Fin stabilisers with curved fins, new from Sleipner, 50-60 foot boat bracket

[MapisM]

Point of order matey. I never go for the man, with the exception of this thread. You went for the man, so you set the ground rules. I'm merely following them (in this thread only).
"You've made your bed", if I may use an EN expression, and have lost the moral right to protest

Nope, I didn't make any bed. I posted a joke, inclusive of a smiley, and you perfectly know that it wasn't meant to "go for the man".
In fact, I can't think of any better proof of this than your own statement which followed: "Agreed - that page is marketing BS!"
Which I must admit was refreshingly honest, for a change vs. your obsessive statements, further repeated also in this thread, labelling each and every thing CMC says as MBS.

But now, you are using this as an excuse for REALLY going for the man, and in your last post you passed the fine line marking the borders of offensive statements - line which you already approached with the previous post.
Btw, without even being man enough to understand that tagging all the FDC crew of not having any STAR experience, without knowing for sure whether this is true or not (and as it happens it isn't, because I for one have been on other STAR equipped boats, as already mentioned), is something for which apologies would have been in order REGARDLESS of whether your guess was true or not.

So, I'm not going any further, also because what I was more interested in were two thing:
1) how would you qualify the misrepresentation of sway effect as something contributing to sea sickness, after you recognised that it isn't ("Yes in a BA or Match, you never feel much yaw or sway. But feeling it isn't the point", "in swaying the boat you will not feel the sway", "I repeat that you will not feel any elimination of sway", "It was never the main event anyway; it is a mere sideshow").
But you skipped that point altogether, so I take it as a tacit consent that "fraudulent representation" was the appropriate terminology.
Maybe you should advise Sleipner, in this respect.
2) understand whether I was being so stupid to miss any big factor on the topic of the fins positioning.
Now, your ridiculous reply on the requirement which is not met by the second fin of my drawing, together with your attempt to prove "scientifically" that a vertical force component applied to the keel of a boat can contribute to reducing its roll (which is something that beggars belief, and I'd be just curious to hear if anyone else agree with such concept), to my simple mind is more than enough to prove beyond any reasonable doubt that I had no reason to fear of being stupid.

Bottom line, sorry to disappoint OF who was enjoying the competition, but it's over.
Jfm has got the biggest willie, I can live with that.

 

[Deleted User YDKXO]

2) understand whether I was being so stupid to miss any big factor on the topic of the fins positioning.
Now, your ridiculous reply on the requirement which is not met by the second fin of my drawing, together with your attempt to prove "scientifically" that a vertical force component applied to the keel of a boat can contribute to reducing its roll (which is something that beggars belief, and I'd be just curious to hear if anyone else agree with such concept), to my simple mind is more than enough to prove beyond any reasonable doubt that I had no reason to fear of being stupid.

Come on Mapism, keep going! Surely it's not a vertical force component that jfm is referring to but a force normal to the axis of the fin which acts over a lever arm (shown by the double ended arrow) to the roll axis so I have to agree with him, I don't see why a fin attached to the keel wouldn't contribute to reducing roll. In any case, just as a point of order, presumably the fin starts actuating when the boat has already started to roll in which case a fin attached to the keel won't be exactly vertical under the roll axis?

 

[Tender_aft]

No, keep it going on the open forum. I'm enjoying this immensely, especially the physics. It's great to see 2 forum heavyweights slugging it out to a standstill

....but, with no offence intended to either of them....are they just armchair amateurs with a strong opinion or do they actually know their stuff?....It'd be nice if we could get input from a professional expert in this field, so we can see whether he/she would bash their heads together and tell them to stop it, or validate one of them (however, experts can be biased so just consider this a rhetorical post).

....steps back to sidelines to let the fighting recommence.

 

[MapisM]

Come on Mapism, keep going! Surely it's not a vertical force component that jfm is referring to but a force normal to the axis of the fin which acts over a lever arm (shown by the double ended arrow) to the roll axis so I have to agree with him, I don't see why a fin attached to the keel wouldn't contribute to reducing roll. In any case, just as a point of order, presumably the fin starts actuating when the boat has already started to roll in which case a fin attached to the keel won't be exactly vertical under the roll axis?

