Jonathan W. wrote:
We had occasion two weekends ago to reconsider the matter of removing
large amounts of water from a boat in a hurry. This event caused by
crossing inside of the green day mark #3 marking the Middle Ground ledge
in Woods Hole, MA.
While the events leading up to this are still being debated among those
onboard, part of the problem appeared to be a fixation on the part of
the skipper/helmsman with electronic charting over the real world. If
the course had been adjusted when the alarm had first been raised,(by
humans) or the second or third time, there would have been no incident
to reflect on.
Driving a 20,000 lb, 38 foot sloop drawing about 6 feet over a ledge
with 3 or 4 feet of water over it is an experience I would not wish to
repeat. The full keel and skeg hung rudder took the brunt of the impact
and the bottom of the ruder skeg with it's gudgeon were left on the
ledge (presumably).
The rudder dropped straight down and the now two extra feet of leverage
given overcame the strength of the interface between the rudder's
stuffing box and the hull, ripping open a 2-3 inch hole, depending on
where the rudder/shaft assembly was leaning at any given moment.
The two 2500 GPH bilge pumps were immediately overwhelmed. It is a
sobering sight to see salt water rising inexorably toward the air intake
on a diesel engine. In the confusion, I could not decipher which hose was
the raw water intake to add the engine cooling capacity to the bilge
pumping (and I did not wish to risk my hands in the belts of the dual
alternators). During this, others managed to leverage the rudder
quadrant/shaft into the upright position, mostly closing the hole, and
slowing the ingress of water to a point where the pumps could almost
hold their own. The arrival of a local fisherman in response to the
radio call was comforting, in that a tow line kept us from additional
impact with other natural hard spots in the passage.
The Coast Guard 41 footer has impressive dewatering capabilities in both
portable and built in pumps. We only needed the portable gas pump to
establish equilibrium. It was a long 30 minutes until they arrived from
their training mission off of Edgartown, however.
Once we were dewatered, and all the floorboard hatches were put back in
place (they tend to float off at some point) TowBoat US took over. While
our pumps were mostly capable of holding us while we were under tow to a
boat yard, they had put aboard two of these:
http://www.starmarinedepot.com/detai...duct_id=RU1416
You have to look a little harder to find these to purchase, than the
2500 gph, but I think one will be high on my list of must haves for the
coming years. It is interesting to look at the loss due to "lift" and
voltage, even this powerful appearing pump actually has. 6 foot lift
would not be uncommon in a boat that has standing headroom in the cabin.
Between lift and the voltage drop to 12v vs 13.5 when an engine is
running, even this pumps capacity gets reduced by about 30%
Just thought I'd share.
Jonathan
Interesting point. I built a "golf club" bilge pump, so I can empty
the dinghy without getting into it. It has a small battery pack
from a bag phone, and I though to improve it's operation my adding a
flexible tail long enough to drop in the water whilst in use. The
effect on pumping capacity was remarkable. The "down" side of the
hose helps with a syphon effect to reduce the workload on the tiny
bilge pump at the end of the stiff pipe handle. Now, the only work
the pump does is effectively to move the water sideways, not up.
All bilge pumps would benefit from this configuration, but
permanently fixed bilge pumps so arranged must include a vented
loop, defeating the syphon assist, it seems, and, I might add,
rightly so, unless diligently supervised. So much for safety
regulations.
Your pump would be more efficient if it has a tail down to the water
to be used only while actually trying not to sink. Unattended pumps
must not offer any possibility of syphoning water into the boat.
Terry K