Greetings,
I am very pleased with Ship Simulator becoming reality, let there be no question about that. However, I feel
PRIDE OF ROTTERDAM Ship Simulator
Steering Effects for berth and umberth
Steering
In the case of the POR is important to mention that as she is 2 screw drive most common she have left hand for one propeller and right hand for the other propeller, this diverse handles cause an stabilization of the hydro-interaction of the vessel, with rudders at midship the vessel will be well steered. Of course as faster as she could run a faster response of the hull on the steering will be pronounced with speed lower than 5kn the response will be much slower and or nothing due to the wind angle and force of attack against to the ship’s structures and hull.
On the umberthing and or berthing maneuvering to use the propellers at different attack is very helpful for sideways slide and or 180dG turning. Is important to keep in mind that with double screw where the propellers (shafts) are turning on a different hand to use the port propeller to slow ahead and starboard propeller at slow stern and the rudder full to starboard it’s helpful as long as the interaction effects are pushing the vessel to the side to where you want to turn and not attacking the vessel from the side to where you need to turn. This method can be used without steering too. Rudder at midship.
Very important the stern force are small pronounce than the fwd force.
If do you have one propeller to ahead and other to stern the one turning ahead will pronounce it’s effects stronger than the one stern. In case of left hand port propeller the ships stern will slide to the port. With the starboard propeller handling stern and on the right handling it’s will not decrease so much the ships stern port slide due to it’s lake of power pronouncement.
Shallow waters
With a lake of under keel clearance (Shallow waters) the propellers have to present more power in order to attend the wished movement, due to the lake of water present the propellers suction gape will try to suck the bottom (Impossible) and this will reduce the ship’s performance and rudder’s performance too. At some large and width vessels this shallow water’s may cause a lake of performance up to 20% of the ship’s turning rate and or lost of maneuverability.
Banks cushion effects
Sloop banks cause a lost of performance but not more than a steep bank, the cushion effects may push the vessel against the side to where you want to handle the ship and to avoid a deviation of the course at some times you are obliged to turn the rudder on the same way where is the bank to avoid that the mass between bank and vessel push to bow to the other side of the channel, this force is well observed during narrows channel passage. With tugs connected it’s require more tugs force to avoid the deviation.
Bow and Stern Trust
The bow and stern trust are very effective with speed smaller than 4kn over this the much used power will be useless for the sideways slides and or steering.
Skin friction (Where is the break!!! I can’t stop she at all)
Is important to master to award of the ships skin friction this presence of factor cause the water friction to the hull during channel and or sea passage the vessel is carrying a significant amount of water together with her at the big mould vessels this amount of water can be up to 15% of the vessel’s displacement, this mass that slide together with the vessel extend from the bow up to abaft stern gape. This mass of water which is found sliding with the vessel behind the stern is so called as dead water, in a heavy stop of the engine this mass may push the vessel stern to an unknown side and push the vessel more ahead of the planned stop point. It’s recommend to made in practice to apply a re-direction of speed reducing it by the way points till have a safety stop speed considering shallow waters and squat effects and also channel and or sea current and wind angle of attack. This practice is common performed on width channels for anchorage and or waiting / meeting points.
Resume;
On the PRIDE OF ROTTERDAM part of the above mentioned effects are well presence and observed and same effects can be observed with the LATITUDE (Super Tanker) and VEERMAS (Container vessel).
Would be so realistic if SS team applying more effectiveness for the steering. And for the Shallow waters / Bank cushion effects / Bow and stern trust and the must important ship’s water and ship to ship interaction which today are almost pronounced.
Study and information form the Principles of the Naval architecture Part I and II, Ship Handling and Tug Use in Port.
By Juvenal Tavares Junior
