If you are a boat owner, you need to be aware of boat flotation. The US Coast Guard requires that all boats under 20 feet in length provide level flotation. Level flotation means that if the boat is swamped it will float level and upright, which means that the flotation product must be distributed symmetrically.
Subparts F, G, and H deal with flotation requirements. The document addresses the federal regulations for boat manufacturers and is intended to help them comply with marine flotation requirements. Recreational boats 20 feet and smaller are required to leave the manufacturer with foam flotation. However, there are no laws prohibiting owners from removing the flotation material.
From recreational boats to large transatlantic freighters, all of them must successfully go through rigorous buoyancy tests. This feature is achieved using elements that are lighter than water , such as air contained in an inflated balloon.
The feature of buoyancy is obtained by the effect that occurs between water and the hull of the boat. Due to the configuration of the ships, it is complicated and exaggerated to think of balloons inflated with air in the hull. Polyurethane is presented as a material that plays the role of these "inflated balloons": its weight is lighter than water and polyurethane foam is expanded in situ to suit the thickness of the hull of the boat.
The closed-cell polyurethane expanded in situ presents a high degree of adhesion to the inner surfaces of the hull. Thanks to this characteristic as well as to its structure, it welds the contour between the hull and the deck. The result obtained is a tailor-made sandwich panel that confers rigidity to the hull of the ship in the presence of waves. There are two types of polyurethane foam: closed-cell and open-cell. Why is closed-cell foam interesting for boats?
Density Flotation Foam Activator can expose you to chemicals including ethylene glycol, which is known to the State of California to cause birth defects or other reproductive harm. For more information, go to www.
Density: Available in 2 lb. Note : Continuous water submersion can eventually lead to loss of buoyancy over a period of years. Without additional treatment, this type of foam is attacked on contact by polyester resins, and its resistance to gasoline is poor. It can, however, be sealed with epoxy resins first, but this adds to the work and does drive up the cost substantially, perhaps making it more economical to consider a more expensive, but better suited foam in the first place.
Another consideration is that this type of foam is extremely flammable. However, there are special formulations that are solvent-resistant and self-extinguishing. An improved type of foam that is similar to foamed polystyrene is called styrene acrylonitrile. This foam has negligible water absorption and reasonable solvent resistance, but the styrene base would still make it incompatible with polyester resins.
T he most common type of plastic foam used for flotation purposes is the urethane type, available in blocks or sheets, or in "pour-in-place" kits. In production boatbuilding, boatbuilders use rather elaborate and costly foam-in-place machines not readily available to the amateur.
However, this same material is being used in many cases for home and building insulation, and it may be possible to contract with a firm that specializes in this process to install the foam directly into the boat if desired.
U rethane foams in sheets and blocks are easily cut and shaped before installation using ordinary woodworking tools, and readily glued in place with most glues. They are not attacked by resins and are resistant to gasoline and oil, which affect the foam only by a slight swelling after several hours of complete immersion when low density 1.
O lbs. However, this quality of the low-density variety does allow it to absorb large quantities of water over a long period of time. Because of this, the foam in low densities is not recommended for use below the waterline.
Therefore, for applications below the waterline, use urethane foams of 4. At this density there is also no discernible impact on the foam from hydrocarbon solvents such as gasoline or oil. While urethane foam is combustible, I have been told that it can be made self-extinguishing, so you might want to discuss this quality with your supplier. Both the sheet or block type, and the pour-in-place type have similar characteristics in the final form.
Both are quite friable and crumble easily, which causes a loss in bond and breakdown of the foam in high vibration situations such as those found in powerboats. I f using a pour-in-place type foam, these should be considered as VERY hazardous products when in use. Follow the label precautions and instructions to the letter. Experience shows that the volume of foam that results from one of these products can vary somewhat.
The rate of expansion also varies with ambient temperatures; the hotter it is, the faster the reaction and the more the foam tends to expand. Since most are a two-part concoction, they must be carefully and accurately mixed, and once mixed, there will be little time to get the product into the areas where it is wanted.
Mixing by hand is usually not complete enough nor quick enough; a power mixer such as a paint mixer attachment on a power drill is preferable. Do NOT apply the foam mix into restricted spaces except in several smaller pourings as opposed to a single batch, and allow about 20 minutes between batches.
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