Bi-wing glider

[Jono Richards]

A thought came to me the other day...

Now, I have never seen a bi-wing glider, but was thinking,
could a bi-wing glider of, say 15m wingspan, effectively
have 30m performace?

This is probably a stupid uneducated question, and
I would imagine that it hasnt been done because it
wouldnt work! But its certainly something I am interested
in.

Think of it...a bi-wing ETA giving a total of 60m performance!


JR

[Bert Willing]

The main idea of long wings is to reduce the relative part of the wingtip
vortexes in the total amount of the drag.
Having 4 vortexes instead of 2 certainly doesn't help.


"Jono Richards" > wrote in
message ...
>A thought came to me the other day...
>
> Now, I have never seen a bi-wing glider, but was thinking,
> could a bi-wing glider of, say 15m wingspan, effectively
> have 30m performace?
>
> This is probably a stupid uneducated question, and
> I would imagine that it hasnt been done because it
> wouldnt work! But its certainly something I am interested
> in.
>
> Think of it...a bi-wing ETA giving a total of 60m performance!
>
>
> JR
>
>
>

[Martin Gregorie]

Jono Richards wrote:
> A thought came to me the other day...
>
> Now, I have never seen a bi-wing glider, but was thinking,
> could a bi-wing glider of, say 15m wingspan, effectively
> have 30m performace?
>
> This is probably a stupid uneducated question, and
> I would imagine that it hasnt been done because it
> wouldnt work! But its certainly something I am interested
> in.
>
Short answer: no.

The F1H competition model glider class has a maximum total *projected*
wing area limit, so some years back an ingenious chap built a bi-plane
version with no stagger so the projected area was the same as for a
monoplane but with halved wing loading. He omitted interplane struts to
minimize drag, but the model flew better with one wing removed.

The reason was that you get a lot of interference drag between the
wings. His interplane spacing was about 1.5 wing chords. Theoretical
calculations later showed that he should have used a spacing of at least
5 chords to avoid interference gap.

A sailplane with a 0.7m average chord would need an interplane gap of
3.5m and you'd still have a lot of drag from interplane struts. You'd
need step-ladders or a fork lift to rig it.

However, it would win the Ugly Trophy hands down.

--
martin@ | Martin Gregorie
gregorie. |
org | Zappa fan & glider pilot

[COLIN LAMB]

"I have never seen a bi-wing glider"

Orville and Wilbur used to fly them.

Colin

[Jono Richards]

At 14:12 21 February 2006, Colin Lamb wrote:
>'I have never seen a bi-wing glider'
>
>Orville and Wilbur used to fly them.
>
>Colin
>
>
Colin,

Good point hadnt thought of that! Were those not kites,
rather than gliders? Or maybe I should read my history
books again...

Right so there is no benefit in havin two wings than
one? even if staggered to reduce the interference from
each?

As regards to using a fork lift to rig, no i am sure
it would be far from practical, but then again, what
would some people do in the strive for performance...!?

JR

[bumper]

As Martin said, "interference drag" between the two wings would be the main
culprit. High pressure under the upper wing migrating to the low pressure
area above the lower wing. Some biplane designs try to counter this with
more spacing between the wings, or more off-set (think Beech Staggerwing).

Early aircraft design embraced multiple wings partly because the box
structure was easy to make strong using external wires and struts, the
additional drag wasn't such a big deal, as they didn't fly all that fast.

bumper


"Jono Richards" > wrote in
message ...
>A thought came to me the other day...
>
> Now, I have never seen a bi-wing glider, but was thinking,
> could a bi-wing glider of, say 15m wingspan, effectively
> have 30m performace?
>
> This is probably a stupid uneducated question, and
> I would imagine that it hasnt been done because it
> wouldnt work! But its certainly something I am interested
> in.
>
> Think of it...a bi-wing ETA giving a total of 60m performance!
>
>
> JR
>
>
>

[Tim Ward]

"Jono Richards" > wrote in
message ...
> At 14:12 21 February 2006, Colin Lamb wrote:
> >'I have never seen a bi-wing glider'
> >
> >Orville and Wilbur used to fly them.
> >
> >Colin
> >
> >
> Colin,
>
> Good point hadnt thought of that! Were those not kites,
> rather than gliders? Or maybe I should read my history
> books again...
>
> Right so there is no benefit in havin two wings than
> one? even if staggered to reduce the interference from
> each?
>
> As regards to using a fork lift to rig, no i am sure
> it would be far from practical, but then again, what
> would some people do in the strive for performance...!?
>
> JR

You probably should go back and read your history again.
The Wright's 1902 glider is probably the most important aircraft in the
history of aviation.
It's the aircraft all their patents were based on.

Tim Ward

[Al]

Ok, what if one of the wings is a canard? If the elevator pushes down to
support the nose, and a canard lifts, doesn't that make a canard more
efficient?

