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Old 02-21-2014, 01:25 PM   #41
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(Trying to pin you down here Peter.....)
My former JV partner is a brilliant aeronautical engineer. During our association, we had many discussions where he would complain about the relative lack of engineering standards available with respect to naval architecture vs. what is available in aeronautical engineering. How data collected from tank testing paled in comparison to that of wind tunnel testing. There were just too many variables in hydro dynamics to nail down an absolute standard for many important design elements. Each new design is compared to previous designs.......not to an absolute standard. He finally retreated back to aircraft design.

So.....in answer to your question, you can't pin me down because in order for me to prove one argument over another, I need a way to measure and compare under equal conditions. And that is not possible. (me tap dancing)
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Old 02-21-2014, 01:41 PM   #42
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My former JV partner is a brilliant aeronautical engineer. During our association, we had many discussions where he would complain about the relative lack of engineering standards available with respect to naval architecture vs. what is available in aeronautical engineering. How data collected from tank testing paled in comparison to that of wind tunnel testing. There were just too many variables in hydro dynamics to nail down an absolute standard for many important design elements. Each new design is compared to previous designs.......not to an absolute standard. He finally retreated back to aircraft design.

So.....in answer to your question, you can't pin me down because in order for me to prove one argument over another, I need a way to measure and compare under equal conditions. And that is not possible. (me tap dancing)
Retreating into Godel's Uncertainty theorem, eh?

Permission to treat the witness as hostile, your honor.
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Old 02-21-2014, 01:49 PM   #43
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Yes........retreating in Godel's theorem (thank you Wikipedia). But not hostile at all. Just can't prove nuthin' to no one........no how. And I would be a fool to try. And besides.....I am entitled to my opinions......no matter how wrong they may be.
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Old 02-21-2014, 02:08 PM   #44
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This is probably apropos of nothing, but the earlier discussion of gyros running amuck reminded me of this picture of the Tennessee Valley Authority's Ocoee #2 hydroelectric powerhouse. I used to work for TVA but can't remember if it was a governor overspeed failure or if they tried to synchronize the unit to the grid out of phase. Whatever they did, the massive rotor and turbine shaft exited the building. Witnesses when this happened in the 1940's said it went partway up the side of the Ocoee gorge before finally coming to rest. Not sure I'd ever be able to get that image out of my head if I had a gyro on board.

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Old 02-21-2014, 02:10 PM   #45
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I'd never fly an airliner if I thought I was going back to 1940's tech and maintenance...seriously?

I would think a bazillion law suits since the 40's would have wised up most companies and engineering standards for failures.
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Old 02-21-2014, 02:42 PM   #46
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some years back there was talk of utilizing the existing large rudders on some trawlers to offset roll.

I believe the idea was to get some sort of roll input device to fire off a big fast hydraulic pump to 'whip' the rudder to compensate for the roll from a wave.

I don't remember this idea happening for our size boats, but think some larger ships may utilize this type of roll dampening.
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Old 02-21-2014, 04:38 PM   #47
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I'd never fly an airliner if I thought I was going back to 1940's tech and maintenance...seriously?

I would think a bazillion law suits since the 40's would have wised up most companies and engineering standards for failures.
You'd think so, wouldn't you? Seriously!

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Old 02-21-2014, 08:11 PM   #48
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One concern I haven't ever head addressed, probably because it isn't one, is the need for the hull to be able to withstand the torque loads involved. From one Gyro manufacturer website:

The gyro foundation saddle beams should be attached to stringers using an adhesive bonding agent. The stringers and bonding agent must be capable of reliably and effectively transmitting the gyro's torques to the hull structure through an infinite number of fully reversing load cycles.

