Pylon mounted wings superior?

Wouldn't it be simpler just to get rid of the fuselage and put the cockpit and pilot in the wing?

On Friday, February 7, 2014 12:03:40 AM UTC-5, Mike the Strike wrote:
Wouldn't it be simpler just to get rid of the fuselage and put the cockpit and pilot in the wing?

Now you're talking like the Horten Brothers. It works, but because of the washout required, it's not quite as efficient.

http://www.twitt.org/Hoiv-03.jpg

Op vrijdag 7 februari 2014 05:06:49 UTC+1 schreef Steve Leonard:
On Thursday, February 6, 2014 2:49:37 PM UTC-6, J. Nieuwenhuize wrote:

Giving up things like automatic connections would be down right stupid. What I'm proposing is something like the V2/ASG29.



So, how big a span on that center section are you proposing? Roughly the same as the inner sections on a V2C/ASG29 assembled? That would be one pretty heavy wing section!

That'd probably too large. Not so much for weight I'd think, taking out the spar stubs and all the other parts at the joint saves a lot of weight, but for trailerability. Something around 8 meters would make it fit in any trailer and also be around the optimal span for the flaps, avoiding complexity further.

Once you move the wing up to a pylon and join the inner halves, there's a

large reduction in parts. 4 less half root ribs, 2 less shear web fillers, 4 less spar bolt inserts, 2 controls less (only one for flap, one for

spoilers), one spoiler less, two push-pull tubes for the spoilers less, more room for a mixer and on and on.

So, you are proposing a single spoiler panel that extends a couple of feet either side of centerline? Keep in mind that the flaps move as ailerons on those planes, so if you go to one flap pushrod going into the center section, you will force the aileron mixers into the wing.

Yep, one spoiler. Or just do away with spoilers all together and have a "crow feet" approach (flaps down, ailerons up). That only works with very narrow chords though, due to the actuation forces and requires a mixer as complex as Waibel's latest achievement.
Not sure whether flaps moving with aileron function add much in roll moment, so we could just as well ditch that and bank the simplification.

And since you are doing that, you might as well just go with one aileron input into the center wing. That is how many three piece wing ships do it. As to the reduction in number of parts, you will have the ability to use fewer pushrods, but I am not so sure you will be able to do away with all the ribs and things to attach the wing to the fuselage (pins in the root ribs and spar bolt inserts are now replaced with fittings to attach the center section to the pylon, ribs for control bellcranks, etc). And if I am understanding your location for the spoiler, you are going to lose a LOT of room where those connections are going on.

You can use the space below the wing for the automatic connections (buried in the pylon once assembled), but packaging would certainly be a challenge.

One of the more interesting features of a pylon wing is in fact it's

(potential for) practicality. Do away with the one-men rigging aids and put a spring-loaded joint on the pylon. Pull the middle wing from the trailer while the other tip is still in it's dolly, cant horizontal and put it on the

spring-loaded receptor. No need to have a one-man rigging aid if your glider has it built-in. Vary required tip lifting by moving the wing dolly inboard a bit.

You lost me on the spring loaded joint on the pylon. Also, depending on how long the center wing panel is, you may have to roll the fuselage a LOT further back so that when you get the center section out so the far tip is at the back of the trailer, the middle of it is now along side the pylon. And, since you have a pylon sticking up above the fuselage, you will now have to lift that center wing panel 5-6 feet into the air to get it over the fuselage.

The mid-wing would have a vertical hole in the bottom and the pylon a small pin sticking upwards, which has 20 or so degrees freedom to cant fwd/aft. The pin is spring-loaded, such that when you put enough force on it, it'll sink in the pylon. Have the wing dolly on one side such that you can cant the chord from vertical to horizontal. Pull out the wing, cant it horizontal, position mid wing above the pylon and let it rest on the pin. Disconnect wing dolly, rotate wing to spanwise, pull down at the center and lock the lifting pins.

An alternative is to mount the outer panels like the S10 folding system and hang the 3 assembled panels from the roof of the trailer. Save a mechanical/electric roof lift and some reinforcements, it solves all the usual issues of assembling a sailplane and you have the potential to put the sailplane on a dolly and fold the wing without any external tools or help for an overnight in a hangar.

The interesting thing about the pylon-mounted wing is that nobody I discussed it with (including some involved in last-generation factory ships) actually

disliked the idea that it had potential in the end. Especially for monocoque wings (like the Diana), there's a lot to be gained.

There have been many advances in understanding aerodynamics since that experimental Std Cirrus with the pylon mounted wing. Maybe there is a performance benefit to be had? But with the biggest emphasis seeming to be reduction of the wetted area for whatever class is being worked, I am doubtful that adding the wetted area of a pylon of the required height to reduce the wing root interference drag is the road to performance improvements.

It's mostly about improving the extent of laminar flow on both the wing and the fuselage. There's a huge area of turbulent flow there, which (at least in theory) could be turned laminar. Bosman spoke about sucking off the LE of the wing/fuselage section, but just taking wing and fuselage apart could yield 1-2 sqm of flow that's laminar instead of turbulent.

