Simplified Stability

(46 CFR 178.310(a), 178.310(b), 179.212(c))


Information regarding simplified stability is coordinated by the Naval Architecture Division (CG-ENG-2).

Small passenger vessels inspected under 46 CFR Subchapter T must comply with the stability standards in Subchapter S, except where simplified alternative methods are permitted to assess the vessel's stability (see the CFR sections cited above).
These simplified methods can be used for a small passenger vessels that are:
  • Monohulls & sailing monohulls, non-sailing catamarans (but excluding pontoon vessels);
  • Not more than 65 feet in length;
  • Don't carry more than 12 passengers on an international voyage;
  • Don't have more than two decks available to passengers; and
  • Satisfy some additional criteria.

Each method involves physical measurement of certain physical dimensions and characteristics of the vessel, and placing weight(s) on board to simulate the total weight of all passengers, crew, and any other variable loads.

Simplified Stability Proof Test (SST)

A small passenger vessel (except a pontoon vessel) may undergo a simplified stability proof test (SST) as detailed in 46 CFR 178.330, provided that it satisfies the conditions set forth in §178.320 or §178.325.

To assess the vessel's stability, the SST requires that the weight(s) be moved a measured distance, in order to cause the vessel to heel.  The resulting change in freeboard is measured, and the test is satisfied if the freeboard change does not exceed the allowable amount.  (Note: if the freeboard change does exceed the allowable amount, the vessel's stability must be ascertained by other calculations or methods).

A job-aid with detailed instructions for conducting a simplified stability test, recording test data, and performing associated calculations, can be downloaded here (formerly designated Form CG-4006).

Pontoon Simplified Stability Proof Test (PSST)

[To be added]

Simplified Subdivision

[To be added]

Contact the Naval Architecture Division:

  • Commandant (CG-ENG-2)
    Attn: Naval Architecture Division
    U.S. Coast Guard Stop 7509
    2703 Martin Luther King Jr Ave S.E.
    Washington, D.C. 20593-7509
    (202) 372-1370