The task: to genuinely produce a seaworthy, comfortable design I plan to live on till the end of my days, given that everything?s going to crash socio-politically.
The constraints: money mainly. There?s enough to get the shell on the water and the rest would somehow follow that. Until it?s ready, it stays coast bound. Eventually, as I tend to the decrepit, it would indeed be coast bound. In between, hopefully, there?ll be some nice sailing.
The ideal: a yacht as most people know it:
That?s not a realistic possibility for me, at least not larger than 31 feet and possibly not a monohull [reasons below].?? First thing is to fix on about 31 feet, the length of the Westsail in the pic.?? Why 31 feet?
1.? Long enough to get away with fitting two masts;
2.? No sail larger than 200 sq ft
So, to start looking around: first at the Bermudan rig:
? it gets over 200 sq ft in the main very quickly so clearly it?s not the rig to have for cruising, particularly as the idea is to have the rig low enough to handle [no higher than 80% of the boat length.?? Sq ft by sq ft, the best sail is the lug or the gaff but you need jibs out front for efficiency as well:
The squarer a sail is, the less efficient, which is why Bermudans have tall, narrow sailplans.?? However, what about a lot of short sails in a row [as you see], each sail relatively tall and narrow but the overall effect low and long??? That?s the aim on this boat of mine.
There are other reasons for using this plan on a cruising boat:
1.? The tacks [the boat going through the eye of the wind] are far less;
2.? If sails blow out or something happens, there are the other sails;
3.? Less overhang over the water;
4.? More easily reefed [lowered or dropped];
5.? Easier to climb the mast[s];
6.? It requires a long shallow keel, better for cruising;
7.? The flexibility allows you to run jib and mizzen in tight situations;
8.? You can still handle the sails with blocks [pulleys]:
? and not have to go to expensive winches:
The N1 downside to a winch, aside from cost, is that you must be physically nearby with a rotating, winding lever, whereas the other way, you can be anywhere on the boat ? same with using a tiller rudder rather than a wheel.? This is handy on a cat.?? The block pictured is also expensive but I?d either make mine or buy less expensive blocks on the grounds that there is far less stress involved from these sails.
There?s another spinoff from the long, low sailplan and this looks like a disadvantage in this clip.?? Note the two front sails [jibs] drawing well but the rear sail [the main] is flapping like crazy.?? The second last is oscillating a bit:
For a cruiser, this is actually very good.?? What?s happening is that the front sails are giving ?dirty? wind to those behind, causing drag and stall.?? Upwind there is too much sail aloft and if it was all drawing equally, you?d be capsized.?? However, using the dirty wind to advantage [less efficiency], the boat heels less [leans over less] and more sail can be kept up for when you bear away [go away from the eye of the wind] which is when you want a fair bit of sail up.
?Purchase? is the word in sailing for the mechanical efficiency of the pulling device. ? ? I work on 15 sq ft to one purchase on a Bermudan sail but maybe 20 sqft:1 on a gaff.?? That is the most I can physically handle in a moderate breeze, not forgetting that on a cruiser, you can reduce sail and the pressure therefore drops.
If my largest sail [the main] is under 200 sq ft, say 180 sq ft, then I need a purchase of 9:1.?? This is ungainly and right on the edge of needing a winch.? Solution is to run a 6:1 system down to the traveller [the wire which goes across the boat, to which the sail sheet [rope] attaches].?? Then the traveller has a 2:1 system and that solves that.?? When it becomes too much ? reduce sail.
Or else reduce it and tack the extra area on the mizzen [see below] and foresails:
? meaning you?d have to run as a ketch and not a yawl.
So the form of the boat is slowly coming together.? It?s going to be long and low in sailplan and keel, with four sails and a storm jib in reserve.
Now to other considerations ? for example, which hull configuration? ?? There?s an excellent article about the Hunter 260 on design considerations and the author observes the following:
Boats are divided into categories based on certain parameters in respect to stability, buoyancy, and other relevant handling characteristics. These categories are:
Category A? ? Ocean; Extended voyages with wind force in excess of Beaufort force 8, and significant wave height of 4 meters or above.
Category B ? Offshore; Off shore voyages in possible wind force of Beaufort force 8 and significant wave heights of up to 4 meters.
Category C ? Inshore Voyages on coastal waters, large lakes, bays estuaries, or rivers, where wind force of up to force 6 on the Beaufort scale and significant wave heights of up to 2 meters may be experienced.
