News:
2018----><---- T Shirt




  • October 20, 2018, 12:15:38 PM

Login with username, password and session length

Author Topic: Elevator width  (Read 1856 times)

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 468
Elevator width
« on: October 08, 2018, 06:21:59 AM »
Hello,
There exists a general consensus among the best pilots regarding the flaps width in the competition stunt planes - narrower flaps are preferred. 
 
I wonder if the same pertains to the elevator width?

In my understanding, the elevator also cannot be too wide. I have inconclusively searched the entire forum for the conclusion regarding this particular issue and would like to start the discussion of this topic.

Thank you,
M




Online Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 10470
Re: Elevator width
« Reply #1 on: October 08, 2018, 08:42:19 AM »
First, note that while much of what I say here is conditioned by my own theoretical understanding and relatively meager experience flying, it's all been hashed out here before, by national and world champions.  There's no need to start a discussion -- just refine your search skills, and you can tippy-type your way through over a decade of received knowledge on this subject.  There's always a question about who to believe in such cases -- I look in the archives of the US Nationals and the FAI Worlds, and go by the people who've placed well there.  For this group (and please double-check me on this!) that'll be Paul Walker, Ted Fancher, Brett Buck, Igor Burger, and a few others who post less often.  (And note: I haven't even GONE to the Nationals, and based on how I stack up against local competitors who do go, I wouldn't make it into the top twenty -- so if one of Those Guys says I'm wrong, I'm probably wrong.)

Typical flapped stunters have an elevator area that's about 40-50% of the total horizontal area.  They seem to work pretty well.  It's probably more important to get the total horizontal area (or the tail volume coefficient) right.  I'm pretty sure that tail aspect ratio has a bearing on that, too, but that gets into things that I understand that I should understand, but don't actually understand -- if you understand what I mean.

Based on the excellent flight performance of the Skyray, and the pretty good flight performance of the 40-sized knockoffs that I've built, a flapless stunter seems to want to have an elevator area about 25-30% of the total horizontal area.  More just makes the elevator too sensitive, and gets you a plane that'll tend to run into the Netzband Wall (look it up).

Flapped stunters need more area because in the typical flapped stunter configuration, the flap contributes elevator action opposite to the lift it provides, which requires more elevator to compensate.

In my humble opinion, once you get the stab & elevator size in the ballpark it's far more important that you provision your airplane with the ability to change the flap/elevator ratio, because that ratio is something that you want to trim depending on the airplane weight and CG location.  You may get it set up in the initial trim sessions and never touch it again for the life of the plane -- but you want it adjustable for those first trim sessions.

In my humble opinion, that pretty much sums it up.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 468
Re: Elevator width
« Reply #2 on: October 08, 2018, 02:54:33 PM »
Please see the attached.
There is a mistake on one of these sheets. Please compare the root chord width of the elevator (red ellipses)
I have contacted Igor with question - no answer yet.

In the meantime and following my general approach to the issues I do not understand, I am searching for opinions and suggestions.

Hi Ty,
Sounds right to me. Longer nose and longer tail (like Max Bee) mean larger pitch inertia w/r to the model CG comparing to the models with short fuselage. Larger pitch inertia means larger moment to overcome it in corners. Larger moment (w/r to the model CG.) means larger force on the elevator is needed. Larger force on the elevator means larger elevator. This of course assumes that the time to make corner is constant.

Hi Tim,
You are most likely right that the issue was discussed before among top fliers but was it properly documented on the Forum?
I will keep searching....

Regards and Happy Flying,
M


Online Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 10470
Re: Elevator width
« Reply #3 on: October 08, 2018, 03:28:27 PM »
Try searching on elevator chord rather than elevator width.

Igor's Max Bee should operate on different rules, because of his "logarithmic" flap mechanism -- at high elevator deflection the flaps move more slowly, so you need less elevator to rotate the ship than you would if you had a more typical setup.  That would allow for a smaller ratio of elevator area to total.

If I were building that thing, I'd just go by the view that shows the whole elevator.  It's very likely the other view is intended to be illustrative only, not to be a guide for building.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Massimo Rimoldi

  • Trade Count: (0)
  • Lieutenant
  • ***
  • Posts: 78
Re: Elevator width
« Reply #4 on: October 09, 2018, 03:08:27 AM »

 Longer nose and longer tail (like Max Bee) mean larger pitch inertia w/r to the model CG comparing to the models with short fuselage. Larger pitch inertia means larger moment to overcome it in corners. Larger moment (w/r to the model CG.) means larger force on the elevator is needed. Larger force on the elevator means larger elevator. This of course assumes that the time to make corner is constant.



Hi Matt.
Personally I do not think the problem is that simple.
Our tail plane (stab + elev) produces lift that multiplied by the lever arm (distance from the CG) generates the moment that allows the variation of attitude.
+ lever arm = + stability, + moment around CG with the other variables being equal.
So, if you increase the lever arm you do not have to increase the force on the elevator to increase the moment produced by the two, you already did.
So, as usual, everything takes us back to struggle with the compromise that practically governs the good flight of our beloved models.

Massimo

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 468
Re: Elevator width
« Reply #5 on: October 09, 2018, 05:32:42 AM »
Hi Massimo,
When the elevator is deflected up, the moment w/r to the CG produced by the horizontal stabilizer at a momentary AOA has the sign opposite to the moment w/r to CG produced by the deflected elevator. Because the sum of these moments causes the nose of the plane to go up, the moment from the elevator must be larger than the moment from the stabilizer.

At this moment, I simply want to know what is the correct width of the Max Bee elevator.

I have already built one and it has the contour shown on sheet 2 like suggested by Tim.

