Jouy-en-Josas, September 27, 1999
The draft of a boat
-A short draft is easier for mooring.
-A long draft makes the boat safer, faster.
It is necessary to find for every user the best balance, but every
solution has its limits.
Increase the draft :
| Decrease the volume of the ballast near the hull |
the boat is more stable reaching |
| Lower the centre of gravity |
|
| Give a better center board area |
tacking the boat hauls up better |
|
|
|
|
Decrease the draft,
the qualities of the boat decrease gradually and degrade brutally
when the wind increases, heeling is coming and the waves increase. According to the size
of the boat and with certain force of wind and waves, the boat becomes incompetent
to haul up , to handle ; it becomes dangerous.
It is imperative not to build or to buy boats under a draft minimum.
Examples :
Fig 1 : hauling up is function of the draft
Fig 2 : draft is function of the type of boat and of the size
It is more simple to have a fixed ballast, but there is a limit below
which we must not cut down the draft .
To escape the fixed ballast and decrease the draft , there are other
solutions :
The ballasted centreboarder
A centre of gravity is kept enough low with weight of ballast increased.
Performances are still acceptable because of the drift
But using and maintenance of the boat are more delicate.
The lifting keel boat
a low centre of gravity and a good drift area
- a keel like a centreboard allows well to absorb the shocks.
- a lifting keel gives a centre of gravity very low.
These two solutions are even more difficult to build and to maintain
than the ballasted centreboarder and the keel boat..
Double keel
Util now, the performances.of these boats are not very good
At present, we try to improve and to confirm this type of appendixes. |
