In detail: do-it-yourself fiberglass boat repair step by step from a real master for the site my.housecope.com.
This is not so much an article as knowledge gained in practice in the form of notes.
I started repairing plastic back in my sporting days. When, at the moments of hard drinking, the whole base brought oars to me for repairs, and then boats. Since the boats were beaten often, I had a good opportunity to gain a lot of useful knowledge empirically. Which were then actively used in the repair of hulls of motorboats, boats and yachts.
The main materials for the repair of plastic housings are epoxy resins and various glass fabrics.
There are a great many epoxy resins in the world. Basically, they are all very resistant to external influences after curing. But, as always, you will not find the best thing. Or it stands like a cast-iron bridge. Experiments have shown that for ordinary household compounds, EDP and EKF, as well as automotive epoxy putty (which is also some kind of EKF), are quite suitable for repairing housings. The main thing is that there is an appropriate hardener. EKF after curing gives a more plastic layer. All kinds of industrial compounds, from the category “two buckets of epoxy and a bucket of hardener” are also suitable, but for repairs they are usually not needed in such quantities as they usually are from the factories. And they are extremely toxic. You can get an allergy, or you can get a poisoning of the type of BOV skin-blistering action, smoothly turning into eczema.
Epoxy is best handled outdoors or in a well-ventilated area and wearing medical gloves.
Ideally, epoxy is diluted with a hardener according to the instructions. But experiments have shown that if you stir well, then the compound will set even with a small amount of hardener. It will only grasp for a long time. And the layer will be more plastic. Accordingly, and vice versa. However, the more hardener, the harder and more brittle the layer.
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Sometimes a filler compound is needed for work. At the worst, even dry fine sand can be used in the field. But it is better to buy or otherwise have ground mica or silver. Don't blow silver. It will be worse for you.
If the hardener is not poured into the resin, you can get a lot of problems. The resin usually heats up slightly when the hardener is added. But in my practice there was also the release of some kind of stinking smoke and combustion and just stinks.
Some epoxy grades melt perfectly after curing at a temperature
150 degrees. This can be used if it is necessary to remove the compound from the non-combustible material.
If the compound is heated during polymerization, then it sets faster. We remember the hairdryer.
If you need to press down on a surface covered with a compound, then just put a sheet of cellophane, polyethylene, or better fluoroplastic on top.
Fiberglass is different. I'm not a brand specialist. Therefore, I will explain "by eye". When repairing, you mainly need fabric with an average thread size. Preferably with "oblique" or satin weaving. But the usual one, with a “homespun” weave, will also work. In rare cases, you need a glass wool or glass fiber. They are the same in the thickness of the threads. Differ in weave. For those cases when you need a thick fiberglass weave do not care.
The fiberglass we need should be twisted threads. Will not work with whole fibers. If you shake it, then a cloud of glass pieces should not fly out of it. An operation such as shaking a large piece of fiberglass is best done where there are no people. Downwind. And holding my breath.God forbid you breathe or shake this muck into your eyes or anyone else.
Fiberglass comes in sheets, rolls and tapes. This is a big deficit in sheets. That is, each piece is sealed from all sides. The roll is sealed on only two sides. In principle, the tape is the same roll, but narrow. Usually comes with the most convenient oblique binding, but rarely comes across more than 5 cm.
Currently, fiberglass of various brands is quite often sold in ordinary building materials stores. You can also buy fiberglass from various construction organizations, for example, those involved in the laying of heating mains. Well, or he will come to an agreement with those men who are wrapping this heating main.
To work, the glass fabric must be dry and fat-free. In the field, you can quickly dry fiberglass by calcining it well on a sheet or in a bucket. It will not burn. It is better not to dry over a fire. God forbid it gets smoked. Fiberglass is degreased by rinsing it in any solvent.
Fiberglass must be impregnated before sculpting somewhere. It is necessary to impregnate by repeatedly immersing the workpiece in the diluted compound. After each immersion or “kneading” in the compound, the workpiece must be squeezed out. For example, stretching it between two tightly compressed sticks, tubes, fingers, etc.
The housing must be clean, dry and free of grease before being repaired. In places of repair, of course. in some cases long drying is required. Better with a technical hairdryer. But the hairdryer of your beloved wife and the usual home fan heater will also work.