An infinite number of reversing load cycles sounds like rather a lot of them, and I just wonder about fatigue being an issue at some point. Probably not a problem, but just curious.
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Old 02-21-2014, 08:25 PM   #49
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Delfin-I have had the same question. Reading that the saddle is attached to stringers with an "adhesive bonding agent" doesn't ease my concerns. I have wondered about the directional forces on the stringers from a gyro, i.e lateral or angular forces where stringers are primarily designed to absorb longitudinal forces. Have gyros been around long enough to see if there are any issues created where the hull and stringer come together?
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Old 02-21-2014, 09:33 PM   #50
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This probably isn't a whole lot different from the forces generated by fins, with similar structural reinforcement required - or at least analysis required.
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Old 02-21-2014, 10:34 PM   #51
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Gyro Stabilizers & Nordhavn

Last year when we considered building N3 I spoke with the west coast sales representative about being the first Nordhavn with a Gyro system. To make a long story short the promises made were not kept (representative over stepped his authority). Even if the arrangement would have worked out I'm not sure we would have proceeded in part to the proven track record of Trac Stabilizers and having to run the generator full time. If we built another new boat I would likely go with Trac stabilization again.

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Old 02-22-2014, 12:03 AM   #52
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This probably isn't a whole lot different from the forces generated by fins, with similar structural reinforcement required - or at least analysis required.
Maybe, but I'm not so sure. First of all, the loads of fins on a particular place on hull is 1/2 because there are two of them. Second, the fins act in water, where the load is spread over the entire fin. With a gyro, all of the force of correction is placed directly on a relatively small part of the hull. You might be right, but I can't quite visualize it.
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Old 02-22-2014, 01:59 AM   #53
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Delfin-i think how the forces are placed on the hull are entirely different. The "collar" or the part actually attached to the hull is backed by a good sixed backing plate directly on the hull, not on a stringer. The force acts on the hull itself and is spread out over a decent sized area. If I understand the installation of the gyros correctly, they attach to the stringer itself and impart the force against the stringer. My question still is where the force acting on the stringer is lateral and angular, is there a danger of the stringer-hull joint cracking or separating?
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Old 02-22-2014, 08:03 AM   #54
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My question still is where the force acting on the stringer is lateral and angular, is there a danger of the stringer-hull joint cracking or separating?
On a new build the NA and builders should be able to get this right. A lot of the points made on structural integrity for gyros could easily apply to poor designs and or applications for rudders, engines, passive stabilizers or anchor rode connections.

Similar discussions were common a few years ago when pod drives were in their infancy and long before that stern drives. New concepts always have their doubters, in the case of gyros I am one but not for being (un)able to design a suitable structure.

For new builds such as a Fleming, OA, Westport or Marlow gyros seem worth a look. Hull appendages create external strike potential and the fewer the better IMHO. I was reviewing a large vessel recently that had 30ft2 stabilizers, the thought of one of those striking a log or container in the open ocean is not pleasant.
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Old 02-22-2014, 08:10 AM   #55
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It would be great to hear from someone first hand who has a gyro in their boat. I'd love to hear how they actually perform. We have a bunch of people here with fin systems, but it appears nobody with a gyro?
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Old 02-22-2014, 08:25 AM   #56
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It would be great to hear from someone first hand who has a gyro in their boat. I'd love to hear how they actually perform. We have a bunch of people here with fin systems, but it appears nobody with a gyro?
Yes, and a visit to Seakeepers website is worthwhile too. It is surprising how many builders appear to be on board.
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Old 02-22-2014, 04:18 PM   #57
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I have talked with two guys who have them on their big sport fishing boats, which I believe was Seakeepers original target market. Both were installed as part of the original build as I recall. They both loved it, the primary purpose being stability while on the drift or slow trolling speeds ( it is very rare to see fin stabilizers on a sport fisher).
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Old 02-23-2014, 12:09 AM   #58
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As far as the loads go, when I looked at sea keepers web site days ago there was technical info that showed the largest load in the worst sea state of 23 kN in the z axis. All the the other loads were in the teens. Not near as much as I had expected.

On a dying cell phone on a particularly boring ferry ride so not able to link right now. I'm sure the OP, RickB has already read it though.
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Old 02-24-2014, 07:08 AM   #59
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It would be great to hear from someone first hand who has a gyro in their boat. I'd love to hear how they actually perform. We have a bunch of people here with fin systems, but it appears nobody with a gyro?
People with gyros don't need no stinkin trawler forum
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Old 02-24-2014, 10:59 AM   #60
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People with gyros don't need no stinkin trawler forum
Sometimes an eye opener is a good thing. There are some on this forum who still feel the best head is a bucket.
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