Flap settings for Dummies

At the risk of having my ignorance exposed (again), is there any way a
reasonably competant (another problem in my case) can determine
"optimum" flap settings for the most commonly used speeds/
configurations, without resorting to a full-blown Johnson-style test
program?

I have been flying my new (to me) Ventus 2bx for a year now, and am
reasonably comfortable with the following flap settings (speeds in
kt):

40-60 Flaps L, +2, +1 dep on thermal characteristics
60-80 Flaps 0
80-100 Flaps -1
100+ Flaps -2, only happens on badly planned final glides or with
ballast.

However, I'm not sure how efficient these values are for my glider.
Should I stay with 0 all the way to 90kt, or maybe switch to -1
earlier? I mean, I've already give everyone else a big lead just due
to the IQ drop I experience immediately after release, so I'd hate to
think that I'm costing myself even more with poor flap settings!

I have played around some with watching the vario in cruise (TE) mode
to see if it makes much difference between 0 and -1 at say, 70kt, but
it's awful hard for me to tell. Anything else I should be looking
for?

TIA,

Frank (TA)

Some will suggest feeling for the aerodynamic neutral-force point with the
flap handle. The idea is that the lowest drag configuration is with the
flaps in trail. I think I remember reading that minimum drag is slightly
positive from the neutral force point.

Building a flap 'drag meter' isn't too difficult. Jim Phoenix has pictures
on his site of building one for his Nimbus 3. Pilots who fly with a drag
meter say they can 'dial in' the minimum drag flat setting for any airspeed.

Bill D


"Frank" wrote in message
...
At the risk of having my ignorance exposed (again), is there any way a
reasonably competant (another problem in my case) can determine
"optimum" flap settings for the most commonly used speeds/
configurations, without resorting to a full-blown Johnson-style test
program?

I have been flying my new (to me) Ventus 2bx for a year now, and am
reasonably comfortable with the following flap settings (speeds in
kt):

40-60 Flaps L, +2, +1 dep on thermal characteristics
60-80 Flaps 0
80-100 Flaps -1
100+ Flaps -2, only happens on badly planned final glides or with
ballast.

However, I'm not sure how efficient these values are for my glider.
Should I stay with 0 all the way to 90kt, or maybe switch to -1
earlier? I mean, I've already give everyone else a big lead just due
to the IQ drop I experience immediately after release, so I'd hate to
think that I'm costing myself even more with poor flap settings!

I have played around some with watching the vario in cruise (TE) mode
to see if it makes much difference between 0 and -1 at say, 70kt, but
it's awful hard for me to tell. Anything else I should be looking
for?

TIA,

Frank (TA)

On Mar 29, 4:14*pm, Frank wrote:
At the risk of having my ignorance exposed (again), is there any way a
reasonably competant (another problem in my case) can determine
"optimum" flap settings for the most commonly used speeds/
configurations, without resorting to a full-blown Johnson-style test
program?

I have been flying my new (to me) Ventus 2bx for a year now, and am
reasonably comfortable with the following flap settings (speeds in
kt):

40-60 Flaps L, +2, +1 dep on thermal characteristics
60-80 Flaps 0
80-100 Flaps -1
100+ Flaps -2, only happens on badly planned final glides or with
ballast.

However, I'm not sure how efficient these values are for my glider.
Should I stay with 0 all the way to 90kt, or maybe switch to -1
earlier? *I mean, I've already give everyone else a big lead just due
to the IQ drop I experience immediately after release, so I'd hate to
think that I'm costing myself even more with poor flap settings!

I have played around some with watching the vario in cruise (TE) mode
to see if it makes much difference between 0 and -1 at say, 70kt, but
it's awful hard for me to tell. *Anything else I should be looking
for?

TIA,

Frank (TA)

Frank,

Get yourself Grosskinsky ring made by Winter. You can get it from W&W.
The concept is that you set your ring, mounted on the ASI same way as
the McReady ring, to your weight and simply look at the speed factor
to which the needle is pointing to at the ASI and fly that speed. I
have ring like that on my ASI in my Diana.

Jacek
Pasco, WA

Bill,

I like the 'neutral-force' idea, and I think I have actually felt that
a little bit on my Ventus. I'll keep looking at that. As for
building a drag meter, I looked through the articles you referenced
and beat a quick retreat. I would be much more likely to do serious
damage to my glider (and/or me) than I would be to do anything
positive! ;-)

Frank


On Mar 29, 8:45*pm, "Bill Daniels" bildan@comcast-dot-net wrote:
Some will suggest feeling for the aerodynamic neutral-force point with the
flap handle. *The idea is that the lowest drag configuration is with the
flaps in trail. *I think I remember reading that minimum drag is slightly
positive from the neutral force point.

Building a flap 'drag meter' isn't too difficult. *Jim Phoenix has pictures
on his site of building one for his Nimbus 3. *Pilots who fly with a drag
meter say they can 'dial in' the minimum drag flat setting for any airspeed.

Bill D

"Frank" wrote in message

...



At the risk of having my ignorance exposed (again), is there any way a
reasonably competant (another problem in my case) can determine
"optimum" flap settings for the most commonly used speeds/
configurations, without resorting to a full-blown Johnson-style test
program?

I have been flying my new (to me) Ventus 2bx for a year now, and am
reasonably comfortable with the following flap settings (speeds in
kt):

40-60 Flaps L, +2, +1 dep on thermal characteristics
60-80 Flaps 0
80-100 Flaps -1
100+ Flaps -2, only happens on badly planned final glides or with
ballast.

However, I'm not sure how efficient these values are for my glider.
Should I stay with 0 all the way to 90kt, or maybe switch to -1
earlier? *I mean, I've already give everyone else a big lead just due
to the IQ drop I experience immediately after release, so I'd hate to
think that I'm costing myself even more with poor flap settings!

I have played around some with watching the vario in cruise (TE) mode
to see if it makes much difference between 0 and -1 at say, 70kt, but
it's awful hard for me to tell. *Anything else I should be looking
for?

TIA,

Frank (TA)- Hide quoted text -

- Show quoted text -

Frank,

As you fly the glider more, you'll get a feel for the best flap
position the way Bill describes. The chart in the flight manual is the
best starting point, I used to use little laminated versions for
different wing loadings for my Ventus 2C, but after time found myself
just going by the feel of the handle.

Before you do any of that though make sure your weight and balance is
current.

~ted/2NO

ps don't use the L setting for landing unless you really have to. It
puts excess stress on the mylar seals.

Tuno wrote:
Frank,

As you fly the glider more, you'll get a feel for the best flap
position the way Bill describes. The chart in the flight manual is the
best starting point, I used to use little laminated versions for
different wing loadings for my Ventus 2C, but after time found myself
just going by the feel of the handle.

Before you do any of that though make sure your weight and balance is
current.

~ted/2NO

ps don't use the L setting for landing unless you really have to. It
puts excess stress on the mylar seals.

pps: practice with the L setting enough to be good at it. A landing in a
short field isn't the place to practice. Mylar can be replaced in a few
hours, but even a simple repair might take weeks.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

On Mar 29, 10:36*pm, Tuno wrote:
Frank,

As you fly the glider more, you'll get a feel for the best flap
position the way Bill describes. The chart in the flight manual is the
best starting point, I used to use little laminated versions for
different wing loadings for my Ventus 2C, but after time found myself
just going by the feel of the handle.

Before you do any of that though make sure your weight and balance is
current.

~ted/2NO

ps don't use the L setting for landing unless you really have to. It
puts excess stress on the mylar seals.

Ted,

Thanks for the info. I'm afraid my w/b isn't current, but that is
because I spent quite a bit of time last year moving the CG around
(slowly and carefully) until it felt right. I plan to verify this
with formal w/b this year at the first contest that offers it ;-)

Hmm thanks for the tip about the 'L' setting: I have started using L
for thermalling in strong thermals, in the belief that it allows me to
core better, and to use no more than +2 for landings. If the mylar
seal is being overstressed any time the flaps are in 'L', I may want
to reconsider its use at all.

Frank (TA)

Properly applied mylar will not be affected by use of high positive
flap settings. I have had 3 gliders now with trailing edge dive
breaks that have flaps of +60 or more at full extension without any
noticeable deterioration to mylar integrity. The 304cz series was
shipped with mylar like this from the factory and I have never heard
of any problems except normal 5-7 year replacement cycles. If the
mylar comes off it just means you can put it back on properly.