Typical damage to plastic: 1. damage to the decorative layer 2. cracks in the case 3. “half-holes” 4. holes 5. diverging “corners” 6. shells 7. all this together
Damage to the decorative layer - minor damage. A scratch that does not damage the layer through and through is simply primed with GF primer or epoxy without filler. It is sanded and painted over. A through scratch, even if the case itself is shallowly touched, is putty with a compound with a filler. It is sanded and painted over. If the decorative layer falls behind, then it must be peeled off to the point where it is firmly adhered to the body.
The inside of the case is usually just painted. This is true. On a note.
Never work on the edges of holes. Let them frown better. It will be stronger.
Where the fiberglass will lie, the case should be cleaned along the first layer of fiberglass on this side, so that this layer is slightly brushed. Even if it was torn in places. This is best done with a coarse sandpaper wrapped around a block of wood, cork or finely porous foam.
The fiberglass sheet must be glued so that the edges are smoothed out and do not fall on the paint or decorative layer.
It is better to take your time when working. And in advance, figure out how to put the body in the right position. Bo is most convenient to do something if the working area is horizontal. And if there is a need to glue a large piece of fiberglass, then the only way to put it right is to place the surface horizontally or close to horizontal.
Half-hole is vile damage. This is a break in the case in which the piece of plastic remains mostly attached to the case. Not with a flap, but more precisely. In general, an abomination. We clean on both sides. Then we figure out whether we will be able to put the piece in place. This usually works with small breaks. If there are no chances, then it is better to remove the piece. Get a normal hole and repair as described below. If the piece itself is damaged, then you also need to remove it. But you can try to straighten it. We coat all surfaces with compound and put a good stop on the side of the direction of impact. Preferably with a thick rubber gasket. On the other hand, with a mallet, carefully put the piece in place. It will never work exactly in place, but you have to try. As a result, we get a dent on one side and a bulge on the other.Immediately place a soaked piece of fiberglass on the bulge. And we fix it with a spacer or load. When everything is polymerized, we begin to process the dent. Putty with resin with filler. After hardening, we grind. We glue the impregnated sheet. We grind. cover with a thin layer. We grind and paint.
For a good seal of the hole, a punch must be made. For example, from foam. This is necessary in order not to disturb the contours. Better if it is a punch along the outer contours. This is exactly the case when thick fiberglass is needed. We process the edges. That is, we remove the paint and lightly brush up our native fiberglass. We cut out several patches from the glass crimp, with a minimum (3-5mm) overlap covering the hole. The number of layers should be chosen by eye on the assumption that the thickness of the package should correspond to the thickness of the case. We put the punch. We glue the patches in layers. Each layer is allowed to dry until the resin is semi-polymerized. And no bubbles. After that, from the inside of the case: grind, glue another layer, grind, second layer, grind, cover with a layer of pure resin, grind, paint. Put one layer outside and process it in the same way.
The separated corners are glued in the same way as for sealing cracks. But it's best to use tape for them. It is advisable to put the corners in the transom on the knits. Knits are made of plywood or plywood tank. They are carefully adjusted according to the mating angle. First, the knit itself is glued in. Then it is pasted over with fiberglass. For example: on the transom of Ladoga-2, two knits with a side of 100 mm were placed at the joints with the sides. At the bottom joint, three on each side. Of course, all the places where the fiberglass fits are thoroughly cleaned to the first native layer.
No one has come up with anything more disgusting than shells. The shell in the laminated plastic is either a factory defect. Or is it the result of water getting between the layers of the hull. This usually results from damage to the outer layers. After a couple of hibernations, the freezing water expands the layers. If this shell is closer to the inner side, then we can assume that the entrance to it is from the inside. It's better to score on such damage. If it is closer to the outside, then it must be repaired. The main problem is that the sink is very difficult to dry. therefore, in order not to wait a month in the sun, the sink needs to be opened. From the side of water entering it, we drill a hole
8-10 mm. Depth before entering the cavity. With a wire or any other thin and flexible object, we determine the true dimensions of the shell. We open the shell with a knife or "claw" from a hacksaw blade. We make it wide enough, up to 5 mm. cut along the largest shell size. Several parallel cuts are possible. If the width of the sink is more than 100-120mm Through the cut with a dry hair dryer. Then we drive in as much compound as possible with a syringe. The most important thing is that the sink must then be clamped over its entire area in some kind of press. Or strut and support. Or with a clamp with large coverage. Or a load. Well, the favorite process of putty is sanding and painting after polymerization.