Al


"Bert Willing" > wrote in message
...
> The main idea of long wings is to reduce the relative part of the wingtip
> vortexes in the total amount of the drag.
> Having 4 vortexes instead of 2 certainly doesn't help.
>
>
> "Jono Richards" > wrote in
> message ...
>>A thought came to me the other day...
>>
>> Now, I have never seen a bi-wing glider, but was thinking,
>> could a bi-wing glider of, say 15m wingspan, effectively
>> have 30m performace?
>>
>> This is probably a stupid uneducated question, and
>> I would imagine that it hasnt been done because it
>> wouldnt work! But its certainly something I am interested
>> in.
>>
>> Think of it...a bi-wing ETA giving a total of 60m performance!
>>
>>
>> JR
>>
>>
>>
>
>

[[email protected]]

>>Ok, what if one of the wings is a canard? If the elevator pushes down to
support the nose, and a canard lifts, doesn't that make a canard more
efficient? <<

No. Take a look at the success of Rutan's Solitaire.

The disadvantages with a canard or a tandem wing plane is that it is
hard to use flaps, and to keep the plane pitch stable you end up with a
plane that won't develop the same maximum total lift coefficient as a
"normal" plane because you can never use the aft wing to it's full
potential. This means that you end up having a higher minimum speed
for a given wing area or need more wing for a given minimum speed.
What all this means is that the speed range for efficient operation
will be less than that of a comparable "normal" plane.

You can tune the plane to be efficient at one speed by matching the
airfoils and relative areas and this is how some of the canard
homebuilts manage to show such good cruise performance. But they all
suffer from high landing speeds.

About the only way I see to improve on the standard glider - might - be
to develop a flying wing with some kind of weight shift to increase
it's speed range.

The canard/tandem wing planform does have some advantages for powered
planes but even there I've decided that a negative stagger biplane with
a conventional empenage (Durand Mk V is an example) is more efficient
than a pure tandem wing or canard ..................... and why my Q-2
will fly with a V-tail and flaps if I ever decide to finish it.
=======================
Just my opinion
Leon McAtee

[Martin Gregorie]

Jono Richards wrote:

> Good point hadnt thought of that! Were those not kites,
> rather than gliders? Or maybe I should read my history
> books again...
>
As other people have said, all their important patents were on the
glider. They famously said they thought that making a machine fly should
not be difficult, but making it controllable would be the main problem.
Their main patents reflected this.

One point I didn't know until recently is that the 1902 glider was flown
for proficiency before they tackled the Flyer and, apparently, Orville
flew the glider fairly extensively after the Flyer was in the record books.

> Right so there is no benefit in havin two wings than
> one? even if staggered to reduce the interference from
> each?
>
Not for efficiency. The big biplane advantage is that you can make a
very light, strong structure by cross-bracing it with wire.


--
martin@ | Martin Gregorie
gregorie. |
org | Zappa fan & glider pilot

[Al]

Thanks, very informative. Al


> wrote in message
oups.com...
>>>Ok, what if one of the wings is a canard? If the elevator pushes down to
> support the nose, and a canard lifts, doesn't that make a canard more
> efficient? <<
>
> No. Take a look at the success of Rutan's Solitaire.
>
> The disadvantages with a canard or a tandem wing plane is that it is
> hard to use flaps, and to keep the plane pitch stable you end up with a
> plane that won't develop the same maximum total lift coefficient as a
> "normal" plane because you can never use the aft wing to it's full
> potential. This means that you end up having a higher minimum speed
> for a given wing area or need more wing for a given minimum speed.
> What all this means is that the speed range for efficient operation
> will be less than that of a comparable "normal" plane.
>
> You can tune the plane to be efficient at one speed by matching the
> airfoils and relative areas and this is how some of the canard
> homebuilts manage to show such good cruise performance. But they all
> suffer from high landing speeds.
>
> About the only way I see to improve on the standard glider - might - be
> to develop a flying wing with some kind of weight shift to increase
> it's speed range.
>
> The canard/tandem wing planform does have some advantages for powered
> planes but even there I've decided that a negative stagger biplane with
> a conventional empenage (Durand Mk V is an example) is more efficient
> than a pure tandem wing or canard ..................... and why my Q-2
> will fly with a V-tail and flaps if I ever decide to finish it.
> =======================
> Just my opinion
> Leon McAtee
>

[[email protected]]

Tim Ward wrote:
>
> You probably should go back and read your history again.
> The Wright's 1902 glider is probably the most important aircraft in the
> history of aviation.
> It's the aircraft all their patents were based on.
>
> Tim Ward

Don't forget the Wright 1911 biplane glider. On 24 Oct 1911, Orville
soared it for 9 minutes 45 seconds, a world record that stood for 10
years.

http://worlddmc.ohiolink.edu/History/Search?fieldname=date&searchstring=19111026&searchstatus=0

John

[Lars Peder Hansen]

Thinking out-of-the-box here: How about a one-piece circular wing,
compressed so it would look like a flat oval from the front? -Inter-wing
interference might be an issue, but this design would certainly get rid of
the wingtip induced drag.

