News:


Advertise Here

  • December 07, 2021, 11:38:42 AM

Login with username, password and session length

Author Topic: Blunt leading edge  (Read 3582 times)

Offline Air Ministry .

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 4312
Re: Blunt leading edge
« Reply #100 on: November 23, 2021, 05:44:01 PM »


Tripped overthis so Why Not . Eastern Block job

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #101 on: November 23, 2021, 05:59:27 PM »
a " BLUNT " leading edge , in the extreme , would be flat , vertical , the depth of the wing !  S?P


This ones got a blunt trailing edge too .  S?P

My thinkng is the ' way round ' full size plane aerobatic airfoil , is in part , to enhance the rate of roll .
As in , a sharper L E is gunna need greater forward tavel per degree of roll .



The Eppler section E472 used on the Extra would be a bad choice for a model. It was designed to be able to Snap Roll and in models it will cause quite a bit of bad things to happen. Further, it really doesn't have good drag and Cl numbers. Even the full size extra will "tell you" about pulling too hard. There are much better selection for the models than this one.

The rolling rate isn't so much the airfoil but the size of the aileron. Notice how far back on the aileron the hinge is. That's what I have been talking about with offset hinges. The hinge on the Extra is set back to about the 20% chord point.
 

Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Online Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 12238
Re: Blunt leading edge
« Reply #102 on: November 23, 2021, 06:58:33 PM »
The Eppler section E472 used on the Extra would be a bad choice for a model. It was designed to be able to Snap Roll and in models it will cause quite a bit of bad things to happen. Further, it really doesn't have good drag and Cl numbers. Even the full size extra will "tell you" about pulling too hard. There are much better selection for the models than this one.

    Agreed, they make them like this precisely because they have the characteristics we we arguing about before - they want it to snap roll abruptly, unlike conventional full-scale aircraft.

         Brett

Offline Serge_Krauss

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1334
Re: Blunt leading edge
« Reply #103 on: November 23, 2021, 07:58:37 PM »
My guess is that they wanted to compare the Guinn flap to something and picked models they had around to compare.  They had some with "plain" flaps and they appended the Guinn flap on another.  Do you reckon they picked the 15% foil based on thickness ratio, or did they run the Guinn flap case and then pick the plain-flap model that came close to the Guinn-flap model's lift curve.  They probably already had data on a range of plain-flap airfoils.

That was pretty much my guess, although I THINK I remember seeing a lot of 23012's in that period's researches. I should have noted (for Scott now) that the date of the TN is 1940. I also remember the best L/D numbers falling in the 15%-thickness area for RN's around 3 million. So , yeah, I think they picked the models they had. I don't remember any other reports at this low Reynolds number though - except that one about RN effects, which indicated two reversals of which thicknesses were "best" as RN's decreased below 1 M. I think they had to already have much data on plain flaps in the five-digit and other series by the time of this report, but there's only one way to find out, and that's not for me at the moment. Now, I just need to read the third-page posts.

Online Tim Just

  • 21 supporter
  • Trade Count: (0)
  • Ensign
  • *
  • Posts: 46
Re: Blunt leading edge
« Reply #104 on: November 23, 2021, 08:05:10 PM »
I found the Extra stall to be very benign.  Much better than a Mooney for example.  The  wing does give a good amount of feedback and will protest, but has no surprises if coordinated.  Anything else would be treacherous at contest or Airshow altitudes.

The Extra does snap well inside but has to be forced to do outsides.  Spins are opposite.  Inverted it is effortless but upright has do be set up just right or the airplane develops a high rate of sink and ignores the rudder.  C/G with me is close to aft limit.  The Extra 330SC solved the snap and spin issue with a much improved elevator, same airfoil.

Attached is my Extra at a reasonably high AOA

Offline Air Ministry .

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 4312
Re: Blunt leading edge
« Reply #105 on: November 23, 2021, 08:33:27 PM »
Not all gusts are the same .

2.2.1 Sharp-edge gust
The concept of sharp-edge gust was reported in 1931(Reference Rhode and Lundquist17). This simplest gust shape proposed by albeit a century ago, is still used for response analysis to date. The gust shape is of a step type, as shown in Fig. 3. The gust velocity profile can be expressed by Equation (6).


Figure 3. Illustration of sharp-edge gust velocity distribution.

(6)

where U is the gust maximum velocity value, u(s) is the gust velocity at any penetration distance, s.

The U.S. Bureau of Air Commerce regulated the first U.S. civil requirements related to gust loads in the ďAirworthiness Requirements for Aircraft Components and AccessoriesĒ issued in 1933(18). These requirements were merely based on the sharp-edge gust concept. The design gust velocity is 30 fps for aircraft at cruise speeds and 15 fps at dive speeds.

2.2.2 Linear-ramp gust
The linear-ramp gust concept had become apparent by the late 1930s. This concept was used to account for the differences in airplane motion due to gust encounter from one airplane to another. The linear-ramp gust shape means the gust velocity increases linearly with the gust gradient distance, as shown in Fig. 4. The gust velocity profile can be expressed by Equation (7),


Figure 4. Illustration of linear-ramp gust velocity distribution.

(7)

where, H is the gust gradient distance (horizontal distance from zero to maximum gust velocity, usually in wing chord length).

The regulations that resulted were contained in the 1941 issue of the Civil Aeronautics Manual (CAM 04)(19), where the equivalent gust velocity was specified as 40, 30 and 15 fps for three different forward air speeds.