Owners of fiberglass motorboats, boats and yachts often complain about fading of the initially bright and glossy surface, bubbles and cracks on the bottom that increase water resistance to movement, increase fuel consumption (see this page for fuel saving methods).
This damage occurs in the outer decorative (pigmented) binder layer, which is sometimes referred to by shipbuilders gelcoat (from English gelcoat). This layer is a film with a thickness of about 0.6 mm, which is formed after polymerization of the colored binder layer applied to the matrix surface first - before the main layers reinforced with glass fiber or glass cloth are laid in it.
In addition to painting the body in a certain color, the gelcoat also performs another, even more important function - to protect the laminate, i.e.the internal main layers of glass material from the penetration of water to them, from the formation in the microscopic voids and channels, which are always present in the thickness of the glass material, acid solutions of substances that make up the binder. For this reason, under especially unfavorable storage conditions of the vessel (mainly on the water, at high water temperatures in summer and frost in winter), as well as with insufficient attention to the state of the decorative layer, the service life of the plastic hull of the boat can be significantly reduced - up to 8-10 years old.
The main principle of caring for the decorative layer during the operation of the vessel is the timely elimination of foci of osmosis development and the restoration of the water-protective functions of the gelcoat.
The phenomenon of osmosis is a change in the concentration of an acid solution in the voids of fiberglass (caverns) due to the filtration of seawater molecules through a semi-permeable gelcoat film. Recall that during osmosis, a solution of high concentration in the caverns, as it were, sucks up the molecules of the solvent - the seawater. As a result, the pressure inside the caverns increases to 5-6 atmospheres (the so-called osmotic pressure), the gelcoat film first swells - in the form of bubbles, and then bursts, forming cruciform cracks. Through the cracks, seawater penetrates to the layers of the laminate, and the process continues to develop already in the strong layers of fiberglass. The decorative layer gradually crumbles and peels off.
This process develops over a rather long period - from several months to 5-8 years. In the initial stage, the bubbles on the decorative layer may be quite small in size: for example, they will be the diameter of a pinhead. Such bubbles do not interfere with the protective function of the decorative layer, unless they cover significant surfaces. It is not required to immediately remove them and restore the decorative layer, but no more than 4-5 months later, it is necessary to carefully examine the same places and evaluate the development of the size of the bubbles and the total area on which they were found.
a - bubbles; b - delamination and cracking.
1 - closed bubble; 2 - cracks in the top of the bubble - the result of osmosis; 3 - open cavity;
4 - lagging edge of the gelcoat; 5 - exposed fiberglass of the main layer (laminate).
In the further course of the process, the bubbles are arranged in the form of chains or combined in the form of rolls, and the chains and rolls are usually oriented along the fibers of the upper layer of the laminate. Then a crack forms in the decorative layer, and this already requires immediate repair.
It is also necessary to pay attention to separate large bubbles with a diameter of 5-15 mm. They are easily detected on the surface of the hull immediately after the boat is lifted ashore, especially in hot weather. If you pierce such a bubble (for example, with an awl), an acidic solution flows out of it. During a long stay on the shore, the solution can partially evaporate through the pores in the decorative layer, the bubbles are smoothed out, and in spring the damaged spots can go unnoticed.
The need for repairs can be judged by the state of the fiberglass under the bubbles, for which they should be removed with sandpaper before opening the cavity. Immediate repair is required if dry, binder-free fiberglass is found in the cavity. Sometimes even fine white dust is present. Such cavities, as a rule, penetrate deeply into the main layer of fiberglass; the solution in them can remain for a long time after the boat is lifted out of the water. If these defects are left unattended, after a certain time the outer cladding at their locations will be weakened, and laminate delamination may even occur (especially after exposure to negative temperatures).
a - the top layer of the laminate is well impregnated with a binder, b - with a "dry" layer of the laminate;
c - laminate delamination.
1 - decorative layer; 2 - laminate; 3 - destroyed fiberglass;
4 - cavity inside the laminate.
Bubbles larger than 5 mm in diameter must be removed, even if opening reveals a laminate that is sufficiently well impregnated with the binder. This is all the more important if cracks appear in the gelcoat.
More harmless damage to the decorative layer in the upper part. The white gelcoat becomes dirty over time, turns yellow under the influence of ultraviolet rays. Gelcoat of other colors is covered with a white bloom, the surface becomes dull, untidy looking.
