How to build a catamaran with your own hands from polystyrene

Articles

All photos from the article

For many owners of suburban areas located in close proximity to a natural or artificial reservoir, it makes sense to think about purchasing or independently building their own watercraft, which can be used for small water trips, fishing, or family summer holidays on the water.

As such a watercraft for small enclosed bodies of water, in most cases all kinds of plastic, inflatable, wooden or metal boats are used, but a catamaran is best suited for these purposes, which has higher stability, good unsinkability, and with an equal weight can accommodate more people .

Homemade catamaran with a hull made of waterproof plywood.

Why a catamaran?

There are a lot of options for watercraft, as well as their purposes. For those who live near bodies of water, and especially for those for whom overcoming a water obstacle is a vital necessity, a catamaran is ideal. This type of vessel has many advantages over kayaks, boats or yachts.

To make catamarans from plastic pipes, a minimum amount of material is required. In addition, remnants from the recent installation of a sewer or water supply system may well be used;
the catamaran is light in weight, so it does not cause problems in terms of transportation;
due to the design features - two cylinders connected by a deck, such a craft has high seaworthiness, strength, reliability and sufficient speed;
the ability to accommodate the required number of seats;
Any type of engine can be installed on a catamaran.

What does a catamaran consist of?

The catamaran has a large number of design features compared to other watercraft.

The catamaran is based on large diameter plastic pipes

That is why you need to know its components in detail before starting drawings and installation work.

The first, and most important, part of the catamaran is the floats. These are two chamber structures located on the sides of the craft. Their immediate task is to keep the ship afloat. Cylinders can be made of different materials that limit the outer perimeter of the float. To do this, use the film from which inflatable cylinders, foam plastic or PVC pipes are made.
Connecting frame. It can be made of any materials, from the same plastic pipes to wood or metal. The lighter the catamaran frame, the smaller the floats can be.
Deck. This part is created to accommodate passengers, luggage and other things that will be transported by water.
Steering wheel. The function of the rudder of any watercraft is performed by an underwater blade, which for movement is directly installed parallel to the movement, and for turning it is bent in one direction or another using a rotary handle brought to the deck.
Oars, pedals, motor or any other device that propels the catamaran.

Vessel size calculation

The diameter of the floats, as well as the width and length of the vessel, depend primarily on where and how it will be used. The larger the crew expected and the more cargo will be transported, the larger the size of the craft and the diameter of the floats should be.

The carrying capacity of a vessel can be increased by increasing the cross-section of the cylinders or their length. The decisive factor in this situation is the volume of air inside the cylinders.

The optimal parameters for calculating floats, based on the crew and carrying capacity, are as follows:

a single-seat catamaran should have a length of 2-3 meters with a cylinder cross-section of 0.3-0.4 meters;
for the manufacture of a two-seater vessel, cylinders with a length of 3.5-4 meters and a diameter of 0.45-0.5 meters are used;
three and four-seater watercraft have a length of up to 6 meters with a float diameter of 0.5-0.6 meters.

It is not recommended to make a catamaran longer than 6 meters, since it will almost completely lose its maneuverability. Although, if you are going to sail mainly in a straight line, there are no restrictions on the size of such a “ship”.

The larger the size of the vessel, the greater its maneuverability and stability, but the less maneuverability. This applies to both its length and width.

The width of a catamaran is primarily determined by its purpose and method of propulsion. If you are making a catamaran for river rafting using the kayak principle, its width should not exceed 1.2 meters. Otherwise, capturing water with oars becomes impossible. If it is planned to board rowers on cylinders, the width of the vessel can be increased to 2 meters.

If the catamaran is a fishing or pleasure boat and it is planned to be equipped with a sail, motor or blades with pedals, its width can be increased further.

Catamaran with oars

The width of the catamaran should be at least one and a half times less than its length.

Manufacturing procedure

To make a catamaran with your own hands, you need to decide on its purpose and, based on this, calculate the dimensions. We will consider two options for the vessel: the simplest single-seater and a tourist raft based on a catamaran.

Single catamaran

We start making the simplest single-seat catamaran by making floats. We take two pipes of the same diameter and length (based on the calculations given above, we will need plastic pipes for external sewage with a diameter of 0.4 meters and a length of 2 meters). We attach plastic plugs to one side of both pipes. This will be the back of the catamaran.

The front part needs to be raised for greater cross-country ability and maneuverability. To do this, we use two plastic elbows with a 120 degree bend. We attach them to the other end of the pipes and also close them with plugs.

When assembling cylinders, pay special attention to the tightness of the joints. The slightest depressurization can lead to the sinking of a ship on the water.

The floats are ready. You can start assembling.

Making a seat for a single-seater catamaran

To connect the floats into one “whole” catamaran, you can use anything. Small-diameter plastic pipes, wooden blocks, metal corners, etc. are suitable.

From the material you choose, we make crossbars 1.2 meters wide.
We install the cylinders strictly parallel to each other so that the bends point up and in the same direction.
We fix the transverse strips on top of the cylinders. For fastening, both clamps and self-tapping screws can be used, with which the transverse strips can be screwed to the floats for greater strength.
We install any comfortable seat on the cross beams, take the oars in our hands and row where we want.

Do-it-yourself single-seat catamaran made of plastic pipes (video)

Tourist raft

The basic principles of making these two watercraft with your own hands are not particularly different. The only difference is that the pleasure raft will obviously not be designed for one person. And it’s even better if it can also accommodate cargo in the form of provisions, a sun umbrella, clothes, dishes, and other things.

We make floats using the above method. But you should take a pipe with a diameter of 500-600 mm and a length of 6 meters. This will make it possible to create a stable and passable vessel on which you can take a nap without worrying about the life of the crew.
We make a strong frame measuring 6*2 meters. Since the frame must not only hold the cylinders in the correct position, but also serve as a platform for the deck, it is better to make it from metal corners.
Clamps are tightened onto the pipes from which the floats are made, to which, in turn, the frame is attached using bolts.
Flooring is made from boards on the frame.

This is what a tourist raft might look like
. This design allows you to install any driving device on a catamaran, from blades driven by pedals to gasoline engines.

In addition, such a platform allows you to fully sunbathe in the sun, catch fish, and, in general, have a fun and fruitful relaxation in a narrow circle of best friends.

Structural elements

So, when understanding the question of how to make a catamaran, it is worth considering everything in order. The raft's pontoons are made of slats and plywood. It’s worth starting with the frames. To do this, you need to cut 12 blanks from plywood, the dimensions of which are 320 * 320 millimeters, knock them down with three or four nails, and then process everything together along the contour. Next you need to make slots for the slats. The slats are square, but the slots should be 20-25 millimeters in size. The remaining 5 millimeters in the slats are equipped with grooves. It is best to lay all six slats side by side, secure them, and then use a saw to make cuts in all of them at the same time. Since they will turn out to be a little deeper at the edges, it is worth leveling the average depth by shifting the boards several times during the work process.

Before forming grooves, it is worth checking the dimensions of the plywood sheets. If we are talking about a number less than 1500 millimeters, then it is necessary to adjust the installation location of the cross member 7 and frame 5 accordingly. Six frames require pieces of slats to be attached to them from the sides and top, and a piece of board should be attached to the bottom. Everything must be done as firmly as possible; it is better to use screws or screws for this, because nails will be driven into the slats, the task of which will be to hold the plywood.