2.2.3 One-minus-cosine gust
The current certification regulations utilise theoretical work undertaken by the NACA where the concept of one-minus-cosine gust was reported in 1953(Reference Pratt14). The gust shape is shown in Fig. 5 and is mathematically defined as


Figure 5. Illustration of one-minus-cosine gust velocity distribution.

(8)

where the symbols are identical to those for sharp-edge gust. In the whole history, the gust gradient distance H was designated to different values successively, such as 12.5 and 25 chords; however, the latest regulations of the gust gradient distance in FAR-25(20), CS-25(Reference Easa15) and JAR 25(21) require a sufficient number of gust gradient distance in the range of 30 feet to 350 feet to be investigated in order to find the critical response for each load quantity.

https://www.cambridge.org/core/journals/aeronautical-journal/article/gust-loads-on-aircraft/C37F9E9233E81557F8435CAA406DABB6

Some diagams there ,

Gusts effects begin to act in advance of the aircraftís encounter and last sometime even when the gust is located far away from the aircraft. This result is particularly important to flight dynamic performance of very flexible and light aircraft.

Was intresting the low darg tips on the Phantom stopped the yaw & roll in high wind through smaller tip vortices under high load / squares .
essentially tip rib at 45 deg. to vertical , canted . with top sheet running outward aft , about 15 m.m. wider . A straight line in planform from preceeding the max depth .


Offline Air Ministry .

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 4312
Re: Blunt leading edge
« Reply #106 on: November 23, 2021, 08:53:46 PM »
Tis with added swept top sheet , about the same as the tip flap chord ( 1 1/4 " ) wider . So as the sweep is OUT to + 5/8 at the rear . sanded and contured but just a 1/8 " sheet tacked on , sanded faired in finished .



Flying in 20 & 30 mph winds , with ' trees in the valley ' , the rolling air would pull it around , with a fair bit of control & load to counter . Slamming & heaving the handle helped it get turning ,
or it'd tend to wait for a break . Even if you got the nose up the breeze would hold it flattened level .

55 Ft. of .018 7 the little FSR 25 clone fighting away . Figured it matched Gieske's 58 ft. ( to center ? ) G Nobler .

Tered tend to be a ' ground flow ' of hard air till about 10 Ft. altitude .  50 / 80 Ft trees up & downwind would have you wander to find the least disrupted area ,
Downwind big bushy tree with branhes even from 8 or 10 Ft. As in a 8 / 10 foot clear under them had a big sucktion / venturie effect 60 ft. upwind , starting around 80  . Close Itd get pulled near into the ground .
The bigger tree upwind had massive turbulace within 100 / 150 foot .

Had a typal noblerish airfoil & construction , with only about 1/8 dia. front edge .
 Would stagger out off hard bottoms nose up at times , but not as bad as P J's
large noseweight version . More it had to old nose up to counter the sink it the air
which'd smatter about anything . Needed that weight of line in that air to steer .

The tips made it a bit less volitile but perhaps more effort to ' ungroove ' it to hit the turns .

Offline Air Ministry .

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 4312
Re: Blunt leading edge
« Reply #107 on: November 23, 2021, 09:00:49 PM »
O.K. call it 1/8 " Rad. , say 1/4 Dia. ' entry ' .



Seeing it again reminds us the anheadral Stab. , had sections NOT in the wing / flap wake . You could still feel it at times ,
but it didnt get the dull spot & thud or a tailplan working trough or out of the wing wash , when everythings earning its keep .

Will putta picha of the Strega LE ere , as its the 1/4 Sq. drg . and has very good bottoms at 5 ton / Sq Ft loading .
( With Very STIFF Flaps , Stab, Elevators & no control flex . Not to mention a bit of line tension , wearyingly so .

Offline Air Ministry .

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 4312
Re: Blunt leading edge
« Reply #108 on: November 23, 2021, 09:10:15 PM »
So BLUNT SHARP LEADING EDGE . 1/4 Sq with 1/16 + sheet stock ARC Strega . plus 80 Wt sandpaper & sanding block .
Tip .

Tip .

Root .


Whichifyoulookatit , is COMPLETELY DIFFERANT than to one at the Top of This Page .


and brings us to , nomatterwhatyouvegot , Zero Flex , smooth controls and  extreme torsional stiffness

are the priority , as nomatterwhatyouvegot as far as airfoils , if the rest is as soggey as eggs you shoulda hadit
as stiff as the egg shell . Edibility notwithstanding .

The 3/4 deep tailplane . NOT the kit one . Or Controlls , custom steel bushed 1/8 & 5/32 wire .
Initially hot weather got the vertical bellcrank pin binding , end float gallng . Cut & lube 7 a few blows with the 16 lb. hammer ( Taps with a drift ) has it smooth & no binding .
The tear  your arm out line tension overcame the friction initially though . So it stll grooved and hit turns . But the longer in the sun the stiffer & louder the binding was .   :P

Be intresed in Ted's comments on His ships of the big round front style airfoil , in conditions where youre hanging on like grim death , 25 Knots with a FSR , Ro Jett or P A - piped
and Working .

Mush , overheads & wakes .
Surpriseingly the 6 ft. Mewgull with a Merco 61 on a 12 x 6 was real good in 20 knot smooth wind . But crosswindat 50 foot would have it roll/ snap 45 degrees for a moment in the outside of the o. h. 8 .
On the Top three list to get onto & done . But again , required your full attention . Like Mototrcyles anything less is inadviseable usually anyway . Bout the same actually .Particularly in the city .

