X. Filling, sanding. Repeat n times, or even m times. m-many
ДThe next step will be filling. For the filler to adhere, the base layer must be "sanded" with abrasive, otherwise nothing will "stick" to the "glass". To select a filler, you need to contact the supplier/manufacturer's technologists and choose the material. The material will be epoxy filler with or without fibreglass. This type of filler is used when applying relatively thick layers to level large irregularities and join surfaces together. After filling, the layer is sanded, then more filler is applied and sanded again. This process is almost endless and ends either with patience or a perfect surface.
The main lines and cheekbones are measured. They are aligned relative to the diametrical plane of the vessel.
Metal rulers, templates made of hard materials, laser scanners and total stations are used to measure the dimensions and compare the left and right sides of the hull.
Our hull differed from the ideal. The symmetry of the front cheeks relative to the diametrical plane was slightly disturbed.
This aspect was identified during the study of the 3D model. Accordingly, using tape measures, rulers, laser levels and templates, we mark out the transition lines. We use paper tape for marking. Putty is applied to create volume and then sanded along the marked lines.
If you are not successful with a 3D scan, it is not a concern. You will need a metal ruler with clearly legible markings, a pencil, and paper. Divide the required area into a grid. The grid spacing can vary depending on the object and its curvature. For our purposes, the longitudinal grid spacing is 5-10 cm.
For example, let's say we want to check the line of the spray deflector running along the hull. From the transom to the stem, markings are made every 10 cm at a location that will not be removed during work (this can be on the hull flange for connecting the upper and lower hull shells to each other). This must be done on the left and right sides. Next, at each marked point, we measure the "height" - the vertical distance from the flange to the splash guard - and record it in the table. Then we compare the values and draw conclusions about where the line needs to be "extended".
Orbital sanders are good for everything except working in corners, close to walls, etc. You can get a machine with a smaller disc (5" or 4" instead of 6").
It is convenient to use vibrating machines along the walls and corner machines in the corners. But no one has cancelled manual sanding blocks. Rectangular, radius, small and large corner blocks. Sometimes they are the only way to get into the necessary nooks and crannies and sand the surface. Light is also an important aspect. Direct and corner lighting allows you to see pits and bumps on the surface. Filler is applied to the pits, and the bumps are sanded down. Do not apply a large amount of filler because it is relatively fragile. The less filler, the better.
Various spatulas are used: metal, rubber and plastic. They range in size from small to large. Plastic spatulas can be used to create cut-outs for profiling filler, for example when transferring the profile of an element from one side of the boat to the other.
Sooner or later, the work of removing and levelling surfaces comes to an end. The surface is sanded with P300-P400 abrasive to create a smooth surface. Ideally, the surface should be washed with a cleaning agent to ensure that no abrasive dust remains in the remaining micro-pits and pores. If this is not possible, blow with compressed air and vacuum thoroughly. The surface is dried, degreased and coated with a light epoxy primer. The primer is applied with a 4 mm long natural lambswool roller. Before applying, we use a painting trick. Stick the edge of the paper masking tape to the surface, hold the other end in your hands and roll the roller over the sticky surface of the tape so that individual hairs remain on the sticky layer of the tape and not on the body during painting.
Epoxy primers are selected in two colours; we typically use light grey and dark grey. The layers should alternate in colour, which is necessary for subsequent finishing operations such as sanding before applying the final coatings. The two colours make it clear how deeply we are sanding into the layers.
If we use a non-fouling coating, it is better to apply it to the ground. After applying the coating, do not touch it with your hands. If you do touch it, wash your hands thoroughly with soap. Depending on the composition, the shelf life of the composition without water may be limited, so you can leave the hull in the ground and apply the non-fouling coating before the start of the season. After the primer, a top coat was applied to the sides as a future base layer, but more on that in the relevant chapter.
Next, turn the shell over to its "normal" position and start working on the inside.
Before tackling the interior of the lower shell, it is worth paying attention to the power unit. To a large extent, the appearance of the interior (and partly the exterior) shell is determined by the technical features of the mechanics and transmission.
So, let's get started on what is sometimes called remotorisation... something that strikes fear into the heart and costs a lot of money... which has to be spent on it. Since it has to be done, it might as well be done beautifully.