About catamarans

A special type of polyethylene is used to make the body of modern pedal boats. Moving parts are made of stainless alloys. Thanks to the water flow, this vehicle is easy to transport and store.

In addition to catamarans, models for personal use are also available, so purchasing a pedal catamaran is not difficult if you have available funds. The choice of models offered will satisfy the wishes of customers. You can find models from single-seat children's to impressively sized water catamarans that can easily transport 4 well-fed adults. But this is not the limit, because there are structures that are designed for group walks.

Vessel assembly

If you decide to make a catamaran with your own hands, you will need to prepare several slats. The length of four of them should be three meters each, two should be 1.9 meters each, you will also need four segments of 570-600 millimeters each, after which you can begin further work. It is clear that it is worth placing a pair of upper slats below, which will allow the frames to sit firmly in their place. You can immediately fasten a couple of cross members with screws, and then lay the keel rail, screwing it to frames 1, 5 and 6. Next, you can turn the catamaran frame on its side to secure the upper rails to the same frames.

You will need a board 50 millimeters thick to cut out the stern and bow bosses, and here it is important to take into account that their shape should be cone-shaped. And then they need to be inserted into place, having first tied the top slats with wire

On the bow and stern overhangs, the keel rail is made from several scraps.

Float manufacturing options

From wide boards 40 millimeters thick and about 3 meters long, support skis are made - floats, at one end of which cuts are made at an angle of 45 degrees. To increase the buoyancy of skis, dense foam is used, which is glued with waterproof or epoxy glue to their lower surface. After it dries, all edges of the workpieces are carefully processed with sandpaper or a file, and then covered with several layers of bright nitro enamel.

Inflatable floats are made, the material for which will be rubberized fabric. The creation process is quite labor-intensive, but the weight of the entire catamaran will be significantly reduced due to this.

The advantage of the first method of manufacturing floats over the second is that it is much easier to adapt a chair, as well as a drive mechanism, to a wooden structure.

The driving force in such a catamaran will be ordinary pedals from a simple bicycle. To install them, holes are cut in the bridge. To put such a technique into action, it is necessary to make a paddle wheel and blades, due to the rotation of which it will be possible to increase speed. They are usually made of stainless metal and welded to the rear hub. To control the catamaran, you also need to install a steering wheel, which will allow you to turn the device in different directions.

How to build a catamaran with a motor with your own hands

Only a good craftsman can construct such a craft on his own. But sometimes a do-it-yourself catamaran becomes better than the factory version; the owner has the opportunity to adjust the parameters and characteristics of the vessel to his needs.

First, the future model is designed: its detailed drawings are created, after which the general drawing is divided into separate drawings of all parts of the vessel. Then a frame is made (usually from duralumin). The next stage is the production of air cylinders from durable PVC of specified dimensions (length 3.5-4 m). The cylinders are equipped with valves for air injection.

In a homemade version, you can install tension balls. The assembly of the structure is completed by installing the stringers and deck. An important stage of design is checking all parts of the craft for reliability

Particular attention should be paid to the tightness of air cylinders. A high-quality homemade catamaran is always the pride of the owner

Inflatable catamarans

When moving, the inflatable catamaran comes into contact with the water only with its cylinders; the deck and frame remain above its surface. This reduces water resistance and increases speed. Now for these structures, high-pressure cylinder chambers (250-300 mbar) are used, in the manufacture of which reinforced PVC materials are used.

The use of single-layer cylinders made of durable materials reduces the weight of the craft and increases their rigidity. Inflatable catamaran models expand the capabilities of fishermen; with their help, users of a collapsible vessel get into the most inaccessible places of the reservoir, delivering the craft to the shore using personal vehicles.

Some tips on how to make a homemade catamaran

For short walks or trips on the water, a catamaran has a number of advantages over a boat or kayak. This means ease of disembarking and landing, reliability, greater stability and maneuverability, as well as increased cross-country ability in various rapids areas.

This means of transportation on water also has disadvantages, for example, increased windage of the hull and low speed when moving with oars. But these disadvantages are compensated by the advantages of the catamaran.

There are many designs of catamarans, the manufacture of which uses available materials. With the help of a detailed description and drawings, anyone can assemble the model they need with their own hands and at almost no cost.

The catamaran is a vessel that is easy to operate and manufacture, versatile in use and viable in extreme situations. According to the type of movement, these vessels can be rowing, sailing and motor, as well as mixed designs. These devices consist of a frame and floats. The frame is made of a number of longitudinal elements, and the floats are made of an airtight internal cylinder. Next we will tell you how to make a catamaran with your own hands.

Why not buy it?

For lovers of active recreation on the water, who have a great desire to have such equipment, but do not have the opportunity to design it themselves or buy it in a store due to high prices, the option of purchasing it through various media may well be suitable. A used introductory bicycle, if, of course, it is sufficiently reliable and suitable for use, it may well please the owner for a long time and give him a lot of pleasure. After all, someone may sell a bicycle not at all because it has fallen into disrepair and the owner decided to get rid of it quickly. It is quite possible that the former owner, for a completely different reason, not related to the technical category, decided to take this step. Of course, when purchasing such a watercraft, you need to carefully, or better yet, in the presence of a person who is familiar with this type of equipment first-hand, examine all the components of the pedal boat, and then make a final decision.

Second option

MODERNIZATION OF A CATAMARAN

Otherwise, we are completely satisfied with the catamaran, as far as this is in principle possible with this type of vessel, i.e. with inflatable and collapsible.

The use of stainless fasteners, as experience has shown, does not make much sense, with the exception of some of the smallest details. Galvanized steel fasteners do not rust much. Replacing it is cheaper than buying stainless steel. Well, the advantage of galvanized fasteners is also that it does not cause electrochemical corrosion of the aluminum alloy. The same can be said about cables.

It also doesn’t make sense to spend a lot of money on yacht components, since in other stores you can find cheaper analogues that are almost as good as branded components in terms of functionality. For example, a yacht double-pulley block can cost 5,000 rubles in a yacht store, but similar products can be bought in a tourist climbing equipment store for 300 rubles. The climbing block will be made of the same steel, with the same bearings, except without a stopper.

Types of catamarans

Types of catamarans differ in the technical solution of the parts of the vessel:

deck arrangements;
installation of transverse beams for floor rigidity (beams);
supports of different heights.

With flexible and rigid locker

The description of catamarans contains information about materials for deck construction. The locker of a catamaran can be flexible or rigid. Models with a flexible locker are easier to stack during assembly and transportation, while rigid structures are more reliable and convenient to use, but take up a lot of space during transportation.

The tension deck is made of PVC fabric, lined around the perimeter with slings with loops for fastening to the frame. The boom of these catamarans is of medium thickness, the air valve is near the stringer, and the fasteners are cross-shaped. Flexible types use polyvinyl chloride (PVC) material with a high density of 800 g/sq.m. Large cylinders can be installed on these models.

Models for two and three beams

Catamaran models for fishing have two or three beams that serve to strengthen the structure. The higher the protection of the frame, the greater the passenger capacity and other technical characteristics.

Models with two beams - for two passengers. The supports are installed at a low height. Load capacity - up to 300 kg, vessel length - up to 3.4 m, stringer diameter - 1.3 mm, cylinders - rubber patches, fastening - in the form of crosses. Can be equipped with flexible lockers. These designs are in demand among fishermen.

