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Background on W22 Design (book article)

As published in new book "More Small Trimarans" by BookSpec Publishing 2010

Target of article was to answer six questions posed by publisher Joe Farinaccio:

Author, Mike WatersINTRODUCTION
Well I guess I'm now one of the 'old guys' in this field but like many of my generation, still passionate about small boats and especially multihulls. When we started 40 plus years back, they were looked down upon by everyone else who sailed and it was tough - so we had to be both very convinced and very convincing! But today, cats and tris are finally recognized for what they are, so when we realize that whether we like it or not most of our wild adventure days are over, we want to share our experience and knowledge with others before it's all disappeared 6 feet under. That for me, was the main drive behind starting my website, where I've chosen to zone in on small trimaran design.

I already feel sad that inspirations like Norm Cross and Lock Crowther are not still around. They both contributed SO much to the modern multihull ... as also has Dick Newick, Derek Kelsall, Jim Brown, John Marples and others; even James Wharram with his minimalist designs that still managed some amazing voyages on a shoe-string. I am pleased to hear that at least a couple of these will be contributing to this book and also, therefore honored to share my thoughts within the same pages.

Today we have some wonderful boats from the likes of John Shuttleworth, the Quorning Bros, Chris White, Richard Wood, Ian Farrier, Hughes, Tennant etc. (and forgive me if I've forgotten someone important), but it's 'the pioneers' that had to be especially effective and convincing, as today's young sailors have NO idea how resistant the sailing public was to ANY sort of multihull — and how the press made it especially hard to get the message across that they were safe enough for long voyages when well designed and intelligently sailed. As others have said before, one glance at an overturned multihull was all the press needed to jump on the concept, without any word of how effective the boat then was as a liferaft! A sinking monohull left no trace and so was largely ignored as the press had nothing to show. But with ALL the important cross-ocean and round-the-globe records now being held by multihulls, there is no longer that huge hill to climb when presenting a new boat design to the sailing public. Multihulls are now here to stay and if it were not for marina space and multihull cost, might even put pressure on monohull survival!

Let me share a little of how I personally got involved.
Although I was working towards a career in music at the time in the UK, a casual sailing trip in a 14' gunter sloop when I was 10, led me to reading Arthur Ransome's great adventure stories about 2 intrepid sailing families from the Lake District. After reading 'Swallows and Amazons' at the age of 11, a chum and I each built a small 10' dinghy and yes, like a thousand other small boats in the UK at the time, they were inevitably named 'Swallow' and 'Amazon' and our own adventures followed. By the time I was 18, the decision was cast in stone and I gave up dreams of being a concert pianist to study naval architecture and have since created a plethora of designs from an 8' pram dinghy to 600' cargo liners.

I left England after graduating from what is now one of the most highly acknowledged boat-design institutes in the world (Southampton Technical University) but then spent 40 years designing ships of all types for a major shipyard in Canada.
But small boats were always prominent in my life and I first toyed with a cruising catamaran design in the mid 70s—and rather uniquely at the time, my 'Flying Wing' concept featured a lower hull solepiece of fibreglass that was combined with topsides of ply for easy fairing. I mention this as, rather interestingly, this feature has returned in the design of my latest W22 trimaran.

As well, as my career as a naval architect for a large Canadian shipyard involving many interesting trips overseas to meet potential owners, I started three small boat companies and later, a consulting firm called Interface Marine Inc. Now retired (though not from sailing or designing) I am happy to share over 60 years of diverse boat experience (about half that time with multihulls) through my website and various consulting activity.
(see www.smalltrimarandesign.com)

One may well ask, with a grounding in 'conventional' naval architecture etc, how come I was drawn to multihulls along the way? Well, although I can still enjoy to sail almost anything that uses the wind to propel it (and still love my Div-ll sailboard), it was the technical aspects that ultimately led me to accept that multihulls 'just made so much sense'. While looking at the monohull concept, it started to bother me that they only reached maximum stability when laid flat over with sails in the water. Once there, they were all too easily flooded and then would sink. Further, for all the other times when there was a good sailing breeze, this lump of steel or lead on the bottom did little to resist the heeling until it was well inclined off center — so it was doomed to sail at large angles with a greatly distorted underwater hull shape virtually all the time there was a decent breeze. Then there was the additional fact that the boat had to be significantly larger below the water merely to support and float this keel weight, even when it was doing virtually nothing until the boat inclined. And finally, this larger underwater volume made it hard to design a really fine hull shape for higher speeds, unless the boat was also very long. [Mind you, since those days things have changed a bit too. New, higher strength materials have permitted monohulls to sail more like huge dinghies with much greater basic stability than ever before, thereby pushing ultimate speeds up towards the realm of multihulls, though at very high cost and physical demands.]

