How do I calculate scale weight for testing a scale glider?

In summary, when creating a scale model of a glider to test glide ratio, the weight of the model should be 1/64th of the weight of the full scale design, which in this case would be 1.5625 kg. Additionally, the scale speed should be increased by a factor of 4 to properly reproduce the aerodynamics of the full scale design. This is based on the principle that weight is proportional to volume, which scales as the cube of length, and speed scales the same way as length. The Reynolds number should also be considered when determining the scale speed.
  • #1
Moomba
1
0
Hello all - I'm new to the forum - I hope some kind person can help with a question of calculating scale weight in a scale model of a glider.

I want to test the glide ratio of a glider design by making a 1:4 scale model and thowing it from a certain height at a certain speed and measuring how far the model glides.
Suppose the design has 10m wingspan and the model has 2.5m ws.
The question is: if the full scale design weighs, say, 100kg (including pilot) what should the 1:4 scale model weigh?

(And, I'm supposing that the scale speed should just be reduced to 1/4 ?)
 
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  • #2
Typically, weight, being proportional to volume scales as the cube of length. If typical lengths on the actually glider are 4 times the model lengths, then its weight will be [itex]4^3= 64[/itex] times the model's weight. If the full scale is 100 kg,the model should weigh 100/64= 1.5625 kg.

Yes, speed= length/time and, since time is not scaled, will scale the same way as length.
 
  • #3
Moomba said:
(And, I'm supposing that the scale speed should just be reduced to 1/4 ?)

Actually to properly reproduce the aerodynamics the speed would have to be increased by a factor of 4. Are you familiar with the Reynolds number?
 

1. How do I determine the weight of my scale glider for testing purposes?

To calculate the scale weight of your glider for testing, you will need to first determine the scale ratio of your model. This is typically listed as a fraction, such as 1/4 or 1/6. Then, you will need to multiply the actual weight of your glider by the scale ratio to get the scale weight. For example, if your glider weighs 10 pounds and the scale ratio is 1/4, the scale weight would be 2.5 pounds (10 pounds x 1/4 = 2.5 pounds).

2. Do I need to take into account the weight of the materials used to build the glider?

Yes, the weight of the materials used to construct the glider should be included in the overall weight calculation. This will ensure that the scale weight accurately reflects the weight of the completed glider.

3. Can I use a digital scale to measure the weight of my scale glider?

Yes, a digital scale can be used to measure the weight of your scale glider. However, make sure to calibrate the scale beforehand to ensure accurate measurements. It is also recommended to use a scale that can measure in grams or ounces for more precise readings.

4. Is there a specific weight limit that my scale glider should not exceed?

There is no set weight limit for scale gliders, as it can vary depending on the size and design of the model. However, it is important to keep in mind the weight of the glider in relation to its wingspan and overall size. A heavier glider may require more power to fly and could affect its performance.

5. How often should I weigh my scale glider for testing purposes?

It is recommended to weigh your scale glider before each flight or at least once a week if you are actively testing and making changes to the model. This will help you keep track of any weight changes and ensure that your glider is within the desired weight range for optimal performance.

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