Home Forums Repairs and Maintenance Ama arm cracks

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  • #592
    Paul WhitePaul White
    Keymaster

    If you start to hear a creaking noise from the joints of the ama arms it’s possible that a crack may have developed in either the upright or joint allowing some movement. Check for surface fractures.

    Vertical crack

    Vertical crack

    You can repair the structure using woven carbon mat wrapped around the arm at 45 deg to the existing carbon structure (boat builders/repairers may be willing to let you have an offcut).

    Materials
    – Woven carbon mat
    – 400, 800, 1000 wet/dry paper
    – Epoxy resin suitable for marine application
    – Disposable mixing containers and mixing sticks
    – Disposable paintbrush
    – Peel ply (available from modelling and fibreglass shops) or ripstop nylon (as used for spinnakers) – hencforth PP/RN in these instructions
    – Methylated spirits or denuded alcohol
    – UV resistant paint or clear sealant spray
    – Electric scales for measuring resin/hardner
    – Plastic packaging tape for masking
    – Sharp knife
    – Disposable rubber gloves

    Mask off the areas where the join is going to be made. Use plastic packaging tape where you don’t want resin to stick.

    Masking off

    Masking off

    Roughen the tube where the carbon is going to be applied with 400 wet/dry paper and when dry, clean the area thoroughly with alcohol or methylated spirits.

    Cut out the carbon so that it forms a “bandage” that overlaps at least half a turn – a complete turn may be a better depending on the thickness of the carbon. Cut out the PP/RN so that it will wrap around the join at least twice.

    Mix the resin according to the instructions and apply a layer to the repair area with the brush

    Lay the carbon mat on the resin and apply more resin on top making sure you use the paintbrush to force the resin into the cloth

    Lay the PP/RN over the wet resin and wrap it around the arm one turn so that you can pull it tight to force the resin into the carbon mat and squeeze out excess resin onto the surface of the PP/RN.

    Tape the PP/RN in place and leave to part cure.

    Peel-ply wrapping

    Peel-ply wrapping

    When the resin has started to harden but is still flexible, remove the packing tape from the masked off areas and trim off any excess resin with a sharp knife.

    Leave to fully cure with the PP/RN in place.

    When cured, remove the PP/RN and then rub down with progressively finer wet/dry paper to get a smooth finish.

    IMG_1258

    Peel ply removed and rubbed down before spraying

    Mask off any areas you don’t want sprayed and spray with paint/sealant to provide a protective top coat.

    • This topic was modified 6 years, 1 month ago by Paul WhitePaul White.
    • This topic was modified 6 years, 1 month ago by Paul WhitePaul White.
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