RE: found this interesting discussion on Spiral Slipstream    Gallery
View related threads: (in this forum | in all forums)

Logged in as Guest



Users viewing this topic: none
    Search This Thread  
 
Printable Version

All Forums >> RC Airplanes >> Aerodynamics >> RE: found this interesting discussion on Spiral Slipstream
Page: <<   < prev  1 2 [3] 4   next >   >>  

Tower Hobbies Get Coupon Codes Brands  
Login
Message << Older Topic   Newer Topic >>
RE: found this interesting discussion on Spiral Slipstream - 10/3/2012 10:09 AM   
da Rock



Posts: 10888
Score: 265
Joined: 10/11/2005
Last Login: 5/25/2013
From: western, NC, USA
Status: offline
quote:

ORIGINAL: David Bathe

 Sometimes a picture's worth a thousand words.



Sometimes the pictures show what happens when a plane taxis around or is taking off while the humidity is high.

The tips are producing vapor trails. Happens all the time.

If there was truly a major "wind" created by those props, wouldn't you expect to see the "screw threads" showing a much larger "pitch"? Airflow that has power would also have airspeed. Those vapor trails are just hanging there. They basically just show where the tips were a very short time before the picture was taken.

There are a couple of things to notice in the picture of the Corsair taking off. That Corsair has some speed yet the vapor trails are still closely stacked. It really shows how fast the prop is rotating and how slowly the vapor trails are moving. Also, look closely at the direction the supposed slipstream looks like it's moving. They're interesting pictures for sure.

Attachments
Click to see fullsize image.
Click for fullsize


_____________________________

Good flying wit ya today

Hide Signatures

(in reply to David Bathe)
       Post #: 51

RE: found this interesting discussion on Spiral Slipstream - 10/3/2012 6:33 PM   
BMatthews



Posts: 11656
Score: 247
Joined: 10/4/2002
Last Login: 5/23/2013
From: Chilliwack, BC, CANADA
Status: offline 		In the picture of the Corsair keep in mind that the vapour trails for any given blade is every third or fourth trail. In between is the trails from the other blades depending on how many blades are up front.

Sadly I also tend to think that the vapour trails off the tips are not a good indicator of a spiralling slip stream. Since the prop tips are rotating while there is a rearward airflow from the speed of the plane and any headwind the tips would produce such a pattern with or without any actual spiral flow.

It is pretty easy to see the slipstream for one's self. Some thread "flow indicators" can be taped to a fuselage or mounted on small wire standoffs made from paper clips or copper wire and taped to a fuselage. Or even to a cross bar and the running prop blown over the threads.

I suspect that ideally it should be done with a fairly high pitch prop to see the angles well.

A prop might be lifting but it also has drag caused by both the lifting as well parasitic drag. And much like a motorized paint mixer or other paddle like stirring device the drag from the prop will cause some circular flow to the slip stream produced. As said already we don't need a math equation to see how that can happen.

I also suspect that the spiralling effect is tied closely to the pitch of the prop. Our models get away without the need for fin offset largely because we don't generate lots of torque and run with proportionally large props like the WWII fighter planes and other higher powered prop driven aircraft do. Or do we? Since we don't have to push with our leg against a rudder pedal could it be that a well trimmed model with the big gas engines ends up with a skosh of permanent right trim on the rudder? Hard to say as with our sizes the sort of difference that may be trimmed into such a model would be slight and could easily be taken for some misalignment during construction even on a high quality build. In effect the trim needed for OUR size and engines could be lost in the "noise" of other factors.

_____________________________

Witty saying to be plagarized shortly.....

Hide Signatures

(in reply to da Rock)
       Post #: 52

RE: found this interesting discussion on Spiral Slipstream - 10/3/2012 6:51 PM   
rmh



Posts: 12307
Score: 252
Joined: 12/12/2001
Last Login: 5/25/2013
From: , UT, USA
Status: offline 		The premise that the flow from the prop remains in a spiral path as it progresses over the model - is hard for me to accept
Too many variable to give it much credence -
That there is a twisting action from the prop - absolutely- simple reaction force. fin offset is about the only viable fix
offseting thrust - works for some types of models for others - it is just another built in offset which often requires opposing force inputs to hold it all in a line as we fly thru different attitudes..

