BOATBUILDER'S HANDBOOK

Flotation - Flotation Materials

There are specific performance specifications for flotation materials based upon their location in a boat. The level of performance required depends on the degree of exposure to detrimental agents. Each section of the federal regulation related to a specific type of flotation, i.e., Basic, Level, or Modified Level, provides requirements addressing flotation material. The requirements refer the reader to Sec. 183.114 which follows.

The terms "bilge", "engine room bilge" and "engine room" have been defined (see section 2.0). The first step will be to establish the bilge and engine room bilge areas within the boat.

With the unloaded boat in calm, fresh water and transversely level (static floating position):

  • The bilge is the volume located below a line parallel to the reference waterline. This line is located 4" up from the lowest point where water may accumulate in the boat.
  • The engine room bilge is the volume located below a line parallel to the reference waterline. This line is located 12" up from the point where water may accumulate within this compartment (or connected compartments)

FIGURE - 7.1

FIGURE 7.2 - Boat in Static Floating Position
 

Flotation Material Requirements

Basic Flotation Material Requirements

FEDERAL LAW

183.112 - Flotation material and air chambers

(a) Flotation materials must meet the requirements in Sec. 183.114 as listed in Table 183.114 when used in the: (1) Engine room bilge, (2) engine room, or (3) bilge, unless located in a sealed compartment.

(b) Air chambers used to meet the flotation requirements of this subpart must not be integral with the hull.


Level Flotation Material Requirements

FEDERAL LAW

183.222 - Flotation material and air chambers

(a) Flotation materials must meet the requirements in Sec. 183.114 as listed in Table 183.114 when used in the bilge, unless located in a sealed compartment.

(b) Air chambers used to meet the flotation requirements of this subpart must not be integral with the hull.


Modified Level Flotation Material Requirements

FEDERAL LAW

183.322 - Flotation materials

(a) Flotation materials must meet the requirements in Sec. 183.114 as listed in Table 183.114 when used in the bilge, unless located in a sealed compartment.



Flotation Material Tests

FEDERAL LAW

183.114 Test of flotation materials.

(a) Vapor test. The flotation material must not reduce in buoyant force more than 5 percent after being immersed in a fully saturated gasoline vapor atmosphere for 30 days at a minimum temperature of 38 deg. C.

(b) 24-hour gasoline test. The flotation material must not reduce in buoyant force more than 5 percent after being immersed for 24 hours at 23 plus or minus 2 deg.C in reference fuel B, of ASTM D 471 (incorporated by reference, see Sec. 183.5).

(c) 30-day gasoline test. The flotation material must not reduce in buoyant force more than 5 percent after being immersed for 30 days at 23 plus or minus 2 deg.C in reference fuel B, of ASTM D 471 (incorporated by reference, see Sec. 183.5).

(d) 24-hour oil test. The flotation material must not reduce in buoyant force more than 5 percent after being immersed for 24 hours at 23 plus or minus 2 deg.C in reference oil No. 2, of ASTM D 471 (incorporated by reference, see Sec. 183.5).

(e) 30-day oil test. The flotation material must not reduce in buoyant force more than 5 percent after being immersed for 30 days at 23 plus or minus 2 deg.C in reference oil No. 2, of ASTM D 471 (incorporated by reference, see Sec. 183.5).

(f) 24-hour bilge cleaner test. The flotation material must not reduce in buoyant force more than 5 percent after being immersed for 24 hours at 23 plus or minus 2 deg.C in a 5-percent solution of trisodium phosphate in water.

(g) 30-day bilge cleaner test. The flotation material must not reduce in buoyant force more than 5 percent after being immersed for 30 days at 23 plus or minus 2 deg.C in a 5-percent solution of trisodium phosphate in water.

(h) The buoyant force reduction in paragraphs (a) through (g) of this section is measured in accordance with ASTM D 2842 (incorporated by reference, see Sec. 183.5).


Table 183.114 - Flotation Performance Tests

NOTES:

  1. The change in volume and buoyancy is measured in accordance with ASTM D-2842. The maxi mum size of a test sample shall be 6" x 6" x 3" and cut by the same method used to shape it for use in the boat.
  2. Flotation material does not have to be gasoline, oil, gasoline vapor or trisodium solution-resistant if:
  3. a. Used in manually propelled boats;

    b. Installed outside the engine compartment more than 4 inches above the lowest point where liquid can collect when the boat is in its static floating position; or

    c. Enclosed or encased in an enclosure that permits no more than one-quarter ounce of fresh water per hour to enter when the enclosure is submerged to a depth of 12 inches.

  4. Cellular plastic used to encase fuel tanks is allowed to count as a flotation material, but it must conform to the following applicable conditions (33 CFR 183.516 of the USCG Fuels Systems regulations):
  5. For the purposes of these tests, ASTM oils and ASTM fuels, and a trisodium phosphate solution have been selected which approximate typical marine products with which flotation material may come in contact in actual service.
  6. ASTM reference fuel B provides typical swelling effects produced by commercial gasolines, and ASTM No. 2 reference oil has been chosen since it characterizes the nearest aniline point of a petroleum- based oil used in marine service. The aniline point of petroleum oil determines the swelling action of the oil. Reference fuel B consists of 70% Isooctane and 30% Toluene, in volume (Isooctane conforming to Section Annex A2.8, Motor Fuels Section of 1973-74 ASTM Manual for Rating Motor, Diesel and Aviation Fuels; Toluene conforming to ASTM D-362 for Industrial Grade Toluene).
  7. For a full explanation of the test fuels, refer to ASTM D-471.

