Positively Buoyant Triton

James Baldwin, #384, Atom

I noticed the recent discussion regarding Atom's buoyancy and thought I'd clear up a few points. While speeding across countless miles of ocean during the past 23 years I had plenty of time to worry about being holed by a collision. Over the years I gradually modified most of the storage lockers into watertight lockers so that if the boat was holed in any of those areas the flooding would be contained. I was not particularly seeking positive buoyancy.

The main watertight lockers are:
1. Chain locker with two gasketed doors and shut-off valve drain.
2. Entire V-berth is filled in and raised 5 inches and its 5 independent lockers are sealed to the hull down to the bilge.
3. The forward watertank is integral to the hull.
4. The clothes locker face is raised to 10 inches above the waterline.
5. The toilet is behind a watertight bulkhead 3 inches above the waterline.
6. The forward bilge is isolated and sealed with gasketed hatch.
7. Lockers under main cabin bunks are divided into two each side with gasketed hatches.
8. Lockers under sink and galley are sealed to hull and have gasketed hatch access.
9. The ex-icebox locker is sealed to hull with a gasketed front hatch and the open is 10 inches above the waterline.
10. Watertank under cockpit floor is integral to the hull.
11. The three enormous cockpit lockers are independently sealed with shut-off valves in drains.
12. In addition, the door between the main cabin and the forward cabin is sealed with rubber gasket and three latches.

Once I had these lockers in place I wondered if I had incidentally achieved positive buoyancy on a boat with an estimated gross displacement of 9,700 lbs. By making estimates of the amounts of fiberglass, lead, anchors and chains, other metals, wood, foam deck core, tools and miscellaneous gear and calculating their respective buoyancy factors, I came up with a figure of 86.5 cu ft of watertight locker volume needed to float the boat with decks awash. (Imagine cutting up a foam block of 10-foot by 9-foot by 1-foot thick and placing the pieces throughout the boat). I then calculated that my watertight lockers which have gasketed seals have an approximate volume of 95 cu ft. I have not included partial watertight bulkheads unsealed at the tops which might be flooded over or the watertanks and the numerous watercans because they just might be full of fresh water. Closed cell cushions well strapped down would be another significant source of buoyancy.

I'm guessing Atom would float briefly even if she were holed in one of the few remaining areas of the hull which are not contained by watertight lockers. I say briefly, because I cannot be sure how fast the water will leak past the gaskets into the lockers. So, does Atom have temporary positive buoyancy? Possibly. Is she less likely to sink in most flooding situations because of her extensive watertight compartments? Absolutely! Do I sail with less anxiety when plowing through the seas at 6 knots in mid-ocean? You bet. Should you consider making some of your lockers watertight? That's up to you.

For more on Atom's watertight lockers go to: http://www.sailnet.com/collections/articles/index.cfm?articleid=baldwi0014