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Author Topic: Stabs and the "AVANTI" for Ted.  (Read 18261 times)

Offline Ron Varnas

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Stabs and the "AVANTI" for Ted.
« on: March 08, 2006, 01:56:39 AM »
Ted, the recent Stab position discussion reminded me of a favorite design that you'd be very familiar too......the "AVANTI" by Bob Baron, everything on this design I love still today....just one thing that always made me wary about building one was in the in line Stab location.......and hearing back in those days
that this set up is very hard to trim, I'd really like your thoughts on this and just how well did the AVANTI fly as a model, knowing full well the desiginer was one
of the best fliers around :)
RJV Melb. Australia

Offline Ron Varnas

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Re: Stabs and the "AVANTI" for Ted.
« Reply #1 on: March 09, 2006, 05:12:06 AM »
Oh well.......no interest in the question.......means no further interest from
me on this particular forum  >:(
RJV Melb. Australia

Offline Crist Rigotti

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Re: Stabs and the "AVANTI" for Ted.
« Reply #2 on: March 09, 2006, 11:01:10 AM »
Ron,
You're kidding...right.  Barely 28 hours have passed since your first post.  Maybe Ted has been travelling or something.  Be a bit more patient.
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Offline ash

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Re: Stabs and the "AVANTI" for Ted.
« Reply #3 on: March 10, 2006, 01:35:56 AM »
The fact that half the US stunt community are travelling the highways to Tuscon now or soon seems like a fair excuse to me too...

Not that I really have first hand experience myself, but the Avanti has spawned several offspring at the hands of master modellers, so my guess is that it rates highly. My next *serious* effort has Avanti heritage via Brad Walker's series of designs that he has on his website.
Adrian Hamilton - Auckland, NZ.

Offline Ron Varnas

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Re: Stabs and the "AVANTI" for Ted.
« Reply #4 on: March 10, 2006, 01:42:38 AM »
Ok, I digress ........I mistakingly looked at  the different time postings,
my apologies Chris , Ash & especially  Ted...........by the way how do I find Brad
Walkers website :-[
RJV Melb. Australia

Offline ash

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Re: Stabs and the "AVANTI" for Ted.
« Reply #5 on: March 10, 2006, 02:06:43 AM »
No problem, Ron.

Brad's plans that are Avanti derived:
http://www.egpworld.com/ultrahobby/teamuhp/Zone%202.htm
http://www.egpworld.com/forum/default.aspx?f=2&m=1989
http://www.egpworld.com/ultrahobby/download/solace.pdf

And the attendant forum:
http://209.190.111.138/forum/default.aspx

His designs don't look anything like the Avanti or Patternmaster, but that is where his aerodynamics package comes from.
Adrian Hamilton - Auckland, NZ.

Offline Ted Fancher

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Re: Stabs and the "AVANTI" for Ted.
« Reply #6 on: March 25, 2006, 12:10:35 AM »
As a matter of fact VSC was absolutely awesome and I didn't look at a computer once while I was enjoying it.

Having said that...

I flew against and with Bob a number of times including at the 1982 World Champs.  He was a wizard at making a variety of designs fly very well.

It just so happens that the Avanti is the one design of his that I actually flew myself after a nats (I forget which) at which he finished a very competitive fourth.  I was also in the top five that year but don't remember where.

Like many of Bob's designs and set-ups (witness the Humbug and others) the entire package was unusual, not only the layout of the wing, tail and thrustline.  It had extremely slow controls even using an abnormally wide line spacing.

Once again, Bob had whipped most everyone there just minutes before I was able to fly the airplane so the following comments must say more about me than they do the competency of the airplane.

I found it very difficult to fly at least in part because I am a finger tip flyer and control inputs with which I was comfortable barely budged the Avanti from level flight.  It seemed very difficult to fly straight and level despite the insensitivity.  It seemed to be quite a bit more tail heavy than I would have prefered and the combination of the above made me kind of nervous flying it.  As a result I really didn't do much more than a couple of loops that made me nervous and I was a bit concerned about landing it.  As it happened it pretty much just drifted down and touched down after the engine quit.

I must state strongly again that this uncomfortable feeling was probably 90% the result of the difference in control set-up and sensitivity preference between Bob and me. I say again, this exact airplane just pretty much beat up on 90% of the very good pilots at the nats.

I did, as a result of that flight, develop a strong inclination to avoid in-line setups for fear that the feeling of instability I disliked might well have been due at least in part to that layout.

My aversion was so great that even when I built a KA-10 from Tom Dixon's kit a number of years ago that I modified the tail location to a more conventional inch and a half or so above the thrustline/wing centerline.  Unfortuanately, this airplane has been hanging on the wall of my shop in base color for several years and has yet to see the light of day for flying.  This will likely change this summer as I need something new to fly at the Nats (I'm afraid they won't let me fly the old original Trivial Pursuit again) so I'll probably put a little trim paint on the KA-10 and see what happens.

It'll be real retro...it's set up for an OS .52 Surpass four stroke...a concept that appears to have run its course.  Oh, well. Better late than never.

I'll spend a couple of paragraphs addressing my theory about why inline designs may be sensitive and tend toward instability in level flight (see remarks about the in-line Beringer airplanes from many who have built them and found them to have the same "balancing on the head of a pin" feeling in level flight that requires constant attention).  Again, please recognize I'm only passing on what I've heard, I've not flown one -- but have been beat by them!)

I feel that stability, that locked in feeling you get from some airplanes, comes at least in part from some aerodynamic tension created by a disparity in aerodynamic loads on the airframe.  Pitching moments, variations in CG relative to the Center of lift of the wing, drag moments that attempt to pitch the airplane, etc.

Full scale planes exhibit similar characheristics and in some cases, such as aerobatic flying teams like the Blue Angels and Thunderbirds the pilots purposely trim the controls so that some tension is built into the system, i.e. they trim the aircraft nose down so that it wants to pitch down and must be held in the pitch attitude required for the formation maneuvers.  By working against tension in the system, constantly applying a bit of up elevator to hold the aircraft precisely on the third rivet past the air intake of the jet a few feet away from him, the pilot is able to literally hold the airplane where he wants it.

If he were, instead, to trim the ship for hands off level flight every little aerodynamic nudge would upset that precise attitude and have to be readjusted.  Can you understand what I'm saying?

I feel the in-line stunter is more like the latter case than the former.

By having the wing below the thrustline and/or the stab above or (in most cases, both) a stunt ship has some built in tension between the aerodynamic forces acting on it.  It might only be a tiny bit but it is enough to require that the pilot work against that tension and the result is a locked in feeling.

When we purposely design ships to eliminate that tension (the whole idea between in-line setups as I understand it) those source of tension in the system are mitigated or even lost.  It now becomes necessary for the pilot to absolutely concentrate and correct every aerodynamic foible that militates against that lack of tension.  When any force wants to pitch the ship up or down it will require pilot initiated corrections.  If you're a super pilot like Bob Baron or the Beringers you simply deal with that and remain utterly focused on doing so.

