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sidsel.svein(at)oslo.onli
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 Posted: Mon Jul 01, 2013 6:22 am Post subject: SV: Re: wing lift/drag pins |
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This has been an interesting discussion, but it appears to me that it got off-track somewhere because "forward" has two meanings (see the attached illustrations):
<![if !supportLists]>(i) <![endif]>The LIFT does not have a “forward” component, under any circumstances, if FORWARD means the direction of the aircraft’s flight. Reason: LIFT is by definition always perpendicular to the direction of flight, as DRAG is always opposite to the direction of flight (i.e. perpendicular to the LIFT).
<![if !supportLists]>(ii) <![endif]>If, however, one refers to FORWARD as the direction of the aircrafts centerline, then LIFT has a “forward” component as soon as the centerline points up at the nose relative to the direction of flight. The higher the nose points up, the greater this forward component is. At some point it may, as I read the discussion, become larger than the wing DRAG’s component parallel to the centerline in the opposite direction, giving a net “forward” force on the wing.
<![if !supportLists]>(iii) <![endif]>The LIFT does not contribute, under any circumstances, to moving the aircraft forward through the air, as there is no lift component parallel to the direction of flight. A glider is “propelled” by the forward – in the direction of flight – component of the aircraft’s WEIGHT only.
Regards,
Svein
LN-SKJ
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frans(at)privatepilots.nl
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| Posted: Mon Jul 01, 2013 6:37 am Post subject: SV: Re: wing lift/drag pins |
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On 07/01/2013 04:21 PM, Sidsel & Svein Johnsen wrote:
| Quote: | This has been an interesting discussion, but it appears to me that it
got off-track somewhere because "forward" has two meanings (see the
attached illustrations):
|
How does an autogyro (autocopter?) work? What is causing the blades to
move forward?
| Quote: | A glider is
“propelled” by the forward – in the direction of flight – component of
the aircraft’s WEIGHT only.
|
Ok, got it. But without wings (but still with the majority of the
weight) will the glider still be propelled forwards? I guess not.
Then what exactly is exercising a forward pulling force on the glider's
fuselage? The fuselage has only drag. So something must be pulling it
forward.
Frans
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grahamsingleton(at)btinte
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| Posted: Mon Jul 01, 2013 6:53 am Post subject: SV: Re: wing lift/drag pins |
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Good point Svein
Graham
From: Sidsel & Svein Johnsen <sidsel.svein(at)oslo.online.no>
To: europa-list(at)matronics.com
Sent: Monday, 1 July 2013, 15:21
Subject: SV: Re: wing lift/drag pins
This has been an interesting discussion, but it appears to me that it got off-track somewhere because "forward" has two meanings (see the attached illustrations):
(i) The LIFT does not have a “forward” component, under any circumstances, if FORWARD means the direction of the aircraft’s flight. Reason: LIFT is by definition always perpendicular to the direction of flight, as DRAG is always opposite to the direction of flight (i.e. perpendicular to the LIFT).
(ii) If, however, one refers to FORWARD as the direction of the aircrafts centerline, then LIFT has a “forward” component as soon as the centerline points up at the nose relative to the direction of flight. The higher the nose points up, the greater this forward component is. At some point it may, as I read the discussion, become larger than the wing DRAG’s component parallel to the centerline in the opposite direction, giving a net “forward” force on the wing.
(iii) The LIFT does not contribute, under any circumstances, to moving the aircraft forward through the air, as there is no lift component parallel to the direction of flight. A glider is “propelled” by the forward – in the direction of flight – component of the aircraft’s WEIGHT only.
Regards,
Svein
LN-SKJ
[quote][b]
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sidsel.svein(at)oslo.onli
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| Posted: Mon Jul 01, 2013 10:23 pm Post subject: SV: Re: wing lift/drag pins |
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Ron,
From your message:
| Quote: | Attached is a diagram that is a pretty good visualization.
Ron P.
Here's his reply:
No it’s not… (a good visualization)
You have to apply real numbers to those phoney scalers on that figure.
