Bilge keels for distance yachts

[kunyang]

I had a look at a Scanyacht 39 yesterday. Lovely condition (or looked it), but I am not too sure about the bilge keels. I know we would have to go 'off the wind' a bit (even if sailing off the wind is considered a disadvantage), but are there other reasons why it might not be suitable for long distances.

What are your thoughts.



Dave

 

[ianabc]

Offshore sailboats to Brent Swain design are usually built with bilge keels. (origami steel)

Allows the boat to take the ground in protected bays at no charge!

 

[CAPTAIN FANTASTIC]

I think of more advantages than disadvantages such as when it gets stormy/rough, twin keel yacht will "slide" sideways rather than "grip" the water and hence will not lean excessively (unlike a long keel yacht). It will sail flat and therefore more comfortable ride. It will take the ground; this is a real advantage in every way. It carries more underwater and therefore will be slower, in theory, however, in practise, a bit more attention to sail trimming will near enough overcome this disadvantage. Some will argue that twin keels tent to slam against the waves; some twin keel designs do others don't. I am sure a lot of forumites will sincerely disagree with me.

 

[paul.norton]

Roger Taylor - the high latitude sailor - is currently preparing MingMing 2.

She is either a bilge keeler or triple keel vessel.

Paul

 

[lpdsn]

Roger Taylor - the high latitude sailor - is currently preparing MingMing 2.

She is either a bilge keeler or triple keel vessel.

Paul

If she turns out to be a triple keeler, will she be called MingMingMing 3?

 

[kunyang]

I just wonder how they compare i.e. stability curve, STIX etc. Can they really be as safe for ocean cruising?

 

[Seajet]

A fin / long keel design will be a lot more efficient for passage making, which is surely the point of blue water boats.

If one has a destination in mind which particularly suits a twin keeler fair enough, otherwise the keels mean extra wetted area drag.

It would be an idea for anyone setting off on blue water adventures to have well set up drying legs organised ' just in case ', but extra keels on a cruising boat seem a bit of a drag, literally.

 

[Applescruffs]

How far do you want to go ..where do you want to go??

Monsewer Winter sailed many more miles in just a couple of years in a decrepid bilge keeler than most sailors ever manage in a lifetime ....


Charlie Stock beat the lot in ...basicaly...a dinghy hull with a home buit top and rig....

I live in Essex...Blackwater....bilge keelers....de rigeur around here

Another place ...then take you pick??

For me .....B/K every time.....just in case I get the sums wrong........again !

 

[Searush]

Bluebird of Thorne (Lord Riversdale designed the first twin keeler) was specifically designed as a blue water cruiser & crossed several oceans. Even the tiny Shrimpy had few problems with ocean crossings. But why let mere facts influence prejudice?

 

[Lakesailor]

the keels mean extra wetted area drag.

but extra keels on a cruising boat seem a bit of a drag, literally.

How can a bilge keeler carry more wetted surface area than a long keeler? http://www.brayyachtdesign.bc.ca/article_twinkeels.html

1. Higher sailing speeds than an ordinary cruising yacht of similar dimensions. Surprisingly, part of the reason for this is the relatively small wetted surface, which yields improved light air performance. Modern twin keels are of high aspect ratio and present less wetted area then a full keel or long fin keel while retaining the steady helm associated with full keels.

 

[Pete7]

long keel design will be a lot more efficient for passage making, which is surely the point of blue water boats
.

How are you measuring this efficiency?

 

[2nd_apprentice]

Bilge keelers are brill for taking the ground, which is exactly where they belong

 

[Lakesailor]

Depends if you think of a bilge keeler as an '80's heavy lump with two vertical cacky bits of grp filled with steel waste.
Did you read my link to Bray Design?

 

[Seajet]

How are you measuring this efficiency?

Pretty simple really Pete7, time taken to get to destination !

Even if not racing it's nice to get to Point B on the chart reasonably quickly.

Twin keels are spiffing for drying out should one fancy doing this, otherwise incur drag via wetted area ( wetted as in exposed surface area, not in the water, aircraft also suffer wetted area drag ).

As opposed to a single central keel, twin keels also leave the prop' and rudder vulnerable to flotsam etc, so are not usually a designers' first choice for a blue water boat.

 

[macd]

Allows the boat to take the ground in protected bays at no charge!

That rather depends which bit of distant water the bilgey might be visiting. Tidal ranges in the Caribbean, in particular, and most mid-ocean tropical islands are tiny.

 

[Twister_Ken]

That rather depends which bit of distant water the bilgey might be visiting. Tidal ranges in the Caribbean, in particular, and most mid-ocean tropical islands are tiny.

Ditto Med, Black Sea.

 

[Lakesailor]

How can a bilge keeler carry more wetted surface area than a long keeler? http://www.brayyachtdesign.bc.ca/article_twinkeels.html

1. Higher sailing speeds than an ordinary cruising yacht of similar dimensions. Surprisingly, part of the reason for this is the relatively small wetted surface, which yields improved light air performance. Modern twin keels are of high aspect ratio and present less wetted area then a full keel or long fin keel while retaining the steady helm associated with full keels.

incur drag via wetted area ( wetted as in exposed surface area, not in the water, aircraft also suffer wetted area drag ).

Someone is wrong. Bray Yacht Design thinks otherwise. Perhaps aircraft travelling at 300mph have different issues to yachts trying to drag their topside through the air at 8 knots.

 

[Searush]

Yer wasting ya time, Lakey, prejudice trumps facts every time.

 

[Twister_Ken]

How can a bilge keeler carry more wetted surface area than a long keeler? http://www.brayyachtdesign.bc.ca/article_twinkeels.html

Not saying Bray is wrong, but it is out on a limb compared with most other designers.

Also if bilgers are so good, how come very very few (if any) have ever made a mark in top-level racing, where owners and designers will do whatever it takes/costs to squeeze another nano-fraction of a knot out of the beasts.

We've had winged keels, trim tabs, tandem keels, forward rudders, canting keels, water ballast plus other sorts of jiggery-pokery but not a spare keel, AFAIK.

 

[Douglas T]

I sailed a twin keeler round the world - - it was a Snowgoose cat.