Justine has a pair of frames (one port, one starboard) at each station where there is a construction mold. This makes a total of 44 frames, two at each station from stations 2–23. The frames are cut from white oak planks and milled to 7/8″ square cross section. They are steamed, quickly bent to shape on the corresponding construction mold, clamped in place, and allowed to cool and harden for at least a day or two.
I bought most of my white oak from New England Naval Timbers in Cornwall, CT. The planks are “live edge,” that is they are complete cross sections of logs and often have bark on the edges of the planks. (Sometimes the bark is loose and falls off when the planks are first cut.) White oak can have a significant layer of sapwood under the bark, and it is relatively unsound for boat timbers. So the sapwood needs to be cut away. (It makes good kindling.) The planks I bought had been stacked and “stickered” with wood spacers, then air dried for at least one year.
If a piece of wood is bent sufficiently, it will break—even if it is steamed. Breaks tend to follow the “grain” of the wood. So frames need to be cut parallel to the grain of the plank in order to minimize places where the grain crosses the frame. Ideally the frames are gotten out of quarter-sawn planks with very straight grain, but it’s hard to find such planks and they are expensive. So I ended up cutting somewhat curved shapes for my frame blanks, following the grain of each plank.
After removing the sapwood, I ran the plank through my thickness planer to bring it down to 7/8″. I then marked and cut strips about 1″ wide that followed the grain of the plank. I made these cuts with an 8″ circular saw.
I sorted my frame stock to match particular pieces to particular station molds. In places where the frame would need to take a sharp bend, I used stock with very straight grain where the bend would be. I tried to use all the stock with more questionable grain for the relatively straight frames on the forward construction molds.
My steam box takes about an hour to really get going. Inside the long box are some cross pieces that serve as racks to separate pieces being steamed. I usually steamed about 8 frames at a time. They were all marked with their mold number, but it was still important to know which frame you were about to grab from the box.
The common rule of thumb for time in the steam box is one hour for each inch of cross section of the piece. So I steamed my 7/8″ frames for at least one hour.
It is primarily the heat, and not the steam per se, that makes the wood pliable. So it is critical to work quickly once the frame comes out of the steam box. If the frame cools much before being fully bent, you risk it breaking. And, the thinner the piece, the more quickly it cools.
I fashioned U-shaped straps from steel sheet and screwed them low down on each “leg” of the construction molds. These served to secure the end of the frame very quickly before starting the bend. Extra room was left to drive in a wooden wedge to firmly hold the end of the frame in place. Where the construction molds have a winding bevel, the hot frame needs to be twisted so that it will lie flat on the bevel. Extra hands are needed to clamp the frame in place on the mold.
With a total of 44 frames to steam and bend, you begin to acquire experience to the point that things go relatively smoothly. Even so, getting each one bent and clamped without breaking is a small triumph. I think I broke about five of them and had to cut and steam-bend replacements.