Not trying to say this is the only way to do it. Just jumped in and threw it on . Respect others evaluations and approaches . Suspect anything over 30 knot wind will have anything
not entirely under full exact control no matter HOW you go about it at either end of the lines .
« Last Edit: November 23, 2021, 09:56:16 PM by Air Ministry . »

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #109 on: November 24, 2021, 09:07:59 AM »
I found the Extra stall to be very benign.  Much better than a Mooney for example.  The  wing does give a good amount of feedback and will protest, but has no surprises if coordinated.  Anything else would be treacherous at contest or Airshow altitudes.

The Extra does snap well inside but has to be forced to do outsides.  Spins are opposite.  Inverted it is effortless but upright has do be set up just right or the airplane develops a high rate of sink and ignores the rudder.  C/G with me is close to aft limit.  The Extra 330SC solved the snap and spin issue with a much improved elevator, same airfoil.

Attached is my Extra at a reasonably high AOA

Very cool photo... The key words here are "if coordinated" which means the airplane is pointed straight ahead with no yaw / skid when the stall occurs. With a pilot onboard this is fairly straight forward. On a model that generally doesn't happen and there is some yaw when the airplane stalls. The Eppler stall characteristic shape is "peaky" which is to say it has a continuous Cl curve which is sharp, bends quickly, but has no discontinuity. This is desirable for the 4/4 aerobatic airplane because it leads to a controllable stall which can be "commanded" to autorotate (snap / spin). An undesirable characteristic of the shape is when there is a step change in CL which occurs over a small angle of attack as airfoils like the 23012. The yaw during stall creates a different angle of attack between the two wings and if the section has a discontinuity as in my graph in a previous post then huge rolling and yawing moments result. That accounts for the Mooney v Extra as I think the Mooney uses the 23012 which does have a significant discontinuity in the Cl curve. It's  misunderstanding about aerobatic airplanes thinking they are tougher to fly, they aren't, if anything they are easier by design.

Why the E472 isn't a good option for the model lies in the way the airfoil behaves as the Rn is reduced. For the operating range Rn of the 4/4 Extra the E472 has a fairly smooth CL curve at stall although is bends quickly. At lower Rn numbers the sharpness turns in to abrupt separation creating the Cl curve discontinuity which makes for a bad behaving model. To exacerbate this problem it is common practice in the control line arena to cause the airplane to yaw outward which is the perfect recipe to generate the "snap roll ona string" hinging. The characteristic of an airfoil for a well behaving model has a smooth Cl curve around the stall Cl.   

Unfortunately the understanding of this involves all of those graphs and such which aren't very popular to fully understand.  Words simply won't fully convey the concept.  Having said all of the above, the E47x series airfoils are good coordinate donors for modification in which to tune for application. Primarily for the lower Rn reducing the nose roundness "radius" would help and adding some thickness behind the max thickness.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Online Howard Rush

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7465
Re: Blunt leading edge
« Reply #110 on: November 24, 2021, 02:24:10 PM »
At lower Rn numbers the sharpness turns in to abrupt separation creating the Cl curve discontinuity which makes for a bad behaving model.
To exacerbate this problem it is common practice in the control line arena to cause the airplane to yaw outward which is the perfect recipe to generate the "snap roll ona string" hinging. The characteristic of an airfoil for a well behaving model has a smooth Cl curve around the stall Cl.   

Your comments may apply to your application, but, as previously explained, not to control line airplanes optimized for either stunt or combat competition, where we want more Clmax.  The "snap roll on a string" is benign: you won't crash.  I don't remember ever seeing it on my stunt planes, and, as previously explained, we trim it out of combat planes.  You can still get it with a full load of fuel in combat if you overcontrol the airplane, but it won't cost you the match.


Unfortunately the understanding of this involves all of those graphs and such which aren't very popular to fully understand.  Words simply won't fully convey the concept. 

I don't know about being popular to fully understand, but I can't understand a graph that was autoscaled with too few decimal places.

Having said all of the above, the E47x series airfoils are good coordinate donors for modification in which to tune for application. Primarily for the lower Rn reducing the nose roundness "radius" would help and adding some thickness behind the max thickness.

Although it's been more than 30 years since I used an Eppler 47x airfoil on airplanes at a world championships, I remember it as working OK.  Gary James has showed us that airfoils modified opposite to your advice (increased LE radius, fatter in front of the max thickness) work even better.   
The Jive Combat Team
Making combat and stunt great again

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #111 on: November 24, 2021, 04:04:56 PM »
Your comments may apply to your application, but, as previously explained, not to control line airplanes optimized for either stunt or combat competition, where we want more Clmax.  The "snap roll on a string" is benign: you won't crash.  I don't remember ever seeing it on my stunt planes, and, as previously explained, we trim it out of combat planes.  You can still get it with a full load of fuel in combat if you overcontrol the airplane, but it won't cost you the match.


I don't know about being popular to fully understand, but I can't understand a graph that was autoscaled with too few decimal places.

Although it's been more than 30 years since I used an Eppler 47x airfoil on airplanes at a world championships, I remember it as working OK.  Gary James has showed us that airfoils modified opposite to your advice (increased LE radius, fatter in front of the max thickness) work even better.


The snap roll ona string is a description of a kind of hinging I see occasionally when the airplane stalls during some maneuvers. A normally good flying plane with limited hinging will, at times produce this. Note to self, don't pull too hard as Brett would say. My note to self, next airplane fix that. I don't disagree with Brett except that I won't tolerate it if I don't have to. I have seen a very interesting video of a CL biplane doing and absolutely wonderful snap roll to destruction.