At high AOA the drag is significantly higher than shown, but lift not so much
so. This would pull the L/D resultant much father aft.
Those two plots are implying that the L/D of a wing is the same at cruise and
at high AOA which we all KNOW is not true! (the reason you never fly a high
performance sailplane near Cl Max!)
|
I assume it was my illustration that you forwarded to your friend. If so, I agree with his statement about L/D  - the vectors are not to scale at all, and were not intended to be. I realize, however, that I should have emphasized this and also increased the length of the wing drag vector at the high AOA illustration, but this has no bearing on the lift component issue.
My message – and illustration - had two purposes, which perhaps your friend was not aware of:Â
<![if !supportLists]>- <![endif]>To show that lift has no component in the direction of flight, regardless of the angle of attack, while lift may have a “forward” component, if "forward" means the direction the nose is pointing. Â
<![if !supportLists]>- <![endif]>To show that a glider is pulled forward (in the direction of gliding flight) by gravity, not by any lift component.
I have not made any calculation of the magnitude of the “forward” lift component vs. drag on Europa or any other airplane, which is why I just referred to arguments and observations presented by others:  "At some point it may, as I read the discussion, become larger than the wing DRAG’s component parallel to the centerline in the opposite direction, giving a net “forward” force on the wing."  The magnitude of such a “forward” component is only dependent on the magnitude of the lift and the angle between the centerline and the direction of flight. The magnitude of drag does not come in here. The resultant force on the wing, however, and whether it acts “forward” or “backward”, depends also on the drag magnitude.
I apologize if I have caused any confusion about wing L/D vs. AOA (I don’t really think I have, though!)
Regards,
Svein
[quote][b]
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grahamsingleton(at)btinte
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| Posted: Tue Jul 02, 2013 4:21 am Post subject: SV: Re: wing lift/drag pins |
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Svein
I admire your patience and courtesy, the persistent deniers on this tread have
just about exhausted mine! First of all one should start with the facts; when a wing
fails due to high positive load it claps forwards. Saying "I don't believe it because it
doesn't fit my understanding or theory might be described as "an academic reaction to an inconvenient truth"
This "forward lift component" is very counter intuitive, the only way to approach it is to
refer to a diagram like yours. The criterion a lot of people overlook is that lift is
perpendicular to line of flight, which is NOT parallel with the centre line of the fuselage.
Nor is it 180deg from the line of gravity.
Graham
From: Sidsel & Svein Johnsen <sidsel.svein(at)oslo.online.no>
To: europa-list(at)matronics.com
Sent: Tuesday, 2 July 2013, 7:23
Subject: SV: Re: wing lift/drag pins
Ron,
From your message:
| Quote: | Attached is a diagram that is a pretty good visualization.
Ron P.
Here's his reply:
No it’s not… (a good visualization)
You have to apply real numbers to those phoney scalers on that figure.
At high AOA the drag is significantly higher than shown, but lift not so much
so. This would pull the L/D resultant much father aft.
Those two plots are implying that the L/D of a wing is the same at cruise and
at high AOA which we all KNOW is not true! (the reason you never fly a high
performance sailplane near Cl Max!)
|
I assume it was my illustration that you forwarded to your friend. If so, I agree with his statement about L/D - the vectors are not to scale at all, and were not intended to be. I realize, however, that I should have emphasized this and also increased the length of the wing drag vector at the high AOA illustration, but this has no bearing on the lift component issue.
My message – and illustration - had two purposes, which perhaps your friend was not aware of:
- To show that lift has no component in the direction of flight, regardless of the angle of attack, while lift may have a “forward” component, if "forward" means the direction the nose is pointing.
- To show that a glider is pulled forward (in the direction of gliding flight) by gravity, not by any lift component.