In my limited exposure I found myself totally unable to cope with that sort of feel in the airplane.  I also suspect the reason for the incredibly slow control response had to do with attempts to mitigate or reduce the upset caused by small pilot inputs while flying level.

Once again, guys.  I was asked for my opinion and that's all this post is.  My experience was instructive enough that I would be unwilling to build such an airplane expecting to fly it competitively.

I do have on the shelf now a multi time World Champion Skywriter kit which is an inline design.  Because I've pretty much burned out on pursuing big trophies any more I'm developing more interest in trying out other people's successful designs to compare them to those of my own that I competed with for so many years.  I probably won't build it immediately but the primary reason I will build it is to have an in-line ship of my own that I can trim to my preferences.

I could well find out I like it.

Ted

Offline Bill Little

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Re: Stabs and the "AVANTI" for Ted.
« Reply #7 on: April 13, 2006, 07:13:10 AM »
Hi Ted,

I think you have said what we all must find out for ourselves.  Some of us "like" a certain style of plane that flies a certain way while others like something different.  Maybe WAY differrent!

You have been highly successful and have found the "numbers" that suit your style, pretty much.  The fact that you have been doing this since the rocks were cooling may be a factor.  ;D

I DO believe something you told me a while back:  "Find one design that flies like you like, and build that.  Then build another like it.  I believe that when we DO find the style that suits us, we will get better much quicker at this event.

Problem is, I have had to build SO MANY to finally understand what I DO like!  x:
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Offline Randy Powell

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Re: Stabs and the "AVANTI" for Ted.
« Reply #8 on: April 13, 2006, 03:42:17 PM »
I think this a a really good point. I recently built a Walter Umland Cobra. I built it exactly as the plans indicated and found that I didn't particularly like the way it flew. The control are sensitive and you have to stay on it all the time. It doesn't fly at all badly, just very different from what I'm used to. I think if I get enough time on it, I will get used to it and be able to fly it reasonably well, but I don't know that I will ever be "comfortable" with it. I just prefer a much slower, more deliberate control system that has the locked in feel that Ted talks about. The Cobra is a flick your wrist sort of plane.
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Offline Jim Pollock

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Re: Stabs and the "AVANTI" for Ted.
« Reply #9 on: April 14, 2006, 08:16:49 PM »
Randy,

Can you cut down you handle spacing?  Could you also afford about a 1/2 ounce of extra weight in the nose.  Lastly, maybe you've already tried these solutions?

Jim Pollock

Offline Randy Powell

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Re: Stabs and the "AVANTI" for Ted.
« Reply #10 on: April 21, 2006, 03:02:25 PM »
Jim,

For my plane, the handle spacing is already about 5% narrower than I am really comfortable with just to tame it down and it's nose heavy as it is. By going to a plastic spinner, a trick plastic tank (my consruction) and some judicious pruning, it now balances per plan.
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Offline phil c

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Re: Stabs and the "AVANTI" for Ted.
« Reply #11 on: April 22, 2006, 03:27:15 PM »
If it truly is nose heavy, then unfortunately the controls aren't right.  Probably needs a shorter arm on the bellcrank.  Changing the bellcrank arm is similar to trimming handle spacing, but not exactly the same.  Narrowing line spacing slows the controls by reducing the lever arm between the handle and BC,reducing the bellcrank movement.

Going to a shorter arm on the bellcrank reduces the control travel without changing the bellcrank travel.  Ya gotta love fully adjustable controls when you run into a problem like this.
phil Cartier

Offline John Lindberg

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Re: Stabs and the "AVANTI" for Ted.
« Reply #12 on: April 25, 2006, 01:55:48 PM »
Ted, one plane I have always been interested in is the "Chizler", I believe you flew one for awhile. How did you like it? I think it is Classic legal. Thanks, John Lindberg. b1

Offline Bill Little

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Re: Stabs and the "AVANTI" for Ted.
« Reply #13 on: April 25, 2006, 07:56:20 PM »
Ted, one plane I have always been interested in is the "Chizler", I believe you flew one for awhile. How did you like it? I think it is Classic legal. Thanks, John Lindberg. b1

Hi John,
Not Ted, but I have seen a Chizler fly.  In the magazine article (it is Classic Legal, no problem) Mr. Mathis plainly says that it is a Nobler wing and mostly Nobler lay out.   Which means it flies like a good Nobler with a nicely different look!  I know Fast Richard flew his in three NATS, but I'm not sure if it was just the same one refinished three times or new ship(s).  The one I saw flew quite nice!

I hope Ted puts his word in!
« Last Edit: April 26, 2006, 07:01:45 PM by Bill Little »
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Offline John Lindberg

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Re: Stabs and the "AVANTI" for Ted.
« Reply #14 on: April 26, 2006, 07:48:04 AM »
Thanks, Bill, anyone else out there have an opinion on the Chizler? Rather unique plane, I believe. ;D

Offline Ted Fancher

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Re: Stabs and the "AVANTI" for Ted.
« Reply #15 on: April 26, 2006, 06:36:25 PM »
Hi John,

I did, indeed, build a Chizler for a VSC many years ago and have flown it off and on at a variety of VSCs and once at the Nats in Classic.

It is without a doubt my favorite Classic ship and ranks right up there with the best of any ships I've flown over the years regardless of the designs age or heritage.  Mine was a quick and dirty construction job of about five weeks which resulted in a very "modest" finish which includes both Shareen and my finger prints in the clear coat on the flaps --  which were installed in a motel room on the drive to Tucson for that long ago VSC.

The airplane does for a fact fly like a very good Nobler and the fuse shape gives it a distinctive appearance that seems to enhance the sides of angled maneuvers while having just that hint of curvature that also desguises minor glitches...sort of like Al's big profiled semi-scales, part of which was almost always at five feet.

I flew mine with a Big Art modified OS Max .35s which was perfectly adequate for power when flown on slightly less than 60' of wire.  Modern powerplants would, in my estimation, be a bit much for it at any reasonable weight.  The Merco Rustler is one modern engine that would do the job very pleasantly and give you a choice of engine run types, either a classic 4-2-4 with a five and half or six inch pitch or a wet constant two stroke with 4.5" of pitch or so.  The engine is perfectly comfortable up to just under 10K which pretty much sets the minimum pitch at around that 4.5 level.

My ship was not particularly light, around 43oz or so if memory serves and on solid lines felt like it was attached directly to the flyers hand.  Some of my very best flights ever were flown with that airplane.

You might have developed the notion I like it a lot.

You'd be right.

Ted

p.s. RSM has a laser cut kit available now and if I were to build another one that's the way I'd go.  I just finished an RSM Ruffy for VSC last month and it was a delight to build and flies pretty well (not yet to the level of the Chizler, however).

