Multihull / trimaran mindset in Europe?

Having our office in Stockholm Sweden we are of course influenced by local multihull activities, which as I wrote in a previous blog entry are growing substantially. Of course multihull entries in races are still a fraction of the total however it is being generally recognized that in the last one or two years a lot of races now as standard are open to multihulls. Racing is done according to the Swedish LYS rating rules. This rating also allows to appoint a total winner among all classes (mono and multihulls), an opportunity which many organizers use.
Of course it is quite tough to win overall with a multihull, however it adds to your ego passing through fields of monohulls classes, especially since one the last few years enjoys admiration rather than a puzzled or scared UFO encounter facial expression.

Multihulls also are quite active on Lake Geneva with their big racing event Bol d’Or coming up. Obviously Mr Bertarelli and the Décision 35s catamarans are an attraction (http://www.decision.ch/ANG/default.htm) on the lake, however on the very extreme end of multihulls. Soon having two Seaon 96crb on Lake Geneva we of course would be delighted to grow a fleet for racing and high performance cruising there.

Obviously there are a lot of multihull activities around Europe – it would be nice to share some experiences on the multihull mindset among monohull sailors around Europe. I assume many of us at least initially have encountered arguments such as “multihulls cannot sail upwind”, “multihulls cannot tack”, “not appreciated in harbours” (due to space needed) etc. however I assume we have passed this first level of “scepticism”.
What is your experience? Are multihulls gaining admiration and interest? Once tried most sailors are “hooked on the feeling”? What is the multihull mindset among monohull sailors?

/Jan

Carbon epoxy laminate for multihulls

Our Seaon 96crb is fully built in pre-preg carbon fibre (for more on information on our building technology please check production” on our web site). Occasionally we get comments that suggest a laminate based on carbon fibre is more fragile than a glass fibre polyester laminate and carbon there fore not being suitable for normal boat handling e.g. when docking.

Let us look at some “theory” behind a laminate.
Most modern boats are built with a sandwich laminate meaning that instead of a solid laminate it is built with a laminate on each side on both sides of a foam core (early days balsa was used – and to some extent still is). Separating the inner and outer laminate skin by a foam core gives a lighter laminate than building a solid laminate.

When dimensioning a laminate, considerations have to be taken to the various forces that will impact on the laminate such as structural loads and practical boat handling e.g. local impact when docking. Furthermore the type of fibre and resin (normally polyester, vinyl ester and epoxy) selected will affect the dimensioning of the laminate. Typically carbon fibre is approx 1,5 times stronger and approx 2,5 times stiffer than glass fibre compared to weight, i.e. a carbon laminate of the same weight is 2, 5 stiffer than the glass fibre laminate meaning it will distribute physical impact over a wider area of the core. Practically this means if the same force is used for impact on a glass fibre and carbon fibre laminate of the same weight, it will create a deeper deformation in the core of the glass fibre based laminate.

The total laminate strength however is also determined by the combination of fibre and resin (the matrix). Polyester has a maximum elongation of approx 1,5-2% before it breaks. The equivalent value for epoxy is approx 4-6%. This means that a polyester based laminate will be limited to a deformation of 1,5- 2% before breaking. If the laminate is based on epoxy it has the potential of making use of the full strength of the fibre.

The rumour of carbon fibre being fragile may be based more on an imagination of a thin eggshell layer of carbon than on real life experience. For practical reasons however, it is not always possible to use the full advantages of the additional strength of carbon fibre and thus saving weight because of the laminate strength needed for practical handling (e.g. docking, walking on deck etc) of the boat exceeds the dimensioning due to structural forces.

In addition to the above it is sometimes claimed it is more difficult to repair an epoxy carbon fibre laminate. Thin laminates in general are more difficult to repair whether based on polyester and glass fibre or epoxy and carbon fibre, however it is not more difficult to repair an epoxy and carbon fibre laminate.

