Vertical Bilge Keels

gandy

gandy

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Hi,

Descriptions of some boats emphasise the advantages of bilge keels splayed out and in some cases toed in as well (Centaur, Virgo Voyager, Hunters, Pandora?). Others have vertical keels, and keep quiet about it.

Does this design difference actually reflect real-world sailing performance? For example does a Centaur sail better than a Colvic (or other similar boat with vertical keels)?

Tony S
 
The designer of the Kingfisher range of yachts, Rags Nierop, had definite views on the splaying and toe-in of twin keels but I regret I can't lay my hands on it at present.
The K30's from 1964 t0 1966 had noticeably splayed keels (about 15 degs each from upright). Later boats from 1967 to 1978 had less splay (about 7 degs; but performance is difficult to evaluate because other changes were made to the keels, skeg, rudder and ballast. I believe in both cases the keels are parallel.
 
Wasn't the splayed nature of the Centaurs keels the reason given for some of the keels getting rather wobbly? Or am a repeating an nautical myth?
 
The general belief is that splayed keels sail better but they have the disadvantage of having to be bolted onto the hull. Vertical keels are moulded on (they are vertical so that they will come out of the mould), have the advantage of being stronger and not having the complication/weakness of bolts. If you are really that worried about performance, you wouldn't have a bilge keeler of either type.
 
Re: Vertical Bilge Keels - Toe-in?

I can see the definate advantages of splayed keels over vertical. (ignoring the mechanics of it).

But toe-in, surely this must cause considerable hydrodynamic drag when sailing downwind, or under power? ie boat upright.

or is the toe-in minimal?

kev
 
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Wasn't the splayed nature of the Centaurs keels the reason given for some of the keels getting rather wobbly? Or am a repeating an nautical myth?

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That's what I'd heard as well, specially if they're drying and refloating on soft ground. All those I've seen for sale have had reinforcements added.

Tony S
 
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I thought the idea was that splayed bilge keels are vertical when heeled (or rather, the leeward one is)

- Nick

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Yes, the leeward keel has a proper grip on the water and the windward one increases the righting leverage as it moves outboard to windward of the effective centreline. Who needs canting keels? Or winged keels?

The same principal apllies to twin rudders in that you always have a surface with some grip on the water.
 
[ QUOTE ]
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Wasn't the splayed nature of the Centaurs keels the reason given for some of the keels getting rather wobbly? Or am a repeating an nautical myth?

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That's what I'd heard as well, specially if they're drying and refloating on soft ground. All those I've seen for sale have had reinforcements added.

Tony S

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When we were looking at buying a cruiser between 26 and 28 foot, the Centaur was obviously on our 'Must View' list, however we were warned away from them by a Marine Surveyor friend because of the inherent problem with the splayed Bilge Keels. It is a fact that most Centaurs that take the bottom on a regular basis have been re-inforced...think about it...a deadweight sitting on to two plates bolted through a Fibreglass panel (albeit heftily laid up), the stress is going to be enormous, hence the need for re-inforcing of the Centaurs keel stubs.

The penalty that you end up paying with a straight bilge keel (as per the Cobra 850) is anything more than 20 degrees heel and you start making more leeway than you make headway.

As has been said, if you wanted performance, then you probably should not be considering Bilge Keels!
 
Hundreds of Sadller 29s out there with splayed bilge keels and no problems. Double hull and massive keel bolts probably help. Also the keels have an asymetrical areofoil section so that the leward keel develops lift to resist leeway. Mine goes to windward Ok but the windward keel starts to slam when heeled too far as the air gets under the keel root.
 
Of the bilge keelers I've sailed, those with vertical keels have been notably worse performers, seriously bad in some cases. But they have also been older boats, arguably less efficient sailors in other respects.

Splayed keels also has the advantage of a wider base when going aground, less inclined to topple on an uneven surface. But they are notorious as a source of weakness - a double line of keel bolts is a must. That is why, for example, Kingfisher yachts have tended to last better than Westerlies of the same period.
 
thousands of hunters around, never heard of a problem with keels, only heard about the well documented and easily fixed westerly probs.
as for the people stating if you are worried about performance you wouldnt consider a twin keeler. i wonder what expierience they have to back up this statement, have you sailed the hunters/moodys t/keelers?
 
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Wasn't the splayed nature of the Centaurs keels the reason given for some of the keels getting rather wobbly? Or am a repeating an nautical myth?

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No it was inadequate engineering. And it affected other Westerlies. Moodies, with similar keel angles were OK
 
Fact!

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as for the people stating if you are worried about performance you wouldnt consider a twin keeler. i wonder what expierience they have to back up this statement, have you sailed the hunters/moodys t/keelers?

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A good Fin Keeler will ALWAYS outperform a good Bilge Keeler...certainly to windward, and 9 times out of 10 downwind. Compare two boats of the same design...be they Moody, Westerly, Cobra, Hunter...one Bilge Keeler, one Fin Keeler if sailed by helmsmen of a similar standard, the Fin Keeler will almost always be the quicker of the two boats!
 
I believe the problem was peculiar to Westerly yachts. There was obviously a design problem with the keel mountings. I've not heard of any other builder's boats suffering in the same way. Has anybody else? My own Newbridge Pioneer is berthed in soft mud and has also taken the ground on hard surfaces numerous times but shows no problems, as yet!
 
As an East Coaster, I can say that most of the Westerly Centaurs I can think of round here have had the beefing up work done years ago, as the Centaurs are getting quite elderly now. They still have to have the keels rebedded, and they do also suffer worn rudder stock bearings. Normal maintenance. I think the keel work is around 800 quid.
Thought about 15 grands worth of Mirage? Similar but better looking and a bit bigger.
And for performance keels, look at the reviews of the new Sadler 290.

I personally prefer lift keels, but you pays your money and you takes your choice (Lift Keel Sun Odyssey 35 in my case). Look at Jeanneau Fantasia, Jouet 760, Evolution 25, Jagaur 27 et al.

Jim
 
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