Steam Bent Coat Hanger
Steam bending is an ancient technique of shaping wood. Heating the material and relaxing the lignin, which gives wood its rigidity, can be achieved. I challenged myself to create curves at a three inch radius, as this is the industry standard for hardwoods that are considered excellent for wood bending. White Oak, Ash and mahogany are all considered excellent in their ability to be bent from one stiff state to another.
Achieving these bends is challenging. With much trial and error, some successful cooking times and moisture was achieved. The term “folding” is used to discribe the sharp bend and subsequent cracking that occurs to wood when it is overheated. The wood often folded if the direction of the grain wasn’t appropriately selected before cutting the laminations into strips of steaming and laminating.
A pin table was initially used for tests. Custom pin holders were then built using laminated MDF Plywood with holes drilled for the pins. The laminations of white oak, 3/16 thick, were kept tight with clamps while the pieces dried and cooled after steaming.
Pieces were left for one day after steaming to allow the form of the oak pieces to set properly and fully dry before moving on to glue ups.
The laminations of steam bent white oak were glued together using an epoxy glue with a one hour working time. This was beneficial to the glueing process as many clamps were used for the glue-ups.
The coat hanger hooks showcase the sharpest bends that were successfully achieved in the course of the material tests conducted for this project. Edges were sanded once the epoxy glue was fully cured. The screw pattern for the hooks are scattered for two reasons. Firstly, it leaves room for longer screws into the coat rack spine. Second, it creates a rythmic visual gesture that is echoed in the screw pattern of the legs.
The spine is left long at the top to allow for the stacking of hats. Edges are left rectangular to create opportunity for wedging coats on the hooks, thus securing them readily.
To refine the manufacturing process for the coat rack, using a vacuum bag with a form would help glue firmly and without gaps the pieces bent together during steam bending. Forms would likely not work for the hooks, as the design calls for a double bend in opposing directions. Nonetheless, once the pieces are bent around the pins, they keep their form. Bending the pieces before putting them in a vacuum would ease the strain onto the pieces during glue-ups.
The coat rack legs were initially bent from 3/4 inch thick white oak. The bends achieved at this thickness were inadequate even after a day of soaking. The final legs are three thicknesses of 3/16 thick laminations.
With more time and resources, bending forms could be built, outfitted with a steam bending compression strap, to bend the full 3/4 inch pieces. The legs are bent at a larger radius than the hooks, and forms work well in the case of single bends. Stainless steel compression straps would be required, as the heat and moisture of the wood coming directly from the steam box, and having been pre-soaked, would cause the steel to stain the wood with dark, black stains.
The final prototype balances the length of the top pieces with that of the legs. The coat rack could accommodate a large number of coats without having to balance the load on each side with the legs as wide as they are.
This project has taught me the value of note taking to record changing parameters and to help find patterns in cooking times in relation to soaking times.