I had read Multihull Magazine since its first issue and also subscribed early on to the UK-published AYRS Bulletins on Yacht Research that provoked new ideas and thoughts about boat design. I also attended the first World Symposium on Multihulls (in Toronto, Canada) and enjoyed listening to and meeting many of the well known designers of that time who were of my generation.

So as a result, my interest in multihulls just grew and grew and I have to admit that I was drawn to trimarans even more than catamarans, although both have their place 'et raison d'être'. [For me, a trimaran sails as 'a perfect catamaran' ;-) It always has the heaviest hull to windward and even more, there's an airborne outrigger out beyond that, like the sliding seat on an International Canoe!]

The smaller, 'potentially ownable' boats really caught my imagination though, as for all boats, the fun is frequently inversely proportional to their size.

More recently I have often been asked, what is the biggest appeal of sailing small trimarans as opposed to sailing other types of small sailboats? To this I would reply that a good trimaran design offers the thoroughbred feel of handling a finely-balanced racing dinghy with the added attributes of efficiency, power, space, speed and great stability. In many cases, it's drier and more comfortable too!

Personally, the first thing I do is to identify the target user and attributes that I want the boat to excel in. Exactly what these are and how to achieve them is based on my experience with sailing other designs and also what I have learnt from many others in the multihull design field whom I have had the pleasure to know and who have shared their accumulated and diverse knowledge. All this is tempered and put in perspective by my own technical studies and acquired knowledge, something that I have indeed found quite valuable, as every design is ultimately a collection of difficult compromises, all tailored towards the target attributes and user.

Being someone who graduated in the late 50s, most of my design work has been done using manual methods rather than computers. While the new generation may find this antiquated, my defense would be that to work as we did, we really needed to fully understand all the calculations, what was meant by the figures and how we got there. Most of the great trimaran designers of the past (Brown, Cross, Crowther, Harris, Kelsall, Newick, etc.) doubtless also worked the same way.
Today's younger computer-savvy generation can readily create wonderful 3D renditions of some dream concept, but it's not always apparent that the important calculations and detailed engineering are handled better by any software—the workings and formulae of which, are now often blind to the user. Having said that however, I did spend 20 years with a large CAD/CAM department under my wing and still use a computer where I feel it can actually add something significant to my work. One thing all good designers know is that computers are working tools and do not do the thinking or critical decision making, so I still always mentally check things in my head for global accuracy and feasibility. It's still far too easy to just accept computer output data that may not be realistic.

I am presently (Dec 2009) in the process of designing two small trimarans—the W22, and a smaller W17 for my personal pleasure. (As I have hinted earlier, 'the smaller the boat, the greater the fun' so there's a little intro on the W17 on Joe's small trimaran blog.)
After owning and sailing two trimarans designed by the brilliant Australian Lock Crowther, I was fortunate to become the owner of what I personally consider to be one of the finest small trimarans ever created—the first ever Dragonfly from Quorning Boats in Denmark. She was called 'Magic Hempel' and turned both the monohull and multihull worlds on their heads when she won her class in a very rough Round Britain race in 1985. (She is featured in the header for my website (see below) and also on Joe Farinaccio's newsy Small Trimaran blog, at:   https://smalltrimaran.co.uk/the-original-dragonfly-small-trimaran/#more-254

 [as well as several articles on my website].)

For the first time, here was a multihull that could sail decently to windward, tack on a dime, as well as having a light helm, great stability and she also kept the crew pretty dry in the process. As a beamier prototype for the Dragonfly 25 and later Magic HempelDragonfly 800, she was once timed by radar at 25.4 kt in the Baltic—not half bad for a 25.5' boat with a small cabin, sleeping 2+2! As she won race after race, the boating magazines raved about her clear superiority for good reason and although the F-27 appeared later that same year, the Dragonfly was always held in the highest regard in her native Europe—and that apparently remains true even today. Even 5 times Olympic medal winner Paul Elvstrom owned one and admitted it was the most enjoyable boat he'd ever owned. Although I had personally owned some 20 small boats, nothing compared to this wonderful boat. Sadly, I was pressured to sell her due to a passing health issue and with over 40 prospective buyers enquiring after her, the sale went all too quickly.
Since then, and with many personal years of experience and acquired knowledge, I have continued to dream of a boat to replace her—something that would retain all the fine points of this great design, yet be easier to rig and handle ashore and less costly to build. The new W22 is to be the outcome of all this and I am convinced she will be an extremely enjoyable boat to own and sail, for those who feel a fit with the design criteria and what that offers.