The shiny surface can be restored by periodic cleaning and painting, without intruding on the decorative layer. Preparing a fiberglass body for painting does not differ in principle from similar work on wooden or metal bodies, but it is worth noting some specifics.
When forming the body, the surface of the matrix before applying the gelcoat is covered with a separating layer - a special suspension of wax, polyvinyl alcohol, etc. This layer is only necessary so that the molded structure does not stick and it can be easily removed from the matrix. However, traces of this release layer remain on the front surface of the structure for quite a long time; if they are not removed, no paint will stick.
During the operation of the boat, caring owners carefully polish the outer surface of the hull using various types of pastes containing wax or silicone. These substances are embedded in the pores and microcracks of the decorative layer; they must also be removed before painting.
The surfaces to be painted must first be washed with warm soapy water and cleaned from coarse dirt using white spirit, solvent or other slow-drying solvent. Acetone or industrial alcohol are unsuitable, since when using them, the separating layer substance will not be removed, but simply redistributed over the surface. For the same reasons, you should often change the cloth soaked in solvent, and finally wipe the surface with a clean dry cloth.
Using an emery cloth of medium grain size, it is necessary to sand the area to be painted so that it acquires an even matte, slightly powdered surface.
Keep in mind the small thickness of the decorative layer! You should not make too much effort. If an electric drill is used to facilitate the work, it is better to put a rubber disc under the sanding cloth. After sanding, you should carefully remove the dust from the surface (with a vacuum cleaner, and then wipe the surface with a clean cloth moistened with solvent).
When carrying out skinning work, the safety rules must be observed. It is necessary to work in goggles, a headdress and a mask made of gauze, which prevents dust from entering the respiratory tract; it is not recommended to smoke, drink or eat. This is especially important if you have to remove the old layer of antifouling paint from the underwater part, which contains poisonous copper compounds. At the end of work, clothes are thoroughly cleaned of dust; it is best to wash them immediately.
If waterproof sanding paper is available, it is best to apply wet hand sanding. Small scratches are removed with a skin; tiny bubbles can be ignored.
If dirt remains in the crack after sanding and dusting, this indicates that the crack is deep. In this case, it is better to carefully cut it (within the thickness of the decorative layer), dry it well (for example, using a hair dryer), degrease it, and then putty. Only after the filler has completely polymerized can the repaired area be sanded down again.
Sometimes deep cracks also cover the layers of the laminate. Typically, such cracks appear due to local stress concentration in the skin or any design flaws.In such cases, it is important to first find out the cause of the formation of cracks and eliminate it by distributing the load over a large area or by molding additional structural elements, and only after that to close the crack itself. You may have to slightly expand the repair area and go deeper into the laminate. To restore the damaged strength, several layers of glass material - fibers or strips of fabric will need to be laid in the cut place.
Bubbles with a diameter of more than 5 mm in the underwater part of the case must in all cases be opened, the cavity removed from the liquid, rinsed with fresh water and dried. With large bulges in the gelcoat, you should determine the boundaries of the cavity (using an awl), then open the decorative layer and, after cleaning, drying and degreasing, putty the damaged area with an epoxy binder. If delamination of the laminate is found, then after thorough drying, a binder with a hardener is injected into the existing cavity through a carefully drilled hole using a syringe. Any excess resin that has come out must be removed immediately with a dry cloth.
Where the gelcoat has peeled off from the laminate, remove all cracked and loose edges, i.e. loosely adhering to the laminate, by prying them off with a spatula.
1 - spatula; 2 - putty area;
3 - a layer of cellophane or polyethylene film.
After processing the sink, it is filled with putty, a cellophane or plastic film is applied on top and the putty is smoothed with a spatula through the film. In this way, it is possible to obtain a smooth glossy surface that requires minimal labor for grinding. If possible, the film should be well pressed to the surface and not removed until the end of the polymerisation of the binder.
Various polyester putties (fillers) can be used to seal the joints of the decorative coating. These are two-component (base and hardener) polymer compositions that are very easy to use and allow you to get a high quality repair.
Before use, the filler is first thoroughly mixed until a homogeneous mass is obtained. Then add the hardener MEK (methyl ethyl ketone) and mix again thoroughly. Now the putty is ready for application, but remember that its pot life is limited to 20-30 minutes (at normal temperature), so work should be done promptly.
