Select to expand quoteDrogueOne said..
A very good presentation, clear, concise and no extra fluff.
Thanks for posting.
Yes agree, and very interesting.
It's funny the interplay between function, form and beauty.
IOR bustle tends to look wrong to me, in part because it tends to break symmetry and in part because I associate it with narrow performance over safety. That said a sensible shape for those conditions would need to be about 100 meters longer to be appealing : p
Interesting excerpt from an article on the same subject below.
I had not ever previously considered the deleterious effect of furling head sails and of course in mast furling. Imagine the amount of water trapped inside a furled or partially furled headsail when the yacht is inverted. I was also recently shocked to see a calculation of the negating effect on keel ballast of a modest radar unit even halfway up the mast. Solid solar panels are also seriously compromising as are dinghy davits... on cruising boats.
People also die from getting their heads gashed below decks in a rollover and it never ceases to amaze me that people seem to be happy with over length bolt ends passing through the coach house roof exposed to the cabin. I have minor intrusion of dome nuts down into the cabin from the bolts holding my liferaft securing apparatus above which I don't like even though they are rounded and only protrude downwards about 7 or so mm.
I have 2x20kg solar panels well over 6 ft above my cockpit floor together with supporting stainless steel the effect of which I have not calculated but must be pretty bad. The problem of course is that flexible panels don't perform well at all. I keep meaning to cut off the supporting structures to reduce the excessive height by about 6 inches but I do love the shade and it precludes the necessity for a fast deteriorating soft bimini. I take consolation from the fact that it would probably rip free and I also have a version of my yacht with rarish factory optioned 800kg lead boot on the bottom of the keel with no countermanding increase in (already considerable) mast height.
Not sure about the supposed advantage of form stability of modern dinghy shaped hulls mentioned below. It seems to me that in a rollover the form stability of that type of hull which keeps it upright before a knock down serves equally well to keep it inverted after a passing a knockdown state.
In addition to the mentioned decrease in downwind handling due to difficulty steering I also would have thought that a dinghy shaped hull (vs IOR) would be more susceptible to pitchpoling due to the increased surface area and flotation near the transom exposed to a breaking wave astern.
Do twin rudders common on wide assed boats counter the steerage issue? Taking to extremes I don't remember Shaggy complaining about his Pogo, I can guess once it's hard chine dug in it would be 'on rails'?
Would Sugru or similar be a good idea for your exposed bolt?
Select to expand quotejulesmoto said..
I dunno if I agree about this comment from the YM article.
"There's also a move toward fine bows and wide sterns, making boats harder to steer downwind."
I agree there is a move towards wide sterns, but fine bows I don't think is correct. I would posit that the trend on wide arse racing and cruising boats is for more volume in the bow, not less and they are easy to steer DW. I took out a French couple that had 10,000's of sea miles on their fine stemmed previous generation Class 40 hull. The biggest difference they commented on was how much drier the decks were and the lack of pitching. That extra volume meant it sat bow up even running in 30+knots and big seas. The latest designs post my 2016 era are even more voluminous forward.
The well credentialled NA houses I looked at all had one thing in common, you get quickly that stability is reflected in every aspect of their boat designs. Example: the deck, sheer, cabin top and companionway shape are resultant from inverted stability modelling. A CoG that is near, or near to, under the boat. Mainsail flaking that sits low on the boom. A boom that sits low on the mast. Window design and materials that are nearly as strong as the hull. Baffles in the bilge to stop free water from running forrard and aft preventing massive changes in pitch attitude. A roof and bulkhead design that does the same when inverted.
Proper watertight bulkheads. Weighty components are low and inboard, nothing high, in the beams or fore and aft.
Even weird things like its not just about getting a good AVS, but how a balanced sail plan that gives ample warning of impending broaches and takes seconds to recover from, even when under storm sails. The positioning of electrical connections at mid points and not in the bilges, under deck or cabintops apparently spun out of the inverted stability design modelling.
After now having done enough miles on both, I would unquestioningly prefer a scow bow Class 40 hull form for taking on filthy conditions. From a good quality NA that is. The low COG, lack of weight aloft, wide beams and ballast/weight ratio will give you some savage motion when near the beams, but IMHO that's far outweighed by the resultant stability and survivability. The 12.50 was more confidence inspiring the crappier the conditions got. It was still fun, it would go, steer and feel like a dirt bike or a go kart with all the grip in the world.
The inevitable penalty of course is its sticky light air performance and you're never gunna outpoint the canoes, so if light air sailing and gentleman like motion is a key buying decision, well the fine entry, canoe hull forms still rock.
The skinny canoe guys just have to learn to like the green decks when its gets sloppy 
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Cool video, thanks Ramona!
