|
An Automatic Daggerboard |
|
Revering to Mr Szudy`s
article about dagger
boards. They can be a necessary nuisance.
But are also helpful sailing to windward. As you will
know I am a multihull person. Good ability to sail
to windwards is for this type of boats even more important.
Because fast multihulls sail for about 60% of the
time to windwards (apparent wind). I found for some
hull cross section, with my anti-vortex panels, a
simple solution.
A-symmetrical hulls
need no boards at all. My catamaran designs up to
9m (27ft) have daggerboard rudders with an automatic
kick up system. When an obstacle is hit (also logs),
the rudder is pulled out of the slot and the bungee
cord pulls the rudder up. To get the rudder down again
you push the rudder down till it jumps in the slot
again.
We have used this rudder system now for 22 years without
problems on different multi hulls.
Dagger board rudder on a DUO
425 beach catamaran.
Rudder in up position.
The system can be also adapted for daggerboards.
(See sketch below - This is a dimensionless drawing
to explain the function.) The dagger board case has
to be angled on the front, so that the dagger board
can slip out of the key. So when an obstacle is hit
the PVC tube will be bent and the dagger board turns
forward. At this moment the slot in the board falls
out of the key and the bungee cord pulls the board
up.
To have the board working again push
it down till the key falls in the slot again. The
bungee cord is fastened to the dagger board case with
clamps. The PVC tube (for small boats a tube like
that used for electric wiring will suffice) is very
important. The tube holds the board back in the dagger
board case and in this way the board in the slot under
normal sailing conditions.
The length and diameter of the bungee
cord has to be found out for every boat. If the dagger
board case is short the leverage of the cord can be
improved by leading the cord backwards. Use sheaves
on each side in this case.
https://www.ikarus342000.com/P86page2.htm
|