Yes, it is true that in general moving the max thickness forward can improve the Cl max but too far forward requires moving it rearward again. The E47x are in this state. What happens is the rapid velocity increase around the big round nose creates low pressure which then faces a long trip back to the high pressure zone. You can see this on the E472 graph as the reynolds numbers drop in the Summary of Low Reynolds Number Report . The result of this is separation towards the front first creating the undesirable stall characteristic.

For the stunt model the non flapped airfoils Clmax is pretty much irrelevant as the flap changes that significantly. The forward profile has some impact though and its character plays  roll in the flapped performance.

I'm going to guess the graph I put up which doesn't make sense is the Cd v Cl polar. Which I didn't save. In general, I don't take the model as a gospel but rather a tool to understand dependencies. I don't have the desire to spend the time and resources to verify the models and as such any confirmation I may make is qualitative. I'm assuming that your testing is quantitative and confirm the numbers directly via test. So any graph I generate shows the difference in characteristic or a characteristic of interest or how  it may change. Overlaying different airfoils on the Cd v Cl polar is one of the methods of comparison. It is the speed range and maneuvering performance.

In general though my comment was more about that not many people really get graphs. I guess my humor was missed yet agin.

Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #112 on: November 24, 2021, 04:12:35 PM »
This one is sad but it is and example of a poorly behaving airfoil causing the snap roll ona string. In this case more like a spin but same difference a snap roll is just a spin going in a different direction. Probably from yawing outward. The airplane was flying slow and the pull to recover pushed the airplane to stall. The inside wing stalled first. Once started autorotation is self progressing and in this case unrecoverable. You can see the inside wing dip at 5:14. That was the wing stalling. Some call it tip stall. But it is that discontinuity of the lift curve at stall that drives it. The recovery is to release the back pressure but sometimes the reflexes won't allow it as in this case. The nose is down and the desire is to pull harder which only makes things worse.



Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Online Dan McEntee

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 5086
Re: Blunt leading edge
« Reply #113 on: November 24, 2021, 06:01:46 PM »
   I've watched that video before. Looked like an official flight in a scale contest. After flying his twelve laps, high flight and a touch and go, I wonder if he didn't have some sort of control failure in the elevator? He was flying 7 or 8 second laps, so I don't think he tried a loop, but may have been an attempt at a wingover?  It was such a shallow climb that I'm thinking it wasn't and he just lost elevator control, it climbed up and got even slower and into the stall realm of things. That snap to the left , though was just as you call it, and really surprised me the first time I saw it. A few more RPM and a few less pounces of weight would have helped a lot. The trees seemed still enough, so don't know if a gust of wind caused anything. Just ran out of air speed, altitude and ideas all at the same time!
  Type at you later,
   Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #114 on: November 24, 2021, 06:14:03 PM »
   I've watched that video before. Looked like an official flight in a scale contest. After flying his twelve laps, high flight and a touch and go, I wonder if he didn't have some sort of control failure in the elevator? He was flying 7 or 8 second laps, so I don't think he tried a loop, but may have been an attempt at a wingover?  It was such a shallow climb that I'm thinking it wasn't and he just lost elevator control, it climbed up and got even slower and into the stall realm of things. That snap to the left , though was just as you call it, and really surprised me the first time I saw it. A few more RPM and a few less pounces of weight would have helped a lot. The trees seemed still enough, so don't know if a gust of wind caused anything. Just ran out of air speed, altitude and ideas all at the same time!
  Type at you later,
   Dan McEntee

I don't know but could be. I watched in slow mo to see what was going on and I don't think I saw any elevator movement at the stall which is a typical reflex. Usually what happens in this scenario is the airplane pitches down and the pilot pulls back. I think he was just putting around trying to be "scale like" and the climb sucked the last bit of energy out, the airplane stalled and spun to the ground. It probably shocked him and he didn't have a chance to respond which probably wouldn't have done any good.

Actually, I just watched it again and could see an intentional pull up to what might have been a wing over of sorts. The airplane "told him" it didn't want to do it. Watch carefully the first part of the climb. The inside wing dipped twice and  the second time probably made the lines slack and they just came back when  the airplane snapped probably from up elevator effort.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline frank williams

  • AMA Member
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 681
Re: Blunt leading edge
« Reply #115 on: November 24, 2021, 06:56:21 PM »
In low Reynolds number airfoil analysis, there is one airfoil that is always included in any work that is done.  The Wortmann FX63-137 has shown remarkable performance through the years.  The maximum lift coefficient is above 1.5 generally, and the stall is pretty benign.  It has as high an L/D as any airfoil around.  I think this airfoil has been used for some of the human powered airplanes attempts.

I know I poo pooed the small sheet flap extension on the symmetrical airfoil from a few posts back as not being a driver in the flow conditions and here I am touting  a radical under cambered  airfoil.  Granted the FX 63-137 is a highly under-cambered airfoil and not a symmetrical airfoil like used for pa airplanes, but Iíve always thought that the upper surface curvature might be of special importance.  It might be magic.  This upper surface seems to hold onto the flow better than most airfoils.  I wonder what would happen if I took this upper surface and flipped it over to make a symmetrical airfoil.  Would the surface be as ďstickyĒ when applied as a symmetrical foil.