Comment: The C/L aerodynamics is very complex and this what we know for sure represents a tip of the huge iceberg of the unknown waiting to be discovered, described and at least partially quantified. I may actually build several Max Bee elevators having different root and tip chords width to test in the air.

Regards,
M

Online Massimo Rimoldi

  • Trade Count: (0)
  • Lieutenant
  • ***
  • Posts: 78
Re: Elevator width
« Reply #6 on: October 09, 2018, 05:59:55 AM »
Hi Matt.
If I understand correctly you consider the work of stab and elev independent of one another.
In fact, the rudder horizontal tail should be considered as a wing, when you speak of the wing you consider ONLY the generated lift.
In this case the elev is an integral part of the "wing" and (like the flaps) is used for:
- change the airfoil
- change the incidence of the "wing"

Regarding your research, I have recently used the Igor's elevators (Fiberglass), at the moment I do not have the exact measurements available but as soon as possible I will let you have them.

Massimo
« Last Edit: October 09, 2018, 09:20:08 AM by Massimo Rimoldi »

Offline Vitalis Pilkionis

  • Trade Count: (0)
  • Lieutenant
  • ***
  • Posts: 87
Re: Elevator width
« Reply #7 on: October 09, 2018, 07:51:30 AM »
Hi Matt,

I noticed the same discrepancies in those drawings, so I asked Igor what is the correct size of the elevator and his answer was 75/55 (root/tip).

Regards,
Vitalis

Online Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 9047
Re: Elevator width
« Reply #8 on: October 09, 2018, 10:59:13 AM »
You are most likely right that the issue was discussed before among top fliers but was it properly documented on the Forum?

      Well, it's probably not in the form of a formal lecture directed at your specific issue, but that's not the definition of "proper".

    And again, I fear you are getting bogged down in trivia and minutiae without attempting to master the basics. Very successful airplanes have been built with stab/elevator splits of anywhere from 40:60 to 75:25. Generally, the right answer for relatively conventional flapped stunt plane dimensions is probably somewhere around 60:40, but that includes a lot of other assumptions and you can probably make anything from 50:50 to 75:25 work if you are willing to fiddle with the control ratios.

      Ty's observations is quite on point, the longer the tail moment, the more "angle" you need in the tail to avoid rate-limiting. It has to do with the partial derivative of the torque VS the pitch rate. Howard and I discussed this very briefly at the last contest, about how you can make the tail too long. The Skyray exhibits this in droves, the turn is limited entirely by the fact that it can't pitch around fast enough, particularly when it's built up from balsa and has a good engine (removing stalling at a cause). That's why mine has an experimental wider elevator, and all the travel I can get. The Ringmaster is the opposite case, which is why you have to slow the elevator travel rate down so you only move it +-1/2" or so. Make the elevator narrower and that would go away, and you could move it further. It wouldn't fly any better, just make the comically long elevator horn less comical.

     Brett



Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 468
Re: Elevator width
« Reply #9 on: October 09, 2018, 04:29:33 PM »
Hi Vitalis,
Thank you for confirming the dimensions.
Loren Nell (NZ), who built many Max Bees, responded with 74mm at the elevator root and 55mm at the tip.

Hi Massimo,
I treat the elevator and the horizontal stabilizer as the tail wing with adjustable airfoil geometry.
Please measure the Igor's fiberglass elevator and confirm the dimensions given by Vitalis and Loren Nell.

Thanks and Happy Flying,
M



Online Crist Rigotti

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 3091
  • Electric - The future of Old Time Stunt
Re: Elevator width
« Reply #10 on: October 09, 2018, 05:25:44 PM »
I would think to determine the elevator chord you first need the stab & elevator total area and aspect ratio.  That will give the total chord, then use a split as Brett mentioned above.  Then deal with the LE/TE tapers.
Crist
AMA 482497
Waxahachie, TX
Electric - The Future of Old Time Stunt

Online Massimo Rimoldi

  • Trade Count: (0)
  • Lieutenant
  • ***
  • Posts: 78
Re: Elevator width
« Reply #11 on: October 10, 2018, 06:22:54 AM »
Hi matt.
I checked my elev, the measurements are the same as those provided by Vitalis and Loren: mm 75/55 (root/tip).

Regards, Massimo

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 468
Re: Elevator width
« Reply #12 on: October 10, 2018, 07:59:43 AM »
Hi Massimo,
Thank you. The issue of the Max Bee elevator size is closed.

Hi Crist,
I will use the method described by you for several designs of modern stunt planes.
If I find something interesting, I will publish the results on this Forum.

Happy Flying,
M

Offline Steve Helmick

  • AMA Member and supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 8313
Re: Elevator width
« Reply #13 on: October 10, 2018, 01:00:11 PM »
As Massimo wrote, Matt should be thinking of the stabilizer and elevator as a unit, with variable airfoil, as is the wing. The Free Flight guys that experimented with undercambered airfoils came to the conclusion that the most lift and least drag was created by moving the undercamber aft. Some HLG fliers just added a triangular "kicker" to the bottom of the TE that was less than 5% of the chord, while F1A airfoils were developed (before zoom launch and bunting transition) with the UC flatter in front and more droop aft.

That suggests to me that we might be better off with smaller elevator chords...which would also result in larger stabilizer chords, naturally improving the strength and stiffness. We should not under-appreciate the value of stiff fuselage and surfaces. With removable flaps and elevators, it would be an interesting experiment to make both with various chords and swapping them around.

What puzzles me most about Igor's drawing is the elevator being thinner than the stabilizer. We know that this reduces response around neutral...which is also what his logarithmic gizmo does. Hmmmm.  D>K Steve
« Last Edit: October 10, 2018, 01:50:51 PM by Steve Helmick »
In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.

