Winglet performance

[Jock Proudfoot]

Anyone know in round numbers, what % increase in L/D garden-variety
winglets give?

[John Galloway[_1_]]

At 10:56 20 February 2011, Jock Proudfoot wrote:
>Anyone know in round numbers, what % increase in L/D garden-
variety
>winglets give?



Some relevant articles here:

http://www.mandhsoaring.com/Winglets.html

[BruceGreeff]

As with all things soaring - it depends.

In an attempt to summarise / save some reading. My understanding is as
follows:

You can take it that a correctly set up winglet affects performance
equivalent to adding approximately 50%-70% of the winglet span to the
wingspan. Resulting in higher aspect ratio and lower induced drag.

Problem is that as speed increases the form drag becomes dominant over
induced drag. So - only for a specific speed and AoA range do winglets
reduce drag (sometimes significantly). Get your design wrong and the
performance is actually easily impaired rather than improved.

Either way you get what you paid for. Some are set up for better
cruise,some are set up to improve climb performance, some are set up to
tame poor handling at low reynolds numbers, some are just tacked on
without any clear idea...

Theoretically the winglet can be set up to generate lift with a forward
component to the vector extracting waste energy from the tip vortex -
improving glide efficiency. Doing this well involves some complex
geometry and arcane design which I don't claim to understand.

On many gliders adding a winglet improves the handling, and so
indirectly improves achieved performance.

Bruce
--
Bruce Greeff
T59D #1771 & Std Cirrus #57

[Wayne Paul]

"Jock Proudfoot" > wrote in message ...
> Anyone know in round numbers, what % increase in L/D garden-variety
> winglets give?
>

Back in 1997, when winglets were entering the soaring scene, an article was published in the Free Flight magazine's April edition entitled "Do Winglets Work?" It can be found on page 16 of the following link. (http://www.wgc.mb.ca/sac/freeflight/97_04.pdf)

As for percentage of improvement, US racing handicaps are adjusted from as little as 0.002 to 0.010 in the case of the Discus 2b.

Wayne
HP-14 "6F"

[Peter F[_2_]]

My Discus CS had factory fitted winglets.

However the "Cut line" between wing & winglet wasn't as per the details
in the Schempp modification. (I assume the factory use a jig)

This lead me to have doubts as to the correct AoA of the winglet, so I
stopped using them (After about 5 years!)

In general use I found there to be no difference with or without, so I
continued to fly without them and didn't take the hit on the increased
handicap.

I never found an effective way of measuring what the toe in/out of the
winglet was, or figures for what it should be.

In summary, correctly fitted winglets may make an improvement but it's
easier to make things worse than to make things better

PF

[Bruce Hoult]

On Feb 20, 11:56*pm, Jock Proudfoot > wrote:
> Anyone know in round numbers, what % increase in L/D garden-variety
> winglets give?

It will always be a bit less than adding the same length in (equally
well designed) wingtip extensions instead.

You only go upwards if some external influence (class rules in gliders
and Americas Cup yachts, airport gate spacing in the 747-400) prevents
you from going sideways.

[Berry[_2_]]

In article >,
BruceGreeff > wrote:

> As with all things soaring - it depends.
>


When asked what airfoil he used on his HP winglets, Dick Schreder
replied "I use the ROF-POB airfoil. Questioned further he elaborated
"Round on front-pointy on back".

H301 "WB" "Why yes dear, I'd much rather go with you to pick out
countertops than fly my glider."

[Bill Bullimore[_2_]]

Having fitted winglets to my Mosquito some years ago I can say
there is (i) a small increase in climb rate (ii) possibly better l/d
and (iii) a definite improvement in handling.
For example, the left wing would drop at stall before, now it
stalls evenly. Also the handling at higher flap settings is vastly
improved.

On BGA handicapping, this amounts to a 1% performance
increase overall.

However...
- we spent 11 whole days getting them on straight and true

- the original kit was jigged incorrectly and would have resulted
in misalignment (food for thought when done professionally)

- the foil profile did not match the wing at the join. This was
corrected with re-fairing when the glider was refinished in Poland

Was it worth doing? Absobloodylutely!

bwBB




>My Discus CS had factory fitted winglets.
>
>However the "Cut line" between wing & winglet wasn't as per
the details
>in the Schempp modification. (I assume the factory use a jig)
>
>This lead me to have doubts as to the correct AoA of the
winglet, so I
>stopped using them (After about 5 years!)
>
>In general use I found there to be no difference with or
without, so I
>continued to fly without them and didn't take the hit on the
increased
>handicap.
>
>I never found an effective way of measuring what the toe
in/out of the
>winglet was, or figures for what it should be.
>
>In summary, correctly fitted winglets may make an
improvement but it's
>easier to make things worse than to make things better
>
>PF
>
>
>

[Kevin Neave[_2_]]

At 06:58 22 February 2011, Bill Bullimore wrote:
>
>However...
>- we spent 11 whole days getting them on straight and true
>
>- the original kit was jigged incorrectly and would have resulted
>in misalignment (food for thought when done professionally)
>
>- the foil profile did not match the wing at the join. This was
>corrected with re-fairing when the glider was refinished in Poland
>

Whose winglet kit did you fit to your Mosquito, how did you know the
correct toe in/out angles (i.e "Straight & True) & how did you measure
the the toe angle when fitted.

