Soviet and post-Soviet aluminium flat-bottomed squirrels are still “workhorses” in the vast expanses of Russian rivers and lakes, among them a special place is occupied by the Russian government. Ob M. It's a modification that differs from the classic version not only in the design of the transom, but also in the modified dimensions. Many aqueous motorists are looking for accurate data on the length of the Ob M boat to plan its transportation on the roof of the car or calculate the storage area in the garage.
The issue of dimensions is critically important, since it is the length and width that determines the stability of the vessel on the wave and the convenience of its movement on land. The length of the boat Ob M This is one of the key specifications that affect performance and stability, and unlike earlier versions, this model has a reinforced transom and slightly modified bow geometry, which necessitated revision of the standards in the documentation, and accurate measurements avoid unpleasant surprises when buying a trailer or planning a place in the boat shed.
In this article, we will take a look at all dimensions, compare them to other models, and answer questions that often arise from owners of this legendary vessel: how to measure length correctly, why data-sheet figures may differ from real ones, and what to look for when choosing a trailer for transportation. Understanding these nuances will help you operate the boat as efficiently and safely as possible.
data-sheet figures and real length measurements
Official documentation accompanying the aluminum boats manufactured by the Chkalov Novosibirsk Plant (Chkalovets) always indicated strictly regulated parameters. length of the boat It's exactly 4,500 millimeters, measured from the horizontal projection from the forehead to the farthest point of the transom, but in practice, owners often encounter discrepancies between the numbers in the documents and the roulette in their hands.
A difference of several centimeters is normal for products made of aluminum-magnesium alloy AMg5M. Technology welding and stamping metal allows certain tolerances, which can vary depending on the year of manufacture and the particular lot. In addition, the actual length may be affected by the presence of additional equipment, such as a shaft bar or keelson, which can act beyond the dimensions of the clean housing.
If you plan to make a case or calculate a place in the garage with an accuracy of up to a millimeter, it is better to focus on your own measurements. Ob M. It can be between 4,480 and 4,520 mm long, depending on the individual specifications of the particular specimen. Always leave a small margin when planning space, as metal tends to deform slightly during prolonged use or heating in the sun.
When measuring the length, use a stretched construction thread or laser rangefinder, applying them strictly parallel to the diametric plane of the boat to avoid errors due to the rounding of the sides.
Influence of the length of the body on driving performance
The size of the boat dictates its behavior on the water. The length of the boat Ob M 4.5 meters is optimal for maintaining the status of a flat-bottom, but already allows you to develop quite decent speeds when installing a powerful motor. The longer the body, the greater its displacement capacity and theoretical maximum speed that it can develop without going to the planing, although the Obi M is characterized by a planing mode.
The longer length of the Kazanka makes it easier to hold the wave, although it is inferior to larger models like the Crimea or Progress. The long hull has greater inertia, which makes the movement smoother, but requires an earlier start of maneuver for turning. Owners often note that at full speed the boat becomes roller if the load is unevenly distributed.
⚠️ Warning: Exceeding the permissible power of the motor on long-range modifications of the Ob can lead to a nose burrowing in the wave and loss of controllability, since the flat bottom is not designed to cut high waves at high speed.
It is important to consider that the length of the boat itself affects the wavelength, and in the shallow waters of many rivers in Siberia and European Russia, the long boat may experience resistance due to interaction with the bottom. Ob M. with its length has a certain sediment under load, and when passing rolls, care must be taken not to damage the skin of the bottom on stones or driftwood.
The length of 4.5 meters provides a balance between capacity and the possibility of plane with medium-power engines (up to 30 hp), but requires careful distribution of the load.
Comparison of dimensions: Ob M and other models
To better understand the scale and location Ob M. In the Soviet and Russian boats, you need to make a comparative analysis with the nearest competitors and predecessors. Often, water engines choose between buying a new PVC boat and used aluminum "classics", and here the size plays a decisive role. The length of the boat Ob M It distinguishes it from more compact models, providing more useful space in the cockpit.
