Edge Capping a Cored Panel: Packing Unidirectional Fibre Into a Tight Channel

Following on from the beam-theory reasoning behind cutting a bulkhead for headroom, this is the actual execution — getting calculated unidirectional fibre packed properly into a narrow routed channel, which turned out to be a genuinely different challenge from laminating it onto a flat panel.

Why Uni Behaves Differently Wet Than Dry

Unidirectional fibre rolls up easily enough dry — it’s once resin goes into it that the real challenge starts. Wetted-out uni becomes considerably harder to compress and manoeuvre into a tight space, and this particular channel was only 20mm wide, which meant real care fitting material that was actually cut slightly oversized at 25mm.

The bigger issue turned out to be the cross-fibre — the threads running perpendicular to the main unidirectional fibre, there to hold the roll together during handling. That cross-fibre is a non-issue on a flat panel, where it lies down flat and contributes nothing but a bit of consolidation. Try to pack that same material into a tight channel or radius, though, and it resists conforming to the shape — it wants to hold its flat form rather than bend into a gap, exactly the opposite of what a tight structural channel needs. It’s a good lesson in itself: uni is excellent for flat lamination, but a channel this narrow needs the fibre trimmed and handled with that cross-thread resistance specifically in mind.

The Masking Tape Consolidation Method

Getting the fibre properly consolidated into the channel — packed tight, no voids, no gaps between the uni and the sides of the trough — came down to a genuinely simple trick: masking tape, pulled as tight as possible over the packed fibre while the resin was still workable, holding everything compressed into position through the open cure window. Not a sophisticated piece of equipment, but an effective one — the finished result consolidated well, with only a couple of stray fibres needing tidying up afterward.

Why Post-Cure Matters Here

With a cooler evening working against a full cure, giving the laminate proper time before sanding mattered more than usual — resin systems like this one benefit from a genuine post-cure period, and rushing straight into sanding on a laminate that’s still soft risks disturbing a joint that hasn’t fully set. Patience here is cheap insurance against redoing the work.

The Finished Numbers

For anyone wanting the specifics: the channel was routed 20mm wide by 5mm deep, filled with ten layers of 600g unidirectional fibre — the exact figure the load calculation called for in the first place, not an approximation. With that cured and consolidated, the remaining steps are straightforward: radius the edge properly, then edge cap over the top to finish it.

Meanwhile: The Bottom-of-Stairs Floor and Hatch

In parallel, the floor and hatch for the base of the stairs have been templated and are ready for infusion — a full day’s work went into marking out and drilling the resin-transfer holes needed to get even flow through the panel during infusion. With that prep done, a new floor there should be in place shortly.

For the engineering reasoning behind why this section needed reinforcing in the first place, see Cutting a Structural Bulkhead for Headroom: The Beam Theory Behind It. Follow the rest of Paikea’s interior transformation on the Paikea’s Refit page.

In This Series

Edge Capping a Cored Panel is one part of Paikea’s bulkhead reinforcement. Follow the rest of the build here: