Why vacuum bag
Under vacuum, atmospheric pressure presses the fabric evenly onto the foam. The result: a more compact and lighter lamination, fewer bubbles, and a PVC bond with no hard spots. It is also more repeatable than laminating with a squeegee alone.
Equipment
- A vacuum pump (rotary vane) with a gauge and, ideally, a reservoir or a resin trap.
- A vacuum bag or bagging film and sealant tape, with a valve connector.
- The consumables: peel ply, perforated release film, breather.
The stack, from top to bottom
Vacuum bagairtight, with the pump valve
Breatherspreads the vacuum and soaks up excess resin
Perforated release filmlets resin through, does not stick
Peel plypeels off after curing, leaves a surface ready to sand
Resin-soaked fabricthe lamination
Foam blankEPS, plus PVC if any
The valve sits on the breather, never directly on the lamination.
The steps
- Prepare everything dry: cut the fabrics and consumables, close the bag and do a vacuum test to find leaks.
- Follow the resin data sheet (accurate mixing on the scale, temperature, working time).
- Wet out the fabric on the board, squeegee off the excess.
- Lay the peel ply, perforated film and breather, then close the bag.
- Pull the vacuum gradually, smooth out the bag creases so they don’t mark the board.
- Keep it under vacuum until the cure time given by the manufacturer, then peel off the peel ply.
Vacuum level and EPS
Careful with EPS: too strong a vacuum can crush the foam, especially at low density. Many EPS shapers work with a moderate vacuum (around -0.3 to -0.5 bar). Always test on an offcut of your blank before the board.
Common mistakes
- Leaks: the vacuum does not hold. Check the sealant tape, the creases and the valve connector.
- Dry spots: too much resin pulled out. Less vacuum, or more resin when wetting out.
- Crease marks: add “pleats” in the bag to give slack where the shape is complex.
- Resin kicking too fast: too much mixed at once or too high a temperature.
Safety
Epoxy can cause lasting skin allergies: nitrile gloves, goggles and a ventilated room are essential. When sanding fibres and resin, wear respiratory protection suited to the dust.
The calculator sizes the vacuum bagging consumables (peel ply, perforated film, breather, bag) for your board and the roll widths.
Open the calculator →