Click for Delta
Click for Burger
Click for Trinity
Click for Walker
Click for Christensen
Click for Lurssen
Go Back   YachtForums.Com > GENERAL YACHTING DISCUSSION > Technical Discussion > Anti-Rolling Gyro or Stabilization Fins

Login to YachtForums
Username
Password

Reply

Anti-Rolling Gyro or Stabilization Fins

 
 
LinkBack Thread Tools Rate Thread Display Modes
Old 08-19-2010, 02:35 PM   #16 (permalink)
Registered User
 
Join Date: Aug 2010
Location: Ft Lauderdale
Posts: 2
Wink Mitsubishi ARG test ride

I got the chance to ride on a bertram 70 the other day. it had the mitsubishi stabilizers installed. what a difference it made! When up on the fly bridge it was so steady we could have made breakfast if we had a grill! Down below where they were running they just sat there, no moving parts, safe as could be. This is going to become standard equipment someday!
rixter55 is offline   Reply With Quote
Old 08-19-2010, 02:47 PM   #17 (permalink)
Registered User
 
Join Date: Jan 2010
Location: Seaford NY
Posts: 7
In a recent issue of Power and Motoryacht, there was an article about one of these gyros installed on a charterboat fishing out of NJ (I think). Quite interesting. Although one of the long-time captains was skeptical, he was quite surprised at it's effectivness.
phildehazya is offline   Reply With Quote
Old 08-19-2010, 03:42 PM   #18 (permalink)
Publisher/Admin
 
YachtForums's Avatar
 
Join Date: Dec 2002
Location: South Florida
Posts: 18,208
Quote:
Originally Posted by rixter55
This is going to become standard equipment someday!
Don't count on it. A mechanical gyro will never replace active fin stabilization. While a single axis spinner can offset roll momentum/acceleration, to a certain degree, it can only react to motion. It is not able to provide a continuous counter effect in the same way as subsurface fins with water passing over them.

Because these gyro based systems are one dimensional in nature, they can only provide anti-roll assistance. They can do nothing to counter pitch, whereas stabilization fins, such as Quantum and others, can do both. That said, the latter has been geared toward larger applications and isn't always suitable for smaller apps.

Another potential issue is longevity of gyro-based systems. We really don't have much long term data on reliability. And while you might call me skeptical, gyro reliability in other apps has been known to be spuratic.

As for these units becoming standard equipment, not at their cost and weight penalty.
YachtForums is offline   Reply With Quote
Old 08-19-2010, 11:50 PM   #19 (permalink)
Senior Member
 
tirekicker11's Avatar
 
Join Date: Jul 2010
Location: SE Asia
Posts: 325
I guess these Gyro's have to be installed on the centre line midships, or could you install one off centre?
tirekicker11 is offline   Reply With Quote
Old 08-20-2010, 07:24 AM   #20 (permalink)
Publisher/Admin
 
YachtForums's Avatar
 
Join Date: Dec 2002
Location: South Florida
Posts: 18,208
Where the gyro is mounted isn't as critical as keeping the center of gravity as low as possible, in effect using the weight of the gyro as ballast. They are typically mounted in the bilge, aft of the engines and between the drive shafts. Not a very friendly environment for a precision instrument. While the optimum mounting point should be closest to the center of rotation, in reality the best place to mount a heavy, mechanical gyro is closest to the greatest mass.
YachtForums is offline   Reply With Quote
Old 08-20-2010, 07:44 AM   #21 (permalink)
Publisher/Admin
 
YachtForums's Avatar
 
Join Date: Dec 2002
Location: South Florida
Posts: 18,208
Just came across another thread we had on gyros...

http://www.yachtforums.com/forums/te...tabilizer.html
YachtForums is offline   Reply With Quote
Old 08-22-2010, 01:48 PM   #22 (permalink)
Registered User
 
Join Date: Apr 2010
Location: Bradenton, FL
Posts: 6
Gyro

Fins are defiantly better than the Sea Keeper system on the boat I was able to directly compare. I would say the gyros were less than 50% as effective as the fins and the gyros dampen the roll but do not try to seek level so if you have a strong cross wind the fins will put you level but the gyros will let you list. We are outfitting a boat with both right now so you can use the fins running and have a gyro for anchoring out.
motoryachtbill is offline   Reply With Quote
Old 08-22-2010, 07:21 PM   #23 (permalink)
Senior Member
 
tirekicker11's Avatar
 
Join Date: Jul 2010
Location: SE Asia
Posts: 325
Quote:
Originally Posted by YachtForums
Where the gyro is mounted isn't as critical as keeping the center of gravity as low as possible, in effect using the weight of the gyro as ballast. They are typically mounted in the bilge, aft of the engines and between the drive shafts. Not a very friendly environment for a precision instrument. While the optimum mounting point should be closest to the center of rotation, in reality the best place to mount a heavy, mechanical gyro is closest to the greatest mass.
Probaply a stupid question but why is the gyro not installed where the rolling motion is the most? Like on the flying bridge.
I am not an engineer and can't do the math but something tells me that its something with force and moment.
tirekicker11 is offline   Reply With Quote
Old 08-22-2010, 11:57 PM   #24 (permalink)
Senior Member
 
Join Date: Mar 2010
Location: Silver Spring, MD
Posts: 116
Gryos

Yep; I believe the phrase "polar moment of inertia" applies here, but don't ask me how.

If money were no object, it would seem that stabilizer fins and gyros would be the way to go. Presumably you'd have to heavy-up the generator(s) and the wiring to handle the extra load, so that's even more expense. Still.......
vlafrank is offline   Reply With Quote
Old 09-19-2010, 12:04 PM   #25 (permalink)
Senior Member
 
brian eiland's Avatar
 
Join Date: Jul 2004
Location: Washington DC, Annapolis MD, Thailand
Posts: 2,436
just happened on this from a PUP forum, and thought it might have some interest in these discussions


We had looked into these units when Swan Song was earlier in the stage of re-construction. At the time, according to the factory man in Japan, we'd need two of the mid-sized units to keep Swan Song from rolling less than 25 degree each side. If a sea state was at the level that we were rolling this much the power required to keep them both spinning was just over 8 KW. This all according to them. In a really nasty sea state they would need to be turned off as if they hit the stops often and with too much force they might self destruct. Suffering and surviving a knockdown wasn't in their vocabulary! All in all we opted not to go in that direction as the predictability of sea state isn't within our ability in making a passage.

As most of you know we went the route that few have taken and for the life of me I don't know why. An Anti-roll tank, ART, is our only roll reducing system on Swan Song. A totally passive device with no maintenance to date, 5 years, and only one moving part, water.

I wish I could say exactly what the numbers are for roll reduction but I can't. What I can say is that in 15,000 odd nm we have never rolled more than 30 degree and perhaps on 20-25. This includes a tough patch coming into Hawaii last year in waves that were occasionally in the 30' range. We can sit with no way on in 8-10 ft. seas with very little movement. So little that you can work on things and not be chasing tools all over the place. This is a very comforting fact especially when you have to shut down the engine for daily checks at sea.

For some reason Naval Architects hate them. They are afraid that they will somehow encourage a capsize or something similar. We have found all of this is bunk. Swan Song is stiff and has a high righting moment but it is round bilged and likes to roll and once started would go on for 12-15 rolls as a minimum. We tested all of this with full inclination tests, etc. Our boat parameters were fed into the computers that Dr Bass up in Newfoundland runs with his software and came up with the design tuned to our boat. $10,000 later it was constructed and put in place on top of Swan Song's Pilothouse. 1500 lbs. of water over our heads ;-)

Everyone who has ever been aboard either on the hook or underway is astounded by how Swan Song behaves in the water. At first they are puzzled and then as they watch other boats nearby whether they are sailboats with the masts waving in the sky or power boats showing lots of bottom paint they realized that Swan Song doesn't hear the music that the other boats are dancing to. As Seahorse John (now departed) once said in Bequia after an evening on board with the ferryboats passing 50' away without spilling the wine, "I thought you must be aground as you aren't rolling like the others". Then as he watched us round the point heading north out of the harbor the next day waiting for the first African tradewind swell to pin us down Swan Song just went on her merry way. "**** I got to get that system".

Bob Phillips, Another Asylum, has the same system done by Dr Bass. He is the one that sold me on it. Check with Bob as I think he'll compliment just about everything I've said.

I can't compare if paravanes would be as good but I don't think so especially at slow speeds, stopped or in shallow water plus they do require effort. Active fins are nothing but trouble long term and because of our size, propensity to roll, and slow speed the size of a system for Swan Song is large and in the order of $75K with all the attendant maintenance over the years. We would already be due for an overhaul. So for us the option was the paravanes or ART. Glad we made the choice we did and have never looked back.

