Welcome, I'm in Columbus also. On family trips, I'm the pack mule because I carry most of the gear and all of the food for our family of six (4 young kids). I use a large internal frame Kelty pack which isn't light, but it "comfortably" (ha ha) carries the load of around 80 lbs or so. I've tried external frames in the past, but I really like the stability of the load internal frames provide.

Check out these companies, as they make packs which I think would work for loads of 30-40 lbs:

ULA
Six Moon Designs
Mountain Laurel Designs

On my own, I use a lighter Gossamer Gear Gorilla pack which seems to do well with loads up to 20-25 lbs.