VI. Removing the Power Set / VII. Removing the Gelcoat
VI. Removal of the power set
In this boat, the power set is presented in the form of a spatial fiberglass stringer, a rotten oak reinforcing beam under the deadwood and a propeller shaft bracket. All this must be carefully separated and removed.
According to the vessel reconstruction project, the stringer remains original, without modifications due to the labor intensity of manufacturing hollow spatial parts without matrices and dummies; the foundation for the new engine will be metal. Molding a new engine foundation and reverse gearbox to a dented stringer is not a good idea. Yes, you heard right, the engine mounting points on the stringer were dented. The previous owner tried to fix the situation with aluminum plates and polyurethane foam, but it did not help. The fastening of the old and new power units is very different, so we leave the old stringer as a hull reinforcement.
To remove the internal elements, we will need metal plates with single- and double-sided sharpening, used earlier when separating the hull shells from each other. In hard-to-reach places, you can use a “trembling” tool (oscillator cutter, renovator, Oscillating multi-tool, etc.). Do not use an angle grinder. There are 2 reasons for this: Destruction of the mating edge (edge) of the fiberglass element, with which it is molded to the body, which will further complicate its positioning. The second point is related to safety and another cleaning in the workshop. When working with an angle grinder, even with a very powerful vacuum cleaner, fine, prickly fiberglass dust will settle evenly throughout the workshop.
The stringer is molded in pieces: fiberglass strips, which we must cut, separating the element from the body. First, we cut through the molding with a tool, install a second plate next to it and gradually go the entire way. The first plate creates tension and lifts the separated element, the second cuts through the molding. You can also go along the molding, cutting it with one plate. Then the molding itself must be removed.
In the same way, oak and plywood reinforcements and embedded elements are removed.
By the way, a very important point. Before removing a power element, it is necessary to measure the relative position of the elements relative to what will not be replaced (for example, a boat hull) and transfer them to a sketch, a drawing, and indicate many complementary dimensions. Additionally, you can use markers with paint and mark the elements. Circle them. Draw lines passing through both elements: removable and non-removable. These operations will help the future assembly to position the elements relative to each other. When using a 3D scanner, it is also advisable to perform this operation because it speeds up the process and allows you to double-check everything.
Don't forget to take pictures of everything as you work.
After removing the elements, there remains a molding that must be removed. Removal is done using the same tools: a chisel and a chisel. Carefully cut off unnecessary elements without going deep into the hull. The tool is always parallel to the surface. Under the removed elements we will find a lot of dirt, earth, oil. This means that the next step will be a thorough wash of both the elements and the boat. The technology, as in the previous chapters, is high pressure washer, harsh chemicals for washing the engine, hard brushes and a lot of patience.
Important! Don't forget to blow out and dry the hull after washing. It is necessary to use a sink, but do not forget that fiberglass (polyester) does not like water. For this reason, you should always dry the boat and not let water stagnate inside, blow it out with an air gun. It is possible to use mud cutters for washing, but carefully, otherwise you can cut the laminate. To remove water, use the drain holes in the body and a construction vacuum cleaner with the ability to suck in water.
After washing, there is a scanning stage to get a complete picture: a 3D model of the outside of the hull, inside with an engine, without an engine and without a power set (if necessary). 3D scans are superimposed on each other and the relative position of the elements is studied, how much the central planes of the elements coincide with the diametrical (central, longitudinal) plane of the boat.
We also have a clean hull and its components.
VII. Removing the gelcoat
Next on the plan is removing the gelcoat and paying close attention to those areas that we didn't like during the initial inspection and previous work.
What is gelcoat? Gelcoat is a special compound that is used to create a protective and decorative coating on the surface of fiberglass products. It is a viscous paste containing resins, pigments and additives that provide strength, resistance to ultraviolet radiation and atmospheric influences.
It is usually applied to the mold before pouring fiberglass, forming a thin layer that gives the product a smooth and aesthetically pleasing surface. It is widely used in the production of yachts, cars and other composite products. If the integrity of the outer coating is compromised, water gets inside and an endless process of osmosis begins. If there is no access to water (the boat is not in the water), then some water can come out of the hull, but such drying is not very effective. In any case, first you need to remove the areas with cracks to see the extent of the damage.
I recommend removing gelcoat only with orbital grinders. And only with them! The reason is simple. Other “highly effective” tools can easily “dig holes in the hull”, thereby changing the contours and ruining the symmetry of the hull. It is problematic and time-consuming to check each point of the surface later, so the likelihood that this will be done is minimal. My position is to do no harm. Therefore, the gelcoat must be removed carefully, controlling the depth of immersion and following the contours of the hull. It will be effective to use disks with an abrasive grown by electrolytic method. The removal result is predictable and the durability is higher than that of abrasive material obtained by bulk method. Let me remind you that our project is large-scale and we are regenerating the hull, so in any case we remove all the gelcoat. Don't forget about the vacuum cleaner attached to the tool and personal protective equipment (full face mask or half mask + glasses)!
Usually only damaged areas are cleaned. Cracks, impact marks, etc. with subsequent repair of damaged areas and the use of repair compounds to restore gelcoats.
Don't forget to take photos of everything as you work and measure distances.
After removing the gelcoat, you can see suspicious wet spots with a sticky substance in them and an unusual smell (styrene). “Congratulations”, — this is osmosis! Osmosis is the destruction of the laminate of a fiberglass structure, — it is an irreversible process in which moisture penetrates through the membrane layer (gelcoat) and reacts with the chemical substances of the laminate. During the reaction, the volume of substances decreases, i.e. a void is formed in the place where the laminate was. Even with microcracks in the gelcoat, water penetrates abundantly into the laminate structure due to the high hydraulic pressure from the outside (the boat is usually not stationary, but moves through the water).
Where do microcracks in gelcoat come from?
Hull made of fiberglass using polyester resin “flow”. They change their shape, they are very flexible. In the sun and without the sun, the dimensions change. Accordingly, the coefficient of thermal expansion of such fiberglass laminate is very different from that of hard gelcoat, hence the formation of stress in the layers of the outer coating and laminate and the formation of microcracks. The second possible reason for the formation of cracks is the thickness and its unevenness when applying the gelcoat to the matrix during hull molding. The thicker the gelcoat layer -> the more stress -> the greater the probability of destruction.
Globally, there are only two reasons for the formation of microcracks in gelcoat. The first is the use of polyester resin; the second is the use of gelcoat. Is it possible without them? Can! But more on this in a separate chapter below.
After removing the gelcoat, it became clear that several places were relatively deeply affected by osmosis - 1..2 mm. I decide to remove the outer 1-2 layers of laminate. This is necessary to align the laminate and exclude suspicious places. For more convenient work, the lower shell must be turned "upside down". We also work with osmosis - we remove it instrumentally (cut out, clean inward, deep). For this we use dremels, drills and necessarily a vacuum cleaner and personal protective equipment. You can imagine yourself as a dentist when removing caries on teeth =)).
Next, we remove dust from the hull. We thoroughly clean out all the debris with a vacuum cleaner and then blow it out with an air gun. Don't forget about PPE!
If your workshop doesn't have a good large screw compressor and good filters that retain moisture and oil in the supplied air, you can limit yourself to a vacuum cleaner. It is better not to use household ones, but construction ones are just right.
After that, we cover everything with thick polyethylene and go to rest for the weekend. Regarding polyethylene, we always do this when there will be no work the next day. The body must be protected from dust and dirt.