I should have found this newsgroup before I finished this repair project.

A relative brought me a rocking chair with one of its 5 back spindles
missing (broken completely out). the spindle is 28+ inches long. I
went to the hardware store, bought an oversized dowel, turned it to 1/2"
dia and one end, tapering up to 3/4" at the other. Then I tried
steaming it so I could bend it enought to get it into the mortises in
the chair. I steamed it in a 2" pvc pipe with my wife's drapery
steamer for about 10 minutes (that's all the water it holds). No
flexibility at all, but I did realize that the tenons swelled up so much
that they wouldn't have gone into the mortises anyway. Tried again with
the pvc pipe with steam going into the middle of the pipe rather than
from one end and shortened pipe so the ends stuck out. No luck. So I
bent the spindle until it broke, to see how far it would go. No flex at
all.
Folks think that hardware store dowels might be maple, and tell me
that maple isn't good for bending.
It was at this point that I spent time on the Internet looking up
"+steam* +wood" and reviewed a couple of old Woodwright shop tapes/DVD's
on the subject.
Folks say its the heat, not the steam that is important, but that
simple heating will dry the wood out and that's bad. So you need a lot
of heat and some wet. Look's as though the pro's all use steam anyway.
So, go out to the woodshed and get a piece of white oak that's been
there for 10 or 20 years. Made more spindles. Made some 1/2" wide X
1" test strips,the right length, pared down at ends to simulate tenons.
Laid the test strips across the laundry tub and slowly ran hot-hot
water over the center 2/3 of it. Got out the heat gun and heated and
watered and heated and watered for about 10 minutes, maybe a little
less. Bends just fine. Stuck 4 inches of one end in a vise and pulled
slowly until it broke at almost a 90 degree bend.
This process worked out just fine to install the spindle.

I still wish I had a steam box, but I really haven't needed one much.

Blacksmith 80%, wood worker 6%, master of anything 0%,
Pete Stanaitis