Glide Ratio & Scale: Designing Gliders for Maximum Air Time/Distance

[herpamad]

Hi

I am looking into the design of gliders with good L/D / Glide Ratio.

It seems hard to find what is the most efficient full size glider, and the same goes to a scale r/c type one too.

So any ideas?

If i was to start from scratch, what should i be looking at to get the best l/d ratio possible?

The AIM is to get the most airtime and/or distance.

I read in a book that speed has little effect on the L/D ratio, is this true? If so, is this only true down to a certain speed, ie, stall speed?

Project needs to address to if the aircraft can be used with a powerplant.

Is the use of a glider for adaption to a low power, and long distance aircraft better than building an aircraft from scratch for this purpose?

My area of study is Mech Eng, but I want to get into Aero Engineering after graduation, and i have an interest in fluids and aviation in general, thus having an Aero themed project to try get some knowledge about Aero Engineering.

 

[Filip Larsen]

Flying gliders but not R/C model I'm not sure what you ask. A modern glider has a glide ratio around 40-50 with the airspeed for maximum glide a bit above the speed for minimum sink rate, as calculated as the "tangent" from the glide polar [1]. The glide ratio do vary with speed, enough so that flying with the "correct" speed is significant in competition flights [2] and you would usually also correct for wind speed so that you fly a bit faster in head wind and a bit slower in tail wind.

I assume the performance of a R/C glider somehow can be transformed from the performance figures of a real size glider using the "standard" scale laws in aerodynamics, but I suspect "heuristic" knowledge about build and flying R/C models is far more important than general theoretical knowledge about aerodynamics.[1] http://en.wikipedia.org/wiki/Polar_curve_(aviation)
[2] http://en.wikipedia.org/wiki/Speed_to_fly

 

[Cyrus]

Hi

I am looking into the design of gliders with good L/D / Glide Ratio.

It seems hard to find what is the most efficient full size glider, and the same goes to a scale r/c type one too.

So any ideas?

If i was to start from scratch, what should i be looking at to get the best l/d ratio possible?

The AIM is to get the most airtime and/or distance.

I read in a book that speed has little effect on the L/D ratio, is this true? If so, is this only true down to a certain speed, ie, stall speed?

Project needs to address to if the aircraft can be used with a powerplant.

Is the use of a glider for adaption to a low power, and long distance aircraft better than building an aircraft from scratch for this purpose?

My area of study is Mech Eng, but I want to get into Aero Engineering after graduation, and i have an interest in fluids and aviation in general, thus having an Aero themed project to try get some knowledge about Aero Engineering.

Any aerodynamic behavior of a vehicle is a function of its angle of attack and sideslip. Airspeed does not dictate best L/D ratio, angle of attack does.

 

[herpamad]

Any aerodynamic behavior of a vehicle is a function of its angle of attack and sideslip. Airspeed does not dictate best L/D ratio, angle of attack does.

All i was wondering, thanks.

 

[alphy]

Hi there,

It's great to hear that you are interested in designing gliders for maximum airtime and distance. This is a complex and fascinating area of study that combines both mechanical and aerospace engineering principles.

To answer your first question, the most efficient full-size glider is typically the one with the highest glide ratio (L/D ratio). However, the design of a glider also depends on its purpose and the specific conditions it will be used in. For example, a glider designed for aerobatics will have a different design and glide ratio than one designed for long-distance flights.

If you were to start from scratch, there are several key factors to consider in order to achieve the best L/D ratio possible. These include the wing shape and size, aspect ratio, airfoil design, and weight distribution. It's important to also consider the materials used and their weight to ensure the glider remains light enough for maximum efficiency.

In terms of speed, it is true that speed has little effect on the L/D ratio of a glider. This is because the glide ratio is primarily determined by the shape and design of the wing, rather than the speed at which it is flying. However, at very low speeds, such as near stall speed, the L/D ratio will decrease as the lift generated by the wings decreases.

As for using a glider for adaptation to a low power, long-distance aircraft, it depends on the specific requirements and goals of the project. In some cases, it may be more efficient to design a glider specifically for this purpose, while in others, adapting a glider may be a more cost-effective option.

In terms of your interest in fluid mechanics and aviation, designing gliders is a great way to gain knowledge and experience in these areas. You will learn about the principles of lift, drag, and aerodynamics, as well as the importance of weight and balance in aircraft design. I would recommend researching and studying the design of existing gliders and conducting simulations or experiments to test different design factors and their impact on the L/D ratio.

I wish you the best of luck in your project and future studies in the field of aerospace engineering. It is an exciting and constantly evolving field, and I'm sure you will find it both challenging and rewarding.