_____________________________

Libby is still watching you

Hide Signatures

(in reply to BMatthews)
       Post #: 53

RE: found this interesting discussion on Spiral Slipstream - 10/3/2012 7:20 PM   
pimmnz


 

Posts: 1894
Score: 148
Joined: 11/9/2005
Last Login: 5/21/2013
From: Auckland, NEW ZEALAND
Status: offline 		The difficulty with a 'spiral flow' around a fuselage is simply this: It could work with a circular fuselage of smaller diameter than the prop, but most airplanes I know have wings...and fuselages with flat sides, often bigger than the prop...in order for any spiral flow to continue down a shape, there can't be any part of the flow that is redirected, say around a wing, or through a fuselage side...I remember AMI 'proving' spiral flow showing streamlines actually flowing through the wing X section...difficult in the real world as most wings are not permeable. And it (spiral flow) still does not explain why an airplane with the prop behind all of the structure still exhibits the same reactions as one with the prop at the front...Oh well, it's all just fun after all...
Evan, WB #12.

Hide Signatures

(in reply to rmh)
       Post #: 54

RE: found this interesting discussion on Spiral Slipstream - 10/4/2012 11:17 AM   
AA5BY


 

Posts: 1970
Score: 153
Joined: 9/7/2006
Last Login: 5/25/2013
From: White Oak, TX, USA
Status: offline 		Maybe in the Southern Hemisphere, they yaw right... eh.

Hide Signatures

(in reply to pimmnz)
       Post #: 55

RE: found this interesting discussion on Spiral Slipstream - 10/4/2012 2:53 PM   
da Rock



Posts: 10888
Score: 265
Joined: 10/11/2005
Last Login: 5/25/2013
From: western, NC, USA
Status: offline
quote:

ORIGINAL: AA5BY

Maybe in the Southern Hemisphere, they yaw right... eh.



They of course would be taking off inverted and that would counteract the direction of the flow.

_____________________________

Good flying wit ya today

Hide Signatures

(in reply to AA5BY)
       Post #: 56

RE: found this interesting discussion on Spiral Slipstream - 10/4/2012 5:48 PM   
MajorTomski



Posts: 2250
Score: 113
Joined: 5/1/2003
Last Login: 5/24/2013
From: Oklahoma City, OK, USA
Status: offline
quote:

ORIGINAL: banktoturn
That might not exist. You seem to think that if the ''mathematical proof'' doesn't exist, then the phenomenon doesn't occur. This isn't true; many engineering phenomena are well confirmed, yet don't benefit from such a tidy mathematical description. Bummer.

banktoturn


One can achieve the same yawing effect by having the airflow down the right side of the fuselage and fin flow faster than the air flowing down the left side of the fuse. and fin.

And at no time does the air need to spiral around the fuselage.

Which by the way is how the thrust comes off the prop due stricly to high AOA P-factor.



_____________________________

Spitfire Brotherhood #6
Kadet LT 40 Brotherhood #98

Hide Signatures

(in reply to banktoturn)
       Post #: 57

RE: found this interesting discussion on Spiral Slipstream - 10/6/2012 4:54 AM   
banktoturn



Posts: 762
Score: 105
Joined: 8/22/2002
Last Login: 5/3/2013
From: Bloomington, MN,
Status: offline
quote:

ORIGINAL: MajorTomski


quote:

ORIGINAL: banktoturn
That might not exist. You seem to think that if the ''mathematical proof'' doesn't exist, then the phenomenon doesn't occur. This isn't true; many engineering phenomena are well confirmed, yet don't benefit from such a tidy mathematical description. Bummer.

banktoturn


One can achieve the same yawing effect by having the airflow down the right side of the fuselage and fin flow faster than the air flowing down the left side of the fuse. and fin.

And at no time does the air need to spiral around the fuselage.