Catamarans with three beams are four-seater. Load capacity - up to 500 kg, air valves - near the stringer. The lockers are hard, sometimes the boom is made of rubber. Vessel options with two legs are popular. These flotation devices are made of high-density materials.

With low and high support

Supports of different heights affect the installation of motors of different power. Small models have low technical parameters, large vessels with powerful engines have higher quality characteristics.

Models with low supports are designed for installing low-power motors. Their carrying capacity is 300 kg, the air cylinders have a small diameter. It is possible to use rubber booms and ballers. The stringers are attached to PVC pads.

To use powerful motors, catamarans with high legs are produced. These models feature a rigid aluminum frame, large-diameter cylinders (density 800 g/sq.m.), and 1.4 mm thick stringers. The supports are additionally secured with braces. The length of such a catamaran reaches 4 meters.

Cylinder design

Floats are the most important part of the vessel. Stability, load capacity, and driving performance depend on them. There are 2 main types of cylinders - single-layer and double-layer.

As the names suggest, we are talking about the number of layers of material that form each float - a sealed container without an internal cylinder or a two-layer structure, where the upper power shell protects the inflatable chamber.

Both types have pros and cons, and, unfortunately, are surrounded by a number of myths inspired by manufacturers.

Single layer cylinders

Lighter, more compact, quick to assemble. Made from high-quality boat PVC material, they are no less reliable than a two-layer float. Gluing during production strengthens the joints, and in the event of forced repairs, the special patch copes with its task with a bang. It is easier to repair a mono structure in the field.

Mono cylinders are also divided into internal sections, and damage to one of them will not sink the ship. German fabrics VALMEX Boat Mainstream 1000 g/m2 and Powerstream 1200 g/m2, HEYTex Boat H5559 1200 g/m2 are considered good characteristics for single-layer nacelles.

Valmex 1200 grams

There is only one drawback of the single-layer model - the correct material for its manufacture is more expensive than for two-layer floats; this is not cost-effective for on-line production.

Double layer

The sealed inflatable layer is located inside the power shell. Such floats are heavier in dry weight, and after rafting, the weight of water in the internal interlayer space is added. They are much more difficult to dry and assemble correctly - assembly can take several hours. They take up more storage space. They are no less afraid of holes than mono.

The inner container is made of lightweight material of medium strength. It partly follows the shape of the main balloon to avoid unnecessary folds, but is longer than it. Thanks to this, the chamber is not inflated with air all the way, and the lack of pressure reduces the load on the seams. The best fabrics: Finnish Viniplan 6331 boat 550 g/m2, VALMEX Boat Life raft 7326 500 g/m2.

Repair kit MEHLER PLASTEL® boat TE 70

For repairs, PVC PLASTEL boat TE 90 and TE 70 has proven itself well: they adhere well, the tensile strength of the strip is 5 cm 2800/2800N. It’s more difficult with glue; in production they use two-component ones. One of the compromise options is the French BOSTIK.

Gondola shape

The gondolas of the first catamarans had a simple cigar-shaped shape. Sewing them is not difficult, and if you want to increase the volume, you can make changes to the pattern without complex calculations.

It is convenient to attach a deck and accessories for a motor or sail to a vessel with such cylinders, so “sausage” catamarans are the best choice from the point of view of tourists who are not looking for extreme sports.

Camel Big Fox from Raftmaster

Sports double models are sewn in the camel style. They received this name because of the “humps” on the stern and bow. At the same time, the middle part, where the rowers and luggage are located, turns out to be lower. The vessel's center of gravity also shifts down, making it more stable and controllable. In addition, the humps partially protect athletes from impacts from oncoming shafts.

Number of sections

The internal container is often equipped with partitions that divide it into several independent sections. This increases the weight of the catamaran and during assembly you will have to inflate each section separately. But, even if the ship gets a hole, there will still be a fair amount of air left in the cylinder, and the rowers will have time to moor the ship to the shore on their own.

Volume

An important characteristic on which the vessel’s carrying capacity and its ability to overcome obstacles depend. The huge float can easily pass moderately difficult barrels, and with competent work of the crew, dangerous foam boilers. It is not capsized by rigid shafts; in short, in any such situations such a catamaran is highly stable.

Maximum load for Urex Tourist-1: 350 kg, for Bereg K6: 1700 kg.

The larger the volume of the cylinders, the lower the vessel’s ability to maneuver, so on slalom sections the tonnage boat will feel insecure.

Additional features

Openings for inflatable containers can have different designs. For example, a self-closing valve (models from Raftmaster), a zipper (Baseg), piano hinges (Svarog).
Longitudinal fastenings Some vessels have a lace-up , for which purpose there are special ridges with eyelets on the sides of the cylinders through which a rope is passed. This fastening has a drawback - the rope can easily be broken, for example, by hitting a stone. Because of this, many manufacturers offer another method: a corridor along the cylinder . However, the option is often suitable only for the “original” frame, so replacing a damaged pipe, for example, with a wooden picket will be problematic. For this purpose, manufacturers sometimes combine both fastenings: corridor and ridges .
Pockets, handles . For the convenience of catamaran operators, the cylinders may have separate pockets for a lifeline, a pump or a repair kit, as well as special handles that can be used to lift the boat or grab onto it while in the water.
Individual tailoring . Manufacturers offer ready-made production models, but many, at the request of the customer, are ready to make changes to existing designs. So, if there are no internal partitions in the inflatable container, you can ask them to be glued in, or choose a more dense material for the bottom. Some people want to increase the flow, glue the seams, add handles. Such improvements will allow you to get a watercraft “for yourself.”

Advantages of using a catamaran for fishing

A popular means of fishing is motorized fishing catamarans. It allows you to expand the range of fishing spots, you can choose the best sites for biting. Assembling and disassembling the catamaran can be done by one person: its parts are assembled within half an hour, which makes the device mobile and convenient.

The deck is half a meter higher than the water surface, which saves fishermen from the waves, and rainfall does not accumulate inside the frame. There is no need to bail out the water; it drains into the gaps of the deck, making the catamaran easy to wash. From below, inflatable catamarans are protected by a beam from rubbing against the surface of the bottom or shore of a reservoir.

The main advantages of a catamaran-type vessel are:

high frame stability;
spacious and high deck;
high load capacity;
durable bottom;
large air compartments;
easy assembly and disassembly;
easy care and cleaning from dirt;
safety of use.

Inflatable catamaran

You can swim on it in pairs and there is even room for luggage.

If you wish, you can easily install a small sail here, which brings little benefit, but still worth a try.

The floats are glued from pharmaceutical durable oilcloth, the surface of which is covered with rubber glue and carefully powdered with silver powder.

Fabric covers help preserve the floats and protect them from sunlight. For the manufacture of the frame frame and seat bases, aluminum pipes with a diameter of twenty and twenty-five centimeters are used. The oars can be used for kayaking.

What is a catamaran?

If you look at the photo of a fishing catamaran, it is easy to see that there is a lot in common between it and an inflatable boat. An inflatable boat is a single unit, even if it is divided into compartments and each of them is inflated separately.

The catamaran has two separate floats between which there is a deck. The catamaran's area is much larger due to its width and there is enough useful space even for setting up a small tent or canopy.