I'm dubious about the factory fitted winglets on my Discus B - again the
cut angle on the winglet doesn't match the Schempp tech note. But the
performance doesn't seem to be any worse with them than without and they
stop the tip dolly falling off (When manoeuvring on the ground, before we
get ay sarky comments!) so I continue using them.

Kevin

[Bill Bullimore[_2_]]

Kevin,
I won't name the kit supplier for obvious reasons, but we did spend some
considerable time getting the locating pins back to true and parallel,
before we could even start the fitting.

It was indeed a memorable moment when we sawed the first old tip off and
it fell with a klunk onto the floor.

From memory we only gave only 1 or 2 deg toe-in. There is a 'flat-ish'
surface on the outside winglet face to establish toe-in. It is a very
complex mod. because there are so many variables, I remember 6 of them:
~ rotational pitch
~ toe-in/out
~ splay (dihedral)
~ total span in and out
~ vertical position
~ fore/aft position

For the best match of the airfoil profile between winglet and wing, we
simply chose the 'least worse' position. Wing tape helped the final
match and covered some sins. Poland did a proper job later.

The main reference point established was the top rear tip (projected out
with layers of tape), which was used for all checks. On a non-flying day,
it might be worth running these checks on your assembled glider, I would
also use a point at the front of the wing/fuse join. It's amazing how
span can vary between left and right wings.

Also I believe we made a mistake with the tear-drop shaped eurathane
stick-on tip skid by sticking it on in the direction of flight. Next time
that gets replaced I will try and align it with the best l/d airflow.

Of course the real expert on all of this is Afandi Darlington, compared
with his expertise, one is reminded of the great philosopher Homer
Simpson's all-embracing observation:
"Doh- I wish I knew Stuff".

bwBB


>Whose winglet kit did you fit to your Mosquito, how did you know the
>correct toe in/out angles (i.e "Straight & True) & how did you measure
>the the toe angle when fitted.
>
>I'm dubious about the factory fitted winglets on my Discus B - again
the
>cut angle on the winglet doesn't match the Schempp tech note. But the
>performance doesn't seem to be any worse with them than without and
they
>stop the tip dolly falling off (When manoeuvring on the ground, before
we
>get ay sarky comments!) so I continue using them.
>
>Kevin
>
>

[Wayne Paul]

"Berry" > wrote in message ...
> In article >,
> BruceGreeff > wrote:
>
> When asked what airfoil he used on his HP winglets, Dick Schreder
> replied "I use the ROF-POB airfoil. Questioned further he elaborated
> "Round on front-pointy on back".
>

I am aware of a lot of Schreder sailplanes with winglets; however, I haven't come across any with Dick's plywood slabs described above bolted to the wingtip rib. Almost all the HP/RS-15 winglets are based on (copies of) the winglets described in the Free Flight page 6 article by Peter Masak.(http://www.wgc.mb.ca/sac/freeflight/92_02.pdf)

HP pilots note that winglets definitely improve aileron effectiveness resulting in higher roll rates.

Wayne
http://www.soaridaho.com/Schreder

[noel.wade]

Just to throw my voice into the mix - my DG-300 was retrofitted with
(factory-supplied) winglets...

The difference in L/D is so small with most winglets, that even if its
working correctly it would be hard to notice... Like others have said
- its "almost as good as" an equal improvement in span. What's the L/
D difference between a good 15-meter ship and a good 16-meter ship?
Very little.

However, I do notice an improvement in slow-speed handling with my
winglets on. This is where I believe a lot of people derive benefit
from them: Improved airflow over the wing at slow speeds and while
turning can directly translate into better thermalling performance,
both in reduced drag and in improved aileron control/authority.

--Noel

[Eric Greenwell[_4_]]

On 2/22/2011 12:11 PM, noel.wade wrote:
> Just to throw my voice into the mix - my DG-300 was retrofitted with
> (factory-supplied) winglets...
>
> The difference in L/D is so small with most winglets, that even if its
> working correctly it would be hard to notice... Like others have said
> - its "almost as good as" an equal improvement in span. What's the L/
> D difference between a good 15-meter ship and a good 16-meter ship?
> Very little.