Category D ? Sheltered waters.?Designed for voyages on sheltered inland waterways, including lakes, rivers and canals, where wind force 4 and significant wave height of 0.5 meters may be experienced.
While we might dream of ocean going, it?s usually way beyond our range.?? At the other end of the scale, a boat only suitable for sheltered waters is Ok if that is absolutely all you?re going to do ? you might live next to a lake, for example.
Most people need a boat to be multipurpose enough to do mainly Category C and a bit of B for short periods.?? Problem is ? that is like saying you want your car for commuting but also for a bit of drag racin ? the very designs must be altogether different.
The other day, I designed two boats of 31 feet, with around 500 sq ft of sail each. The first was a displacement monohull with a full keel, based on the Westsail:
? perfect for big seas and bad conditions but not much use in estuaries and near the beach. Plus the problem of mooring and putting in a marina.?? Plus the lack of space in 31 feet.
The second was an attempt to combine a few Westsail and Colin Archer features in a broad-hulled displacement catamaran, not unlike a Wharram Pahi, which has been proven as a true oceangoing craft at incredibly low cost:
Now there is amazing prejudice from both camps. Basically, the arguments are these:
1. A monohull is a ?boaty? boat, a proper looking craft [see the Westsail at the top] and seaworthy to boot ? no argument from me on that.??? After all, the three primary considerations are:
a. Seaworthiness, including crew comfort and safety;
b. Fittedness for purpose;
c. Aesthetics.
You can have any two. Actually, you can get close to three.
2. A monohull works on a ballast system like a tippy bias-weighted doll, the type you tip over and it springs back up again. The extent to which a yacht tips or stays up is called its stiffness or tenderness. Provided you?re not afraid to be knocked down [and a mono tends towards this all the time], knowing it will spring up again, then everything?s fine and you can rest easier.
This is why most mono sailors say that around the British Isles and North Sea, with its washing machine style waves and vicious currents, the mono is the only way. A multihull will simply flip over on uneven waves and that?s the end of the sailing.
3. A monohull is usually a displacement hull, meaning it sits deep in the water and it?s hard for the wind and waves to throw it out of its ?hole?:
Not only that but being so deep, the cabin roof need only be a short height above deck and yet you can have full headroom below, which makes it more like a living room and has the feel of bringing your home onto the water, a quite uplifting thing for a sailor in an angry sea.?? It can?t be discounted, this factor and Dragonfly Trimarans [Quorning] try to emulate this sumptuous appointment look in their boats.?? Most people are conservative on this and rightly so ? a mono has proven itself countless times as the design of choice.
One problem with cats is that you just can?t get the headroom without going tall and slab-sided:
Frankly, they?re not beautiful and look at the people beside the cat ? there is no full headroom on a boat that length ? there should be at least at one or two points fore and aft.?? Cats also tend to be shallow and round-bottomed for speed and this plays merry havoc with them as a cruising option.
Most cat designers try for the central pod, wanting it to be low and sleek but it hardly ever works out like that and the result is a wallowing tub with low clearance:
The waves will slap and roll this boat around ? you?ll notice they built tall above the deck to get the headroom.? Not nice.
There is a solution though ? the Wharram solution ? which is to build deep displacement hulls for the cat in a V profile section or close to it.?? This lets the boat track better and presents less area for flipping.? With a cat, there are two motions ? efficient and slap-slap-slap on the waves or deep and bounce-bounce-bounce like a yo-yo.?? The latter is softer but both become wearing.
The solution is careful compromise ? making the profile something like a parabola. ? Also, fore and aft, the rule is that you try to graduate your weight [load] between about 15% and 85% of the boat length, with the median load about 60% forward.
The correct amount of fullness in the bow and stern for a particular boat is the art of design.
Another downer for the catamaran is that it relies on daggerboards through the hulls to stop sideways motion.?? This actually provides a fulcrum around which the boat yaws [wants to go left and right], as you?ll see in this clip:
The case for the cat
So, having said all that, it doesn?t look too good for the cat as a final choice but the advantages of the cat have not yet been spelt out:
1.? Monohulls don?t have a mortgage on seaworthiness or rightability ? bad sailing or damage will cause this:
It?s all well and fine mono sailors saying cats have a narrow window of safety and that one error will tip you over but there are things to be said about that.
