The process of preparing a boat for launch is often underestimated, considering it a simple routine, but it is the right pumping that determines the safety and durability of your equipment. PVC boats They make the critical mistake of relying solely on tactile sensations, where the side seems hard enough to the touch, but the gauge shows insufficient values. Insufficient pressure leads to deformation of the bottom and reduced driving performance, and excess in hot weather can break the seams or damage the valves.
The standard pumps that come with most models are often criticized for seeming inefficiencies, especially in windy weather or low temperatures. foot-frog Or a two-chamber hand pump that can provide the necessary tightness and rigidity of the structure, if you know the technical nuances of their work. In this article, we will discuss in detail the physics of the process, the difference between atmospheric and overpressure, and the step-by-step algorithm of actions.
It is important to understand that the material polyvinyl chloride It has a certain elasticity that varies with the temperature of the environment, and the pressure that was ideal in a cool garage in the morning can be devastating to the design by noon, so knowing the exact parameters and being able to control them is not just a recommendation, it's a necessary condition for operation.
Principles of operation and physics of pressure in cylinders
Before we start to act, we need to understand what we measure with a pressure gauge. floatboat The operating pressure is between 0.2 and 0.25 atmospheres (or bar), equivalent to 200-250 millibars, which seems negligible compared to tire pressure, but for a large surface area of the balloon, this force is sufficient to withstand the weight of passengers and wave shocks.
The key is to understand the difference between absolute and excess pressure, and the standard pressure gauges on the pumps show exactly what they are. pressure-out The difference between the pressure inside the cylinder and the pressure outside, when the pressure gauge is at zero, it means that the pressure inside the cylinder is atmospheric, meaning that the balloon is actually empty, even though it is straightened.
⚠️ Warning: Never rely on the hardness of the sides as the main criterion. The human hand is not able to accurately determine the difference between 0.15 and 0.25 atmosphere, and this range is critical for the hardness of the bottom.
Gay-Lussac's law of physics says that when you heat a gas in a closed volume, it increases its pressure. cold-morning At a maximum of 0.25 atm, the pressure inside can jump to 0.3-0.35 atm when exposed to the sun, creating dangerous tension in the tissue and seams, so you should always leave a small reserve or burn air before going out into the open water on a hot day.
Why do the pumps seem weak?
The standard pumps are designed to create high pressure with low air intake. In the first stage (spreading the balloon), they work slowly, because their task is to overcome the resistance already in the air, not just fill the volume. This is normal and requires switching modes or using different sides of the piston.
Preparation of equipment and selection of a pumping site
The efficiency of the regular pump depends on the conditions in which the process takes place. Choosing the right place to prepare the boat is the first step to success. The ideal surface is a flat grassy area, a sandy beach without sharp stones or a special synthetic coating. Concrete or asphalt can only be used with a protective mat, because friction of PVC on rough asphalt during pumping can damage. reinforcement tissue.
Before you start, you need to do a visual inspection of the pump itself, check the integrity of the hose, the absence of cracks on the pressure gauge and the reliability of the attachments. Often, there are adapters for different types of valves, and it is important to choose the right one right away so that the valve petals do not damage. High Pressure or Bravo when inserted.
- 🌬️ Check the purity of the air channels of the pump - the ingress of sand inside the cylinder can violate the tightness of the piston group.
- 🌡️ Make sure the gauge shows zero in a calm state; if the arrow is cruising, the readings cannot be trusted.
- 🧹 Clean the valves on the boat of dust and sand before inserting the hose tip.
And you also need to consider the direction of the wind, and if you're on the shore of a body of water, try to position the boat with your nose against the wind, and this will prevent the already inflated compartments from blowing out of control while you're working with other cylinders, which is especially true for models with a high-speed air-powered surface. keel.
Phased pumping technology of cylinders
The pumping process cannot be randomly switched between cylinders. There is a strict sequence, the violation of which can lead to skewed design and difficulties with the installation of floorboards (plywood or aluminum floor), the side cylinders are always pumped first, but not to full pressure, but to about 60-70% of normal, which allows the boat to spread out and take shape, but leaves the material elastic.
After the sides are straightened, a transom board is installed and the bottom is assembled. bottom (if it's designed) because it has to be cut under the weight of floorboards. If you use a hard floorboard, it requires that the sides be malleable. Only after the floor is fully assembled and the stringers are fixed can you start to push the pressure to the working values.
☑️ Checklist of proper pumping
The final step is to pump the inflatable keel (Kilson) and this element must be inflated with the latest and maximum value specified in the data sheet (often up to 0.25-0.3 atm, but check the instructions specifically for your model). PVC boatsThe hard keel provides the right hydrodynamics and course stability, and if you pump the keel before the sides, it can rest on them and deform the structure when it is pumped further.
