut@mindspring.com