<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
       
<S>                             <C>                     <C>                     <C>                     <C>
<PERIOD-TYPE>                   3-MOS                   3-MOS                   6-MOS                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-1998             DEC-31-1997             DEC-31-1998             DEC-31-1997
<PERIOD-START>                             APR-01-1998             APR-01-1997             JAN-01-1998             JAN-01-1997
<PERIOD-END>                               JUN-30-1998             JUN-30-1997             MAR-31-1998             MAR-31-1997
<CASH>                                         335,348                 264,247                       0                       0
<SECURITIES>                                         0                       0                       0                       0
<RECEIVABLES>                                3,405,296               3,558,557                       0                       0
<ALLOWANCES>                                         0                       0                       0                       0
<INVENTORY>                                  2,988,200               3,024,597                       0                       0
<CURRENT-ASSETS>                             6,847,268               6,935,442                       0                       0
<PP&E>                                      17,479,396              17,234,988                       0                       0
<DEPRECIATION>                               5,718,885               5,205,058                       0                       0
<TOTAL-ASSETS>                              21,376,682              21,798,022                       0                       0
<CURRENT-LIABILITIES>                        7,174,369               7,333,308                       0                       0
<BONDS>                                      4,377,798               4,732,167                       0                       0
<PREFERRED-MANDATORY>                                0                       0                       0                       0
<PREFERRED>                                          0                       0                       0                       0
<COMMON>                                             0                       0                       0                       0
<OTHER-SE>                                   9,824,515               9,732,547                       0                       0
<TOTAL-LIABILITY-AND-EQUITY>                21,376,682              21,798,022                       0                       0
<SALES>                                     16,213,769              18,061,461              32,097,679              33,006,101
<TOTAL-REVENUES>                            16,284,837              18,121,374              32,273,665              33,121,711
<CGS>                                       14,998,495              16,666,622              29,887,184              30,466,970
<TOTAL-COSTS>                               16,087,525              17,747,920              32,049,701              32,679,828
<OTHER-EXPENSES>                                     0                       0                       0                       0
<LOSS-PROVISION>                                     0                       0                       0                       0
<INTEREST-EXPENSE>                             171,974                 182,206                 347,389                 371,956
<INCOME-PRETAX>                                      0                       0                       0                       0
<INCOME-TAX>                                         0                       0                       0                       0
<INCOME-CONTINUING>                                  0                       0                       0                       0
<DISCONTINUED>                                       0                       0                       0                       0
<EXTRAORDINARY>                                      0                       0                       0                       0
<CHANGES>                                            0                       0                       0                       0
<NET-INCOME>                                   197,312                 373,454                 223,964                 441,883
<EPS-PRIMARY>                                     0.15                    0.29                    0.17                    0.34
<EPS-DILUTED>                                        0                       0                       0                       0
        

</TABLE>