Whale Research Vessel Towing Post - Design and Installation

In the summer of 2004 Allied Whale, based at the College of the Atlantic in Bar Harbor, Maine, purchased a 26-foot General Marine Downeast cruiser for their whale research projects. Autopsies of deceased whales is an occasional part of the organization's work, so the ability to tow a dead whale was a requirement for the boat. As we had done some work for the college in the past, we were contacted to see if we would evaluate their proposed post design and make recommendations for both its construction and installation on the new boat.

Given an estimated weight and dimensions for a whale carcass, an assumed maximum towing speed, and assuming water temperature and salinity for a worse case situation, we calculated the likely drag produced by a whale-shaped body. Using that drag force, an assumed acceleration of 2g due to wave action, and including a safety factor of 3, we evaluated the strength of Allied Whale's proposed design. Our calculations suggested that it be strengthened and enlarged slightly to withstand the anticipated loads. We then drew up construction plans for the towing post and base.

We also analyzed the boat's deck structure to insure that it could handle the loads imparted by the post when in use. General Marine provided us with a lay-up schedule and framing details, from which we were able to calculate the loads the deck could support. We then developed a mounting base assembly to be installed below the deck, in way of the post, to which the post assembly could be bolted.

When we had completed our analyses we wrote up a final report, completed the plans for the towing post, mounting base assembly, and installation details, and sent them off to Allied Whale. Subsequently, we were informed that the post was fabricated and installed successfully.

We heard no more until we recently had occasion to contact Allied Whale on a different matter. At that time we learned that the boat had successfully towed a 20-ton sperm whale carcass back to the college from well offshore. Our analyses had included what we felt were sufficiently large safety factors, given our assumptions of loads, drag coefficients, and other variables. This load, however, was twice what we had been told to expect, so we were glad to learn that there was no visible damage to the post, tow line, or deck structure. Click here to download the images of the Whale Research Towing Post.

Background photograph by Alison Hudson