Which by the way is how the thrust comes off the prop due stricly to high AOA P-factor.




Really? You can get that kind of velocity differential from right to left just due to the P-factor? Do you have a mathematical proof or set of equations describing that phenomenon? How about just an authoritative web site that refers to it? I'd love to see any of these.

banktoturn

Hide Signatures

(in reply to MajorTomski)
       Post #: 58

RE: found this interesting discussion on Spiral Slipstream - 10/8/2012 10:23 PM   
MajorTomski



Posts: 2250
Score: 113
Joined: 5/1/2003
Last Login: 5/24/2013
From: Oklahoma City, OK, USA
Status: offline
quote:

Really? You can get that kind of velocity differential from right to left just due to the P-factor? Do you have a mathematical proof or set of equations describing that phenomenon? How about just an authoritative web site that refers to it? I'd love to see any of these.

banktoturn


Nope, just know that it took everybit of a locked right leg and a full rightrudder to get my STOL equipped C-182 to fly straight attempting to demonstrate a power on stall for my BFR. Couldn't find a CFI that could do it either.

You missed and continue to miss my original point. Please stop attacking me and prove my opinion wrong. Again the spiraling slipstream did not exist in aviation manuals prior to being popularized in Stick and Rudder. That book even goes as far to make up "facts" when it explains why after the power on stall the turning phenomina stops. All imperical, no number, no data.

Another myth is that spiraling slipstream yaw is minimized by twin engined airplanes that have dual fins & rudders. Except for the minor detail if you look at B-25's, Me-110's, Beech 18's etc most of them have their fins and rudders where the supposed spiraling slipstream would double the effect, not make it go away.

I've been hunting for one equation, or one simple photograph proving that the propwash spirals around the fuselage since 1988.

Please stop attacking me and solve the problem. Thank you

< Message edited by MajorTomski -- 10/10/2012 3:35 PM >

_____________________________

Spitfire Brotherhood #6
Kadet LT 40 Brotherhood #98

Hide Signatures

(in reply to banktoturn)
       Post #: 59

RE: found this interesting discussion on Spiral Slipstream - 10/8/2012 11:46 PM   
acerc



Posts: 3091
Score: 221
Joined: 9/7/2006
Last Login: 5/25/2013
From: lithia, FL, USA
Status: offline 		I don't know what you all are talking about. But I believe the photo toward's the top of this page is an optical illusion. Seem's to me those are the white tip's going at a rate of rotation along with the forward momentum of the plane to give an optical effect of the spiral. I can creat this same image with any modern camera with ease. Of course I could be dumb as an ox as well.


_____________________________

Robert
Cub Brotherhood #3\ Ryan STA Brotherhood #4

Hide Signatures

(in reply to MajorTomski)
       Post #: 60

RE: found this interesting discussion on Spiral Slipstream - 10/9/2012 12:24 AM   
da Rock



Posts: 10888
Score: 265
Joined: 10/11/2005
Last Login: 5/25/2013
From: western, NC, USA
Status: offline
quote:

ORIGINAL: acerc

I don't know what you all are talking about. But I believe the photo toward's the top of this page is an optical illusion. Seem's to me those are the white tip's going at a rate of rotation along with the forward momentum of the plane to give an optical effect of the spiral. I can creat this same image with any modern camera with ease. Of course I could be dumb as an ox as well.


Well, the pictures really aren't optical illusions, or pictorial illusions. They are pictures of contrails (condensation trails) and if you look where they are near the wing or struts in pictures of airplanes that have those areas in the pictures, you can see where the trails have been moved aside or moved anywhere something else moved them.

You aren't dumb as an ox, at least concerning that idea. Lot's of people immediately jumped to the conclusion it was spiral slipstream. They weren't right, but aren't oxen either.

Guys who've worked flight decks and airport ramps through different types of weather noticed the contrails off turning props were a weather phenomenon. Dew points and humidity levels helped make 'em. And they seemed to vanish on their own just like contrails do. Sometimes they're long. Sometimes they're not. And they don't blast aft. They mostly hang where they are made until they decide to recombine their water into the air, where it came from.

