Abrasion resistance is important in both the fence material and the 

 float material if the latter is exposed. If the flotation is encased, 

 the abrasion resistance applies to the casing material. 



The abrasion resistance of material can be measured using the FTMS 

 191 Method 5304 which determines the change in breaking strength of the 

 material after subjecting it to unidirectional rubbing action under 

 controlled conditions of pressure, tension, and abrasion. A material, 

 after being tested by this method and in accordance with MIL-B-28617B 

 (YD), must have a breaking strength of at least 270 pounds per inch of 

 width to be acceptable as boom material. 



Flexibility. The material must have sufficient flexibility to 

 permit it to conform to the waves without loss of freeboard or draft. 

 Under certain wave conditions the rigidity of the boom may cause it to 

 bridge; that is, a portion of the boom will be suspended across the 

 trough of the waves from crest to crest so that the bottom portion of 

 the boom is actually out of the water. This complete loss of barrier 

 draft represents failure of the boom because eventually all oil would 

 escape. The boom must therefore be able to articulate with the waves so 

 that the fence maintains sufficient draft to prevent the oil loss. 



Depending on the design of the boom, a certain amount of rigidity 

 in the material is required (for instance, for a fence- type boom to 

 maintain its freeboard or draft against wind and currents as well as 

 waves). Stiff eners are often used with flexible materials to increase 

 rigidity in the vertical direction. Other methods for maintaining draft 

 with flexible materials include the use of bottom and top tensioning 

 cable and ballast weights attached to the bottom portion of the boom. 

 Flexible joints are often used in boom designs utilizing rigid materials. 



Flexibility is also required for boom storage and handling. The 

 material must be capable of being bent or folded in a relatively small 

 radius for prolonged periods without cracking, breaking, or taking a 

 permanent set. 



Flotation material as well as fence material must be flexible in 

 many boom designs, especially those utilizing continuous rod or log-type 

 foam floats. 



Although standard test methods exist for measuring the directional 

 flex-stiffness of cloth, such as FTMS 191 Methods 5200 and 5204, the 

 flexibility of the material is not one of the parameters currently 

 identified in MIL-B-26617B (YD). The flexibility of the entire boom is 

 visually observed, however, under operational conditions to verify the 

 boom's ability to conform to the water surface. Because of the impact 

 the boom design has on the degree of flexibility required in a material, 

 it is not possible to establish flexibility criteria as was done with 

 breaking strength and other parameters. So, although flexibility is a 

 definite consideration, it is not advisable to quantify it unless a 

 specific boom design is being addressed. 



