Some observations to herd the previous posts into one paddock -
(a) increased mass has the same outcome as increased g so far as the wing looks at weight. Our unfortunate and relaxed use of "weight" when we really mean "mass" is a source of great confusion for many folk.
Recall from basic principles of flight classes (a long time ago) that W = mg, so that, if the net m, and/or g value varies, then W varies.
(b) at the stall (Vs)
CLmax = lift / (― ρ Vsē S)
which can be simplified to
CLmax = lift / (k x Vsē)
if we lump the other factors sensibly together as some constant (k) for the one aircraft and altitude.
We can get rid of the k constant by talking in terms of proportionalities and simplify the equation to
CLmax ≈ lift / Vsē
If we further constrain altitude to be constant so that lift = weight (KISS principle), then
CLmax ≈ weight / Vsē
If we presume CLmax (ie stalling CL) to be a constant, which is reasonable for a given aircraft (and configuration) at a given altitude, then
Vsē ≈ weight
as we can lump the CLmax value (just another number) in with the k and get rid of it as well for proportionality considerations. So now, if we vary weight (ie mass, or g),
Vs ≈ √ W
We use this relationship by comparing two different cases -
Vs2 = Vs1 x √ (W2/W1)
In the real world we need to apply PECs and figure the sums in CAS rather than IAS otherwise all bets are off. This presumes nil instrument error and we can ignore compressibility effects for typical situations.
So, for example, if level stall (presumed at 1g) occurs at 52 KCAS for 1200 kg, we would expect the stall at 1500 kg to occur somewhere near
Vs = 52√(1500/1200) = 58 KCAS
As an aside, if you think back to principles of flight, you probably looked at n-g diagrams which have curved stall lines at the low speed end for positive and negative g loads. The curve is just the equation above.
If you are uncomfortable with the sums, we can describe what happens in the following way
(a) weight (strictly mass) variation is similar to g variation, so far as the end "weight" is concerned
(b) for all intents and purposes, stall speed varies with the square root of the weight variation
Hopefully I haven't just confused everyone more than they were at the start ?
It is important to keep in mind that PECs can go a bit strange post stall.
As a consequence, when we play test pilot at the flying school with a small Cessna and the IAS goes off the clock (indicates something approaching zero ?) in the stall, that "observation" is more about PEC than the actual speed (which is definitely not zero) of the aircraft through the air.