1. Collision Damage (0.0/0.2) . A tire mat properly coupled is a highly 

 resilient and strong structure. Due to its inherent flexibility, an FTB is 

 unlikely to significantly damage a boat during a collision. Likewise, it is 

 highly improbable that most boats could significantly hurt an FTB. There are 

 two known instances of boats colliding with an FTB. In the first case, during 

 a severe storm at night, a small occupied sailboat making for a harbor of ref- 

 uge ran atop the FTB. The only damage which resulted was a bent propeller 

 shaft. In the second case, a reckless and alleged drunken boater rammed his 

 power cruiser against an FTB. The only damage which resulted was black tire 

 marks on the boat's white hull. In both instances, witnesses claim that the 

 FTBs probably saved boaters' lives--in the first case, the occupants of the 

 sailboat; in the second case, people onboard their boats within the protected 

 marina. 



To circumvent collision problems, some FTBs are marked with fluorescent 

 cones and others on freshwater have flashing lights installed. Several opera- 

 tors felt that this latter requirement, posed by the Coast Guard in certain 

 inland waterways, was unnecessary and needlessly expensive. 



2. Effectiveness in Suppressing Waves . 



On a scale of zero (i.e., ineffective) to four (i.e., excellent), the 

 operators gave the Goodyear design an average effectiveness rating of 2.8, a 

 high level of performance. More than 80 percent of the users indicated that 

 the FTB reduced storm wave heights by 50 percent or more. While the values 

 assigned to this physical reduction of wave height may be suspect, the overall 

 satisfaction of the operators with their FTBs' capabilities is not. 



One of the indicators of an FTB's likely effectiveness in reducing wave 

 height is the ratio of the structure's beam to the length of an incident wave. 

 In theory and as borne out in model tests, as this ratio increases (i.e., as 

 the FTB spans more and more of the wavelength), the effectiveness of the struc- 

 ture likewise improves. To determine if this trend was substantiated by field 

 experiences, MRM plotted the reported transmission coefficients versus the 

 beam to estimated wavelength ratios (see Fig. 2). While there is considerable 

 scatter in the points, the trend is clear as illustrated by a line fitted by 

 the least squares method. This trend agrees with theory. Generally speaking, 

 those FTBs which were most successful were located at sites with reported con- 

 ditions such that the FTB's beam equaled or exceeded 60 percent of the length 

 of a typical storm wave (see Harms, 1979) 2 . 



3. Cost and Additional Benefits . 



The cost of a Goodyear FTB can vary substantially from site to site, de- 

 pending on the coupling material used, the reserve flotation provided, the 

 anchoring-mooring system deployed, and the labor available. However, based on 

 the data, some indications of relative cost per square meter (and per square 

 foot) of surface area are possible by separately examining saltwater and fresh- 

 water sites. For projects located in saltwater, total construction and instal- 

 lation costs varied from $9.59/m 2 ($0.89/ft 2 ) to $44.50/m 2 ($4.13/ft 2 ) with an 



HARMS, V.W., "Data and Procedures for the Design of Floating Tire Break- 

 waters," New York Sea Grant Program, Albany, N.Y., 1979. 



15 



