However, I wanted to calculate how wide that boundary layer really is.

The calculation for boundary layer thickness is:

ẟ / x = 5 / (√R)

ẟ = boundary layer height

x = length from nosecone tip to fin

R = Reynold’s number

Fortunately, Open Rocket can calculate the Reynold’s number:

At launch, it appears that the Reynold's number is 1,000,000.

x = 355 cm

R = 1,000,000

ẟ / 355 cm = 5 / (√1,000,000)

ẟ = 355 cm * (5 / (1,000)

ẟ = 1.8 cm

So that means the boundary layer is only 1.8 cm.

I did some reading and see that aerodynamic rockets do have very high Reynold's numbers of 10

^{5}to 10

^{8}range, so I'm in the right range.