I'm generally not a huge picture taker - will get some up on a separate topic in the not so distant future, some of the workshop, stickers and setup etc. don't want to hi-jack tims thread though. Be interested to hear Tims theory on why he is doing this....is there method behind the madness?
From discussions with various people, willow in a bat is effectively a hard trampoline layer with a drum underneath it created by the tubes that are the fibres of the wood. In a more dense cleft, these fibres a presumably smaller and more tightly packed.
Conservation of momentum is achieved transferring energy on impact.
Theoretically, two bats of similar weight and with a profile that is consistent should allow this to take place in a similar fashion, but in doing this we get to find out whether cleft density really is important in bat performance because if we are taking a very extreme version of dense, and it performs then we know that bat (and therefore swing) weight is more important than the willow.
of course, pressing is important in this and the pressing on the cleft needs to be what the batmaker considers to be optimum .