In terms of its seaworthiness, a catamaran is much more stable and does not flood with water like a boat. The deck is usually located quite high from the water and the wave does not reach it.

Introduction to technology

What is a pedal boat? To put it simply, this is an ordinary catamaran, which we have seen more than once on the piers of boat stations and, of course, rode on the surface of the water, enjoying and admiring the beautiful scenery, while simultaneously receiving a boost of energy from training the muscles of our body.

Typically, such equipment is small in size and weight, making it easy to transport in a car. Of course, a big advantage is that this type of transport does not need to be registered, there are no age restrictions for it. Fishing enthusiasts will probably also appreciate such a pedal boat; for them it will be a convenient purchase, since the watercraft will not capsize when the wind blows. Unlike a boat, you can fish while standing in it.

Guide to building a catamaran

Before you start building a catamaran, it’s worth understanding some of the nuances.

Firstly, before you start building a pedal boat with your own hands, you need to decide on the basic design, namely, what the body will be made of.

Secondly, what the design will be like depends on the purpose for which construction is planned.

Thirdly, now on the Internet you can find a lot of examples of real projects that are easy to implement even under minimal conditions (materials, premises, tools).

Below we offer several options for the construction of this watercraft.

Homemade catamaran

Reliable foam catamaran

A catamaran made of foam plastic boasts a lot of advantages: durability, unsinkability, ease of operation. To make a watercraft, you will need the following parts, which are made from plywood with a thickness of 12 mm:

Two diaphragms in the nose.
Four partitions.
Four frames.

To secure the parts, tie pipes made of duralumin are used (thin-walled steel pipes are also suitable). The pipes must be threaded, the size of which should be approximately 12 mm.

Before assembling the floats of the craft, epoxy glue is placed on the wide parts of the plates, and then they are combined using steel tubes using ties. Next, the future watercraft is covered with calico or fiberglass folded in several layers. It is better to do this using epoxy resin.

The front side of the floats is also made by hand using corners, and then sheathed with aluminum sheets.

The covers, consisting of sheet duralumin plywood, are attached to the corners of the bow with screws, and the bow itself sits on the ends of the coupling pipes and is tightened with nuts. The final stage is to fill the bow of the craft with foam, after which the lid is closed.

The deck is built using slats and wooden blocks. Next, the mechanism is attached to the frames with bolts and nuts.

foam boat

DIY inflatable catamaran

Most often, floats have a two-layer design: a chamber on the inside and a protective shell on the outside. To make an inflatable catamaran, you can use internal chambers with two compartments.

The installation of an inflatable chamber into a vehicle on water is carried out into the skin of the float through the holes that are located at the ends of the skin. All actions must be carried out as follows:

The camera is placed next to the hole.
The skin is put on the hand through another hole.
The camera is pulled into the skin.
The ends are bent approximately 10 cm.

An inflatable craft with primitive hatches does not have a fastener, since at the moment of inflation, the chambers close themselves. As the two chambers are inserted into the skin, they are layered on top of each other. Next, two skins are drawn in simultaneously.

The tube that inflates the chambers comes from the skin through one of the hatches. As for the pressure in the chambers, it is generally no more than 0.1 atm.

Inflatable catamaran

Homemade catamaran

Many people ask questions: “How? Of what? With what tools? According to what drawings? You can make your own catamaran. There is a lot of information on this topic on the Internet; of course, many methods, ideas, estimates and diagrams will be presented to your attention. Theoretical knowledge will definitely be needed, but it is better to see the whole process with your own eyes and choose the catamaran model that is right for you, and be patient when implementing your plans. This article presents several options for building a catamaran.

Well, isn't it great?

It's hard to resist a purchase like a pedal boat, which weighs only 14 kilograms and, in addition to this, can also be disassembled. By putting it in a bag for a while (disassembled), you can travel with it everywhere and test it on any body of water. The maximum weight that the design of such an aquaskiper can withstand is 110 kilograms, the minimum is 35. Therefore, for safety reasons, teenagers under 11-13 years old should not ride it.

These age limit guidelines are provided for hydrofoil bike buyers. For those who decide to purchase a catamaran-bicycle for walking around the water area, such restrictions do not exist. In this case, everything depends on the adult: if he allows his child to see him, it means he trusts and does not doubt his strength and endurance. But attentiveness and control over children and adolescents are always necessary and never hurt. Be careful on the water!

Is it possible?

Is it possible to construct such a pedal boat with your own hands? Yes, easily! If only you had skillful hands and a head, a good master will definitely have everything else. Let's take a closer look at this unusual type of transport. A man sitting on an aeroplane resembles a rider, bouncing up and down, as if galloping along a very rough road. At the same time, with the help of the steering wheel, it can turn in any direction, and, most importantly, all this will happen not on the ground, but on the surface of the water. When creating such a bicycle, close attention must be paid to the reliability of the leg mounts; it is also necessary to make the correct calculations for the hydrofoils in order to ultimately ensure complete safety for the “rider”.

Looking from the side at such a jumping person is funny and cheerful, and it seems that it is easy and simple to do. In fact, to glide smoothly and confidently through the water, a lot of effort and skill is required, because it’s not for nothing that such a bicycle is considered a sports trainer.

Sailing Catamaran

The floats of this vessel have a certain chamber structure, that is, an outer shell, which provides strength and an internal chamber, which is responsible for tightness.
This function simplifies the production of this model and increases its reliability. The contours on the floats help achieve low water resistance when moving. The frame is constructed of duralumin tubes with bolted fastenings using shaped nuts. The catamaran is equipped with a steering wheel to facilitate control and relaxation. Also, such a design provides for the presence of sailing weapons. Almost all components are made independently; only a small amount of turning work is required.

Floats

There are two of them and each has the appearance of an air-filled hollow and round structure in cross section. The floats have practically no cylindrical sections and differ in bow and stern sections. The large ratio of surface to underwater volumes in the stern and bow parts of the floats contributes to excellent surfability on waves.

The float consists of an inner chamber and an outer shell, which is fifteen percent smaller than the chamber. This factor is necessary, as it contributes to the tense state of the camera and ensures its safety. Making cameras is a major operation and takes a lot of time. A part made of synthetic materials is considered the most durable, while a part made of rubberized materials is considered the cheapest.

Uncover

If the chamber cannot be cut out from a single piece of material, then the panel must be glued from the pieces overlapping. The seam width must be at least three centimeters and additional fabric strips must be glued in their place. During assembly, the back of the chamber, which looks like a sleeve, is twisted and tied with a rubber band.

The bottom is also cut out from a single piece of fabric or from separate panels. Next, the lower and upper shell parts are stitched from the limbs to the middle. These parts should be cut very carefully, to the nearest millimeter, to ensure the correct shape and avoid wrinkles on the float.

Bridge

This part is made from a set of aluminum tubes of various diameters, fastened with studs and bolts. All stringers consist of two components connected by a sleeve, which is attached with glue to the stern part and secured with a pin. The ends of the stringers are secured with plugs made of any materials and secured with shaped nuts.

Deck

This part has the appearance of a rectangular panel made of a dense type of nylon. Its dimensions depend on the assembled frame. Along the perimeter it is necessary to tuck the edges of the panel thirty millimeters and stitch it. Then you should install the grommets designed to secure the bridge and deck. Lacing must be done from the middle of the float to the limb.

Steering wheel

This part of the catamaran has the form of a feather made of fiberglass sheet two millimeters thick, which later bifurcates and folds together. Both halves need to be attached to the back and front edge using holes and copper wire and screws. Then all the edges in turn must be filled with epoxy resin and coated with plasticine.

The steering wheel should be hung on the bracket using homemade hinges.

Oars

To make oars, you need duralumin pipes, to which a roll, flattened by heating, is attached with four bolts or rivets.

Sailing weapons

This auxiliary weapon is ineffective and therefore rarely used, but is provided on this type of catamaran.

Seats

The number of seats is ideally equal to the number of rowers and a multiple of two, since the crew is distributed equally across both cylinders. But options are also possible: on the “Latvian” two-piece, the seats are located between the gondolas.

With mattress rafting, it is permissible to place passengers on backpacks. On difficult routes, the rower's seat must ensure safety and comfort, so the seats are pre-sewn to the outer skin or rigidly fixed in place.

Legs numbness in the knee position is an unsolved problem of rafting on catamarans. In stretch areas you will be able to rest by straightening your legs, but even getting off the kata onto the shore can sometimes be difficult.

The concept of convenience is individual for each catamaran operator, but only one thing is certain - the seat should be high enough to reduce the load on the knees.

On sports catamarans there are two types of seats : “machine guns” and the more familiar inflatable ones:

“Machine guns” received such an unexpected name because of the support, reminiscent of a machine gun bipod. The design is quite convenient, it will not deflate at the wrong moment, but it is not widely used and is perceived as exotic.
Inflatable seats, or cans , are more popular. They are easier to assemble, convenient and have only one drawback - if the plug accidentally falls out, the seat will deflate. However, this rarely happens, and in all other respects the device showed its best side.

Knee supports are an essential part of the seats; they hold the rower in place, preventing him from falling out and allowing him to operate the oar without difficulty. With the free end they are attached to the lengths and are adjusted depending on the needs and dimensions of a particular person.

Belraft catamarans even have two straps on each side, but only people with above average height can truly appreciate such convenience.

Fixing straps can hold the leg in different places: for some it is more convenient for them to be located as close to the body as possible, but there are also those who prefer support on the middle of the thigh. Such moments are individual and each athlete adjusts the straps to suit himself, fortunately catamaran manufacturers provide this opportunity.

An additional detail on the stops is a self-release buckle, like the Raftmaster models. It is needed to free yourself during a rollover if protection or other elements of equipment get caught in the belts.

Catamaran "Surf"

Catamaran “Surf” (pedal-driven pedal boat), designed for recreation and boat trips along inland waters and coastal areas of the seas.

The drive and steering of the catamaran are made of stainless and galvanized steel. The shells of the floats and the seats of the catamaran (pedal boat) are made of fiberglass.
The floats of the catamaran (pedal boat) are filled with foam, which ensures 100% unsinkability.
The protective and decorative coating of a fiberglass pedal boat (fiberglass catamaran) provides not only ultraviolet resistance and surface smoothness, but also provides ample opportunities when choosing the color scheme of the product.

Surf - main parameters and dimensions:

Catamaran length – 3.75 m;
The width of the catamaran is 1.95 m;
The height of the catamaran is 1.1 m;
Catamaran weight – 95-100 kg;
The carrying capacity of the catamaran is up to 200 kg;
Passenger capacity – 2 people and a child under 12 years old.

Main advantages:

easy movement and controllability
of the catamaran (pedal boat), which allows even a child to control it;
the high position of the seats and the presence of mudguards
make it possible to take walks on the catamaran in clothes;
good stability on the water
makes it possible to move along floats, dive from them into the water and get out of the water;
excellent maneuverability of the catamaran
(pedal boat) “Surf” (turning radius – 3 meters);
Possibility of equipping with a removable sun awning, luggage bag for passengers' belongings (volume - 40 liters), cup holders for drinks.

The use of fiberglass as the main material in the design of the Priboy catamaran allows us to achieve:

long service life of a fiberglass catamaran (fiberglass pedal boat);
high resistance to temperature changes;
resistance to aggressive environments and ultraviolet radiation;
high physical, mechanical and operational properties;
ease of care and maintenance.

https://veles-sib.ru/sport.katamaran-priboy
https://the-mostly.ru/misc/water_bike
https://www.viza-yacht.ru/product/vodnye_velosipedy_katamarany/

Third option

A homemade foam catamaran is unsinkable, easy to use, durable and easy to manufacture.

Its dimensions are: 3750 x 1600 mm, plate thickness from 40 to 150 mm, float height 200 mm and width 400 mm. The weight of 1 m3 of foam is about 20 kg.

The plates are cut on a special device using nichrome wire heated to 200-250°C, or on a special machine. The bow diaphragm (2 pcs.), bulkheads (4 pcs.), frame (4 pcs.) are made of plywood 12 mm thick. The coupling pipes, which are used to fasten parts, are made of duralumin, but thin-walled steel is also acceptable; Duralumin rods with a diameter of 10-12 mm are also suitable for screeding. Threads on pipes with a diameter of 1/2 are cut with a ratchet or a die, and on rods - with a die with a basic metric thread (M10).

The bow part of the catamaran floats is made separately from aluminum corners 25 x 25 mm and sheathed with thin (0.5 mm) sheet aluminum. The metal structure has a plywood diaphragm, fastened with M5 bolts with corners; The aluminum cladding parts are connected with rivets. Covers made of plywood or sheet duralumin 1-1.5 mm thick are attached with screws to the corners of the bow. The bow part is placed on the ends of the pipes and secured with nuts, as shown in the figure. It is then filled with pieces of polystyrene foam and covered with a lid. The superstructure (deck) is assembled from wooden blocks and slats. The entire structure is attached to the frames with eight bolts and nuts. For movement on water, a boat motor with a power of 1-5 hp is installed in the stern. You can also swim on oars made from thin-walled duralumin pipes. It is also possible to install an oblique sail on a catamaran with an area of up to m/2.

How to make a pedal boat with your own hands?

The pedal boat is simple in design, reliable and lightweight. The basis for it is the frame of a children's bicycle.

1 – floats; 2 – frame; 3 – small square; 4 – large square; 5 – stretch marks; 6 – rudder blade; 7 – bearings; 8 – paddle wheel; 9 -shaft; 10 – rivet with a diameter of 5; 11 – bushing; 12 – rivet with a diameter of 5; 13 - star; 14 – strip measuring 0.5x25x200 mm; 15 – strip measuring 0.5x25x210 mm; 16 – bolt M8x30; 17 – M8 nut.