In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

"Be polite, be professional, but have a plan to kill everybody you meet." General Mattis.

Online Brent Williams

  • 2018 Supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 635
  • Making America Fly Stunt Again!
    • Fancher Handles - Presented by Brent Williams
Re: Elevator width
« Reply #14 on: October 10, 2018, 01:09:13 PM »
If anyone is curious what this change to the elevator chord looks like on the MaxBee plan, here's a quick drawing showing the difference.
Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
https://stunthanger.com/smf/brent-williams'-fancher-handles-and-cl-parts/ted-fancher's-precision-pro-handle-kit-by-brent-williams-information/

Offline Ken Culbertson

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 692
Re: Elevator width
« Reply #15 on: October 10, 2018, 01:11:37 PM »
With removable flaps and elevators, it would be an interesting experiment to make both with various chords and swapping them around.  D>K Steve
Doing just that with Pocketed Robarts on next years PA right now.  I am convinced that an airfoiled high aspect stab with about 40% elevator will produce smoother tighter corners but I don't want to be digging out hinges if I am wrong!

Ken
AMA 15382

If it is not broke, don't fix it.

Offline Vitalis Pilkionis

  • Trade Count: (0)
  • Lieutenant
  • ***
  • Posts: 87
Re: Elevator width
« Reply #16 on: October 10, 2018, 01:53:13 PM »
What puzzles me most about Igor's drawing is the elevator being thinner than the stabilizer. We know that this reduces response around neutral...which is also what his logarithmic gizmo does. Hmmmm.  D>K Steve

Igor's gizmo affects only flaps. Elevators operate as usual. I may be wrong, but I think his approach on stabilizer+elevator design was just the same as on wing+flaps, which are designed to maintain the curve of a lift coeficient vs AoA linear without any bumps and with smooth transition at the top. But as we know stabilizer operates at negative AoA, therefore theoretically needs different approach on design, but somewhere Igor mentioned, that he just tried this combination and it worked well, so he left with it.

Vitalis

Online Brent Williams

  • 2018 Supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 635
  • Making America Fly Stunt Again!
    • Fancher Handles - Presented by Brent Williams
Re: Elevator width
« Reply #17 on: October 10, 2018, 02:48:57 PM »
Doing just that with Pocketed Robarts on next years PA right now.  I am convinced that an airfoiled high aspect stab with about 40% elevator will produce smoother tighter corners but I don't want to be digging out hinges if I am wrong!

Ken

Paul Walker, Brett Buck, Ted Fancher, David Fitzgerald would disagree with you on the high aspect ratio tail topic.  For the most part,  all of the so named members of this club of world/national champions advocate for a low aspect ratio tail.
Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
https://stunthanger.com/smf/brent-williams'-fancher-handles-and-cl-parts/ted-fancher's-precision-pro-handle-kit-by-brent-williams-information/

Online Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 10470
Re: Elevator width
« Reply #18 on: October 10, 2018, 03:42:09 PM »
Doing just that with Pocketed Robarts on next years PA right now.  I am convinced that an airfoiled high aspect stab with about 40% elevator will produce smoother tighter corners but I don't want to be digging out hinges if I am wrong!

Ken

Paul Walker, Brett Buck, Ted Fancher, David Fitzgerald would disagree with you on the high aspect ratio tail topic.  For the most part,  all of the so named members of this club of world/national champions advocate for a low aspect ratio tail.

Check out this here thread on horizontal tail aspect ratio. 
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Ken Culbertson

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 692
Re: Elevator width
« Reply #19 on: October 10, 2018, 04:26:16 PM »
Check out this here thread on horizontal tail aspect ratio.

Saw that post earlier.  Maybe we need to define "high" before going further.  My design has a 64" span, 675sq" wing with a 6 AR and the tail has a 25" span with a 5.5 AR .  I plan to bump it up to about the same as the wing by thinning the elevator.  These numbers are not "out of the box" high by today's standards.

Ken
AMA 15382

If it is not broke, don't fix it.

Online Brent Williams

  • 2018 Supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 635
  • Making America Fly Stunt Again!
    • Fancher Handles - Presented by Brent Williams
Re: Elevator width
« Reply #20 on: October 10, 2018, 05:06:04 PM »
Saw that post earlier.  Maybe we need to define "high" before going further.  My design has a 64" span, 675sq" wing with a 6 AR and the tail has a 25" span with a 5.5 AR .  I plan to bump it up to about the same as the wing by thinning the elevator.  These numbers are not "out of the box" high by today's standards.

Ken

You'll find that the tail assemblies on the afore mentioned crew of winners have aspect ratios that are 4:1 or less, with most hovering closer to the neighborhood of 3.5:1 (ish) and around 25% of the wing area.  Generally, the split is around 60/40 or 65/35.

See the percentage of Walker Cup wins from the Impact(bad news, impact, for reals, predator), ThunderGazer/Stargazer, Trivial Pursuit, and the Infinity.  The West Coast engineers cabal has been mighty successful in nearly 30 years of competition practice using the low aspect ratio tail.  Feel free to chart your own path.  There are other successful camps of design, ie Igor, Randy Smith, Bob Hunt and Bill Werewage.
Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
https://stunthanger.com/smf/brent-williams'-fancher-handles-and-cl-parts/ted-fancher's-precision-pro-handle-kit-by-brent-williams-information/

Online Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 10470
Re: Elevator width
« Reply #21 on: October 10, 2018, 05:37:10 PM »
You'll find that the tail assemblies on the afore mentioned crew of winners have aspect ratios that are 4:1 or less, with most hovering closer to the neighborhood of 3.5:1 (ish) and around 25% of the wing area.  Generally, the split is around 60/40 or 65/35.

