Examples of repairs : GRP rudder inspection / repair

Example 3 - GRP rudder from a Rival 31. 

The rudder was suspected of being waterlogged and the owner required this to be checked along with the internal structure. 
The centre of the rudder face on one side was totally removed to expose completely saturated and chemically degrading polyurethane foam.  All of the foam was removed, the laminated area of tang connection to the stainless steel stock was ground away to check the welds for corrosion and integrity.  These were all found to be sound and secure. 

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An additional tang was fitted for extra backup and the old centre section of face was refitted using epoxy resins and glass cloth.  The inlet and outlet position for the rudder stock was sealed with polyurethane sealant and over laminated.  The whole of the rudder was epoxy coated to complete.

Points to remember :

• Polyester resin is not acceptable for any underwater repairs to any areas of a GRP vessel.
• Epoxy resin should generally  be used for all repairs.
• Laminates ( glass cloth) must be well saturated and all air must be eliminated by using a proper lay-up roller.
• Rudder shafts must be sealed effectively with polyurethane sealant only.
• silicon  sealant should not to be used as this does not perform well under constant immersion loses adhesion after a short time.
• Replacement tangs must be of appropriate material.
• Replacement foam should be the correct type ie polyurethane structural foam. Marine foam is generally of a higher specification than house-builders expanding foam.