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

[Moomba]

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 ?)

 

[HallsofIvy]

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 4^3= 64 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.

 

[RandomGuy88]

(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?