FEDERAL LAW

183.516 - Cellular plastic used to encase fuel tanks

(a) Cellular plastic used to encase metallic fuel tanks must:

(1) Not change volume by more than five percent or dissolve after being immersed in any of the following liquids for 24 hours at 29 deg.C:

(i) Reference fuel B ASTM D 471 (incorporated by reference, see Sec. 183.5).

(ii) No. 2 reference oil of ASTM D 471 (incorporated by reference, see Sec. 183.5).

(iii) Five percent solution of trisodium phosphate in water; and

(2) Not absorb more than 0.12 pound of water per square foot of cut surface, measured under Military Specification MIL P-21929B.

(b) Non-polyurethane cellular plastic used to encase metallic fuel tanks must have a compressive strength of at least 60 pounds per square inch at ten percent deflection measured under ASTM D 1621 (incorporated by reference, see Sec. 183.5), "Compressive Strength of Rigid Cellular Plastics".

(c) Polyurethane cellular plastic used to encase metallic fuel tanks must have a density of at least 2.0 pounds per cubic foot, measured under ASTM D 1622 (incorporated by reference, see Sec. 183.5), "Apparent Density of Rigid Cellular Plastics."


NOTE:

If cellular plastic was used to encase a fuel tank and is counted as flotation material, it must meet the above stated requirements.

Of the many foams available, foamed polystyrene and polyurethane are the most common. They are noted here because of their broad use, but not to the exclusion of other types of flotation material.

Foamed polystyrene is a low-cost material produced from expandable beads ("pop corn") or extruded in the form of billets or boards. The common name is "Styrofoam." In its common forms, it is readily dissolved in gasoline and is highly flammable. There are special compounds of polystyrene foam that are solvent-resistant and self-extinguishing. One objection to foamed polystyrene is that it cannot be foamed in place, and it usually cannot be produced in a boat builder's plant. Caution is necessary because some varieties have "wormholes" which reduce the flotation value.

Polyurethane foam is another widely used buoyancy material. It is usually foamed in place or molded into specific shapes before installation. It is also available in slabs and billets. Polyurethane foam is normally highly resistant to gasoline and oil, particularly in densities of 4.0 pounds per cubic foot and higher. Even in densities of 1.5 to 2 pounds per cubic foot, it is considered very resistant to gasoline and oil. Polyurethane foam is flammable, but it can be made self-extinguishing. In densities of less than 2 pounds per cubic foot, it may absorb significant amounts of water.

Air chambers used to achieve flotation are usually made of plastic materials. They must be capable of withstanding the same solvent-resistance tests as other flotation materials, and they must pass the required 18-hour submergence preconditioning before undergoing the flotation tests.
 

Flotation Material Installation Requirements

a) Air Chambers

Air chambers shall maintain their integrity under pre-test conditioning and under flotation test conditions. They shall not leak when subjected to an internal air pressure test and shall not allow the ingress of water when submerged to at least a depth equal to that required in the flotation test.

b) Plastic Foam Blocks and Other Shapes

1) A method of identifying foam blocks and other shapes must be employed to assure that each boat gets the correct amount of flotation in the correct location.

2) Expanded polystyrene foam must not come in contact with uncured polyester resin or fumes.

3) Foam blocks and other shapes must be secured so that no movement in any direction occurs that will effect the flotation's performance.

4) Installation must be in a manner that will prevent:

  • damage from occupant contact
  • deterioration from exposure to direct sunlight
  • damage from normal use of the boat.

5) The space provided for the installation of foam blocks must be large enough to prevent the necessity of using force that will deform the shape of the block during the installation process. Deformation will lower the volume, and therefore the total buoyancy, of the foam block.

c) Sprayed or Poured Liquid Mix

1) When liquid flotation material is installed directly in place, constraints must be provided in the form of bulkheads, boxes or dams to ensure the proper volume, and to ensure that the centers of buoyancy are correctly placed.

2) Clearance around, and passages through, the foam should be provided for:

  • routing controls, cables and wires;
  • access to windshield fasteners, cleat and chock fasteners, rail
    fasteners, ventilation ducts, other deck hardware and standard fittings;
  • bilge drainage;
  • drainage of the top of metallic fuel tanks (See Fuel Systems Compliance Guideline).

FIGURE - 7.3

FIGURE - 7.4

FIGURE 7.5 - Flotation Material — Protection from Damage

FIGURE 7.6 - Flotation Material — Protection from Damage

 

Previous  |  Next

RESOURCES

Media and Marketing Materials

Members of the press, boating safety specialists and advocates, and the general public are invited to utilize any and all of the media and marketing materials in this section.

 

Photo Library

The U.S. Coast Guard has provided the Image Library as a resource tool for boating safety specialists, advocates and the general public.

 

Video Library

The U.S. Coast Guard has provided the Video Library as a resource tool for boating safety specialists, advocates and the general public.

QUICK LINKS

 

 


 
 
 
 
 
   safe a float