Flooding Cabin Sump on REVENGE in Bad Weather to Improve Stability

A conversation among Whalers
floater
Posts: 173
Joined: Sat Oct 24, 2015 3:55 pm

Flooding Cabin Sump on REVENGE in Bad Weather to Improve Stability

Postby floater » Mon Jul 19, 2021 8:40 am

When the weather really kicks up my 1988 Revenge 20 W-T starts getting tossed around like a cork. I thought maybe I could pull the plug in the front sump and let the cuddy flood with water to help stabilize the boat. I've been out before with the cork pulled and the water didn't even make it to the top of the step so I don't think it would fill the boat.

Will [flooding sump areas with water] help [reduce the tendency for the boat to be tossed around like a cork]?

ASIDE: On July 18, 2021, I was on Lake Ontario. The seas were six-foot to seven-foot swells until noon. I've never experienced this before.

jimh
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Location: Michigan, Lower Peninsula
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Re: Flooding Cabin Sump on REVENGE in Bad Weather to Improve Stability

Postby jimh » Mon Jul 19, 2021 8:46 am

Generally the worst possible condition to have on a boat during stormy seas is to have free water in the boat that can move in response to changes in trim. See:

https://en.wikipedia.org/wiki/Free_surface_effect

Generally best pitching stability in a boat is obtained by keeping weight out of the ends of the hull.

The hydrodynamic stability of a hull is a complicated topic, and hull interaction with waves an even more complex topic.

If making boats heavier made them more stable and safter, you would expect that all boats would contain large amounts of fixed ballast weights in the most advantageous areas.

dtmackey
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Joined: Thu Sep 28, 2017 9:29 pm

Re: Flooding Cabin Sump on REVENGE in Bad Weather to Improve Stability

Postby dtmackey » Mon Jul 19, 2021 10:40 am

When I was in the Coast Guard aboard a 180 buoy tender, we were traveled from Norfolk (Virginia) to Portland (Maine) in the March storm of 1987. We were out there in 25-feet-high sea, and were called to divert to a Russian freighter than was sinking off New Jersey. The change in course put us in a percarious track, and we managed to record one roll where our cutter went two or three-degrees beyond designed roll-righting-specification from the original specifications when the ship was built.

Our cutter was fitted to serve as a buoy tender off the coast of Maine and refuel lighthouses, so in the bowels of the ship, massive tanks were installed to carry tens of thousands of gallons of fuel. Lucky for us, our commanding officer made the decision to ballast those tanks before we left for Maine, knowing we would encounter the storm.

So what is my point? Extra weight carried in the lowest location of a vessel (below the waterline) can have a dramatic impact on the handling, BUT only if the fluid is contained and unable to slosh around. Sloshing fluid can actually increase the ability of a boat or ship to rock or roll in heavy seas and is an big no-no. In a planing hull, like a Whaler, any tankage would not be deep enough below the waterline to have the desired stability you seek.

The Russian freighter did sink in that storm and the crew was rescued by helicopter off the coast of NJ. While we were within distance to respond, there was nothing we could have done in those seas, not to mention our speed over ground was about two-nautical-miles-per-hour in those conditions and would have taken us too long to arrive on scene. Our slow speed was also due to one main diesel being ouf of commission due to a previous grounding on Moutlon Ledge off of Bar Harbor. That grounding caused damage to the hull side bottom so bad that it bent the crankshaft in one of the Cooper-Bessemer GND-8 main diesels. Luckily we were twin diesel electric driving one screw.

D-

floater
Posts: 173
Joined: Sat Oct 24, 2015 3:55 pm

Re: Flooding Cabin Sump on REVENGE in Bad Weather to Improve Stability

Postby floater » Tue Jul 20, 2021 8:03 am

Great replies. I will scratch that idea and just watch the weather!