After the binder has hardened, the place to be repaired is first sanded with a medium-grained sandpaper, then wet-sanded with a fine waterproof sandpaper until a smooth surface is obtained. After finishing the treatment, wash the surface with warm soapy water, dry it, wipe it with a cloth soaked in white spirit. An hour later, you can start painting the case.
Note that all work on the repair of the decorative layer and painting must be carried out in dry warm weather, protect the surfaces being repaired from moisture. If it is not possible to place the boat in a boathouse or under a canopy, you need to take care of the local protection of the repaired section of the sheathing from moisture and dust by covering it with plastic wrap. It should be painted within no more than 24 hours after finishing the surface preparation, otherwise it will have to be wiped and degreased again.
To protect the bottom of ships that are in the water most of the time, a layer of XB-53 or XB-79 antifouling paint or imported paints - "antifoulings" are applied over two layers of ordinary paint.
Stir the paint thoroughly before use. During operation, the paint is periodically added to the supply container and mixed each time. Small surfaces are painted with a brush. With a large area of the painted surface, it is better to work together: one applies the paint with a roller, and the other evens it out with a flat brush - a flute.
You should not try to cover the surface in one go.The coating will be more durable and reliable if you apply not one, but two or three thin layers with intermediate drying. With natural drying, a break between layers of up to 24 hours is required; when using reflector lamps, 2-3 hours are sufficient to dry.
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Fiberglass rowing boats 4.3-meter "Pella" were produced by the plant "Pella" (Leningrad region) for many years, starting in 1971, and the last - the third modification ("Pella-fiord") in a small series has been produced until recently ... At many rental stations, tourist and hunting bases, thousands of such boats are still in operation, and decisive measures are taken every year to prolong their life. Most often, for example, they protect the worn keel and the lower part of the stem by applying a steel channel, and the upper edge of the bead in the area of the oarlocks, which “breathes” when rowing, is reinforced with a piece of square on three or four bolts. At the request of the editors, two specialists who were involved in this work at the Priozerskaya camp site share their experience of repairing Pella boats.
“The boat is not a cart, it doesn’t jump over rocks,” - this is the rule the designer usually follows, not wanting to take into account the fact that most often a small rowing boat is operated near land with daily and repeated pulling out onto an unequipped shore, sometimes rocky, and most often without special sledges or carts. Especially harsh operating conditions for boats at rental stations and tourist centers, where the boat does not have a permanent owner.
A reasonable designer, naturally, will take care of the maintainability of his brainchild. However, the plant - the builder of a large series - is trying, first of all, to significantly simplify the structure, taking care of reducing the cost of construction.
The struggle for "manufacturability" affected, in particular, the boat "Pella", which is popular with us. Let us sequentially consider her “sore” spots and methods of their treatment, keeping in mind mainly the second model of the boat (a series of over 25,000 pieces). We will also assume that such repair operations as sealing holes, deep cuts and dents usually do not cause difficulties (and, moreover, they have been repeatedly considered on the pages of "KiYa").
1. The plastic protective profile does not hold on the outwardly molded bead flange, it jumps off; then the flange itself begins to collapse, especially intensively - in the widest part of the hull, where the nests of the oarlocks are located. When mooring at the boom, when people boarding, the boat, swinging, touches the protruding flanges for other boats, the attachments of the protective profile are loosened, and at the same time what it is attached to. This flange does not have any reinforcements fore and aft.
There are two solutions. The first and most successful one is to remove this flange (cut it off with emery), and instead install a fender bar made of glued wooden slats from the inside. After careful grinding, this bar must be pasted over with fiberglass, overlapping the upper outer edge of the bead with fiberglass. The fender should have reliable horizontal braces - bristles connecting both branches at the bow end. The same knits should be at the stern, connecting the sides and the transom.
The second method is that the re-glued strips are installed on the sanded surfaces outside the upper edge of the bead and the lower surface of the flange and, after stitching and grinding, are pasted over with fiberglass. The bottom surface of the fender guard must be sloped to prevent it from trapping with other boats or booms.
In the same way, it is necessary to repair all illiterately built watercraft, including boats, lifeboats, yachts.
2. Place a metal plate from the inside under the bow mooring eye to unload the knot.
Better yet, install an additional eyelet near the waterline. It will be much more convenient for this lower eye to tow the boat.Even a submerged or capsized boat during towing will necessarily turn down the keel and get a trim aft, the water will begin to drain through the transom. When you stop, the water will be evenly distributed throughout the boat, which will allow you to direct a person to it to pump out the remaining water.