Here's a table showing the difference in size between the Ob M and other popular models from the same period, and it gives you an estimate of how much more space you'll get by choosing this particular one.
| Model boat | Full length, m | Width, m. | Load capacity, kg |
|---|---|---|---|
| Ob M. | 4.50 | 1.60 | 400 |
| Kazanka-M | 4.00 | 1.45 | 300 |
| Crimea | 4.30 | 1.62 | 350 |
| Progress-2 | 4.45 | 1.50 | 400 |
As you can see from the comparison, Ob M. It's one of the longest in its class, second only to some specialized models. The width of 1.60 meters is also a significant advantage, providing good stability. However, it is worth remembering that increasing the length and width leads to an increase in the body's own weight, which must be considered when transporting.
Transportation and storage: calculation of dimensions
Transport planning aluminum-boat It requires careful calculation. 4.5 meters is a boundary value for many passenger cars. If you plan to carry a boat on the roof, you need to make sure that the length of the trunk and overhangs allow you to securely lock the body. Standard trunks are often designed to be up to 1.2-1.5 meters long between the points of support, so the Ob M will require special elongated arcs or remote brackets.
When transported on a trailer, the length of the boat dictates the length of the lozenge or nickel trailer. Ob M. It should be placed on the supports at least three points: at the transom, in the middle and at the forehead, to avoid sagging and deformation of the bottom when shaking on the roads. It is unacceptable to attach only to the nose and stern without intermediate supports, since the own weight of the metal is curvature of the skin.
For storage in the garage or under the canopy, the exact length is also critical. Be sure to add to the 4.5 meters the length of the engine if it stays on the transom and the length of the trailer is breathed. Overall length The boat + motor + trailer can easily exceed 6-7 meters, which requires considerable space for maneuvering and parking.
☑️ Preparation for transport
Design features that affect the size
Modifications Ob M. It's different from the base version, not only in terms of marking, but also in terms of design, and the main change was the transom board, which is more powerful and designed to be able to hold more powerful engines, which didn't change the overall length of the body, but it shifted the center of gravity closer to the stern, which is important to consider when you load. Tranza It became stiffer, which reduced the vibration of the stern at full speed.
Another feature is the shape of the zygomatic sheets and splash-blowers. Although they don't add significant length, they affect width and aerodynamics. In some cases, owners install additional tiles on the sides or forespeak, which can visually and physically increase the dimensions. When buying a used boat, always check if it was modified by the previous owner.
⚠️ Attention: Independent welding of additional aluminum sheets for lengthening the bow is strictly prohibited without professional calculation, as this violates the centering and can lead to the tipping of the boat.
The hull is made of an AMg5M alloy, which is weldable but requires technology. Any interventions in the geometry of the hull to change the length must be made with the metal thickness (usually 2 mm for the bottom and 1.5-2 mm for the board).
The letter "M" in the model name is often interpreted as "Motor" or "Modernized". The main difference was the reinforced transomboard and the ability to install more powerful engines compared to the earlier versions of the Ob, which were often equipped with low-power engines or intended for rowing.
Frequently Asked Questions (FAQ)
Can I increase the length of the boat by myself?
In theory, this is possible by inserting an additional section, but in practice it requires a complete recalculation of buoyancy and stability. Self-extension often leads to a violation of the longitudinal strength of the hull and a loss of warranty (if it is still relevant) or safety. It is easier and safer to sell a short boat and buy a model of the right size.
Is the length of 4.5 meters in the restrictions for control without a license?
According to the legislation of the Russian Federation, the rights of category "M" (boatmaster of a small vessel) are required if the length of the vessel exceeds 20 meters OR the engine power exceeds 8 kW (about 10.88 hp). In itself, the length of 4.5 meters is not a restriction for driving without a license if the engine power is less than 10.88 hp However, registration in GIMS is mandatory for all motor boats.
Which trailer is better to choose for a boat with a length of 4.5 meters?
The optimal choice would be a single-axle trailer with pawns, designed to load up to 750 kg (for Category B, customary law is sufficient). The platform length should be at least 5 meters to provide overhangs and space for mounting the winch. It is important to have a keel roller for easy loading.
Does the length of the boat affect fuel consumption?
A longer boat at the same width has greater friction resistance against water. Ob M. Because of its length and shape, the bottom is more likely to get on plane mode, which can be more economical than moving in displacement mode on a shorter but wider boat.
Where can I find the exact size of the M?
Original drawings can be found in the archives of Chkalov's factory or in specialized magazines such as Boats and Yachts for their respective years of production, and detailed dimensional grids are often published on powerboating forums where owners share their own measurements. Look for files labeled "Ob-M drawing" or "Ob M passport".