Same speed for same wing loading?

[S55]

Assuming everything else is equal (in fact proportional), is it true that a bigger plane with the same wing loading as a small plane will be able to stay in the air at the same speed as the smaller one?
I would go bigger in size just to be able to take off and land on grass, but I do not want that big plane if it needs to fly at higher speed.

Thanks,
S55

[Basketcase]

Yes it is true. :) A big plane with the same wingloading will be able to fly slower than a small plane with the same wing loading.

For example, my 65.5 oz. Banchee with a 12.5oz/sq. ft. loading can fly slower than my 16 ounce Steven's Cap 232 that has a loading of 11 oz/sq ft.

BC

[DLC]

As long as you keep the same airfoil and wing loading, the scaled up plane should fly at pretty much the same speed as the smaller plane. Be sure to check the weight, since weight and size typically don't scale the same, particularly if you have to use a bigger motor, bigger battery, etc. with the scaled up plane.

[S55]

That is good news. I was afraid it has to do with the Reynolds number and the flying speed would be the same when expressed in number of chords per time unit.

S55

[DLC]

There will be some Reynolds Number effects, but unless you are doing some really major scaling, they should be second order effects. There will be more drag because of the increased wing and frontal area, so you will have to go to a more powerful motor or lose some perfomance.

[BMatthews]

Depending on the airfoil and how the wings are constructed it's possible that the larger airplane will actuall stall at a lower airpseed than the smaller one. THAT is due to the effect of using a wider chord wing that is operating in a more efficient manner.

That rise in efficiency is connected to the scaling effect and is related to the rise in the Reynolds number thanks to flying the wider chord at the same airspeed.

But if you're only making a slightly larger model that works with the same motor for both designs then the best action is to make the big model lighter in construction so the larger model weighs the same as the smaller one so the wing area is less. For the scale effect to make a significant difference the size increase needs to be at least 1.5 times or you won't really notice anything if they are flying at the same wing LOADING.

[S55]

I cannot make the same model bigger and keep the same total weight, but most likely I can get the same wing loading. The motor and battery would be sized for more power too. The size increase I am contemplating is to go from 40 inch wingspan to 60.
S55

[edfardos]

another way to think of it, is that, instead of changing the scale of
the plane, you could change the density of the air - taken to the
extreme, with air as dense, as say, water, you can move through
it much slower and still maintain level flight.

[Tom Harper]

S55,

For a span increase of 1.5 the weight can be multiplied by 2.25 and the wing loading will be the same. The velocity should decrease to 80% of the original but it will require about 3 times as much thrust to get there.