I built a mold to form the surface skins because I  didnít  think that a rib and fabric construction would accurately enough replicate the surface.   It makes a pretty thick section.  Itís not too blunt or too sharp.  The fully sheeted wing makes for a bit heaver airplane.  The half wing and flap in the photo is 11.7 ounces.   Does it fly better and stall later?   So far I havenít had a stall in the 3rd corner of the hourglass or triangle and it s a 70+ oz. ship.  But I must admit that I havenít actually had opportunity to fly it a whole bunch.

Online Howard Rush

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7465
Re: Blunt leading edge
« Reply #116 on: November 24, 2021, 07:01:20 PM »
This, of course, reminds me of a story. One can make a Flite Streak spin.  Not a whole Flite Streakó first you have to remove the outside wing. This can be done by flying combat with it.  Fly the remaining Flite Streak high and give it up elevator abruptly. It will spin and chew up a set of lines. You should get out of the way, because it will land of the center of the circle. This can be done remarkably consistently.
The Jive Combat Team
Making combat and stunt great again

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #117 on: November 24, 2021, 07:13:59 PM »
This, of course, reminds me of a story. One can make a Flite Streak spin.  Not a whole Flite Streakó first you have to remove the outside wing. This can be done by flying combat with it.  Fly the remaining Flite Streak high and give it up elevator abruptly. It will spin and chew up a set of lines. You should get out of the way, because it will land of the center of the circle. This can be done remarkably consistently.

I'm spittin snot..... Thanks...
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #118 on: November 24, 2021, 07:35:48 PM »
In low Reynolds number airfoil analysis, there is one airfoil that is always included in any work that is done.  The Wortmann FX63-137 has shown remarkable performance through the years.  The maximum lift coefficient is above 1.5 generally, and the stall is pretty benign.  It has as high an L/D as any airfoil around.  I think this airfoil has been used for some of the human powered airplanes attempts.

I know I poo pooed the small sheet flap extension on the symmetrical airfoil from a few posts back as not being a driver in the flow conditions and here I am touting  a radical under cambered  airfoil.  Granted the FX 63-137 is a highly under-cambered airfoil and not a symmetrical airfoil like used for pa airplanes, but Iíve always thought that the upper surface curvature might be of special importance.  It might be magic.  This upper surface seems to hold onto the flow better than most airfoils.  I wonder what would happen if I took this upper surface and flipped it over to make a symmetrical airfoil.  Would the surface be as ďstickyĒ when applied as a symmetrical foil.

I built a mold to form the surface skins because I  didnít  think that a rib and fabric construction would accurately enough replicate the surface.   It makes a pretty thick section.  Itís not too blunt or too sharp.  The fully sheeted wing makes for a bit heaver airplane.  The half wing and flap in the photo is 11.7 ounces.   Does it fly better and stall later?   So far I havenít had a stall in the 3rd corner of the hourglass or triangle and it s a 70+ oz. ship.  But I must admit that I havenít actually had opportunity to fly it a whole bunch.

I built some FF models utilizing some of the Wortman sections in my younger years. I'm going to say my intuition is that you are correct in your assumption. I didn't take that you were poo pooing the thin flap. Personally I have always thought of the flat plate Gwinn flap, didn't know it had a name until recently, worked much like the concave (?) r portion of the laminar sections in that it helped reduce the adverse pressure gradient which TN 763 confirmed for me. That confirmation comes from the Cl v Cd polar where the Gwinn performs better at higher Cls for drag. It's unfortunate they didn't generate Cp plots in their testing. Oh well. I do have the Wortman in my arsenal of tools and I'll make a run at the Symmetrical version. I think it's worth pursuit.

You may have diverged me once again from my current wing project. The larger flap area ratio of that wing messes up the section in more ways than just the aerodynamics. When scaled a "normal" airfoil ends up with the spar much forward of the wing MAC Cg which means a section redesign would be good. 
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Online Dan McEntee

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 5086
Re: Blunt leading edge
« Reply #119 on: November 24, 2021, 07:39:06 PM »
I don't know but could be. I watched in slow mo to see what was going on and I don't think I saw any elevator movement at the stall which is a typical reflex. Usually what happens in this scenario is the airplane pitches down and the pilot pulls back. I think he was just putting around trying to be "scale like" and the climb sucked the last bit of energy out, the airplane stalled and spun to the ground. It probably shocked him and he didn't have a chance to respond which probably wouldn't have done any good.

Actually, I just watched it again and could see an intentional pull up to what might have been a wing over of sorts. The airplane "told him" it didn't want to do it. Watch carefully the first part of the climb. The inside wing dipped twice and  the second time probably made the lines slack and they just came back when  the airplane snapped probably from up elevator effort.

   Next time freeze it just after impact, and look where the pilot is standing. He's almost on the circle, no where near the center pad. I think he lost it in the climb, and prop pitch and torque started bringing it in on him so he headed out to try to get tension back. I don't think it was under control at all once the nose when up and it got to higher than 45 degrees and it free flighted the rest of the way. That is what let it roll as violently as it did, no tension at all.  Whatever it was, it's a shame and the guy lost a nice model.  If things aren't optimal, it's best to just fly it out safe and get it down in one piece.
  HAPPY THANKSGIVING!
  Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Scott Richlen

  • AMA Member
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1881
Re: Blunt leading edge
« Reply #120 on: November 24, 2021, 08:17:23 PM »
Back in the days of the "traveling Nats" you could see lots of different events.  One of my favorites was Scale.  A common characteristic of the scale guys is that they would spend all their time building, almost none flying.  Many times the first time a scale plane would fly was at the Nats.  It could be very exciting and often gruesome since they may not have been trimmed at all.  Nothing like flying tail-heavy!  I recall a beautiful WWII warbird at the Chicopee Nats (don't remember any more if it was a Hurricane or a Zero or...) being released for take-off and almost immediately going into a wing-over ending in a resounding "Splat!" into the asphalt on the opposite side of the circle.  Yikes!  Alnost as much carnage at the scale circles sometimes as at the combat circles.