Though both these designs strive for fine handling and performance with comfort and dryness, the W17 by comparison, will be a comfortable day sailor—a trimaran of 'beach cat' type—quicker to build and lower in cost [than the W22]. She will both beach and fold readily, be great for a couple or single-handed and most importantly—be comfortable and sail well! I guess a small Discovery 20 would be one flattering way to describe her. Basic plans will be ready for early Spring 2010 and building help for first-time builders, as close as your email. More on the W17 under 'New Design Development' on my website.

A preliminary review of the new W22 trimaran design
The main target of the W22 design, is for those who want a fast responsive boat that is not only fun and rewarding to sail, but that also offers a drier ride than the average small multihull. Rather than giving up most of the boat volume for an enclosed cabin, the basic design will feature a 7' long cockpit for comfortable day sailing with friends but also have a low cuddy (with sitting headroom) for inside protection during a passing storm or the occasional overnight. The cockpit floor and the under-cuddy area, will be just above the waterline, so that these areas can naturally drain any water back from where it came. The boat will also be easily sailed single-handed. [The W17 also has the 7'-long self-draining cockpit feature.]

The design is being developed to be both easy-to-build and of relatively low cost, keeping in mind that overall performance in the sailing conditions that sailors typically most enjoy, is very high on my list of priorities. And by 'overall' performance, I mean seaworthiness, handling, stability, comfort, dryness, low maintenance, trailability etc., as well as pure speed. All of this was apparent with the original D25R and here is how she looked.

Magic Hempel

Now for a brief introduction of what the building a W22 will involve.
All three hulls will be quite rounded in section to give the lowest surface friction possible, though there will also be the option to build the amas using plywood for faster assembly and a slight compromise on speed. The rather unique cross section of the main hull can be seen in this preliminary Body Plan of the W22.
W22 HullI was recently asked (in 2008) as to why I did not retain the simple flat sheet form of the W17 hull? My personal thinking at that time was that the 17ft would be about as large a boat as can justify the simple form, as the hull cost and construction time becomes a smaller part of the total as size increases. 

[Note added Dec 2017: While I had always hoped to squeeze the maximum performance from the W17 hull forms, I became more and more convinced over 5 years of extensive testing, that they would not be the compromise that was first anticipated.    While the W17 form has a higher wetted surface and therefore more drag at low speeds (say below 4 kts), the box form is proving to create less wave, actually lowering mid-speed (6k-12k) resistance, making also for a drier boat, plus offering a bonus of improved leeway resistance ... so it can 'give something significant back' for the low speed loss.    This has therefore changed my overall conclusion that the form cannot be justified for larger boats ... so I am now reconsidering it for a larger fast-cruiser of about 10m. where having a shallow, flat bottom could prove useful, as well as being easy and less-expensive to build.  So watch for more development on what will be a very unique and original boat.   The W22 will retain it's round-bilge form in the style of my original Magic Hempel, but will retain the deep forefoot of the W17 and all my trimarans stay away from the 'banana hulls' that tend to aggravate pitching as well as add more wave-making than necessary.] 

In the case of slightly larger boats (like the W22), I think it's worth the extra effort to get the lowest resistance possible, so that the overall performance will better match the expense of their larger rig and all the other equipment, (mast, fittings, trailer etc.) that a boat needs. There are a lot of new boats coming out in the 20+ foot range and having spent a year or more to build one, I think one deserves the best overall performance one can get.  Regardless of whether it's justified or not, round bilge seems to always help resale value for such a boat too, as it's more often associated with professional boatbuilding. All these factors are less pertinent for a beach tri like the W17 and in that case, getting in the water with the least effort and still having a ball of fun, is the reason I intend to build a W17 for myself. Wing masts on both boats will make a difference too.
So back to the W22. The main hull will retain the flare just above the waterline that kept 'Magic' so dry, provided some extra lift, added to the interior space and also, looked good—all without lowering performance. Since 'Magic', many notable designers have adopted this flare and these include UK designers John Shuttleworth and Richard Woods as well as US designer Chris White and French designer Eric Lerouge—all of whose design offerings, I have much admired over the years. The underwater sections of all 3 hulls will be targeting the lowest wetted surface possible combined with a deep forefoot and a straight, somewhat tapered run out to the stern, rather than the approach of some designers who have preferred wider, squarer sections and sterns that give more space but only with higher wetted surface and more low speed drag.   I still much prefer deep U sections rather than Vee'd ones, in order to 1) get the buoyancy as low as possible and 2) keep the sides at the waterline as vertical as practical to keep wave-making at the water surface as low as possible.  While some claim a wider form might offer a planing ability, I am not one who agrees with that line of thought (see my website article on, Can a trimaran Plane?).   The overall design will be streamlined and attractive, yet also retaining flat working decks that are much safer to move around on. Cockpit seating will also have inclined backs and flat horizontal surfaces for maximum sitting comfort.