M, forget the drawing posted above, that has nothing to see with the hypothetical fin placed exactly under the keel, with a vertical shaft.
In such position, it's the curved fin that would introduce a vertical component, which just doesn't make any sense when applied to the keel.
Otoh, I understand your point of order, and I don't disagree with it. But that's another matter altogether.

Anyway, don't hold your breath, I'm sure jfm will be soon around to explain that bended fins would be better even if placed above the radar arch.
From my part, I said it's over and it's over.
I just answered your question because you've been kind enough to call myself and jfm "2 forum heavyweight", hence putting me on par with him (sort of).
But also that is now sorted.
Maybe I should have paid more attention to the emails I occasionally receive, suggesting enlargement solutions of all sorts...

 

[jfm]

Ref post #101
Oh jeeze calm down MapisM

Happy to disagree on making a bed. I have never said "each and every" thing CMC says is MBS. Just two very specific things: (a) that Swiss watch gearboxes are the reason there is no heat, and (b) that their electric actuation means a 0.6 performs like a 1.0. I made those two point in good faith, when BartW was about to spend €50k+ and was asking for comments, and I urged him to check and think carefully about those things. That's all. Calm down.

As for going for the man, you set the parameters for this thread. I don't think I have said anything factually incorrect about FDC participants, but I repeat that if they correct me I'll eat my words. You yourself have spent virtually no time on boats in STAR mode, as you have alluded to many times on here eg post #27 on Rob's Fifty Shades of Steel thread

Ref your two numbered paras:
1. I really can't be bothered with "fraudulent misrep" debate. Life is too short. All I care about is that there is a new clever stabilisation product out there. I think it's fab, but if there is some science/argument saying it's bad/so-so I'd love to hear it too. Frankly if there is a company out there that makes fantastic stabilisers and writes awful marketing material, I want to buy their product please.

2. (i) My reply on the "requirement which is not met" is not "ridiculous". It is 100% correct and critical to the physics

(ii) As for the rest of your point 2, about fins mounted on a boat's keel, you are correct here and I was wrong. I've been saying that curved fins create more vertical and less horizontal component. I already explained a couple of times that this only works well, beating the flat fins, if they are towards the chine. The closer to the chine the better. I also explained that if you move them too far away from the chine, they become WORSE than flat fins. Now, as you saw and I missed, the crossover point is earlier. As you have explained, if you move them merely as far as the keel, and not even as far as beyond the keel, their advantage is lost, and becomes a disadvantage. The logic/physics is glaringly obvious - a force component pointing AT the roll centre cannot help, as you correctly stated. So yes, I got that point 100% wrong - I missed that simple bit of physics . In my only slight defence, this is complex stuff, I have a day job, I'm posting in late evening, and of course this doesn't change the "main event" here that curved fins if mounted in the usual position on the hull are a big improvement over flat fins. (It would be much better to have discussed this all in a pub with a sketch pad!)

EDIT, I wrote 2(ii) above before reading MapisM's #104, but no matter, we are now in synch on that point and he is correct on it

 

[petem]

M, forget the drawing posted above, that has nothing to see with the hypothetical fin placed exactly under the keel, with a vertical shaft.
In such position, it's the curved fin that would introduce a vertical component, which just doesn't make any sense when applied to the keel.
Otoh, I understand your point of order, and I don't disagree with it. But that's another matter altogether.

Anyway, don't hold your breath, I'm sure jfm will be soon around to explain that bended fins would be better even if placed above the radar arch.
From my part, I said it's over and it's over.
I just answered your question because you've been kind enough to call myself and jfm "2 forum heavyweight", hence putting me on par with him (sort of).
But also that is now sorted.
Maybe I should have paid more attention to the emails I occasionally receive, suggesting enlargement solutions of all sorts...

I believe big is better. I've also head that a curvy one is good too.