DE2623188A1 - Boat hull of GRP and foam core sandwich - made by winding round mould and sectioning for removal - Google Patents

Abstract

Boat hull or other hollow article e.g. pipe or container, of sandwich wall construction, is made or an internal mould by winding layers of lay-up matl. completely round the mould. An inner layer of resin impregnated fibre is followed by a core layer of synthetic foam matl. and an outer layer of resin impregnated fibre to complete the sandwich. The moulded article is cut into two sections for removal from the mould which has a release coating. The numerous draw-backs in boat construction of laying up on a plug type mould are avoided and building simplified. The present invention enables tension to be applied so that no distortion occurs. Fasteners are not needed. Quick cure resin can be used without styrene release from the resin onto the core. There is not waste of matl. The mould is immediately re-usable.

Description

Method of making boat hulls and other hollow

Objects. n The invention relates to a method of manufacturing a boat hull or other hollow objects.

Plastic reinforced with foam, commonly known as FRP, is used for the manufacture of boat hulls.

FRP consists of a core with a low specific weight between two outer shells made of a material with a high specific weight. The core is made in the desired shape and the outer layers are made mechanically connected to this. The core material must have sufficient rigidity and have sufficient shear strength to space the outer layers to keep from each other. PVC foam is an example of a core material of these Art, which also has the ability to return to its old form after being subjected to pressure return and is therefore resistant to vibrations. PVC foam, fiberglass and polyester resin are typical materials that are suitable for sandwich constructions.

A well-known method of sandwich construction used in boat building is used is referred to as a "core punch" or "positive molding process". This Procedure V ^ erfren consists in a To make a stamp or a mold, which has the shape of the boat hull, the top of which points downwards and is attached to a level floor. It consists of formers or ribs that are parallel arranged to each other and on which slats are attached in the longitudinal direction. the Slats are a few centimeters apart. PVC foam boards will be cut, trimmed for the shape and stretched, heated or preformed, like that that they envelop the shape almost all around. These PVC foam strips are then made attached to the wooden slats from the inside of the mold with wood screws or with headless nails or pins that pass through the foam and outside the slats are driven in to securely attach it to the slats. Everyone Foam strip is butted against the strip that is already attached to the mold until the entire surface of the trunk is covered. Afterward the gaps and the butt joints between the foam strips with thin Mortar filled and sanded at the front, using them for the application of the outer skin are done.

This is followed by an outer coating made of GRP with a fast-curing polyester resin that adheres to the surface of the PVC foam is applied. Then there are layers of fiberglass in the form of fragmented ones Mats in which the fibers either run in one direction or form a fabric. The mats are moistened and fully impregnated with polyester resin. The surface learns at this stage usually by sanding it smooth Finish.

The fuselage, which is made of PVC foam with an outer skin made of GRP, is then removed from the wooden form. Screws, nails or fasteners will 'be removed from the inside to remove the inner surfaces of the foam from to loosen the wooden slats. The fuselage is then lifted off the mold, turned over and set up in an upright position with the help of appropriately trimmed wedges.

Then an inner skin made of GRP is applied in a similar way like the outer skin in order to create a "sandwich" of PVC foam between two in this way Manufacture shells from GRP, which are mechanically attached to its surface.

The production of the deck or the head part of the hull is carried out either in the same way as making the hull or on special boards about supports.

The disadvantages of the positive mold process are as follows: a) The trimming and cutting the foam into strips into curves with different radii of curvature is arduous and requires a lot of skill.

b) Certain parts of the PVC foam must be under different stresses attached to the wooden slats of the form will. Because while hardening Heat is generated from the polyester resin, the surface of the PVC foam, which is in Contact with the applied GRP layers is, heated, which increases the strength of the foam is reduced. At the same time the surface coating hardens a shrinkage. This creates tension in the surface when the skin hardens of the fuselage. If a slow-curing resin is used to seal the To reduce heat transfer from the coating to the foam, so there is the risk of styrene escaping from the synthetic resin, penetrating into the foam and causes a softening and a similar twist, especially there, where pressure was applied to create a tight fit between the foam and the mold reach.

c) The application of a GRP coating to a solid form calls at the transition from the horizontal in the middle of the trunk to the vertical the gunwale line unavoidable changes in the coating and a corresponding one Committee before.

d) A prescribed inspection of the coating on the exterior and the inside becomes problematic when scaffolding is required to keep the Workers apply the plastic and the fiberglass material to the entire surface of the Can apply the fuselage. When working on the inside of the GRP skin, a must have special ventilation must be provided.

e) Enables the usual use of a slow-setting resin it allows the worker to finish a coating of fiberglass so that this can partially harden before the subsequent layer is applied. In this Case it is necessary to grind and rough corners from the partially hardened Remove surface areas between the individual coating processes.

f) Removal of the wooden core mold easily damages the hull itself, as well as the insides of the foam.

g) The lifting, turning and lowering of the partially completed The fuselage for coating the inner surface requires time and time from the workforce Experience. This also includes aligning the trunk in its upright position, so that tensions in the subsequent application of the inner skin are avoided.

h) As a result of the above in sections a), b), c), d), e) and f) That said, a considerable amount of filling and sanding work is required in order to to achieve a surface condition comparable to hulls that pass through other processes were made. The positive form method is commonly used for used to manufacture only one hull or a small number of hulls. In addition, the structural advantages of the single-shell sandwich construction, in this way curves with changing radii of curvature achieved as well as the simplicity of using the local zones of the hull woven from glass or reinforced in one direction glass fibers, The cost must be balanced against the effective monitoring of the coating and causes a surface finish.

