Originally posted by dick Hanson
He asked and you answered in a clear, concise manner -
I do have a question tho --
How relevant is boundry layer at the speeds this scale B25 will be seeing-wich I am guessing will not exceed 100 MPH.
Revelant to what? If you mean relevant to your set of values about scale models, I would guess that reynolds number is not all that relevant. If Bill has a problem with too high a landing speed then maybe it is of some small relevance. If Bill wonders why he can't get the B25 model to fly at a scale speed, the high wing loading and a poor airfoil selection are at fault. The boundary layer has a significant affect on airfoil performance. So much so that it is best to select different airfoils for the tip and root of a wing with a lot of taper. Some airfoils for tails have a jog in the coefficient of lift versus angle of attack curve that results in symptoms of a one or two degree dead band in the control response which is caused by laminar seperation bubbles of the boundary layer shifting from one side to the other when the airfoil pases through zero angle of attack. Some people might think this significant, others not.
On a model of this size -at what speed does the boundry layer start to make a significant change in how the model flys.?
Its hard to say because various people will have various ideas of what is significant. Generally speaking, reynolds number effects change slowly with changes in reynolds number but, at model sizes and speeds they change faster than at full scale and the smaller and slower the model the more pronounced the changes with changes in reynolds number.
At sea level. (STP)
Did I ask the question correctly?