https://youtube.com/watch?v=qOo0l1ygHkk

Instructions for making a pedal boat

From four dry, smoothly planed pine boards with a cross-section of 20x120x2400 mm, cut out the “cheeks” of floats 1, as shown in the figure.
Connect them using casein glue and small nails with spacers, and place bosses on the ends. Cover the bottom of the floats, also on glue and nails, with a sheet of plywood 3 mm thick and 300x2500 mm in size.
Lubricate the inside of the grooves generously with glue and cover them with strips of fabric. When the glue has dried, putty the joints of the plywood with the “cheeks” and cover with oil paint.
After 1-2 days, as soon as the paint has dried well, strengthen the deck with glue and nails. Make it from a sheet of plywood 3 mm thick and 300x2400 mm in size.
From pine beams, as shown in the figure, make a frame 2 and use squares 3 and 4 to secure it on the floats. Using 5 braces, firmly connect the bicycle frame to the float frame.
Cut the rudder blade 6 from a sheet of millimeter steel, solder the axle to it and insert it into the front fork.
Then proceed to install the drive. To do this, put the paddle wheel 8 on the shaft 9 and mount it with the gear sprocket 13 using the bushing 11 and rivets 10 and 12.
Then install bearing 7 in place at the rear of the floats, at a distance determined by the length of the chain.
Having secured the bearings with marks 14 and 15 from metal strips (pieces of hoops) to the float frame, tighten the M8×30 bolts with M8 nuts (16, 17). After checking the correct assembly, rotate the drive pedals several times.
After this, having soaked all wooden surfaces with boiling drying oil, paint the bicycle with oil paints in the colors you like. From thin, smoothly planed and treated with fine sandpaper boards measuring 10x50x1340 mm, make a footrest on the left side. There is no need to paint it.

First option

What kind of sailing ship can be built at minimal cost, without having a special place for building and storing the ship, or high-quality materials? An ultra-small catamaran less than two and a half meters long was recognized as such a vessel. We were convinced that a catamaran of this size can be successfully sailed by a photograph in one of the issues of the French magazine “La Revue Marittirne”. The chosen length made it possible not only to build the buildings in the conditions of any city apartment, but also to transport them on an electric train, on a tram, and even more so on the roof of a car.

It was necessary to ensure other qualities of the catamaran: ease of assembly and armament, ease of operation and speed. A collapsible design with a removable bridge and sealed housings was developed.

The rig type is Bermuda cat.

Main parameters of a small catamaran:

To increase longitudinal stability, the hulls have fairly full ends. Rounded contours provide a minimum wetted surface, which, when one body comes out of the water, is reduced by another UZ. The material for covering the bodies was 3 mm thick cardboard, available in a wide selection in construction supply stores. Cardboard is quite durable and technologically convenient.

The casing is glued to the kit with casein glue and pressed in with screws. The bodies are covered on the outside with calico with epoxy glue and impregnated on the inside with a mixture of drying oil and turpentine. The longitudinal set of the hull consists of a keel, midships (carlengs), fenders and two stringers. The frames are cut from 12 mm thick plywood. At the ends, the spacing is reduced for ease of fastening of the sheathing.

The hulls were assembled without a slipway and checked by string. The bridge rests on the hulls at the ends of two box-shaped beams. The sub-mast beam has a cross-section of 64X80 mm and is designed to withstand bending from a mast pressure of 150 kg. Safety margin of plywood beam chords n=3.5. The bodies are equipped with ash cushions with wide hinges, in which the ends of the beams are fixed with four bolts. With this mounting, the bridge is raised above the hulls, which increases vertical ground clearance.

The hollow mast consists of two parts. The upper half fits over the lower half and is secured with a bolt. The junction is covered with a foam fairing. At the bottom, a pair of bamboo legs are attached to the mast; these legs replace the stays, take part of the load of the cables, and facilitate the installation of the mast.

The disassembled mast and boom are stored in the catamaran hull. For this purpose, a hatch is made in the transom of one of the hulls, which is secured with a lid with a rubber gasket. The centerboards and rudders are cut from D16 duralumin, 3 mm thick.

The halyard plate of the sail also serves to attach the foam float. The volume of the mast, fairing and float is sufficient to prevent the catamaran lying on board from completely capsizing. The stability of such a small vessel depends, first of all, on the efficiency of heeling. When the windward hull with the helmsman on it leaves the water, the righting moment is 100-120 kgm. The nominal wind for a catamaran should be 7-8 m/sec. In this case, the heeling moment will not exceed 90 kgm, and the design speed on the gulfwind course will be equal to 12 knots. The total resistance of the vessel is 16 kg.

Specifications

The catamaran consists of two air cylinders and a frame, which can be inflatable or rigid, made of aluminum. When assembled, the entire structure fits in a backpack, which is convenient for transportation.

Sustainability

The catamaran is a stable structure; it easily rides the wave, receiving a minimum of impacts. Spray formation is small at any speed, which is comfortable for passengers. With a wave height of 0.5 m, the stability of the structure is superior to other models. Catamarans are stable on course and easily maintain a given trajectory.

The watercraft is able to withstand the influence of external forces, its lateral stability resists the forces of the turning moment. Longitudinal stability resists piles on the stern or bow - a longitudinal turning moment (turning over the stern). The large distance between the cylinders and proper weight distribution increase the stability of the product.

The safety of a catamaran is greater than that of boat models. The stability of its structure is much higher. Boat overturns are possible when there is a load on board, which often happens when fishing for fish when the craft rolls. Using inflatable structures, even several people can be on the same board without the danger of it tilting or capsizing. This craft cannot be capsized or sunk.

Usable space

Catamarans are much wider than single-hull models, resulting in almost twice the usable space of boats. Decks with a width of 2 m can be from 2.5 to 4 m long; an awning or tent is installed on a large area.

Economical

Due to their design, catamaran models have reduced drag. Their weight is divided between the air hulls, creating little drag compared to boats. The speed of a catamaran is 20-40% higher than that of a boat with the same load.

Catamarans accelerate to 20-25 km/h when using smaller engines that consume little fuel. The fuel consumption of these models is one third lower than that of boats. Fishing models have a transom for a motor up to 10 hp, but they often use small engines from 2 to 5 hp.

Load capacity

A loaded craft can dive below the optimal depth, but overloading a catamaran will only worsen its speed characteristics: for it to sink, the cargo must be three times its carrying capacity. This means that with a carrying capacity of 500 kg, an overload of up to 1500 kg will be critical for this craft.

Catamarans have a carrying capacity of 300 to 500 kg; the load does not affect its stability and speed. Despite their light weight, the models have a large carrying capacity; they can accommodate boxes for transporting catch, fishing equipment and many other necessary loads. The number of passengers is from 2 to 10 people. Unsinkability under overload is a big advantage of the catamaran design compared to boat models.

MOTOR CATAMARANS

The topic of motor catamarans is so multifaceted that, when starting this material, I immediately limited the range of designs under consideration to only those that I knew from personal experience. We will only talk about vessels with rigid hulls, leaving aside what is probably the most numerous class of watercraft on inflatable floats. The main attention will be paid to collapsible models of compact size. They are easy to transport and suitable for making on your own.

For most DIY tourists, it is important that the dead weight of their watercraft with a motor does not exceed 200 kg. In this case, according to Russian laws, it does not require registration, and it is much easier to transport/store such a boat. At the same time, even with such a strict weight limit, I want to achieve maximum comfort, safety and seaworthiness. This opportunity is provided by multihull vessels and, in particular, catamarans.

