Dollars Per Degree Damping

I mentioned in a prior post that I might try a comparison of the various common anti-roll systems.  Something that I would call "Dollar per Damping Degree" ($/D°).  I actually had started doing a comparison of the systems before I decided to experiment with the anti-roll tank (ART).  I knew that the other systems would all cost more time, money, fuel, and some even require a generator, but I didn't know which ones might be more effective.  While some people might like the idea of roll reduction at any cost, it seemed like getting one's money's worth might be a goal.

Probably the biggest difficulty in doing a comparison is getting accurate numbers.  There are claims as to what a new roll reduction system "feels like," but actual measured numbers are rare.  The same is true with costs.  I can measure the reduction of my ART and I have receipts for the costs, so those are the only actual numbers in my chart.  The other numbers I pulled from various postings on the web, some of them from end users and some from purveyors.  When a purveyor says their gyro system (for example) costs $23K, one then has to guesstimate the installation costs.  Same with annual maintenance.  Same with haul outs and yard times for other roll reduction systems.  Those numbers in my $/D° chart are followed by a "?" because they are gleaned from various posts on the web.  If you have accurate numbers for costs, degree reduction, etc., for a system, please post in the comments so that I can update the chart.

My boat is small by trawler standards (32' LOA), so any system would be small (like the gyro at only $40K) and costs would be small (in comparison to larger boats).  Still, some stabilization systems would require the installation of a $10K generator running nonstop (like the gyro), in order to stabilize at anchor.  Other systems, like paravanes, sort of work at anchor, but at a greatly reduced roll attenuation capability.  Because roll reduction both while running and at anchor are important to me, my $/D° calculation takes that into account.  Paravanes are generally seen as 40-60% degree roll reduction underway (depending on speed), while only 10-30% at anchor.  If I average those numbers (50% underway and 20% at anchor), I would then weigh those numbers equally, coming up with 35% reduction overall.  Dividing overall costs by the average overall reduction produces a of $603 per degree of damping.  The chart shows earlier numbers and a higher $/D° of $704.

The numbers are interesting because the material costs and installation are so little for the ART.  It was within my abilities to build the tank and put it in place.  I'm not sure that I would try DIY with the other systems.  Self-installing the rolling chocks maybe?  It would be 10 times the work involved with the tank, but that would reduce the $/D° even further for chocks.  

The effectiveness of the ART is also easily measured, unlike the other systems.  But being as no other system came close to the ART on costs and time, I'm not going to do any further analysis or research on the time, expense, and effectiveness of the other systems.