Initially, it is proposed that the underwater parts be built using strip-cedar, though the use of  foam core will be a recommended option for the amas. I personally, prefer a denser wood core for the lower body of the main hull as it provides excellent rigidity with lower material cost than a foam composite. Once a prototype has been built (one on each continent perhaps), the initial plan is to create a local master-mold for the lower part of the main hull and possibly make a fiberglass lower 'solepiece' available for future builders.  As this solepiece will also have the important knuckle built-in as well as a substantial vertical centerline girder, it will be extremely stiff and stable in shape and therefore well able to guarantee the successful completion of a good looking and high performing main hull.
(Most racers will confirm that stiffness equates closely to high performance.)

Once the lower curved section is built (either with wood strips or glass), then the easy, fun part can get under way. Basically, the sides are created by rolling plywood around and attaching it to the vertical flange of the lower solepiece. Temporary framework is set up on the solepiece to guide the placement of the topside plywood and once in place, temporary gussets will be added to guide the additional extension at the deck level. This is all relatively easy work as offsets will be provided to define the initial plywood shapes. The plywood sides will simply be lapped over the vertical flange of the lower solepiece and temporarily fixed with sheet metal screws while the joint (of FG mat and epoxy) cures. Once cured, the screws will be removed, the holes filled and the lower edge trimmed off flush with the flare to create a fair knuckle line.

W22 Trimaran Building approach

Note that the interior of the plywood will all be precoated with one cloth and epoxy. This very easy step (done while flat and horizontal) will not only provide a far better seal against interior water in the future but will add important stiffness to the panel against exterior pressure. The same approach will be used for the deck panels in both the main hull and amas. Typically the undersides of decks are rarely sealed watertight and particularly with amas, are very often the initial cause of failure when water gets into uncoated areas while the amas are stored upside down. For both the W22 and W17, that problem will rarely be an issue.

W22 ama prototypeAs noted earlier, the amas can be built using ones method of choice, though the rounded shape achieved with either cylinder molding, foam or strip cedar, will give the best performance. Here is a prototype of the proposed shape.

(The design will also lend itself to the use of 20' catamaran hulls as amas, if that's an option a builder prefers. However, as these may have less buoyancy than those of W22 design, the ultimate performance would likely be compromised.)

The approach of precoating the underside of deck panels will also extend to the amas and make for very rapid assembly as well as one with low future maintenance.

For the initial W22 model that will have demountable akas or crossbeams, a streamlined mast section is specified and preferred. These will simply sleeve into pockets created from layers of glass and be molded and strapped to the ama decks and sides with tows of carbon fiber. This concept has been well tested after I Trimaran aka pocketrebuilt the sockets on 'Magic' and here is what they finally look like. Very streamlined and professional and quick to use for assembly as no bolting is required.
As long as a demountable trimaran can be set up quickly with minimal outside help, then its certainly a very favored approach by many knowledgeable designers. The reason for this is that the beam is not as limited or controlled as it is for most folding systems and if the beam is too limited, the boat not only heels more than necessary but the boat cannot develop the same power under sail. Heeling can also add resistance, as well as frequently making the boat wetter than need be.
This is not to say 'the more beam the better'. There are both practical and design limits for overall safety but in my view, it's just preferable to not have sailing performance held back by the limits of a folding system when that might not be entirely essential. So if you're not confined to daily folding for a marina berth or a narrow launching facility, then I'd certainly take a good demountable into consideration. Set up time will only be about 20 mins. longer than for a folding system and the added overall performance (through greater beam and lower weight) for all the hours spent sailing, will more than repay that small inconvenience. And I've not even mentioned the faster build time and lower cost. But there will probably be a slide-out or folding option developed later on for those unfortunates who really need it.

