The edge of a plywood sheet is a cross-section of its layers, and that is exactly what a buyer inspects. A chipped edge shows the plies separating, which reads as a manufacturing defect even when the sheet is sound. A U channel covers the layer line and holds the plies together at the edge through handling.
The edge is the quality signal
A veneered or film-faced plywood is judged on its face first and its edge second. A crushed edge with lifted plies is the fastest way to a rejection, and it costs more to sort than to prevent.
Because the plies are bonded at the factory but not at the cut edge, an impact can open them slightly. A channel holds that edge closed through the journey.
Specification at a glance
Plywood is usually 12-25 mm, and thickness tolerance is wider than for MDF or plastic sheet, so the channel needs a little clearance rather than a tight fit.
| Plywood | Inner width | Leg | Wall |
|---|
| 12 mm | 13 mm | 40 mm | 3 mm |
| 18 mm | 19 mm | 50 mm | 3-4 mm |
| 25 mm | 26 mm | 50-60 mm | 4 mm |
| Film faced 18 mm | 19 mm | 50 mm | 3-4 mm |
| Marine ply 18 mm | 19 mm, dry | 50 mm | 4 mm |
Stacking, banding and the strap line
Sheets are stacked and banded. The band crosses the channel and the channel spreads the band load along the edge, which is the same job an L profile does on a corner.
Where a stack is strapped hard, a 3-4 mm wall is enough because the load is spread; a thin 2.5 mm wall flattens at the band line and the edge then takes the pressure directly.
Marine ply, film faced and exposed edges
Marine ply and film-faced boards have edges that matter structurally, because water enters through an open edge. A paper channel is not a seal, but it keeps the edge off a damp pallet and out of direct contact with water on the ground.
For a long sea leg, a coated facing is worth discussing. It slows moisture take-up, and the crate or container ventilation still does most of the work.
Questions buyers ask before ordering
Will the channel keep the plies from lifting?
It holds the edge closed through handling. It does not repair an edge that is already delaminating.
Why not a tight fit like on MDF?
Plywood thickness varies more, so a tight channel creases when it meets a thick sheet. Allow a millimetre.
Can it protect a film-faced board?
Yes, provided the board is clean, so the film is not abraded by grit between channel and sheet.
Is it suitable for marine ply export?
As a dry, physical cover, yes. It is not a waterproof seal; discuss a coated facing for long routes.
What length do you cut?
To the sheet length, up to 6,000 mm, bundled and labelled.
Send the panel thickness, leg length and wall you need to mona@hengnicepacking.com and we will quote the U profile that fits.