Offline phil c

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Re: Stabs and the "AVANTI" for Ted.
« Reply #16 on: April 26, 2006, 06:55:22 PM »
If I remember the article right, the Chizler used the Nobler wing and tail.  Just had the nice, curvy, carved block fuselage.
phil Cartier

Offline Bill Little

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Re: Stabs and the "AVANTI" for Ted.
« Reply #17 on: April 26, 2006, 06:58:48 PM »
If I remember the article right, the Chizler used the Nobler wing and tail.  Just had the nice, curvy, carved block fuselage.

Which is exactly what I wrote in my reply!  I was semi quoteing the article that I had in my hands.  %^

"Hi John,
Not Ted, but I have seen a Chizler fly.  In the magazine article (it is Classic Legal, no problem) Mr. Mathis plainly says that it is a Nobler wing and mostly Nobler lay out.   Which means it flies like a good Nobler with a nicely different look!"
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Offline John Lindberg

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Re: Stabs and the "AVANTI" for Ted.
« Reply #18 on: April 26, 2006, 08:02:02 PM »
The Chizler sounds like a good one, have to seriously consider it, thanks all for the replies. Dick Mathis-who I believe designed the plane-has some interesting stuff. I have his Excalibur, and when I put a LA 46 on it, with a Randy Smith Bolly 11x6 prop, it really became a nice plane, one of the last kits I got from Andy Nehring before he absconded with the investors funds. Anyone heard anything about him? b1 

Offline Ted Fancher

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Re: Stabs and the "AVANTI" for Ted.
« Reply #19 on: April 27, 2006, 11:29:44 PM »
Just as an aside, somebody at VSC was saying Dick Mathis was excited about stunt again and was planning to come back and fly again,  That would be great.

I saw Dick fly the Chizler in 1967 at the last Los Alimitos Nats.  He came in second to Bart Klanski in a very good competition.  Two really, really good flyers flying outstanding designs.  I think that was also the year Bob Baron placed real high with the Humbug.  I think he was fourth if memory serves.  Some very contrasting flying there.

Ted

Offline John Lindberg

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Re: Stabs and the "AVANTI" for Ted.
« Reply #20 on: April 28, 2006, 03:25:57 PM »
Well, maybe Dick will have a few more designs for us to ponder, that would be nice. ~>

Offline Brett Buck

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Re: Stabs and the "AVANTI" for Ted.
« Reply #21 on: May 02, 2006, 09:29:00 PM »

I'll spend a couple of paragraphs addressing my theory about why inline designs may be sensitive and tend toward instability in level flight (see remarks about the in-line Beringer airplanes from many who have built them and found them to have the same "balancing on the head of a pin" feeling in level flight that requires constant attention). 



    I know I am coming in very late on this one, but since I did have a comment about in-liners in response to Tom Dixon's rather critical/hostile letter to SN a few years ago about tail incidence, and tangentially about in-liners, I suppose I can comment.

     I don't think there's any doubt that most "in-liners" are very "wafty" or funny-feeling around neutral, compared to regular stunt planes. I probably even saw Ted's Avanti flight way back when, well before we met. I was incrediby impressed with the Bob flew it, in fact, in many ways, my mind was set on what good stunt patterns looked like by the way Bob flew it.

    But - as anyone who read my first shot at a design column could see, the concept is fundamentally flawed. The idea is that since the airplane should turn the same inside and outside, it ought to be "symmetrical" and, of course, that means that you should put the engine, wing, and tail all in a line so that there is nothing that "favors" up or down. Great idea, unfortunately, unless you have drop gear, fin/rudder that looks like the tail on a largemouth bass (symmetrical from the side view), and contra-rotating propellor and engines, you have plenty of other assymetry already, so putting the engine, wing, and tail in line doesn't accomplish the  goal of making the airplane neutral in terms of up and down response. In fact, an in-liner will probably need quite a bit more downthrust and/or positive stab incidence, since you don't have the *advantage* of having the engine trying to nose you down to compensate for the precession like you did with a higher thrust line. I haven't thought it through whether or not the higher stab helps or hurts with this. I suspect it *probably* helps compensate, too, but I couldn't explain it in words.   Point being, the goal of equal/neutral inside/outside response is NOT accomplished by making an in-liner, in fact it probably hurts.

   But there is one whoppingly obvious (to me, anyway) disadvantage, and it's most evident in level or low-g flight. The turbulence off the wing in level flight streams almost straight out behind it. There's very little lift (just the weight) and it doesn't take much Cl to create it. Therefore the "downwash" is very minimal. So, bingo, the stab/elevator is running in the wing turbulence in level flight. And very tiny changes in the Cl from slight corrections at the controls move the turbulent area up and down around the stab. So not only is it in turbulence, slight corrections drastically change the turbulence, and thus the stab effectiveness. So you make a slight correction, or a slight perturbation comes along and loads or unloads the wing, and all of a suddenly your control input works 50% better or 50% worse, and you never have any idea what it's going to do next. Leading to that "vague" feeling.

     Of course, it clears itself up pretty well in harder maneuvers, and may be more equal in terms of stab effectiveness when you start getting to higher Cl as the downwash is moved away from the stab. But now, you have a situation where it works very weakly and unpredictably around neutral and really comes on strong in maneuvering. That might *sound* good, but I think that something that drastically changes charactersitics depending on the conditions is a formula for unpredictablity and inconsistency. Maybe you can practice a lot every day and get used to it, and used to how it's different in different conditions, but you are gonna have a bit of a time trying to just pick it up and fly it well the first time, or anytime the engine runs a little different, or when the air density changes, or the wind changes, or (etc).

   Never mind that almost everything that we have done in the past 20 years in terms of design and trim is geared towards making the airplane more positive and responsive around neutral. This arrangement has the precisely opposite effect.

   And the Avanti in particular has another, quite intentional, feature that encourages this "vague" feeling, and that's the old "stab bigger than elevator" trick. In fact, the plans show a rather exaggerated case, with the stab TE about 1/2" and the elevator about 3/16 (or something like that). That works on the same principle, creating turbulence that makes the stab less effective around neutral to "smooth it out". So in this case it's a sort of double whammy.

   The very last thing I think you want is a system where you move the handle a lot, and not much happens, then you move it a little more, and all of a sudden it "grabs" and really responds.


     Once again, a lot of people have been trying to *prevent* exatly this effect. Paul Walker started it, and I have subsequently ripped off the idea. We are actually rounding off the edges at the stab/elevator (and wing/flap) hinge line to reduce the turbulence and make the controls *more* effective around neutral than they would be otherwise. The 3 airplanes upon which I have done this have been *very very positive* around neutral and nonetheless track very well. With some remarkably aft CGs at time. Of course, I am also willing to build in or dial in the necessary positive incidence, and not feel "guilty" about it.


   So it's no wonder to me that the Avanti was a little tricky to fly. Even without knowing the historical record, you could pretty well predict that a very superior pilot (and make no mistake, Bob Baron was in general a very superior pilot) could fly it well, on some occasions - but probably not consistently from month to month. Which pretty much was what happened.

     Brett



Offline RandySmith

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Re: Stabs and the "AVANTI" for Ted.
« Reply #22 on: May 03, 2006, 10:34:51 PM »
Not  to mention  that  if you mount the  engine inverted  you  get  a  bad out of  CG   range  plane  that  will have the  line tension   tight-looser   when  you   maneuver  insides  and  outside.
  I found  that in-lines  need  to  be  sidewinder  mounted,  this  has  proven  to  be  a bad  idea  because  most all  Stunt designs  have a  far  stiffer  fuselage, for  inverted or  upright engines  than  they  do  for  side mounted  engines. 
This  has  given  many  people  fits,  and  has  been the  cause  of  many  bad  engine  runs.
So  if  your  gonna  build one  you have  a  few things  to think about

Randy

Offline Brett Buck

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Re: Stabs and the "AVANTI" for Ted.
« Reply #23 on: May 03, 2006, 11:03:05 PM »
Not  to mention  that  if you mount the  engine inverted  you  get  a  bad out of  CG   range  plane  that  will have the  line tension   tight-looser   when  you   maneuver  insides  and  outside.
  I found  that in-lines  need  to  be  sidewinder  mounted,  this  has  proven  to  be  a bad  idea  because  most all  Stunt designs  have a  far  stiffer  fuselage, for  inverted or  upright engines  than  they  do  for  side mounted  engines. 
This  has  given  many  people  fits,  and  has  been the  cause  of  many  bad  engine  runs.
So  if  your  gonna  build one  you have  a  few things  to think about


    Yeah, but I have a plan for that - I am waiting for the PA152 opposed twin. One PA76 cylinder on top, one on the bottom, nice and symmetrical, no vibration. Then a gearbox to drive the contra-rotating props, and drop gear. Then, we'll be all set in our new world of perfect symmetry!

     Brett

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Re: Stabs and the "AVANTI" for Ted.
« Reply #24 on: May 06, 2006, 06:23:57 PM »
Great, now ya tell me. Right when I get the sucker to this stage...(See Pic) Top block is just sitting there, but the wing and tail are locked and loaded. Oh well, I've got the full tilt boogie Tom Morris adjustable controls in it so I can hopefully trim out any of the anomalies that may show up. You all sure know how to hurt a guy  :-[

On a more serious note, I have flown Owen Richards Avanti and it grooved like a son of a gun and turned decently. Only problem was some roll trim (I think he could have pulled some tip weight) but none of what Ted describes. It's hard enough for us mere mortals to build two of the same design that fly exactly the same, which makes determining what's design flaw versus trim issue a little difficult... None the less, it should be a fun adventure with my RO76 under the hood.  (sorry Brett, I only own the one, so no twin!)

I did make a small design change now that I think about it, I did not want to use the shaft extension scenario shown on the plans, so I shortened the nose to meet my RO76 thrust washer rather than put the "slightly heavier than designed for" engine further forward.

EricV

Offline Brett Buck

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Re: Stabs and the "AVANTI" for Ted.
« Reply #25 on: May 07, 2006, 06:21:37 PM »
Great, now ya tell me. Right when I get the sucker to this stage...(See Pic) Top block is just sitting there, but the wing and tail are locked and loaded. Oh well, I've got the full tilt boogie Tom Morris adjustable controls in it so I can hopefully trim out any of the anomalies that may show up. You all sure know how to hurt a guy  :-[

On a more serious note, I have flown Owen Richards Avanti and it grooved like a son of a gun and turned decently. Only problem was some roll trim (I think he could have pulled some tip weight) but none of what Ted describes. It's hard enough for us mere mortals to build two of the same design that fly exactly the same, which makes determining what's design flaw versus trim issue a little difficult... None the less, it should be a fun adventure with my RO76 under the hood.  (sorry Brett, I only own the one, so no twin!)
EricV


    Hey, Baron made mincemeat out of one team trials (must have been '81) so it can be flown well. I also recall that some of Jim Casale's airplanes were supposedly pretty stock Avantis - and he seemed to do OK!

   Of course, he also made mincemeat out of most of us at the 96 NATs flying a pretty much stock Patternmaster with the prototype Double Star 60, at least until the wind came up.

    Just out of curiosity, why did you glue in the wing and tail before you had the fuselage done? Seems like it would be a lot more prone to getting misaligned if you didn't put the blocks on exactly right. I usually have the fuselage almost complete before I even try to put on the tail - only missing bit is the block that goes right over the stab. And I am very, very carefull installing that, since it's relatively easy to rack the aft fuse out of square, even with the extensive diagonal bracing I use. Installing the tail is usually the last thing I do.

    Brett
     

Eric Viglione

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Re: Stabs and the "AVANTI" for Ted.
« Reply #26 on: May 08, 2006, 07:55:16 AM »
Brett said:Just out of curiosity, why did you glue in the wing and tail before you had the fuselage done? Seems like it would be a lot more prone to getting misaligned if you didn't put the blocks on exactly right. I usually have the fuselage almost complete before I even try to put on the tail - only missing bit is the block that goes right over the stab. And I am very, very carefull installing that, since it's relatively easy to rack the aft fuse out of square, even with the extensive diagonal bracing I use. Installing the tail is usually the last thing I do.

    Brett


Hi Brett - Well, a few reasons I guess, none of them that great... The top block containing such a large portion of the wing cutout threw me a little on this design. It's been tacked on, but removed for hollowing. It should fit back fairly well.

I also wanted to make sure I NAILED the controls on this one, and have found that keeping the B/C neutral when the control surfaces are level is very important to the way I perceive the feel of the plane in flight. Even with adjustables, the BC rod length is only available till you put on the blocks.

And I guess finally that I constantly re-check alignment all the way out from here anyways and don't force fit anything that's going to tilt the stab.

Even fully assembled previous models where I've silkspan'ed the fuse, I've had the dope pull a tilt into the stab, so I've gone to epoxy and 1/2oz glass cloth. I try to keep a close eye on it just the same. I usually block up the stab at that point while the epoxy on the fuse dries, and so far that method seems to be the best for keeping the stab level.

As for others doing well with the Avanti or Avanti based plane, well that is one of the reasons I started one in the first place, plus the major "cool factor" of the design. I'm going to be in the finishing stage soon, and can't wait to see how she handles!

EricV

Offline Bill Little

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Re: Stabs and the "AVANTI" for Ted.
« Reply #27 on: May 09, 2006, 12:31:54 PM »
10 years ago, I built Bill Werwage's "little" Junar.  It is an inline piped ship that some of you will remember, he got a concours with it, yellow and maroon.

I used a 40VF and it's around 660 sq. in., I'm guessing.   It flew very nicely, until a gust hit it at Rock Hill on the bottom of the outsides of the square 8s and I had to glue the two pieces of the fuselage back together!  I got to the NATS and a motor mount came loose.  I guess the crash damaged it, and the flights between the repairs and NATS were enough to work it loose.  I had one really poor flight, and helped my son the rest of the meet.

I hope to build another one, since the wing is still intact!
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Re: Stabs and the "AVANTI" for Ted.
« Reply #28 on: May 09, 2006, 01:55:51 PM »
10 years ago, I built Bill Werwage's "little" Junar.  It is an inline piped ship that some of you will remember, he got a concours with it, yellow and maroon.

I used a 40VF and it's around 660 sq. in., I'm guessing.   It flew very nicely, until a gust hit it at Rock Hill on the bottom of the outsides of the square 8s and I had to glue the two pieces of the fuselage back together!  I got to the NATS and a motor mount came loose.  I guess the crash damaged it, and the flights between the repairs and NATS were enough to work it loose.  I had one really poor flight, and helped my son the rest of the meet.

I hope to build another one, since the wing is still intact!


I remember it  very well, It was  Stunning  to Curt Contrata  who was  gazing at it.  Billy used it in the worlds  an  had one of the OPS 40 REs in it.

 Right after  that Billy built another   Junar  with the  engine  mounted sidewinder, so the vertical CG  would  be  better in alignment.

The only Problem he had with that one  was  broken  homemade  headers  all  the time.

Randy

Offline Bill Little

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Re: Stabs and the "AVANTI" for Ted.
« Reply #29 on: May 12, 2006, 07:12:21 AM »
I remember it  very well, It was  Stunning  to Curt Contrata  who was  gazing at it.  Billy used it in the worlds  an  had one of the OPS 40 REs in it.

 Right after  that Billy built another   Junar  with the  engine  mounted sidewinder, so the vertical CG  would  be  better in alignment.

The only Problem he had with that one  was  broken  homemade  headers  all  the time.

Randy

I remember teh Geo XL at the '93 NATS having the header problems that really cost Billy that year. 

I was happy eith the "little" Junar at the time because it was more the size of the SV-11 compared to the USA-1 size plane that the "regular" Junar, and subsequent Geo XL were.


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Offline Steve Fitton

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Re: Stabs and the "AVANTI" for Ted.
« Reply #30 on: May 12, 2006, 02:13:13 PM »
Egad, I'm another Avanti owner enlightened "too late"!!! ;D

I have an Avanti 50 (approx 600 sq) completed and an Avanti 60 under construction.  So, if nothing else, I'll be able to contribute some empirical flight observations as trimming progresses.  So far, the model has only one flight, which demonstrated that it was grossly tail heavy but still had excellent pitch stability in level flight.  It was stuntable but with the tail heavy condition pitch rates were excessive and I discontinued the maneuvers because I was afraid the explosive corners might stress the wings too hard or lead to it getting away from me (PIO) in the square 8.  Nose weight has been added and the model awaits more favorable wind conditions for more flights.  This Avanti 50 example uses flat stab/elevator, in 3/8th and 1/4 thicknesses respectively.
  The original Baron Avanti plans show the dramatic disparity in stab/ele thickness, using a wedge shaped stab to 1/2" and a 1/4" elevator.  The newer Avanti 60 plans show a much different contouring of the stab, sort of an airfoil, albeit with the high point set back a bit far, still 1/2" at max, but reducing in thickness so that they blend into the 1/4" thickness of the elevators without a dropoff.  Dixon had those plans drafted off a set of Baron hand drawn plans, I don't know if Baron had changed the stab contour or if Dixon, or the person who drafted the CAD version of the plan, made it.  Some of this discussion is germaine to my current project, as I was planning to to a slab 1/2" stab and 1/4" elevators, although I was already debating using 3/8th for the elevators.
  The Yatsenko planes seem to feature the highly insensitive at neutral/exponential "boost" as the controls are moved.  When Derek Barry flew Orestes Shark last spring he commented on the pronounced feel to the controls-totally dead at neutral and then coming on in a hurry as you yanked on the handle.  Obviously, it was not a "totally dead, then too abrupt" feel, but something in that neighboorhood.
  At any rate, time will tell with my own Avanti programme.  I'll post any flight info s it comes available....

Steve
Steve

Offline Louis Rankin

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Re: Stabs and the "AVANTI" for Ted.
« Reply #31 on: May 12, 2006, 03:48:54 PM »
Steve,

I too am in the process of building an Avanti 60, so have been following this thread with interest.  Yes the stab is thick and elevator thinner, I had been debating making the elevator thicker also, maybe 5/16.  I am doing a quick but tasteful build so may not shape and taper the stab and elevator but leave them flat, flaps also.

I do like the looks and have seen Tom fly his several times.  Let me know how your build progresses.
Louis Rankin
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Offline Jim Pollock

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Re: Stabs and the "AVANTI" for Ted.
« Reply #32 on: May 13, 2006, 01:12:40 PM »
Well of course,

This begs the question could the Avanti be improved by a re-design to move the stab/elevator above the wing?  Just thought I would try for some enlightenment here
...... ::)  f~   %^   n~

Jim Pollock   :o

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Re: Stabs and the "AVANTI" for Ted.
« Reply #33 on: May 13, 2006, 05:18:08 PM »
Well of course,

This begs the question could the Avanti be improved by a re-design to move the stab/elevator above the wing?  Just thought I would try for some enlightenment here
...... ::)  f~   %^   n~

Jim Pollock   :o

Then it wouldn't be an AVANTI!   n1 y1 <=  f~ **) **) j1 j1
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Offline Bill Little

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Re: Stabs and the "AVANTI" for Ted.
« Reply #34 on: May 13, 2006, 05:20:17 PM »
Actually, that *might* be why Bob built the Patternmaster (with Avanti looks) to win the '96 NATS?  Guess we'll never know, unless Tom Dixon has a line on that reasoning.
 ???  %^
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Offline Brett Buck

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Re: Stabs and the "AVANTI" for Ted.
« Reply #35 on: May 13, 2006, 10:31:25 PM »
Actually, that *might* be why Bob built the Patternmaster (with Avanti looks) to win the '96 NATS? 

       I don't know what he was thinking about the 96 NATs, but the story went around in the mid-80s that he had said something along the lines of "I can do 6 good flights out of 10 with the Avanti and 9/10 with the Patternmaster". The provenance of that story is somewhat dubious, but it sounds plausible.

     Brett
   

Offline Steve Fitton

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Re: Stabs and the "AVANTI" for Ted.
« Reply #36 on: May 15, 2006, 10:19:18 AM »
Steve,

I too am in the process of building an Avanti 60, so have been following this thread with interest.  Yes the stab is thick and elevator thinner, I had been debating making the elevator thicker also, maybe 5/16.  I am doing a quick but tasteful build so may not shape and taper the stab and elevator but leave them flat, flaps also.

I do like the looks and have seen Tom fly his several times.  Let me know how your build progresses.

Louis,

  When I talked to Tom last week, he said the thickness of the stab was more a structural consideration than aerodynamic.  The stab was 1/2" for the worst-case strength scenario, a builder airfoiling the stab down and covering it with film instead of some more rigid finish.  Tom said that in the case of the Avanti and PM Baron had already come to the conclusion that even thickness (or at least less of a thickness disparity) was the way to go.  The plane that disintegrated at the 98 Nats had equal or near equal thickness surfaces.  The Avanti 60 plans Tom made up showed Tom's interpretation of the revised Baron stab with Tom's preference for 1/2" thickness for strength.  The plans note the 1/2" tapering down to about 1/4" at the hingeline.
As an aside Tom said that the triangular stab shape on the original Avanti plans was due to some structural issues with the foam stab cores Bob was using.
  Since I use film (egad!) on surfaces such as flaps and tail surfaces I usually do what you do Louis, eg, flat slab surfaces with rounded edges.  They are at least easy to work with if not optimium aerodynamically, although if I recall, the Impact uses flat surfaces as well...On the Avanti 50 I used 3/8th thick stab and 1/4 elevator, on the 60 I am using 1/2 stab and 3/8 elevator.

Steve

PS Eric, is that the Green Cowl of Doom I see in that photo you posted? >:D
Steve

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Re: Stabs and the "AVANTI" for Ted.
« Reply #37 on: May 15, 2006, 01:24:21 PM »
 f~"Green Cowl of DOOM!"

Yeah, and if you look a little to the left you will also see the Balsa Cowl of Enlightenment. x:

I'm saving the GCoD for any alternate engine configs that may arise. Maybe by then I'll be in the right frame of mind to finish it.

Thanks for rubbing it in....ahemm I mean noticing it.  b1

EricV 

Offline Steve Fitton

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Re: Stabs and the "AVANTI" for Ted.
« Reply #38 on: May 15, 2006, 01:33:31 PM »
Maybe you can feed the Green Cowl of Doom to your local alligator.  Sounds like they are on a rampage this year.  Eating that foam and fibreglass may convince them to stay away from humans.... y1
Steve

Offline Brett Buck

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Re: Stabs and the "AVANTI" for Ted.
« Reply #39 on: May 15, 2006, 11:36:10 PM »
Louis,

  When I talked to Tom last week, he said the thickness of the stab was more a structural consideration than aerodynamic.  The stab was 1/2" for the worst-case strength scenario, a builder airfoiling the stab down and covering it with film instead of some more rigid finish.  Tom said that in the case of the Avanti and PM Baron had already come to the conclusion that even thickness (or at least less of a thickness disparity) was the way to go.  The plane that disintegrated at the 98 Nats had equal or near equal thickness surfaces.  The Avanti 60 plans Tom made up showed Tom's interpretation of the revised Baron stab with Tom's preference for 1/2" thickness for strength.  The plans note the 1/2" tapering down to about 1/4" at the hingeline.
As an aside Tom said that the triangular stab shape on the original Avanti plans was due to some structural issues with the foam stab cores Bob was using.
  Since I use film (egad!) on surfaces such as flaps and tail surfaces I usually do what you do Louis, eg, flat slab surfaces with rounded edges.

    That all seems logical enough. Although I would point out that flat parts are less than optimum use of the weight, as far as stiffness goes. Some curve to the surface helps the stiffness sginificantly. It's a lot easier to line up a flat one, of course, but there are ways around that with the airfoiled stab.

    You really can't make the stab too rigid or too strong. I have had more issue with outright failures in the stab than anywhere. I have folded two stabs over the years, one thick airfoiled stab covered with Monokote, and the other a solid balsa "wedgie" style also covered with Monokote. On the second airplane, I got the airplane down in one peice, and rebuilt the stab as a 1/2" flat, built-up, with some of the first graphite I had ever seen. It was pretty darn stiff, and not inordinately heavy. I flew it the very next weekend, and it was a revelation in how much more consistent it was. Then, after about 10 flights, the pushrod fell off right after the 4-leaf, and went straight into the ground on the upwind side of the circle. Some guy was standing there watching, he was really impressed. Ted introduced himself and then...

    After that. the light bulb went on, and I built the next airplane with a solid balsa 1/2" airfoiled stab. It wasn't that punk wood, it was 7-lb C-grain. It almost made me sick how much it weighed, and how much nose weight I had to put in. But that airplane was dead-nuts consistent, for years. No matter what, it just worked the same every single time.

   Ever since then I have taken great effort to make sure the stab (and the rest of the airplane) was super-rigid. I think the best compromise between rigidity, aerodynamics, and weight using traditional materials is a sheeted foam airfoiled stab, about 1/2 or 5/8 thick, with medium (8 lb ) 1/32 sheeting, and double or triple covered. The last airplane stab was double-covered with .2 oz graphite, which made the pinholes MUCH WORSE on the stab than the rest of the airplane. The current airplane is double-covered with OO silkspan and copius amounts of nitrate, so far so good on the finish. The covering helps to an amazing degree, probably reduces the deflection per unit torque by a factor of 2. And, if I had been thinking, I would have put the graphite mat *in between* the foam and balsa, while I was sheeting it.


     The next step will be to move to graphite/epoxy, either vacuum-bagged to foam, or over balsa/foam.

     Point being, the most important thing I ever learned about stunt performance was to spend 3-4 oz of total weight to get more rigidity. The 4 oz is nothing as far as wing loading or power loading goes, but, if you are smart about it, can double or triple the rigidity of the stab and aft fuse, and make the airplane FAR more consistent - which directly translates to less wasted practice time and higher scores.

   Brett
« Last Edit: May 16, 2006, 11:12:17 AM by Brett Buck »

Offline Terry Fancher

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Re: Stabs and the "AVANTI" for Ted.
« Reply #40 on: May 16, 2006, 09:35:54 AM »
Egad, I'm another Avanti owner enlightened "too late"!!! ;D

I have an Avanti 50 (approx 600 sq) completed and an Avanti 60 under construction.  So, if nothing else, I'll be able to contribute some empirical flight observations as trimming progresses.  So far, the model has only one flight, which demonstrated that it was grossly tail heavy but still had excellent pitch stability in level flight.  It was stuntable but with the tail heavy condition pitch rates were excessive and I discontinued the maneuvers because I was afraid the explosive corners might stress the wings too hard or lead to it getting away from me (PIO) in the square 8.  Nose weight has been added and the model awaits more favorable wind conditions for more flights.  This Avanti 50 example uses flat stab/elevator, in 3/8th and 1/4 thicknesses respectively.
  The original Baron Avanti plans show the dramatic disparity in stab/ele thickness, using a wedge shaped stab to 1/2" and a 1/4" elevator.  The newer Avanti 60 plans show a much different contouring of the stab, sort of an airfoil, albeit with the high point set back a bit far, still 1/2" at max, but reducing in thickness so that they blend into the 1/4" thickness of the elevators without a dropoff.  Dixon had those plans drafted off a set of Baron hand drawn plans, I don't know if Baron had changed the stab contour or if Dixon, or the person who drafted the CAD version of the plan, made it.  Some of this discussion is germaine to my current project, as I was planning to to a slab 1/2" stab and 1/4" elevators, although I was already debating using 3/8th for the elevators.
  The Yatsenko planes seem to feature the highly insensitive at neutral/exponential "boost" as the controls are moved.  When Derek Barry flew Orestes Shark last spring he commented on the pronounced feel to the controls-totally dead at neutral and then coming on in a hurry as you yanked on the handle.  Obviously, it was not a "totally dead, then too abrupt" feel, but something in that neighboorhood.
  At any rate, time will tell with my own Avanti programme.  I'll post any flight info s it comes available....