Table of recommended pressure and temperature adjustments
It is dangerous to average, as different manufacturers use PVC fabrics of different densities (e.g. 750 g/m2 or 1100 g/m2). The denser fabric is able to withstand more pressure, providing better rigidity. Below is a table that helps you navigate depending on the type of element of the boat and the conditions.
| Element of the boat | Pressure (atm/bar) | Pressure (psi) | Features of control |
|---|---|---|---|
| Side cylinders | 0.20 – 0.25 | 2.9 – 3.6 | Control in the sun |
| inflatable floor (NDB) | 0.12 – 0.18 | 1.7 – 2.6 | Do not pump to avoid bloating |
| Inflatable keel | 0.20 – 0.30 | 2.9 – 4.3 | Must be as hard as a log. |
| transom plates | 0.15 – 0.20 | 2.1 – 2.9 | Depends on the power of the motor. |
The temperature factor is crucial. The rule is that for every 10 degrees Celsius increase in ambient temperature, the pressure inside the balloon increases by about 0.02 to 0.03 atmosphere, which means that if you pump the boat in the shade at 15°C to 0.25 atm, the pressure in the sun at 35°C will rise to 0.30 to 0.31 atm, which can be critical.
⚠️ Warning: In hot weather (+30 C and above), it is recommended to pump the boat to the lower limit (0.18-0.20 atm) to avoid rupture of the seams from thermal expansion of air.
For precise settings, use gauge Cheap pressure gauges often have a large margin of error, making them unsuitable for precise pressure adjustment in PVC boats. It is better to buy a separate high-quality pressure gauge than rely on a built-in cheap pump.
Nuances of operation of regular foot and hand pumps
The main types of regular pumps are leg pumps and hand pumps, two-chambered pumps. The good thing about foot pumps is that they leave your hands free and allow you to use your body weight to push air, but they have a nuance: when you reach pressures above 0.15 atm, effort increases dramatically, and it becomes difficult to push the membrane.
Manual dual-chamber pumps are more efficient in the final stage of pumping. They have two modes of operation, indicated by the numbers 1 and 2 (or A and B) on the piston. In position "1" (extended) pump captures a large volume of air, but creates a low pressure - this is for the initial stage. In position "2" (narrowed) volume of air captured is less, but the pressure at the output above is the mode for the air. pressure-fix.
To make it easier to pump the boat with a hand pump in the final stage, lubricate the piston cuff with a few drops of silicone oil or just water, which will reduce friction and improve slip, making it easier for the piston to travel.
A common problem is heating the pump. When you're working, the pump body and the air that comes out can get warm. When you get hot air into the boat, it shrinks the pressure. So after you pump, let the boat stand for 10 to 15 minutes and check the pressure gauge again, and it's probably going to take a little bit of time. adjustment.
Use the high pressure mode (position 2) only in the final stage of pumping, when the balloon is already straightened, using this mode from the beginning will quickly tire you and will not give you a gain in time.
Typical errors and security measures
One of the most common mistakes is to ignore the position of the valve. Bravo or High Pressure There's a central lock button. In the lower position (pressed), air enters the boat and does not come out. In the upper position (convex), the reverse valve works. Many people forget to press the button before starting pumping, which prevents air from entering the tank, and the user only wastes energy.
Another mistake is to leave the boat in the sun completely pumped unattended. Even in cloudy weather, ultraviolet light heats the dark fabric, and the pressure rises. If you take a break from fishing or have lunch on the shore, be sure to check the pressure before getting on the water. Excess pressure makes the boat "drum", it becomes uncontrollable on the wave and easier to get punctures of erudible objects.
- 🚫 Do not use car compressors without a pressure gauge and a pressure control system – they can tear the cylinder in seconds.
- 🚫 Do not leave a pumped boat on the shore unattended in the heat, even in the shade.
- 🚫 Do not try to increase the hardness of the bottom above normal, hoping to improve planing - this only warps the geometry.
Also worth remembering is the tightness of the valve caps. After pumping, be sure to twist the safety caps. They often contain a sealing gum, which serves as an additional barrier. If the cap is not twisted, sand or water can enter the valve, which will lead to etching of air at the most inappropriate moment on the water.
What to do if the pressure gauge is lying or broken?
If the regular pressure gauge is out of order, you can use the deformation control method. When pressing your hand on board an inflated boat (at +20 ° C), the deflection should be about 1-1.5 cm If the side is broken more strongly - the pressure is low. If the side is hard as a stone and not broken at all - the pressure is likely above normal. However, this method is subjective, and the best solution is to buy an inexpensive universal pressure gauge for PVC boats.
Can I drive a boat with a compressor from a car?
You can use a car compressor, but with extreme caution, and only if it has a built-in pressure gauge with a shutdown function (Hitchhike) Car pumps create a very powerful flow, and if you miss the time to reach 0.25 atm, the pressure will increase instantly, which will lead to a rupture of the seams. It is better to use the compressor only for the primary dispersion of the cylinders, and the final fine-tuning is done manually.
Why does the water pressure drop after pumping on the shore?
This is a normal physical process. Water is generally colder than air, especially in spring or autumn. When exposed to cold water, the air inside the cylinders cools and contracts, causing pressure to drop, so it is recommended to pump the boat just before descent or have a pump for easy pumping already on the water (in shallow water).
How to keep a regular pump so that it lasts longer?
After use, the pump must be dried. The cylinder often gets moisture from the air or condensate. Keep the pump disassembled (if the design allows you to remove the hose) or with open valves in a dry place. Rubber cuffs can stick together over time, so it is useful to periodically lubricate them with silicone.
Does altitude affect the pressure in the boat?
Yes, it does. Atmospheric pressure drops with altitude. If you pump a boat up to 0.2 atm at sea level and then climb up a mountain lake, the difference in external and internal pressure will change. However, for ordinary rivers and reservoirs, this difference is negligible and does not require correction.