- Product: C channel tabletop support
- Type of work: Product design, design for manufacture, fabrication drawings
- Materials: Solid timber and steel
- Process: Steel fabrication
Project overview: the C channel tabletop support
This project needed a C channel tabletop support to keep a solid timber top flat and rigid for years of use. The brief was clear on one point: no visible steelwork. The support had to be there, but nobody should see it.
The challenge and the thinking behind it
Solid timber is a natural material, and it moves. It takes on and gives off moisture as the seasons change, and a wide top can cup, twist or sag if nothing holds it in shape.
The common fix is a steel frame or bearers fixed underneath. That works, but it shows, and it makes a table look heavier than it needs to. So the question became: how do you add real stiffness without adding anything you can see?
My starting point was to put the steel inside the timber’s outline rather than below it.
Design solution: a recessed C channel tabletop support
I designed a recessed C channel tabletop support in steel. It sits into a groove cut in the underside of the tabletop. Set flush, it can’t be seen from normal viewing angles, yet it runs along the length of the top and stiffens it.
The steel parts were kept simple, with straightforward cuts and as little welding as possible, so they would be quick and economical for a fabricator to make.
Design considerations
- Appearance: the steel had to stay hidden, so the recess and channel had to sit flush with the underside
- Timber movement: the timber moves most across its width, so the support needed to control bending along the length without fighting that natural movement
- Fabrication cost: simple steel sections and few operations, so the part could be made by any competent fabricator
- Fitting: the recess had to be practical to machine and the channel easy to fit
Engineering rationale behind the C channel tabletop support
A C channel is an efficient shape for a tabletop support. Most of its material sits away from the centre of the section, which is what gives a beam its stiffness. Engineers call this property the second moment of area. That means a lot of bending resistance from a small, light piece of steel.
Steel is also far stiffer than timber. By recessing a slim steel section into the top, the tabletop and channel work together, and the steel takes on much of the bending load that would otherwise cause the timber to sag or bow.
Recessing the channel rather than fixing it underneath also keeps the overall depth of the table edge down, which keeps it looking light.
Deliverables
- 3D CAD model of the tabletop and steel support
- Fabrication drawings for the steel C channel
- Drawing information for the recess in the timber
- Drawings ready to send to a fabricator for pricing and manufacture
Outcome
The finished C channel tabletop support leaves a top that is stiffer and better able to resist distortion, with the steelwork completely out of sight. The parts are simple to fabricate, and the drawings give a fabricator everything they need without a string of questions.
Services used
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If you have a part or product that needs designing, drawing or improving, I’d like to hear about it. The first call is free, and you’ll get a clear quote before any work starts.