Steve

Steve,

I look forward to your further experiences. 

I want to restate that Bob flew his Avanti extremely well and I expect it is possible (perhaps likely) that had I been able to retrim it to suit my preferred response rates I might have had an entirely different view of the ship.  In that particular case I think it would have been necessary to significantly change the onboard control geometry because the handle already had very wide line spacing yet the response rate was inordinately slow.

In that respect I'd be interested in knowing what the control geometry on your ship is.  Are the controls very, very slow?  It sounds unlikely based on your description of your first flight but, if the ship was really tail heavy that might have masked the situation.  Also curious to know where (at the half span) the ship balanced then and to where you will be moving the CG to correct the situation.

Ted

Offline Steve Fitton

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Re: Stabs and the "AVANTI" for Ted.
« Reply #41 on: May 17, 2006, 12:28:42 PM »
I had inquired of Ted on the details of the CG measurement, to make sure I did this seemingly simple procedure the same way he would, to ensure that my measurements provided good data.

It seems like an elementary thing, but Ted's thorough reply makes it certain that anyone following this discussion can measure their airplane and give data in the same "language"  Thanks to Ted for explaining this.  I must confess that I normally balance the airplane (when new) by picking it up and balancing it on the fingertips at the root, at the high point of the wing.  If neither the nose or tail violently swing down, I fly the model and then adjust balance till I like the feel.  While that might work after a fashion, the technique does not lend itself to accurate discussion over the internet.  So, at any rate, here are Ted's comments from the CG message:

"Hi Steve,

This is just a simple way of determining the location of the CG in respect to what we call the Mean Aerodynamic Chord, a universal aerodynamic practice.  Technically, the MAC is the spanwise point on each wing half (left and right sides) where half the area is inboard and half outboard.  Obviously, this isn't half way out the span but for simple tapered wings like ours it is close enough for a w.a.g. 

The MAC can be considered to "be" the wing for measurements and calculations regarding the lift produced.  As a result, the location of the CG relative to that point has a large effect on any aspect of pitch (up or down) control of the airplane.

To find the CG at the approximate MAC simply measure from the center of the fuse to each wingtip and divide each number by two.  Thus an equal span 60 incher will have the appx MAC 15" from either its wingtip or the center of the fuse.

For a rough location of the CG simply place an index finger under the wing at that location and move them back or foreward until the ship balances.  Make sure your fingers are in the same location on each wing.

Make a mark at the point it balances (I put a piece of masking tape along the chord at the half span so I can do so without hurting the finish).

Now measure the distance from the leading edge to the trailing edge (will be somewhere around 10 or 11 inches on most stunters).  This is the length of the wing chord at the MAC.  Let's say it's 11 inches on your ship.  (To answer the question I'm sure you want to ask; yes, that includes the flap.  The flap is part of the wing, it only happens to be moveable.  But that's a different issue...just include it)

Next measure the distance from the leading edge to the point the ship balanced (marked on the tape).  Based on your description, let's guess that this point is three and a half inches behind the leading edge.

Lastly, divide the second number (three and a half in this example) by the first number (eleven) and the result is 0.318 or 31.8%.  This means your CG is at 31.8% of the MAC.  Say it that way and you're talking like an aero engineer!

Any number bigger than around 25% is likely to result in a ship which responds as you suggest, too quick to fly precisely and may well not glide real well, wanting to balloon going into the wind and be hard to control the touch down point as a result.

To find a very good starting place for the CG in % MAC, figure out the total area of the tail and divide that number by the area of the wing.  This will also result in a % result.  If the tail is around150 square inches and the wing is 700 square inches the tail percentage is 150/700=0.214 (or 21.4%).

The number you get from that area calculation will define a fine starting place for your CG relative to the MAC.  On our example with the 11 inch chord we would be looking for a CG at 21.4% of eleven inches or 2.35 inches aft of the leading edge.

Make sense?

Hope this helps.

Ted"
Steve

Offline Steve Fitton

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Re: Stabs and the "AVANTI" for Ted.
« Reply #42 on: May 17, 2006, 10:34:29 PM »
Some measurements from the Avanti 50:

I actually determined the CG first with the noseweight installed, as I had added this after its first flight.  The CG was 2.5" back from the LE at the MAC.  (And the length of the chord at mid span was 11" and 11.125" (unequal span) respectively (how did you know it would be that??!)  This worked out to about 23% of MAC.  With the weight removed, so as to be in the condition of its first flight, the CG barely moved ;*maybe* 2 tenths of an inch-a distance that fingertips become hard to be accurate with.  If we say 2 tenths, that means the first flight CG was 25% of MAC, not outside the realm of good numbers.  Tail area on this model is about 146 square inches and wing is 600 square inches, so that gives it a 24 % tail percentage.

The nose "weight" installed after the first flight was actually nothing more than a heavier spinner/prop.  I need to take them back off and get a weight just to see how much difference there is.  More useful is probably for me to take the MAC CG measurements of my Time Machine 60 I usually fly, and see just what the CG is on a model I'm confortable with.  It may be I fly much more nose-heavy than I think....

Control ratios and handle play a role in the Avanti as well.  My model has the standard 1" horns with a 1:1 ratio flap/elevator, and 4.1" handle spacing.  Next Avanti test flight will have the spacing reduced to about 3.75, the setting I use on my Time machine.

Mostly though, I need the wind to stop so I can fly the Avanti more and get more stick time to watch exactly what its doing.....

Steve
Steve

Offline Ted Fancher

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Re: Stabs and the "AVANTI" for Ted.
« Reply #43 on: May 18, 2006, 06:34:07 PM »
STeve,

Based on those numbers it sounds like you are going in the right direction by reducing the handle line spacing.  Its' probably too late for you to check but it would be of interest to know what the actual arm lengths on the horns and b/c are as well (is it a four inch b/c, by the way?)

With the CG at that very reasonably good location for first flights the ship should be very flyable once you get the control response more to your liking.

Because the CG location method I described is a ball park figure, it is entirely possible that ultimate pitch trim will vary a small amount from that so don't be afraid to make changes to suit.  I still suggest reducing handle throw as the primary means to achieve that however.

A good test of the appropriateness of the CG is to evaluate how the ship glides after the engine quits.  A ship that is tail heavy will have a tendency to get light on the lines and may actually pitch nose up a little when the engine quits.  It will be uncomfortable in the glide coming into any significant wind and may be hard to get down where you want.

