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Will a bilge keel improve rolling at sea?

Discussion in 'Technical Discussion' started by Francois, Sep 2, 2006.

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  1. BMcF

    BMcF Senior Member

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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.
  2. AMG

    AMG YF Moderator

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    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?
  3. YachtForum

    YachtForum Publisher/Admin

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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.
  4. BMcF

    BMcF Senior Member

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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.
  5. YachtForum

    YachtForum Publisher/Admin

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    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.
  6. Billy1119

    Billy1119 Senior Member

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    Carl, while you've already resolved the problem, in defense of BMcF, I was about to ask the same question he did regarding OceanFlyer's post.
  7. AMG

    AMG YF Moderator

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    Billy, I am defending Carl in this, since we have had similar scenarios in the past, where somebody is helping a supplier by asking innocent questions that could have been asked by anyone. Like you or BMcF.

    I became a little curious on BMcF when he commented like this;

    "OK..I actually had seen that site but it's been a while."

    The reason is I found the website to be almost new...

    But now the air is cleared I hope so let´s go on with the topic.
  8. BMcF

    BMcF Senior Member

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    Thanks for the apology Carl. No worries. Although I must confess that it was I who was actually trying to set a 'trap' so to speak. I suspected I would receive a 'smoke and mirrors' answer to my question...a question that was indeed intended to draw out what kind of wiggly bits performed such miracles. On many forums this is known as 'calling BS' and often done more directly.;)

    AMG, it would have been more accurate, then, if I had said: "I've seen those things before..."...and I'm sure that I saw them on the web some years ago. Can't say I'm in the habit of checking how old a site or URL is ...


    I think it best that I return to lurking and the odd multihull post and leave any discussion of stabilization to the experts.:)
    Last edited: Mar 30, 2007
  9. YachtForum

    YachtForum Publisher/Admin

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    I think it's fair to say you need a "roll eyes" emoticon after that statement. ;)

    Wisdom is welcome here and we embrace new technology. However, we will not let this medium be used for manipulation or self-serving promotion. We have some very respectable people on this site, a virtual who's who of sorts. You can "lump" yourself in this category too Mr. McFann.
  10. BMcF

    BMcF Senior Member

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    Why thank you kind sir..LOL..I've been told I'm a legend in my own lunchtime - perhaps that is more accurate than I 'appreciated'...:)
  11. Billy1119

    Billy1119 Senior Member

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    Lars, I do understand the logic and see how this conclusion was drawn for sure - I guess I haven't been witness to this setup much since you guys are always so on top of them and clean 'em up. :) I'll leave it alone now - moving on.
  12. MaxResolution

    MaxResolution Senior Member

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    This thread wouldn't be compl...

    Hey, I was really impressed with B-obby McF-aren's 'goading' of SkyDiver, or whatever his name really was. Yes sir-ee, the ocean can be a really unforgiving place.

    So, now I know a little more than I did about rolling at sea. And I have to wonder about the trade-offs in efficiency, as we add weight and wet surfaces. Surely this matters less with a larger boat. As to the rear stabalizers I will assume that's most noticable on a faster, smaller boat. 'Passive control' is a sales 'pitch' if I ever heard one.
  13. BMcF

    BMcF Senior Member

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    Heard that..I took a rather large slug of saltwater in that plow-in..:(

    'Passive Control' is largely an oxymoron..I would have to agree with that. However, there are certainly features or devices, bilge keels being one and paravanes another, that can add roll damping 'passively'. The trade-off between roll-damping effectiveness versus added drag (bilge keels and fin stabilizers both add drag, of course) would have to be made in every case. And then there is the 'cost' penalty of having an active solution vice a passive design feature or simple device like a paravane.

    'Rear stabilizers' are most often active trim tabs (not the 'Bennett' variety..rather large special-purpose ones), or interceptors, and are not limited to 'smaller boats' by any means. They are often employed on very large vessels. But they are not (or very seldom anyway) used on round-bilge mono hull forms, nor are they used on 'slower' boats, as you correctly noted.

    Quite a few larger yachts are being delivered with four roll stablizer fins vice two these days. It's pretty clear that in those examples, the weighting given to motion control performance is higher than weight given to cost and drag penalty factors in the trade space.

    I should also note that the added drag from stabilizer fins is not as great as is often assumed..especially for vessels that have lower transit speeds..say in the max-15 knot range. If it were such a large drag penalty, there would not be so many 'players*' in the fin stabilizer market.:)

    * I am not one of those players, BTW.
  14. kach22i

    kach22i New Member

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    I've seen a lot of fins at different places on boat hulls, but all were computer renderings by students or want-to-be designers. I had no idea before this thread that they could be part of a active control system.

    I needed the link in question to understand the topic better and learned something from it.