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Whats the difference?

Old 07-21-2010, 10:47 AM
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Steve Steinbring
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Default Whats the difference?

There some pilots here that separate sailplanes from gliders as different airplanes is there a difference? I did a little referencing and the words appear to be interchangeable what am I perhaps missing?
Old 07-21-2010, 11:03 AM
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Default RE: Whats the difference?



This is unofficial but the way I hear a lot of guys use the terms is sailplanes are unpowered. Whether hi-start, winch launched, or towed up.

Power pod stuff and such is refered to as gliders, some act as if calling a unpowered model a glider is an insult "Thats not a glider, thats a sailplane"
Old 07-21-2010, 12:32 PM
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Default RE: Whats the difference?



I subscribe to the Webster’s New World Dictionary definition of a sailplane as "a light glider especially designed for soaring." Calling a sailplane a glider is somewhat a put down especially when talking about gliders, visions of WWII troop carriers come to mind.



Allan

Old 07-21-2010, 12:35 PM
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Default RE: Whats the difference?

One other way I've heard it explained is as follows:

Either one can be powered to get to altitude, or use a winch, histart, etc.

A glider, is an unpowered aircraft that once at altitude is unable to sustain or increase the altitude by thermals, slopes, etc.

A sailplane, is an unpowered aircraft that once at altitude can sustain or increase the altitude by thermals, slopes, etc.

Is this right or wrong? I have no idea.

As a kid I flew full scale. The initial trainer was nicknamed "The flying brick" because when released from the winch, it was good for flying the airfield boundary. A glider for sure.
Old 07-21-2010, 01:10 PM
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mocgp
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Default RE: Whats the difference?

The word "glider" could be used to describe a Boeing 747 that just lost power to all 4 engines while in flight. The absurdity of using the word "sailplane" in the same situation helps define the difference.

In other words, I agree with kwmtrubrit's definition.
Old 07-21-2010, 03:00 PM
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Default RE: Whats the difference?


ORIGINAL: mocgp

The word ''glider'' could be used to describe a Boeing 747 that just lost power to all 4 engines while in flight. The absurdity of using the word ''sailplane'' in the same situation helps define the difference.

IF the flame out was due to lack of fuel, and it had no pax or cargo, I'd venture that a 747 that lightly loaded might just fly into the sailplane category
Old 07-21-2010, 03:31 PM
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Default RE: Whats the difference?

I believe that there is no big difference in using one or other word for any plane designed to have the highest possible Lift/Drag ratio.

The dictionary makes a difference regarding it being able to ride a thermal or slope draft resulting in a lift.

http://www.merriam-webster.com/dictionary

Sailplane
Function: noun
Date: 1922
: a glider of such design that it is able to rise in an upward air current

Glider
Function: noun
Date: 15th century
: an aircraft similar to an airplane but without an engine

It seems that a Sail-plane is given a similar capability as a canvas sail to substract energy from the wind, as the definition of sail implies:

Sail
Function: noun
Etymology: Middle English, from Old English segl; akin to Old High German segal
Date: before 12th century
1 a (1) : an extent of fabric (as canvas) by means of which wind is used to propel a ship through water (2) : the sails of a ship b plural usually sail : a ship equipped with sails
2 : an extent of fabric used in propelling a wind-driven vehicle (as an iceboat)

According to this, any "official sailplane" becomes a glider in any day with no thermal activity or weak wind at the slope.
On the other hand, any decent "oficial glider" can be a sailplane in a day with opposite conditions.

What my Gentle Lady is.......?[&o]

Old 07-21-2010, 08:01 PM
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Default RE: Whats the difference?

As long as we are debating the use of words, I would offer to Lnewqban that the correct preposition after the word "velocity" in your postscript is "at", not "in." The long form is "at a rate of."
Old 07-21-2010, 08:22 PM
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Default RE: Whats the difference?

Thanks!!!!!
Old 07-22-2010, 07:48 AM
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Steve Steinbring
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Default RE: Whats the difference?

So every sailplane can be a glider, but not every glider can be a sailplane
Old 07-22-2010, 11:58 AM
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Default RE: Whats the difference?

MajorTomski makes a valid point in that, under certain conditions, any aircraft may be able to achieve what we normally attribute only to "sailplanes", that is to overcome gravity without the use of any thrust. In terms of the 4 basic aerodynamic forces (thrust, drag, lift, and gravity), the flight characteristics of a GLIDER could be said to be those of any aircraft in a relatively level pitch attitude where thrust is at or near zero and gravity is greater than lift. The flight characteristics of a SAILPLANE, on the other hand, would be those of an aircraft where thrust is zero and lift is greater than gravity.

So, Steve, your statement is correct. I would alter it only slightly and say that ALL aircraft can be a glider. The fact that we have grown accustomed to using the word "sailplane" to typically describe unpowered, high aspect ratio, high performance aircraft is more a matter of semantics than anything else. If you want to avoid offending the "purist" then stick with the term "sailplane." I wouldn't get my nose out of joint if someone referred to my Windsong as a glider or my Sailaire as a sailplane. To me, each of them perform both functions equally well, with the possible exception of the aesthetic factor. (Not all will agree with the last statement - the Sailaire is often considered to be a beautifully-ugly aircraft.)

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