Forward Swept Wings

[Canuck Bob]

I am working slowly on an evolving Fly5k design and considering a
swept forwrd wing. Does anyone know anything about thier design?
Also would anyone have experience with the Sisler Cygnet, Andreasson
BA-7, or Pottier's Bleu Citron designs. The Cygnet seems to be well
thought of but I don't know any owners or pilots that actually flew
one.

I've learned that mild forward sweep (less than 5 degrees)is not much
different than a standard wing. A tapered wing with lots of forward
sweep is prone to twist its tips upward under load so must be
torsionally rigid. I am sticking with the simple rectangular wing
planform and sweep of 3-4 degrees max.

This allows a compact mid wing and with a 30% C spar location the
pilot sits on the c of g with the mac moved forward slightly (app. 1/2
the amount of forward sweep).

[Fitzair4]

This summer their was a large ad in Trade-A-Plane about the production
equipment
auction on the ARV1 Super 2 certified airplane.
I always liked this plane because of its forward sweep mid-wing. It had
excellent visibility
up and down. They had it at Oshkosh for many years.
Anyone know why this plane was never successful in sales? It was built
out of all Aluminum.

It was designed in Europe and certified. Then a company in Canada had it.
Then the rights to Minnesota, then to some where in Ohio. I don't know if
any one bought it
at the auction.

A picture of a ARV1
http://www.planecheck.com/images/2480/ARV.jpg

I have gotten a letter this summer from a person in England that had one
for a couple year
and never had any complaint about it. He sold it, because he has many
planes and a Helicopter
to play with.

Has any one in this group flown a ARV1, that can give some good advice of
this plane
flight performance qualities.

Larry Fitzgerald

[Orval Fairbairn]

In article >,
(Fitzair4) wrote:

> This summer their was a large ad in Trade-A-Plane about the production
> equipment
> auction on the ARV1 Super 2 certified airplane.
> I always liked this plane because of its forward sweep mid-wing. It had
> excellent visibility
> up and down. They had it at Oshkosh for many years.
> Anyone know why this plane was never successful in sales? It was built
> out of all Aluminum.
>
> It was designed in Europe and certified. Then a company in Canada had
> it.
> Then the rights to Minnesota, then to some where in Ohio. I don't know
> if
> any one bought it
> at the auction.
>
> A picture of a ARV1
> http://www.planecheck.com/images/2480/ARV.jpg
>
> I have gotten a letter this summer from a person in England that had one
> for a couple year
> and never had any complaint about it. He sold it, because he has many
> planes and a Helicopter
> to play with.
>
> Has any one in this group flown a ARV1, that can give some good advice
> of
> this plane
> flight performance qualities.
>
> Larry Fitzgerald
>


The probable reasons for so little interest:

1. Looks -- it has a face only its designer would love.

2. Performance -- probably Kitfox performance.

3. Cost/performance/value -- Van's RV series wins here, all the way
across the board!

[Jay]

What is it that you're hoping the forward sweep is going to give you?

Also, under load, the forward swept wing will bend in a direction that
further increases its load("twist its tips upward"), and so on...
positive feedback... which could cause failure of the structure
("departure" of the wings from the rest of the plane).

(Canuck Bob) wrote in message >...
> I am working slowly on an evolving Fly5k design and considering a
> swept forwrd wing. Does anyone know anything about thier design?
> Also would anyone have experience with the Sisler Cygnet, Andreasson
> BA-7, or Pottier's Bleu Citron designs. The Cygnet seems to be well
> thought of but I don't know any owners or pilots that actually flew
> one.
>
> I've learned that mild forward sweep (less than 5 degrees)is not much
> different than a standard wing. A tapered wing with lots of forward
> sweep is prone to twist its tips upward under load so must be
> torsionally rigid. I am sticking with the simple rectangular wing
> planform and sweep of 3-4 degrees max.
>
> This allows a compact mid wing and with a 30% C spar location the
> pilot sits on the c of g with the mac moved forward slightly (app. 1/2
> the amount of forward sweep).

[Wallace Berry]

In article >,
(Canuck Bob) wrote:

> I am working slowly on an evolving Fly5k design and considering a
> swept forwrd wing. Does anyone know anything about thier design?
> Also would anyone have experience with the Sisler Cygnet, Andreasson
> BA-7, or Pottier's Bleu Citron designs. The Cygnet seems to be well
> thought of but I don't know any owners or pilots that actually flew
> one.
>
> I've learned that mild forward sweep (less than 5 degrees)is not much
> different than a standard wing. A tapered wing with lots of forward
> sweep is prone to twist its tips upward under load so must be
> torsionally rigid. I am sticking with the simple rectangular wing
> planform and sweep of 3-4 degrees max.
>
> This allows a compact mid wing and with a 30% C spar location the
> pilot sits on the c of g with the mac moved forward slightly (app. 1/2
> the amount of forward sweep).