I have not made any calculation of the magnitude of the “forward” lift component vs. drag on Europa or any other airplane, which is why I just referred to arguments and observations presented by others: "At some point it may, as I read the discussion, become larger than the wing DRAG’s component parallel to the centerline in the opposite direction, giving a net “forward” force on the wing." The magnitude of such a “forward” component is only dependent on the magnitude of the lift and the angle between the centerline and the direction of flight. The magnitude of drag does not come in here. The resultant force on the wing, however, and whether it acts “forward” or “backward”, depends also on the drag magnitude.
I apologize if I have caused any confusion about wing L/D vs. AOA (I don’t really think I have, though!)
Regards,
Svein
| Quote: | http://www.matronics.com/Navigator?Europa-Listofollow" target="_blank" href="http://www.matronics.com/contribution">h
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peterz(at)zutrasoft.com
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| Posted: Tue Jul 02, 2013 5:55 am Post subject: SV: Re: wing lift/drag pins |
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Thx Graham,
My sentiments exactly.
And to the question of why the spars are strapped together, and why one pin has to be a pip pin, is because we have simple overlapping spars, and not fork spars, so the asymmetrical load on the pins wants to twist them off, as the spar ends gets forced away from the other spar.
Cheers,
Pete
On Jul 2, 2013, at 8:19 AM, GRAHAM SINGLETON <grahamsingleton(at)btinternet.com (grahamsingleton(at)btinternet.com)> wrote:
[quote]Svein
I admire your patience and courtesy, the persistent deniers on this tread have
just about exhausted mine! First of all one should start with the facts; when a wing
fails due to high positive load it claps forwards. Saying "I don't believe it because it
doesn't fit my understanding or theory might be described as "an academic reaction to an inconvenient truth"
This "forward lift component" is very counter intuitive, the only way to approach it is to
refer to a diagram like yours. The criterion a lot of people overlook is that lift is
perpendicular to line of flight, which is NOT parallel with the centre line of the fuselage.
Nor is it 180deg from the line of gravity.
Graham
From: Sidsel & Svein Johnsen <sidsel.svein(at)oslo.online.no (sidsel.svein(at)oslo.online.no)>
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Sent: Tuesday, 2 July 2013, 7:23
Subject: SV: Re: wing lift/drag pins
Ron,
From your message:
| Quote: | Attached is a diagram that is a pretty good visualization.
Ron P.
Here's his reply:
No it’s not… (a good visualization)
You have to apply real numbers to those phoney scalers on that figure.
At high AOA the drag is significantly higher than shown, but lift not so much
so. This would pull the L/D resultant much father aft.
Those two plots are implying that the L/D of a wing is the same at cruise and
at high AOA which we all KNOW is not true! (the reason you never fly a high
performance sailplane near Cl Max!)
|
I assume it was my illustration that you forwarded to your friend. If so, I agree with his statement about L/D - the vectors are not to scale at all, and were not intended to be. I realize, however, that I should have emphasized this and also increased the length of the wing drag vector at the high AOA illustration, but this has no bearing on the lift component issue.
My message – and illustration - had two purposes, which perhaps your friend was not aware of:
- To show that lift has no component in the direction of flight, regardless of the angle of attack, while lift may have a “forward” component, if "forward" means the direction the nose is pointing.
- To show that a glider is pulled forward (in the direction of gliding flight) by gravity, not by any lift component.
I have not made any calculation of the magnitude of the “forward” lift component vs. drag on Europa or any other airplane, which is why I just referred to arguments and observations presented by others: "At some point it may, as I read the discussion, become larger than the wing DRAG’s component parallel to the centerline in the opposite direction, giving a net “forward” force on the wing." The magnitude of such a “forward” component is only dependent on the magnitude of the lift and the angle between the centerline and the direction of flight. The magnitude of drag does not come in here. The resultant force on the wing, however, and whether it acts “forward” or “backward”, depends also on the drag magnitude.
I apologize if I have caused any confusion about wing L/D vs. AOA (I don’t really think I have, though!)
