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Will a bilge keel improve rolling at sea?

 
 
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Old 09-08-2006, 12:58 PM   #31 (permalink)
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It was high on brackets and this rather small yacht (72ī) only has one deck above so it was probably in the ideal position. I tried to find some info on the weight today without success, but my guess is around 600-800 kg...
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Old 09-08-2006, 01:37 PM   #32 (permalink)
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Great knowledge coming from you guys ,most appreciated thanks.I just like to read through all this and I must say its very informative.From what I can figure out a good pair of stabilizers would have done the trick .But sure one has to plan for that .So I guess he will install those bildge keels.
Will show you some pics next week.

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Old 09-08-2006, 03:31 PM   #33 (permalink)
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Quote:
Originally Posted by AMG
There was a stabilizer system with a weight sliding sideways on rails. Maybe from KoopNautic, and I have seen it on a Moonen 72 where it was on the forward bulkhead of the engine room.

It was also working at anchor, but created some noise and it was scary to be in the engine room when it was moving forth and back...
So, when you first described this I was thinking about a big bar with the weight just freely moving back and forth as needed. I thought about it again and that seems a little out of control... So, how was it controlled if it was? A gyro determining which way a cable should pull the weight and how far and fast?
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Old 09-08-2006, 03:50 PM   #34 (permalink)
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Yes Bill, this is about the right description, canīt remember if it was a chain or cables, maybe both. So it was moving in advance of the movements of the yacht. Similar to fin stabilizers which are also moving in advance to keep the boat from swinging too much. The stabilizers (or the gyro control box) can only predict the next wave to behave as the previous and as the sea is never regular, they get out of rythm once in a while...
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Old 09-08-2006, 11:13 PM   #35 (permalink)
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There are also Fram anti roll tanks which can be passive or active, the passive relies on a tuned length tube and valve arrangement, something to do with the time lag of the mass of water in the tanks and active which has a huge pump. I believe this system was installed on Eco
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Old 03-28-2007, 11:53 AM   #36 (permalink)
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Enclosing active roll-fin stabilizers

The point of protecting active fins is a good one. However, ensure the protection you are installing does not interfere with the flow of water around the active fin. The fins rely on smooth water flow, just as a sail relies on undisturbed air flow.

There are new active and passive stabilizer types which mount to the transom. Since they do not protrude below the propellers and rudders they won't ground. From the transom roll pitch and yaw can be controlled under way and at anchor. Additionally, since they are located aft of the propellers they don't create disturbed water and propeller cavitation which induce hull vibration.

Smaller yachts should not require bilge keels if using the transom mounted system.
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Old 03-29-2007, 02:04 PM   #37 (permalink)
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Quote:
Originally Posted by OceanFlyer
There are new active and passive stabilizer types which mount to the transom. Since they do not protrude below the propellers and rudders they won't ground. From the transom roll pitch and yaw can be controlled under way and at anchor. Additionally, since they are located aft of the propellers they don't create disturbed water and propeller cavitation which induce hull vibration.

.
While it's true that there are now integrated stabilization systems available that control pitch, roll and yaw effectively, and several zero-speed roll control solutions...I can't quite fathom what kind of transom effectors you are referring to. Any links or other info on what they look like?
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Old 03-29-2007, 02:25 PM   #38 (permalink)
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Quote:
Originally Posted by BMcF
While it's true that there are now integrated stabilization systems available that control pitch, roll and yaw effectively, and several zero-speed roll control solutions...I can't quite fathom what kind of transom effectors you are referring to. Any links or other info on what they look like?
Itīs been discussed earlier in this thread. Here is one supplier;
http://www.quantumhydraulic.com/ridecontrol.html
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Old 03-29-2007, 02:35 PM   #39 (permalink)
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Originally Posted by AMG
Itīs been discussed earlier in this thread. Here is one supplier;
http://www.quantumhydraulic.com/ridecontrol.html
Quite familiar with those..I probably should have been more specific in stating that I was curious about the 'yaw control' part of the solutions alluded to above. The winged-tabs that Quantum builds are sometimes 'slaved', in the controller, to the vessel steering (rudder position) to eliminate yaw-roll coupling in some cases, but are not used for yaw control directly.
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Old 03-29-2007, 04:39 PM   #40 (permalink)
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Transom Mounted Stabilizers

There are many ways to control all boat motion from the transom. Most are based on classic hydrofoil technology. Aircraft tail section and aileron techniques are also utilized.

