: Any plywood is going to be stiffer on it's own than pine or other
: similarly light weight wood of the same dimensions. The weight
: issue complicates things, though. Plywood will typically weigh a
: little more than pine or balsa or basswood, or cedar or any
: other similar wood of the same dimensions. The glass isn't going
: to add a significant amount of stiffness. Carbon fibre or kevlar
: would add more stiffness than glass will, but by itself
: fiberglass isn't very stiff at all. It's the wood that supplies
: the stiffness and the glass provides the resiliency/strength in
: the sandwiches that we use for boat building.

: The 2 layers of wood with 3 layers of glass/carbon would be heavier
: than one layer of wood with 1 layer of glass on each surface. If
: this is just for core stiffness, the single wood layer ply will
: be plenty strong enough to add the stiffness you need, assuming
: I understand correctly how you're planning to use it.

: As for a paddle, why not just make it hollow and fill with foam? I
: made a paddle of 2 layers of carbon fiber (12 oz I think) that
: is completely hollow and plenty stiff enough. I just layed the
: carbon around a pvc pipe that was waxed then pulled the pvc out
: of the tube once the epoxy cured on the carbon fiber. Strong,
: light and only cost me about $20 in materials (I used epoxy I
: already had on hand.)

: FrankP

Actually plywood would likely be less stiff since only about 1/2 the wood's grain runs in the direction of the stress, the grain running across the stress does little to add stiffness.

Bill H.