To lift even a half-tonne keel needs a serious amount of horsepower to be applied by the crew, and this is not to be the kind of boat in which motorised hydraulics are to be employed. "Less is more", remember. That's why I've stuck to unballasted boards, with a fairly neutral buoyancy when immersed. They are fairly easy to operate, which is going to be important. 

so yes, lateral resistance can be obtained with lifting boards; even better, positive lift is obtained from cambered bilgeboards; but when it comes to safety in big seas, a different question, there isn't a substitute for getting the ballast low. How low? Well, that's on a sliding scale, taking into consideration the use that the boat is to be put to. Annie is going to sail around Hauraki Gulf and Northland. Though it can get windy, the seas are generally not huge, having the whole of North Island as a breakwater to the west, and smaller islands to the east. So while I would be content to see Annie fit a very shallow keel (more of a slab of metal, really) to keep the draught down close to 2ft, if anyone wanted to go offshore in my version of Sib-Lim, I'd want them to fit some deadwood between the hull and the same slab of metal, to increase the draught.

Having got my tall narrow sail working on Tystie, and having found that it is much better to sheet the sail to the arch over the cockpit, rather than at the transom (no sheets sweeping over the cockpit, for instance), I'd rather like to see this sail, scaled down, on Sib-Lim. It could be sheeted to a small arch over the companionway, with the advantage that hauling on the sheets can be done vertically - a big advantage for a skipper with a limited amount of horsepower and avoirdupois.

David (another one!) - what a lucky man you are to have owned one of these vessels, although I have to admit that your description of sailing at 30 degrees heel, has somewhat moderated my enthusiasm for the design.  I have a friend who is (very slowly) rebuilding an Atalanta here in NZ.  She apparently sailed from England, which I can readily believe.  I keep telling him what a splendid candidate she is for junk rig.  He's a professional boatbuilder, so quite capable of making any necessary mods: of course, a split junk rig might solve that problem.  

My Sib-Lim, if she ever gets built, may not be as spectacular a sailor, but (and I know this is completely the wrong attitude), she is designed first and foremost my home, and that is more important to me than performance.  As long as she gave me fun and satisfaction when I did go out sailing, I would be more than happy with her.

Annie,

I checked up Uffa Fox’s Fairey Atalanta 26.

There are a couple of good reasons for their performance:

·         Long waterline and moderate beam and displacement makes for an easily driven hull, better than any of the Sib-Lim contenders (at the cost of live-aboard space). See here.

·         Flat bottom and all the ballast in the two very deep, retractable boards ensures both good working power to windward and sufficient ultimate stability. I understand the boards (each at 215kg) are now operated by (manual?) hydraulics.

These two factors put the Atalanta in a different league than any of the Sib-Lims, but at the cost of complex construction  -  the Atalanta was produced by an aeroplane maker...

Here is a list of data I found about it:

Fully Equipped LOA 26ft (7.9m)
LWL 25ft (7.6m)
Beam 7ft 8in (2.34m)
Draught:
Boards raised 1ft 8in (0.5m)
Boards lowered 5ft 9in (1.75m)
Displacement 4000lb
Ballast 950lb
Sail area 270ft²
Berths 5 (+2 cockpit berths)
Engine 12hp Mitsubishi Vetus
Designer Uffa Fox

Arne

Surely the bilge-boards provide the lateral resistance required?  And the beam of the hull keeps her on her feet?

I'm still influenced in my thinking by the Atalanta, which apparently sailed perfectly well to windward and floated on a heavy due with the boards up.  An extra 8 inches of draught means that I am floating more like half the time than a third of the time.  Our tides are nothing like those in the UK, don't forget, David.

I've been thinking about the outboard, Arne.  There is no weight difference between the Nissan 6hp and the Nissan 10hp.  Another argument in favour of the larger engine.  And I don't see that it would use a lot more fuel.  In theory, I don't like the idea of relying on my motor, but in practice I would use it if necessary.  Feeling sick with worry that something would go wrong! 

Yes, Chris,

I anyway expected that the shoal draught boats would have adequate "wings" in the water. My concern is rather how to produce enough righting moment to provide the required sailing power to windward, against strong winds and heavy seas.

Your shown design looks interesting and Chinese, but how powerful would such a boat be to windward? Remember, most offshore junks were a lot bigger than this and big is beautiful when it comes to upwind performance.

This has been well demonstrated my country: The Colin Archer sailing rescue boats (around 47’, 30tons) were legendary, and if you see them sailing on Youtube (search for RS14, Stavanger), you will see that they sail really well. However, being so popular, many made downscaled copies at around 30’ and even down to 25’, and these are no good at all, being way too tender.

Therefore, small boats needs comparatively more ballast and bigger keels to work to windward. Annie’s Fantail is great in this respect, and so is my new  26’ IF (disp 2150kg, ballast 1250kg).

Arne