The strategy is to use the force of lift generated from NACA shaped t-foils, to actively stop roll and passively dampen pitch and yaw. The effectiveness in a following sea is extraordinary, with transom mounting.

At anchor, the active t-foils attenuate roll motion and passively reduce pitch motion. This prevents the yacht from synchronizing with wave amplitude and period. This reduces roll acceleration and shortens the length of time the boat is effected by each wave cycle.

The mere fact that the hydrofoils are an added appendage under water increases drag at anchor and dampens roll, like bilge keels and flopper stoppers.
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Old 03-29-2007, 04:52 PM   #41 (permalink)
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OK..I actually had seen that site but it's been a while. The systems I've seen in service that deal with active control of pitch, roll and yaw simultaneously had multiple effectors operated by one controller; e.g. trim tabs (or interceptors), bow foils and the rudders. Some only have the trim tabs and rudders. Interesting stuff.
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Old 03-29-2007, 05:25 PM   #42 (permalink)
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Quote:
Originally Posted by OceanFlyer
Smaller yachts should not require bilge keels if using the transom mounted system.
I guess bilge keels are the most proven and trouble free motion dampers, especially if you are fishing, where the transom mounted will add more things to tangle...

Among all the words on that website, I could have missed if there are speed limitations and if they have speed advantages or is slowing the yacht down? For how long has these transom foils been produced and is it your company or do you have first hand experience of using them?
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Old 03-29-2007, 07:00 PM   #43 (permalink)
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Lars, forgive me. I know you just set a trap for OceanFlyer and BMcF, but I can't let this continue...

The question was asked... "Will a bilge keel prevent rolling at sea?"

I can tell you what it won't prevent... ME, from rolling my eyes at a couple of members who have jumped on an old thread with a specific interest and greater than average knowledge in the area of hull stabilization. One must ask, why do you two characters have so much interest in this and why are you all-of-a-sudden talking about here? It's not like you've discussed anything else...

Gentlemen, we take a zero-tolerance approach to promotion on YachtForums, but more specifically... we take a hardline approach to businesses posing as consumers. If you have a product or a technology, issue a press release or commence an ad campaign. But "leading" is a form of fraud and we will not tolerate this kind of conduct. Furthermore, we WILL take measures to disclose the same.

The link to your site has been removed and your memberships are about one keystroke away from deletion. If you try to pull this stunt again, I WILL index this incident/thread with our technology and it WILL come to the top of a search in Google, Yahoo & MSN. And make no mistake... the careful wording of an editor with 10 years of hydrodynamic development should prove sufficient to challenge any benefit you're claiming.
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Old 03-29-2007, 08:57 PM   #44 (permalink)
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Excuse me..but how did I get lumped in to this rebuke? I saw the recent post, in a subject I find quite interesting, and responded with a request for clarification because I could not fathom what the 'solution' was that was being desribed. The link posted by AMG, to a vendor's website/product by the way, was clearly not 'it'.

The thread in question has had numerous posts regarding active versus passive solutions. I read them all with great interest back when I first signed on.

Nowhere in my own posts did I make any attempt to promote anybody's product. I simply commented, and quite generally so, on what I knew to be solutions out there that did what was described by OceanFlyer. Certainly you are not saying that knowing something about a subject precludes one from posting about it..or are you trying to imply that this was somehow a 'joint effort' between myself and OceanFlyer? I guess we are all assuming that Oceanflyer and the link provided are closely connected..which is why I purposely limited my last response after seeing the link and recognizing that a line had probably been crossed..but not by me.

My posts on this forum have been largely limited to a few on the subject of multihulls..another subject in which I have a lot of interest and to which I was pointed by a long-standing member on this forum....and why I then joined it.
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Old 03-29-2007, 09:54 PM   #45 (permalink)
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Quote:
Originally Posted by BMcF
I guess we are all assuming that Oceanflyer and the link provided are closely connected..which is why I purposely limited my last response after seeing the link and recognizing that a line had probably been crossed..but not by me.
My apologies Mr. McFann. Your post looked like a leader based on response time and the level of knowledge conveyed rather quickly. This was compounded by an immediate follow up by a new member, OceanFlyer, that was directing focus to his website, technology, product. It's a classic scenario.

What I can say with with absolute assuredness is OceanFlyer is directly connected to the link he posted. Because I recognized your name and associated it with hydrofoils and stabilization systems, an area of specific and related expertise to OceanFlyer's business, it was a fair assumption that you may be working together.

Whatever the case, I will end this here with a formal apology to you... and I am banning OceanFlyer's IP address & removing his membership.
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