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Old 02-19-2014, 06:40 PM   #21
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If you really want to wallow, go to www.mvtanglewood.com and follow the link on the right to stabilizer installation.
Very impressive work and site. I read about your install a year or two ago on another forum. I have 7ft2 units on my vessel, sized for a bit lower speed than likely yours were. Even at 6 knots in a big beam sea they are doing their thing.
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Old 02-19-2014, 06:50 PM   #22
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Yes, ours are 6 or 7 foot. - I can't remember which - but they were sized to be effective at slow speed, and they are. I can't speak highly enough about ABT. They really set the gold standard for engineering and customer support

We are going with ABT again on the Nordhavn, including hydraulic thrusters and windlass. The really new thing that I can't wait to experience is stabilization at rest, or STAR. So far the reports from other owners is very encouraging.
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Old 02-19-2014, 07:41 PM   #23
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Greetings,
Naiads here. Definitely did NOT want any stabilization while boat searching. Definitely do NOT want to be without now.
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Old 02-19-2014, 09:09 PM   #24
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We are going with ABT again on the Nordhavn, including hydraulic thrusters and windlass.
How are the hydraulics set up to operate when the main is at idle when you are docking? A Nordhavn I was looking at recently got around this by operating hydraulic thrusters off the genset PTO when docking.
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Old 02-19-2014, 09:20 PM   #25
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How are the hydraulics set up to operate when the main is at idle when you are docking? A Nordhavn I was looking at recently got around this by operating hydraulic thrusters off the genset PTO when docking.
You didn't ask me, but.....

I put a large pump in front of the CAT turned by a pto connected to the flywheel. That provides enough flow to power either the bow or stern thruster at about 1/2 flow. If I want both and full flow, like the Nordhavn you referenced, the genset with an auxiliary pump takes the load.
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Old 02-19-2014, 09:23 PM   #26
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How are the hydraulics set up to operate when the main is at idle when you are docking? A Nordhavn I was looking at recently got around this by operating hydraulic thrusters off the genset PTO when docking.
On my Offshore 54 the port engine runs the pto for the hydraulics on the thruster and the stabilizers. I have to increase my rpm's on that engine to about 850 to keep the thruster from bogging down.

FWIW I would not own another LRC without stabilizers.......and neither would my wife.
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Old 02-19-2014, 10:08 PM   #27
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Like many here we have the ABT,9 sq ft on a 58' 50+ton boat. They are work extremely well and so far have been virtually trouble-with and the routine maintenance is quite easy. Would never again have a boat without them.
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Old 02-19-2014, 10:39 PM   #28
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the hydraulic pump uses very little power when it is in standby. The horsepower formula for hydraulics is: HP= gallons per minute x psi divided by 1714.

if you have a 6 gallon per minute pump just idling at about 20 psi it is drawing down .07 horsepower. When the stabilizers come on for just a few seconds your pressure can go to 1500 psi which is 5.25 hp for those few seconds.

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Old 02-19-2014, 11:57 PM   #29
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the hydraulic pump uses very little power when it is in standby. The horsepower formula for hydraulics is: HP= gallons per minute x psi divided by 1714.

if you have a 6 gallon per minute pump just idling at about 20 psi it is drawing down .07 horsepower. When the stabilizers come on for just a few seconds your pressure can go to 1500 psi which is 5.25 hp for those few seconds.

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That's interesting, thank you.
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Old 02-19-2014, 11:59 PM   #30
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the hydraulic pump uses very little power when it is in standby. The horsepower formula for hydraulics is: HP= gallons per minute x psi divided by 1714.

if you have a 6 gallon per minute pump just idling at about 20 psi it is drawing down .07 horsepower. When the stabilizers come on for just a few seconds your pressure can go to 1500 psi which is 5.25 hp for those few seconds.