I believe if you look closely at the Corsair picture (hope that's one in this thread) at one or two of the curls that're right down in the starboard gull you'll notice the ends are being drawn almost at right angles away from where the prop blast would be going.

_____________________________

Good flying wit ya today

Hide Signatures

(in reply to acerc)
       Post #: 61

RE: found this interesting discussion on Spiral Slipstream - 10/9/2012 1:14 AM   
acerc



Posts: 3091
Score: 221
Joined: 9/7/2006
Last Login: 5/25/2013
From: lithia, FL, USA
Status: offline 		da Rock thank's for that explanation. Use to deal with boat motor's in test tank's and seen many of what you describe there with air being the displacement factor.


_____________________________

Robert
Cub Brotherhood #3\ Ryan STA Brotherhood #4

Hide Signatures

(in reply to da Rock)
       Post #: 62

RE: found this interesting discussion on Spiral Slipstream - 10/9/2012 2:13 AM   
AA5BY


 

Posts: 1970
Score: 153
Joined: 9/7/2006
Last Login: 5/25/2013
From: White Oak, TX, USA
Status: offline 		Interesting thought about boat comparison. Boaters describe prop walk as the condition that thrust a boat laterally (stern yaw) when there is little in the way of forward or reverse speed. Rotating the prop clockwise produces a starboard walk and reversing produces a port walk. The condition applies to a inboards with prop shafts where the prop lies under the boat. On outboards where the prop lies aft of the hull, there is little noticeable walk.

The walk is caused by pressure differences created by the asymmetry of the zone around the prop as the prop interacts with the hull bottom with the ascending blade toward the hull bottom producing a zone of higher pressure than exist on the descending away from the hull bottom side. Prop walk is very pronounced and predictable and used as a tool by experienced boaters to position a boat in a slip or to a pier.

Boats and planes have much in common such as the use of a propeller. Prop walk is notable when the boat has minimal speed and IMO has a corollary with airplane left yaw. The cause of the walk has been ascribed to many things such as P-factor of an angled prop shaft but it is my opinion that differing asymmetrical structure in the influence zone of the prop causes differing pressure zones and that as always, higher pressure moves towards lower pressure.

IMO, the P-factor is falsely ascribed to explain why an angled prop shaft causes more distinct walk to one direction, which is to port when in reverse. More likely to me is that simply put, the angled shaft directs prop wash closer to the hull bottom when in reverse than it does when in forward and the closer the wash is to the hull bottom, the greater the variance of pressure between the two sides. Again... P-factor IMO doesn't exist unless there is forward movement to define an angle of attack.

Yep... I'm still arguing that left airplane yaw is more that the fore section is yawing to port than the tail section is yawing to starboard.

Hide Signatures

(in reply to acerc)
       Post #: 63

RE: found this interesting discussion on Spiral Slipstream - 10/9/2012 9:13 AM   
David Bathe



Posts: 1127
Score: 105
Joined: 3/18/2008
Last Login: 5/25/2013
From: Oslo, NORWAY
Status: offline
quote:

ORIGINAL: AA5BY

Yep... I'm still arguing that left airplane yaw is more that the fore section is yawing to port than the tail section is yawing to starboard.


But that wouldn't explain why an airplane without any form of compensation (right thrust or rudder mix etc) that veers left when you pull to vertical, veers right when you push to vertical.
The difference being the fin position... upright for the pull and down for the push.
We still can't rule out the ol' fin.
Bugger.

Could it be more of a case of the aircraft fuselage flying into a spinning vortex of air created by the prop tip thus effecting the fin... instead of a fixed spirelling slip stream?


_____________________________

Best Regards: davidbathe.com
Occasional Aircraft Illustrations.

