I still don't see how Greg and ArtArt can both be right. Nobody has explained how with a weight of about 364g, the SW can be 355 on such a HL racquet?
My friend can't weigh his racquet (no scales, but it's probably about 364g anyway) and can't measure SW. However he has checked under grommets/bumper at top of racquet and there is one layer of very thin lead across the top 10 grommets (on both sides), about 5" or 12cm each side, which I guess would only be about 3g in weight. He also carefully looked under overgrip, and it is a P1 leather grip underneath not Wilson!
So along with balance of 32.1cm, that's all the info I can get on this Federer K90 racquet. Am looking forward to seeing balance of Fabfeds 4 racquets.
Thanks in advance Fabfed, and I hope you enjoy the Grand Prix
If we take a stock K90 that comes on "on-spec" we have (unstrung):
Static weight: 340 grams
Balance: 30.5 cm
Swingweight: ~308 (this is derived from TW's 6-frame average, minus the ~15 gram stringjob they put into their demo/playtesting frames)
We then add 16g Natural gut mains and 16L Alu Rough crosses, which weigh about 17 grams in a mid (including his 10 string savers). The center of the stringbed is 21" inches from the butt, and using the TW University Customization Worksheet (
http://twu.tennis-warehouse.com/learning_center/customizationReverse.php) we can add that string weight and get:
Static weight: 357 grams
Balance: 31.6 cm
Swingweight: ~339
Then we add the 4 gram overgrip:
Static weight: 361 grams
Balance: 31.35 cm
Swingweight: ~339
Then we add the 3-5 grams at 12 o'clock that P1 puts under the bumpers to match the frames and reach Fed's target swingweight (lets do 4 grams):
Static weight: 365 grams
Balance: 31.7 cm
Swingweight: ~352.5
So we're very close to the 364 grams FabFed has reported, and also very close the the 354 swingweight that Art Art has reported. Our modded K90 is slightly more headlight than the 32.1 cm you reported. But that can easily be explained by the custom handle and custom leather added by P1. If those two things are slightly lighter than the stock equivlents, P1 could get to 364 grams by adding several grams at the top of the grip, which would raise the balance by several millimeters (weight at the top of the grip moves the balance down less than the same amount in the middle of the grip). Alternately, the frames chosen for Fed could be a bit less headlight than Wilson's target spec for the K90 (30.5 cm unstrung). (Actually, most K90s are several millimeters less headlight than that target spec.)
(BTW, most modern racquets can have a high swingweight and a short (headlight) balance. You just add weight to the butt, polarizing it. The K90 is moderately polarized in stock form. This is done with the lead bars Wilson places inside the butt of K90s, about a half inch from the end of the handle; dig through the foam a bit and you'll find them. For example, If we put 34 grams in the butt of Rafa's racquet (350 swingweight) to match Fed's 364 gram static weight, his APDGT would balance at 30cm (14HL)!)
I think Greg Raven's Fed K90 lacks the lead at 12 o'clock that P1 adds (thus, the 338 swingweight, rather than 350+). Raven's frame came from the Wilson War Room, not from P1, so it probably doesn't have P1's custom handle or leather either.