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  #571  
Old 01-03-2013
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Re: German Yacht Magazine Article on Full vs. Fin Keel

Quote:
Originally Posted by BryceGTX View Post
So I should check a 33 is bigger than a 30???? Who cares?

Paulo.. given that the three boats in question were 31ft, 29 ft and 30 foot.. why in the world would you suggest than anyone would compare these boats to a 33?

Who cares that a 33 is more stiff or faster or whatever.. clearly it is in a different class...
Bryce
Sometimes is difficult to communicate with you. I have said that the modern 30ft they had used for comparison (a Jeanneau 30) was particularly tender, I give as example the 33ft from jeanneau as a boat much more stiff, even from the same line and brand

You said that the Jeanneau 30 was a good example in what regards the average stiffness of modern 30fts and I showed that you were wrong, that in fact I cannot find one as tender and posted the B/D of almost all 30ft on the market.

If that comparison was made with a Dehler 29 or a A31 the results would be very different, not in what regards sea motion but in what regards upwind speed. The main reason of the poor performance of the Jeanneau 30i upwind has nothing to do with being a fin keel or a full keel but with the boat being tender, exceptionally tender.

The better performer upwind on that test was not from the full keel (Vindo 40) but the one of other fin keel, the smaller boat, the Halberg-Rassy 29.

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Paulo
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  #572  
Old 01-04-2013
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Re: Full or fin keel?

I've owned full keeled boats with encapsulated ballast, one off fin keeled with keel bolts, modified fin with bolts . It's been mentioned several times in this thread full keel boats have encapsulated ballast (not always true) which runs the risk of complete ruin in a hard grounding and bolt on keels do not. Given I just spent my kids inheritance on a high aspect bulbed fin keel boat with encapsulated ballast (yes they exist) is there any data to support these statements.?Is this just ancedotal. Would think just like a properly engineered spade rudder can be stronger than a skeg hung one -a properly engineered fin with encapsulated ballast should be as strong or stronger than keel bolted.To the point that the grounding would have to produce whole structure failure of the vessel regardless of encapsulated or bolted. ?Are Shannons and Outbounds lousy boats.
P.S.- right on Paulo -having lived with both beasts unless thin water precludes it's a fin that's a better choice- just like we don't see many gaff rigged schooners being made these days unless we are in Lundenburg and see more solents modern fin keel boats can tract better, sail better and are as safe or safer in bad weather if properly designed and constructed. One post was kind enough to have a link that allowed comparisions.
please keep this thread going
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Last edited by outbound; 01-04-2013 at 12:23 AM.
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  #573  
Old 01-04-2013
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Re: Full or fin keel?

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Originally Posted by Faster View Post
If a full keel was really the absolute optimum for offshore sailing we'd still see the Suhali's on the Volvo Ocean Race. (and I imagine a few of those crew, crawling soaking wet into an equally wet berth might well wish they'd chosen that ride from time to time)
While most of your post was thoughtful and well said (as usual), I have to call you on this analogy. Few things are "absolute" in this world, and I don't think anyone has claimed that the advantage of a full keel is speed. Don't know what "Suhali's are, but I assume they had an ample keel. On any race boat (offshore or otherwise), I think the priority is going to be speed. Not - sea kindness (as you point out), tracking, safety, shallow draft and certainly not durability after running aground. I don't think the OP was asking about offshore racing.

Last edited by L124C; 01-04-2013 at 05:47 AM.
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  #574  
Old 01-04-2013
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Re: Full or fin keel?

"Suhali" was the name of Robin Knox Johnson's boat that won the first solo nonstop round the world race.

It was a heavy, old-fashioned, full-keeled, Colin Archer design that survived the race where all others were eliminated due to material failures or insanity in the case of Donald Crowhurst. It averaged 4 knots per hour - the classic 4ksb.

Last edited by jameswilson29; 01-04-2013 at 06:20 AM.
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  #575  
Old 01-04-2013
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Re: Full or fin keel?

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Originally Posted by L124C View Post
While most of your post was thoughtful and well said (as usual), I have to call you on this analogy. Few things are "absolute" in this world, and I don't think anyone has claimed that the advantage of a full keel is speed. Don't know what "Suhali's are, but I assume they had an ample keel. On any race boat (offshore or otherwise), I think the priority is going to be speed. Not - sea kindness (as you point out), tracking, safety, shallow draft and certainly not durability after running aground. I don't think the OP was asking about offshore racing.
Thanks.... and yes, that statement may well have been an exaggeration (although there are a few W32 posters here that might not think so...
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  #576  
Old 01-04-2013
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Re: Full or fin keel?