CLASSICAL CONSTRUCTIONS

The peak of interest in catamarans occurred in the 60s of the last century.
Then they were a fashionable novelty, from which many miracles were expected, including an increase in speed by reducing wave resistance with the low-power engines then available. The talented shipbuilding engineer Vasily Andreevich Hartwig, the designer of the passenger glider-catamaran OSGA-25 "Express", which was ahead of its time by about 50 years, spoke then in the magazines "Boats and Yachts" (No. 1-1963) and "Science and Life" ( No. 10-1968) on projects of high-speed multi-hull floating dachas intended for self-construction. A similar development, or rather sketches, were published in the journal “Technology for Youth” (No. 7-1971). A common disadvantage of these designs was that powerful outboard motors did not exist for them at that time. Implemented project by V.A. Hartwig (see "KiYa" No. 43-1973) confirmed that the comfort and seaworthiness of the floating dacha-catamaran were indeed excellent, but its speed turned out to be significantly lower than expected. As a result, a fair conclusion was made: due to the high labor intensity of assembling a catamaran and lower speed indicators than a monohull vessel, the construction of such structures is justified only in cases where the deck area and, accordingly, comfort are important. Fast floating dacha-catamaran V.A. Hartwig (“KiYa” No. 1-1963). The project envisaged the installation of two Moskva outboard motors of 10 hp each, but to achieve the design speed it was necessary to use two Whirlwind motors of 20 hp each.

Drawing of a catamaran by G. Lipman with a very beautiful, but very heavy, automobile-type cabin, published in the magazine “Technology for Youth” (“T-M” No. 7-1971).
The contours of the floats are designed for planing and even have transverse steps, but motors capable of doing this did not exist in the USSR at that time. As far as is known, there were no attempts to implement this project. The magazine “Modelist-Constructor” did not remain aloof from the fashionable hobby of amateur shipbuilders. In No. 7 for 1969, a magnificent drawing of a single-seat planing catamaran (or “water moped”) designed by G. Stepanov, made by the famous designer Eduard Molchanov, was published in the color insert. You can see how the structure is transported on the roof of a car, which means that its weight does not exceed 100 kg. But the most interesting thing in that picture is the engine. This is a stationary motor with forced air cooling, reminiscent of the Japanese Honda.

“Water moped” in the drawing by E. Molchanov (“M-K” No. 7-1969). The idea is beautiful, but a stationary air-cooled engine is clearly “not ours”

Design of the “water moped” by G. Stepanov (“M-K” No. 8-1969). Planing floats with transverse steps have a stacked design

A modern home-made design of a lightweight, collapsible catamaran with assembled floats, involving the use of a low-power PLM (no more than 5 hp).
The contours of the floats are smooth, designed for displacement mode. They are spaced at the maximum possible distance, which not only increases stability, but also reduces wave resistance. However, in the next issue of the magazine a description of the “moped” project was given. Its floats had a traditional stacked construction of wooden slats with plywood sheathing and, of course, there was no Honda on it. For the planing version, a stationary engine from the Vyatka VP-150 scooter with a power of 5.5 hp, as well as outboard motors “Priboy” with a power of 5 hp were offered. or “Veterok” with a power of 8 hp. I’ll note right away that due to the hydrodynamics of the catamaran, it would only be possible to plan confidently with the “Veterok”.

Similar lightweight collapsible catamarans with stacked floats and plywood sheathing are still being built in our time. To ensure the durability of the cases, they are usually covered with fiberglass.

FOAM BOATS

In deck catamarans, the volume of floats is not used in any way. In the case of a stacked structure, only air is contained there. Therefore, it seems logical to make the floats monolithic, from a lightweight material such as polystyrene foam, polystyrene foam or polyethylene foam. Foam plastic is the most accessible for DIYers, but polystyrene foam is preferable because it does not absorb moisture.

One of the first examples of a lightweight foam plastic catamaran (expanded polystyrene was not commercially available at that time) designed by A. Kopylov was also published in the magazine “Modelist-Konstruktor” (see “M-K”, No. 9-1974). The floats are made of 50 mm thick foam plates, pulled together into a package with long pin rods. The resulting block is covered with fiberglass cloth and epoxy resin. The catamaran was designed to use an outboard motor with a power of up to 5 hp. A modern two-seater homemade catamaran, the floats of which are assembled using almost the same technology (the thickness of the plates made of construction foam polystyrene is 50 mm), is shown in the photo given in this review. The mass of each float with a cross-section of 400×300 mm and a length of 3400 mm is only 24 kg. The 16mm thick plywood deck is attached with eyebolts directly to the tie rods of the floats. Speed with 3.6 hp motor. and with a crew of two people was 15 -18 km/h. The author calls this planing, but when applied to a craft with a displacement of about 300 kg, this is not correct (I will talk about the features of planing catamarans below, using my own design as an example).

Light catamaran by A. Kopylov with floats assembled from foam plates (“M-K” No. 9-1974)

Homemade catamaran with floats made of polystyrene foam boards.
Vessel length 3400 mm, width 1450 mm, distance between floats 650 mm BUOYATION MODULES

It is better, of course, that the catamaran floats are monolithic. The main difficulty here will be to find suitable workpieces, and the technology for cutting polystyrene foam and expanded polystyrene has been mastered for a long time. Although in our time it is not at all necessary to make floats yourself. Relatively inexpensive so-called buoyancy modules (essentially the same floats) are available for sale, designed for floating berths and other low-speed watercraft. They are made, as a rule, by rotational molding from polyethylene, less often glued from fiberglass, and have attachment points to each other and to the upper deck. The inside of the housing is hollow, but can also be filled with some kind of foam material. The bow and sometimes the stern modules have some sharpening, so the design obtained using them will not be completely alien to the laws of hydrodynamics.

Using such systems from buoyancy modules, not only berths are built, but also quite large deck boats with outboard motors and even quite comfortable (at the same time inexpensive) self-propelled floating dachas. For example, the small deck boat-catamaran "Kairan", assembled on four floats, has a high carrying capacity (up to 680 kg). True, it itself weighs 440 kg, which makes its transportation and launching difficult.

Deck boat-catamaran "Kairan" on four buoyancy modules. Length 4000 mm, width 1800 mm, load capacity 680 kg, dead weight 440 kg, permissible motor power 10 hp.

Project of a collapsible deck boat-catamaran designed by G. Dyakonov on buoyancy modules of the PK-120 type

Transport position of the catamaran on the top trunk of a car.
I set myself the task of keeping the boat’s own weight within 200 kg. This is possible if you use smaller buoyancy modules. The floats are assembled from three polyethylene buoyancy modules of the PK-120 type. The bridge, measuring 2080×1800 mm, is made of bakelized FBS-1 plywood 5 mm thick, laid on a frame made of rectangular duralumin profiles. Easily removable “seats” from a UAZ car were used as seats. In the carrier vehicle they are used for their intended purpose, so they do not require space in luggage. The seats are mounted on perforated plastic vegetable boxes that act as luggage compartments. During transportation, empty boxes fit inside one another. The railing is assembled from thin-walled pipes and attachment points of the “Joker” system, which is usually used for quick-dismounting warehouse shelves, sales counters, exhibition stands, etc.

In terms of the weight of the structure, the breakdown is as follows: float system - 2 x 40 kg; bridge - 28 kg; bow seats -2 x 5.3 kg; aft seats - 2 x 6.6 kg; luggage boxes - 4 x 1.6 kg; railing - 7.4 kg; outboard motor 5 hp - no more than 20 kg. Thus, the total weight of the catamaran with PLM is about 165 kg. When transporting, floats and a bridge are placed on the top trunk of the car - 108 kg, which is quite acceptable for a UAZ.

