14 REFIT STAGE 2 – Sanding, Sanding and more Sanding…

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Graphite pencil on the hull to test fairness.

To quote Jim Saltonstall – “Proper Preparation Prevent P*ss Poor Performance”.

So first part of the preparation was to talk to boat building expert Nick Harvey to get his advice on how to approach the sanding of the boat. For anyone considering doing this work here is his advice:

  • For the initial sanding use 60 Grit sandpaper, 120 for final finishing
  • You need two types of long board; a stiff board and a flexible board, length should be around 400mm or longer and ideally the same width as a stand roll of sandpaper.
  • A good respirator/face mask this is really important you are going generate a lot of dust, the yellow ‘paint’ in the photo is dust.
  • Electric detail sander
  • Electric Flat Sander
  • Detail sanding blocks, sourced Style-Line Soft-Sander Sanding Blocks which are curved and shaped foam blocks
Partially sanded deck, the yellow colour isn’t paint it is dust.

What we were trying to achieve

There were two major objectives in this exercise;

1 – Take the boat back to the composite base so at worst we don’t add any weight with the respray and hopefully we reduce weight slightly 

2 – Fair the hull so the hull is as flat and smooth as possible

The tricky bit about fairing a hull is avoiding flat spotting the hull, in order to avoid this the professional recommendation is to sand at 45 degrees to the horizontal in a X like motion. This is done across as wide a spread as your arms can cover. This prevents focusing on one area and works high spots down evenly.

By doing this and working from your starting point to an end, you get an even sand across the entire length of the hull. The effect can be seen below.

We initially started on the hull but decided it was easier to do the topsides and deck before finishing the hull. One of the reasons for this was simply practice, we did not want to change the hull shape so it made sense to work on the easier topsides first.

This boat has been extensively modified and this became clear as the paint was sanded off. There was a noticeable difference between the original build fairing material and compound used post the modifications. The later being a much lower density and prone to opening up pin holes.

The design of this 14 means the topsides are relatively flat we could use the stiffer of the two boards for about 70% of the hull, especially the aft sections, using the flexible board and for the forward 25% and our foam detail blocks for last more complex bow curves.

For the deck there is less concern about fairness, and the extensive non-slip in the paint meant that using the power sander was the preferred option. Using power tools does mean extra care needs to the taken as it is easy to burn through the carbon skin or old repairs. Which we did…

T Bear repairing a hole in the side deck. 1.5mm carbon plate with epoxy resin then filled with AWLFair fairing compound

The approach with the hull was similar to the Top Sides except after the initial work we only used the flexible sander, the composite curves made it to hard to get a fair finish without flat spotting. The hull shape varies significantly from front to back, with the aft sections being relatively flat and wide curves with the bow feeding into very tight curves. 

Paint layer being removed but not going down to the composite layer at this stage.

First pass was primarily to remove the yellow paint and not to go into the Carbon composite, as the above image shows we stayed away from the edges of the chine with the long board. Instead we used a small hand block to do the detail work around the Chines and the Centreboard case.

Having removed most of the surface paint the next stage was to check how fair the hull was. To do this we used a Graphite pencil to pattern the hull and then used the flexible board with 120 Grit sandpaper and sanded the surface, gently to see how evenly the pencil disappeared. 

With this complete, the final area needing to the completed was the area around the centreboard case. This was particularly important to get right; this area of the boat is always in the water and we want to make sure that the board has a smooth a flow of water across it as possible. By replacing the Centreboard capping and sanding across the capping makes sure that we get the fairness we are looking for.

This is the finished hull before fairing, it is easy see the area of the bow where the boat was modified.

Nice fare finish but a visible hollow in the transom

Next stage is the fairing of the hull and the frustrating process of sealing all of the pin holes that opened up during the sanding process…

Final sanding finished, fairing next

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