See the percentage of Walker Cup wins from the Impact(bad news, impact, for reals, predator), ThunderGazer/Stargazer, Trivial Pursuit, and the Infinity.  The West Coast engineers cabal has been mighty successful in nearly 30 years of competition practice using the low aspect ratio tail.  Feel free to chart your own path.  There are other successful camps of design, ie Igor, Randy Smith, Bob Hunt and Bill Werewage.

Oh, Brent Brent Brent Brent Brent.  So discouraging.

Ken -- go right ahead and design it your way.  Particularly if I'm going to be there flying a Walker-ish design with a stubby tail (heh heh).
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Larry Fernandez

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1069
Re: Elevator width
« Reply #22 on: October 10, 2018, 06:07:55 PM »
Doing just that with Pocketed Robarts on next years PA right now.  I am convinced that an airfoiled high aspect stab with about 40% elevator will produce smoother tighter corners but I don't want to be digging out hinges if I am wrong!

Ken

Make the elevators removable and build two or three sets with different cord widths.
They can be changed at the flying field in just a few minutes. And donít forget to seal the hing lines.

Larry, Buttafucco Stunt Team

Offline Ken Culbertson

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 692
Re: Elevator width
« Reply #23 on: October 10, 2018, 06:32:18 PM »
Oh, Brent Brent Brent Brent Brent.  So discouraging.

Ken -- go right ahead and design it your way.  Particularly if I'm going to be there flying a Walker-ish design with a stubby tail (heh heh).

Once upon a time we were discussing removable surfaces so we could experiment with flap and elevator sizes.  Somehow this turned into a theoretical discussion of aspect ratio's.  IMHO it is more an issue of style and size.  I like a big elevator/stab.  I have never paid much attention to the aspect ratio other than to notice that the planes I have flown with a higher ratio seem to exit corners better.  I have enough to worry about switching to electric so I will revisit aspect ratio's next season as soon as I post a score that makes me think  that I have out flown my current design.  I still think the Argus is the most beautiful stunt ship ever.

Ken 
AMA 15382

If it is not broke, don't fix it.

Online Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 9047
Re: Elevator width
« Reply #24 on: October 10, 2018, 06:43:46 PM »
Hi Matt.
If I understand correctly you consider the work of stab and elev independent of one another.
In fact, the rudder horizontal tail should be considered as a wing, when you speak of the wing you consider ONLY the generated lift.
In this case the elev is an integral part of the "wing" and (like the flaps) is used for:
- change the airfoil
- change the incidence of the "wing"

    Which is a much more clearly-worded description than those above. For at least some relevant example cases, you get the largest increment in the section Cl with a 40% elevator (60% stab). You get the most AoA change for a given deflection angle with a flying stabilizer (with has a ratio of 0:100 - the whole thing moves).

     The AoA change with respect to the wing is what determines the partial of lift WRT pitch rate, so there is some compromise that changes depending on the tail moment - the shorter the tail, the less sensitive the tail lift is to the pitch rate. That *why* a Flite Streak only needs a 75:25 stab/elevator, it never gets near rate limiting, and why a Ringmaster can only handle so much elevator travel, because even small deflections put it WAY over the tolerable maximum pitch rate for the rest of the airplane.

      Howard's question from the other day ("if the tail moment is too long, what problem does it cause") very quickly led us to think that there is no real limit from the standpoint of control, as long as you used a stabilator/flying stab. Of course there are many other good reasons - structural and weight/balance - that drive the tail moment to something relatively small, and you actually want the partial of lift to pitch rate to tail off in the range of normal flying, so you can get it more sensitive around neutral without going crazy at larger deflections.

    Brett

Offline Serge_Krauss

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1140
Re: Elevator width
« Reply #25 on: October 10, 2018, 07:43:30 PM »
     
 Ty's observations is quite on point, the longer the tail moment, the more "angle" you need in the tail to avoid rate-limiting. It has to do with the partial derivative of the torque VS the pitch rate. Howard and I discussed this very briefly at the last contest, about how you can make the tail too long. The Skyray exhibits this in droves, the turn is limited entirely by the fact that it can't pitch around fast enough, particularly when it's built up from balsa and has a good engine (removing stalling at a cause). That's why mine has an experimental wider elevator, and all the travel I can get. The Ringmaster is the opposite case, which is why you have to slow the elevator travel rate down so you only move it +-1/2" or so. Make the elevator narrower and that would go away, and you could move it further. It wouldn't fly any better, just make the comically long elevator horn less comical.

Brett

I'm not sure what all goes into the derivatives that determine turn limiting. I think though that in a simple static analysis, it is relevant that for a given positive wing angle of attack, the longer the tail arm, the more positive the stabilizer's angle of attack. That in itself limits pitching moment. I don't know whether this is part of the math mentioned, and since my hard drive is dead, I don't have the diagram I drew to illustrate this. For short, it's just a diagram using what Frank Zaic translated as "circular airflow."- SK

Online MikeyPratt

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 484
Re: Elevator width
« Reply #26 on: October 11, 2018, 11:07:33 AM »
Based on the excellent flight performance of the Skyray, and the pretty good flight performance of the 40-sized knockoffs that I've built, a flapless stunter seems to want to have an elevator area about 25-30% of the total horizontal area.

Hi Tim,
I agree with that, but there are a number things that contribute to that such as TVC.  I've found that the same 60/40 split between the stab & elevator of the flapless worked really well and can be adjusted up or down to get the corner your looking for.  Many of the older models fly great when the controls are slowed down (i.e. Ringmaster & Flitestreak etc.).

My latest design the P-Force XL has the 60/40 split, I've changed 50/50, 55/45, 70/30 all flew well but the 60/40 was the best in terms of corner and groove.  Super easy to fly with a great corner giving the feeling that it goes right where you point it.

For Kens MaxBee, I would build it as drawn because of the flap gizmo and make another set of larger elevators to try out once you have flown & trimmed out, that way you can quantify the size of the elevator that suits your feel.
Remember Igor did win the worlds with it so it has to be pretty good already.

Later,
Mikey

Online Dane Martin

  • 2017
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2253
  • heli pilot BHOR
Re: Elevator width
« Reply #27 on: October 11, 2018, 11:38:13 AM »
I think this is a related question..... if not I'll research it. No need to repeat anything.

Since Mikey brought up flap less stunters, what is the general reason for flaps? I have a few planes now that are flapless and make extremely tight turns. I would assume the idea is not to make a turn tighter?

Online Dave_Trible

  • 2017
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4415
Re: Elevator width
« Reply #28 on: October 11, 2018, 12:19:34 PM »
Dane I think it's more about the 'style' of the turn.  While some flapless airplanes can certainly turn tightly, it is a more round turn where an airplane with flaps more looks to rotate on an axis in the vicinity of the flap line.  The affect is akin to 1. Suddenly adding wing area and 2. Shifting the wing angle of attack to a large positive number as if the wings were able to swivel at the root. This is very well seen if you could take slow motion video of the two styles during a square loop.  The stabilizer/tail of the flapless airplane seem to follow right along the flight path of the forward fuselage where the on the flapped airplane you get the sense the airplane is turning at an angle of attack a little greater than the radius.  When flaps get oversized or are set to too great a deflection the airplane can start looking strange in turns-as if it's folding in half at the middle and whipping the nose around from behind.  Something JUST short of that yields the "turn-lock" corner.  This isn't possible with any normal looking flapless airplane I've seen fly.

Dave
AMA 20934
FAA Certificate FA3ATY4T94

Online Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 10470
Re: Elevator width
« Reply #29 on: October 11, 2018, 12:26:10 PM »
I think this is a related question..... if not I'll research it. No need to repeat anything.

Since Mikey brought up flap less stunters, what is the general reason for flaps? I have a few planes now that are flapless and make extremely tight turns. I would assume the idea is not to make a turn tighter?

It's been discussed.  I'm pretty sure parts of it are in Paul Walker's trimming procedure, but I'm not going to go check right now.

One, you can fly a heavier plane and still get nice tight turns (this isn't in Paul's procedure).

Two, a flapless stunter has to have the wing pitched to get a turn.  That means that it's always a bit nose up in level, and it's visibly pitched in maneuvers.  Properly adjusted flaps make the plane fly through the maneuvers with the fuselage tangent to the path that it's taking through the air, rather than pitched up (or pitched down, if you overdo the flap action).  IMHO a flapped plane is way prettier in the air (Dave answered while I was typing -- what he said).
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Dane Martin

  • 2017
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2253
  • heli pilot BHOR
Re: Elevator width
« Reply #30 on: October 11, 2018, 12:28:40 PM »
Makes sense guys. Thank you.

Offline Ken Culbertson

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 692
Re: Elevator width
« Reply #31 on: October 11, 2018, 02:19:22 PM »
Makes sense guys. Thank you.
If you want to see what Dave is saying, here are links to a flapless and a modern full flap doing patterns.  Slow them down to .25 and watch the corners.  The 6th and 10th corners of the SQ8 and the triangles really illustrate what he is talking about.



AMA 15382

If it is not broke, don't fix it.

Offline phil c

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1884
Re: Elevator width
« Reply #32 on: October 11, 2018, 03:14:21 PM »
If you want to see what Dave is saying, here are links to a flapless and a modern full flap doing patterns.  Slow them down to .25 and watch the corners.  The 6th and 10th corners of the SQ8 and the triangles really illustrate what he is talking about.


The videos don't seem to show what Dave T is talking about.  The unflapped plane generally turned pretty soft corners.  The flapped plane turned sharper turns and looked under better control.  The result probably depends a lot on how the plane is trimmed but I suspect in the long run it is harder to get a consistent sharp corner with an unflapped plane.  Generally it has to be balanced further back to get quick response in sharp maneuvers which hinders making precise entrances and exits.
phil Cartier

Offline Ken Culbertson

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 692
Re: Elevator width
« Reply #33 on: October 11, 2018, 03:45:06 PM »
The videos don't seem to show what Dave T is talking about.  The unflapped plane generally turned pretty soft corners.  The flapped plane turned sharper turns and looked under better control.  The result probably depends a lot on how the plane is trimmed but I suspect in the long run it is harder to get a consistent sharp corner with an unflapped plane.  Generally it has to be balanced further back to get quick response in sharp maneuvers which hinders making precise entrances and exits.
Watch the nose when the corner starts.  On the unflapped plane will appear to be flying a tangent to the curve.  The flapped plane will appear to be rotating and sliding as it turns.

Ken
AMA 15382

If it is not broke, don't fix it.

Online MikeyPratt

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 484
Re: Elevator width
« Reply #34 on: October 11, 2018, 11:24:22 PM »
Hi Dave & Ken,
After switching to my computer and slowing it down as you suggested, I don't see that at all.  What I saw was a model that wasn't properly trimmed against a very well trimmed model and higher caliber pilot (not trying to run anyone down at all).  The Primary Force in the Video was somewhat nose heavy, you could tell by watching the inside or outside loops because they tended to open up.  Now if you would have shown Brett and his Skyray it would have been at better example. 

