Quote:
Originally Posted by kach22i
With all due respect Charlie I have stated the full sized template works as a stand alone entity, but is not the tool needed nor promoted in this forum by it's developers and their following.
I have stated many times in many ways that scaling down the template is scaling down success, and I suspect that there is a mathematical factor which can be applied to this.
I have suggested that a 3D boattail template/tool be develop to retrofit to existing cars/trucks and made suggestion as to what it may look like in cross section and so forth, therefore I have done much more that criticize - read up.
I admit that I need to learn more on the scaling of models (not doing any model testing at this time), however very few things posted in the forum lend a clue. The comment that a 1/6th scale model would need to be doing 120 mph means what exactly? An intriguing comment, one which I appreciate but no context or comparisons to add value or pattern. 120 mph verses what other speed of the full scale body, 20 or 250 mph? No clue, sorry if I missed it. Is the air going to detach on the scale model before the full scale model? Now that would be useful information and make some sense. Crickets.
I understand that one cannot fit a square peg into a half circle hole, which puts me one up on you Charlie - your emotions on this topic have blinded you to the painfully obvious.
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The drag coefficient will not stabilize until the body reaches a critical Reynolds number which forces transition to the turbulent boundary layer.
Reynolds number is a function of body length and velocity with road vehicles.
*For a full-scale vehicle the critical Rn will occur at 20 mph.
*For a 1/2-scale 40 mph.
*1/4-scale 80 mph
*1/5-scale 100 mph
*1/6-scale 120 mph.
Aerodynamicists use the term verisimilitude to describe the necessary relationship among scale-models with which to produce an Rn which will produce meaningful data.
freebeard just posted a link to Suzuka's wind tunnel work which covers this phenomena.