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Maybe I'm missing something John but once my stabilizer switch is turned to on the gauge says 1200 or so PSI and the Vickers pump is moving fluid. I don't understand what you mean by "when the stabilizers come on for just a few seconds."
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Old 02-20-2014, 08:26 AM   #31
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if your pressure stays at 1200 psi you have a variable volume pump. the math still works. with a fixed displacement pump working in standby the oil flows through a control valve and back to tank at low pressure ( 6 gpm x 20 psi / 1714 = .07 hp). with a variable displacement pressure compensated pump in standby you have high pressure a zero flow
( 0 gpm x 1200 psi / 1714 = .7 hp). they now use load sense pumps that in standby give you zero flow at 200 psi ( 0 gpm x 200 psi / 1714 = .11 hp.). The fixed pump has the lowest horsepower draw in standby, the highest horsepower draw when working. the variable pressure compensated pump has higher in standby but better in working mode. The loadsense pump gives the best all around; very low in standby and extremely low when working.
Almost all new construction machines today use loadsense. It's all about fuel savings. Your Vickers pump is probably a PVB6 series.
My company is the Eaton Vickers distributor for the east coast.
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Old 02-20-2014, 08:42 AM   #32
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if your pressure stays at 1200 psi you have a variable volume pump. the math still works. with a fixed displacement pump working in standby the oil flows through a control valve and back to tank at low pressure ( 6 gpm x 20 psi / 1714 = .07 hp). with a variable displacement pressure compensated pump in standby you have high pressure a zero flow ( 0 gpm x 1200 psi / 1714 = .7 hp). they now use load sense pumps that in standby give you zero flow at 200 psi ( 0 gpm x 200 psi / 1714 = .11 hp.). The fixed pump has the lowest horsepower draw in standby, the highest horsepower draw when working. the variable pressure compensated pump has higher in standby but better in working mode. The loadsense pump gives the best all around; very low in standby and extremely low when working. Almost all new construction machines today use loadsense. It's all about fuel savings. Your Vickers pump is probably a PVB6 series. My company is the Eaton Vickers distributor for the east coast. John MS390
Smaller ABT systems use a fixed displacement pump as you describe. But the only time pressure is relieved is when they are turned off. Otherwise pressure and flow are maintained by way of a regulator relief valve. So even if the fin isn't moving you are consuming full power. Its not ideal, but the power draw is small in the grand scheme of things.

The bigger systems use variable displacement pump which maintain pressure, but regulate it by controlling flow. The result is engine load that mostly tracks the actual consumed power by the fins. Its more expensive, but definitely a better setup.
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Old 02-20-2014, 08:51 AM   #33
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How are the hydraulics set up to operate when the main is at idle when you are docking? A Nordhavn I was looking at recently got around this by operating hydraulic thrusters off the genset PTO when docking.
They work pretty much as others have described for other boats. There is a pump off the main engine trans that operates the stabilizers while underway, and the thrusters and windlass while docking/anchoring. But as noted, at idle the main engine pump can only do so much. It basically can operate and one device including a single thruster up to full power, or close to full power. But if you run both thrusters the available power is split between them and they operate at reduced power.

The gap if filled with a second pump run either off the wing engine or gen set. Most Nordhavns run the pump off the wing engine. Its a great way to be sure it gets exercised. Mine runs off the genset, but the decision was totally driven by the stabilization at rest feature which of course needs power while at anchor. It makes much more sense therefor to run off the gen rather than the wing. The gen is quieter, is useful to run for other reasons, and is better loaded than the wing which would be running at very light load with just hydraulics under power.

Even bigger boats with 24x7 genset power will often power the hydraulics via a 3-phase electric powered hydraulic pump.
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Old 02-20-2014, 12:08 PM   #34
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Mine runs off the genset, but the decision was totally driven by the stabilization at rest feature which of course needs power while at anchor. It makes much more sense therefor to run off the gen rather than the wing. The gen is quieter, is useful to run for other reasons, and is better loaded than the wing which would be running at very light load with just hydraulics under power. .
Back on point ------