One that is nose heavy will glide easily and can generally be whipped all day to touchdown wherever you want it to.  My preference is for a ship that is just enough heavier in the nose to eliminate the floatiness in the glide.

Ted

Offline Steve Fitton

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Re: Stabs and the "AVANTI" for Ted.
« Reply #44 on: May 24, 2006, 09:27:05 AM »
For reference purposes I measured my 650" Time Machine 60 for CG, and found, in the configuration I currently fly it in, that it balances at 19.2% of MAC. 



Steve
Steve

Offline Steve Fitton

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Re: Stabs and the "AVANTI" for Ted.
« Reply #45 on: June 12, 2006, 07:28:07 PM »
I flew the Avanti some more yesterday.  With the heavier spinner and prop, it was stuntable, albeit it it was still acting tail heavy in the glide.  At shutoff, it would not immediately react in pitch either direction, but airspeed seemed to diminish rapidly and a slow uncommanded pitchup would occur, requiring constant down stick and making touchdowns on a point, and wheel landings, rather difficult.  Powered flight characteristics were good.  It was VERY stable in level flight, more stable in fact than my TM 60.  Control pressures were in the fingertip range but it was easy to fly good rounds and square corners were crisp with good "locking" in the flats of the squares.  I had reduced handle spacing to the minimum on the 85mm Kaz handle, but the airplane gives the impression that if you were too abrupt on a pull you could broach it sideways in the blink of an eye even with the narrow line spacing-but that was just an impression, and the plane was easy and intuitive to fly to the extent that the 3rd and 4th flights were full patterns with no issues with getting into a PIO or overturning and departing the plane.
  The "heavy prop" idea was a flop otherwise though, as the prop of choice (APC 11.75x3.75) turning 10250 rpm gave an annoying amount of out/in yaw in inside/outside squares.  I'll ditch that and try a Bolly 11x4 three blade next, with fixed weight in the nose.
  Overall impression is that it is just another good plane, with no odd handling characteristics I can discern that might relate to the configuration.  With its small size and motor though, it feels a bit "toylike" compared to the larger planes I seem to prefer.  Bill, you were right, I should have put an ST-51 or PA in the nose, as while the LA-46 is adequate power, having more power (and an ounce or two of engine weight eliminating the need for nose weight) would have probably reduced the toylike impression I get from the plane.  I do feel good about pressing on with the 60 size version, as I feel it should outfly my TM 60.

Steve
Steve

Offline Bill Little

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Re: Stabs and the "AVANTI" for Ted.
« Reply #46 on: June 12, 2006, 10:00:46 PM »
Hey Steve,

Even a Blind Big Bear grubs up an acorn every now and then...............

 ;D ;D
Big Bear <><

Aberdeen, NC

James Hylton Motorsports/NASCAR/ARCA

AMA 95351 (got one of my old numbers back! ;D )

Trying to get by

Offline Terry Fancher

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Re: Stabs and the "AVANTI" for Ted.
« Reply #47 on: June 13, 2006, 12:59:24 PM »
I flew the Avanti some more yesterday.  With the heavier spinner and prop, it was stuntable, albeit it it was still acting tail heavy in the glide.  At shutoff, it would not immediately react in pitch either direction, but airspeed seemed to diminish rapidly and a slow uncommanded pitchup would occur, requiring constant down stick and making touchdowns on a point, and wheel landings, rather difficult.  Powered flight characteristics were good.  It was VERY stable in level flight, more stable in fact than my TM 60.  Control pressures were in the fingertip range but it was easy to fly good rounds and square corners were crisp with good "locking" in the flats of the squares.  I had reduced handle spacing to the minimum on the 85mm Kaz handle, but the airplane gives the impression that if you were too abrupt on a pull you could broach it sideways in the blink of an eye even with the narrow line spacing-but that was just an impression, and the plane was easy and intuitive to fly to the extent that the 3rd and 4th flights were full patterns with no issues with getting into a PIO or overturning and departing the plane.
  The "heavy prop" idea was a flop otherwise though, as the prop of choice (APC 11.75x3.75) turning 10250 rpm gave an annoying amount of out/in yaw in inside/outside squares.  I'll ditch that and try a Bolly 11x4 three blade next, with fixed weight in the nose.
  Overall impression is that it is just another good plane, with no odd handling characteristics I can discern that might relate to the configuration.  With its small size and motor though, it feels a bit "toylike" compared to the larger planes I seem to prefer.  Bill, you were right, I should have put an ST-51 or PA in the nose, as while the LA-46 is adequate power, having more power (and an ounce or two of engine weight eliminating the need for nose weight) would have probably reduced the toylike impression I get from the plane.  I do feel good about pressing on with the 60 size version, as I feel it should outfly my TM 60.

Steve

Steve,

Enjoyed our chat last night.  Thanks for the call.

You've probably expressed the glide effects of tail heaviness better than I have.  I've called it a pitch up but your description is a better statement of what the flyer feels.  In good air you can get away with it but, as we've all seen, when such an airplane comes around into a significant wind it can become nearly impossible to get on the ground in decent fashion and, if severe, can even be damaged by the balloon, float and flop that can result.

Re the prop thing.  How much difference in weight will there be between the APC and the three blade Bolly?  Worth considering as well is the fact that the APC, while heavy overall, concentrates the majority of its mass in the hub and the tips themselves (which by definition have the greatest gyroscopic effect) amount to almost nothing weightwise.

I'll be very interested to hear if the yaws you describe go away with the prop change or if you might eventually determine that other yaw inducing forces are responsible (engine/rudder offsets, leadout position, tip weight, etc.)

Ted

Offline Steve Fitton

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Re: Stabs and the "AVANTI" for Ted.
« Reply #48 on: June 13, 2006, 11:03:45 PM »
The APC 11.75x3.75 weighs 1.50 oz on my scale, and the Bolly 11x4 three blade weighs 0.95 oz.  I won't get a chance to fly the Avanti this weekend, but when it does take to the air again I'll report if the different prop combination helps with the yaw or not.....


Steve
Steve

Offline RandySmith

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Re: Stabs and the "AVANTI" for Ted.
« Reply #49 on: June 18, 2006, 01:24:34 PM »
The APC 11.75x3.75 weighs 1.50 oz on my scale, and the Bolly 11x4 three blade weighs 0.95 oz.  I won't get a chance to fly the Avanti this weekend, but when it does take to the air again I'll report if the different prop combination helps with the yaw or not.....


Steve

Hi Steve

You will find  even if the BOLLY was  as heavy  or  a bit heavier  that it would have  LESS  GP, the 3 blades on my planes seem to always  have  less  GP  than the equivalent  2 blades, and  the APC and other plastic props seem to alway have more.
The 11 x4 N  that you have  is very light at the tips  too. for the  46 OS  you may want to pitch the blades  up slightly

Regards
Randy


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