High aspect sail ratio

And I don't see any point that a ketch couldn't be high aspect and many of them are..

 

Of course your observation is correct. Aspect ratio, in my simple mans terms, is the relationship between mainsail hoist and mainsail foot length. The very best ketchs are indeed high aspect ratio , with maximum separation between main and mizzen.

For practical reasons most ketch's I see are lower aspect ratio. They choose a split rig for air height considerations. 65 ft is the number on the east coast of the US...30 meters is the number in Europe. These vessels will be long on the mainsail foot and short on hoist.

 

I'd like to raise a question. Are you talking about main or headsail?
Old masthead rig had high aspect main with low aspect headsail, as you all know these boats carried large overlappers.
Modern boats have relatively low aspect main with high aspect headsail. Originally this fashion was started around mid 80's when IOR preferred fractional rig for rating advantage.
After the death of IOR, newer rating system like IMS, ORC and IRC are promoting fractional rig.
A great number of production builders noticed this and they started building boats with fractional as these are much more user friendly (Easy to tack). Nowadays a considerable number of mass production manufacturer build boats with non overlapping headsail. This type of boats have shrould chainplates nearer to gunwale so can reduce compression to mast tubes which means they can use smaller mast section. Cheaper!!

 

Sounds logical. Perhaps the fortriangle , overlapping sails, comes into terminology. I don't know. I only comment as a user, not a designer. My eye spots aspect ratio as length of boom... mast height. A traditional gaff rig being low aspect.

 

Also helped by new technology especially sails.