3. The location of the blocks of buoyancy does not ensure the safety of navigation, since when the boat is flooded, emergency stability is not preserved. Tourists and boat owners may be advised to pack their gear in an even number of waterproof bags and tie them in pairs over rowing cans closer to the sides.
It makes sense to remove the foam from the buoyancy compartments (usually soaked in water) in any way and replace it with a set of plastic bottles tightly sealed with corks. You will be able not only to control the state of “buoyancy reserve”, but also to replace bottles as needed. In addition, the entire space will become available for repair, drying and cleaning from dirt. But it is better to secure the “buoyancy reserve” securely along the sides under the gunwale.
4. Keel with soft foam core causes deep sadness. It often happens that when the boat is pulled ashore, the stern (or bow) is still floating, and a significant part of the load is taken up by a small area, almost a point, which leads to keel damage and wear.
Real tourists take not only scotch tape with them on a hike, but also cans of pitch and grease the holes with rags with resin.
On boats belonging to tourist centers, we advise you to cut out the foam together with the horizontal belt of the worn out - worn out - fiberglass, clean the formed groove with emery, insert and glue a steel profile with a square section with a wall thickness of 2-3 mm (such profiles are now widely used in light building structures). Holes are made in the horizontal shelves: at the bottom - 25-30 mm, at the top - 5-6 mm. Through them, the profile is bolted to the inner strip, and then filled with bitumen, PSB foam or any other material that prevents corrosion. The holes in the bottom shelf must be plugged with plugs, after which you can put the outer cover - a steel strip.
On boats of private owners, it makes sense to replace the foam with a wooden bar impregnated with an antiseptic, and again paste over it with fiberglass.
Working on two bottom stiffeners - corrugations - is simplified, since there is no foam. Fill the cavity with fiberglass and resin. From the inside along the stiffeners (as well as along the keel), lay wooden or metal strips, fastening them to the outer plates. With wear and tear, the wooden outer linings are easy to replace without making a "major" repair.
Another knot that usually needs to be repaired is the reinforcements under the ends of the wooden cans, which lie on the molded side ledge. Outside, under the horizontal shelf, it is necessary to lay a triangular beam glued from the rails and glue it over with fiberglass. You can limit yourself to filling the corner with fiberglass putty.
5. On "Pellefjord" (this is the third model, mastered in 1985) there are no bottom stiffeners - corrugations - but there are forward and aft blind bulkheads. This local increase in rigidity is not at all a positive role. When, when pulling the boat ashore, an obstacle in the form of a stone (logs, driftwood) appears under the sinking bottom, there is a real danger that it will push the bottom first in front of the bulkhead itself, and then immediately behind it. To get rid of this danger forever, we advise you to cut off the lower part of both bulkheads so that they do not touch the outer skin of the bottom at all, but rest without rigid attachment only on the longitudinal rigid connections of the bottom.As such connections, put keelson on the DP (you can use a square metal profile) and one on the side - the stringer opposite the false sheets installed outside (wooden slats with a lining).
Reinforce the keel, install fenders and replace the buoyancy blocks as recommended for Pella.
The repair was carried out using polyurethane glue and glass fabric T11-GVS-9 by a specialized team led by V. Alekseev.
Fiberglass, the material from which they are made, is prone to chips, cracks, dents. The most severe damage is the hole.
Often cracks and chips occur during dashing mooring to the shore, when the ship's hull meets stones or other obstacles.
It is quite possible to repair all the damage to the plastic boat with your own hands. No special repair tools are required, it is only important to choose the right consumable.
Serious hull cracks usually occur after a significant boat collision. Simple, small cracks, this is most likely damage to the decorative layer.
Damage to the decorative layer, minor scratches and cracks will be enough to putty. 
It will be possible to do it better with special putties, which include fiberglass. A distinctive feature of such putties is their increased elasticity, which allows them to be applied neatly. I will give a few examples of such putties:
Any type of putty is applied to a well-prepared surface, which must be carefully sanded and degreased.
Putty putty is applied in a thin layer, as many times as necessary to achieve the desired result. Each layer must dry, it is sanded, and only then the next layer is applied.
After the putty is covered with a primer and painted. 
You can also use a one-component nitro-filler type NTs-008. It is intended for wood and metal, as well as for leveling dents along the enamel, for small cracks along the outer layer it is quite suitable.