Just my thoughts.
Thanks for sharing. Some interesting points.

On Saturday, February 8, 2014 6:09:11 AM UTC-6, J. Nieuwenhuize wrote:
It's mostly about improving the extent of laminar flow on both the wing and the fuselage. There's a huge area of turbulent flow there, which (at least in
theory) could be turned laminar. Bosman spoke about sucking off the LE of the
wing/fuselage section, but just taking wing and fuselage apart could yield 1-2 sqm of flow that's laminar instead of turbulent.
Thanks for sharing. Some interesting points.

But, to get those "1-2 sqm" of turbulent flow converted to laminar, you added almost that much area exposed to the flow. Some of which is still turbulent. Roughly 5 square feet of wing that was "hidden" in the fuselage is now exposed to air flow (2 feet spanwise, 30 inch chord). And, you have added a pylon that is something on the order of 24 to 30 inches tall, and probably more than 30 inches in chord. So, at best, another 5 square feet of wetted area of pylon. Probably more, because aerodynamically, you don't want max pylon width at the same chordwise location as max thickness on the wing.

Even if you can do it with a shorter pylon, it is still going to be difficult to get lower total drag with greater wetted area.

Steve

K

A wing 3 ft above the CG will give excessive roll stability; to
get an acceptable roll rate there will have to be substantial
anhedral. It will be at least look peculiar but there may be
other detractions.
I do not remember if the Slingsby T 21 was too stable
but that might be an attraction in a trainer.

John F



At 21:17 05 February 2014, Bob Kuykendall wrote:
From the perspective of an inveterate pragmatist:

I think it comes down to operationality. Yes, the autoconnects add
complexi=
ty. Yes, placing the wing panel separation at the station of maximum
bendin=
g moment adds weight.=20

But what you get in return is a system of parts that allows for easy
storag=
e and transport, rapid assembly, and high reliability. That system has
been=
proven to result in good soaring performance at the lowest possible cost
i=
n terms of operator fatigue. And that makes for a more enjoyable soaring
ex=
perience. And when it comes down to it, quality of experience is what we
sh=
ould be trying to maximize here, not necessarily quality of performance.

It is easy to conceive of this or that adaptation that might result in
grea=
ter performance for a no-holds-barred competition machine. However, all
too=
often the result is a less robust machine that requires more work to
assem=
ble and prepare for operation. That's great if all you want to do is win
pr=
estigious contests and are prepared to either do or pay for the extra
work
=
required to campaign such an aircraft. It's less great for everyone else,
a=
nd especially for those who buy such aircraft on the used market and find
o=
ut what a pain it can be.

Thanks, Bob K.
https://www.facebook.com/pages/HP-24...t/200931354951

On Wednesday, February 5, 2014 1:29:19 AM UTC-8, J. Nieuwenhuize wrote:
Op dinsdag 4 februari 2014 22:53:33 UTC+1 schreef :
=20
It seems it would make the structure more complex and heavier. I
would
=
guess it also would cost more to build a pylon wing glider.
=20
I would expect the exact opposite. Looking at all the parts, easily a
qua=
rter of all the parts of a normal 15M sailplane are in the wing-fuselage
in=
tersection and the spar roots are a pretty beefy (and heavy) part since
you=
have a joint at the highest loaded part of the whole structure. I don't
ha=
ve a weight breakdown at hand, but some earlier number-crunching yielded
ar=
ound 15 kg weight saved by carrying on the wing (and have 2 lighter
joints
=
outboard)
=20
All those automatic connections add a lot of complexity and weight too
an=
d you can reduce their number by half. Not to mention spoilers (drag
brakes=
) that can be in the middle of the wing since you're outside the
fuselages
=
"blocked zone" reducing the number of parts further.
=20
=20
=20
One of the interesting things about glider design is that, even for
ope=
n class, it's not really a free for all. The design has to comply with
nati=
onal airworthiness requirements and have acceptable flying
characteristics
=
for the average pilot. Compare this to an Unlimited Reno racer for
example.=
I remember what Gerhard Waibel said about the ASW-12 in hindsight. It
was
=
something about learning how all new, hot gliders will become older
gliders=
flown by less than top rank pilots eventually and you have to take that
in=
to consideration even when you're trying to make a world championship
conte=
nder.
=20
=20
=20
An excellent point. Yet, not certifying and having a homebuilt,
developme=
nt cost could be drastically less, though it'd still be wise to meet
every
=
requirement from CS22. Save France, to the best of my knowledge you can
fly=
homebuilt sailplanes in most soaring-minded countries.
=20
=20
=20
One. You need a fair pylon height to avoid interference drag in the
gap=
=20
=20
between the top of the fuselage and the wing's lower surface. I'd
say=
=20
=20
interference drag is relatively high on the Sunseeker shown he
=20
=20
=20
http://www.solar-flight.com/
=20
=20
=20
However I'm not an aerodynamics expert and have no idea what the
optimu=
m=20
=20
height sound be except that its unlikely to be less than 10-15% of
the=
=20
=20
wing chord, think of the Wien for this pylon height, and that its
one=
=20
=20
problem the Ku-4 Austria didn't suffer from.
=20
=20
=20
martin@ | Martin Gregorie
=20
gregorie. | Essex, UK
=20
org |
=20
=20
=20
A bit of number-crunching suggests something like 0.5-1 root chord, so
1-=
2 feet for a typical single-seater.