A number of two place gliders use forward sweep for exactly the reason
you are citing. A common forward sweep wing glider is the Blanik L-13,
L-23 series (as used by the USAF Academy, the Civil Air Patrol, and
about a zillion glider operations all over the world) See
http://www.nwinternet.com/~blanikam/ba/prod01.htm.

The Alexander Schleicher Ka-7 and Ka-13 gliders are also very common
forward swept wing gliders. http://www.gliding-in-melbourne.org/ka7.htm
has a good three view.

Good luck with the design.

Wallace

[Kevin McCue]

A friend of mine has a Cygnet. Nice plane to fly w/excellent viz. Very
stiff wing on this plane, due to geodesic construction. Also the reason it
gets away with a single lift strut.

--
Kevin McCue
KRYN
'47 Luscombe 8E
Rans S-17 (for sale)




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[Paul Lee]

If you change a design to different wing sweep, don't forget
that it will move the center of lift in the direction of
sweep and it may significantly alter W & B and permissible CG
range position.

-------------------------------------------
Paul Lee, SQ2000 canard project: www.abri.com/sq2000

(Canuck Bob) wrote in message >...
> I am working slowly on an evolving Fly5k design and considering a
> swept forwrd wing. Does anyone know anything about thier design?
> Also would anyone have experience with the Sisler Cygnet, Andreasson
> BA-7, or Pottier's Bleu Citron designs. The Cygnet seems to be well
> thought of but I don't know any owners or pilots that actually flew
> one.
>
> I've learned that mild forward sweep (less than 5 degrees)is not much
> different than a standard wing. A tapered wing with lots of forward
> sweep is prone to twist its tips upward under load so must be
> torsionally rigid. I am sticking with the simple rectangular wing
> planform and sweep of 3-4 degrees max.
>
> This allows a compact mid wing and with a 30% C spar location the
> pilot sits on the c of g with the mac moved forward slightly (app. 1/2
> the amount of forward sweep).

[Dave Hyde]

Canuck Bob wrote:
>
> I am working slowly on an evolving Fly5k design and considering a
> swept forwrd wing. Does anyone know anything about thier design?

A little bit <g>
Like you say, a little forward sweep can get the spar out of the
way in the cabin. The big thing you have to work out is the potential
for structural divergence - the natural twist of the wing tends to
increase AOA, making the twist increase, etc...so you'll have to
make it stiffer than a straight or aft-swept wing.

Dave 'aeroelastica' Hyde

[Bill Daniels]

"Paul Lee" > wrote in message
om...
> If you change a design to different wing sweep, don't forget
> that it will move the center of lift in the direction of
> sweep and it may significantly alter W & B and permissible CG
> range position.
>
That depends on whether you sweep the tips forward or the roots
backwards.(Grin)

If the purpose is to move the wing spar carry-through structure aft of the
cockpit, the forward sweep is likely to leave the center of lift right where
it would be with the spar going through the cockpit with a straight wing.

Bill Daniels

[BD5ER]

>the natural twist of the wing tends to
>increase AOA, making the twist increase, etc...so you'll have to
>make it stiffer than a straight or aft-swept wing.

And you might need a bit more than normal dihedral..............

IMHO the added weight needed for the stiff wing would be worth it for the added
visibility and cockpit room on a recreational aircraft.

Take a look at the Marske site for some ideas on forward swept wing design.

http://www.continuo.com/marske/

Graphlite rod is actually quite cost effective.

[Dave Hyde]

BD5ER wrote:

> And you might need a bit more than normal dihedral..............

Oooohhh, good point. Anybody ever flown
an airplane with 'unstable' dihedral effect?
i.e. Step on the left pedal and the airplane
rolls right (but still yaws left)? It's
a very strange feeling.

In both examples (structural and dihedral)
a little forward sweep probably isn't going to make
much difference, but the smart designer should
understand both of these factors (and the ones we've
forgotten) and make an informed decision to neglect
them or not.

Dave 'Cl,beta' Hyde

[Thaddeus Beier]

Dave Hyde wrote:
>
> BD5ER wrote:
>
> > And you might need a bit more than normal dihedral..............
>
> Oooohhh, good point. Anybody ever flown
> an airplane with 'unstable' dihedral effect?
> i.e. Step on the left pedal and the airplane
> rolls right (but still yaws left)? It's
> a very strange feeling.
>
> In both examples (structural and dihedral)
> a little forward sweep probably isn't going to make
> much difference, but the smart designer should
> understand both of these factors (and the ones we've
> forgotten) and make an informed decision to neglect
> them or not.
>
> Dave 'Cl,beta' Hyde
>

I've read that 15 degrees of (typical rearward) sweep
equals about one degree of dihedral. Four degrees of
forward sweep would require just a smidgen more dihedral.