Summing up - An epoxy carbon laminate is ideal for a light weight boat since it is considerably stronger than the equivalent polyester glass fibre laminate. This is also the reason why we have used an epoxy carbon laminate for the Seaon 96crb. Using carbon fibre for a racing monohull may well be worth the efforts since every 1/100 of a knot counts, however the weight gain in percent is considerably smaller for a monohull than for a multihull since the keel weight is a major part of the total weight. On a multihull every saved kilo has direct impact on the performance. As an example, saving 350 kilo on a multihull such as the Seaon reaching a total of 1400 kilo is a weight reduction of close to 25%. Saving 350 kilo on an e.g. 34 foot monohull performance cruiser/racer coming down to a total of 4000 kilo is only a saving short of 10%.

We strongly believe using an epoxy carbon fibre laminate for the Seaon 96crb has been very well worth the effort. Together with polyurethane painted instead of gel coated surfaces, we have decreased the need for power equivalent to approx. 13 square meters of sail area which also allows us to use a shorter mast. A light boat is more fun to sail in light winds and the reduced need for sail area and mast length will make the boat more comfortable to handle at increased wind power.

/Jan

Lidingo Runt – Stockholm’s major opening race of the sailing season. "HiQ" a 60 foot trimaran 2006: 55 minutes. "HiQ" 2007: 5,5 hours!

On Saturday May 12th the annual Lidingo Runt race was held in very light winds, if any wind at all. Last years race caused a problem for many boats due to very heavy sudden gusts of 30+ knots. This year only 51 boats out of 450 managed to cross the finish line within the maximum time set to 7 pm. A large part of the boats that managed to fulfil the race were multihulls….

Lidingo Runt is gathering more than 60 trimarans and catamarans thanks to many multihull missionaires like Magnus Olsson (60 fot trimaran and Volvo Ocena race sailor) Mats Leander (Chairman of Swedish Catamaran and Trimaran Sailors Association) and Mats Johansson (of Gransegel).

An excellent site for more information on Lidingo Runt and sailing News in “Scandinavian” is http://www.skota.se/.

Trimaran float (ama) buoyancy

From time to time we get questions like: “Can you sail on one hull only” or “On one of the videos you can see a float almost submerged in the water, does it not indicate to little buoyancy”. (In one of our old videos a sequence was shown where the float was partially submerged. This we thought would show how kind the Seaon behaves, however it seems to have caused more questions than answers.)

Basically these questions boil down to: Why don’t you have more buoyancy in the floats? This is a relevant question. I will try to elaborate on this.

Already at the requirement specification phase the float displacement is to be defined by the intended use of the boat: Racing without interior, racing/performance cruising etc.

For racing purposes only, the float buoyancy would be generous enough to be able to lift the main hull out of the water and the leeward float will carry the whole weight of the boat. So why are not all trimarans designed this way? Sailing on one hull will obviously improve performance due to reduced wetted area, however you will also sail very close to the stability limit of the boat, meaning you will be sailing close to capsizing. A small increase in wind force could turn the boat upside down.
Obviously this needs very active and proper sailing by an experienced racing crew. There is little indication whether being on the right side of stability (and yes….there is occasional capsizing with racing trimarans and in rare cases also with cruising trimarans).

Another important consideration is the volume in the float compared to the length. If you design a light weight racing boat to a certain length and want it to fly on a hull it is possible to achieve this with a slender float design that cuts the waves nice and even in lights winds. On the other hand, if you design a heavy cruiser with the same objectives, the float will be blunt and will have to much reserve buoyancy in light winds, witch will cause the boat to respond to excessively to wave action and slow the boat down in choppy light wind conditions when sailing upwind.

How much displacement and its distribution through out the float is part of the sailing characteristics of the boat. Amongst other it influences performance for upwind sailing, power reaching etc. Furthermore it defines the “predictability” of the boat. It is very important to design a predictive and smooth behaviour of the boat. One does not want a boat that reacts with surprises. To achieve this it is important to have the longitudinal buoyancy distributed in a suitable way. For power reaching you need a lot of volume in the bow, but not too much to affect upwind performance. When pressing the boat hard upwind, it is also very important to have enough reserve buoyancy in the aft part of the float to avoid that the boat trims excessively backwards in longitudinal direction, when the boat is hit by a hard wind gust (due to sail center of effort moving excessively backwards when e.g. trying to luff to depower).

