Bilge keels for distance yachts

kunyang said:
So, if Scanyachts made only a few bilge keelers, did they have any problems with them (like the moody's). There's not much info on the web on them.
Click to expand...

Not sure they made much of anything. They were importers for the boats from Denmark for many years until the yard closed then bought the moulds and tried to relaunch them in the UK. Some were built by Trident Marine, but not sure who built that 39. Not aware of Moodys ever having any problems with bilge keels - Westerly, yes on some models. Looking at that boat in the photos, seems pretty ordinary bilge keel design so any structural problems would be easily spotted by a surveyor. Don't know about sailing qualities, but again many similar (or slightly smaller) boats with similar keels satisfy their owners.
 
Twister_Ken said:
Doesn't seem to have caught on though.
Click to expand...

Commander D A Rayner was directly inspired by Bluebird when he saw her at Beaumaris & made a deliberate effort to spend time with Lord Ravenscroft as a result. Consequently, all the Rayner designed westerlies had similar keels (22, Nomad, 25, Windrush etc etc). It was only the later Laurent Giles designed boats that dropped the aerofoil sections, probably to reduce costs & simplify production, which became more important after Rayner died & sales started to grow dramatically.
 
Twin keels will always suffer wetted area drag, and may be handy for cruising but will never be ultimate performers; canted fin keels with canards are probably the best solution as proven by serious racing boats, but the engineering involved is a serious snag unless one fancies hydraulics and water ballast etc.
 
surely bilge keels wouldn't be as much of a hindrance as a short stumpy mast?

Seajet said:
Twin keels will always suffer wetted area drag, and may be handy for cruising but will never be ultimate performers; canted fin keels with canards are probably the best solution as proven by serious racing boats, but the engineering involved is a serious snag unless one fancies hydraulics and water ballast etc.
Click to expand...
 
Seajet said:
Twin keels will always suffer wetted area drag, and may be handy for cruising but will never be ultimate performers; canted fin keels with canards are probably the best solution as proven by serious racing boats, but the engineering involved is a serious snag unless one fancies hydraulics and water ballast etc.
Click to expand...
To start with you're still banging on about twin keels having more surface area. But what are you comparing them with?
Secondly you are banging on about racing and performance. Probably a very small minority of cruisers are interested in that. Passage times will be more to do with a variety of factors than 1/2 knot more in suitable conditions
 
And, of course, Chay Blyth's Golden Globe entry, Dytiscus, was a bilge keel Kingfisher 30... except that he failed to finish, pulling out because the boat was inappropriate for the Southern Ocean, was too lightly built and falling apart
 
Seajet said:
Twin keels will always suffer wetted area drag, and may be handy for cruising but will never be ultimate performers
Click to expand...

Dont think there is very much wetted area let alone drag on one of these!

View attachment 34715

View attachment 34717

I would suggest the French are now well ahead in Boat design and development for the twin keel cruiser market for which most uk manufacturers have disappeared some time ago
 
Actually post Chay quitting he sailed her back to the UK. She then took part in other races performing very well and she is still going strong to this day. My K30 clocks in at 7 tons so she is not lightly built, the hull is over an inch and a half thick.

The vane steering gear had problems steering the boat and possibly Chay's inexperience of sailing at the time probably didn't help. Chay has since revisited the K30 and sailed one for an article complimenting the little boat.

For the record she is twin keeled, not bilge as there is no bilge - the keels are the fuel tanks, weighing in at 3/4 ton each. Each is held on by 30 bolts through steel ribs embedded in the hull. The mast is stepped onto the keels via an internal steel cage.
 
Last edited:
Lakesailor said:
To start with you're still banging on about twin keels having more surface area. But what are you comparing them with?
Secondly you are banging on about racing and performance. Probably a very small minority of cruisers are interested in that. Passage times will be more to do with a variety of factors than 1/2 knot more in suitable conditions
Click to expand...

Lakesailor,

well two keels compared to one for a start ! :rolleyes:
 
Twister.

s_1.jpg
 
Just to confuse things with some more facts and personal experience.

Wetted surface area is significant at low speeds but less so at higher hull speed.

IME : There is some truth to the claim that downwind tradesailing( the OPs question?) the extra foil surfaces of twin keels and skeg dampen roll more, which makes for a straighter course, less corrective helm( brake) and sails pulling better .. Nicer for the crew too.
 
The fact that there's twin keels doesn't make that much difference (unless you're racing) as demonstrated by boats such as RM and some Hunters. It's not the number of keels, it's the design of them and the rest of the hull that matters. Most bilge keelers are shallow draft and fairly voluminous. A long or fin keel with an otherwise similar hull and draft wouldn't be that much different. I'd be more concerned about keel slap, which could drive you round the bend on a long passage.

A bilge keeler is usually less likely to slip sideways than a fin or long keeler of the same draft when excessively heeled as the leeward keel is further submerged and frequently angled out from the centreline as well as possibly having a bit of toe out generate lift on each tack. If you're in the right kind of area then don't under-estimate the value of being able to take the ground. It's not just about being able to use shallow tidal moorings - you can save a fortune on lift-outs and check for damage if you hit something or catch a rope/net.
 
A twin keeled Westerly Fulmar turned up here in the 1987 ARC Rally (in the days when it still came to Barbados rather than St Lucia) and entered the Mount Gay Regatta on Boxing Day in full cruising trim. She was racing against visiting yachts and local cruisers (who were not carrying all their worldly belongings with them), and she did very well. I remember seeing her sailing upwind very efficiently at a rate of knots.
 
kunyang said:
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.

:confused:

Dave
Click to expand...

Rather than get in a twist about "wetted surface" arguments etc, I can offer this expert view http://www.goodoldboat.com/reader_services/articles/keeldesign.php
 
You must log in or register to reply here.

Other threads that may be of interest

Frogmogman
My next boat.
2 3
Replies
40
Views
1K
fredrussell
F

Share this page

Top