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Originally Posted by L124C View Post
... I don't think anyone has claimed that the advantage of a full keel is speed. Don't know what "Suhali's are, but I assume they had an ample keel. On any race boat (offshore or otherwise), I think the priority is going to be speed. Not - sea kindness (as you point out), tracking, safety, shallow draft and certainly not durability after running aground. I don't think the OP was asking about offshore racing.
Sea-kindness has not to do with the type of keel but with the hull design and boat weight (inertia). In what regards tracking a well design fin keel can be as good as a full keel and certainly they point better and provide less drag.

Regarding draft, for the ones that need it modern keels offer swing ballasted keels that are very similar in performance with fin keels and offer a smaller draft than full keels.

You call it performance I call it a better sailing boat (a boat that sails better) and that is not important only to racers but to all cruisers.

Regarding durability I don't see why a boat with a fin keel would be less durable than a boat with a full keel.

Regarding being more resistant to grounding I guess you are right even if each case is a case. Anyway take a look at this videos. Do you really think that you need more resistance than this? Take into consideration that is a very light performance production cruiser with a big draft (2.30m). Normally mainstream production cruisers are more heavily built and have less draft.



Skerries boat "Raging Bull" crashes into the rocks during a storm from Silverscreen Media on Vimeo.



Regards

Paulo
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  #577  
Old 01-08-2013
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Re: German Yacht Magazine Article on Full vs. Fin Keel

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Originally Posted by PCP View Post
I have said that the modern 30ft they had used for comparison (a Jeanneau 30) was particularly tender, I give as example the 33ft from jeanneau as a boat much more stiff, even from the same line and brand

You said that the Jeanneau 30 was a good example in what regards the average stiffness of modern 30fts and I showed that you were wrong, that in fact I cannot find one as tender and posted the B/D of almost all 30ft on the market.

Paulo
Clearly comparing a 33 foot to a 30 foot boat does not make sense. On the other hand, there are 30 footers with more beam that would result in considerably more stiffness.

The problem is that you consider stiffness to be a requirement for a good rough water boat.. clearly few agree with you. And this video shows why.

In spite of the fact, the Sun 30 is probably the stiffest of the three boats for the simple reason that it is a more modern flat hull. The other two will invariably be more v-shaped less stiff hulls.

The video pretty much states what this thread is about.. even if you do not agree with it.
Bryce
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  #578  
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Re: Full or fin keel?

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Originally Posted by PCP View Post
Sea-kindness has not to do with the type of keel but with the hull design and boat weight (inertia).
Paulo
Really?? I think keel design is mostly what this thread is about and keel design has been shown to be important.

BTW.. weight and inertia are radically different things.
Bryce
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  #579  
Old 01-08-2013
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Re: Full or fin keel?

A friend of mine decided to compare his Calalina 30 to my boat, same LOA, same LWL....lots of other differance....the final results surprised him
Captian Cicero
Ballast to weight ratio 28%
Max hull speed 6.7
Displacement length ratio 428.57
Sail area disp' ratio 13.15
Capsize screening ratio 1.42
Motion comfort ratio 46.71

Catalina 30
Ballast to weight ratio 41.18%
Max hull speed 6.7
Displacement length ratio 291.43
Sail area disp' ratio 15.17
Capsize screening ratio 1.99
Motion comfort ratio 23.99

I used SloopIT - Boat performance calculator
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  #580  
Old 01-09-2013
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Re: Full or fin keel?

Do not remember which number, be it capsize or comfort ratio, but was not one of them "hood" a naval architect that came up with that ratio. Later said it was good, but at the end of the day with some of the newer designs not as useful as with past designs. Not saying that that ratio should be thrown out per say, as it favors longer/skinnier designs vs some of the fatter hulled designs of today. Rather apparent that hull design will potentially make or break a design depending upon useage as to if it will or will not work for the end user. Not just fin vs full vs bilge vs CB or some combo there of!

The more I type, I believe it is the motion comfort ratio number. Even short will come out on the lower side of things than width. As a 30'L 10' wide boat will come out with a worst number than a 60' x 20', even tho the length.width ratio is equal. I am also recalling disp being part, maybe that needs to be equally doubled to get the same ratio, where is going up double in length, usually (typically) quadruples or equal the disp of the boat. That would be an interesting plug in numbers to see what or if one can get different equal length and beam to equal....

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