Regards,
Svein
[b]
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grahamsingleton(at)btinte
Guest
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| Posted: Tue Jul 02, 2013 6:00 am Post subject: SV: Re: wing lift/drag pins |
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Glad I didn't upset everyone {{!-)
Graham
From: Pete <peterz(at)zutrasoft.com>
To: "europa-list(at)matronics.com" <europa-list(at)matronics.com>
Sent: Tuesday, 2 July 2013, 14:54
Subject: Re: SV: Re: wing lift/drag pins
Thx Graham,
My sentiments exactly.
And to the question of why the spars are strapped together, and why one pin has to be a pip pin, is because we have simple overlapping spars, and not fork spars, so the asymmetrical load on the pins wants to twist them off, as the spar ends gets forced away from the other spar.
Cheers,
Pete
On Jul 2, 2013, at 8:19 AM, GRAHAM SINGLETON <grahamsingleton(at)btinternet.com (grahamsingleton(at)btinternet.com)> wrote:
[quote]Svein
I admire your patience and courtesy,
[b]
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wdaniell.longport(at)gmai
Guest
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| Posted: Wed Jul 03, 2013 4:46 am Post subject: SV: Re: wing lift/drag pins |
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This whole discussion has been fascinating. IMHO lot of the discussion is related to the difficulty of describing a three dimensional event in words (by the way I admire Frans’ and Svein’s grasp of English)
As I understand this and for the purposes of the discussion
Motive power is provided primarily from the fuselage in the form of
<![if !supportLists]>1. <![endif]>the engine when running
<![if !supportLists]>2. <![endif]>or in its absence the mass of the aircraft which is mostly concentrated in the fuselage being acted upon by the acceleration provided by gravity.
Drag affects the aircraft all over its surface but in level flight the wings are forced toward the rear of the aircraft by the relative wind acting upon the leading edge.
The wings provide the majority of the lift (a minimal being provided by the fuselage) in two ways but can only be created by forward motion with respect to the relative wind. (if the relative wind is zero then it wont fly)
<![if !supportLists]>1. <![endif]>benouille´s effect which is perpendicular to the cord
<![if !supportLists]>2. <![endif]>force of the relative wind against the lower surface of the wing. I am assuming that this varies in a complex way.
One can see the in level flight the mass of the aircraft is supported by the wings and this support is transmitted by the 4 points at which the wings connect to the fuselage. The force of the relative wind against the leading edge trying to fold the wings to the rear of the aircraft is being counteracted by the rear lift sockets and (I would also guess) by the main wing spars. So in this case the tie bar is in compression.
I have difficulty with visualizing how the tie bar could be in tension. I suppose that with the relative hitting the lower surface of the wing at a high angle of attack on could foresee a force component towards the front of the fuselage though not in the direction of flight but it seems hard. Maybe Rons engineer can try to explain it to us less technical folks.
I am continually surprised by what I learn on the forum.
Yours
Will
Bogota
From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of GRAHAM SINGLETON
Sent: Tuesday, July 02, 2013 09:01
To: europa-list(at)matronics.com
Subject: Re: SV: Re: wing lift/drag pins
Glad I didn't upset everyone {{!-)
Graham
From: Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)>
To: "europa-list(at)matronics.com (europa-list(at)matronics.com)" <europa-list(at)matronics.com (europa-list(at)matronics.com)>
Sent: Tuesday, 2 July 2013, 14:54
Subject: Re: SV: Re: wing lift/drag pins
Thx Graham,
My sentiments exactly.
And to the question of why the spars are strapped together, and why one pin has to be a pip pin, is because we have simple overlapping spars, and not fork spars, so the asymmetrical load on the pins wants to twist them off, as the spar ends gets forced away from the other spar.
Cheers,
Pete
On Jul 2, 2013, at 8:19 AM, GRAHAM SINGLETON <grahamsingleton(at)btinternet.com (grahamsingleton(at)btinternet.com)> wrote:
| Quote: |
Svein
I admire your patience and courtesy,
|
| Quote: | | http://www.matronics.com/Navigator?Europa-List |
0123456789
[quote][b]
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