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #121 on: November 24, 2021, 08:18:11 PM »
   Next time freeze it just after impact, and look where the pilot is standing. He's almost on the circle, no where near the center pad. I think he lost it in the climb, and prop pitch and torque started bringing it in on him so he headed out to try to get tension back. I don't think it was under control at all once the nose when up and it got to higher than 45 degrees and it free flighted the rest of the way. That is what let it roll as violently as it did, no tension at all.  Whatever it was, it's a shame and the guy lost a nice model.  If things aren't optimal, it's best to just fly it out safe and get it down in one piece.
  HAPPY THANKSGIVING!
  Dan McEntee

I did. He had full up elevator in it. The second snap ona string caused it to get loose. The catching up and getting line tension with full up elevator finished it. I prolly woulda done the same. Not really, I wouldn't have flown it with half throttle. I'd have been blasting full bore tearing up the sky. In my version it'd have exploded in flight sheading debris in to the wind. It would have been epic... Just sayin..
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Online Dan McEntee

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 5086
Re: Blunt leading edge
« Reply #122 on: November 24, 2021, 08:43:00 PM »
I did. He had full up elevator in it. The second snap ona string caused it to get loose. The catching up and getting line tension with full up elevator finished it. I prolly woulda done the same. Not really, I wouldn't have flown it with half throttle. I'd have been blasting full bore tearing up the sky. In my version it'd have exploded in flight sheading debris in to the wind. It would have been epic... Just sayin..

  I expanded the screen this time to watch it again. It was a nice looking Neuport 11 with Lafayette Escadrille markings. It's kind of a mascot of the club I belong to, the Lafayette, Esquadrile. The different spelling is along story. The model looked to be pretty well trimmed. It didn't act like it was tail heavy, properly balanced and was only rocking a bit in some sort of breeze. The pilot looked to be signaling before each maneuver. It looked in decent shape while flying at 45 degrees for several laps. Then he signaled again for some climbs and dives, and then again for a touch and go. No apparent problems there. He signaled one more time and a lap later pulled up. At about 45 degrees or higher is when I think it initially stalled and broke left and the rest was history. I'm changing my assessment to attempting a wingover of some sort, and then he who stalleth, falleth. Like Scott surmised, I have watched a lot of scale pilots struggle with flying their models, over weight and not balanced and agree with his view. This guy looked to be in pretty good control until that one point. Just too slow Should have put the throttle forward through the stops! ( or at least pulled the trigger back through the stops! Still sad. I'll bet he wished he would have waved it off and got a better engine run.
  Type at you later,
  HAPPY THANKSGIVING!
  Dan McEntee
   

 
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Brent Williams

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 991
  • Making America Fly Stunt Again!
    • Fancher Handles - Presented by Brent Williams
Re: Blunt leading edge
« Reply #123 on: November 24, 2021, 09:32:01 PM »
In low Reynolds number airfoil analysis, there is one airfoil that is always included in any work that is done.  The Wortmann FX63-137 has shown remarkable performance through the years.  The maximum lift coefficient is above 1.5 generally, and the stall is pretty benign.  It has as high an L/D as any airfoil around.  I think this airfoil has been used for some of the human powered airplanes attempts.

I know I poo pooed the small sheet flap extension on the symmetrical airfoil from a few posts back as not being a driver in the flow conditions and here I am touting  a radical under cambered  airfoil.  Granted the FX 63-137 is a highly under-cambered airfoil and not a symmetrical airfoil like used for pa airplanes, but Iíve always thought that the upper surface curvature might be of special importance.  It might be magic.  This upper surface seems to hold onto the flow better than most airfoils.  I wonder what would happen if I took this upper surface and flipped it over to make a symmetrical airfoil.  Would the surface be as ďstickyĒ when applied as a symmetrical foil.

I built a mold to form the surface skins because I  didnít  think that a rib and fabric construction would accurately enough replicate the surface.   It makes a pretty thick section.  Itís not too blunt or too sharp.  The fully sheeted wing makes for a bit heaver airplane.  The half wing and flap in the photo is 11.7 ounces.   Does it fly better and stall later?   So far I havenít had a stall in the 3rd corner of the hourglass or triangle and it s a 70+ oz. ship.  But I must admit that I havenít actually had opportunity to fly it a whole bunch.

Here is an example of the upper section of the Wortman FX63-137 taken from Profili, then flipped and stacked. 
Looks quite a bit like an Al Rabe or Igor Burger type section this way. 
« Last Edit: November 24, 2021, 09:53:39 PM by Brent Williams »
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 Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #124 on: November 24, 2021, 09:38:08 PM »
  I expanded the screen this time to watch it again. It was a nice looking Neuport 11 with Lafayette Escadrille markings. It's kind of a mascot of the club I belong to, the Lafayette, Esquadrile. The different spelling is along story. The model looked to be pretty well trimmed. It didn't act like it was tail heavy, properly balanced and was only rocking a bit in some sort of breeze. The pilot looked to be signaling before each maneuver. It looked in decent shape while flying at 45 degrees for several laps. Then he signaled again for some climbs and dives, and then again for a touch and go. No apparent problems there. He signaled one more time and a lap later pulled up. At about 45 degrees or higher is when I think it initially stalled and broke left and the rest was history. I'm changing my assessment to attempting a wingover of some sort, and then he who stalleth, falleth. Like Scott surmised, I have watched a lot of scale pilots struggle with flying their models, over weight and not balanced and agree with his view. This guy looked to be in pretty good control until that one point. Just too slow Should have put the throttle forward through the stops! ( or at least pulled the trigger back through the stops! Still sad. I'll bet he wished he would have waved it off and got a better engine run.
  Type at you later,
  HAPPY THANKSGIVING!
  Dan McEntee
   

 

Pretty much my assessment as well.

