Simple summer raspberry question.

Try this for size
http://www.bbc.co.uk/programmes/p00k603t

Tie them up how you want, but it's a nice pic for spacing, and how much he's cut off 

I've never measured them but assumed they do. If you look at a second year cane the surface looks as though it has split in various directions one layer a a time them dries and peels off.  I assumed this was where the surface dries and 'dies' then as the cane swells it splits that surface layer and another layer then becomes the surface. Akin to the surface of a tree like silver birch.

i think they do swell but not a huge amount, not like a tree. i leave my ties loose, just tie them above a branch and they will sit there nicely.

i tie mine individually using strands of telephone wire which is stiff but thin copper covered wire, because it's single strand stiff copper you put it round what your tying and put a couple of twist in and it stays as it is. no tying and you can re use them for 3/ 4 years until the plastic coatings breaks up.

i have found using nylon string before that the prickly stems can blow around in the wind and leave the string frayed and looking like a birds nest. maybe this doesn't happen with twine or if you tie them tight.

i think they say thin out to 3 canes to 1 plant, removing the weaker ones and keeping the stronger healthier ones.