Although a dagger board can always be accommodated, the base W22 design will incorporate a kick-up board below the cockpit floor. This is because many people will be sailing this boat in shallow inland waters and at the speeds likely to be developed, a fixed dagger board could well be the cause of avoidable accidents. [I still remember hitting an uncharted boulder in 8' of water at 6 knots with a nearly vertical dagger board. From the after cockpit, I was thrown totally in the air to land on a cabin-top winch and broke two ribs. After that experience, I now design all my dagger boards with either a sacrificial tip or a slight pivoting ability, to ease the impact].   To solve the resistance issues of centerboard slots, the slot will either be kept as short as possible and or have some form of gasket.
Because of the possibility of lifting the main hull significantly and therefore inviting rudder cavitation, the boat has been designed with 2 rudders in mind—one on each ama for maximum control. This also fits with the option of using the hulls from an existing suitable catamaran as then, the rudders will come with the hulls and at the most, might need slightly larger blades. [Twin rudders also free up the center hull for the outboard and/or swim platform.]

One other interesting thing about the W22 design is that it will include the design of a rotating wing mast that can be built at home. Although no guarantees can ever be offered on such designs due to the designer having zero control over both workmanship or the sailing conditions the mast will be subjected to, the design will be of proven heritage and offer significantly improved sailing performance over the more typical rigid, aluminum stick. Ultimately, the boat's performance will depend greatly on the efficiency of the sails chosen and on the skill and experience of the crew.
In closing this brief review, I will attach a general deck view and sailplan. Although these were sketched out when the design was first being envisaged, they still generally resemble the final design.

Deck Plan of the W22 Trimaran

Sail Plan of the W22 Trimaran
Preliminary Sail Plan

W22 Trimaran Preliminary Design

According to the build-time graph included with my Report on Small Trimarans (available through my website www.smalltrimarandesign.com), the 3 hulls should take about 400 hours. Depending on the level of skill, experience, tools available etc, the complete boat should take less than 1000 hours. An experienced worker will likely trim down these figures.

Potential owners have sometimes asked me about storage issues. To keep any boat 'in optimum condition', requires that it be kept under a ventilated cover as long as possible to protect it from rain, snow, wind abrasion and most importantly, the sun. As that is not always possible, at least one needs to cover the boat as often as possible.
Whilst in use, the boat should be kept clean by freshwater wash-downs and regularly sponged out to keep all internal areas dry. Interiors should also be ventilated and awnings used to cut UV light whenever weather or circumstances permit.

In my clearly biased opinion, the major benefits that separate the W22 trimaran design from other small trimarans on the market will be this;

So this boat will be for:

Someone who wants to sail fast with a partner or some friends, yet stay dry and comfortable.
Someone who really appreciates the feel of a thoroughbred at his fingertips and the feeling of high efficiency, even at low wind speeds.
Someone who mostly day sails but occasionally needs protection for camp-aboard trips.
Someone who has the skills and place to build their own boat but not the money for more exotic options like the folding F-22.
Although future owners will decide this, its eventual popularity could justify a significant following and this would help retain high resale value. Ideas for a class association are already being discussed.

To help potential boat owners understand more about the materials and design of these fascinating craft, I am happy to refer them to my quasi-technical small-tri website, where over 50 articles* are now posted (Dec 2009), with more to come. There's no purchasing hype here—just solid, well researched data, aimed to inform in as unbiased a manner as my experience permits.   (*by 2021, now well over 200 articles posted with an average of a new one added each month)

Through my website, one can also submit specific questions that concern potential small-tri builders and owners and I will do my best to answer them as time permits. Those who decide to build to one of my designs will have direct and reasonable access to me through email, to answer any query they may have. And such builders can be confident that my designs have been well thought out and ultimately, offer above average performance.

Mike Waters, December 2009


Originally written Dec 2009, released to Website, July 2010

Footnote: Mike Waters was recently invited to contribute an article to Multihulls Magazine on "Considering a Small Trimaran?". In this article, the author outlines aspects to look for based on his personal knowledge and experience with small tris. You may read this article, published in two parts in the July/August and September/October 2010 issues at the following links: Considering a Small Trimaran? - Part 1 and Considering a Small Trimaran? - Part 2


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