Originally Posted by zzyzx
4)Drive back to see Akaka Falls.(0.5 hour? )
The fastest you could drive from the overlook to Akaka Fall, ime, would be 60-70 minutes -- and that is not counting any slow trucks.
And, as far as I'm concerned if you're driving that way and don't make the short side trip to Laupahoehoe Point you have missed one of the most dramatic (and sadly historic -- the memorial to the 1946 tsunami where 2 dozen+ teachers and students were swept away. Families still maintain the memorial. Very moving) spots on the whole island.
5)Drive to Vocano NP( 0.75 hour?)
Plan on an hour. You *might* make it from Akaka Falls to VNP in an 3/4 hour but I never have.
6) Is it possible to see the Black Sand Beach in an hour(drive there from VNP and back?
No. And even if you could come close, if you're only allotting yourself an hour all you'll have time to do is speed through the parking lot and wave at the turtles and get a quick glance at the black sand.
My sense, brah, is that you would be better served to pick either south/west from Hilo (VNP, Black Sand Beach, Hilo town) or north from Hilo (Waipio overlook, Laupahoehoe Point, Akaka Falls, Hilo town) than to try to do both.
Part ofthe attractiveness of Hawaii is what happens when you are not on a tight schedule -- walking the black sand beach, particularly the trail north where few tourists go, stopping in Pahala on the way back from the beach for malasadas at Tex Drive In, stopping at the Verna's (and -- note for other locals: Verna's has a new slogan!) on the Keaau-Volcano highway and talking story. Or being at Laupahoehoe Point and talking with a man whose brother was swept away in the 1946 tsunami, or seeing across the way a memorial service for a local who died too young and being invited to join in the lunch after the service; or walking the shops in Honomu on the way to/from Akaka Falls and talking with some of the "characters" there (or doing the same in Honoka'a after the Waipio overlook); walking Kamehameha Avenue on Hilo's bayfront, etc., etc. So slow down, do less, and experience more is my un-asked for counsel
(And, in any case, whether you end up agreeing or not, do not in your travel planning use the mainland mile-a-minute calculation. It's half that.