Issuma Centerboard (Lifting Keel)

Centerboard, labeled    

Unlike most sailboats, all ballast in Issuma is in the centerboard--there is no internal ballast, nor a ballasted keel--just the ballasted centerboard. I call it a ballasted centerboard, but it could also be called a lifting keel.

The ballasted centerboard is great for an expedition boat--it allows motoring (not sailing) into shallow areas, and, if stuck in ice, raising the centerboard leaves less for the ice to grab the boat with, making it more likely to pop up rather than be crushed. But one absolutely must always remember to put the centerboard all the way down and the locking pin in before setting sail. Otherwise, there is the danger of a gust of wind heeling the boat far enough over that the centerboard pivots up and the boat capsizes.

The centerboard trunk goes all the way to the deck (it is covered by a piece of plywood when the keel is down)

Centerboard trunk, looking down
It is just possible to squeeze into the centerboard trunk

The centerboard has 4.5 tons of ballast and also serves as a 700 litre fuel tank. So it has hoses for fill, vent and supply coming from it.

Looking down into the centerboard trunk with hold-down brackets removed: Centerboard trunk, looking down, forward end, labeled



On either side, hold-down brackets hold the centerboard pivot pin down (this is to hold the centerboard in the trunk). Four 3/4" stainless steel bolts hold down a small bracket on top of the hold-down bracket. The hold-down bracket is prevented from twisting out of place by one 3/4" stainless steel bolt. The channels in the centerboard trunk that the brackets slide down also prevent the brackets from twisting out.


Centerboard hold-down brackets, labeled, laid out
The threaded rod in the picture is for adjsting how tight the hold-down bracket is (unless there is a lot of wear, one would only adjust this when first installing the board).


Inside the boat

Before sailing, the centerboard must be locked down. There are four (reinforced) holes in the centerboard trunk for the locking pin. I know the lowest pin hole is the position that is safe for sailing. I do not know specifically what each of the other positions are for--I use them for motoring, or when at anchor in shallow water.


Inside the boat, besides the four holes for the pins, there are horizontal pads, two per side. The horizontal pads are screwed (there is a special tool for this) in when the centerboard is down and locked. They prevent the back of the centerboard from slopping around in the centerboard trunk in waves. Properly adjusted, the centerboard does not make any noises in waves.


Centerboard pin, in hole, shown from inside cabin


Not shown in the pictures, but to make it as plain as possible to know that the centerboard pin is in or out, when out, it is stored in front of a white-painted area, in plain view of the cockpit.

Lowering the centerboard for sailing:

The centerboard must be down and locked before sailing. The procedure for lowering it is:
  • Assuming horizontal pads are backed off, so centerboard can be lowered, lower centerboard most of the way.
  • Remove the cap on the hole in the centerboard trunk. Now you can see where the hole in the centerboard is relative to the hole in the centerboard trunk, so can lower the centerboard until the holes align.
  • Insert the locking pin into the hole in the centerboard trunk, and thru the centerboard to the other side of the centerboard trunk.
  • Lower the centerboard a bit more to put some load on the locking pin, to help ensure it can't slide around.
  • Put the cap on the hole in the centerboard trunk.
  • Tighten the four horizontal pads that prevent the aft end of the centerboard from slopping around in waves.


Raising the centerboard:

To get into shallow areas, one can raise the centerboard. The boat can be motored with the centerboard raised, or partly raised, but it should not be sailed, because the ballast is not low enough. The motion of the boat will be different with the centerboard raised, because the center of gravity will be higher. So motoring in beam seas should be avoided.

To raise the centerboard:
  • Loosen the horizontal pads that prevent the centerboard from slopping around in the centerboard trunk.
  • Remove the cap on the locking pin hole in the centerboard trunk.
  • Slightly raise the centerboard until the locking pin can be freely removed.
  • Remove the locking pin and replace the cap on the locking pin hole.
  • Raise the centerboard as far as desired.
If you forget to remove the locking pin before raising the centerboard, the cable will break, and you will need to replace the cable before you can raise the centerboard. The cable is common 10mm or 3/8" galvanized steel cable, available in any city.


Removing/Installing the centerboard

I've removed the centerboard once (so far) for inspection (it was fine, no signs of wear). Issuma was tied between two barges when the centerboard was removed. I did it this way to ensure no winds could heel her over when her centerboard (and therefore all ballast) was removed.
Lifting the centerboard out of the boat, pic from on deck
Lifting centerboard out of boat, pic from beside boat
Lowering centerboard into trunk, pic from beside boat

More about inspecting the centerboard at this blog entry,Inspecting the Centerboard



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