It isn't as easy as it looks?
- Written by Martin Northey
Berthing a Motor Cruiser or Yacht in a Marina is not nearly as easy as it looks, it requires training, a lot of practise, not too much of a crosswind and a little luck! Yachts and Motor Cruisers of course require totally different techniques and there are different types of each of those, each having its own particular handling characteristics.
Motor Cruisers
A motor cruiser can be extremely difficult to handle in a marina, most of them of less than 38 feet in length do not have a bow thruster and berthing with even a moderate cross wind can be very nerve racking for the beginner.
Many twin and almost all single engine modern motor cruisers of 42 feet or less have stern drives as can be seen in the photo to the right, this involves having the gear box and transmission outside the boat under the water, the design advantage of this is that the engines can be right at the after end of the boat thus making room for an additional cabin forward of the engines. Compared to a boat with fixed propellers, the disadvantage of this system is that the engines are a little closer together and so the propellers are closer together and so when used separately have much less turning effect on the boat. There is also some loss of power. In addition with the weight of the engines and stern drives so far aft, the boat is very inclined to be blown sideways by any crosswind. Another disadvantage is that with the weight of the engines so far astern the boat is very ‘bows high’ when accelerating up onto the plane and it is essential to use the trim tabs to get the bows down and the boat properly up on the plane.
For berthing it is enormously helpful to have a bow thruster with this type of motor cruiser as shown in the photograph to the right, even with a bow thruster they can be very difficult for the beginner to maneuver into a marina berth, there are four things to do, one which engine to put into gear, two whether to have it in ahead or astern, three which way to turn the steering and four when it all goes pear shaped which way do you push the bow thruster control to get you out of trouble. It’s a bit like patting your stomach with one hand whilst making circular movements with the other on the top of your head.
Motor cruisers in excess of about 42 feet tend to have fixed propeller shafts as in the photograph to the right, the propellers tend to be a little further apart and larger and so have a greater turning effect when used individually when berthing. In addition the engines will be positioned further forward, putting the boats weight more in the center and so the boat is less inclined to be effected by strong crosswinds. When berthing this type of motor cruiser it is neither necessary nor helpful to use the steering, maneuvers to position the boat can all be achieved with the use of the engines at low revs. Most boats in excess of about 42 feet have a bow thruster fitted, whilst we may not use it the whole time for berthing it is enormously helpful to have in reserve should it be needed.
The most difficult of all types of boats to handle in a marina are small single engine motorboats with stern drives; some of them have a profile remarkably similar to a block of flats and not too much of the hull actually sitting in the water. With the engine right at the stern, plus the weight of the stern drive, the forward part of the boat has very little grip on the water and so will be blown sideways with the greatest of ease. Much as we all like to berth ‘stern to’, berthing one of these backwards in any kind of a wind we stand a very good chance of getting it seriously wrong. Most people, and this will include the manufacturers will tell you that you don’t need a bow thruster in a single engine boat of less than 30 feet. I completely disagree with this view. As most boats of this size have a stern drive system, it is enormously helpful to have a bow thruster which will enable you to berth ‘stern to’ in a cross wind that would make it impossible without one.
Yachts
There are several different types of keel and propulsion systems with yachts. With each type of configuration you will experience differing amounts of ‘prop walk’ and ‘prop wash’.
Prop walk occurs when you are trying to stop or slow down by engaging astern (reverse). It is also known as ‘paddle wheel’ effect; this happens because propellers are shaped to drive a boat forwards, not backwards, so when in astern a propeller will pull a boat backwards but rather ineffectively. It will also work like a paddle wheel and actually move the stern of the boat to one side. As to which side the stern will go depends on which way round the propeller goes when the gearbox is in astern (different engines go in different ways). It is possible to discover which way prop walk is going to make a boat go by engaging astern whilst the boat is still tied to the pontoon, then look over the sides of the boat and you will see that the majority of the wash created by the propeller will be coming out from one side, you can be certain then that when in astern the boat will swing away from that wash. So for example if the majority of the water is coming out on the port side then in astern the boat will clearly swing to starboard. This is known as starboard prop walk.
Prop wash occurs when the engine is in ahead and with the rudder hard over to one side. A burst of power in ahead will shoot a stream of water backwards half of which will be reflected off the rudder which will have an instant and pronounced turning effect on the boat without actually driving it forward too much.
When it is necessary to turn a boat almost within its own length firstly a decision must be made to turn the boat in the direction of its prop walk, then with alternate bursts of ahead and astern the boat will revolve in not much than its own length as a result of the combined effect of prop walk and prop wash.
The different types of hull configurations are as follows:
The easiest to handle in a marina is a yacht with a fin keel and unsupported rudder and an engine with a fixed prop shaft and propeller. see the photograph on the right. This type you can often steer as well backwards as you can forwards. You will experience both prop walk and prop wash and providing you make use of and allow for them this type of yacht will be very easy to handle in a marina.
Another type that is moderately easy to handle in a marina is a yacht with a long fin keel, a fixed prop shaft and a skeg-hung rudder. See the photograph on the left. This type can be difficult to steer in astern particularly if the wind is on the same side as the prop walk. Prop walk and wash will be quite pronounced, but very useful if you make use of them.
The most difficult and certainly the most unpredictable is a yacht with a full length long keel. They are usually impossible to steer backwards, they do have prop wash, which can be used to advantage but prop walk is often unreliable, the green yacht to the right is an example.
Also difficult is the type of yacht that has a drive leg directly connected to the back of the engine and passing through the hull just behind the engine, there is an example shown to the left. This type of configuration which is known as a sail drive will have very little prop walk because the propeller is too close to the middle of the boat to have any turning effect. It won’t have any prop wash because the propeller is often as much as three meters in front of the rudder and therefore any stream of water created by a burst in ahead will have lost its power by the time it reaches the rudder. Whilst it will be possible to steer this boat backwards turning it round in its own length will not be easy.
So berthing a boat in a marina is not always easy and with a boat that a skipper is not familiar with it can be quite difficult to get it right. I often see people getting it badly wrong and am surprised by the fact that these same people have often got just three fenders and all of those are just on one side, which I feel shows a combination of over confidence and a lack of imagination. When I am bringing a boat into a marina berth I like to have a minimum of eight fenders, four of which will be almost touching the water on the side of the pontoon and the other four on the other side. The four on the other side will be much higher if there is a boat on that side, or at water level if there an empty berth. An owner may well argue that fenders are expensive, but gel coat repairs are much more.
My conclusion to all of the above is that when we see a motor cruiser or yacht berthed well, the skipper deserves our respect and admiration, when it all goes badly wrong it is our sympathy and understanding that should be the appropriate reaction!
Article and photos - Martin Northey
Martin Northey - RYA Yachtmaster Examiner / Instructor for Sail & Power
Tel: 00 351 965 800702.
Email: martin.northey@mail.telepac.pt
Skype: martinnorthey
Web Site: www.theiberianseaschool.com
