 |
AirTalk.org
Aviation discussions newsgroups
|
| View previous topic :: View next topic |
| Author |
Message |
Guest
|
 Posted: Mon Jul 31, 2006 4:19 pm Post subject: What arre luff lines ? |
 |
|
| Quote: | All modern gliders have built-in stall recovery mechanisms (such as
luff lines in kingposted gliders) and are designed and tested for as
much stability as possible, depending on the performance
characteristics desired.
|
== Chris Glur. |
|
| Back to top |
|
 |
Iwo Mergler
Guest
|
| Posted: Tue Aug 01, 2006 12:43 pm Post subject: Re: What arre luff lines ? |
|
|
news (AT) absamail (DOT) co.za wrote:
| Quote: | All modern gliders have built-in stall recovery mechanisms (such as
luff lines in kingposted gliders) and are designed and tested for as
What arre luff lines ?
|
This is my understanding of the luff lines:
Early hang gliders had the unpleasant behaviour of becoming
uncontrollable during a vertical dive. It accounted for the
majority of fatal accidents.
The wing relies on the pressure difference between top and
bottom to stay in shape and provide lift. In a steep dive,
this difference goes away and the wing just flutters in the
wind, like a flag.
The luff lines are lines attached between the kingpost and
the trailing edge of the wing. In normal flight, they are
slack.
In the mentioned vertical dive, the wing goes into flag mode,
but the luff lines now pull the trailing edge up. This acts
like an elevator which increases the angle of attack and gets
the wing flying again.
Kind regards,
Iwo |
|
| Back to top |
|
|
Guest
|
| Posted: Sat Aug 05, 2006 6:15 pm Post subject: Re: What arre luff lines ? |
|
|
In article <d9d3q3-88l.ln1 (AT) c2968 (DOT) soton.sc.philips.com>, Iwo Mergler <Iwo.Mergler (AT) soton (DOT) sc.philips.com> wrote:
| Quote: | news (AT) absamail (DOT) co.za wrote:
All modern gliders have built-in stall recovery mechanisms (such as
luff lines in kingposted gliders) and are designed and tested for as
What arre luff lines ?
This is my understanding of the luff lines:
Early hang gliders had the unpleasant behaviour of becoming
uncontrollable during a vertical dive. It accounted for the
majority of fatal accidents.
The wing relies on the pressure difference between top and
bottom to stay in shape and provide lift. In a steep dive,
this difference goes away and the wing just flutters in the
wind, like a flag.
The luff lines are lines attached between the kingpost and
the trailing edge of the wing. In normal flight, they are
slack.
In the mentioned vertical dive, the wing goes into flag mode,
but the luff lines now pull the trailing edge up. This acts
like an elevator which increases the angle of attack and gets
the wing flying again.
Kind regards,
Iwo
|
That makes sense, if the 'trailing edge pull up' occurs [by some
'deforming' of the structure] when ever the 'lift' is lost.
Which would mean also before initially reaching flying speed.
Which seems problematic, because it would tend to mean stall on
take off ?
Also the original quote "stall recovery mechanisms" suggests
the opposite of a dive recovery mechanism ?
Have we got any techie hang-gliders ?
Thanks,
== Chris Glur. |
|
| Back to top |
|
|
Iwo Mergler
Guest
|
| Posted: Mon Aug 07, 2006 1:06 pm Post subject: Re: What arre luff lines ? |
|
|
news (AT) absamail (DOT) co.za wrote:
| Quote: | In article <d9d3q3-88l.ln1 (AT) c2968 (DOT) soton.sc.philips.com>, Iwo Mergler
Iwo.Mergler (AT) soton (DOT) sc.philips.com> wrote:
news (AT) absamail (DOT) co.za wrote:
All modern gliders have built-in stall recovery mechanisms (such as
luff lines in kingposted gliders) and are designed and tested for
as
What arre luff lines ?
This is my understanding of the luff lines:
Early hang gliders had the unpleasant behaviour of becoming
uncontrollable during a vertical dive. It accounted for the
majority of fatal accidents.
The wing relies on the pressure difference between top and
bottom to stay in shape and provide lift. In a steep dive,
this difference goes away and the wing just flutters in the
wind, like a flag.
The luff lines are lines attached between the kingpost and
the trailing edge of the wing. In normal flight, they are
slack.
In the mentioned vertical dive, the wing goes into flag mode,
but the luff lines now pull the trailing edge up. This acts
like an elevator which increases the angle of attack and gets
the wing flying again.