Happy Thanksgiving.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline Serge_Krauss

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1334
Re: Blunt leading edge
« Reply #125 on: November 24, 2021, 09:52:21 PM »
Unfortunately, my Profili is no longer licensed (should I trust PayPal?); so to see Frank's Wortman idea, I had to convert to JPEG, edit to create halves, insert into Word, arrange the halves, and photograph my monitor....not pretty, but I like the idea. I'm wondering whether I would ruin the whole idea by thinning it and stretching to move the point of maximum thickness forward from that 37%(?) point for a flapless plane. If I just added a flap, as Frank apparently did, or stationary "flap," the "high point" would move from that .37 Chord point to .31C - .32C and reduce the thickness to around 20%. I wonder though whether that might raise pressure near the flap and defeat the purpose -  'just playing with ideas. I can't use this picture though. I presume this one undercambered section is in the Profili library now.

SK

Edit: Sorry! I somehow missed Brent's post above. Questions are the same though.
« Last Edit: November 25, 2021, 12:14:30 AM by Serge_Krauss »

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #126 on: November 25, 2021, 06:20:24 AM »
Unfortunately, my Profili is no longer licensed (should I trust PayPal?); so to see Frank's Wortman idea, I had to convert to JPEG, edit to create halves, insert into Word, arrange the halves, and photograph my monitor....not pretty, but I like the idea. I'm wondering whether I would ruin the whole idea by thinning it and stretching to move the point of maximum thickness forward from that 37%(?) point for a flapless plane. If I just added a flap, as Frank apparently did, or stationary "flap," the "high point" would move from that .37 Chord point to .31C - .32C and reduce the thickness to around 20%. I wonder though whether that might raise pressure near the flap and defeat the purpose -  'just playing with ideas. I can't use this picture though. I presume this one undercambered section is in the Profili library now.

SK

Edit: Sorry! I somehow missed Brent's post above. Questions are the same though.

No, DO NOT trust PayPal. They decided our business did not fit within their moral standards and cleaned out our account. Many thousands of dollars. They call a fee for violating their policies which you cannot find in detail.

Having said that, excel is the easiest way to do the coordinate task. Just take them massage. I you wish, I'll provide them to you. I'm way past you on the evaluation. It was the first thing I did when you mentioned it. As is it turns in to a 20% ish section has a decent Cl curve a sharpish stall and decent Cl v Cd polar. Not an airplane killer like the above biplane. I'd use it. I also did a couple thickness variations to see the impacts but unfortunately my program crashed and I had to head to bed. I'll see what I can produce. Any specific requests?

Attached coordinates
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline Serge_Krauss

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1334
Re: Blunt leading edge
« Reply #127 on: November 25, 2021, 07:52:51 AM »
Thanks, Mark. I guess I'm a dunce when it comes to my current Microsoft stuff. Sometimes, as has just happened, I try to open a file by clicking on a link and it asks what program I want to use to open it. I try a couple, and it then fixates on the last unsuccessful attempt and from then on gives an error message saying that last program cannot open the file, no longer giving me a choice. That's where I am now, unable to open your coordinate file. Maybe I should have used Excel. Anyway, I've never before had it not renew, when I re-entered the site. - SK

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #128 on: November 25, 2021, 08:13:01 AM »
Thanks, Mark. I guess I'm a dunce when it comes to my current Microsoft stuff. Sometimes, as has just happened, I try to open a file by clicking on a link and it asks what program I want to use to open it. I try a couple, and it then fixates on the last unsuccessful attempt and from then on gives an error message saying that last program cannot open the file, no longer giving me a choice. That's where I am now, unable to open your coordinate file. Maybe I should have used Excel. Anyway, I've never before had it not renew, when I re-entered the site. - SK

right click on the file, choose properties, select note pad or word pad.  Or ask me to rename the file. They're just text files but they are in the data folder for the application I use which requires the *.dat extension.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #129 on: November 25, 2021, 09:39:40 AM »
right click on the file, choose properties, select note pad or word pad.  Or ask me to rename the file. They're just text files but they are in the data folder for the application I use which requires the *.dat extension.

The attached file is the NACE section not the Wortman. I encountered a file corruption issue when moving data back and forth. I'm going to redo the whole effort and repost once I figure out what what its actually what.
 
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline frank williams

  • AMA Member
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 681
Re: Blunt leading edge
« Reply #130 on: November 25, 2021, 10:12:43 AM »
cant view the graphs ... that disappeared ....

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #131 on: November 25, 2021, 10:27:04 AM »
cant view the graphs ... that disappeared ....

I made a grand mistake during the movement of coordinate data and I have to completely redo the analysis. There is a completely different result. Not bad but different. The resulting Wortman modification isn't as good of performance as the initial results. It isn't a lost effort as I think the impact of adding flaps will compensate. The NACE section isn't well suited for large plate Gwinn style flaps, I don't think. It will take me a couple hours to repeat the analysis and it is Thanksgiving so it will be tomorrow.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #132 on: November 25, 2021, 11:04:56 AM »
cant view the graphs ... that disappeared ....