I agree with the above posters that the biggest bugaboo
with FSW is increasing washin with load factor. Composite
planes (like the X-29) orient the fibers to counteract
that effect. I had the privelege of walking around and
climbing into an X-29 while it was at Grumman, the wing
had a spectacular amount of washin built into it, but the
wing skins were designed so that the amount of washin
didn't change as the wings deflected upward. As I recall
rather than the axis of the carbon fiber threads pointing
parallel to the spar, they pointed more forward than that.

Still, for a few degrees of sweep and a reasonably
torsionally strong wing construction, I can't imagine you'll
have too much trouble.

One idea I had was kind of odd, but it might work.
Rig the ailerons so that as the wingtips deflect upward
the ailerons move up, decreasing the lift at the wingtips.
You could rig the ailerons to do this automatically if the
control rod traversed the wing from bottom to top as it
moved out the wing.

thad

[nafod40]

Thaddeus Beier wrote:
> Dave Hyde wrote:
>
>
> I've read that 15 degrees of (typical rearward) sweep
> equals about one degree of dihedral. Four degrees of
> forward sweep would require just a smidgen more dihedral.

Give the Blanik gliders a good look. They have as much forward sweep as
I've seen on a plane. Aluminum construction. Aerobatic. Here's a page
that shows the wing forward sweep.

http://www.nwinternet.com/~blanikam/ba/prod06.htm

[Kevin Horton]

On Thu, 02 Oct 2003 02:03:42 +0000, Dave Hyde wrote:

> BD5ER wrote:
>
>> And you might need a bit more than normal dihedral..............
>
> Oooohhh, good point. Anybody ever flown an airplane with 'unstable'
> dihedral effect? i.e. Step on the left pedal and the airplane rolls
> right (but still yaws left)? It's a very strange feeling.
>
>
The Alpha Jet's dihedral effect goes unstable at high Mach - above about
M0.86 IIRC. I agree that the "wrong" roll due to yaw would get your
attention if you ever had cause to use the rudder. The dutch roll was
absolutely bizarre too, as the roll rate at each point in the cycle was
very different than a normal dutch roll.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

[Dave Hyde]

Kevin Horton wrote:

> The dutch roll was absolutely bizarre too, as the roll rate
> at each point in the cycle was very different than a normal
> dutch roll.

I think I just sprained my wrist trying to figure that one
out :-)
I've seen it in the Calspan Lear and a couple of simulators,
most of them accurate but one with a sign error :-)
It's not something that jumps right out at you, but once
you notice it it annoys the snot out of you.

....stability augmentation is your friend.

Dave 'wris****ch kill' Hyde

[Kevin Horton]

On Thu, 02 Oct 2003 23:02:41 +0000, Dave Hyde wrote:

> Kevin Horton wrote:
>
>> The dutch roll was absolutely bizarre too, as the roll rate at each
>> point in the cycle was very different than a normal dutch roll.
>
> I think I just sprained my wrist trying to figure that one out :-)
> I've seen it in the Calspan Lear and a couple of simulators, most of them
> accurate but one with a sign error :-) It's not something that jumps right
> out at you, but once you notice it it annoys the snot out of you.
>
> ...stability augmentation is your friend.
>

Well, as you know, you can look at the wing tip during a dutch roll and
watch the path it makes against the horizon to estimate the phi to beta
ratio (ratio of lateral motion to directional motion for the non-flight
test folks). In a normal dutch roll you'll see the wing tip rising as it
moves forward, i.e. if the nose is moving left, the left wing will be
rising. So if you watch the left wing tip, you'll see it making a circle
or ellipse in a clockwise direction. If the lateral stablity if
negative, the left wing will make a circle or ellipse in the
counter-clockwise direction. If you are used to normal dutch rolls, it
feels very strange.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

[Canuck Bob]

Thanks to everyone. I am working on a study that includes building
cheaply and safely.

The forward sweep came about because of two reasons, excellent
visibility and its not real common. I like to look down and fly low
and slow. The world doesn't need another strutted hi-wing amateur
design from me, that is for sure. I also considered a low wing, I own
a Fly Baby, but I do like looking at scenery. However the low wing
visibility in the pattern is very reassuring.

After doing some research on the web regarding the Cygnet, French Bleu
Citron, and the Andreasson Ba-7 the forward sweep really attracted me.
I want a single seater Canadian Ultralight with a heavy A65 in the
nose. The Cygnet would be nose heavy according to the designer from a
Sport Aviation article.

I will use the Cygnet plans as a reference and also study the Bleu
Citron, Tandem Airbike and such to understand a 500# empty 900# gross
airframe. The Cygnet uses geodesic construction for a rigid wing but
I want my fuel in the wings and not my lap or behind my head(these
forward sweep planes put the tank behind the cockpit head area).
Because of my size and the weight of the Continental with a metal prop
keeping the pilot as far rearward as possible will be important. A
35%C spar and some forward sweep >5 degreeswill work for me. By using
a tail with good authority and reasonable arm a forward range C of G
would be acceptable.