Keel tyoes: handling & seas

[ianj99]

I was wondering if one type of keel is better than another as regards handling and sea state.

For example, the west coast of Scotland I'm told, is prone to short steep seas. So would a long keel be better or worse or no different to a fin keel in these seas?

Ianj

 

[Krusty]

South of Mull of Kintyre, I doubt if the keel makes much difference, but North of it, I would rather have a short keel.
My preference has nothing to do with sea-state, but handiness: a boat that will turn in little more than her own length bestows greater confidence at close-quarters.
Many of the best and most secure anchorages are quite tight to enter and to manoeuvre within. The same goes for those (few) harbours which now have pontoons.

 

[Deleted member 36384]

Its Not Just A Question Of Keel Shape

Your question is difficult to quantify as sea kindliness can be found in most keel and hull shapes. Its also very dependant on length and displacement.

Around 25' a yachts motion in moderate seas will be much different than a yacht more than 30'. In very general terms a fuller keel on a heavier displacement yacht will cut through the waves with less motion than a lighter fin keel yacht.

However, a Contessa 32 which has a fuller keel, is a very wet boat compared to a Sigma 33, which is fin keeled. The Contessa has a good turn of speed, like the Sigma but unlike the Sigma will tend to part the waves as apposed to ride over the waves. This parting action throws a lot of water aft into the cockpit when close hauled. In my opinion the Sigma 33 is the better boat.

From about 36' upwards the keel type begins to have less of an impact on a well designed boat. They can all take a chop or big swell relatively straight forward.

I don't think that the West Coast of Scotland can be classified as neatly as your statement suggests. The North Sea however does fit your description much better.

Piotaskipper makes a point about the ability of a fin keel to turn tighter than a fuller keel. It is certainly easier but if you know your boat you can turn it on its keel within a boat length. I have a 41' boat with long keel, skeg, inability to go backwards but she can be spun around on her own length effortlessly if you know what to do.

What are you looking to do in your boat?

 

[vyv_cox]

However, a Contessa 32 which has a fuller keel, is a very wet boat compared to a Sigma 33, which is fin keeled. The Contessa has a good turn of speed, like the Sigma but unlike the Sigma will tend to part the waves as apposed to ride over the waves. This parting action throws a lot of water aft into the cockpit when close hauled. In my opinion the Sigma 33 is the better boat.

Surely this is absolutely nothing to do with keel configuration, but everything to do with hull and topsides shape? Many 1970s IOR-influenced designs had pronounced tumblehome whch tended to attract water around the topsides until it reached the toerail. It then ejected itself aft, usually landing on the helm.

One very wet boat like this is a Fastnet 34, otherwise a very pleasant boat. Every wave in a seaway finds the helm, whereas my Sadler 34, with reasonable flare to the bows, throws them all outwards, with the result that a wave on deck is a rare occurence. Keel configuration of both is very similar.

 

[Deleted member 36384]

Surely this is absolutely nothing to do with keel configuration, but everything to do with hull and topsides shape?

I do not disagree with your observation. The point is that two keel shapes both deal with a choppy sea comfortably but one throws water at the helmsman the other doesn't.

Thanks for clarifying the position on the keel.

 

[Quandary]

Keel types

Keel choice is influenced by geography but not in the way the OP implies, modern, deep hydrodynamic lead keels are more efficient with low drag and effective uplift to windward, they are the choice on Scotlands West Coast because there is plenty of deep water almost everywhere, so Scots have not needed to resort to shallow draught or bilge keels like sailors in Wales and parts of England. There are quite a few older long keelers like the Contessa 32 about but this is because they are classics and really pretty boats, the downside is low freeboard, lower speeds and less manouevreability often with narrow beam giving less accommodation. Much like the Morgan my wife wants in place of her MX5.
As time passes the fin keel is almost universal though there are modern multi keeled and twin ruddered boats appearing.
The choice to be made today is shape, depth, and material, there are still quite a few new boats with simple tapered iron fins like the Sigmas of thirty years ago but this is to do with cost of production rather than performance in use.
Sea kindliness is not directly a product of keel type but of hull shape as Vyv describes, dryness is not necessarily a consequence of high freeboard but again of hull shape as evidenced by boats like the very wet J35. Sea kindliness and directional stabilty are not entirely the preserve of long keelers but the more accommodation you squeeze into a given length. the fatter and less efficent the shape.
While I like sailing I can get bored after a 6 or 7 hours so I like a fast boat to get me to my destination, however if you are happy at sea for days on end then a 'soft' motion is probably more important.