Kalzip Inc. IMETCO Kalzip Inc. IMETCO 8 thi n gs to kn ow about curv ed metal panels
While the majority of your projects may require basic straight metal wall and roof panels, some will require panels to be curved. Whether the project calls for curved roof or wall panels, there’s a lot to know about curving metal panels. Metal Construction News talked to some industry experts to learn more about what is required when a project calls for curved metal panels.
1 Types of Curved Panels Curved panels can come in a variety of shapes.
Barrel-vaulted, or convex curves, are the most common version where the roof design consists of an outward consistent curvature that creates a con- vex shape. A reverse curved roof, with the curve turned inward, is known as a concave curve. Some manufacturers also offer a complex
curvature, known as an S-shaped curve, which combines a concave and convex curve. In addition to single- and S-shaped curves, Curveline Inc., a metal panel curving service based in Adelanto, Calif., also forms double- and triple-radius curves. Michigan City, Ind.-based Kalzip Inc. offers
elliptically and hyperbolically curved panels, in addi- tion to convex and concave panels. Called XT Pro- fi les, the freeform elliptical and hyperbolic curves are applied to Kalzip’s standing seam sheets for use with complex curved roofs, allowing architects" unrestricted design and fl air when it comes to curved surfaces, as Paul Stringer, technical support engineer at Kalzip’s U.K. location, explains.
2 Curving Methods There are a variety of methods through which a
panel can be curved. Stringer describes the basic
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curve as a natural curve that the panel will natu- rally curve to, without being forced or excessively strained, which would create visual deformations and possible creases. This can also be known as the “lay-down” or “walk-down” method, as George Jones, director of fi eld services at IM- ETCO, Norcross, Ga., calls it. “For large radii, the panel’s weight will cause it to naturally drop down or conform to the substrate surfaces within reason,” Jones says. “For smaller, tighter radii, the same approach is utilized, but the installer will be forcing the panels down and holding them in place with the panel clips.” A mechanically curved panel creates a curve
that is tighter than what its natural curve will permit. Panels start as a straight profi le and are curved by a machine that physically alters the panel by a set of forming and curving rollers. Jones explains that the rollers stretch or com- press the straight panel into a curved shape. “These curving rollers can be mounted to a standard panel roll former, or can be a separate operation,” he notes. “Both of these methods provide a consistently curved panel that will fol- low a consistent curved substrate.” A third method is called crimp curving. “Crimp
curving is typically used where there is a continuation of the roof down the building façade and a soft visual edge is preferred to a sharp edge,” Stringer says. “The crimping is as the word implies, has an undulat- ing surface that is introduced by pressing the sheet with indentations to achieve the required radius. The crimping process allows for reasonably tight curves to be achieved, though at the expense of a local- ized corrugated surface to the radiused area.” Crimp
curving is the process that Curveline uses to curve its panels, and according to Dennis Klocek, AIA, CSI, product manager at Curveline, this process actually increases the structural integrity of the panel.
3 Material Selection While just about any material—stainless steel,
galvanized or Galvalume steel, copper, zinc or aluminum—can all be used for curved metal panels, some materials are easier to bend than others. “Alu- minum tends to allow for a tighter curve with many panel systems,” says James Bush, vice president of sales, ATAS International Inc., Allentown, Pa. “It may also allow for fl exibility for fi eld adjustment, as often a true curve is hard to build with various substrates to which the panels are applied.” “For curving metal panels, the softer more
ductile materials are often preferred, but not re- quired,” adds Jones. “For larger radius conditions, any material can be utilized, but for tighter condi- tions, copper, zinc and aluminum are preferred. The most cost-effective approach is to use steel for larger curvature while using aluminum for the tighter applications.”
4 Panel Thickness When it comes to how thick of a panel to use for
a curved application, thinner materials are easier to curve because there is simply less material that is needed to conform to the desired shape, explains Kurt Schievelbein, technical manager of rollforming operations at Berridge Manufacturing Co., San Antonio. Bush explains that for aluminum, the com- mon substrates are 0.032 and 0.040, and for
October 2012 METAL CONSTRUCTION NEWS 29
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