Hand Lay-Up

Hand lay-up is the simplest method of fabricating. The tooling and equipment is low cost and design changes can be readily made. This method is good for low to medium volume parts. Hand lay-up gives a finished/gelcoated surface on one side of the product only (the mould face). This is the most labour intensive method of fabricating.  Skilled fabricators ensure consistent quality. Hand lay-up is also called open moulding or contact moulding.

allnex products commonly used:

  • Resins (UPE, vinyl ester)
  • Fillers & putties
  • Catalyst, promoters, inhibitors
  • Mould preparations
  • Gelcoats & flowcoats
  • Accessories (brushes, rollers, bags, peel ply)
  • Reinforcements (chopped strand mat, fabrics, tissues, speciality fabrics)

Steps

  1. The mould surface must be well prepared with a release agent.
  2. Gelcoat is firstly applied to the waxed mould surface either with a brush or with a spray gun and allowed to cure. 
  3. The resin is catalysed1 and then applied by: brush, paint roller or spraying from a gun
  4. Reinforcing fibres (Glass, Aramid, Carbon) in the form of tissue, cloth, chopped strand mat, or fabrics are placed onto the mould by hand2,3.
  5. Manipulate the reinforcement into all radii and details of the mould to ensure no bridging occurs and creasing is minimised.
  6. Thoroughly wet the reinforcement and consolidate the laminate with a roller to remove entrapped air.
  7. Further layers of fibreglass reinforcement and catalysed resin are added in the same manner to build the required thickness.  As a guide no more than four layers of resin and reinforcement should be applied at any one time to prevent excessive exotherm of the laminate causing problems with product quality. Where thick laminates are needed, each series of four layers should be allowed to exotherm and return to ambient temperature before subsequent layers are applied.4,5
  8. Flowcoat is used in place of resin in the final layer to prevent air inhibition and tackiness.
  9. The curing reaction occurs at room temperature.

Notes:

1To optimise the manufacturing process and final laminate performance the suppliers’ instructions for mix ratios of resin and catalyst should always be followed.  The resin’and catalyst should always be measured accurately on calibrated scales/measuring cylinders.
2Resin is applied first before the dry reinforcement to enable thorough wet-through of the fibres, and reduce possibility of air bubble entrapment.
3A finer reinforcement such as tissue, print blocker or light weight chopped strand mat used in the reinforcement layer against the gel coat will minimise fibre print through, providing a smoother, high quality surface finish.
4The surface should be cool and tacky.
5If the laminate has been left for a long period of time i.e. 72hrs or more, the surface should be abraided/sanded before subsequent laminate is applied.  (40 grit sandpaper or discs are recommended). This assists bonding between existing and subsequent laminate layers.