Hole reparing

Repair and re-surfacing

For the repair, the first survey should be done. The yacht carefully examined and tested in the main strength members, the hull, deck, and cabin arrangement. Generally, the probing is performed with hammering and visual inspection then estimates the condition. The hull is composite construction, for instance, inner laminate total thickness is 2.5 mm the foam core is 12mm and the outside laminate total thickness is 3mm, the fiber is E-glass. The surrounding damage is small, for instance, 50mm. Therefore, its repair area is 1000mm x 400mm. The damaged area should be marked ellipse shape of the circle with pencil. The circle should be covered 1000mm x 400mm.

Before the cutting damage area, the scarfing area also should be considered that is 30:1. The ellipse-circle should be bigger than the first estimation since inner-skin is 2.5mm and outer skin is 3mm, therefore, the inner-skin, core, and outer-skin have different diameter, 1000mm x 400mm, 1150mm x 550mm and 1150mm x 550mm, respectively. The ellipse-circle could be cut out with diamond-cutter, nicely.

Before the laminating, foam core and fibers should be prepared with proper size, especially, each fiber is different size because of scarfing. To prepare the fibers, be aware of that Inner-skin and outer-skin size also different.

Fig 1 Preparing the fibers (ABS, 2006)

By the (ABS, 2006), the new core will need to be slightly thinner than the existing core to accommodate the additional repair laminate thickness, or the core can be make holes to squeeze out the glue. The outer-skin is 3mm thickness, it will scarf 90mm. back-plate is also prepared for the inner-skin laminating. 

Laminating starts from the inner-skin, core, and then outer-skin, sequentially. For the inner-skins laminating, back-plate will be attached temporally behind the inner-skin then layer up fibers until fit proper thickness. Butt joint method is used for the foam core, before the joint, glue should be applied on the inner-skin then joint with old foam core. The last step, outer-skins are applied on the core. For the less labor, the peel-ply can be applied on the laminated skin.  

The surface should be prepared for the painting. After peel-ply strip off from the surface, there are some shining parts which should be sanded and dusted the surface off. When sanding the surface, the glass should not be damaged.

The painting process is the same as the case study 6.

Haul-out

Haul-out process:  

Haul-out with the travel-lift, generally, a travel lift which is a metal frame and sling the lift belts. It is mounted on wheels, the lift moves into position and the belt lowered under the yacht-hull. The yacht is hanging over the belts and lifted out of the water, and moved onto the cradle in a trailer. For the safe, the yacht should be carefully distributed the load between two belts to avoid from damages.

There are two approach methods, either bow first or stern first (Haulout and relaunch guide, n.d). Before approaching to the travel lift, the lift drive should know which approaching. It is important to the travel lift driver because its lifting belts vary and set up properly with each method. Also, the lift driver should know the lifting position of the boat. The lifting positions are determined by the skipper who indicates the direction, the lifting belt should move to ensure it is correctly placed by the lift driver (Haulout and relaunch guide, n.d).

For the bow-first approaching, the yacht slowly enter in the centre of the pen (Haulout guide, n.d,). The travel lift driver will slowly bring belts. Yacht’s engine should keep running with neutral gear and the skipper also stays in the helm until the engine turned down, advised by lift driver (Haulout and relaunch guide, n.d). The yacht will be gently held by the forward belt until the aft belt has been placed. The lift driver will adjust with necessary.

For the stern-first approaching, the yacht should enter stern first in the centre of the pen (Haulout guide, n.d). Before entry, the backstay of the yacht may be removed. The lifting aft position will be on the lifting point with first belt. The lift driver, then, placed the second belt at the forward lifting position.

The lifted yacht move on to the bilge cradle which is proper for the above waterline repair. As Fig 1, the cradle is ready on the haulage trailer, if the workshop is far from the ramp.

Fig 1 Bilge cradle on the haulage trailer

The yacht placed on the proper cradle, the position could be adjusted with the height of cradle bars as shown in Fig 2. 

Fig 2 Adjust the cradle bars

The yacht should be secured on the cradle then move to the factory for repairing as shown in Fig 3.

Fig 3 Moving the yacht with haulage trailer

The yacht is placed in the factory with the bilge cradle as shown Fig 4.

Fig 4 Yacht is in the factory on the bilge cradle

Re-launching

For the re-launching the yacht, it should move to the ramp with haulage trailer. The process is the reverse way to the haul-out processes. When the yacht has been returned to the water the engine will start. The yacht can move advised by lift driver, the lifting belt should be lowered below than the keel and rudder. 

AL hull and deck Scantling

frame understanding of timber construction (plumb vs. perpendicular)

transportation

transportation

FRP Hull Painting (above and below waterline)

For the resurfacing, clean and degrease the surface very well with liquid rinse. Rinse well afterwards with clean tap water. All old wax residues have to be removed completely. Grind the whole surface with sanding paper grit P150-180 and dust-off and clean with clean cloths. The gelcoat has to be very well sanded, and the surface should be cleaned and well dried. 

Painting system can be coated with two different parts: above and below waterline. The whole painting processes are shown in Fig 1.

[Fig 1. Hull painting process]

For the above waterline, there are two steps, under coating and top coating, and multi-coats are coated in each step (C. Nigel, 2006). Thickness and over-coat interval of each coat is important factor to get expected results it depends on products. In each coat, paint should be well prepared; base should be stirred to lift up heavy settlements then mixed with agent together by product’s instruction (C. Nigel, 2006).

In under coating, it coated on the resurfaced layer with two coats. Undercoat might be slightly sanded for the top coat for each coat. It has tolerance for water, fuel and chemicals however, it is not suitable to apply below waterline. Minor filling and fairing can be done with 400 grit sandpaper for each coat. For the International^® products, Perfection Undercoat^® is recommended with 75 µ WFT for each coat of at least two coats by (C. Nigel, 2006).

In top coating, high performance top coat which is polyurethane can be used to get advantages. Its gloss has twice longer than conventional top coat. Especially, it has tolerance for dark area and heat, water, fuel and oil. However, it is difficult to apply since the high performance coat has shorter wet edge times. Top coat can be processed as the undercoat, it requires clean and gloss finishes. For the International^® products, Interlux super ^® is recommended with 85 µ WFT for each coat of two or more coats by (C. Nigel, 2006).

For the below waterline, high performance epoxy coating system is applied to protect surface from the moisture, oxygen, oil and fuel. Therefore the system can be expected good results in any application especially for the below waterline. To apply epoxy system, the surface should be cleaned and dried with atmospheric condition. For the International^® products, Metallic Primocon3^® is recommended with 120 µ WFT for each coat of 4-5 coats by (C. Nigel, 2006). Epoxy filler can be used for filling and fairing surface after each coat.

The next step is applying antifouling tie coat which is only one coat. To apply the antifouling, mask along the waterline and covered the above waterline with plastic. Antifouling coat is usually applied at least two coats, third coat can be applied to the rudder and alone waterline to protect the wear-out by wave (C. Nigel, 2006). For the international product, International^® Intershield 163 Inerta 160^® and Interswift 655^® can be coated (International_W, nd).

Spray 40

Transom

Spray 40

Hull planking



Spray 40

Planking & Gunwhale