Hide Signatures

(in reply to AA5BY)
       Post #: 64

RE: found this interesting discussion on Spiral Slipstream - 10/9/2012 12:51 PM   
AA5BY


 

Posts: 1970
Score: 153
Joined: 9/7/2006
Last Login: 5/25/2013
From: White Oak, TX, USA
Status: offline
quote:

ORIGINAL: David Bathe


quote:

ORIGINAL: AA5BY

Yep... I'm still arguing that left airplane yaw is more that the fore section is yawing to port than the tail section is yawing to starboard.


But that wouldn't explain why an airplane without any form of compensation (right thrust or rudder mix etc) that veers left when you pull to vertical, veers right when you push to vertical.
The difference being the fin position... upright for the pull and down for the push.
We still can't rule out the ol' fin.
Bugger.

Could it be more of a case of the aircraft fuselage flying into a spinning vortex of air created by the prop tip thus effecting the fin... instead of a fixed spirelling slip stream?


I'm not sure if you mean relative to the ground pilot or the plane. If relative to the ground, looking at the gear, a plane veering right is veering left.

If you are saying that looking at the gear, the plane veers left so that it is actually veering right... I can't recall ever making that observation but will look for it.

Hide Signatures

(in reply to David Bathe)
       Post #: 65

RE: found this interesting discussion on Spiral Slipstream - 10/9/2012 2:59 PM   
da Rock



Posts: 10888
Score: 265
Joined: 10/11/2005
Last Login: 5/25/2013
From: western, NC, USA
Status: offline 		Keep in mind that gyroscopic precession rears it's ugly head much the same way p-effect does. Both show up when the nose is yawed or pitched. Ultimately, we really shouldn't focus on one as if the other didn't exist.

It's also good that someone has mentioned something other than pitch up.

_____________________________

Good flying wit ya today

Hide Signatures

(in reply to AA5BY)
       Post #: 66

RE: found this interesting discussion on Spiral Slipstream - 10/9/2012 3:16 PM   
David Bathe



Posts: 1127
Score: 105
Joined: 3/18/2008
Last Login: 5/25/2013
From: Oslo, NORWAY
Status: offline 		Well exactly, the left yaw in question, (if not compensated for with right thrust or rudder mix etc) is most evident when you pull to vertical from normal horizontal flight.
In pattern we're drawing enormous vertical lines compared with all types of normal sports/scale flying so we work a great deal on having our planes trimmed/balanced perfectly... alot more than normal.
As mentioned in an earlier post, I changed the prop on a perfectly trimmed 2m F3A plane some years ago which resulted in a noticably yaw left when pulled to vertical. It also showed a noticable yaw to right when pushed to vertical.
The prop was still going in the same direction... only the fin was now inverted.

If the yaw was down to some prop/angle/high pressure voodoo... wouldn't it drift left during all positive pulls and pushes?



_____________________________

Best Regards: davidbathe.com
Occasional Aircraft Illustrations.

Hide Signatures

(in reply to da Rock)
       Post #: 67

RE: found this interesting discussion on Spiral Slipstream - 10/9/2012 3:27 PM   
AA5BY


 

Posts: 1970
Score: 153
Joined: 9/7/2006
Last Login: 5/25/2013
From: White Oak, TX, USA
Status: offline 		I'd remind that the symmetry of the fore section is reversing between pulling to vertical and pushing to vertical so it is not just the fin that is reversed.

Hide Signatures

(in reply to David Bathe)
       Post #: 68

RE: found this interesting discussion on Spiral Slipstream - 10/9/2012 3:38 PM   
AA5BY


 

Posts: 1970
Score: 153
Joined: 9/7/2006
Last Login: 5/25/2013
From: White Oak, TX, USA
Status: offline 		A prop change could understandably affect yaw according to my theory of forward pressure variances. A high pitch prop doesn't get adequate bite when a plane slows so its efficiency as an air compressor is reduced so the pressures aft of the prop will be reduced as the plane slows in a vertical climb.

Hide Signatures

(in reply to AA5BY)
       Post #: 69

RE: found this interesting discussion on Spiral Slipstream - 10/9/2012 5:02 PM   
David Bathe



Posts: 1127
Score: 105
Joined: 3/18/2008
Last Login: 5/25/2013
From: Oslo, NORWAY
Status: offline

quote:

ORIGINAL: AA5BY

I'd remind that the symmetry of the fore section is reversing between pulling to vertical and pushing to vertical so it is not just the fin that is reversed.


