Originally Posted by sparau
i was worried being so flat, wide and with the weight only at floor level that at anchor it would roll like crazy and even possibly it would have near zero self righting.
as to beaching it, i dont really want to do that often but i do like the extreme shoal draft
, 0.5m !
The nearest thing I know of to a laboratory for investigating the capsize
of blue-water sailing yachts is the Southern Ocean.
The boat that some would say started it all, Damien II,* has been sailing pretty much continuously since the late 1970's, spending the intervening decades in those waters almost exclusively, and when I last heard had still not been upside down.
Canoe body, no stub keel, swing keel which retracts completely into the canoe body.
In extreme conditions, the keel is sometimes intentionally retracted. There is an experienced body of opinion of those who spend their lives down there who consider there are more important attributes in such conditions than righting moment.
*(she wasn't the first, but the one which first came to wide public notice)
She was built (in steel
, 6mm topside scantlings IIRC) at 46' LOA
) with a swing keel (ballasted tip, 3 or 400 gallons of fuel
in the top), and a designed draught of I think a little over 3' (maybe 0.9m)
She was subsequently lengthened to 52', on a beach in Tasmania... steel
is good like that.
I guess the limited interest in bluewater, lift
keel in the Anglosphere is partly to do with cost, partly to do with fashion, partly to do with cruising grounds.... but I think partly to do with a tendency to dumb issues down by seeking single-figure ways to measure merit. (such as righting moment, or area under the righting curve). This is a static concept, whereas capsize
is a very dynamic activity.
I first discovered this not in a yacht but in (of all things) a Fiat Bambina. As an adolescent, I was fond of cornering at and beyond the limit, on anything with wheels (and as a result, on bikes I probably put in more miles sliding alongside my motorbike on tarmac, gravel and dirt than some people do in the saddle)
On my way home from work I encountered some pea gravel on a deserted stretch of freshly built, deserted freeway (what we call a motorway) and was delighted to achieve a genuine four wheel
drift. I'm confident that this represented a novel experience for this 500cc vehicle, which would lose a tug of war with any modern-day ride-on mower.
The interesting discovery came when I reached the end of the pea gravel and was suddenly looking at the world at an angle of about 50 degrees. To my delight, I was able to drive along on two wheels for a considerable distance, the 'heel angle' varying with the 'helm angle' in much the same way I was used to on small yachts. However it was pure chance that there had not been quite enough overturning moment offered by the sudden grip of the tyres on the road to flip her on her (partly fabric) roof.
What I'm saying is that a vehicle is relatively immune to rollover if it has little traction. Nobody rolls on an icy road ... until they hit the berm. This, I submit, applies to vessels, which helps to explain why a canoe-body with keel retracted is relatively immune to capsize when thrown bodily sideways by the water
avalanching down the front face of a large wave.
There's another benefit which the OP alludes to attached inseparably to shoal draft. I'm sure I'm not the only one who feels frustrated by the need to give interesting places a wide berth in fixed keel yachts.
To me such vessels are like a dolphin, in the sense that stranding is an existential threat, where a lift
keel yacht is almost as amphibious as a seal - for whom stranding is a holiday and a chance to catch up on some sleep.
Which brings me back to expedition yachts: if you want to treat yourself to one of the most beautiful sets of study plans you'd ever find, splash out on Ed Joy's design for "Seal", for Hamish Laird.
or get a hint here:
Expedition Sail - Sailboat Seal