In that case, I will dig back into the past.

Actually meant that the grains were diagonal rather than the plys cut across the sheet.

Pete

I recall reading an article in Modern Drummer about 20 years or so ago about Sonor that said that they form their shells "tension free", and I believe it was stated that it was because all of the grain ran in the same direction (vertical).It was referring to the Signature series.

Hey Peedy;

Yes, I took it as you meant that the grain direction of the plies ran diagonal. (I still can't figure out what you meant by "parallel diagonal"...) I was just trying to explain to you that that is not what was happening in the Sonor vid that you pointed me to. I am sorry to have to keep pounding away at this but I would really like to know if that type of shell ever existed. I find shell construction very interesting because forcing wood into round, and keeping it that way, is one of the most difficult tasks to accomplish in woodworking. Wood wants to stay straight, we want it to curve, the battle rages on....

ps, we started discussing Premier shells, how did Sonor get mixed up in this?

8upwithit;

Welcome to the discussion!

Sonor to this day still produces their shells using their "Cross Laminated Tension Free" system. Once you remove the marketing wank, it is basically the same way everyone else produces shells. The one exception I can think of with ply shells is DW's xlt line, which runs some plies diagonal. The important part is that there is still a change in grain direction throughout the plies to supply stability to the shell. If all the grain runs in the same direction there will be twisting during expansion and contraction. When building a shell, we want the forces of expansion and contraction minimised. Cross lamination accomplishes this, having the small amount of force from one ply counteracted by the force of the next ply running perpendicular to the first. Those forces basically cancel each other out, (this is where the "tension free" part comes from), helping the long term stability of the shell. If all the plies run the same direction, they all expand and contract in the same direction, most likely not at the same rate, leading to delamination, cracking and basically just pushing and pulling itself apart over time.