The carrying capacity of each buoyancy module of the PK-120 type is 120 kg according to the passport; six modules will give 720 kg, respectively. If we subtract 85.6 kg - the mass of the bridge with all deck structures and outboard motor - we are left with 634.4 kg. Typically, a safety factor of 0.75 is used for self-propelled watercraft, therefore, the payload capacity of this catamaran is about 475 kg, which allows you to take four people with luggage on board.

The contours of the floats of my vessel allow movement only in displacement mode at a speed of up to 10 km/h, so use a PLM more powerful than 5 hp. doesn't make much sense. Although with the installation of an 8-10 hp motor. you can try to reach a speed of 15-16 km/h when driving in transition mode. In this case, to regulate the running trim and reduce wave formation between the floats in the aft part, it is advisable to install a hydrofoil that performs the functions of a transom plate (shown in the dotted line in the figure). Mounting units for buoyancy modules type PK-120 allow this.

The described project of a collapsible deck boat-catamaran was developed by me and brought to working drawings of parts in 2015. All that remained was to order a set of buoyancy modules, but it was at that moment that I received an offer that was difficult to refuse...

CATAMARAN TYPE CRAIG CAT

A well-known classifieds website offered for sale a set of a homemade motor catamaran, consisting of two polystyrene foam floats and a collapsible plywood bridge. The homemade product was made in St. Petersburg based on the American catamaran Craig Cat, and its price was approximately equal to the cost of a set of six buoyancy modules of the PK-120 type.

Craig Cat.
Obviously, this “floating sun lounger” is designed for hot countries and warm seas. The remote control of the outboard motor is very unusual: not with a traditional steering wheel, but with an airplane-type handle. The lightweight two-seater Craig Cat motor catamaran was developed about 20 years ago and is still quite popular abroad. The model is very different from all the watercraft created before it. It has always been believed that in order to reduce the harmful interference of floats caused by their wave formation, they should be spaced from each other at a distance of no less than two widths of the float. Here, on the contrary, the floats are so close together that the outboard motor propeller can barely fit between them. The theory also taught that to ensure sufficient seaworthiness, the height of the floats and the clearance of the bridge should be no less than the height of the waves. Craig Cat's floats, made of polyethylene with foam core, are practically flat skis with a height of only 200 mm. The ability of such skis to ride a wave is achieved due to a fairly large running trim. Like a water skier's skis, the floats are movable relative to each other and can independently play the wave, which is achieved by the elasticity of the fiberglass bridge. Thus, from a hydrodynamics perspective, the Craig Cat can be considered nothing more than a motorized water ski.

View of Craig Cat from the stern.
Interesting features: flat-bottomed floats with gutters, and a hydroski and a powerful PLM are installed between the floats; the position angles of the motor and hydraulic ski are adjusted on the fly by electric drives; The drives are possibly controlled by the pilot, but it is more likely that the angles are adjusted automatically, depending on the engine speed. The length of the catamaran is only 3400 mm, width 1700 mm with the width of each float 700 mm. With its own weight without a motor of about 100 kg, the vessel’s carrying capacity reaches 340 kg. Thanks to the catamaran design, such a small “ship” can be equipped with quite large motors with a power of up to 25 - 30 hp. With such power, even despite all the hydrodynamic shortcomings of the design, Craig Cat with two crew members easily goes on planing and accelerates to speeds of over 50 km/h. According to the manufacturer, this catamaran on monolithic floats is a raft that cannot be filled and is very difficult to turn over. Its reliability was proven by Adam Gurzo and Trevor Bejkowski on a 750-kilometer crossing of the American Great Lakes. However, looking ahead, I will say that my own experience has shown that not everything is so rosy with the seaworthiness of the Craig Cat, as well as with the deck being splashed while underway.

It would be surprising if such an interesting, albeit unusual project did not become the subject of imitation. In Russia, the ENIGMA company offered for sale a collapsible catamaran “Betta” of exactly the same dimensions. Only the fiberglass floats are slightly higher than those of the American prototype, which increased the load capacity to 400 kg. "Betta" is designed for an outboard motor with a power of up to 15 hp. With a motor up to 10 hp. it belongs to the category of unregistered watercraft.

“Betta” is a simplified domestic analogue of Craig Cat.
A PLM with a power of only 5 hp is installed. There are no remote control of the motor, hydraulic ski and electric drives. The author of the homemade product, which I decided to purchase as a basic basis for my own design, exactly reproduced the layout and dimensions of Craig Cat, although technologically this is a completely original project. The floats are made of monolithic polystyrene foam with an external fiberglass lining with an epoxy binder. Such hulls are quite easily damaged when hitting stones, but can be easily repaired using automotive putty with fiberglass. The mass of each float is 36 kg.

The bridge with bracket for the outboard motor is made of waterproof FSF-B2 plywood 18 mm thick, it can be disassembled into four parts and weighs 35 kg. In my opinion as an aviation engineer, it’s a bit heavy, but I didn’t redo it for the sake of reliability. Unlike the prototype, some mobility of the floats is achieved not by the flexibility of the deck, but by the rubber-metal bushings of its attachment to the floats.

To adjust the centering, the bridge has two sets of holes for the bushings for its fastening. In calm water, the deck is set to the forward position and the centering is shifted to the bow. At the same time, the running trim is reduced, wave resistance is reduced, and the catamaran accelerates to higher speeds. With rear centering, the running trim increases, and the catamaran rides the wave much better.

For my wife and I, the main sailing area is the cold and turbulent Lake Onega. In such conditions, it is better to raise the seats as high as possible, then the waves freely rolling over the low floats can only wet your boots. Railing is also absolutely necessary. It is made collapsible, from elements of the mentioned “Joker” system. For seats, I use lightweight swivel office-type plastic chairs.

Catamaran, modified for operation on Lake Onega and the White Sea.
High swivel seats, railings, perforated luggage boxes and a bracket for a spare PLM are installed. At the stern there is a main motor of 5 hp, at the bow there is a spare motor of 1 hp. In this modified form, the catamaran has been operated every summer since 2015. During this time, a wide variety of engines with power from 1 to 15 hp were installed on it. During transportation, two floats and the stern - the heaviest - part of the bridge, with a total weight of 89 kg, are placed on the top trunk of the car, and the outboard motor and other structural elements are inside it. Assembling and disassembling the catamaran takes no more than half an hour.

Before the start of the 2022 season, I installed an additional front bracket for a small power spare motor. To perform its functions, the second motor must be able to operate in reverse by turning 180°. And it so happened that this “dokatka” had a power of only 1 hp. came in handy on the first trip. When the main engine, being flooded by the wave, refused to start, the spare one not only successfully crossed the surf zone, but also slowly brought us to the camp. And since the summer on the Kola Peninsula is cold, the water in Umbozero is icy, we seriously thought about a closed cabin...

Grigory DYAKONOV (To be continued)

We recommend reading

“PERSISTENT” ASKS TO FLIGHT This is what the aircraft model circle members and their leader, Vadim Borisovich Rumyantsev from the city of Privolzhsk, Ivanovo region, call their plane, with whose hands at the local station of young technicians (SUT)…
“CRUSADER” IN TANK FORMATION By the mid-30s, against the backdrop of mass production of tanks in the USSR and Germany, the development of armored vehicles in the UK sharply intensified. This was facilitated by…