Given you will run your genset at rest if needed and the N60 has the space in the very large lazarette for a Gyro setup, what were the tradeoffs in your decision comparing ABT & STAR to Gyro stabilization?
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Old 02-20-2014, 09:21 PM   #35
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I want one system for underway and at rest, and picked ABT. I've had a great experience with them on my Grand Banks, so went with them again. With everything else hydraulic, it makes sense for the stabilization to be hydraulic as well. Plus I still don't want to have to run a generator for stabilization underway, so that further drove me towards a hydraulic approach.
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Old 02-21-2014, 09:22 AM   #36
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When we built hulls 1 and 2 of our Northwest series, hull 1 had ABT stabilizers and hull 2 had none. Top speed was .5 knots greater with hull 2. ABT installations have been great with little or no issues. Hull 2's owner, however recently installed Keypower stabilizers and is very happy with them. We installed Keypower stabilizers and thruster on another boat we built in 2004 and the owner reports nothing other than routine maintenance and would buy Keypower again.
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Old 02-21-2014, 09:39 AM   #37
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When we built hulls 1 and 2 of our Northwest series, hull 1 had ABT stabilizers and hull 2 had none. Top speed was .5 knots greater with hull 2. ABT installations have been great with little or no issues. Hull 2's owner, however recently installed Keypower stabilizers and is very happy with them. We installed Keypower stabilizers and thruster on another boat we built in 2004 and the owner reports nothing other than routine maintenance and would buy Keypower again.
Useful comparison, thank you Peter.

Do you think it possible that in a seaway, there would be improved tracking on the vessel with stabilizers that would offset the speed loss until more benign conditions? Don't know myself, but I have always wondered.
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Old 02-21-2014, 10:46 AM   #38
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Useful comparison, thank you Peter. Do you think it possible that in a seaway, there would be improved tracking on the vessel with stabilizers that would offset the speed loss until more benign conditions? Don't know myself, but I have always wondered.
At the risk of being jumped on by all the experts here, I will break my rule and answer an excellent question; a question that will surely illicit a lot of comment from others.

Hulls will always track their straightest when they are sitting on their lines. As a hull rolls or heels, uneven lift is generated, causing the hull to steer. Now if the hull is rolling, the boat will wander in sync with the roll.

So now the question of roll period comes in. A snappy boat with a very short roll period will tend to not wander as much as a boat with a longer roll period as the hull will be returning to the level quicker, thus arresting the directional instability.

Boats with longer and deeper keels will tend to wander less than those with shorter keels or no keels as in the case of many planing hulls.

Boats with larger rudders will tend to wander less than those with smaller rudders.

So back to the original question; generally speaking, a boat with active fin stabilizers will tend to track straighter than one that is not stabilized, all other things being equal. BUT..........

A stabilized boat can also develop "stabilizer steer". If the stabilizers are installed in an improper position or at the wrong angle, they can cause the boat to steer as they actually are 2 more "rudders" on the boat. As the boat begins to roll, the stabilizers may more than offset the rudder and the boat wanders. Steve Seaton can tell you a story about a well known boat builder who didn't listen to him as to where the stabilizers should go The boat wandered terribly, and it was costly for them to move the stabilizer fins to where he said they should be in the first place.

Another issue is that some people like to run their stabilizers in the "zero heel" mode. If the boat does not tend to sit on its lines (athwartship), then forcing it to by using the zero heel mode will make it steer in the direction the stabilizers have moved to bring the boat back to level. I have experienced being underway in relatively calm seas, observing the stabilizers offset to one side (on the control panel) to counteract the heel and the rudder angle off in the opposite direction to keep the boat going straight. This definitely is increasing drag.
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Old 02-21-2014, 10:57 AM   #39
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So back to the original question; generally speaking, a boat with active fin stabilizers will tend to track straighter than one that is not stabilized, all other things being equal. BUT..........
So, is it fair to say that a vessel that will track relatively easily natively (long keel, adequate rudder), will not suffer additional drag from fighting the action of the stabilizers, and where those stabilizers are optimally situated may decrease overall drag in lumpy conditions?

(Trying to pin you down here Peter.....)
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Old 02-21-2014, 11:45 AM   #40
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So, is it fair to say that a vessel that will track relatively easily natively (long keel, adequate rudder), will not suffer additional drag from fighting the action of the stabilizers, and where those stabilizers are optimally situated may decrease overall drag in lumpy conditions?

(Trying to pin you down here Peter.....)
I think a few years back someone posted some real world numbers that their economy increased with use of the fins due to the boat riding on it's lines better.

However, like many performance discussions on TF...SO many variables come into play, to measure performance between 2 boats that aren't exactly alike ....as you change the equation...you really can't predict exactly what YOUR boat may do.... but if I were to bet...the drag caused by fins could easily be nullified by smoothing out the ride and eliminating forces that Peter described.
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