Well yes, but I'm talking about the unlimited vertical our pattern models have.
In my case the yaw left or (right from inverted) didn't become noticable untill 50 - 75m clean vertical AFTER the pull up.
Unacceptable for the usage.
We need accelleated, hands-off unlimited straight line vertical.



_____________________________

Best Regards: davidbathe.com
Occasional Aircraft Illustrations.

Hide Signatures

(in reply to AA5BY)
       Post #: 70

RE: found this interesting discussion on Spiral Slipstream - 10/9/2012 6:43 PM   
MTK



Posts: 4003
Score: 203
Joined: 5/14/2004
Last Login: 5/25/2013
From: Whippany, NJ, USA
Status: online
quote:

ORIGINAL: rhall999

quote:

Guys for the spiral to be true the propeller has to induce airflow in the same direction as the rotation of the propeller.

If you watch the video again, you can see the direction of rotation right at the start of the video.  I admit, it is hard to tell with the bubbles, but sure looks to be the same direction to me.

This is the same as saying, if we place a probe somewhere below and aft of the trailing edge of a wing, we will find air moving in the same direction as the airplane. Never heard that one taught either.

Can't say as though I have ever seen evidence of that in any wind tunnel tests either....but I could be wrong.  There definately is some "forward" moving air below and aft of the LEADING edge.

As to the exhaust bubles from the prop. still not proof the bubbles are acually spiralling in the prop's wake.

Really???  Do you honestly think that there is something else there that is causing the bubble to spiral, and what would such a thing be??  The boat is barely moving, and you can sort of see the flow pattern off the back of the boat hull by watching the seaweed stuck to the bottom, and other floating particles in th water.


See my comments above in red.  I hate to be rude Major, but it seems to me as though you are grasping at straws now, trying desperately to cling to your theory  Just kidding, I know how hard it can be to accept things sometimes when your brain is certain of something else, I can be pretty stubborn myself sometimes!!!!!!

Same prop experiment...wish there was a way to show the bubbles with prop stopped and then with prop spinning in a continuous sequence. It would prove that NOT rotating that much mass (water mass in that case), the bubbles don't rotate....


_____________________________

Regards,
MattK

Hide Signatures

(in reply to rhall999)
       Post #: 71

RE: found this interesting discussion on Spiral Slipstream - 10/9/2012 6:56 PM   
MTK



Posts: 4003
Score: 203
Joined: 5/14/2004
Last Login: 5/25/2013
From: Whippany, NJ, USA
Status: online
quote:

ORIGINAL: da Rock

quote:

ORIGINAL: David Bathe

 Sometimes a picture's worth a thousand words.



Sometimes the pictures show what happens when a plane taxis around or is taking off while the humidity is high.

The tips are producing vapor trails. Happens all the time.

If there was truly a major "wind" created by those props, wouldn't you expect to see the "screw threads" showing a much larger "pitch"? Airflow that has power would also have airspeed. Those vapor trails are just hanging there. They basically just show where the tips were a very short time before the picture was taken.

There are a couple of things to notice in the picture of the Corsair taking off. That Corsair has some speed yet the vapor trails are still closely stacked. It really shows how fast the prop is rotating and how slowly the vapor trails are moving. Also, look closely at the direction the supposed slipstream looks like it's moving. They're interesting pictures for sure.

I've never seen this phenomenon before. Very cool and interesting that vapor condensation induced by a prop manifests this way, at the prop tips where vortices exist. I have seen a similar condensation of vapor many times at air shows where the whole plane makes a sharp pitch or sharp turn. Either of those flight conditions load the wing considerably requiring greater pressure differential to provide the necessary lift, hence vapor condensation occurs near the wingtips


_____________________________

Regards,
MattK

Hide Signatures

(in reply to da Rock)
       Post #: 72

RE: found this interesting discussion on Spiral Slipstream - 10/11/2012 1:28 PM   
AA5BY


 

Posts: 1970
Score: 153
Joined: 9/7/2006
Last Login: 5/25/2013
From: White Oak, TX, USA
Status: offline 		I flew my 72" Yak Tuesday and was careful to note yaw tendencies. It has none in both steep vertical or straight up, which verified what I thought I recalled. The Yak has a symmetrical fore section and has no engine right thrust. IIRC, it weighs just under 11 lbs and is powered by a 28cc engine.

Why doesn't the Yak yaw? It certainly has a lot of vertical fin with very little of it sub fin. On the other hand, I've an Akrobat II (somewhat similar to a Laser) that has as much fin as the Yak but differs greatly from the Yak in that it has a very asymmetric fore section. The engine center line is high in the cowl with the cowl then offering air intake below the spinner and then sweeping aft to the gear strut from below the air intake. That plane requires considerable rudder to correct left yaw on vertical and it has three degrees right thrust engine offset.

I'd suggest comparing ones planes and noting the forward symmetry. Do symmetrical fore sections suffer less yaw than do asymmetrical fore sections? If yes, I think we've been blaming the wrong end of the airplane for the left yaw when going vertical.

Offered is a pic of an original design also having a fairly symmetrical fore section. It suffers very little yaw when going vertical.





Attachments
Click to see fullsize image.
Click for fullsize


Hide Signatures

(in reply to David Bathe)
       Post #: 73

RE: found this interesting discussion on Spiral Slipstream - 10/11/2012 4:46 PM   
David Bathe



Posts: 1127
Score: 105
Joined: 3/18/2008
Last Login: 5/25/2013
From: Oslo, NORWAY
Status: offline
I just don't know why the Yak may exhibit that behaviour.
No front powered plane of mind, regardless of shape has ever flow straight without some right thrust, or rudder mix.
Try a radically different prop on the Yak, (dia/pitch not brand) as an experiment.
Try driving the vertical twice as far. 
Is there any rudder trim dialed in?
Is there any aileron trim dial in/ are the wings balanced?
Is the fin off set, is there any right thrust built in without you really noticing it?
What ever, if it fly's straight.... congratulations.


_____________________________

Best Regards: davidbathe.com
Occasional Aircraft Illustrations.

Hide Signatures

(in reply to AA5BY)
       Post #: 74

RE: found this interesting discussion on Spiral Slipstream - 10/11/2012 10:04 PM   
rmh



Posts: 12307
Score: 252
Joined: 12/12/2001
Last Login: 5/25/2013
From: , UT, USA
Status: offline 		After years of precision pattern (F3A) and IMAC in all sizes - it isapparant that the prop twisting its way thru the air - requires an offset - when power is cut on downlines - a roll going the other way -always occurs - both are, in my book very minor problems No matter which design plane is being flown - the same effect shows. - which leads me to believe this "spiral Flow " is really not a culprit the reaction to the prop producing thrust seems to be the real reason for any offsets . A truly hands of plane is a PITA -I like a wee bit of stability - don't like to chase a model to stay on line.

_____________________________

Libby is still watching you

Hide Signatures

(in reply to David Bathe)
       Post #: 75

Page:   <<   < prev  1 2 [3] 4   next >   >>  
All Forums >> RC Airplanes >> Aerodynamics >> RE: found this interesting discussion on Spiral Slipstream
Page: <<   < prev  1 2 [3] 4   next >   >>  




Jump to:


 
Google 



Search | Marketplace | Event Calendar | Local Clubs | Magazine | Product Ratings | New Products | Discussion Forums

Photo Gallery | Instructor Search | Field|Track|Marina Search

Advertisers | Hobby Vendor Resources | Rate Manufacturers | Sign In/Sign Up

SITE MAP!   : :   FORUM RULES

RC Universe is a service of Internet Brands, Inc. Copyright © 2001-2013.

Charities we support that also need your help
Yorkie Rescue | Humane Society | ASPCA | Crohn's-Colitis America


0.922RCU1