trimaran w22

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:

What is my background?
How did I get into multihulls?
What is my design approach?
What new designs am I working on?
What are my thoughts on storage?
What is special or unique about my designs?

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!

MY CONVERSION 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!

SO WHAT IS MY TYPICAL DESIGN PROCESS? 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] .)

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.

[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.

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.

(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.

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.

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.

Most bang for the buck—assuming 'your bang' matches the chosen design criteria
Greater dryness and overall sailing comfort
A proven concept based on a well tested design, and subsequently 'tweaked' by someone with both experience and appropriate knowledge
Attractive looking
Excellent performance in the most typical sailing conditions, [aided by a unique wing mast design]

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 www.smalltrimarandesign.com

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

"Have a question or comment about the W22? If so, feel free to use our Questions & Comments Form to submit them to the designer." —webmaster

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A few trimaran design questions

Discussion in ' Multihulls ' started by FantasyTrimaran , Dec 20, 2019 .

FantasyTrimaran Junior Member

On trimarans... Why are the floats usually shallower at the aft ends than the fore? The floats of many, but not all, trimarans that I've seen appear to be narrower and taller at the front ends and shallower - and sometimes wider, sometimes not wider, at the aft ends. Is this the best design for a specific reason? Is it to reducd the "wetted area" of the boat overall by "slicing through" the water at the front ends and then transitioning to "floating upon" the water towards the back ends? Some of the floats seem very thin and shallow at the back, or far too wide with a sort of bulkhead transom at the back. Are such design choices losing something by way of flotation/bouyancy volume? Also the transomed floats would, I think, be worse with a wave pushback - thw transoms tending to "catch" and "dig-into" the water if pushed backwards in rough seas or something, like someone catching their heel on a loose rug behind them - therefore presumably being more likely to picthpole, backwards. Compared to floats that are narrow at both ends, which would presumably be more likely to slice through the water rather than catch on it. Is this just a matter of Make your choices and take your chances? Both designs being valid but just with different strengths and weaknesses? Blunt and shallow, versus tall and narrow, symmetrical with the front?

fishwics Quiet member

It depends, surely, where you want the centre of buoyancy of the float. The sail force acts somewhat forward of abeam, depending upon the point of sailing. Ideally the CB of the float should be on the same line, but as always there is a compromise required. Boats likely to sail a lot at low apparent wind angles (i.e apparent wind well forward of the beam) can use floats (or foils) with a CB/Centre of Lift further aft than slower boats (that may at times have the apparent wind aft of abeam).

Niclas Vestman Senior Member

Conclusions from my own research as a complete amateur: 1) yes, float bows are almost always designed to slice, more or less. Mainly depending on float volume vs boat displacement. A 150% volume vs displacement makes it possible to sail on one float, lifting the main hull. Like the SeaCart30. Around 100% will be burried enough to act as a break, reducing apparent wind speed and also sail forces thus reducing risk of capsize. 2) load transfered to the floats vary a lot depending on wind and point of sail. Although the forces often act to burry the float bows. If the bow is shaped like an axe, the shape is quite neutral as to how deep the bow is forced down by the sail forces. 3) the forces acting aft on the floats vary less. Meaning it will lie quite flat on the water no mater the conditions. 4) early tri designs had canoe shape floats, pointy at both ends, as it was assumed to be a optimal shape to reduce resistance. But later it was found to be false for most cases. 5) Floats are design specific. An extreme racer will have different design compared to a cruiser. But both will probably have flater stearns. This often gives better speed, pitchpole resistance but most importantly significantly reduces hobby horsing. Still there are many more design considerations for floats. Eg, how many degrees they lean inward while the boat is level at anchor. Also, are the trimed downward back to front. And are they shorter than the main hull or maybe even protruding, like in the new Dragonfly 25?(forgot the name. Maybe 26). Among many more design aspects. As for tripping backwards, i would say that this scenario is almost non existent as to the sort of movement, and also the float stearn being way to small to offer enough resistance making a backflip impossible. .... Still just my amateur opinion. Best regards

tspeer Senior Member

FantasyTrimaran said: ↑ On trimarans... Why are the floats usually shallower at the aft ends than the fore? ... Click to expand...

oldmulti Senior Member

Tom. Thanks for Shuttleworth's Great Brittany Ferries article. Modern OMRA tri's now sail more like catamarans with only one hull in the water and 2 hulls in the air. Result outer hulls more shaped like cat hulls. For an older style tri or pure cruiser the article is very valid.

Yes, the article is a bit dated, but it goes to the OP's question as to why trimaran amas are deeper forward. Diagonal stability is typically the trimaran's weak point, and they need lots of reserve buoyancy in the ama bow to prevent digging in the ama. Been there, done that, spent the night on the overturned hull.

W17 designer Senior Member

Greetings, Should Fantasy Trimaran not already be aware of the Trimaran Design Info shared via my website www.SmallTrimaranDesign.com , perhaps he and others will find this helpful. Although written originally for the W17 hull design, the aspects discussed affect all trimarans and should help to answer the original question. Review of W17 Hull Forms https://smalltridesign.com/W17/w17-design-approach.html If I remember correctly, I think this article links to two others which also address related aspects, but in case not, here are the links and hope readers will also find this of interest. DiagonaL Stability: Multihull Diagonal Stability https://smalltridesign.com/Trimaran-Articles/Diagonal-Stability-of-Multihulls.html Efficiency of Simple Shapes: https://smalltridesign.com/pdfs/W17ProBoatOctNov2017.pdf I will add that although I think you will find my personal design thoughts are totally in line with those of John (Shuttleworth), the execution of them is significantly affected by boat size, as it's often easier to get closer to the ideal on a larger boat, whereas more compromise is necessary when the boat is short. Mike/ .. and a great 2020 to all.

For information only and only applicable to larger racing tris the following add shows the float hull lines for a 60 ft racing tri's.

Attached Files:

Orma floats for sale..png.

Thanks for sharing that ... we don't often get to actually see the lines I'd call this 'a good compromise shape' taking into account that one shape will not perfectly serve all operating conditions. My own W22 has a very similar form that can be summarized like this from bow to stern. Deep forefoot for fine, early water separation and longest waterline; semi-circular underwater section for lowest wetted surface; deep chest with most buoyancy forward (like a fish) that helps to move the CB well forward of the CB of the main hull. This is recommended (by me anyway) so that the two are not in line. This offset dampens pitching in my experience, so all my amas have this feature. The tail is as clean and 'fish-like' as is possible ... but particularly on the smaller boats, the stern has to be at least Vee'd in section, if not somewhat U'd, to retain helm and stability balance when heeled. If you don't plan to sail with it depressed very much (good luck!), you might get away with a broader stern for better downwind performance (as Kurt Hughes often does), but there are compromises with that. Too much buoyancy aft not only defeats the forward CB attempt, but can lift out a central hull rudder and you lose steering control. I personally think that its often forgotten that the ama is NOT just a buoyancy pod ..its a hull that you are sailing on .. and its immersed volume actually replaces much of the main hull volume when sailed with a heel. So the more efficient you make the ama, the better the overall performance can be. I personally felt that early Farriers were too banana shaped and could use more bow in the water with an earlier immersion of buoyancy. Especially after a buddy pitchpoled his F25 on a small, flat lake! Then additionally, there are other compromises needed that have nothing to do with hydrodynamics .. such as having a decent deck area to stand on (to fend off) or to give a good structural connection for the aft beam that may well be very near the aft end. Yes, amas can have much variance for many different reasons, but my advice is to ask the designer why he did what he did. If he doesn't have a justified reason, then just forget you saw it ..... Mike