Flapped models do tend to look slightly slower in corners but not necessary tighter in my opinion.  I'm not anti flap at all but after watching modelers for years flying models that aren't properly trimmed.  Over the years there are some really good models that don't have flaps and even a National Champion (Bob Baron) flying a flapp-less design.  Yes he was very gifted pilot and worked really hard at it. 

I've built many flapped models and most of them flew just fine after lots of trimming.  What gave me a clue on all of this was Ted Fancher, I reduced the flap area on my next model and it turned more like Teds, Davids, Paul, Billy, and the French guy with really small flaps on his model.  So I designed a flap-less model for profile stunt that worked really well (and now the XL that works even better).  I'm not trying to change the minds of people and saying flapp-less is the way to go, not at all.  Flying models such as many of the older models has showed me that it can be done with great results.

Later,

Mikey

P. S.  After watching this Vedio again (Friday Morning) I think it may also be partl of a ďhandle biasĒ flying without the handle totally vertical for the loops to open up, this would also affect the entry and exit of the turns.   
« Last Edit: October 13, 2018, 08:22:21 AM by MikeyPratt »

Offline Ken Culbertson

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 692
Re: Elevator width
« Reply #35 on: October 12, 2018, 08:33:03 AM »
Hi Dave & Ken,
After switching to my computer and slowing it down as you suggested, I don't see that at all.  What I saw was a model that wasn't properly trimmed against a very well trimmed model and higher caliber pilot (not trying to run anyone down at all).  The Primary Force in the Video was somewhat nose heavy, you could tell by watching the inside or outside loops because they tended to open up.  Now if you would have shown Brett and his Skyray it would have been at better example. 

Flapped models do tend to look slightly slower in corners but not necessary tighter in my opinion.  I'm not anti flap at all but after watching modelers for years flying models that aren't properly trimmed.  Over the years there are some really good models that don't have flaps and even a National Champion (Bob Baron) flying a flapp-less design.  Yes he was very gifted pilot and worked really hard at it. 

I've built many flapped models and most of them flew just fine after lots of trimming.  What gave me a clue on all of this was Ted Fancher, I reduced the flap area on my next model and it turned more like Teds, Davids, Paul, Billy, and the French guy with really small flaps on his model.  So I designed a flap-less model for profile stunt that worked really well (and now the XL that works even better).  I'm not trying to change the minds of people and saying flapp-less is the way to go, not at all.  Flying models such as many of the older models has showed me that it can be done with great results.

Later,

Mikey
I was in a hurry and just grabbed the first flapless one I could find.  You are right, it does look nose heavy.  I didn't even look at the rounds since it was the behavior in the corners I was concerned with.  I have been sensitive to this issue since I first started flying squares back in the early 60's.  I learned on a "out of the box" Nobler and I never liked how it appeared to turn like you were holding the tail and pushing the nose up. So, not having a clue what I was doing, I designed my own plane with a longer tail, larger stab, smaller flaps and I flipped the holes on the flap horn to give me a 2/3 vs a 1/1 on the ratio.  It flew more like I wanted it to but at 16 I had no clue why, it just did.

So, what I am saying is that we all seem to see what we want to see and what bothers some is what the others are calling perfection so let's just agree to disagree on this one.

Ken

AMA 15382

If it is not broke, don't fix it.

Online Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 9047
Re: Elevator width
« Reply #36 on: October 12, 2018, 09:27:49 AM »

So, what I am saying is that we all seem to see what we want to see and what bothers some is what the others are calling perfection so let's just agree to disagree on this one.


    What you are seeing is at least partially an optical illusion, that would be illustrated if you had the position track (like the tracking camera data from the WC threads). The effect you are describing, in either case, is the discrepancy between the pitch attitude and the track. The "pitch around and slide" effect you note is a function of the angle of attack. The track is not right along the fuselage in either case, the difference is you can easily see it on my airplane (ex post facto) because of the nature of the design (and the way it is being flown). Mine turns pitches up abruptly right at the beginning and stays there, the flapless airplane swoops a bit so that you don't get a very sharp change from the nose to inside the track of the turn.   

   Also, the wing loading is probably a lot higher on my airplane. At the time of the video, the wing loading was about 13.55 ounces/square foot. Guessing at typical weights, the flapless airplane is probably more like 11 or possibly less. For a given turn radius, the flapless airplane has to have less coefficient of lift than mine. The difference is, to get that, it has to pitch the entire airplane around and hold the nose "inside" the turn by a corresponding amount. My flapped airplane has to do a bit of that, but it also gets some AoA from having a cambered airfoil with the flap deflected, so it's *probably* flying at a lower body angle of attack than the flapless airplane.

    Note that making the flaps proportionally larger would reduce the angle of attack even furthers, and the "narrow flap"/"wide flap" issue can have a marked effect on the way the airplane looks in the corners. In fact, as early as the late 50's, people had realized that the Nobler turn didn't ever look very tight, whether it was or not. The Shark 45 was originally unnamed and had the word "Humbler" typed on a piece of paper stuck in the canopy. It had much smaller (proportionally) flaps than the Nobler and was known for a sharper turn. Bob Gialdini even mentions that to "make your turn more snappy, like a Shark" trim a good fraction of the flaps off his erstwhile Nobler clone Olympic. Ted Fancher took the experiment to its logical conclusion by making his flaps *variable sized* and doing experiments.

   Of course, part of this is also piloting. I can't recall how hard I was trying to hit the corners in this video, compared to normal, but I absolutely, positively, guarantee that I was not attempting to achieve the full capability of the airplane. In the few cases we have good data for, I would guess it would turn maybe 1/3 to 1/2 the normal radius I am attempting to achieve. It can clearly turn much tighter (I have been flying essentially the same design for about 20 years, I have a *really good idea* what it can do and not do).  I have no idea how hard the flapless airplane was attempting to turn compared to it's capability. Somewhere this is a video of me flying the Skyray, that would be a better comparison. I am generally very close to maxed out on those flights.

