Of interest to me at the time I commissioned my tank was that roll-attenuation tanks have been in use since the late 1800s in tankers, with outboard ballast tanks inter-connected with piping and valves to control the flow back and forth as product levels changed in the main tanks.  Systems like that in non-tankers, generically known as “flume tanks” have been in use since the mid 1900s, generally interconnected ballast tanks.  Horizontal tanks like mine were chosen on the product tankers a friend was involved with as they could be and were added after the initial design of the vessels.  Dave and I may have the first pleasure vessels with them.

Another friend of mine spent some years at sea on ocean going tug boats, one memorable trip being a 1/2 knot tow of an oil rig from Rotterdam to Houston. They had an athwartship tank and a graph for changing the amount of water in the tank to maintain comfort as they depleted fuel; someone spent a lot of time with a slide rule figuring that out as it was a 60s built tug.

The most comfortable vessel I have been to sea on was my original Asylum, an 80 foot Dutch built fishing trawler, which I had dreams of converting to a live-aboard cruiser.  While most pleasure trawlers are around a four second roll period, she was 8-10, depending on fuel level. While she rolled almost gunwale to gunwale in a beam sea, it was so slow as to be almost un-noticable.  Roll period is important for comfort in that too short a period is hard on the joints.  Having used catamarans for race committee boats for many years the transition from sail cats to power cats was painful.  The early power cats were sail cats sans rig with fly bridges; where the sailing version was almost a 4 second roll period due to the dampening of the rig, the power cat version was around two seconds, making for painful joints by the end of the day after standing on the fly bridge all day; later versions had increased weight aloft to make them more comfortable.

Robert Phillips
Doyle Sailmakers BVI, Ltd.
bob@doylecaribbean.com
Mobile 284-541-2206
Office 284-494-2569

Bob Philips wrote:

"The most comfortable vessel I have been to sea on was my original Asylum, an 80 foot Dutch built fishing trawler, which I had dreams of converting to a live-aboard cruiser.  While most pleasure trawlers are around a four second roll period, she was 8-10, depending on fuel level. While she rolled almost gunwale to gunwale in a beam sea, it was so slow as to be almost un-noticable.  Roll period is important for comfort in that too short a period is hard on the joints..."

The posts on this subject that have focused on heavy and low ballast  have raised a question in my mind about the roll period of the boats under discussion. My experience has been similar to Bob's - that a "stiff" boat with a short roll period is the source of much discomfort and displeasure. It has been my belief that the most upsetting (pun intended) part of rough water cruising is the tendency for people and belongings to get thrown around the boat. A snappy roll increases the likelihood that things will break loose and people will have a hard time hanging on. Extra stability from lots of low ballast may seem like a good thing, but may actually make a boat less comfortable.

Dick Allen
42" Bristol LRC
Lying Englewood, FL