No one can notice the difference between 40 and 42 in L/D. You might be
able to measure it with very careful measurements, but "notice" it? No.

> However, I do notice an improvement in slow-speed handling with my
> winglets on. This is where I believe a lot of people derive benefit
> from them: Improved airflow over the wing at slow speeds and while
> turning can directly translate into better thermalling performance,
> both in reduced drag and in improved aileron control/authority.

Noel echos my experience, and it's not just in flight, but on the ground
roll, too. It makes a glider less likely to drop a wing at the start of
takeoff, or near the end of the rollout.

I retrofitted factory winglets to my ASH 26E. Besides the above, I could
see (and confirm with photographs), that the wingtips were higher in
flight with the winglets than without, evidence that the winglets had
shifted the lift distribution outwards. I have no idea if the cruise L/D
was changed.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[John Smith]

Greenwell wrote:
>> However, I do notice an improvement in slow-speed handling with my
>> winglets on.

> Noel echos my experience, and it's not just in flight, but on the ground

The main benefit of winglets, especially for the older among us, is that
we don't have to bow that much to pick up the wing.

[Eric Greenwell[_4_]]

On 2/23/2011 1:59 AM, John Smith wrote:
> Greenwell wrote:
>>> However, I do notice an improvement in slow-speed handling with my
>>> winglets on.
>
>> Noel echos my experience, and it's not just in flight, but on the ground
>
> The main benefit of winglets, especially for the older among us, is that
> we don't have to bow that much to pick up the wing.

And, you can put a tire on it and it won't slip off in the wind! Not
that I'm suggesting that is a good practice...

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[Brad[_2_]]

On Feb 23, 1:59*am, John Smith > wrote:
> Greenwell wrote:
> >> However, I do notice an improvement in slow-speed handling with my
> >> winglets on.
> > Noel echos my experience, and it's not just in flight, but on the ground
>
> The main benefit of winglets, especially for the older among us, is that
> we don't have to bow that much to pick up the wing.

and to the younger, they look bitchin'

Brad

[kirk.stant]

On Feb 23, 3:27*pm, Brad > wrote:
> On Feb 23, 1:59*am, John Smith > wrote:
>
> > Greenwell wrote:
> > >> However, I do notice an improvement in slow-speed handling with my
> > >> winglets on.
> > > Noel echos my experience, and it's not just in flight, but on the ground
>
> > The main benefit of winglets, especially for the older among us, is that
> > we don't have to bow that much to pick up the wing.
>
> and to the younger, they look bitchin'
>
> Brad

Bah! Draglets!

Just stick your toe under the (beautifully unencumbered) wingtip and
lift your foot - voila, no bending required at all...

Anyway, if winglets were so great, why don't they have their own
winglets? - ad infinitum!

Kirk
66

[Doug Greenwell]

At 13:11 24 February 2011, kirk.stant wrote:
>On Feb 23, 3:27=A0pm, Brad wrote:
>> On Feb 23, 1:59=A0am, John Smith wrote:
>>
>> > Greenwell wrote:
>> > >> However, I do notice an improvement in slow-speed handling with
my
>> > >> winglets on.
>> > > Noel echos my experience, and it's not just in flight, but on the
>gro=
>und
>>
>> > The main benefit of winglets, especially for the older among us, is
>tha=
>t
>> > we don't have to bow that much to pick up the wing.
>>
>> and to the younger, they look bitchin'
>>
>> Brad
>
>Bah! Draglets!
>
>Just stick your toe under the (beautifully unencumbered) wingtip and
>lift your foot - voila, no bending required at all...
>
>Anyway, if winglets were so great, why don't they have their own
>winglets? - ad infinitum!
>
>Kirk
>66
>
>
>

you want winglets on winglets (wingwinglets? wing2lets?) ... Stanford got
there first :-)

http://aero.stanford.edu/CWing.html

Doug

[[email protected]]

On Feb 24, 8:11*am, "kirk.stant" > wrote:
> On Feb 23, 3:27*pm, Brad > wrote:
>
> > On Feb 23, 1:59*am, John Smith > wrote:
>
> > > Greenwell wrote:
> > > >> However, I do notice an improvement in slow-speed handling with my
> > > >> winglets on.
> > > > Noel echos my experience, and it's not just in flight, but on the ground
>
> > > The main benefit of winglets, especially for the older among us, is that
> > > we don't have to bow that much to pick up the wing.
>
> > and to the younger, they look bitchin'
>
> > Brad
>
> Bah! Draglets!
>
> Just stick your toe under the (beautifully unencumbered) wingtip and
> lift your foot - voila, no bending required at all...
>
> Anyway, if winglets were so great, why don't they have their own
> winglets? - ad infinitum!
>
> Kirk
> 66

The law of diminishing returns.
I sense some closet winglet envy leading to denial.
UH