i come back from vacation, and what do i find? more r.b.t. ridiculousness. viz: Mark Hickey wrote: > I'll bet you $1000 that, all other things being equal (OD, wall > thickness at the ends) that a straight gauge 3/2.5 tube IS stiffer > than a butted 6/4 tube. a "bet" on something you could instead calculate? that's illogical since you don't bother to define all relevant terms leaving me to specify my own butted tube wall thickness. i could therefore trade the different modulus for the two materials and specify butting thickness that would win that "bet". and all this is ignoring the fact that the majority of the stiffness you're trying to sell me is needed in the joins since that's where the majority of stress is concentrated. since you /do/ specify the same thickness for the two different materials in this region, the higher modulus tube "wins" again. it's ridiculous to "bet" without bothering to properly define terms. i suggest you deploy your money for something useful [like a book, which you bother to read] and some test gear, something you so diligently avoided earlier and from which you as a "manufacturer" would substantially benefit.