Tube diameter: better big or small?

The diameter of the tubes is generally functional to the size of the boat.

If the dinghy has a tubular section that is too small it becomes a boat, while if it is too large it becomes a balloon. The dimensional range usually fluctuates from a minimum of 40 cm in diameter at the stern to 70 and beyond for boats over ten meters long.

The diameter, and therefore the section, affects what the volume of air is and, therefore, the buoyancy reserve.

The choice between a small or big diameter for RIB (Rigid Inflatable Boat) tubes depends on several factors and the intended use of the boat. Both small and big diameter tubes have their advantages and considerations. Let’s explore each option:

1. Small Diameter Tubes:

   • Maneuverability: Smaller diameter tubes offer better maneuverability, making it easier to navigate in tight spaces and perform quick turns.
   • Speed: Smaller tubes create less drag in the water, which can result in increased speed.
   • Weight: Smaller diameter tubes are generally lighter, which can improve the boat’s overall weight and portability.

2. Big Diameter Tubes:

   • Stability: Larger diameter tubes provide greater stability, especially in rougher waters. This can be advantageous for activities like diving, fishing, or carrying heavy loads.
   • Buoyancy: Big diameter tubes displace more water, resulting in higher buoyancy and improved load-carrying capacity.
   • Comfort: Larger tubes offer more deck space, making it more comfortable for passengers and allowing for additional storage.

Ultimately, the choice between small or big diameter tubes depends on the specific use case and personal preferences. If you prioritize maneuverability, speed, and portability, smaller diameter tubes may be preferable. On the other hand, if stability, buoyancy, and carrying capacity are more important, larger diameter tubes may be the better option. It’s essential to consider your intended activities, the water conditions you’ll encounter, and the trade-offs between different tube sizes. Consulting with experienced boaters or RIB manufacturers can provide valuable insights tailored to your specific needs.

The smaller inflatable boats, therefore subject to greater load, have generously sized and proportionally larger tubulars, while those used on the maxi-ribs appear more exhausted and less bulky.

Obviously, each shipyard makes its own choices, often linked not only to technical but also commercial or convenience needs.

The “fender” tubulars, that is, of small section, have little sense when mounted at the bottom, since their purpose is not to affect the attitude but only to provide a buoyancy reserve in a dangerous situation, or they are useful for boarding vehicles. for work (they are often also foamed and cut resistant); in some cases, finally, they only serve to “make a scene” and allow the builder to “sell” it to a rubber dinghy even if, in reality, this is not.

Tubes of generous dimensions, even on inflatable boats that are not exactly small, are usually the prerogative of transport boats, called to bear heavy loads, while on a semi-rigid pleasure boat, which often travels in light weight, they protect better from splashes and also provide a reassuring sense of protection to passengers, but they have two flaws: they offer a remarkable wind grip, which means a high leeway in strong wind and a broken attitude on rough or strong wind in the bow, which in extreme cases can lead to overturning of the medium.

The second flaw is that the very large tubulars greatly reduce the internal space. To overcome this limitation, but also to give the boat a more slender and sporty line, it is customary to taper the sections towards the bow by up to 20%.

To do this, however, requires considerable skill on the part of the builder and affects the final cost of the artifact.