By the term of deadrise we mean the angle which is formed between the horizontal plane and the side of the hull, at its any point.
As it can easily be understood, this angle is not constant but varies gradually over the whole length of the hull. In other words, the deadrise angle starts with its lower value at the transom and gradually increases as the hull goes forward until it takes its maximum value at the bow, where the hull cuts the wave.
It is a fact that every manufacturer of outboard engines installs different gear ratios while we see that as the horsepower decreases the gear ratio gets higher (numerically), which means the revolutions per minute of the propeller decrease.
As we have seen in previous articles, everything is a matter of Torque and combination of propeller’s diameter and pitch.
The torque that is produced by the engine is converted to thrust by the combined effect of the gear ratio with our propeller. Physics teaches us that the Torque is proportional to the horsepower (Hp) and inversely proportional to the rotation speed (Rpm). Thus, the higher the horsepower or the lower the rpm of the propshaft is, the greater the torque that is produced gets.
The propeller rotates at the same speed with the propeller shaft, while the propeller shaft usually rotates much slower than the engine crankshaft turns, at the same throttle setting. This is due to the reduction gear which exists on all the outboard engines among their crankshaft and propeller shaft.
Many people believe that trim tabs are useful only on large cruisers or hulls with inherent imperfections in their design. There is also the opinion that well-designed hulls do not need the assist of trim tabs. The practice, however, shows us that the smaller the boat is, the greater the need for trim tabs gets, because they are much more affected by weight distribution while under certain circumstances the use of trim tabs will greatly help even the best designed hulls.
Many of us who like living like Robinson Crusoe avoiding the overcrowding of the marinas and ports, defying in parallel, the amenities they offer. So, if we belong to the category of those people who prefer to moor in natural bays of their liking, to enjoy the loneliness of the night and to start their day diving in crystal clear waters, then we must be very well organized, completely autonomous and to be aware of some basic things.
When the sea puts on its happy face, any kind of fault or negligence might remain unnoticed. But when it is "wild", it does not forgive even the slightest negligence and things can become even more dangerous both for the safety of the boat and of ourselves.
The last few years, due to global warming, severe weather phenomena appear more and more frequently, especially in the north Aegean Sea. Bursts of storms are quite often and last for several days. Loaded skies, torrential rain, steep temperature decrease and countless lightnings tear up the horizon from edge to edge. Intense and dangerous weather phenomena which were not common in our seas.