The blades were made from a simple, hollow metal spar, with metal pockets bonded on to form the constant blade profile along its length.
Sounds like a good description of the R44 blades!
I wonder what the REAL figure is for the R44? I'd really like to know how much margin I have when I'm flying a steep approach at 300 ft/min - will I plummet earthwards at 310 or is it (which I'm pretty sure I've seen somewhere) above 500 before bad things happen?