Summing up: There is no one single design that is right or wrong – it is the intended use that decides the design. A boat intended for top speed power reaching will look different than a boat optimized for upwind sailing and as mentioned, total weight of boat (building technology i.e. weight of laminate, interior, cruising amenities etc) also is part of the design strategy.

The Seaon 96crb design objective was to create a high overall performance (…if I remember correctly the marketing spec was: “The damn fastest boat with interior that a family can handle”) and to be as versatile as possible in various winds and courses. Also the objective was to minimize the power needed (mast length and sail area) for easy and safe handling, which is why we put some real efforts into the building technology (carbon, pre-preg etc. – for more information check our web site under “Production”). A light boat is fun to sail in light winds and the reduced need for power will make it easier to handle in tougher conditions.

We spent a lot of time and energy in designing the floats (and the rest of the boat of course!) and are extremely pleased with how well the performance, kind and predictable behaviour of the boat came out.

/Stefan

New web site!

Here we are live with our new website and very excited about the new the “Blog” and “Forum” functions, which hopefully will allow more dialogue and discussions! We though have to admitt these functions are quite new to us – so I hope there is some patience and understanding while we are getting in to this.

There has been little news from us for a while. Major reason for that is due to establishing our own production caused by unsatisfactory outsourcing acitivities. This is a chapter for itself - some of it is addressed earlier in this blog and is also why the website is somewhat more production oriented now.

To launch the new web has been a challenge and as always it means hard work defining and fulfilling: "What is it that our web visitors and potential customers really want to know and see?" We have to admit that we for sometime have been so overwhelmed by our own almost religious experience in multihulls, that we potentially forgot that it is not so obvious for everyone, especially if you have invested in an upmarket monohull.

The major challenge is to present the advantages of a multihull….and of course our Seaon 96crb.

Characteristics like SPEED, COMFORT, TECHNOLOGY AND DESIGN….and on top of that CARBON are not enough to justify the advantage. Obviously this can be applied to a lot of yachts. So how do we tell we are twice as fast (sometimes three times…)? And about our technology – how many yachts are produced in “pre-preg” to achieve top quality light weight laminate….and not only “carbon reinforced”, but 100% carbon? And sailing with very little heeling but still with great power etc.?

Usually when thinking of multihulls many sailors think of top speeds….and yes they are fast! So far I have logged 24, 2 knots (not to steel Mats Leander’s official record 24,8 knots in SWE-1) with the Seaon 96 with 4 persons and (limited!) luggage for a week of racing. That was of course fun, but I much more enjoy sailing in 15-18 knots with Ulrika on a nice day in a sea breeze (approx 10-14 knots of wind in Stockholm on a good day) or even sailing 6-10 knots in very light winds. That to me is the feeling! Before when racing with larger monohulls I did not go cruising. It just wasn’t fun with the kind of yacht the family can handle. Now, when sailing multihulls it is almost the other way around. Everyday sailing is great fun, almost like a dinghy (but not as wet…) and I have the full interior with bunks, galley, marine head and the freedom to go virtually anywhere – remember, with rudder and daggerboards up there is very little draft.

And about design – trimaran is a challenging concept, especially since many of us have a touch of vanity in us. You want a yacht that sticks out at the dock….in positive way that is! Having (over)heard someone describe the Seaon “as hot as a Ferrari” (and that with a full interior) certainly appealed to my vanity.

However, all the above are just the underlying parameters to achieve….we certainly looked for the expression that describes it all and we could not find another way to say it than the “FEELING”. It is really about that.

Have we succeeded in conveying this “Feeling”? How many more out there "feel" the same?

/Jan