As you well know (and I’ve been learning lately as I investigate trading off planing forces for displacement forces) – “squarish” is in fact most efficient (meaning with absolutely sharp chines – no rounding) when it comes to hull shapes if/when they can attain the higher speeds that also yield dynamic lift. So the lighter weights and higher RM’s of multihulls are a natural for exploiting the benefits of ‘flattish’ shapes ;)

Similarly, moments are moments no matter how they are generated. Generating RM for anti-capsize can be done either with weight on the bottom or floatation at the top. Cocktail napkin arithmetic applied to 15/20 foot boats indicates that 1 pound of bouyancy at the masthead is worth perhaps 30 lbs of lead in the bilges. There is at least one sailing class (bad memory) that utilizes thin foam inside the top panels of their sails to good effect.

For me (at my age), a good and safe boat is an unballasted and multihull-fast boat the won’t turn turtle – which more and more rules out proper multihulls from being my ‘last’ boat.

Anyway, that’s what leads me towards longer skinny hulls – perhaps 50% longer than a hull of the same payload – combined with some kind of planing surfaces for speed -and- a bouyancy substitute for anticapsize.

So far most of my napkin-sketched solutions are butt ugly – that is until I add some kind of canting rig scheme for even more net horsepower (VMG horsepower), then they get really goood looking ;)

Sorry I digress – it seems therapeutic and helpful to think about this stuff out loud sometimes.

TomH

Hi again Tom,

It is unlikely that I will design bigger boats. There is just no money in them. But I am very interested in smaller off the beach catamarans. Some of the high tech developments in the A-Class Catamarans seem to indicate a squarish shape is not as inefficient as traditional cat thinking has tended to believe.

So some type of of the beach cat might appear. Or a minimum accommodation cruiser.

Michael

Hi Tom,

It is a really interesting one and there are lots of myths to implode.

A few years ago I found a second hand copy of a history or the British Royal Ocean Racing Club (RORC) that was published around 1960 (?). The club along with the American CCA (Cruising Club of America) which had been on the forefront of creating the offshore racing tradition.

It was written by Adlard Coles who has written several books about heavy weather sailing that have been highly influential.

The book was quite critical of existing sailing before the second world war with the fleet anchoriing whenever there were strong winds on the nose. The boats just were not up to it. These included Channel Cutters and some designs championed by Claude Worth. The boats just couldn’t make ground to windward in those conditions.

There is a saying “gentlemen don’t sail to windward”. The reality is that Gentlemen yacht owners in the UK or the USA were unable to, however those in Scandinavia or in Polynesia (or their homeland of modern day Taiwan) had been managing it for decades or millennia.

Then along came Blondie Hasler and his bunch of commandos sailing the Scandinavian restricted sail area rule 30 square metre boat – Tre Sang. It was cramped, low freeboard, but light narrow and long. So it would eat up to windward and fly downwind when the indigenous British tradition was too nervous to lift anchor.

Adlard Coles in his boats called Cohoe were derived from Scandanavian theory as well.

Also John Illingworth who put together a series of boat called xxx of Malham. My very favourite boat of this era was his strikingly modern looking “Myth of Malham” which I think is a truly beautiful boat, despite most traditionally minded types thinking she was an abomination. But perform she did. The only foolishness were the large genoas that gave unmeasured sail area under the rule. Very inefficient sail area, but extra that allowed the basic rig to be reduced in size so the rule would think the boat didn’t have much sail.

The truly stupid part of genoas were that they were adopted for cruising boats too and you can find dozens of old article about “cruising genoas”

In the Americas the revolution was as International Rule boats such as 6, 8 and 12 metre yachts (the old America’s Cup class) started to be imported and built. I think there was a series of 10 of the 10 metre class rule boats made for a group in the New York Yacht Club. Built in Scandinavia and designed by Luders (again from memory) they showed how capable they were at sea.

A young designer at the time, Olin Stephens, got a design commission to develop a couple of 6 metre designs to the rule. They were not terribly successful, but when he got a commission to design an ocean racer the result was the famous Dorade, in some senses a barely disguised metre boat but with a ketch/yawl rig to make the best of handicap allowances under the CCA rule.

Over time under the influence of the rules these slim seakindly hulls put on width as it was realised under the rules you could make the boat look slower and heavier by going wider but that the boat wasn’t quite as slow as the rule projected. But it meant the boats moved from seaworthy types to the very distorted shapes with stupid sails like big overlap genoas purely as an influence of the rules. Enshrining cost, big crews an boats that were real cows in many conditions. Sole virtue that the rule thought that they were slower than they really were.

The culmination of the type was the pic below – distorted shape … note the way the hull volume actually swings up vertically above the rudder for rule purposes and the plan view shows lots of volume in the middle and fine ends. Kind of OK for going upwind but not very good at either accelerating cleanly under wind pressure downwind.

Just a reminder of how things had been from the same designer. Dorade again

But then these were about to be eclipsed by two further developments. Multihulls and cheap high performance sailing yachts, strangely slimmer than the way the slower ocean racers were developing. The main proponents of these were EG van deStadt and Kiwi John Spencer in the early ’60s.

The modern multihulls were never allowed to race with the establishment yacht clubs and there was a great running around trying to find ways of eliminating the plywood planing monohulls on structural grounds on very little evidence of problems. Van deStadt and Spencer both being good engineers as well.

Here is a vandeStadt Black Soo

And one of the Spencer plywood circa 1960 maxis “Ragtime” (originally called “Infidel”) that won or went close to winning the Transpac race so many times it became legendary totally outclassing modern boats up until recent years. A clean hullshape, modest sail area and hard sailing.

We moved around from such lovely clean hullshapes, simple construction, sensible ballast positioning to develop distorted and much slower boats and arguably much less seaworthy and less safe ones … at least until a generation later when a bunch of innovative Kiwi designers Bruce Farr, Laurie Davidson and the late great Paul Whiting found a way of doing fat light boats that would fly. Again the rulemakers tried to ban speed and also tried to imply the boats were not strong enough – a criticism that could have been levelled at some of the more lightly scantled boats that were acceptable such as the North American One Ton Class champion Pied Piper where the crew asked what to do as the hull panted in and out four inches over every wave on the way to Hobart – the answer – “don’t look”.

Bad rules and artificial distinctions between types of boats have been very retrograde for sailing in terms of affordability and the proliferation of boats and features that are foolish in one way or another.

The automotive powered canting keeler maxis are the children of this corrupted evolution.

Enjoyed your analysis of the “rules = designs” cycle – especially the view that the designs are then perceived to be “fast” ;)

Looking forward to a trimaran design from you – you already know that I (and lots of others) really appreciate your approach to getting speed from simplicity and would like to see your take on something like a ultra-simple 9m trimaran.

Definitely not trying to bait you, a serious wish to see something like this from your drawing board.

Cheers,
TomH