Pylon mounted wings superior?

On Tuesday, February 11, 2014 11:56:19 AM UTC-6, Soartech wrote:
Wings with anhedral have been shown to be more efficient (L/D) than straight
wings. I can looks up the study if anyone needs to know more. This may be the
reason paragliders perform as well as they do despite large amounts of drag.

Please do. Might be amusing.

On Tuesday, February 11, 2014 12:15:43 PM UTC-6, wrote:
...Or possible it applies in some cases and not others.

Think you will find paragliders do have large drag, but such low speed as to make the horsepower consumed small. Think Paul MacCready and the Gossamer series of man powered planes. Most previous were cantilever, but he put wires out all over the place. Why? Lighter structure = lower flying speed = lower horsepower required. Horsepower is a cubic function of speed. Cut the flying speed in half, cut the horsepower to 1/8th. So you can afford a little higher drag if you knock the speed way down. Man powered flight is horespower limited. So is paraglider flight. They don't have to make much lift, and at low speed, all the risers don't make too much drag. Not much horsepower available from the low weight, either, so not much speed range.

On Tuesday, February 11, 2014 4:24:53 PM UTC-6, J. Nieuwenhuize wrote:
There are some other details at work; you gain lift, since now the wing is
actually lifting (no dip in the spanwise lift distribution anymore), so you
can actually shrink the wing area with a significant part of the wetted area increase.

Well, there is still a dip in the lift distribution. It is caused by the horizontal tail. If, of course, we are talking complete system, and not just wing. There is still a negative effect from the fuselage, but not NEARLY as big

On Tuesday, February 11, 2014 4:24:53 PM UTC-6, J. Nieuwenhuize wrote:
The pylon could be rather small, for a modern super-elliptic area
distribution (winglets), we now need a root chord of something like 24".
Given the fairly low forces on the pylon (save yaw, groundloop), the pylon
could be a lot smaller in chord and thickness.

The smaller you make the pylon and closer you get the load reacting points together, the higher the loads go. And, if you make the pylon too small, you lost all your volume for control connections. :-) Also, check the root chord on the AS-W27, V2, or even the Diana or Duckhawk. Think they are still 27 to 30 inches.

I also am not ready to buy into the need for anhedral for roll control if you have a pylon mounted wing. Weight of the wings, plus all the water carried in the wings, tends to make the fusleage and pilot a much smaller percentage of the mass of the flying machine. So, the center of mass is not starting as close to on the axis of the fuselage as you might think. What? The world doesn't revolve around the pilot? :-)

Good thoughts. Keep them coming.

Steve

Hey Steve,

The McDonnell XF-85 Goblin (
http://en.wikipedia.org/wiki/McDonnell_XF-85_Goblin ) had winglets *and*
anhedral (in the tail). Do you think it was much of a glider?

Coming to Moriarty this year?

"Steve Leonard" wrote in message
...
On Tuesday, February 11, 2014 11:56:19 AM UTC-6, Soartech wrote:
Wings with anhedral have been shown to be more efficient (L/D) than
straight
wings. I can looks up the study if anyone needs to know more. This may be
the
reason paragliders perform as well as they do despite large amounts of
drag.

Please do. Might be amusing.

On Tuesday, February 11, 2014 12:15:43 PM UTC-6,
wrote:
...Or possible it applies in some cases and not others.

Think you will find paragliders do have large drag, but such low speed as to
make the horsepower consumed small. Think Paul MacCready and the Gossamer
series of man powered planes. Most previous were cantilever, but he put
wires out all over the place. Why? Lighter structure = lower flying speed
= lower horsepower required. Horsepower is a cubic function of speed. Cut
the flying speed in half, cut the horsepower to 1/8th. So you can afford a
little higher drag if you knock the speed way down. Man powered flight is
horespower limited. So is paraglider flight. They don't have to make much
lift, and at low speed, all the risers don't make too much drag. Not much
horsepower available from the low weight, either, so not much speed range.

