What is magical about a 45 degree bank?

[son_of_flubber]

I know that a 45 degree bank is useful for flying small circles and staying in small thermals, but is there something special about a 45 degree bank compared to say a 50 degree bank?

For example, does the designer intend for the glider to do something special at 45 degrees? Is the glider designed to balance aerodynamic forces in a particular harmony at a precise 45 degree bank?

[[email protected]]

On Saturday, October 5, 2013 12:48:27 PM UTC-5, son_of_flubber wrote:
> I know that a 45 degree bank is useful for flying small circles and staying in small thermals, but is there something special about a 45 degree bank compared to say a 50 degree bank?
>
>
>
> For example, does the designer intend for the glider to do something special at 45 degrees? Is the glider designed to balance aerodynamic forces in a particular harmony at a precise 45 degree bank?

Simple: the tan 45 deg is = 1 so you are #1, A-OK, top of the world, #1 flying ace, you get the drift! (don't drift when thermaling)
On the other side, the tan of 30 and 60 deg is a mess, don't go there!
Seriously, there seems to be a sweet spot around 45 deg where the radius flown at our thermaling speeds is keeping us closest to the high-climb values found at the center of the thermal without the penalty of higher wingloading and resulting higher stall speeds and overall higher sink at bank angles >50 deg.
Not sure this was helpful...
Herb

[[email protected]]

I see Herb is just as frustrated as I am that it's raining...

The magic of 45 degrees is that if you tell someone to thermal at 45, they'll probably thermal at 35 - 40 which is really the optimum most of the time, at least over the soggy midwest!

John Cochrane

[Matt Herron Jr.]

On Saturday, October 5, 2013 10:48:27 AM UTC-7, son_of_flubber wrote:
> I know that a 45 degree bank is useful for flying small circles and staying in small thermals, but is there something special about a 45 degree bank compared to say a 50 degree bank?
>
>
>
> For example, does the designer intend for the glider to do something special at 45 degrees? Is the glider designed to balance aerodynamic forces in a particular harmony at a precise 45 degree bank?

"The proper angle of bank in a thermal is one which yields the fastest average rate of climb" --Jim Indrebro--

Obvious, but often overlooked metric. Every thermal is different, airspeed is a factor, airplane, etc., etc.

Matt

[[email protected]]

On Saturday, October 5, 2013 1:48:27 PM UTC-4, son_of_flubber wrote:
> I know that a 45 degree bank is useful for flying small circles and staying in small thermals, but is there something special about a 45 degree bank compared to say a 50 degree bank? For example, does the designer intend for the glider to do something special at 45 degrees? Is the glider designed to balance aerodynamic forces in a particular harmony at a precise 45 degree bank?

Over time we have learned that the best climb rate tends to be when the optimum trade off between circling diameter and sink rate increase caused by banking in achieved. This turns out to be right around 40 degrees. Most people over estimate their bank angle. When they think they are 45 degrees, more likely they are just over 30. Only rarely does more than 45 improve climb.. The key is tighten till the climb rate is steadily best and stick with it..
Most gliders, left alone to spiral, will settle in around 30 degrees from my experience.
FWIW
UH

[Peter Higgs]

Hi, there is a very descriptive book by Markus Lisken and Ulf Gerber called
Radio Control Thermal Gliding, that uses some very complex mathematics to
investigate the best possible thermaling practice.

In it's comparison of various birds, it concludes that Buzzards are better
thermalers than Sea-gulls, because they have a lower Wing Aspect Ratio
(6:1 cf 12:1.) and are able to make tighter turns into the middle of the
lift. It quotes.. 'These wing shapes clearly show that a design to give
minimal sink in no way concur with a design for maximum climb rate'.

So your K8 might outperform a ASW29 in a small diameter thermal.

[Martin Gregorie[_5_]]

On Sun, 06 Oct 2013 08:15:31 +0000, Peter Higgs wrote:

> Hi, there is a very descriptive book by Markus Lisken and Ulf Gerber
> called Radio Control Thermal Gliding, that uses some very complex
> mathematics to investigate the best possible thermaling practice.
>
> In it's comparison of various birds, it concludes that Buzzards are
> better thermalers than Sea-gulls, because they have a lower Wing Aspect
> Ratio (6:1 cf 12:1.) and are able to make tighter turns into the middle
> of the lift. It quotes.. 'These wing shapes clearly show that a design
> to give minimal sink in no way concur with a design for maximum climb
> rate'.
>
I watched a medium sized buzzard-shaped raptor at Wiener Neustadt the
other day as it picked up lift at 50-60ft over the apron and climbed
away. It went up like a rocket in a very small corkscrew spiral, not more
than 3 times its own span and using under 40 degrees bank.

Try doing that in any current sailplane!



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

[Chris Rollings[_2_]]

Nothing magical about 45 degree angle of bank. For any given angle of
bank, turn radius varies with the square of (true) airspeed. For the
gliders we are mostly used to and average sized and velocity gradient
thermals, 45 degrees is often about right. For a vintage type with a
stalling speed of 30 knots, circling at 30 degrees of bank, or even less,
at 35 knots may be better, for a heavily ballasted modern type, in a small
thermal, 60 degrees or even more may be best (better to dump the water
unless your pretty sure of finding bigger thermals later). How much bank
to use in a particular thermal is one of the most important and hardest
learned skills.

At 17:48 05 October 2013, son_of_flubber wrote:
>I know that a 45 degree bank is useful for flying small circles and
staying
>in small thermals, but is there something special about a 45 degree bank
>compared to say a 50 degree bank?
>
>For example, does the designer intend for the glider to do something
>special at 45 degrees? Is the glider designed to balance aerodynamic
>forces in a particular harmony at a precise 45 degree bank?
>

[son_of_flubber]

Thank you for the recommendations made here. I've just ordered copies of:

"Fundamentals of Sailplane Design" by Fred Thomas.

