Choosing a Boat, Part 2 – Keel

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Following on from Length, we have hull form and keel choice. Again, the most suitable hull form and keel will be determined by your likely boat use. Be realistic with yourself! You may dream of winning races, but if you’re likely to spend more time afloat out catching mackerel or sailing down the coast then a short fin with a bulb might not make so much sense.

So what are your choices, and what are each good at?

Fin Keel

A fin keel is exactly what it sounds like. It is a keel that projects down from the centre of the hull much like a fishes fin. They vary in length and depth. Below you can see a Westerly Cirrus sporting a fin keel.

finkeel
Fin Keel

Fin keels are preferred by those looking for performance from their boats. Their relatively low wetted surface area means they are good in low winds. Their short length creates a natural pivot around which the boat may change direction making them responsive, easy to tack through the wind and fast around buoys. However, these attributes aren’t necessarily suitable for cruising or ocean passages, but for racing and day sailing they make for a fun boat!

Other drawbacks include the deep draft and their inability to go aground. These qualities restrict the places you can explore. If you like to visit beautiful, secluded drying harbours such as those found in Porthleven, Mousehole, Polperro, Looe, etc. or sailing up estuaries like the Helford or the Fal then they may not be for you! They can be fitted with ‘legs’ which allow them to take the ground, but they must be carried on board, take up space, and are generally a pain. If the fin is too short or the boat weigh not distributed well then a fin keel with legs can topple forward or backward. Not pretty.

Twin Keel

These are often referred to as bilge keels, which in my opinion is wrong. A twin keel boat has two fin like keels protruding either side of the centre line. This Westerly Centaur has twin keels.

centaur-twinkeel
Twin keeled Centaur

Twin keeled boats can dry out happily, however drying out in soft deep mud may put undue stress on the keels as they are are not parallel to the forces of gravity; they often splay out. However on firm mud, silt and similar they can sit happily every tide. For this reason they are great for visiting drying harbours and estuaries.

Their sailing performance is fairly dependent on the yacht designer’s skills. Each keel must be aligned parallel with the direction of flow of the water over the hull or hydrodynamic lift will be created and this will slow the boat down. They often like to be sailed upright for these reasons.

They also don’t point to windward quite as well as a fin keeler. This is due to the increased drag caused by the two keels, and also due to the leeward keel being at an increased angle of attack to the water, which also produces more drag.

sailandkeelforces

Bilge and Triple Keels

Strictly speaking bilge keels (or bilge plates) are fitted to boats with a centre keel, forming a ‘triple keel’. The centre keel is often a long keel as in a westerly 22 or on the Trident 24.

w22-triplekeel
Westerly 22 twin / triple keel

This keel configuration had died out somewhat in recent years, and most modern hulls are now twin keel. Triple keels have more turning resistance due to the long centre keel which makes them less agile, but means they hold their course well in a following sea. They are often very seaworthy for these reasons.

They can also take the ground and as the Westerly 22 in the photo above demonstrates, have a very shallow draft.

Long Keel

Favoured for long ocean passages long keel boats have a relatively long deep keel with ballast low down and evenly displaced along the keel.

halcyon27-longkeel
Halcyon 27 long keel

Boats like the Halcyon 27 above have a large wetted surface area, so aren’t so good in light winds. The high directional stability means they are great in a seaway with less chance of broaching. Broaching is the sudden change of direction induced by sharp changes of forces on the boat from waves and wind. The directional stability also means that they can be difficult to manoeuvre in a marina however!

Another plus for the long keeled boat is that they are less likely to snag ropes or debris due to the protected keel and lack of protuberances; another reason why they are so beloved by blue water ocean sailors.

Similar to a fin keel, drying out requires sea legs, but unlike the fin keeler a long keel boat is unlikely to tip forward or backward.

A note on Heaving To

‘Heaving to’ is when a boat tacks across the wind but doesn’t release the jib/genoa. This results in a ‘backed foresail’. Under such conditions different keel configurations behave differently. Another attribute of the long keel that makes them so appealing to the ocean yachtsman is that they heave to very well and sit pointing somewhat to windward making little headway and can weather out a blow this way.

Triple keelers like the Westerly 22 can also heave to with good success. Fin and twin Keelers tend to not fare so well. Their short keel length means their bows tend to blow off the wind leaving them beam on to the sea making lots of leeway.

Traditional Cornish fishing boats often have long keels and used to heave to when pulling nets or crab pots. Mizzen masts right at the back of the boat used to help keep them bow into the waves too.

Summing Up

Twin, bilge and triple keelers can be kept in and visit tidal estuaries and drying harbours. They are easier to transport on trailer or HIAB flatbed lorry. Other keel forms will need support or a cradle in order to move them. They may not point so close to the wind as fin or long keel boats, but they can live on cheaper moorings and can be seaworthy.

Fin keelers are the preserve of the racers and performance sailers. If every degree pointed to windward matters to you and you like screeching around buoys in races these boats are for you. There are plenty of cruising yachts with fin keels around the solent, an in deep estuaries on reasonably priced swinging moorings that don’t dry out, so if you imagine your cruising grounds mostly consisting of these kinds of places a fin keel may well be a good bet.

If you’re planning on spending your days on long ocean passages then a long keel would be ideal.

So, which choice for me?

My closest coast is the North Somerset coast. It’s know for its huge tidal range and its mud. However, cheap moorings can be found if you have a boat that can dry out or sit in mud. In order to make it down to Cornwall I will have to sail down the perilous North Devon and North Cornish coasts. Safe havens are few and far between on those coasts and many of them dry out. For example Minehead, Watchet outer harbour, Clovelly and basically all the others!

Also, when we get to the Scillies it will be great to be able to not worry about going aground or even to be able to go aground on purpose. So I’m going to be looking for a twin or triple keel boat.

Anecdote of the Day

I strayed off the path and was tempted by a lovely looking Hurley with a long/fin keel. This conversation with Kurt ensued;

Jamie, [29.09.16 13:29]
I’m now thinking a fin keel hurley wouldn’t be so bad.

Kurt, [29.09.16 14:37]
No

Jamie, [29.09.16 14:38]
Only an extra 3/4’s of a foot. Legs are a pain though.

Kurt, [29.09.16 14:38]
You want to be able to go aground anywhere and not worry

Jamie, [29.09.16 14:39]
But the sea keeping qualities are nice. On a hurley they’re kind of designed around that keel. Narrower beam and big heavy keel means boat sits low in the water which gives you the standing height in the cabin. Not sure how they’d translate to a bilge keel?

Kurt, [29.09.16 14:40]
You’ll regret it

Jamie, [29.09.16 14:40]
I guess you’ve experienced this with your old Porthleven boat?

Kurt, [29.09.16 14:42]
Ha!! It’s a Pain in the arse. And then you’re always worried that a leg will sink into a hole or something. Don’t do it

Jamie, [29.09.16 14:42]

OK.

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