Helpers add complexity and management problems; the minimum
number to handle the weight is usually optimum.

I was owner of 1/4 of a Skylark III for a year; not sure which piece
but it could have been the C.S. Midweek flying meant
being shorthanded but I managed to rig it without hassle
with a (strong) gilrfriend.
1. Remove the fuselage and support in a H steady.
2. remove the CS ( wheels at the inside end in the trailer.
3.lift one end onto a suitable support.
4. lift the other end high enough for the girl friend to wheel
the fuselage under the CS, and roll it a bit to align the
lift fittings with the holes. Insert the long pins.

At 28 I was fit but not especially strong, but 1/2 the CS was manageable,
briefly. We never broke anything, the glider or me.

John F



At 02:08 06 February 2014, Martin Gregorie wrote:
On Wed, 05 Feb 2014 13:17:35 -0800, Bob Kuykendall wrote:

From the perspective of an inveterate pragmatist:

I think it comes down to operationality. Yes, the autoconnects add
complexity. Yes, placing the wing panel separation at the station of
maximum bending moment adds weight.

But what you get in return is a system of parts that allows for easy
storage and transport, rapid assembly, and high reliability. That
system
has been proven to result in good soaring performance at the lowest
possible cost in terms of operator fatigue. And that makes for a more
enjoyable soaring experience. And when it comes down to it, quality of
experience is what we should be trying to maximize here, not
necessarily
quality of performance.

Good point.

I've helped rig one of the Slingsbys which had a three piece wing.
Getting the C/s on was quite a hassle. While it can be done by three
people, having five on the job makes it a lot easier. The problem is that

you have to lift the wing quite high to clear the fuselage and keep it up

while the odd-numbered man attaches the wing to the fuselage. Putting the

tips on is easy but that doen't matter compared with handling the c/s.

One of the local clubs where I fly gas an SZD Pirat, which has a 15m
three-piece wing. They consider attaching and removing the c/s is such a
hassle that its normally left on and just the tips are removed when the
Pirat is put in the hangar.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Pat Beatty and Fritz Johl designed a number of sailplanes in South Africa in the 1960s-80s. They tried the pylon mounted wing with their BJ-5.

http://avcom.co.za/phpBB3/viewtopic....15852&start=15

There is a pic of the BJ-5 in the link. They reverted back to a high-shoulder mounted wing for later designs.

Clinton

On Sunday, February 9, 2014 10:03:36 AM UTC-5, firsys wrote:
A wing 3 ft above the CG will give excessive roll stability; to

get an acceptable roll rate there will have to be substantial

anhedral. It will be at least look peculiar but there may be

other detractions.

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.

On Tuesday, February 11, 2014 12:56:19 PM UTC-5, Soartech wrote:
On Sunday, February 9, 2014 10:03:36 AM UTC-5, firsys wrote: A wing 3 ft above the CG will give excessive roll stability; to get an acceptable roll rate there will have to be substantial anhedral. It will be at least look peculiar but there may be other detractions. 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.

Given the trend in sailplanes toward multiple dihedral breaks toward the tip, and the associated benefit of spreading the flow field spanwise, it seems that your statement is based upon dated knowledge. Or possible it applies in some cases and not others.
UH

Op zondag 9 februari 2014 06:48:59 UTC+1 schreef Steve Leonard:

But, to get those "1-2 sqm" of turbulent flow converted to laminar, you added almost that much area exposed to the flow. Some of which is still turbulent. Roughly 5 square feet of wing that was "hidden" in the fuselage is now exposed to air flow (2 feet spanwise, 30 inch chord). And, you have added a pylon that is something on the order of 24 to 30 inches tall, and probably more than 30 inches in chord. So, at best, another 5 square feet of wetted area of pylon. Probably more, because aerodynamically, you don't want max pylon width at the same chordwise location as max thickness on the wing.

Even if you can do it with a shorter pylon, it is still going to be difficult to get lower total drag with greater wetted area.

Steve

K



It sure would be difficult, but the odds seem favorable. While you increase wetted area, the drag coefficient of that area (and the original area) goes down by a factor of something like 5 if you can get it laminar.
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. 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.


I don't buy the point about anhedral. Many (ballasted) bigger ships have half of their weight in the wing, so we're talking about a 10" raise of the C of G or so. For many open-class ships, that's the difference between 1 and 1.5 G's (steep thermalling).

Bruce Carmichael seems to be the only one that has seriously pursued the idea of laminar-flow pylon wings. Time to win the lottery and start running a wind tunnel.

Thanks for the link to the BJ5 Clinton. Have been chasing pictures of that design for years.