Richard,

How big is your steam box, and what are you using as a steam source?

I bent the ribs for my Brinck baidarka two weekends ago, so the pain is still fresh...

Here's what worked for me:
I'm using a Steam Kettle from Lee-Valley/Veritas, attached to a 4' long steam box made from 3/4" ply. Inside dimensions are about 6" square. It has 'shelves' at 2" and 4". I only steam on the top shelf.

I got a thermometer from the grocery store that goes to about 240, and have that stuck through a hole into the box. Make sure you preheat the box before you start the rib, and try to get the box as close to 212(F) as you can.
Remember you want steam to move through the box, so don't make it airtight.
My ribs were 1/4" x 3/4" kiln dried Red Oak and I found that a rule of thumb of 60 minutes per inch of height (irregardless of width or length worked great.)

I also found that easing the edges of the rib helped reduce splintering, etc...

I haven't read Cunningham yet so if I'm repeating advice, I aplogize.

I'll post pictures of my rig tonight if you tink they might be useful for you.

: I cut my ribs on a table saw, and I am thinning the edge on a router. I
: discovered last night that I am not getting good steam penetration into
: the wood I left a test piece in for 22 minutes. I know this is a long
: time, I was just testing when it came out the edge closest to the door
: wouldn't bend at all and it got gradually more flexible as it got closer
: to the steam source. I think I'm not getting enough steam into the box,
: but do not know how to solve this with the limited funds and material on
: hand.

: Richard