The safety and durability of an inflatable boat depends on how well you've prepared it for the water, and many owners make the mistake of thinking that the harder the inflated boats are, the better. pressure-out It is as dangerous as insufficient and can cause joints to rupture or deform the structure.
In this article, we will look at all the nuances of working with air inside cylinders, explain the physics of the process of gas expansion when heated, and provide accurate tables of values for different conditions, you will understand why the gauge in the morning on shore and in the afternoon on water can be radically different.
We will pay special attention to the design features of models with NDMA (low pressure inflatable floor) because they require a more delicate approach than hard floorboard boats, and ignoring these rules often causes the product to fail prematurely.
Physics of the process: why the pressure changes
The air inside the cylinders obeys the laws of thermodynamics, and the most important thing for the owner of the boat is the Gay-Lussac law, which states that at a constant volume, the pressure of the gas is directly proportional to its temperature, which means that when heated in the sun, the air inside begins to grow. expand, creating an excessive voltage on the walls of PVC.
Imagine a situation: you pumped the boat in the morning at +15°C to a normal 0.2 atmosphere. By noon, the air and surface temperatures of the cylinders had risen to +35°C. A 20°C difference can increase internal pressure by 10-15%, which is already close to critical values for some seams.
That is why manufacturers always point out maximum-pressureIf you ignore this factor, the material may not withstand the load, especially in the places of gluing or near the valves.
⚠️ Attention: Never leave a fully pumped boat in direct sunlight unattended. Even in cloudy weather, the lens effect from water or glass can locally overheat the balloon.
What happens to air molecules when they are heated?
As the temperature rises, the kinetic energy of the air molecules increases, they move faster and hit the walls of the balloon more often, and it's these more frequent impacts that we measure with the pressure gauge as an increase in pressure, and in the closed volume of the PVC cylinder, this expansion has nowhere to go but to press against the walls.
Pressure standards for different types of boats
The standard values given in the passport are averaged, but there are clear boundaries for different design solutions. For the onboard cylinders of most models, the optimal range is from 0.2 to 0.25 atmospheres (kgf/cm2).
The bottom situation NDMA Because it's an inflatable structure, it can't hold high pressure, otherwise it'll lose its flexibility and become a drum. The operating pressure here is usually only 0.1 to 0.15 atmospheres, and exceeding that value makes the bottom rigid, but it deprives it of its shock-absorbing properties.
For boats with rigid plywood or aluminum floorboard, the requirements for the sides remain the same, but it is important to ensure that the pumped sides do not push the floorboard upwards, disrupting the geometry of the bottom. This is especially true for models with a width of more than 130 cm.
| Type of boat element | Recommended pressure (atm) | Maximum pressure (atm) | Features |
|---|---|---|---|
| Onboard cylinders | 0.20 - 0.25 | 0.30 | Main carrier |
| BNDD | 0.10 - 0.15 | 0.20 | Requires precise control |
| Keel (if any) | 0.20 - 0.25 | 0.30 | For course stability |
| Inflatable seats | 0.15 - 0.20 | 0.25 | For passenger comfort |
Effects of ambient temperature
The temperature factor is crucial when preparing the boat for operation. If you keep the boat in a warm garage or house, and the descent into the cold river, the pressure inside the cylinders will inevitably drop. pumping It's already on the water.
The reverse is more dangerous. If you pump the boat in the shade at +20°C, you risk getting pumped cylinders when you pull it out into the open sun, where the PVC surface heats up to +40-50°C. Under these conditions, the material becomes softer and the pressure inside rises.
Experienced water-engineers recommend using the "unpremeditated traffic jam" rule, and if you have a hot day and a long stay on the water, it is better to leave the valve slightly ajar or not to pump the boat to the maximum on the shore.
⚠️ Attention: Sharp cooling of cylinders (for example, when cold water from the depths hits the sun-heated side) can cause a local pressure drop and temporary deformation of the side, which affects handling.
Use a digital pressure gauge that can be calibrated (zero-drop) and it shows accurate values down to the hundredths of the atmosphere, which is critical for tuning the bottom of the NDL.
Instructions: How to properly pump the boat
The pumping process requires consistency and control, always inflating the main cylinders, then the keel (if structurally separated), and lastly the bottom. NDMAThis order allows you to correctly form the geometry of the body.
Using the right pump is key to success. You need a high pressure pump to finish and create working pressure. A conventional car compressor is good for the primary volume set, but it doesn't control the final 0.05 atmospheres well.
It is important to ensure that water or sand does not enter the cylinders, especially when using foot pumps on the shore.
☑️ The right pumping of the boat
After the initial pump, be sure to let the boat lie down for 10-15 minutes, during which time the material will stretch, and the pressure may drop slightly, only after that you need to perform the final adjustment to the desired values.
Features of operation of boats with NDND
Low-pressure inflatable boats are very smooth and smooth, but they require careful treatment. bottom of NDND If you press it with your hand, it looks like a rock, it means that the pressure is over.
The pumped bottom loses its main function of shock absorbing the waves, instead of extinguishing the impacts on the water, the hard bottom begins to transmit vibration to the boards and passengers, and the risk of joints diverged in the central part increases.
When stored in winter, these boats also require attention, and the residual pressure in the cylinders should be minimal, but not zero, so that the layers of PVC do not stick together, but do not create stress in the folds.
For boats, it is critically important not to exceed the pressure of 0.15 atm in the bottom, otherwise the structure will lose its shock absorbing properties and become vulnerable to mechanical damage.
Maintenance and pressure control
Regular leakproofing is a must, and even microscopic air etching through the valve or seam will eventually result in a drop in pressure and a loss of hull rigidity, and you need to check the boat before each season and after long storage.
Use a soap solution to look for leaks, apply it to valves and suspicious areas of the sutures, and the appearance of bubbles will indicate the place where you want to go. repair Or pulling up elements. Don't ignore even the slight hiss.
Keep the pressure gauge in a secure place. Falling or hitting it can knock it down, and next time you'll be targeting the wrong readings, risking the integrity of the boat. Periodically check the accuracy of the instrument.
⚠️ Attention: If the boat has been in the cold for a long time, put it in a warm room a few hours before checking the pressure, cold air in the cylinders will show an underestimated value.
Frequently Asked Questions (FAQ)
Can I swing the boat with a car compressor to the end?
Car compressors are great for filling cylinders with large volumes of air, but they often cannot create the final pressure (0.25 atm and above) and do not have a precise pressure gauge for small values.
Why does the boat seem soft in the morning and harden in the afternoon?
It's a normal physical process of air expansion when heated. In the morning, the temperature is lower, the pressure is normal. In the daytime, the sun heats the dark surface of PVC, the air inside expands, and the pressure rises, which is why you shouldn't pump the boat in the cooler hours of the day.
What is the minimum pressure allowed to go out into the water?
The pressure is considered to be below 0.15 atm, and at this level the boat loses stability, becomes a roller, and the sides can collapse in choppy conditions, and operating at pressures below 0.1 atm is dangerous and can lead to transom under the weight of the engine.
Do I need to blow the air after fishing?
Yes, if you leave the boat on the shore or in the car, in the evening the temperature will drop and the pressure will decrease, but if the boat is left in the sun, the risk of rupture will remain. To transport in the trunk, the boat must be completely deflated to avoid damage to the valves and seams.
Regular pressure checks with a pressure gauge before each fishing trip are the only way to guarantee safety and extend the life of your PVC boat.