The object of the invention is to create a method for the manufacture of a boat hull, in which the advantages of the sandwich construction are retained, but their disadvantages are reduced or avoided and where the materials used are used in the best possible way.

To solve this problem, the invention provides a method of the above mentioned genus, which consists in creating a positive form, this form with a first layer or layers of glass fibers impregnated with synthetic resin to clad, then with a covering of at least one layer of plastic foam to be provided on the glass fibers and at least one further layer of synthetic resin impregnated glass fibers wind on the foam to form a multilayered layer To create (sandwich) foam between two layers of fabric.

You can take the form off by splitting the sandwich in two is cut up to create two hulls from a mold by turning each of the Forms parts as a complete fuselage. On the other hand, by using the invention Procedure a single covered boat can be made. Another virtue of the present Invention consists in the fact that the process is carried out by workers with little technical knowledge and can be used over a longer production period.

According to a preferred method according to the invention, for example a hull for a small vehicle manufactured according to the possibilities, which the process and the material offer. In this example, the body and the Deck of a yacht viewed as a unit, with the upper and lower sections are designed so that they can absorb compressive and tensile loads caused by the jib and rear stay are exercised.

An example of a method of manufacture is as follows: One rotatable form is provided and the materials used for the sandwich coating are required, are assembled on a trolley that can be moved in the longitudinal direction.

The shape is a complete hull and deck unit that in diameter by the thickness of the finished sandwich coating is smaller than the finished fuselage. The mold is supported at both ends and is slowed down by a motor and gearbox rotated so that the materials are unwound from the trolley, applied and the Can be wound one after the other under tension on the core form. First will the mold is coated with a release agent such as PVA or wax. Polyester resin will attached and applied to the mold in a suitable thickness. Interwoven glass threads of the same thickness are applied to the moist plastic under tension. This is followed by a second layer of synthetic resin and a layer of glass fabric and so on continue up to the desired number of layers for the inner skin, then follows PVC foam of suitable strength, which under tension on the last quick-hardening wet coating is applied. Now a weak and wide fiberglass mat can be used be wrapped dry on the surface of the PVC foam to ensure that these are firmly pressed together and pressed into the surface of the inner skin will. This is followed by a layer of a fast-curing synthetic resin. the Coating with the outer skin begins as soon as it hits the PVC plastic surface Applied fast-curing synthetic resin provides sufficient protection against the effects of styrene has sealed. At this stage, any defects in the coating can through Application of fillers can be eliminated. The coatings work like the inner skin further up to the desired thickness. A final finish can be made by arrangement a floating scraper or wiper attached so that it achieves a smoothing and distributes excess resin when the mold is turned.

In this state it is according to one embodiment of the one described Method advantageous, a surface finish by bandaging with a metal strip for example off Melanex (registered trademark) of an aluminum foil of 0.025 mm thickness, or by using a suitable polyester-resistant Movie.

The final stage in the manufacture of the complete fuselage is made in removing the core form by having the hull cut in half and the whole shape is lifted out, and then the two halves together again get connected. This can be done in a satisfactory manner, for example, by that before the application of the mold release agent in the mold at the point of largest Ship width in the horizontal direction an insert is introduced around the Hull goes around to create a groove in the sandwich coating. By inserting a knife or a saw through the sandwich coating into the groove a smoother and more precise cut can be made around the torso to the top to separate from the lower part. The top is then removed, lifted and the Form taken out of the lower part. From the upper edge of the lower part of the body can Foam can be chiseled out sufficiently to a suitable depth. Synthetic resin is poured into this and a preformed tab is inserted into the groove. A similar groove is machined into the lower edge of the top of the fuselage. After the inserted tab has been coated with synthetic resin, the upper The body part is lowered onto the flap and excess plastic is removed.

At this point when the plastic coatings are still in the In the state of curing, there can be openings for the cockpit, hatches and windows can be cut out without the risk of deformation. An effective one At this stage, i.e. before the final hardening, connection can be made with both the inner as well as the outer skin of the hull, for inner bulkheads, keel battens, Ship floors and accessories can be achieved.

Changes in the coating process can occur, for example, when using of glass fibers running in a longitudinal direction in one direction by coating the Mold surface can be made by hand before applying the inner skin and correspondingly on the outer surface of the cured foam prior to application the outer skin.

Both sides of the PVC foam can be localized during coating be heated. Sheets made of PVC foam can be reinforced by inserting the Grooves are cut into foam from one or both outer sides in such a way that that only the middle area is compressed when bending.