"Radio Control Thermal Gliding" by Markus Lisken and Ulf Gerber

Good reading for the winter ahead.

[Dan Marotta]

Maybe lots of inside rudder...?? ;-P


"Martin Gregorie" > wrote in message
...
> On Sun, 06 Oct 2013 08:15:31 +0000, Peter Higgs wrote:
>
>> Hi, there is a very descriptive book by Markus Lisken and Ulf Gerber
>> called Radio Control Thermal Gliding, that uses some very complex
>> mathematics to investigate the best possible thermaling practice.
>>
>> In it's comparison of various birds, it concludes that Buzzards are
>> better thermalers than Sea-gulls, because they have a lower Wing Aspect
>> Ratio (6:1 cf 12:1.) and are able to make tighter turns into the middle
>> of the lift. It quotes.. 'These wing shapes clearly show that a design
>> to give minimal sink in no way concur with a design for maximum climb
>> rate'.
>>
> I watched a medium sized buzzard-shaped raptor at Wiener Neustadt the
> other day as it picked up lift at 50-60ft over the apron and climbed
> away. It went up like a rocket in a very small corkscrew spiral, not more
> than 3 times its own span and using under 40 degrees bank.
>
> Try doing that in any current sailplane!
>
>
>
> --
> martin@ | Martin Gregorie
> gregorie. | Essex, UK
> org |

[Dan Marotta]

If you haven't already read it, you should also look at "Streckensegelflug"
by Helmut Reichmann:
http://www.amazon.com/Streckensegelflug-Helmut-Reichmann/dp/3613024799


"son_of_flubber" > wrote in message
...
> Thank you for the recommendations made here. I've just ordered copies of:
>
> "Fundamentals of Sailplane Design" by Fred Thomas.
>
> "Radio Control Thermal Gliding" by Markus Lisken and Ulf Gerber
>
> Good reading for the winter ahead.
>
>

[son_of_flubber]

On Sunday, October 6, 2013 1:47:40 PM UTC-4, Dan Marotta wrote:
> If you haven't already read it, you should also look at "Streckensegelflug"
>

Ich habe nur eine bischen deutsch.

[C-FFKQ (42)]

I get the 45 degree bank by looking at the screws of my instruments. Since the screws are placed in the "corners" of the non-existent square hole, the diagonals are 45 degrees to vertical/horizontal.

When I bank over, I check that a diagonal parallels the horizon (I'm a flat-lander) and the other is perpendicular. Easy-peasy!

Now, if I can just stabilise my speed and the angle, I might improve my thermalling. I keep working on that :)

[James Metcalfe]

At 20:38 06 October 2013, C-FFKQ 42 wrote:

<snip>Now, if I can just stabilise my speed and the angle, I might
improve my thermalling. I keep working on that :)

Actually, stabilising the attitude (not the speed) is what helps ...
although the two are very similar in typical flatland thermals.
J.

[David Salmon[_3_]]

At 17:48 05 October 2013, son_of_flubber wrote:
>I know that a 45 degree bank is useful for flying small circles and
staying
>in small thermals, but is there something special about a 45 degree bank
>compared to say a 50 degree bank?
>
>For example, does the designer intend for the glider to do something
>special at 45 degrees? Is the glider designed to balance aerodynamic
>forces in a particular harmony at a precise 45 degree bank?
>
The only thing I am aware of in relation to 45 deg of bank, is that it
gives the minimum height loss in a 360 deg turn. This is not of much help
in turns in thermals.
Dave

[Dan Marotta]

If that means you don't speak German, fear not. It's published in English.


"son_of_flubber" > wrote in message
...
> On Sunday, October 6, 2013 1:47:40 PM UTC-4, Dan Marotta wrote:
>> If you haven't already read it, you should also look at
>> "Streckensegelflug"
>>
>
> Ich habe nur eine bischen deutsch.
>

[Dave Nadler]

Silly Flubber. Everyone knows the special number is 42.

[Ramy]

One thing special about 45 degrees is that it is the only angle you can really measure in flight without artificial horizon. If the horizon is aligned with your instrument screws you are banked 45 degrees. You will often be surprised how steeper it is then you thought.

Ramy

[Dan Marotta]

Pesky mountains ruin the horizon so I can't use the screws. Maybe I should
move to Kansas. Steve...?


"Ramy" > wrote in message
...
One thing special about 45 degrees is that it is the only angle you can
really measure in flight without artificial horizon. If the horizon is
aligned with your instrument screws you are banked 45 degrees. You will
often be surprised how steeper it is then you thought.

Ramy

[Steve Leonard[_2_]]

On Monday, October 7, 2013 11:19:01 AM UTC-5, Dan Marotta wrote:
> Pesky mountains ruin the horizon so I can't use the screws. Maybe I should move to Kansas. Steve...?

Stick with New Mexico and the uncertainty of your bank angle.

[Evan Ludeman[_4_]]

On Monday, October 7, 2013 12:40:08 PM UTC-4, Steve Leonard wrote:
> On Monday, October 7, 2013 11:19:01 AM UTC-5, Dan Marotta wrote:
>
> > Pesky mountains ruin the horizon so I can't use the screws. Maybe I should move to Kansas. Steve...?
>
>
>
> Stick with New Mexico and the uncertainty of your bank angle.

Just send him a copy of "Condor" and a plastic joystick. That way he can be all trained up for when he eventually visits the flat lands.

-Evan (still cleaning that red stuff out of my trailer) Ludeman / T8