Residual Elasticity (Part 2): Hammer5.8 (16x10 Proportional)

(Link to Part 1 is here)

Among all the strings I've tried, poly has the highest deformation factor. That's why tension loss for poly is always so high. Especially immediately after stringing!

To further test my theory on stringing based on residual elasticity, I will be stringing with used poly this time.

The used poly string will come from my Wilson Hammer 5.8 (link). It was strung a few months ago and should have seen at least 10 hours of play, maybe more.

My plan is to string 2-piece with poly in mains. The previous stringing pattern would give me plenty of extra string to play with. A new set of synthetic gut will be used for crosses. That would help me isolate any problems, if any, with the stringbed later.

Before re-use, the used poly was tested for its elasticity, resilience and deformation properties. The test results would determine the tension and stringing method to use.

To prevent unnecessary stress or damage to the used poly, I am using only both ends for testing since they will be trimmed after stringing. Each segment of string would be tested a maximum of three times with the lightest tension first and heaviest last. 

After I have arrived at my preferred tension, I will test the centre of the used poly string once to confirm consistency of results. This is because the centre of the stringbed suffers more ball impacts than the side strings.

Here's a pic of how a segment of string was marked, measured, clamped and tested. Two black dots (circled in red) marks the test length before, during and after tension was applied.

Here's two results (from the same string segment) which I felt were insightful:

Test1
Starting length: 20.1cm 
Length @ 45lbs: 20.8cm (after 1min)
Length @ 45lbs: 20.9cm (after 30min)
Ending length: 20.3cm
Elasticity @ 45lbs: (20.9 - 20.3)/20.3 = 2.95%

Test2
Starting length: 20.3cm 
Length @ 50lbs: 20.9cm (after 1min)
Length @ 50lbs: 21.0cm (after 5min)

Length @ 50lbs: 21.1cm (after 30min)

Ending length: 20.3cm
Elasticity @ 50lbs: (21.1 - 20.3)/20.3 = 3.94%

If you refer back to my chart on "Poly Stretch Test" posted in March 2013 (link), you can see that this poly starts stretching from about 45 lbs. The above test findings again confirms that.

One very important observation is the absence of additional string deformation at 50lbs after the 45lbs test was completed. Despite being re-used, this poly string stays resilient!

Thus, 50lbs was selected as the starting tension and proportional stringing was used, just like the PK Black Ace 98 (link). That's how much I like that setup!

Stringing pics below...

From the last pic, it is clear how the slick round poly mains "snap back" automatically whereas the synthetic gut strings lay crooked.

Playtest:
- It played very very close to the PK BA98 (link).
- From the first hit, it is very comfortable. There is absolutely zero trace that the poly was re-used! From my previous recollection of how the poly played when new, it felt exactly the same to me. Exactly.
- Directional control is good. But there is this same feeling of the ball "penetrating the cross strings gap" whenever I crank it up. It is not a serious mis-direction and happens only occasionally. Maybe it will go away in the second session like previously?
- Spin shines! Between this and the BA98 full syn gut, the spin levels appear very similar.
- Power level for this is slightly lower than the BA98 full syn gut. So it is very good for people who like to swing all out. The low-power and heavy spin would easily keep the ball in the court.
- I'll test it again in the next session and update later.

12Aug2013 update:
- Surprisingly, the ball "penetrating the cross strings gap" problem disappeared.
- Spin levels improved over the first session. Both serves and groundstrokes kicked up hard and fast. Slices skidded off the ground wickedly and forced my partner to scrap the racket against the floor just to return that shot.
- The used poly performed as well as, if not better, than a fresh set of similar poly string. I am thoroughly satisfied that it is possible to re-use strings as long as it is strung based on residual elasticity.
- The new synthetic gut cross string lost quite a bit of tension during play today. It started getting softer and softer. As crazy as it sounds, I prefer re-using used strings as tension holding is so much more stable.
- Similar to the PK BA98 (link), light notching can be seen only on the mains poly string. The crosses have absolutely zero notching so far. I find this strange as poly is so much stiffer than syn gut. It seems like tightly-strung syn gut could be stiffer than poly!