The ratio of the thickness of the foam core to the GRP skin is for sandwich hulls about 6: 1 for a PVC foam core with a specific Weight of 80 kg / m3. Variations in skin thickness and the composition of the glass fibers Local stresses can be relieved in the skin layers. It you can also use pressure pieces or spacers instead of the PVC foam be used where, for example, screws pass through the core, which distribute the load on both skins. In these places it can be desirable be additional layers to distribute the forces over a larger area of the Apply skin than the pressure insert has.

Spacers or plates and electrical leads can be useful be introduced into the PVC foam core prior to application of the outer skin.

In this embodiment according to the invention, a sandwich construction wrd used, which simplifies the construction of boat hulls / FRP. Rotating the shape in Associated with the ability to apply the materials under tension to regulate, which are laid in arcs with changing radii of curvature, is essential Advantage of this system. This particular uses PVC foam which is effective with the outer GRP shells is connected.

Due to minor changes in the hull design and composition of the materials used in FRP constructions is made without affecting the Performance of the hull or mechanical and structural properties a loss of material avoided, a uniform production monitoring is ensured and in Compared to the previously usual method for a sandwich construction is much Saved work. The invention is applicable to both manual coating and mechanized coating Coating technology to improve production processes for the Core shape too create.

Further advantages of the method according to the invention are as follows: Air bubbles in the synthetic resin are made of each layer by the tension of the material pressed tightly to the surface around the shape.

The shrinkage of the synthetic resin during curing causes an enlarged Pre-tensioning the glass fibers around the mold and provides a reliable mechanical Secure connection between the foam and the glass fibers.

A chemical bond is established between the inner and the outer Layers of fiberglass formed along the abutting edges of the foam. This area of butt joints can be reinforced with strips of glass fiber during coating so that the GRP has an H-shaped cross-section.

A fast-curing synthetic resin can not only lead to faster Coating can be used, but also to reduce or reduce styrene formation to avoid. If polyester resin and a semi-rigid right plastic PVC foam are used, the PVC foam is locally softened and slowly hardened by the Resin braced.

The use of local heat to embrittle or stiffen the PVC foam strips makes the use of this type of foam for deforming inW MeFnmy more different curvature possible. Local heating at the coating point can also increase resin curing and coating speed. Synthetic resin can be used for both the inner skin and the outer skin, that is colored in one or more colors so that the inner and outer skin become one get colored finish.

The finished fuselage can be demoulded within fifteen minutes after the coating is finished it can be cut into two or more parts and it actually no more twisting occurs. Since there are no twists, you can the parts are stored independently so that they can be stored without the use of support wedges Harden. After curing, the parts can fail or fail without risk of escape not to be connected to one another to fit together. This would when using the usual GRP processes will not be possible.

The tension of the glass fibers during the coating along with allows precise control of the ratio of synthetic resin to fiberglass an improved strength-to-weight ratio characteristic than Standard FRP procedures can do this.

Although the invention is primarily related to construction of boat hulls has been described, this procedure is also applicable to pipes, Containers, wheelbarrows and other products applicable using fiberglass and plastic foam are used in the manner described.

If hollow products are to be produced, these can be built with parallel or mutually suitable walls and the shape can can be deducted directly after completion of production. An example of such a thing Article is a tube.

The mold can also be collapsed within the finished part and the molded parts can then be pulled out of the interior of the article will.

The above method of demolding is only an example. Belsbige other similar procedures are applicable.

Claims (9)

Claims 0 Method for manufacturing boat hulls or others hollow objects, characterized in that a positive shape is created and for the production of a multi-layer layer (sandwich) made of foam between two layers of fabric this form with a first layer or layers of impregnated with synthetic resin Lined with glass fibers, then with a covering of at least one layer of plastic foam provided on the glass fibers and at least one further layer of synthetic resin impregnated glass fibers are wound onto the foam. 2) Method according to claim 1, characterized in that the further Layer of fiberglass is coated with a polyester-resistant film. 3) Method according to claim 1 or 2, characterized in that the foam plastic is butted together in length or width. 4) Method according to one of claims 1 to 3, characterized in that that to form the impregnated fiber layer the mold with a mold release agent is provided, this coated with synthetic resin and on it a Layer of glass fibers is wound under tension. 5) Method according to one of claims 1 to 4, characterized in that that the shape is rotated. 6) Method according to one of claims 1 to 5, characterized in that that the shape is held in place and the plastic foam and fibers around the shape to be wrapped around. 7) Method according to one of claims 1 to 6, characterized in that that synthetic resin is applied to the first fiber layer or the first fiber layers is, wherein the foam is wound under pretension on the synthetic resin that the resin penetrates between the edges of the foam and the blunt abutting turns of the foam connects to one another. 8) Method according to one of claims 1 to 7, characterized in that that to form another impregnated fiberglass layer on the synthetic resin Applied to the outer surface of the foam and an outer layer or layers made of fiberglass is wound onto the synthetic resin. 9) Method according to one of claims 1 to 8, characterized in that that one or more of the synthetic resin-impregnated fiberglass layers contain a color pigment is added. lo) Method according to one of claims 1 to 9, characterized in that that the foam is heated before it is rolled up on the mold.