2C

On Mar 29, 10:44 pm, Frank wrote:
On Mar 29, 10:36 pm, Tuno wrote:

Frank,

As you fly the glider more, you'll get a feel for the best flap
position the way Bill describes. The chart in the flight manual is the
best starting point, I used to use little laminated versions for
different wing loadings for my Ventus 2C, but after time found myself
just going by the feel of the handle.

Before you do any of that though make sure your weight and balance is
current.

~ted/2NO

ps don't use the L setting for landing unless you really have to. It
puts excess stress on the mylar seals.

Ted,

Thanks for the info. I'm afraid my w/b isn't current, but that is
because I spent quite a bit of time last year moving the CG around
(slowly and carefully) until it felt right. I plan to verify this
with formal w/b this year at the first contest that offers it ;-)

Hmm thanks for the tip about the 'L' setting: I have started using L
for thermalling in strong thermals, in the belief that it allows me to
core better, and to use no more than +2 for landings. If the mylar
seal is being overstressed any time the flaps are in 'L', I may want
to reconsider its use at all.

Frank (TA)

On Mar 29, 5:14*pm, Frank wrote:
At the risk of having my ignorance exposed (again), is there any way a
reasonably competant (another problem in my case) can determine
"optimum" flap settings for the most commonly used speeds/
configurations, without resorting to a full-blown Johnson-style test
program?

I have been flying my new (to me) Ventus 2bx for a year now, and am
reasonably comfortable with the following flap settings (speeds in
kt):

40-60 Flaps L, +2, +1 dep on thermal characteristics
60-80 Flaps 0
80-100 Flaps -1
100+ Flaps -2, only happens on badly planned final glides or with
ballast.

However, I'm not sure how efficient these values are for my glider.
Should I stay with 0 all the way to 90kt, or maybe switch to -1
earlier? *I mean, I've already give everyone else a big lead just due
to the IQ drop I experience immediately after release, so I'd hate to
think that I'm costing myself even more with poor flap settings!

I have played around some with watching the vario in cruise (TE) mode
to see if it makes much difference between 0 and -1 at say, 70kt, but
it's awful hard for me to tell. *Anything else I should be looking
for?

TIA,

Frank (TA)

I ran my own series of L/D, sink rate and flap/speed tests on my
DG808B using a gps waypoint grid and a PDA moving map. Each control
setting was flown with a straight glide for a distance of 5.8 miles in
both directions to cancel out the effect of wind. The tests were run
early morning before any noticeable thermal activity and performance
was then calculated from the gps log.
Any test has the possibility of errors from uncontrolled factors but I
believe the results are more accurate than the factory manual.

On 30 Mar, 03:30, Frank wrote:
Bill,

I like the 'neutral-force' idea, and I think I have actually felt that
a little bit on my Ventus. *I'll keep looking at that. *As for
building a drag meter, I looked through the articles you referenced
and beat a quick retreat. *I would be much more likely to do serious
damage to my glider (and/or me) than I would be to do anything
positive! ;-)

Frank

The neutral-force force idea has been around for decades but there is
no particular reason to think that it gives the best glide angle for
the aircraft as a whole for a given speed - not least because it takes
no account of the fuselage drag .

The trailing edge drag probe is useful for research but completely
useless as a real time flap guide during sporting flight - there are
just too many variables and too much noise in the reading.
Furthermore, once again, there is no reason to think that the flap
setting that gives the lowest drag probe reading for that one station
on the wing span is going to be the flap setting that maximises glide
performance for the aircraft as a whole. If anyone believes otherwise
they are welcome to make me an offer for my old Replogle drag probe
and meter but they will be wasting their money:-)

All the optimum settings change with wingloading (as well as air
density, bugs etc).

So, I would change the question round and ask "what is the best speed
for each flap setting"? For each flap setting/wing-loading
combination there will be an optimum airspeed when the fuselage is a
its minimum drag angle of attack. Find information on the minimum
drag angle of attack for the fuselage, set up the glider C of G to
mimimize elevator drag, choose the ballast load depending on
conditions and/or contest tactics, choose the cruise flap setting
depending on the degree of pilot optimism and let the glider run at
whatever speed corresponds to the fuselage angle of attack for lowest
drag - using your handy fuselage angle of attack meter or wool canopy
tufts. This will still be an approximation to the ideal but at least
it is simple to use.

In this way you end a choice of 2 or 3 three of inter-thermal cruise
speeds - just like Ingo Renner advised all those years ago.

Iain