I understand, a wing will perform optimally when the flap is set at
the proper angle for the airspeed ... any mismatch of flap to airspeed
will result in some performance losses vs. the correct setting. Of
course, we have a couple of compromises here ... the flaps are set at
fixed increments and the airspeed varies continuously ... so by
design, you will rarely have the flap and airspeed matched up
perfectly.

I remember seeing a story where one of the German schools modified an
LS-3 with springs, etc. so it automatically put in the correct amount
of flap for the airspeed ... did this result in a measurable
improvement?

Along the same lines, I have heard some pilots say they put the flap
in a position where they feel no pressure ... does this work?

I myself tend to go negative quicker or maintain a negative setting
longer ... then pulling in positive flap ... thinking being too
positive is more costly then too negative ... is this valid?

KK

Good, question. I'll follow this thread with interest.

I can make one comment. My Nimbus 2C has a complex set of trim/flap
interconnect springs and gas struts that probably to more to effect the
"feel" of the flap handle than aerodynamic forces. Even so, the neutral
force point on the flap handle "seems" to be about right. Most of the time
I keep my left hand on the flap handle with the setting at some intermediate
position between detents that "feels about right". The only time I use the
detents is when I need to use my left hand for something else.

I expect the only way to know for sure the flap setting is right is to
install a "drag meter" pitot rake on the flap trailing edge.

Bill Daniels


"Ken Kochanski (KK)" > wrote in message
ups.com...
>I understand, a wing will perform optimally when the flap is set at
> the proper angle for the airspeed ... any mismatch of flap to airspeed
> will result in some performance losses vs. the correct setting. Of
> course, we have a couple of compromises here ... the flaps are set at
> fixed increments and the airspeed varies continuously ... so by
> design, you will rarely have the flap and airspeed matched up
> perfectly.
>
> I remember seeing a story where one of the German schools modified an
> LS-3 with springs, etc. so it automatically put in the correct amount
> of flap for the airspeed ... did this result in a measurable
> improvement?
>
> Along the same lines, I have heard some pilots say they put the flap
> in a position where they feel no pressure ... does this work?
>
> I myself tend to go negative quicker or maintain a negative setting
> longer ... then pulling in positive flap ... thinking being too
> positive is more costly then too negative ... is this valid?
>
> KK
>

I'm reaching back a bit in my memory here so apologies
to the real practitioners if I miss anything.

I believe optimal flap settings are a function of angle
of attack, not airspeed, though obviously there is
a relationship between the two if you adjust for weight,
density, etc.

Second, the 'feel' on the flap handle is determined
by the hinge moment on the flap/flaperon. Again, minimum
hinge moment does not necessarily correspond to minimum
drag, maximum lift coeficient or maximum L/D. You might
want to optimize for any one of these at a given airspeed.
Each would require a different flap setting I think.

9B

At 16:24 10 July 2007, Bill Daniels wrote:
>Good, question. I'll follow this thread with interest.
>
>I can make one comment. My Nimbus 2C has a complex
>set of trim/flap
>interconnect springs and gas struts that probably to
>more to effect the
>'feel' of the flap handle than aerodynamic forces.
> Even so, the neutral
>force point on the flap handle 'seems' to be about
>right. Most of the time
>I keep my left hand on the flap handle with the setting
>at some intermediate
>position between detents that 'feels about right'.
> The only time I use the
>detents is when I need to use my left hand for something
>else.
>
>I expect the only way to know for sure the flap setting
>is right is to
>install a 'drag meter' pitot rake on the flap trailing
>edge.
>
>Bill Daniels
>
>
>'Ken Kochanski (KK)' wrote in message
ups.com...
>>I understand, a wing will perform optimally when the
>>flap is set at
>> the proper angle for the airspeed ... any mismatch
>>of flap to airspeed
>> will result in some performance losses vs. the correct
>>setting. Of
>> course, we have a couple of compromises here ... the
>>flaps are set at
>> fixed increments and the airspeed varies continuously
>>... so by
>> design, you will rarely have the flap and airspeed
>>matched up
>> perfectly.
>>
>> I remember seeing a story where one of the German
>>schools modified an
>> LS-3 with springs, etc. so it automatically put in
>>the correct amount
>> of flap for the airspeed ... did this result in a
>>measurable
>> improvement?
>>
>> Along the same lines, I have heard some pilots say
>>they put the flap
>> in a position where they feel no pressure ... does
>>this work?
>>
>> I myself tend to go negative quicker or maintain a
>>negative setting
>> longer ... then pulling in positive flap ... thinking
>>being too
>> positive is more costly then too negative ... is this
>>valid?
>>
>> KK
>>
>
>
>

Unfortunately we do not have A of A meter. I have come to the
conclusion that using the flight manual for specific flap setting and
speeds and wing loading is the way to go.
For example: At a gross of 800 lb and a flap setting of +20 the
optimum speed range is about 5-7 kt, about the same in a 45 deg. bank
with the needed extra speed added for that bank.
But in level cruise the minimum drag has a range from about 70 kt to
95 kt at zero flap and 800 lb gross. You will feel the aft loading
of the airfoil in climb at the Flap handle , but no load in cruise.
Due to friction this " flap handle feel", as an indicator is
unreliable and depending on the airfoil also misleading.
I can speak from practical experience. On my past projects I had to
calculate the speeds for each flap setting as well as wing loading
In case of that airfoil it had a very narrow speed range in each flap
setting to maximize performance but it comes at a cost of having to
pay attention to the flaps to get the most out of each setting.
Udo

On Jul 10, 11:49 am, "Ken Kochanski (KK)" >
wrote:
> I understand, a wing will perform optimally when the flap is set at
> the proper angle for the airspeed ... any mismatch of flap to airspeed
> will result in some performance losses vs. the correct setting. Of
> course, we have a couple of compromises here ... the flaps are set at
> fixed increments and the airspeed varies continuously ... so by
> design, you will rarely have the flap and airspeed matched up
> perfectly.
>
> I remember seeing a story where one of the German schools modified an
> LS-3 with springs, etc. so it automatically put in the correct amount
> of flap for the airspeed ... did this result in a measurable
> improvement?
>
> Along the same lines, I have heard some pilots say they put the flap
> in a position where they feel no pressure ... does this work?
>
> I myself tend to go negative quicker or maintain a negative setting
> longer ... then pulling in positive flap ... thinking being too
> positive is more costly then too negative ... is this valid?
>
> KK

On Tue, 10 Jul 2007 08:49:17 -0700, "Ken Kochanski (KK)"
> wrote:

>Along the same lines, I have heard some pilots say they put the flap
>in a position where they feel no pressure ... does this work?

Indeed this works for most gliders with the FX62-K... (ASW-20, LS-6
etc.) and FX-67-K...x (Nimbus-2, LS-3, Pik-20 etc.) airfoils, but most
later airfoils (ASH-25, ASW-27 etc.), need a firm "push" towards
negative settings.


Bye
Andreas

Ken Kochanski (KK) wrote:
> I understand, a wing will perform optimally when the flap is set at
> the proper angle for the airspeed ... any mismatch of flap to airspeed
> will result in some performance losses vs. the correct setting. Of
> course, we have a couple of compromises here ... the flaps are set at
> fixed increments and the airspeed varies continuously ... so by
> design, you will rarely have the flap and airspeed matched up
> perfectly.
>
> I remember seeing a story where one of the German schools modified an
> LS-3 with springs, etc. so it automatically put in the correct amount
> of flap for the airspeed ... did this result in a measurable
> improvement?
>
> Along the same lines, I have heard some pilots say they put the flap
> in a position where they feel no pressure ... does this work?
>
> I myself tend to go negative quicker or maintain a negative setting
> longer ... then pulling in positive flap ... thinking being too
> positive is more costly then too negative ... is this valid?
>
Its well worth digging out Dick Johnson's reports on flapped gliders and
looking at the combined polar he plots - the one showing polars for all
flap settings.

The polars for the ASW-20 blend quite nicely except at the ends of the
speed range for each setting and the available speed range gets smaller
for each setting at more positive settings. The implication, I suppose,
is that selecting the right flap is more critical at lower airspeeds.

The same may apply to other gliders too: I haven't looked.


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

On Jul 10, 11:49 am, "Ken Kochanski (KK)" >
wrote:
> I understand, a wing will perform optimally when the flap is set at
> the proper angle for the airspeed ... any mismatch of flap to airspeed
> will result in some performance losses vs. the correct setting. Of
> course, we have a couple of compromises here ... the flaps are set at
> fixed increments and the airspeed varies continuously ... so by
> design, you will rarely have the flap and airspeed matched up
> perfectly.
>
> I remember seeing a story where one of the German schools modified an
> LS-3 with springs, etc. so it automatically put in the correct amount
> of flap for the airspeed ... did this result in a measurable
> improvement?
>
> Along the same lines, I have heard some pilots say they put the flap
> in a position where they feel no pressure ... does this work?
>
> I myself tend to go negative quicker or maintain a negative setting
> longer ... then pulling in positive flap ... thinking being too
> positive is more costly then too negative ... is this valid?
>
> KK

Hi Ken - It depends very much on the glider. The Antares manual
specifically says "do not let the flap handle move to the position
of no force, as you will have the wrong flap setting" (I'm on the
road so that's an approximate quote). In other gliders I've flown
this is sort-of the correct flap setting (but far from exactly right).

Factors include the mechanics of the flap system, any trim
spring interconnect to flap, airfoil, etc...

To your second question, correct flap setting depends on CL
not airspeed. Again, the Antares manual specifically warns
against pulling the flap down during a pull-up. Because of the
flat polar and consequent high cruise speed, you would end
up with the flaps down way too soon and incur much extra
drag during the pull-up - more so than older designs.

Hope that helps,
Best Regards, Dave "YO"

On my want to do list is to build a flap controller for my HP16T.

I have been using PIC Microprocessers and pressure sensors that could
easily be adapted to do this. My initial Idea was to install a drag
rake that the microprocesser would read the pressure difference from
and would adjust the flaps accordingly. Alternate ideas are to connect
directly the the Pitot/Static system or build an AoA Sensor. All are
pretty easy to do but good low pressure sensors are in about $100
range and so far my budget hasn't made it to that. I really hadn't
considered AoA sensors until reading this thread, That might be a
cheaper way of doing this.

Brian Case
HP16T N16VP.



On Jul 10, 11:25 am, Udo > wrote:
> Unfortunately we do not have A of A meter. I have come to the
> conclusion that using the flight manual for specific flap setting and
> speeds and wing loading is the way to go.
> For example: At a gross of 800 lb and a flap setting of +20 the
> optimum speed range is about 5-7 kt, about the same in a 45 deg. bank
> with the needed extra speed added for that bank.
> But in level cruise the minimum drag has a range from about 70 kt to
> 95 kt at zero flap and 800 lb gross. You will feel the aft loading
> of the airfoil in climb at the Flap handle , but no load in cruise.
> Due to friction this " flap handle feel", as an indicator is
> unreliable and depending on the airfoil also misleading.
> I can speak from practical experience. On my past projects I had to
> calculate the speeds for each flap setting as well as wing loading
> In case of that airfoil it had a very narrow speed range in each flap
> setting to maximize performance but it comes at a cost of having to
> pay attention to the flaps to get the most out of each setting.
> Udo
>
> On Jul 10, 11:49 am, "Ken Kochanski (KK)" >
> wrote:
>
>
>

I've noted that there are AoA probes that use two pressure ports on 45
degree faces. Such as:
http://www.cgmasi.com/aviation/index.html although this one is also a pitot
probe.

I've wondered if pressure ports on the top and bottom of the fuselage nose
where the nose contours are at about 45 degrees to the airstream wouldn't
give about the same pressure diferential that could be used to compute AoA.

Bill Daniels


"Brian" > wrote in message
oups.com...
>
> On my want to do list is to build a flap controller for my HP16T.
>
> I have been using PIC Microprocessers and pressure sensors that could
> easily be adapted to do this. My initial Idea was to install a drag
> rake that the microprocesser would read the pressure difference from
> and would adjust the flaps accordingly. Alternate ideas are to connect
> directly the the Pitot/Static system or build an AoA Sensor. All are
> pretty easy to do but good low pressure sensors are in about $100
> range and so far my budget hasn't made it to that. I really hadn't
> considered AoA sensors until reading this thread, That might be a
> cheaper way of doing this.
>
> Brian Case
> HP16T N16VP.
>
>
>
> On Jul 10, 11:25 am, Udo > wrote:
>> Unfortunately we do not have A of A meter. I have come to the
>> conclusion that using the flight manual for specific flap setting and
>> speeds and wing loading is the way to go.
>> For example: At a gross of 800 lb and a flap setting of +20 the
>> optimum speed range is about 5-7 kt, about the same in a 45 deg. bank
>> with the needed extra speed added for that bank.
>> But in level cruise the minimum drag has a range from about 70 kt to
>> 95 kt at zero flap and 800 lb gross. You will feel the aft loading
>> of the airfoil in climb at the Flap handle , but no load in cruise.
>> Due to friction this " flap handle feel", as an indicator is
>> unreliable and depending on the airfoil also misleading.
>> I can speak from practical experience. On my past projects I had to
>> calculate the speeds for each flap setting as well as wing loading
>> In case of that airfoil it had a very narrow speed range in each flap
>> setting to maximize performance but it comes at a cost of having to
>> pay attention to the flaps to get the most out of each setting.
>> Udo
>>
>> On Jul 10, 11:49 am, "Ken Kochanski (KK)" >
>> wrote:
>>
>>
>>
>

Bill Daniels wrote:
> I've wondered if pressure ports on the top and bottom of the fuselage nose
> where the nose contours are at about 45 degrees to the airstream wouldn't
> give about the same pressure diferential that could be used to compute AoA.

The factory AOA meter in my DG-600 uses cross-connected pairs of
fuselage static ports just above the wing root, one set just aft of the
leading edge, and another at roughly 50% chord. The meter appears to be
a slightly modified electronic vario.

Marc

Mark,
would this arrangement work well enough with all predefined
flap setting? One would have to establish a base line
for example, one would start with say a Cl of 1.35 for max climbing
performance in 45 deg. bank and x flap setting. Would the system
respond true enough through out the usable Cl range and corresponding
flap settings with that established base line? I could see were this
arrangement would not correlate well at the other usable Cl number. I
really do not know and would like to find out.

On Jul 10, 7:31 pm, Marc Ramsey > wrote:
> Bill Daniels wrote:
> > I've wondered if pressure ports on the top and bottom of the fuselage nose
> > where the nose contours are at about 45 degrees to the airstream wouldn't
> > give about the same pressure diferential that could be used to compute AoA.
>
> The factory AOA meter in my DG-600 uses cross-connected pairs of
> fuselage static ports just above the wing root, one set just aft of the
> leading edge, and another at roughly 50% chord. The meter appears to be
> a slightly modified electronic vario.
>
> Marc

I find with my PIK that my pull ups are much better with the flaps
full negative until I get below 65 kts. I then slowly transition them
to +8 if I'm going to circle, but only to 0 if I'm going to pass
through the lift and go on. It seems that I waste less time and energy
if I go ahead and transition back to -8 as I nose over to go on. I've
often wondered if I'm doing this correctly, but it seems to work.