Oh, well, hopefully spring's coming soon. Then we can al get back to our old
sane selfs again..

Lars Peder
DG-600 (conventional wings), Denmark.



"bumper" > wrote in message ...
> As Martin said, "interference drag" between the two wings would be the
main
> culprit. High pressure under the upper wing migrating to the low pressure
> area above the lower wing. Some biplane designs try to counter this with
> more spacing between the wings, or more off-set (think Beech Staggerwing).
>
> Early aircraft design embraced multiple wings partly because the box
> structure was easy to make strong using external wires and struts, the
> additional drag wasn't such a big deal, as they didn't fly all that fast.
>
> bumper
>
>
> "Jono Richards" > wrote in
> message ...
> >A thought came to me the other day...
> >
> > Now, I have never seen a bi-wing glider, but was thinking,
> > could a bi-wing glider of, say 15m wingspan, effectively
> > have 30m performace?
> >
> > This is probably a stupid uneducated question, and
> > I would imagine that it hasnt been done because it
> > wouldnt work! But its certainly something I am interested
> > in.
> >
> > Think of it...a bi-wing ETA giving a total of 60m performance!
> >
> >
> > JR
> >
> >
> >
>
>

[AZ T-rex]

I have an article reprinted from the 1920's IIRC that is an account and
has pictures of a bi-wing glider built and flown by Ed Heath. He had
basically omitted the engine from one of his bi-planes and moved the
pilot location for the correct CG. I believe this was the glider he
set several records in. Notably none were soaring records. Something
like farthest distance towed and first glider to perform a loop. The
plane sufferred a very poor L/D due to interplane struts and full wire
bracing!

T-rex

[[email protected]]

How about a biplane configuration wherein the upper and lower wings
are conected only at the tips by an endplate? Within a limited span you
could reduce the chord of the wings for a given wing area and the
endplate would help with the tip vorticies in the same way as a winglet
on a monoplane glider.

BUT; Absolute hell to trailer and rig and I'm sure that if it would
work one of the Akafliegs would have tried it by now...

Anyone ever tried to soar an autogyro?

And, yes, I have gone crazy waiting for the flying season to start
again.

[COLIN LAMB]

Anyone ever tried to soar an autogyro?

Autogyros have been towed behind automobiles, then released. Somewhere on
the way down, they must have encountered a thermal which reduced the
descent. About like asking if anyone has ever tried soaring a Piper
Tri-Pacer.

When ytou get to asking questions like this, it is time to go out and sit in
your sailplane for an hour or so. Maybe listen to a ball game or eat lunch
while you open and close the spoilers. That usually is enough to take your
mind off such things as autogyros soaring. Maybe even polish up the wings
and canopy.

Colin

[Ian Johnston]

On Wed, 22 Feb 2006 21:34:01 UTC, "Lars Peder Hansen"
> wrote:

: Thinking out-of-the-box here: How about a one-piece circular wing,
: compressed so it would look like a flat oval from the front? -Inter-wing
: interference might be an issue, but this design would certainly get rid of
: the wingtip induced drag.

I don't think it would get rid of the induced drag - you'd still need
circulation around the wing, and that vorticity has to go somewhere.

Ian

[Ian Johnston]

On Sat, 25 Feb 2006 07:56:53 UTC, wrote:

: How about a biplane configuration wherein the upper and lower wings
: are conected only at the tips by an endplate?

Horribly inefficient for soaring, as the bottom wing gets pushed down
by the top wing.

Ian

[Welsh Druid]

> Anyone ever tried to soar an autogyro?

Well it depends on what you mean by "soar" - does ridge soaring count?

I have seen a home built (kit) autogyro tested out by tethering it on the
edge of the ridge in the hill lift (at the point where the gliders were
launched by bungee). The pilot flew it up and down and slightly sideways but
did not release the tether.

[Bob Salvo]

I recommend not closing the canopy entirely. I almost asphyxiated myself
with the canopy closed and the vent open.

Bob Salvo

"COLIN LAMB" > wrote in message
ink.net...
> Anyone ever tried to soar an autogyro?
>
> When ytou get to asking questions like this, it is time to go out and sit
in
> your sailplane for an hour or so. Maybe listen to a ball game or eat
lunch
> while you open and close the spoilers.

[Airthug]

Jono Richards wrote:
> A thought came to me the other day...
>
> Now, I have never seen a bi-wing glider, but was thinking,
> could a bi-wing glider of, say 15m wingspan, effectively
> have 30m performace?
>
> This is probably a stupid uneducated question, and
> I would imagine that it hasnt been done because it
> wouldnt work! But its certainly something I am interested
> in.
>
> Think of it...a bi-wing ETA giving a total of 60m performance!
>
>
> JR

Look up the "Easy Riser"
I flew one years ago. Tailless biplane (hang) glider.
positive stagger, weight shift pitch & tip rudder roll control.
A classic to fly, but had no performance advantage.
Ultimatly ended up being flown mostly as a powered ultralight.