     Note that the flapped airplane, no matter what the actual radius, will tend to look a lot better doing it, and can do it in an otherwise competitive package- that is, competitive in National competition. Aldrich figured it out in 1951, if you are going to get judged for appearance, you had better put on a good finish on a pretty airplane, and those weigh something, so design the airplane to handle this, instead of designing "max performance" airplanes with silkspan and a few coats of dope to seal it up, or severely compromised "flexible fliers" with hypothetically high performance, but changing wildly from second to second and day to day.

     The "narrow and long" VS "wide but partial span" is a different point, this is about how much additional Cl you get VS how much hinge moment you require.

     Brett

Online Dave_Trible

  • 2017
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4415
Re: Elevator width
« Reply #37 on: October 12, 2018, 10:47:39 AM »
Hi Dave & Ken,
After switching to my computer and slowing it down as you suggested, I don't see that at all.  What I saw was a model that wasn't properly trimmed against a very well trimmed model and higher caliber pilot (not trying to run anyone down at all).  The Primary Force in the Video was somewhat nose heavy, you could tell by watching the inside or outside loops because they tended to open up.  Now if you would have shown Brett and his Skyray it would have been at better example. 

Flapped models do tend to look slightly slower in corners but not necessary tighter in my opinion.  I'm not anti flap at all but after watching modelers for years flying models that aren't properly trimmed.  Over the years there are some really good models that don't have flaps and even a National Champion (Bob Baron) flying a flapp-less design.  Yes he was very gifted pilot and worked really hard at it. 

I've built many flapped models and most of them flew just fine after lots of trimming.  What gave me a clue on all of this was Ted Fancher, I reduced the flap area on my next model and it turned more like Teds, Davids, Paul, Billy, and the French guy with really small flaps on his model.  So I designed a flap-less model for profile stunt that worked really well (and now the XL that works even better).  I'm not trying to change the minds of people and saying flapp-less is the way to go, not at all.  Flying models such as many of the older models has showed me that it can be done with great results.

Later,

Mikey
Hi Mike.  Iíve seen a number of your airplanes being flown and they surely do fly very well.  As well as anything without flaps Iíve seen.  I wasnít really discussing turn radius.  It was really about the appearance of the turn.  I can remember watching Bob Baron fly his Humbug and the later airplane without flaps but looked like the Avanti (his flapped Nats winner).  Bob made it a point to note- and he was correct- they did the Ďroundestí round maneuvers of anything Iíve ever seen to date.  They DIDNíT fly the best corners by comparison to others.  From my own experiments with all manner of flap sizes I can tell you the angle of attack thing is real in various degrees and very obvious when you get the flap chord too wide.  It may well be that it might be ideal to switch off the flaps for rounds and turn them back on for corners!  That in a sense is what I think Igor is doing with his flap gadget.  I believe with the flaps deployed we are messing with the thrust vector AND AoA which canít be good for tracking rounds.  Yes it is also true your sharpest corners will be with smaller flaps -and a wing loading light enough for smaller flaps.  I canít imagine trying to turn one of my aerial trucks without the flaps.  :-))

Dave
AMA 20934
FAA Certificate FA3ATY4T94

Online Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 10470
Re: Elevator width
« Reply #38 on: October 12, 2018, 11:38:14 AM »
... That in a sense is what I think Igor is doing with his flap gadget...

Unless my built-in CAD (Cranial Aided Design) system is malfunctioning, Igor's logarithmic flap gadget* causes the flap action to level off at high deflections, so you get lots of flap authority for the rounds, but not much more than that for the corners.

* Are you sure it's a gadget and not a gizmo?  I've been thinking it's a gizmo.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Dave_Trible

  • 2017
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4415
Re: Elevator width
« Reply #39 on: October 12, 2018, 11:47:43 AM »
Well I might be wrong- havenít studied it that close-  Tim if you are trying to confuse me- your too late.  Iíve done that already.

Dave
AMA 20934
FAA Certificate FA3ATY4T94

Online Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 10470
Re: Elevator width
« Reply #40 on: October 12, 2018, 12:35:17 PM »
Well I might be wrong- havenít studied it that close-  Tim if you are trying to confuse me- your too late.  Iíve done that already.

Here's a page on the thing.  It definitely gives a curved relationship between elevator deflection and flap deflection, and the slope of that curve definitely flattens out in the corners.

I think the idea is that Igor wanted more turn in a corner (for nice sharp corners), and more of that "tangential to the circle" effect in the rounds.  His mechanism achieves that.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Ken Culbertson

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 692
Re: Elevator width
« Reply #41 on: October 12, 2018, 12:40:56 PM »
    What you are seeing is at least partially an optical illusion
     Brett
Thank you for explaining what I was trying to say and, by the way, for that video.

I am not sure how the tracking software we see from time to time works but I would be curious to see the same flight tracked from the nose of the plane then from the tail.  My theory is that the flapless plane would show nearly the same track on both where the flapped plane would show tighter corners when tracking from either the nose or the tail.  My guess is that it would be the tail - that is where I guess the optical illusion comes from.

Ken
AMA 15382

If it is not broke, don't fix it.

Online Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 10470
Re: Elevator width
« Reply #42 on: October 12, 2018, 01:14:02 PM »
I am not sure how the tracking software we see from time to time works but I would be curious to see the same flight tracked from the nose of the plane then from the tail.  My theory is that the flapless plane would show nearly the same track on both where the flapped plane would show tighter corners when tracking from either the nose or the tail.  My guess is that it would be the tail - that is where I guess the optical illusion comes from.

