motorgliders as towplanes

On 19 Mar, 12:15, Bob Cook wrote:

Spoilers redistribute lift, but not reduce lift.

They reduce the lift over part of the wing. Whether the overall lift
increases, decreases or stays the same depends on what the pilot does.

Flaps change the coeffecient of lift, but not lift.

If you keep everything else the same then they do change lift. Every
tried dumping your landing flap just before the flare ...?

Q) *Two gliders, one is 40:1 racer and glider two is 20:1 trainer. Both
weigh 800#

Glider one has twice the lift of glider two. *True or flase and why.

Depends what they are doing.

Ian

On 19 Mar, 12:45, Bob Cook wrote:

Q) A glider is in circling flight. *The glider circles because there is a
horizontal component of lift. *This horizontal component of lift is
balanced by an equal and opposite force, centrifugal force.

True or False and why?

I hope you're not getting hung up on the old centripetal/centrifugal
debate. Centripetal force is just as real in a stationary axix system
as centrifugal is in a turning one!

By and large (ignoring a few second-order effects) what you wrote is
fine.

Ian

On 19 Mar, 16:39, Darryl Ramm wrote:

A glider "climbs" when you pull back on the stick and converts kinetic
energy to gravitational potential energy,

Technically that's a "zoom", not a climb.

The glider also
"climbs" - (maybe you should think of "lifted" if "climb" confuses
you) by a rising air mass and that does increase the glider's
gravitational potential energy.

But people keep telling me that it's conversion of PE to drag which
keeps the glider flying. How can that be happening when the PE is
increasing?

So how many ways do people need to keep answering the same pedantic
question you keep asking?

Well, some accurate ways would make a good start!

It amazes and depresses me how prevalent the nonsensical believe that
"gravity powers gliders" extends in the gliding world.

Do the ultimate thought experiment, turn off
gravity and the glider will just float along with moving air currents
but will be unable to glide anywhere.

Cars won't be able to work either, since no gravity = no weight = no
friction at the tyres. Would you say that gravity powers cars?

Ian

PS Thanks for your concern about my confusion. I don't really go in
for arguments from authority, but would it allay your concern to know
that I have taught and examined fluid dynamics at two major UK
universities for over twenty years?

On 19 Mar, 17:57, wrote:

Of course if you think about the analogy the energy for the whole
operation comes from the electric motors that drive the steps and
carry everyone's sorry butts to the next floor up. In soaring the
power is provided by the sun heating the air that rises (or forms
pressure systems that creates wind that flows over mountains). Gravity
and aerodynamics are just the way we turn that energy into a combined
forward and downward motion.

Give the man a coconut!

Ian

On 19 Mar, 17:20, Jim Logajan wrote:
The Real Doctor wrote:

On 19 Mar, 00:03, KevinFinke wrote:
Ian, "The Real Doctor" *Out of curiosity, what exactly do you have a
doctorate in?

Numerical solution of non-linear diffusion problems.Which is actually
a lot more interesting than it sounds.

I didn't know doctorates were awarded quite that way. I always thought they
were awarded in broad fields like math or physics or computer science.

Well, technically it's just a doctorate over here. It's the thesis
title and contents which matter.

Did you develop some new numerical techniques for such problems?

Yup.

Was your
work done in a math or computer science department?

Engineering!

Ian

On 19 Mar, 17:04, Jim Logajan wrote:

So what does power gliders? Seems like you are the only one who knows the
real answer.

The sun.

Also, initially, internal combustion engines, stretched rubber or, if
you buy an Electrostart and choose your contract carefully, nuclear
fission!

Ian

On Thu, 19 Mar 2009 17:00:04 +0000, Big Wings wrote:

Further to earlier post. Gravity is measured in Gals (in honour of
Galileo), 1 Gal = an acceleration of 1 cm/sec2. Average gravity at the
surface is 980.654321 Gals (or so). At the poles it is more at about
983 Gals and on equatorial mountain tops only 977 Gals - a difference of
about 0.6%. There are significant local variations. Now if we start to
take height into account...

I notice that's not an SI unit. Is the Gal some sort of engineering or
specialist geological unit? Its a pretty big unit for gravimetry, since
the maximal variation at the earths surface is only 6 Gals.

The SI unit is uM/s^2 (micrometers per sec squared), or 0.1 milliGals,
which looks more in tune with what satellites and aerial surveys are
measuring these days.

By the way, what happened to the discussion about slow tows?

Got too slow and stalled in.


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

The Real Doctor wrote:
On 19 Mar, 17:04, Jim Logajan wrote:

So what does power gliders? Seems like you are the only one who knows
the real answer.

The sun.

So you were being pedantic after all.

On Thu, 19 Mar 2009 13:09:30 -0500, Jim Logajan wrote:

You're claim conflicts with that in the FAA "Pilot's Handbook of
Aeronautical Knowledge":

"Found on many gliders and some aircraft, high drag devices called
spoilers are deployed from the wings to spoil the smooth airflow,
reducing lift and increasing drag."

Printing it in some official or semi-official publication doesn't make it
right.

There is a question in the UK Bronze badge written paper about the
proportion of lift provided by the top and bottom surfaces of a wing
that's just as wrong. The so-called "correct" answer is 70/30, but as a
wing is a device for imparting momentum to an air mass its a meaningless
question.


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

The Real Doctor wrote:
It amazes and depresses me how prevalent the nonsensical believe that
"gravity powers gliders" extends in the gliding world.

We all owe you a debt of gratitude for showing us how ignorant we are.

Cars won't be able to work either, since no gravity = no weight = no
friction at the tyres. Would you say that gravity powers cars?

I think pedantic trolling powers cars:
http://blog.modernmechanix.com/2008/...-makes-85-mph/

I don't really go in for arguments from authority, but

I removed the contradiction in order to protect small children.