Also as to significant wave height measurement, significant wave height is the average of the highest 1/3 of the wave. The actual wave height can be as much as 3 times that on occasion and from my experience usually is. Our height of eye is 12' off the water sitting in the pilothouse and beam waves up to this height aren't comfortable but offer no problem on the beam. Even an occasional crest coming aboard just tosses you sideways. Bigger waves that this and we are either taking them further forward or further aft. Dead down we are fine even in that 30' stuff near Hawaii. 20-30 degrees off our stern is our weak point. We get both the pitch and a roll so the corkscrew motion gets uncomfortable pretty quickly

Dave & Nancy
Swan Song
Roughwater 58
brian eiland is offline   Reply With Quote
Old 09-19-2010, 02:17 PM   #26 (permalink)
Senior Member
 
Join Date: Feb 2006
Location: Baltimore
Posts: 206
When I first seen these gryos, My first thought is why spin a mass of steel around for stability? I would design a system that uses the weight of fuel ~7# per gallon,spin that in a centerfuge(using helical screens and coalesing medium and you could get the benifits of fuel polishing,(you would have to have a steady flow rate through the centerfuge so not breakdown the fuel) . gryoscopic stablization and fuel polshing/water seperation all in one unit.
wdrzal is offline   Reply With Quote
Old 09-19-2010, 02:30 PM   #27 (permalink)
Registered User
 
Join Date: Mar 2009
Location: outbound
Posts: 84
Roll tanks (called Flume tanks) have their following in Europe. I recently attended the launch of one of a series of ro-ro ferries for Med service that use flume tanks for roll stabilization. On a smaller scale, the old 24.4m class of the Norwegian NSSR rescue cutters relied entirely on a central (diesel) flume tank for roll stabilization.
lobo is offline   Reply With Quote
Old 12-10-2010, 05:24 AM   #28 (permalink)
Registered User
 
ton_meeus's Avatar
 
Join Date: Dec 2010
Location: the creek Dubai
Posts: 2
I've been involved in stabilizers and have been looking into gyro based systems and zero speed stabs as the owner wanted a zero speed system to replace the current underway system. There are significant differences between both systems. Fins typically perform well when underway due to the waterspeed that creates lift. The higher the speed the bigger the lifting force. When on anchor there is no water speed and the fins generate no lift at all. The "artificial" solution is moving the fins actively while anchored. It is easy to understand that the roll reduction is not comparable at all with the roll reduction achieved underway. If one looks at the geometry of zero speed fins one notices that the fins are less high but longer called lower aspect ratio. This is to create more momentum when the fins are slewing around. Normal underway fins are higher and perform much better than the lower zero speed fins. That is why zero speed fins always have a bigger area! They are less efficient and cause more drag.

The gyro's are indefinitely better when on anchor. To get similar performance with fins one would have to fit fins with a huge area or even fit four fins. So where is the catch? Are gyro's the solution for modern yachts?
There are a few aspects to be considered such as yacht configuration and on mission profile. For fast hulls with a low mission profile I think that gyro's are the best option. You don't want big fins sticking outside on fast hulls.
For displacement hulls both options could be o.k. Mind you contrary to fins, the performance of the gyro based systems goes down when the hull speed increases.

In my view nothing can beat fins when underway and for zero speed gyro's seem to be the best choice instead of big fins that need to be slewed around. Since we have underway fins I suggested gyro's as zero speed option so we would have both systems onboard.
ton_meeus is offline   Reply With Quote
Old 03-20-2013, 01:07 PM   #29 (permalink)
Registered User
 
Join Date: Jan 2004
Location: Ft. Lauderdale
Posts: 191
Cool Roll one for me!

If the boat doesn't go anywhere, the gyros work well. But then again, why would anyone choose an anchorage where one would need stabilizers?
aeronautic1 is offline   Reply With Quote
Old 03-20-2013, 05:22 PM   #30 (permalink)
Senior Member
 
Pascal's Avatar
 
Join Date: Feb 2008
Location: Miami, FL
Posts: 2,377
Quote:
Originally Posted by aeronautic1 View Post
If the boat doesn't go anywhere, the gyros work well. But then again, why would anyone choose an anchorage where one would need stabilizers?
Guess you haven't spend much time cruising the Bahamas... There are many very nice anchorages where the surge can be felt...
Pascal is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are EST. The time now is 02:48 AM.

Click for Burger
Click for Moonen
Click for Elling
Click for JetForums
Click for MotorCheck
Click for Bering


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.

Content Relevant URLs by vBSEO 3.3.2