Curved Elements in Wood 302d Flashcards
(32 cards)
Ability of wood to bend depends on
-Density
-Innate properties (elasticity, grain direction)
-Length of piece
-Required radius
-Thickness of piece
The three bending stresses
-Tension
-Compression
-Torsion
Tension failure
Splits and shatters
Compression failure
Wrinkles and crumples
Which side of the bend experiences tension?
The convex side (outside of curve)
Which side of the bend experiences compression?
The concave side (inside of curve)
Describe a staved panel
Panel made from long narrow strips of wood, machined with beveled edges, glued together into a curve
Describe kerf core
Bendable sheets made by cutting a sequence of parallel kerfs into the back side of the material, can be layers for two good sides
How many layers in rubber ply?
Three, thick rotary cut veneer on the outside, and either very thin veneer or paper for the core
How close to the surface should you cut your kerfs?
About 3mm from face
How should you determine kerf spacing when creating kerf core?
Cut one kerf, mark out radius required, lift stock until kerf is closed, measure space from marked end of radius to lifted piece
Three ways to make your own curved panels using ply
Laminating layers of thin ply, laminating layers of thick veneer, kerfing sheet goods
What kind of form should you use with a vacuum press?
One part form
How should you finish the two surfaces of a two part form?
The critical side should have a hard finish, ie laminate, and the non-critical side should be lined with a flexible and compressive layer to evenly spread clamping pressure
What is it called when your cured lamination relaxes from its clamped form?
Springback / bounceback
Methods of creating curved solid elements
-Brick
-Band saw
-Kerfing and a shaped form
-Shaping with routers or shapers using templates
-Steam bending
What grain should you try to avoid in load bearing pieces?
Short grain
Different portable router bits that can be used to follow templates
-Flush trim
-Template
-Collar and straight bit
-Pilot tip (not reccomended)
What style of spiral fluted bit should you use with an overhead router?
Downshear
How long should you steam a piece of solid?
Around one hour per inch of thickness
Tool used to control tension effects when steam bending
Bending strap, a steel band that helps contain outer edge
Species of wood who have a smallest radii of 2”/52mm
Oak, Hickory, Elm
Species of wood that has a smallest radii of 3”/76mm
Walnut
Species of wood that has a smallest radii of 4.5”/ 114mm
Ash
