14 REFIT STAGE 8 – Forward Block Plate

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When we weighed the boat before taking her apart, we found that the boat was over weight by about 5 kilos. Not particularly significant in terms of performance, but it is aways worth making the boat as light as possible.

Areas where we could make weight savings includes the deck gear and layouts. We took 10 Kilos of deck gear, fittings and fixings off the boat, so there is the opportunity to make some weight savings in those areas.

As can be seen on the right the old systems utilised a lot of metal work and heavy blocks.

In big racing boats there is a general move towards not using metal fixings, instead they use spectra loops epoxied onto Carbon plates and then the plates are epoxied to the hull or deck.

The benefits are reduced weight and increased strength as with modern adhesives the chemical bond can be as strong as mechanical fixings, although it is dependant on what you are bonding onto.

We also did a comparison of the various block manufacturers, comparing weight and working loads. For our purposes Harken’s 18 mm T2 Soft-Attach Block, is less than half the weight of the existing blocks with a higher working load. The soft attach loops means that the blocks can easily be passed through spectra loops.

Clamped to a chopping board to press the resin into the spectra fibres

To save weight in the fixings, we decided to build a carbon plate, which we would pass Spectra Loops through and attach the Soft Attach blocks through.

To achieve this we took the following steps:

  • Cardboard blank of the bow area
  • Cut and shaped 3mm Carbon plate and dry fitted into bow area
  • Drilled 4mm holes in the plate for the blocks
  • Put spliced 2mm SK79 loops through the holes splayed out behind the hole
  • The splayed spectra was then epoxied to the back of the Carbon plate, clamped to a flat surface
  • Once the epoxy cured, we attached the T-2 blocks to the loops
  • The surfaces had to be prepared for gluing, this involves sanding both surfaces with 120 grit sand paper immediately before gluing the plate onto the hull with our favourite Methacrylate adhesive.
  • Just to cover ourselves, we used 4 screws to provide mechanical support, it never hurts to have more support 🙂

In the end we saved more than 50% of the weight of the old fixing blocks.

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