Engineering and Scaled Prototypes

[mnowaczewski]

Trying to grasp a handle on the concept of scaled prototypes.

Is it possible to use a scaled prototype during the research and design of an aircraft to gather accurate data on how the full-scale model would behave?

For instance, say I have an R/C airplane that has an endurance of 3 hours under x circumstances.

Can I then use some math to accurately say based on the results of this smaller scaled model -- the full scale model would need to increase wing area by x and thrust by x and fuel (gallons) by x...etc to have the same endurance and payload capability (since the model could lift 3 pounds, a full scaled model could lift 3,000 pounds).

Some guidance on literature for this would be great too.

Also, would the airfoil characteristics remain the same apart from the fact that it has to be bigger?

 

[Hlynkacg]

Also, would the airfoil characteristics remain the same apart from the fact that it has to be bigger?

Yes, this is actually the primary use of scale models in aerospace testing.

 

[jangofett287]

Almost, but you will run into the snag that when you double somethings size, its surface area is squared and its volume is cubed. However the aerodynamics remain the same, as they are related to the shape, not how big it is or what its made of.

 

[mnowaczewski]

Thanks for the quick replies... How then could someone look at a model and determine the final product will have an endurance of x and capable of a max payload of x pounds ...

 

[Hlynkacg]

Hard to say as the mass, propulsion system, fuel, and subsystems would also have to be to scale.

For obvious reasons this is unlikely to be the case.

 

[RisingFury]

Short answer: No.
Long answer: Yes.


No, you can't *simply* scale things up. Generally you'll find larger models to be much more stable then smaller ones. The biggest role here is the Reynolds number:
[ame="http://en.wikipedia.org/wiki/Reynolds_number"]Reynolds number - Wikipedia, the free encyclopedia[/ame]

Thanks for the quick replies... How then could someone look at a model and determine the final product will have an endurance of x and capable of a max payload of x pounds ...

That's very difficult to say... as you scale airplanes, various ratios change. Weight per area of wing, thrust to weight for the propulsion system, thrust to drag,... so on.

There's no simple formula used for scaling up...