BTW, very nice way of building the wings. That's how I built my F1C models. Always consistent results. 
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Offline Air Ministry .

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 4312
Re: Blunt leading edge
« Reply #133 on: November 25, 2021, 08:54:07 PM »
EGAR .

If you put a line at 45 Deg. ea. way , intersecting the front at 45 deg.  %^@ you wouldnt miss much , or add much infill to fill the point in front .
A folded cardboard or styrene taped on for air tests'd prove something . One way or another .  VD~ Just dont deck it .



Looks like the C G'd be back amost near the 3rrd mark . 30% . BUT , Flaps'd make it about 2 wider , plus the bit where the backs cut so its not as wide . Unless the flaps are as thin as paper .
3/12ths then is 25 % . But we said ALMOST . so 22 or 23 % . Or 20 - 25 % . Fairly Normal . THOUGH any area FORWARD of the C.G.  , one would think , Is force Fwd of inertia , so enhances
the turn . Whereas if its aft its countering  it and is counter countered  :-X by the elevators . Unless its a Canard .

SORRY .

But we think the aftish high point may / can give more stable center of lift , resitance ( drag Cr. in turn ) and low adhesion .
The Folkerts uses a Werwage airfoil . Said to be a wind man . Larger version with rounded L E needed larger empenage ,
To get ' The Groove ' , and spo turns clean . Eliminate the corrections for track .
AIRFOIL .


Airfoil , Yellow one , pirated from here Via Xerox . Miller said He borrowed the Arees section . HOWEVER -> to The Eye its % percentages , poportionately , look comparable to yours .

As in ones say 10% ( of size ) fatter or thinnner , tho the entry - front - L E  might not be identical .

Is the assumption that the resistance at the front edge of a blunt nose section requires a C G more forward . TEST a foam or shaped thin to tack on fwd to evaluate turn & exit . With Std. (tail) weight variation .
say 4 or 5 ,
To find where it gets dull & where it gets snappy . General Parameters NOT fine tuning . As in , start 0 rear weight -> as there added if its gotten ugly you woulnt try for more ugly -> C G rear Max .  H^^

This had the thrift airfoil . Told the yatsenkos are set up hair trigger to turn . This'd handle a gale  . But flew daily NZ around 2002 , so the driver wasnt all dull & awkward . One learns to fly, in wind, in N Z .


 SNAARRRL.
The L E was just smoothed 1/2 or 3/8 Sq , on edge . As we said , It'd ROTATE on full handle , Triangle corners . No sink & exit clean ( for theconditions . one doest see EXACT laser acurateness . But Close )
The flow might break away , but still supported under . Woosh Noise ! . Still going Fwd so result is tight turn rather than changeing direction in three inchs .
Pity I didnt build it 76 or so , as planned . Will give a clean patter in smooth 20 - 30 knot . And flown in 40 . Not for amatures . A good combat pilot'd like it .
« Last Edit: November 25, 2021, 09:18:50 PM by Air Ministry . »

Online Howard Rush

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7465
Re: Blunt leading edge
« Reply #134 on: November 25, 2021, 11:29:34 PM »
Having said that, excel is the easiest way to do the coordinate task. Just take them massage.

When I had an issue with a Microsoft product I would go at lunchtime to an Indian restaurant near the Redmond campus and ask the cutest woman in the buffet line.  Mark takes this to a whole 'nother level.
The Jive Combat Team
Making combat and stunt great again

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #135 on: November 26, 2021, 06:32:08 AM »
When I had an issue with a Microsoft product I would go at lunchtime to an Indian restaurant near the Redmond campus and ask the cutest woman in the buffet line.  Mark takes this to a whole 'nother level.


"in deep foreign accent"....

Ha ha. You be funny man Mr Rush...


 <=
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #136 on: November 27, 2021, 10:20:10 AM »
So, I spent some time once again using lessons learned and made absolute certain that I had the correct profile loaded. I am struggling with the software crashing when I create the flat plate Gwinn flap. It probably my method of coordinate messaging, Mr Rush (deep foreign accent) and the curve fit is choking on the transition.  The other part of the Hanley's analysis software I have does multi surface analysis but it is not real easy to do a fast analysis with and it isn't coefficientized for individual elements. I have some ideas how to get around this divergence problem but they'll take some time to do.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood

Online Howard Rush

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7465
Re: Blunt leading edge
« Reply #137 on: November 27, 2021, 11:17:23 AM »
I have trouble with the flap on XFOIL, too. It doesnít like the dent between the wing and flap. I draw a straight line across the dent and Profili fairs it even more.
The Jive Combat Team
Making combat and stunt great again

Offline Serge_Krauss

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1334
Re: Blunt leading edge
« Reply #138 on: November 27, 2021, 02:20:54 PM »
When I entered the "stationary flapped" section, I did it with closely spaced coordinates. It printed that out as intended (its in my post on p. 2) and then processed with X-Foil.

SK

Online Mark wood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 434
  • I'm here purely for the fun of it.
Re: Blunt leading edge
« Reply #139 on: November 27, 2021, 04:59:37 PM »
Yeah I know. XFOIL handles that a little better but it isn't as good at mass comparison.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
The aerobatic airplane is a tool, a pencil, a paintbrush the artist uses to paint their aero art onto the tapestry air with. That art is the combined elements of figures drawn in space and time.  - M. Wood


Advertise Here
Tags:
 


Advertise Here