Effective anchoring of an inflatable boat is not just a matter of convenience, it's a key element of safety on the water. PVC It has low draught and high sailing, making it vulnerable to wind and current even in a mild storm, which is why the right anchor drawing for a PVC boat becomes the starting point for self-manufacture of a reliable device that can keep the boat in place.
Many beginners make the mistake of relying on random objects like a bunch of bricks or old engines without understanding the physics of the process. Gravitational anchor The boat is kept only by its weight, whereas the paw structures work by burrowing into the ground, which requires accurate calculation of angles and geometry of the legs. If you plan to fish on the current or in windy weather, you will need a device made according to proven engineering schemes, not by eye.
In this article, we will discuss detailed diagrams of popular models, weight calculation methods and nuances of materials that will provide your boat with a reliable parking lot. A properly selected drawing will save money and get an anchor that is ideal for the dimensions of your inflatable board.
Containment Physics: Gravity or Engagement?
Before starting the manufacture, you need to clearly understand the difference between the two basic principles of the operation of anchors. Gravitational anchorsThese are the ones that hold the boat solely at the expense of its own weight, and their effectiveness is directly proportional to its weight, which for light PVC boats often means carrying 10-15 kg of metal, which is not always convenient.
They work differently. paw-anchor (Danforth, Hall, Sailor) They're designed to push the ropes into the ground, and they can hold up to 10 to 50 times their own weight, which is why PVC anchor designs are more often oriented toward paw structures, allowing lighter products to be used at high efficiency.
⚠️ Warning: Using an anchor too heavy for a light inflatable boat can cause a dangerous roll or even tip over the vessel when a sharp jerk occurs. The weight of the anchor should be approximately 10% of the boat's carrying capacity, but not exceed comfortable limits for carrying.
When choosing a design type, it is also important to consider the type of bottom on which you plan to fish. For a slurry or sandy bottom, wide paws are ideal, and for rocky soil, designs that can get stuck between stones are better suited, but do not damage the cylinders when sampling.
Calculation of the mass of the anchor for an inflatable boat
There are several empirical formulas for determining the weight required, but they only give approximate values. The classic McGauer formula states that the mass of an anchor in kilograms should be equal to the length of a boat in meters multiplied by a coefficient. For quiet water, the coefficient is 1, and for open water, it is up to 1.5.
For inflatable boats, where every extra kilogram of weight is critical, it is better to use a more accurate calculation, taking into account the sail area and wind strength. Anchor mass It's supposed to compensate for the wind and current, and if you use a paw structure, it can be much less than gravity, because the shape does the most work.
Below is a table of indicative values of the mass of the anchor depending on the length of the PVC boat and operating conditions:
| Boat length (m) | Mass (gravitational) | Massa (paw, Danforth) | Fallin diameter (mm) |
|---|---|---|---|
| 2.0 - 2.5 | 4 - 5 kg | 2 - 2.5 kg | 6 - 8 |
| 2.8 - 3.2 | 6 - 8 kg | 3 - 4 kg | 8 - 10 |
| 3.5 - 4.0 | 10 - 12 kg | 5 - 6 kg | 10 - 12 |
| 4.2 - 4.8 | 14 - 16 kg | 7 - 8 kg | 12 |
If you plan to fish on a strong river or in conditions of constant gusty wind, the mass should be increased by 20-30%. anchor-linewhich adds a load to the construction.
For boats up to 3 meters long, the best solution would be a folding anchor cat weighing 3-4 kg, which easily hides in a haunduk. For larger boats, it is better to make an anchor Danforth.
Danforth Anchor Drawing: Geometry and Proportions
Danforth's anchor is considered one of the most efficient for low-bearing soils (sand, silt), characterized by long, narrow legs and a movable transom bar, and the design of an anchor for a PVC boat of this type requires strict proportions, otherwise the device will not be able to properly burrow into the ground.
The basic element is spindleThe angle between the plane of the legs and the spindle in the working position should be about 30-40 degrees. If the angle is larger, the anchor will simply drag along the bottom; if less, it will rest with its nose and not catch. It is critical to correctly calculate the length of the transom slat (stack slat) that prevents the structure from piling on its side.
- 📐 The length of the paw is usually 60-70% of the total length of the spindle.
- ⚖️ The width of the paw should be about 25-30% of the length of the spindle.
- 🔗 The cable is attached to the spindle at a distance of 1/3 of the length from the nose (where the bracket for the cable is located).
- 🔩 The movable bar is set perpendicular to the spindle at the bottom.
Hand-made steel is often made with a thickness of 4-6 mm, the paws are cut out in a pattern and welded to the central axis, and the sharp front edge of the paws can be further strengthened or sharpened to facilitate initial entrenchment in dense soil.
⚠️ Attention: When welding the design of Danforth, make sure that the paws are symmetrical relative to the central axis. A skew even 2-3 millimeters will cause the anchor to constantly lean to one side, and it will not be able to enter the ground normally.
The Secret to Danforth's Efficiency
The key is the movable bar at the bottom, and when the anchor is down, the bar first touches the ground and, thanks to the tension of the cable, flips the structure with its paws down, causing them to crash into the bottom, and without that bar, the anchor can just lie upside down.
Manufacture of folding anchor-cat DIY
For owners of small inflatable boats, which often move between bodies of water on public transport, the ideal option is a folding "cat"; its drawing is simple, but requires accurate work with metal so that the folding mechanism functions without jamming even after hitting sand and silt.
The design consists of a central rod And four horns are attached to a movable sleeve, and when they're working, they're spread out to the sides, forming a strong hook, and they're held in place along the rod, and the key element is the bottom sleeve, which has holes in the ends of the horns.
The manufacturing process requires the following steps:
- Preparation of the central rod from reinforcement with a diameter of 14-16 mm.
- Manufacture of horns from a rod with a diameter of 10-12 mm with pointed ends.
- Creating a lower sleeve with holes at an angle of 45 degrees to the axis.
- Assembly of the mechanism and checking the freedom of movement.
To prevent the horns from rusting or staining the boat, they are often covered with zinc or special rubber paint, and a small load is sometimes welded onto the bottom of the rod to shift the center of gravity and improve stability in chop.
☑️ Checklist of manufacture of anchor-cat
Materials: steel, lead or concrete?
The choice of anchor material is a trade-off between cost, weight and durability. blacksteelIt's very durable, but it's very corrosive, and to protect against rust, it needs to be painted or galvanized regularly, otherwise it can damage the boat floor.
Some craftsmen try to use lead because of its high density, which makes the anchor very compact. However, lead is a soft metal, and its legs can deform when hit by stones. Also, pure lead is toxic and requires care.