I needed to bow the 3/8" mahogany plank that goes beneath my traveler. The bow above the lazarette bulkhead is pretty minimal, but I didn't successfully bow it when I created it and the athwartship ends of the piece lifted up a bit off the deck.
So, I successfully used this method - https://youtu.be/--iPQIwSEJM*- making a steam bag out of tarp material and duct tape coupled to a home/laundry steamer.
Because of COVID, the storage shed at my boat yard is closed, so I couldn't get the exact radius off of the top of the bulkhead. By my guess-timation, the radius on the trim piece above our fireplace seemed about right.
Made a box out of 3/8" plywood and 2x4 scrap to match that radius.
Steamed it for about an hour clamped to my form. Let it cool in place. It got plenty hot with the laundry steamer.
Finished product!
This is a good video on building an actual steam box https://www.youtube.com/watch?v=NMvc2tuVGcQ* Just didn't seem worth the trouble for potentially the only time I will find myself steam-bending wood.