There are worse things than a capsized cat ? it sits placidly upside down and provided you have designed in a hatch to get inside the hull for warmth and food, it?s reasonably OK.?? It will not sink, unlike a mono ? the vast majority of sunk craft are monos and that?s still so when cats are near-ubiquitous today.?? You never hear about yachts losing keels or being flooded and so on but it happens with regularity.
A cat, in itself, is a safe boat ? often built in separate compartments which float in themselves.?? It?s also fast and you can run away from approaching bad weather better than a mono.?? With boards up, in a storm, the cat will keep to the contour of the wave but that can be a double-edged sword, of course [see vid above again].
2.? The constant leaning over of a monohull, the motion and only having two thirds of accommodation space for the given length, plus wanting to bring the boat close to the beach most places it goes [not just the North Sea], provide some very good reasons for a cat.
Also, in hostile seas, the spaciousness of the cat?s accommodation and that large deck between the hulls induces a feeling of safety and space.?? The motion itself in a well-designed cat is nice.? This is a tri, not a cat but you get the idea:
The Achilles heel is definitely though, agreed, that it can flip, even if you design it not to do so.
Experiment ? take two planks 2? x 6? x 1? and bevel the long edges of one at 45 degrees.?? Lie them on a linoleum floor and push against the long edge.?? The one without the bevelled edges will flip up first but neither will flip on the lino anyway ? they?ll slip sideways first.
On a boat, there will be something preventing sideways slip and so a more proper experiment is to put a finger behind the plank with one hand and try to push against it with the other, from the other side.?? It will resist for some time but if the push becomes even slightly upwards with the unbevelled plank, then over she goes.
That?s the issue with the cat in the pic further up [with two people at the bow].?? Not only that but there is a sail in each hull on that boat to make it worse.
The trick then is to design the cat low in the water and any extension above, though it might cut interior living space, should be faired and fall away towards the centre of the boat:
Maximum flat area presented to the wind is narrow and just above the waterline, also where you need it in the hull for berths etc.?? My criticism of the one in the photo here is that they demanded headroom for too many parts of the below decks area.?? For example, berths don?t need full headroom, the galley does, the head [loo] doesn?t.?? The ?football? shape of that cabin is not beautiful ? it can be done better.
So, arranging all these elements to reduce windage wherever possible, even at the cost of aerodynamic flow fore and aft, is necessary on the cruising cat, plus the shallow, full-length keel, supplemented by leeboards ? remember this is a quickish cruiser [around 10-12 knots], not a cruiser/racer.
Some monos have tried to emulate the multihulls ?beachable? advantage, using an age old technique ? water ballast.
Trouble is that though it does work, such boats are unstable in big seas and need the ballast shifting each time you go about, otherwise the advantage is lost.? So either back to the Westsail mono and stick to deep water around the UK or go for the long, heavy cat and watch the windage, ensuring very little ?flat? is presented to the wind abeam.
If all the sailing were to be done around treacherous waters, e.g. German Bight, Fastnet, the strait to Orkney etc, then the Westsail or Archer is your boat.?? For sailing further afield, e.g. the South Pacific, then I?d take the cat, especially if there was a danger of shallow seas in places, and/or rocks.
Barring major accidents, the worst which can happen to a cat is a capsize and with sufficient buoyancy in separate compartments keeping it afloat, along with buffer floats stored under the deck with dedicated halyards to the masts to haul the masts back close to horizontal, along with the ship?s dinghy and a transferable outboard system to it from the hull, then that?s the N1 cat problem covered.
Last thoughts on this
Needed would be more volume, heavy keelson [spine], 3/4? planking instead of 3/8?, stores arranged in such a way that nothing heavy goes in the ends but instead near the outer hull edges, down low, the shape a parabola and curved sides so that the hull looks not unlike an onion in profile, the rig spread out fore and aft and low, easily dropped sails ? one sheet released and the sail collapses into its lazy jacks [the lines around the sail into which it falls] ? and various other designed in goodies.
Most mono sailors think of the cat as either one of those plastic fantastics leaping into the air or one of those tubs pictured further up in this post.?? It really does not have to be like this ? efficient albeit heavy hulls and ?trackability? built in, along with easy to work systems makes for a most seaworthy craft, certainly one I would entrust my life to.
However, when all is said and done, nothing in either design or preparedness will compensate for stupidity:
You put idiots on a mono or a multi and the result will be the same.?? Yachts are not for the naive and clumsy.
Filed under: Leisure, travel & sport, Technology & ideas
Source: http://nourishingobscurity.com/2012/09/30/the-final-solution/
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