I wasn't suggesting that someone toss a tank on their boat, fill it with water and go to sea. Bad karma ;-) The designer of our tank is a professor and has many of these tanks designed and in place on boats. Mostly commercial ones. There is, to my knowledge, very few persons (one that I know of) who can do this and have the experience. I suspect that most marine architects would get there tanks designed from this same source. Also to my knowledge there is no one doing this on a commercial basis. That is someone whom you can go to, give $$$ to and end up with a properly designed tank installed on your boat. In other words it is not a product ready for the "public". However for those who wish a very inexpensive alternative to other roll reduction options and have the time and expertise to implement one they are the best. On Swan Song I priced everything as a complete system to reduce the roll on our narrow, heavy, full displacement boat. MHI gyros: $145,000. Two gyros required, a dedicated 16KW genset and 1 16K BTU Air Conditioner to cool the space as they put out lots of heat! Active fins: $45,000 and up. Swan Song again is narrow, heavy and for fins slow. SO we would need large fins and all the attendant hydraulic systems to support them Trim Tab stabilizers: These are really not suitable for slow boats as they need at least 12-15 kts before they can be effective. They also are not cheap at $100K or so. Paravanes: $25-30K. Given the hull wasn't suitable for them as built we would need major structural changes to support the loads generated. Roll Tank: $11K. Design cost; $4,500. Materials $2500, Labor to build $2500, Cost to install on the pilothouse deck $1,500. Cost to fill $25.00 So, we didn't enter into this lightly and we knew we wanted a system that works full time whether the boat is moving or not. It is possible it could have all just gone bust but the designer has a good track record and we had faith. We also had been aboard Bob Phillips' Another Asylum and were very impressed with the results he achieved. Many of the Canadian fishing boats up in the Newfoundland to Cape Sable area are using then in lieu of paravanes now. It had to take some convincing arguments to get them to change ;-) So, as Steve says, these are not for everyone and there is a very small knowledge base out there in using them on small boats. I'm not sure who's tank design Mike Kasten was using for his comparison of roll reduction but in reading the article it seems it hadn't been explored in depth, IMO. Cheers Dave & Nancy Swan Song 787 990-6064 Sat 954 252-3830 fax -----Original Message----- From: passagemaking-under-power-bounces@lists.samurai.com [mailto:passagemaking-under-power-bounces@lists.samurai.com] On Behalf Of Steven Dubnoff Sent: Wednesday, August 30, 2006 3:16 PM To: Passagemaking Under Power List Subject: Re: [PUP] FW: Swan Song in Venezuela At 09:08 AM 8/30/2006, you wrote: >Very interesting post. I've never heard of the stability tank. How would I >get ahold of the software to design one or have one designed for me? This is, I think, a job for a professional, as poorly designed roll tanks can easily decrease stability. Michael Kasten has a discussion of roll--reduction strategies here: http://www.kastenmarine.com/roll_attenuation.htm Best, Steve Steve Dubnoff 1966 Willard Pilothouse www.mvnereid.com sdubnoff@circlesys.com _______________________________________________ Passagemaking-Under-Power Mailing List