The power of multi-hull sailing
Sailing
Classes
Sailing of a multi-hull is often described as very difficult.
But is this true?
If you have a well-designed boat and have some experience , it’s not difficult at all!
Centre of gravity
But if you turn away from the wind the boat will almost certain turn
over. Normally when the centre of gravity is in the right position a
catamaran and a trimaran with big out-riggers can sail on one hull without
turning on its side. If you have a trimaran with a smaller size hull the hull on the down
wind site might submerge. Most boats can cope with this without turning over. But be aware not to turn the boat away from
the wind!
This turning into the wind is not often used with a mono-hull. If you have a mono-hull that’s capable of getting on the plain you will
turn the boat a little of the wind to gain additional speed.
An other thing you have to avoid is sailing down wind. The bows of a
multi-hull don’t have much lifting capacity, there for the bows might submerge,
the boat will stumble and turn over. During slow wind speed you don’t have this risk of a stumbling.
Once you have some feeling for the boat you will probably enjoy sailing
you boat at the cutting edge. If you sail a multi-hull you will discover that your boat is going more
slowly throe the wind.This is caust by the gouge beam of the boat and the lower weight. A small boat will
turn faster and a heavier boat will keep longer his momentum.
If you turn into the wind, don’t give to much rudder. Wait until the boat start responding.
As soon as the boat loses it speed give more rudder. The boat will turn and pickup speed, once sailing over the other bow.
Turning over of the boat.
Stability problems
Steering problems.
Some boats with multiple rudders are very difficult to steer through the wind.
They will loose virtual al speed as soon as you turn the rudder.
In most cases this is caused by the so called “akkerman” effect; the difference in
turning angle of the inner and outer rudder. (On cars we have the same problem with the front wheels when we take a
corner.)
The rudders will always stand in the right position as the tillers are mounted under an angle.
If you set the rudders for sailing strait forward the alignement of the tillers will meet in the middle of the boat there where the bows are making
contact with the water. This is the proper alignement of the tillers.
If the boat makes a turn the rudders are always in the proper angle.
See the photos on the right) Alignment of multiple rudders.
If the rudders are in the position of sailing strait forward the distance between the frond and rear of the rudders must be
equal.
If this is not the case the rudders will go throe the water as a plough.This will give a lot of
drag.
Sailing is the same as with a mono-hull but you have to be more aware of the centre of gravity of the boat.
If you neglect the centre of gravity a mono-hull will only be slow while a multi-hull might dive, stumble or turn over.
Basicly you have to put the weight to the front of the boat when
sailing with slow wind speed. This will reduce the wet service and the drag
behind the boat. This is also done with a mono-hull.When the wind gets stronger you have to bring the weight to the rear.
This will reduce the chances of submerging of the bows. If you don’t reposition
the centre of gravity the boat will probably turn over more easily. The
centre of gravity can be repositioned by installing the batteries further to
the rear of the boat.
Multy-hulls can turn over. If, in a gust a bow starts diving you can
overcome this easily. Just turn the boat higher into the wind! As long as you do this, it
will reduce the chances of turning over of the boat.
If your boat suffers from stability problems you can install a keel. The additional weight will keep your boat upright. The disadvantage is
the additional resistance of the boat in the water. You might as well go
sailing with a mono-hull. Some people install additional weight in the boat; this will not make the boat more stable.
The solution is to install larger beams. If you install a longer beam the stability will rise and also the speed.
By having more distance between the hulls the waves created by the boat will come together futher away from the boat and therefore will give less.
resistance (more speed).
On the photo you can see the boat with the 78 cm new beams and the original 55cm beams.
If your cat can't make spead its often coust by the alignment of the rudders.