Gyro Stabilizers for mid-sized yachts

Have you actually run a boat with Sleipner vector fins? That's the only one I indicated, or meant to indicate, you lacked experience with because no where do you mention having such. Now, I don't have experience with many of the brands you do, but I do with that, about 10,000 nm worth with vector fins. (I have more experience in total with Naiad than any other and no experience with Wesmar or CMC). I was not a believer until I ran them. And, for the record, Capt J didn't believe me until he ran a different model with them.

As to the Princess data, it wasn't removed until they redid their site about 2 years ago. I don't know the reason either and won't speculate.

I also made it clear when linking to their site, that it was advertising on their part and clearly prejudiced as such, but an explanation from them of the advantages, advantages I have experienced on the water.

I also did not argue that any zero speed wasn't comparable to Sleipner at anchor. I only stated that Gyro wasn't comparable at speed and non-Zero speed might not be comparable at anchor.

Spin up time is often mentioned as a downside of gyros but in the real world does anyone really hop on, gets under way and reach rough water quickly enough to need stabilization before the gyro is up speed? especially since when anchored out you likely have the gyro going

now an issue which I have never seen mentioned is the amount of power needed. Zero speed only requires an electric motor running the hydraulic pump. A gyro requires a lot more power doesn’t it? So chances are you will need to run a second generator or limit power usage (shut down one chiller, watermaker and limit cooking). I know that we are always close to the limit with a full house...

You are correct. "Also Before" does imply both. I have no experience with the "before."

I am adding 2 sea keeper 6's to my boat right now. I too was concerned about the power needed and how that affects my existing generator's capability. What I was told was to power them up (which is when most draw occurs) while hooked up to shore power, then switch to generator and I should be fine. I have one 21kw onan. It takes 45 minutes for that to occur. I will find out soon enough if I have to add a second generator, hopefully not.

No, actually the yard said I should be fine. I do have 5 ac compressors, so I might have to leave one or two off.

A single Seakeeper 6 works fine on my boat with a single 10kw genset. Even with water heater, ac etc on during startup.

I sometimes start the Seakeeper on dock power if I have a particularly seasick prone guest joining us. No rocking from the beginning makes a difference.

Mapis, do you remember that 16oft yacht getting refitted in Toulouse a couple of years ago? Selling 2 gyro's off at half price because the yard's design engineers ordered them way too small and they did nothing. I think they lost $35k on each one.

You should be ok on generator. I'd be more worried if you have a single 50 amp shore cord and all 5 a/c's running. Flipping off the water heater and an a/c while they're spooling up should keep amps low enough. However, usually you're starting the seakeepers fairly early in the morning and not all 5 a/c's are cooling yet anyways.

I have the ability to add a 2nd shore power cord, and may do that during the hottest parts of the summer. I often have AC's running, plus Ice maker, water heater, etc.

You won't (or shouldn't) be running seakeepers at the marina aside from right before you go out. I really don't think it's a problem if you simply keep an eye on electrical draw while they're spooling up and maybe shutting the water heater and 1 air conditioner off. The generator should handle everything (a/c's, water heater, etc.) once the seakeepers are spooled up. If you want to add a 2nd cord, you always could, but I don't think it will be necessary if you just keep an eye on loads. Generator should handle startup time of seakeeper and all a/c's. So could always just get on Generator early. Plus, there are many times I get the seakeepers started at the dock, but leave the dock well before they're ready because I'm in calm water idling out (Intracoastal etc.) anyways.