Proportional Stringing Using Full Poly

Having tried many variants of proportional stringing (link) successfully, I became a believer. 

Of course there are pros and cons, but from my experience, proportional stringing worked great to enlarge the sweetspot, add power and heaps of comfort to any racket.

However, my success was limited to synthetic gut. Given how passe synthetic gut is now, it is difficult to convince anyone to try proportional stringing with it. 

Strangely, the greatest dislike of synthetic gut, was string movements. Not the lack of spin, since almost everyone who tried, commented spin was similar to their full poly setups!

The basic premise of proportional stringing is managing string elasticity. When tensioned equally, for example at 50 lbs, the shorter strings in the racket would always feel tighter than the longer strings. The difference between mains and crosses is often quoted to be in the 25-35% region.

With synthetic gut, it is easy to string proportionately. Just measure the lengths of every string, select a base tension, then apportion it based on string length. The average 10% elasticity of synthetic gut is wide enough for small differences in tensions to be felt.

With poly strings, it is a different story due to their very narrow elastic range of about 2-4%. As a result, even when strung proportionately, the reduced tension is insufficient to add enough elasticity to the shorter strings. My testers and myself could not feel any difference during playtests.

After many failures, an eureka moment suddenly came! I added a "string elasticity factor" to widen the tension gap, and thereby widening the elasticity gap as well.

For example, if a poly string's elasticity is about 3%, and the player wanted to increase forgiveness, I could add a string factor of about 1.3. When applied to the string lengths and tensions, it would look something like:

Without String Elasticity Factor
30cm --> 60 lbs
20cm --> 40 lbs (20/30 x 60)

With String Elasticity Factor of 1.3
30cm --> 60 lbs
20cm --> 34 lbs [30-(1.3 x (30-20))]/30 x 60

(Round to the nearest lbs)

Correspondingly, to tighten up the control of proportional stringing using high elasticity strings like multi or synthetic gut, I would use a string factor of below 1.0 to narrow the gaps.

Since every poly has different elasticity and a distinct elasticity curve, coupled with the player's unique hitting pattern, it took a few attempts to get the factor right. 

But once it was ascertained, a competitive junior remarked that "he was in poly heaven". Others described it as "incredibly soft and comfortable" and "powerful and very spinny".

With the factor applied, some of the shorter strings could end up at a ridiculous 10+ lbs. To prevent that, you can make your own adjustments to the string factor, or set a minimum/maximum tension. Also, a gentle pre-stretch would eliminate the string buzz often found in very low tensioned poly strings.

That said, it still does not negate the fact that most polys are harsh and need to be restrung after every 8-10 hours of play, or less.

And by the way, Tim, to answer your question, this was exactly how your racket was strung with full poly.