On Tuesday, February 11, 2014 4:24:53 PM UTC-6, J. Nieuwenhuize wrote:
There are some other details at work; you gain lift, since now the wing is
actually lifting (no dip in the spanwise lift distribution anymore), so
you
can actually shrink the wing area with a significant part of the wetted
area increase.

Well, there is still a dip in the lift distribution. It is caused by the
horizontal tail. If, of course, we are talking complete system, and not
just wing. There is still a negative effect from the fuselage, but not
NEARLY as big

On Tuesday, February 11, 2014 4:24:53 PM UTC-6, J. Nieuwenhuize wrote:
The pylon could be rather small, for a modern super-elliptic area
distribution (winglets), we now need a root chord of something like 24".
Given the fairly low forces on the pylon (save yaw, groundloop), the pylon
could be a lot smaller in chord and thickness.

The smaller you make the pylon and closer you get the load reacting points
together, the higher the loads go. And, if you make the pylon too small,
you lost all your volume for control connections. :-) Also, check the root
chord on the AS-W27, V2, or even the Diana or Duckhawk. Think they are
still 27 to 30 inches.

I also am not ready to buy into the need for anhedral for roll control if
you have a pylon mounted wing. Weight of the wings, plus all the water
carried in the wings, tends to make the fusleage and pilot a much smaller
percentage of the mass of the flying machine. So, the center of mass is not
starting as close to on the axis of the fuselage as you might think. What?
The world doesn't revolve around the pilot? :-)

Good thoughts. Keep them coming.

Steve

Op woensdag 12 februari 2014 01:12:40 UTC+1 schreef Steve Leonard:
On Tuesday, February 11, 2014 4:24:53 PM UTC-6, J. Nieuwenhuize wrote:
The pylon could be rather small, for a modern super-elliptic area
distribution (winglets), we now need a root chord of something like 24"..
Given the fairly low forces on the pylon (save yaw, groundloop), the pylon
could be a lot smaller in chord and thickness.

The smaller you make the pylon and closer you get the load reacting points together, the higher the loads go. And, if you make the pylon too small, you lost all your volume for control connections. :-) Also, check the root chord on the AS-W27, V2, or even the Diana or Duckhawk. Think they are still 27 to 30 inches.

I might have been too optimistic there with the root chord. Nevertheless I do expect the "next generation" to have narrower root chords, the modern super-elliptic planforms made possible by optimized winglets/polyhedral result in an almost untapered inner part of the wing.

I wouldn't worry too much about the loads on the pylon. Those are pretty small as compared to the wing. Packaging of the controls might be the major issue, though even there, there's some "unconquered terrain", see the Concordia control system. Having the flap/aileron mixer at the mid/outer wing joint could be a solution.


Here is some more in-depth discussion on pylon-mounted (sailplane) wings by the same author as your truly ;-)

http://www.homebuiltairplanes.com/fo...ylon-wing.html

The kicker here is the torsional load on the pylon from a ground
loop or possibly a spin plus recovery. Even if a carbon fibre
tube could approach the torsional rigidity/strength of a standard
fore/aft pin attachment in the fuselage, the structure needed
to distribute the pylon loads into the wing may be compicated.
But I am willing to be proved wrong.
John F

At 00:12 12 February 2014, Steve Leonard wrote:
On Tuesday, February 11, 2014 11:56:19 AM UTC-6, Soartech wrote:
Wings with anhedral have been shown to be more efficient (L/D) than
strai=
ght=20
wings. I can looks up the study if anyone needs to know more. This may
be=
the=20
reason paragliders perform as well as they do despite large amounts of
dr=
ag.

Please do. Might be amusing.

On Tuesday, February 11, 2014 12:15:43 PM UTC-6,
wrot=
e:
...Or possible it applies in some cases and not others.=20

Think you will find paragliders do have large drag, but such low speed as
t=
o make the horsepower consumed small. Think Paul MacCready and the
Gossame=
r series of man powered planes. Most previous were cantilever, but he
put
=
wires out all over the place. Why? Lighter structure =3D lower flying
spe=
ed =3D lower horsepower required. Horsepower is a cubic function of
speed.=
Cut the flying speed in half, cut the horsepower to 1/8th. So you can
af=
ford a little higher drag if you knock the speed way down. Man powered
fli=
ght is horespower limited. So is paraglider flight. They don't have to
ma=
ke much lift, and at low speed, all the risers don't make too much drag.
N=
ot much horsepower available from the low weight, either, so not much
speed=
range.

