Road Cycling - A cross-chaining question

I am (not so patiently) awaiting my new bike. The one with a Campagnolo Daytona - perhaps Centaur at this late date - Racing T 9s setup on it. It is a 30-40-50 x 13-28.

Specifically, if one can be that specific, how many sprockets must I avoid with each chainring? I have heard various numbers, usually 1 or 2, for the inner and outer chainring, and no numbers for the middle.

I realize that it is a function of chain angle between front and rear gearing, along with chain width, etc. But is this a given quantity based simply on the specification of the gearing? If so, what are the real numbers for this setup? If not, what factors help determine the real numbers (distance from chainring center to sprocket center, for example)?

Any and all help is appreciated.

Thanks...Gary

Gary,
I have always understood that the 2 biggest cogs should be avoided with the big ring and one on each end for the middle. I have seen a couple of different ideas on the small ring. One is to avoid the 2 smallest cogs, the other to only use the small ring with the few largest cogs. Physially, you can pretty much put together any combination. The combinations to be avoided just put unnecessary stress on the chain. There is no need to use the extremes since the same gear inch combinations are available with less extreme angles. I make it a practice to follow the above recommendations and use the small ring only with those four or so largest cogs, which is almost never around here.
Regards,
Raymond

Hi All, *S*
I have a seven speed cassett with a nine speed chain. It is nice and quite and I can use all my gears. I dont as a practice but its handy when I need it.

Ride Safe.....Dudley