The hinge pin of success

In response to last month?s feature focusing on Bill Wen Change Huang?s design for an ultra-large hinged container ship, The Motor Ship received this letter from Joseph P Fischer,

President

of Bay Engineering, Wisconsin, USA, pointing to the connector pins as the concept?s potential.

Dear Sir,

With regard to the hinged ship design by Mr. Huang in your June 2004 issue, I offer the following comments: In 1994, a hinged vessel consisting of a barge forward and a ship aft, was designed for Great Lakes service by R.A. Stearn, Naval Architects & Marine Engineers, the predecessor of

Bay Engineering, Inc.

Each vessel was 172.82m x 25.77m at a draft of 8.38m and displaced about 30,800 tonnes in fresh water.

The combined unit was model tested at the Wave and Current Basin of MARIN at Wageningen, the Netherlands, with the final report made in January, 1995. The loads at the connector hinge pins were measured in 3 axis with the model in irregular seas using a JONSWAP spectra with a significant wave height of 10.0m and a maximum period of 14.0 seconds. The model was tested at five (5) wave directions; head on, bow quartering, beam seas, stern quartering and following. The largest loads on the connector pins occurred at the oblique wave heading. The results were statistically presented. At standard deviation, the horizontal loads on the pin are about eight (8) times the vertical loads and the transverse loads are about 3/4 of the vertical loads. At maximumpeak condition, the horizontal loads on the pin were about 125,000 KN and deemed not economically feasible to construct. The hinged vessels were never built.

I suggest that Mr. Huang investigate the horizontal bending in way of the hinge pins while operating in a high sea state. The combined horizontal and vertical sheer forces on the hinge pin can be very large and probably the reason why none such vessels exist.

Respectfully submitted,

Joseph P Fischer, PE

President

Bay Engineering, Inc.