On Tuesday, February 11, 2014 4:24:53 PM UTC-6, J. Nieuwenhuize wrote:
There are some other details at work; you gain lift, since now the wing
i=
s=20
actually lifting (no dip in the spanwise lift distribution anymore), so
y=
ou=20
can actually shrink the wing area with a significant part of the wetted
a=
rea increase.

Well, there is still a dip in the lift distribution. It is caused by the
h=
orizontal tail. If, of course, we are talking complete system, and not
jus=
t wing. There is still a negative effect from the fuselage, but not
NEARLY=
as big

On Tuesday, February 11, 2014 4:24:53 PM UTC-6, J. Nieuwenhuize wrote:
The pylon could be rather small, for a modern super-elliptic area=20
distribution (winglets), we now need a root chord of something like
24".
Given the fairly low forces on the pylon (save yaw, groundloop), the
pylo=
n
could be a lot smaller in chord and thickness.

The smaller you make the pylon and closer you get the load reacting
points
=
together, the higher the loads go. And, if you make the pylon too small,
y=
ou lost all your volume for control connections. :-) Also, check the
root=
chord on the AS-W27, V2, or even the Diana or Duckhawk. Think they are
st=
ill 27 to 30 inches.

I also am not ready to buy into the need for anhedral for roll control if
y=
ou have a pylon mounted wing. Weight of the wings, plus all the water
carr=
ied in the wings, tends to make the fusleage and pilot a much smaller
perce=
ntage of the mass of the flying machine. So, the center of mass is not
sta=
rting as close to on the axis of the fuselage as you might think. What?
T=
he world doesn't revolve around the pilot? :-)

Good thoughts. Keep them coming.

Steve

Op zondag 16 februari 2014 18:16:26 UTC+1 schreef firsys:

The kicker here is the torsional load on the pylon from a ground
loop or possibly a spin plus recovery. Even if a carbon fibre
tube could approach the torsional rigidity/strength of a standard
fore/aft pin attachment in the fuselage, the structure needed
to distribute the pylon loads into the wing may be compicated.
But I am willing to be proved wrong.
John F


I doubt that's nearly as much of a factor as many think.

Ground loop loads, at least from the regulatory point are not that high. 400N, so about 70 kgf (155 lbsf) ultimate load at the extremity of tip, balanced by an opposite load on the tail wheel. (CS22-5?? from memory). Same for spin recovery loads; those are nowhere near as high as rudder deflection @ Va, which is likely the limiting load case for the pylon.

As for the wing structure; mounting the pylon in yaw is pretty trivial. You're simply loading the skin in pure shear, which is about the easiest connection possible. The pylon load and mounting it to the fuselage skin are the biggie, but nothing a few layers of carbon won't solve. Less certain about flutter, but then most of the modes that involve yaw have much lower inertia (sideways boom bending/torsion), 2-3 orders of magnitude less inertia as a fully ballasted wing.

Kingfisher and plncraze came up with this thesis on http://www.homebuiltairplanes.com/fo...ylon-wing.html

MANDATORY reading for anybody that thinks this is interesting. Not 1:1 applicable to full-scale sailplanes, but a most interesting read wrt pylon wings:
http://drum.lib.umd.edu/bitstream/19...i-umd-5315.pdf

Also this article by Johan Bosman has some interesting remarks about moving the wing up (article on the end of the page):
http://www.glidinginternational.com/...g_Stories.html

At the worlds in 2010, Prof Boermans gave an interesting talk on wing-fuselage drag, suggesting that moving the wing to the top of the fuselage -- not shoulder, and not pylon -- could reduce drag. An article in gliding international followed up with some analysis from Jonkers suggesting they are going to implement the idea at some point soon. Not pylons, but higher mounted wings may be on their way.

john cochrane