first layer were loaded across the trailer tightly against the bulkhead and 

 against the first box and each other box so that there remained at the end of 

 the layer a space between the last box and the trailer sidewall of a little 

 less than one-half the width of a box. The second layer of the first stack was 

 begun here with the first box resting partially over the space and partially on 

 the last box of the first layer. The succeeding boxes of the second layer were 

 placed tightly against the bulkhead and tightly against the first and each other 

 box in the line, each box resting almost equally on the two boxes in the layer 

 beneath, leaving a space at the end of the second layer of a little less than 

 half the width of a box. The succeeding odd-numbered layers were loaded the 

 same as the first layer and the succeeding even-numbered layers were loaded 

 the same as the second. The boxes in the second stack were loaded by the same 

 procedure except that loading of the second stack was commenced on the opposite 

 side of the trailer from where the first stack had been started. The third, 

 fifth, seventh, and other odd-numbered crosswise stacks were patterned after 

 the first crosswise stack and the fourth, sixth, eighth, and other even-numbered 

 stacks were constructed the same as the second crosswise stack. Under this 

 procedure the open spaces at the end of the layers in one stack were offset by 

 closed spaces (boxes) in the layers of the next stack because the loading of 

 adjacent stacks, as explained, was alternated and begun at opposite sides of 

 the trailer (fig. 8). 



In Tests 30, 31, 32, and 34 it was found that this stacking procedure had 

 considerably restricted the air circulation around and under these loads, or 

 in some instances had almost completely cut it off. Also, in Test 31 (fig. 9) 

 for example, the two rear stacks did not follow the crosswise offset principle 

 and were loaded too tightly across the trailer from one sidewall to the other 

 thus preventing any air circulation along the sidewalls. All four of the loads 

 arrived at destination with the bottom two layers of the rear stack tightly 

 against the rear doors further restricting the air circulation around the rear 

 of the load to the grooved floors for return flow to the refrigerating unit 

 intake at the front of the trailer. 



There were no vertical wall strips on the trailer sidewalls nor length- 

 wise air channels through the loads in these four tests, and spaces between 

 the rear of the loads and the rear doors had not been provided. As a result, 

 heat transmitted through the walls 'of the trailer passed directly into the 

 boxes as it penetrated the cargo area instead of being picked up by circulating 

 cold air and returned to the refrigeration coil for removal. Due to restricted 

 air circulation in the four test loads, some of the fruit in the boxes had 

 picked up as much as 15 degrees or more in temperature during transit. 



An attempt was made to increase the air flow in the load of Test 34 by 

 loading the last three stacks with the boxes in identical positions in each 

 stack to provide partial lengthwise air channels. However, as the preceding 

 stacks were not uniformly loaded to conform with the last three stacks, it 

 was not possible to have continuous air channels in the load from front to 

 rear, and air circulation was blocked. 



The entire load of Test 33 was loaded by the crosswise offset method 

 without lengthwise air channels but, unlike Tests 30, 31, 32, and 34, it had 

 a 12-inch space between the end of the load and the rear doors of the trailer. 



- 22 - 



