I'm an engineer, but I skipped the fluids course, but now regret that.
As a cruiser, I like the fractional rig for practical reasons. Usually, the mast is further forward, allowing the boat to balance reasonably even with the jib rolled up. Small jib is easy to tack, a bigger fully battened main is easy to handle, you can hold a full jib into an increasing wind while reefing the main only (partially rolled jibs usually don't hold their shape well), the boat will sail to windward on main alone when short tacking allowing someone to easily work the foredeck to get the anchor ready or grab a mooring, and a furling code zero (a super easy to deploy light wind sail for cruisers) can be launched easily in front of the rolled up jib.
I read a little about Bernoulli and Reynolds numbers, but cannot remember any of it
There is no need to review Bernoulli, Reynolds or even Prandtl, etc. All you have to do is keenly observe
that most frac rigs (compared on an equal/similar basis) overwhelm
masthead rigs when going to
weather; and on the 'down side' the very same frac rigs will invariably use a spinnaker to beat the pants off a masthead (using a large LP genoa) 'going down'.
Such kind of strongly suggests that a masthead rig is only
a compromise ... using the BIG jib/genoa instead of a 'proper' downwind sail and at the expense of 'pointing ability' for going uphill, to boot. It also suggests that the 'aerodynamics' of sailing more or increasingly 'optimize' with the fractional rig.
No 'iterated numbers' or 'theories' required, the 'ratings' databanks, the compilation of racing result over many many years seem to confirm this; all the while, the 'modern' (post ~1903) theories of aerodynamics help to explain 'why' that is.
All this stated, I still dont want an overly-tall rigid wing-sail on my crab-crusher 'Perryboat', thank you. But yet, I still fly a staysail 'under' a yankee topsail, as the speedo results show an increase of forward speed & VMG when pointing with this 'combo' .... and even that the staysail doesnt visibly seem
to be 'drawing' - thanks to modern theories of aerodynamics.