Note that without a powered hub, the LED on the hard drive (if one exists) might light up, but that doesn't mean it's getting enough juice to operate properly.
If the disk is not showing up, it may be that it's formatted incorrectly. What format is it now? I believe it has to be either HFS+ or FAT32 (not sure on the last one) for it to be shared via the Disks tab in AirPort Utility.
No. I was at the Apple store and was told it sounds like usb hub is not sending enough power to recognize drive? It is an older 2.0 hub. Because I can plug iphone into hub and it shows, means it works but a hard drive needs more power. Makes sense I guess.
I'm confused... Is it or is it not powered? Does it have an AC adapter that you plug into the wall to provide the hub with power?
Also, is your HDD powered? If your hub does not or cannot have an AC adapter providing it with external power, you may still be able to connect the HDD if it has an external power source itself.
As I stated in earlier post, hub is powered, as is hard drive. Because both are older, the compatibility issue may come into play. It seems to be the only other rational answer, as when I plug HD directly into iMac, it shows up. As well as when I plug my iPhone into hub, it's slow but it shows up and works!