Kind regards,
Iwo
That makes sense, if the 'trailing edge pull up' occurs [by some
'deforming' of the structure] when ever the 'lift' is lost.
To be more accurate, the luff lines just keep the trailing edge |
where it belongs, when the rest of the wing deforms 'downwards'.
Think of lift as a gradual thing. The wing only deforms when
there is not enough lift to keep the sailcloth in shape. It takes
a lot more lift to get the whole glider plus pilot flying.
| Quote: | Which would mean also before initially reaching flying speed.
|
The wing flies while the pilot runs. The transition is gradual.
| Quote: | Which seems problematic, because it would tend to mean stall on
take off ?
|
That is the art of take-off, getting from a stalled (non-flying)
wing to a flying one. For a more extreme example, consider
paragliders - there isn't even a wing until just before takeoff. ;-)
| Quote: | Also the original quote "stall recovery mechanisms" suggests
the opposite of a dive recovery mechanism ?
|
I assume that the wing will recover from the stall by entering
a dive. I'm not sure about this - I'm flying a paraglider and
get some hangliding lore by osmosis, on the hill. :-)
Regards,
Iwo
| Quote: |
Have we got any techie hang-gliders ?
Thanks,
== Chris Glur. |
|
|
| Back to top |
|
|
Randall
Guest
|
| Posted: Wed Aug 09, 2006 9:57 pm Post subject: Re: What arre luff lines ? |
|
|
Luff lines is a cross over from sailing. On a sailboat the luff of the
sail is the area close to the mast... which is the leading edge of the
sail/wing. By observing this area of the sail cloth you can tell the
efficiency of the sailing and trim to improve. Now place this on a wing
and you have angle of attack. In aailing you may hear the term "luff
the sail" that means to let out the Sheet to ease the sail out to dump
the wind. In hanggliding this is what would happen if the wing is put
in to steep a dive... The cloth at the leading edge of the wing would
begin to flutter like a flag. Recovery from a too fast dive to me would
be very touchy. As you are now trying to slow down a fast moving wing
by forcing the wing to a higher angle... done too much and the wing
structure can give or if the cloth is not in the best of shape it could
rip... Stalls on the other hand can be recovered as long as there is
sufficient altitude. Just by angling down the wing which increases the
speed and the aire over the wing you regain lift....
I think this about covers the subject...
Randy
Iwo Mergler wrote:
| Quote: | news (AT) absamail (DOT) co.za wrote:
In article <d9d3q3-88l.ln1 (AT) c2968 (DOT) soton.sc.philips.com>, Iwo Mergler
Iwo.Mergler (AT) soton (DOT) sc.philips.com> wrote:
news (AT) absamail (DOT) co.za wrote:
All modern gliders have built-in stall recovery mechanisms (such as
luff lines in kingposted gliders) and are designed and tested for
as
What arre luff lines ?
This is my understanding of the luff lines:
Early hang gliders had the unpleasant behaviour of becoming
uncontrollable during a vertical dive. It accounted for the
majority of fatal accidents.
The wing relies on the pressure difference between top and
bottom to stay in shape and provide lift. In a steep dive,
this difference goes away and the wing just flutters in the
wind, like a flag.
The luff lines are lines attached between the kingpost and
the trailing edge of the wing. In normal flight, they are
slack.
In the mentioned vertical dive, the wing goes into flag mode,
but the luff lines now pull the trailing edge up. This acts
like an elevator which increases the angle of attack and gets
the wing flying again.
Kind regards,
Iwo
That makes sense, if the 'trailing edge pull up' occurs [by some
'deforming' of the structure] when ever the 'lift' is lost.
To be more accurate, the luff lines just keep the trailing edge
where it belongs, when the rest of the wing deforms 'downwards'.
Think of lift as a gradual thing. The wing only deforms when
there is not enough lift to keep the sailcloth in shape. It takes
a lot more lift to get the whole glider plus pilot flying.
Which would mean also before initially reaching flying speed.
The wing flies while the pilot runs. The transition is gradual.
Which seems problematic, because it would tend to mean stall on
take off ?
That is the art of take-off, getting from a stalled (non-flying)
wing to a flying one. For a more extreme example, consider
paragliders - there isn't even a wing until just before takeoff. ;-)
Also the original quote "stall recovery mechanisms" suggests
the opposite of a dive recovery mechanism ?
I assume that the wing will recover from the stall by entering
a dive. I'm not sure about this - I'm flying a paraglider and
get some hangliding lore by osmosis, on the hill. :-)
Regards,
Iwo
Have we got any techie hang-gliders ?
Thanks,
== Chris Glur.
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