That's actually the opposite of what I'd expect.

I have made my own personal observations of planes in flight, and it looks like a flapped plane does a better job of flying tangent to the circle that it's cutting in the sky, while a flapless plane tends to point to the inside of the corner that it's flying.

This is consistent with what you'd expect if you thought about how an airplane develops lift.  In order to get the lift to go around a corner, a flapless plane must first turn itself, because the only control it has over the wing's lift in the wing's angle of attack.  This means that the wing -- and, of necessity, the whole airplane -- must be pointed "up" with respect to its line of travel.  Conversely, a flapped plane can change the amount of lift it develops without changing the fuselage's angle of attack.  So a correctly set-up flapped plane can fly in a circle while keeping it's fuselage centerline tangent to the circle it's traveling on.

This is actually a feature in Paul Walker's trimming process -- you fly level laps both upright and inverted, and observe whether you're nose-up or nose-down in each position.  You can change how much the nose moves up or down with the flap-elevator ratio, and you can change a bias to up or down with the flap-elevator bias.  Having the plane fly dead level both upright and inverted translates (more or less) to having it stay tangent to the loop in a round maneuver.

I need to review the videos (or track down one with Brett flying a Skyray), and see if I can see what you guys are all seeing.  Or maybe just to find more fuel to add to the fire.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Ron Santia

  • Trade Count: (0)
  • New Pilot
  • *
  • Posts: 7
Re: Elevator width
« Reply #43 on: October 12, 2018, 03:10:21 PM »
I serched and serched but can't find a video of Bret flying the skyray. If anybody finds it could you let me know.  I have a skyray, would love to see how good they can fly..  Thanks ,     Ron
AMA# 1004982

Offline Ken Culbertson

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 692
Re: Elevator width
« Reply #44 on: October 12, 2018, 03:48:25 PM »
That's actually the opposite of what I'd expect.

I have made my own personal observations of planes in flight, and it looks like a flapped plane does a better job of flying tangent to the circle that it's cutting in the sky, while a flapless plane tends to point to the inside of the corner that it's flying.


In level flight there is no difference in a flapped and non flapped plane.  The flaps are nothing more than giant trim tabs until you give it a control input.  Flapless only chages the angle of attack of the wing, flapped changes the angle, the airfoil and the center of lift.  Too many unknown variables in the same equation.

https://www.google.com/imgres?imgurl=https%3A%2F%2Fs3.amazonaws.com%2Flowres.cartoonstock.com%2Fmiscellaneous-worms-can-tin-opening_a_can_of_worms-opening-jfa2492_low.jpg&imgrefurl=https%3A%2F%2Fwww.cartoonstock.com%2Fdirectory%2Fo%2Fopening_a_can_of_worms.asp&docid=ewKoVtXwRkFB5M&tbnid=nmJmcHIcGyKQLM%3A&vet=10ahUKEwiGtsy68YHeAhUBU98KHZ-YCowQMwg2KAEwAQ..i&w=400&h=495&client=firefox-b-1&bih=600&biw=931&q=can%20of%20worms&ved=0ahUKEwiGtsy68YHeAhUBU98KHZ-YCowQMwg2KAEwAQ&iact=mrc&uact=8
AMA 15382

If it is not broke, don't fix it.

Offline Steve Helmick

  • AMA Member and supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 8313
Re: Elevator width
« Reply #45 on: October 12, 2018, 03:54:45 PM »
 

Brett flying the dreaded Skyray plus Dave Fitzgerald flying his Thunder Gazer.

 

This is a decent video (from the pilot's view) of a Strega...which
should give a more obvious viewpoint of the "big flaps" sort of design and the way it'll fly...but it actually looks quite good to me, at 25% speed. NOT what I have personally observed of a Strega, OBTW. What I've seen was VERY soft corners, to the point of wondering what trick the pilot was doing.  H^^ Steve


PS: I went to YouTube and my search was for "Brett + Buck + Skyray". That's kinda the way to do a search...
« Last Edit: October 12, 2018, 05:12:53 PM by Steve Helmick »
In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.

In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

"Be polite, be professional, but have a plan to kill everybody you meet." General Mattis.

Online Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 9047
Re: Elevator width
« Reply #46 on: October 12, 2018, 05:23:46 PM »
In level flight there is no difference in a flapped and non flapped plane.  The flaps are nothing more than giant trim tabs until you give it a control input.

   No, the flapped airplane flies at a slightly lower angle of attack (of the fuselage), everything else being equal. It's no different from a "equilibrium" condition in a turn, except for the degree of difference.

     Brett
 
« Last Edit: October 12, 2018, 07:09:21 PM by Brett Buck »

Online Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 10470
Re: Elevator width
« Reply #47 on: October 12, 2018, 06:01:01 PM »
In level flight there is no difference in a flapped and non flapped plane.  The flaps are nothing more than giant trim tabs until you give it a control input.  Flapless only chages the angle of attack of the wing, flapped changes the angle, the airfoil and the center of lift.  Too many unknown variables in the same equation.

1: In level flight you're always giving small control inputs.  You would like that to result in a lot more "up" and "down" than it does pitch changes, and you can achieve that with flaps.
2: If you mean just upright level flight, sure.  But if you mean both upright and inverted -- no.  The non-flapped plane has to have a bit of nose-up trim (up as in "toward the sky", not "toward the canopy") both upright and inverted.  The flapped plane can be made to fly perfectly level both ways -- see the link to Paul Walker's trim discussion that I posted above.
3: If you know how the wing works then all three of your "unknowns" are dependent on the control input at the leadouts.  So, not that bad.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.


Tags: