: Don, I can now see that you are more serious about this than what I might be.
: Doing full length cores under the assumptions you list gets pretty close
: to actually breaking real paddles. Are you perhaps also including one with
: 1/4" core and 3/8" cap strips? Weighing them all before breaking
: them... you'll get really interesting data!

I could try that Risto, but intuition tells me that adding width to the cap strips would add weight to the paddle. The sum width of 1 core strip ( 3/4") plus two caps ( 1/4" each) is the loom width - 1-1/4" in this case. Ive been using a 1-1/8" loom, that seems to be the general concensus of 'favorite' among people who have tried them. So that a 3/8" cap strip would only leave a 3/8" hollow.

: It might turn out that hollow ones of equal weight are no weaker than their
: solid counterparts... at least this is what I would put my money on (but
: not much of it! ). But like you said, how much lighter can they be,
: that is the question!

The heaviest of the hollow cores are coming in within an ounce or two of the lightest of solid paddles. But I think the holow ones are quite a bit stronger - these are the two that have 4oz glass inside. One is Tims if he wants it, and the other goes into the break test.

I hope the results come in that the cores Ive been making, with no glass, which are anywhere from 2 to 6 ounces lighter than solid core, will turn out just as strong or stronger.

Digital scale - tops on my list of purchases. Hopefully next week. With that, I should soon be able to predict a finished paddle weight based on dimensions and materials.

Flexibility is a different property, based on the properties of the woods. Oddly, the two paddles I have with glass inside dont feel much, if any, stiffer to me. Added to the fact that the most flexible paddles I have ever built had 1/4" thick blades with 'glass on the outside of them, up 2/3 of the way to the loom, indicates that glass/epoxy is at least as flexible, if not more so, that the wood it is bonded to.

: Hmmm... you'll probably come out of this testing with the ability to build
: not only to predetermined weight and strength qualities, but to
: predetermined flexibility as well. With several levels of optional
: finishes. That kind of product tailoring will give the prices some nice
: elasticity - upwards!

I'd settle for being able to predict the weight, and have data to show that the hollow cores are as strong as a solid core. Seems to me, a solid cedar paddle is the default baseline. Any weaker than that, and I'd want to make some changes. I wish I was smarter - it would be fun to try to engineer in ALL the qualities - strength, flex, shape, and finish - using the different properties of species of wood, and glass/epoxy.