Jack Womack

2 cents, I've personally noticed generally good performance in my 20B
when I "float" the flaps while driving. The 20 seems to be fairly well
suited for this proceedure as other ships may not be for a variety of
reasons as noted in one of the posts.

RC-21


On Jul 10, 9:49 am, "Ken Kochanski (KK)" >
wrote:
> I understand, a wing will perform optimally when the flap is set at
> the proper angle for the airspeed ... any mismatch of flap to airspeed
> will result in some performance losses vs. the correct setting. Of
> course, we have a couple of compromises here ... the flaps are set at
> fixed increments and the airspeed varies continuously ... so by
> design, you will rarely have the flap and airspeed matched up
> perfectly.
>
> I remember seeing a story where one of the German schools modified an
> LS-3 with springs, etc. so it automatically put in the correct amount
> of flap for the airspeed ... did this result in a measurable
> improvement?
>
> Along the same lines, I have heard some pilots say they put the flap
> in a position where they feel no pressure ... does this work?
>
> I myself tend to go negative quicker or maintain a negative setting
> longer ... then pulling in positive flap ... thinking being too
> positive is more costly then too negative ... is this valid?
>
> KK

On Jul 11, 11:01 am, Rick Culbertson > wrote:
> 2 cents, I've personally noticed generally good performance in my 20B
> when I "float" the flaps while driving. The 20 seems to be fairly well
> suited for this proceedure as other ships may not be for a variety of
> reasons as noted in one of the posts.
>
> RC-21

Please describe exactly what you mean by "floating" the flaps.

Jack

Hi Jack,

I'll attempt to clarify;
My 1985 asw20b has the following five flap settings;

#1 = -12' (high speed cruise)
#2 = -6'
#3 = 0
#4 = +9 (thermalling)
#L = +38'/-8' (landing flaps)

I also have an additional after market thermal setting between flap
settings #3 & 4

When I speak of "floating the flaps" I'm referring to setting #1
through #3 but most often between the negative flap settings #1 & 2.

Dick Johnson (as I recall) noted in his 1978 asw20 report that he
notice the #2 flap setting didn't seem to produce a noticeable
performance improvement verses the #1 setting and suggested perhaps a
different/better flap setting was in order in this specific speed
range. Additionally, some very talented former 20 drivers told me
they "allowed" the flap handle to "float" between the negative
settings with good results. Meaning, to the location of the least
resistance.

In practice I have found the handle will fairly easily slide to the
next detent (flap setting) with increased speed and not as easily
slide back to the previous one when speed is decreased. I generally
keep my hand on the flap handle and feel for the change in pressure
and assist it with slight pressure for or aft to stay in the area of
least resistance. Of course when I leave a thermal and need to "get up
to speed" quickly, I always lead or set the flaps in advance to the
anticipated cruise speed setting. So what I'm generally referring to
is not when your driving for the next 10 kt thermal at 100+ kts or
when your floating along at best LD but when your varying between 70
and 90 kts. Additionaly I attempt to adjust subtile speed adjustments
within this range with the flap handle verses using the elevator as
has been sugested by some talented published pilots.

My 1985 asw20b seems (IMHO) to be ideally suited for this practice and
the feed back is quite pronounced. Conversely the same "former 20
drivers" have stated the ships they fly today, an asw27 and ash26e do
not accept this kind of flap assistance at all. So this may be unique
to the asw20 or similar ships of its era. In any event it seems to
work well with my ship.

I hope that's helpful,

Rick - 21



On Jul 11, 6:21 pm, Jack > wrote:
> On Jul 11, 11:01 am, Rick Culbertson > wrote:
>
> > 2 cents, I've personally noticed generally good performance in my 20B
> > when I "float" the flaps while driving. The 20 seems to be fairly well
> > suited for this proceedure as other ships may not be for a variety of
> > reasons as noted in one of the posts.
>
> > RC-21
>
> Please describe exactly what you mean by "floating" the flaps.
>
> Jack