Many materials are now available that were little known. For example, gelcoat is a liquid substance that is applied over glass cloth with resin, the thinnest layer from a spray bottle. After drying, such a layer of gelcoat will give a glossy shine and create additional protection for the plastic from mechanical stress and an aggressive aquatic environment.
Small cracks are also sealed with gelcoat. The drying time is 20 minutes, so it must be diluted in small portions. As soon as the gelcoat changed its viscosity and clots appeared in it, it was no longer possible to work with it.
If you do DIY plastic boat repairs, you will come across a variety of fiberglass on the market. 
Fiberglass is available in various thicknesses; structural fabrics, such as glass satin, fiberglass mesh, are suitable for repair. There are also glass mats. Glass mat is a non-woven fabric made from chopped fiberglass.
It is advisable to use glass mat for the restoration of large holes or reinforcement of the boat hull.
To patch holes or update the case, you will need to take glass mats. Plain fiberglass is used for minor repairs and for reinforcement.
A prerequisite is the cleanliness of the fabric, if moisture, dust or dirt gets in, then there will be bubbles on the boat.
In order for the fiberglass not to come apart ahead of time, it is treated with paraffin, which must be disposed of. There are fabrics without paraffin, it is better to use them.
To remove the paraffin, the fiberglass is heated with a hairdryer.
If a large amount of fabric needs to be removed from paraffin, for example, to strengthen the entire body, then it is better to boil it down. You can boil it like this: pour water into a bucket, add soda ash, put glass cloth and lower the boiler. This can be done in the kitchen too. Boil the fabric for 20-25 minutes, let cool.The paraffin will float up and harden. Pull the fabric out and dry.
For fiberglass, both polyester and epoxy resin are used.
To repair a plastic boat, take an epoxy one, since it "sticks" better to the old hull, its adhesion is higher. The time for her to solidify is 2-3 hours, which allows her to carry out all the repair work. 
In the manufacture of plastic boats, polyester resin is used; it hardens very quickly in almost 15 minutes and becomes like glass.
In order for the resin to be sufficiently viscous, it is necessary to work with it at a temperature of at least 20 degrees.
If the resin is thick, you can warm it up a little.
Dilute the epoxy resin in a ratio of 10: 1, where 1 part of the hardener.
In the event of more serious damage: deep scratches, torn cracks, holes, plastic boats are repaired using fiberglass, resin, hardener and plasticizer (dibutyl phthalate). 
The shaggy edges of the crack do not need to be trimmed, the protruding fibers will help the resin to adhere better to the hull.
Dry the boat hull before repairing it. Although it is said that plastic does not absorb water, it is not.
Since the main condition for high-quality repairs when working with resin is the complete absence of dust and debris, it is better to carry out repair work indoors.
For good hardening of the resin, the temperature regime is important, the optimum temperature for such work is 18-20 degrees. If there is no wind and rain, then it can be repaired outdoors. All work should be carried out with gloves.
To avoid smudges, the surface on which you will glue the fiberglass should be located horizontally.
The process of gluing fiberglass will be as follows:
- Sand the body to an undamaged fiberglass layer, the scraped edges do not need to be leveled, the shaggy pieces will provide a more thorough adhesion.
- Add a hardener to the epoxy.
- Spread the resulting mixture on the surface that must be pasted over, smear with a brush, do not spare the resin.
- Apply dry fiberglass and smooth it out so that there are no bubbles and creases.
- Remove excess resin with a spatula on top of the fabric, it is very important not to allow smudges.
- After 3 hours, spread on another layer so that the surface is perfectly smooth.
- Sand once completely dry.
Cover the top with a putty for plastic with the obligatory degreasing of all surfaces for better adhesion.
If, nevertheless, air bubbles formed in the process of working with fiberglass, then they must be cut and re-glued.
If the crack in the case is deep, then the resin-impregnated fiberglass should be tucked into it as tightly as possible.
If this is a hole, then glue the fiberglass from the inside of the boat's hull, and install the matrix from the outside.
By the matrix is meant a part made of polystyrene, which will repeat the boat's hull from the outside. Since you need to make a fiberglass layer commensurate with the hull of the boat, you need to take thick fiberglass.
The process of patching the hole is the same as applying layers of fabric to small cracks, only there will be more layers and each layer requires sanding.
The sequence of the repair can be seen in the video:
