My outlook on this is colored by my being at this point a lighter weight skier (c. 150 lbs/5'10"), and the fact that these days I almost always prefer skis that are a size or two longer than those charts or my weight alone would suggest.
In general, I agree with @HardDaysNight that skill level is the most important factor. I like his example of a smaller but skilled woman liking a much longer ski than many much larger men would find useful.
Also, the properties of the ski itself, and of what you want it to accomplish, often come in a strong second. For example, the 188/30 FIS GS race ski feels more fun and just as easy to me as the 183/30 or older 183/23, irrespective of length.
For another example, I'm a lighter weight guy, but with the right skis, for fore-aft stability in resort powder, I'm likely to often prefer the longest ski the company makes: 189 to 191, especially on wet snow days (like yesterday here!!), deep chop days, windblown days or even refreeze days. Modern ski developments make this possible, I gather. In powder and crud, the things feel shorter and easier to handle just because of stability and great design. And I'm into "easier."
Third, @Noodler 's elegant Center of Mass explanation (taking into account height with weight) sounds good to me. My example here is that the ski lengths I usually like best have seemed in line with my height more than with my weight - more with my CM.
In practical terms, picking the skis and ski lengths that work best, or are likely to work for others, I like to go mostly by experience, past and present. Therefore, I - and many others - demo, at different lengths and with different skis, every year. And there are lots of surprises, especially if I base expectations on past experience/conclusions I've so far drawn on, let alone theories based on physics.
I'm not saying physics doesn't apply here, or isn't useful: just that there are a whole lot of variables, many of them mostly unknown. For most skiers, it's more of a dance or art than a ski design/build project.
In general, I agree with @HardDaysNight that skill level is the most important factor. I like his example of a smaller but skilled woman liking a much longer ski than many much larger men would find useful.
Also, the properties of the ski itself, and of what you want it to accomplish, often come in a strong second. For example, the 188/30 FIS GS race ski feels more fun and just as easy to me as the 183/30 or older 183/23, irrespective of length.
For another example, I'm a lighter weight guy, but with the right skis, for fore-aft stability in resort powder, I'm likely to often prefer the longest ski the company makes: 189 to 191, especially on wet snow days (like yesterday here!!), deep chop days, windblown days or even refreeze days. Modern ski developments make this possible, I gather. In powder and crud, the things feel shorter and easier to handle just because of stability and great design. And I'm into "easier."
Third, @Noodler 's elegant Center of Mass explanation (taking into account height with weight) sounds good to me. My example here is that the ski lengths I usually like best have seemed in line with my height more than with my weight - more with my CM.
In practical terms, picking the skis and ski lengths that work best, or are likely to work for others, I like to go mostly by experience, past and present. Therefore, I - and many others - demo, at different lengths and with different skis, every year. And there are lots of surprises, especially if I base expectations on past experience/conclusions I've so far drawn on, let alone theories based on physics.
I'm not saying physics doesn't apply here, or isn't useful: just that there are a whole lot of variables, many of them mostly unknown. For most skiers, it's more of a dance or art than a ski design/build project.
