TECHNICAL

In 1986 the National Office of the Army Corps of Engineering recommended to all district offices that the use of raw “white” foam be banned on all lakes throughout the country due to environmental concerns. There are numerous reasons for the ban of raw foam. The typical 4’ x 4’ x 1’ block of white foam weighs about 18 lbs. since most of the product is air. The displacement of this block will yield 960 lbs. of buoyancy. The problem lies in the air space within this block, which ultimately fills with water; after a period of time this 18 lb. block will weigh 200-250 lbs. with added water weight. The blocks also tend to break away and/or sink which compounds the problem. Algae forms at the water line and will be eaten by waterfowl. As birds peck away at the algae, they release thousands of tiny BB size pellets of foam onto the lake. These BB size pellets are non-biodegradable and will stay in the lake indefinitely eventually ringing the shore with a bathub ring of pellets. This is evidenced in small coves even today, some 20 years after the ban on the installation of new raw foam material. These white pellets are also mistaken by fish and waterfowl for eggs, which are eaten, plugging the digestive system and leading to premature death.

Many people refer to these floats as “styrofoam,” which is a misnomer since Styrofoam is a brand name of Dow Chemical which also made “treated” foam floats that are the forerunner of today’s encapsulated floats. A more correct name is Expanded Polystyrene or EPS, the same material you find today in insulation, packing material and packaging such as fast food hamburger containers. EPS was and is manufactured by numerous firms including the former Starr plant in Iva, SC.

Today’s “black” floats are foam which is encapsulated in a polyethylene shell. The floats, which could otherwise float like a ball, are filled with foam so they will continue to float even if punctured. There are several methods to produce these floats. Probably the least expensive method is a blow-molding process where a thick sheet is pushed into shape. The negative of this process is that you have stretched the plastic molecules, weakening the shell product. A blow- molded container is stuffed with a block of foam and then the lid is sealed to the top with vents on the side to permit gas to escape when it expands or contracts. Almost all float manufacturers in the market today use a vent hole. The problem with vent-holed floats is that water can eventually seep into the float making it sink faster than a raw foam float. In blow-molded floats the seal on the lid has also been known to break or crack, permitting water to enter the float.

Another process involves a thermoforming technique which stretches polyethylene over a block of foam and seals at a seam. Although this may offer the same negatives as a blow-molded float, it has another potential problem. Since these floats are formed without a bolting flange, the only way to fasten this float is to band it to the dock (not desirable since it can break loose and float away) or to punch a lag screw through the top of the float. We ask, “Why punch a hole in a watertight container?”

The manufacturing method which yields the strongest float is rotational molding, also known as “roto molding.” In this process, a hollow steel mold is filled with pellets of polyethylene and placed in an oven where it is heated and rotated. The plastic pellets melt and stick to the inside surface of the heated mold. An advantage of this process is that the liquefied pellets layer more heavily in the corners and edges providing additional strength where it is needed most. Additionally, a heavy bolting flange is formed as an integral part of the float during the molding process; this flange enables the float to be bolted directly to the frame of the dock. The roto-molding process yields a solid container; holes are bored into the top of the float, 80% pre-expanded polystyrene is pumped into the float, steam wands are inserted to expand the polystyrene to completely fill the container and then the holes are plugged with a spin weld cap. And, yes, there is a vent hole in the top of a well-designed roto-molded float into which a threaded plug is inserted once it is bolted to the dock.