small trimaran sailing

Yachting Monthly

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Astus 20.5: Fast, fun and affordable trailable trimaran

David Harding
August 20, 2021

For fast yet undemanding sailing, easy trailing and simple camper-cruising, the Astus 20.5 trimaran is likely to find wide appeal says David Harding

The Astus 20.5 is taut and responsive to sail. Credit: David Harding

Product Overview

Fast and easy to sail
Can be trailed behind a small car
Easy to reduce beam for marina berthing
Less accommodation than a monohull of similar size
Rigging process could be simplified
Slightly stark interior finish

Manufacturer:

Price as reviewed:.

Boats that are small and light enough to keep in your driveway and trail to where you want to sail make a lot of sense.

One drawback, however, is that they tend to be slower than bigger boats – especially if they’re of a size and weight that allows them to be easily managed short-hand, both afloat and ashore.

If you want to sail from Poole to Weymouth for the weekend in a 20ft trailer-sailer, for example, it might take a while.

This is where speedy trailable trimarans like the Astus 20.5 come in.

When I sailed its predecessor, the 20.2, about 10 years ago, we regularly hit 15 knots on a reach without breaking sweat and maintained an easy 6.5 knots upwind.

This 20 footer can match 50 footers for speed. Credit: David Harding

You can cover a lot of ground at those sorts of speeds.

I first met the Astus 20.5 at the Düsseldorf Boat Show in 2019. Since it’s a newer boat and designed by no less a design team than VPLP, I had high hopes that it would offer even more than the 20.2.

Quite apart from the sailing potential, the trailing is as simple as can be with a boat like this.

If you choose the resin-infused hull, the Astus 20.5 weighs under 500kg (1,100lb), or just over 500kg with the standard solid laminate.

The lighter weight means you can use an unbraked trailer , saving money, maintenance and yet more weight, so you can trail it behind a normal hatchback vehicle.

Getting somewhere fast under sail is one thing. Having somewhere to sleep when you arrive is another.

The Astus 20.5 is simple to sail for two people. Credit: David Harding

Though its cabin is smaller than on a monohull of similar size, the Astus provides seating, stowage and space for a companionable couple to be able to stretch out.

Then of course you have the trampolines each side on which you can rig a tent for more sleeping space.

The opportunity for a sail on the Astus 20.5 finally came when Hein Kuiper of Boats On Wheels brought his first demonstrator to the UK.

In fact we went out twice – first for a photo session in Poole on a brisk winter’s day and then a few months later in Chichester Harbour.

Since the boat arrived in Poole on its trailer, I was able to see how it went together.

Pulling out the hulls is pretty straightforward: their aluminium beams slide in and out of the fixed beams on the main hull. You can do that ashore or afloat.

There’s nothing complicated about raising the rig, either, and it can all be done singlehanded .

The whole process, from arriving with the trailer to sliding the boat into the water, took Hein a couple of hours or so the first time or two (comparable with a monohull of similar size, he reckons) but would undoubtedly get quicker with practice.

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Dragonfly 28 Sport

Whether you choose the standard or the Sport version, the mast is the same height.

The difference is that the latter comes with a square-top mainsail to give appreciably more sail area.

If you want to save as much weight as possible and make raising and lowering the mast easier, you can have it in carbon. A wing mast is another option.

The rig and hardware don’t appear to be modified in any way as a concession to the boat’s trailer-sailer nature.

Here and there, the odd ready-made loop or strop would save fiddling around with bits of line.

It is basic down below but there’s seating and sleeping space for two people. Credit: David Harding

All that is forgotten as soon as you’re under way.

On our second outing, once the electric outboard had pushed us out of Northney Marina – where the boat proved to be surprisingly manoeuvrable with the centreplate fully down – we headed off on a beam reach at 12.5 knots in 12-15 knots of wind.

In most boats, 12.5 knots would be going some. In this 20-footer, it felt perfectly relaxed.

Over the course of the following couple of hours we covered every point of sail including, of course, reaching under spinnaker.

With the gusts rarely exceeding 16 knots in the flat water of the harbour, we didn’t quite manage to break 15 knots.

It wasn’t a bad speed-to-effort ratio nonetheless.

The boat felt rock solid the whole time, and I knew from the photo session in Poole that she could carry the kite on a beam reach in appreciably more wind than we had in Chichester.

It is easy to reduce the beam of the Astus 20.5 for marina berthing. Credit: David Harding

It’s hard to imagine that 20 knots wouldn’t be perfectly achievable.

Upwind we maintained between 7 and 8.5 knots most of the time.

As you would expect, you need to keep the bow down a little to maintain full power.

You also need the purchase of the 6:1 mainsheet to maintain sufficient tension in the upper leech. It makes a big difference.

You won’t need more than two people to go out and have fun on the Astus 20.5. Credit: David Harding

Tacking was pretty positive provided we had adequate boatspeed going into the tack, and leeway appeared minimal.

All told the Astus 20.5 was great fun to sail and easy to manage two-handed.

There was little for a third person to do except enjoy the ride or contribute to the righting moment by joining the helmsman on the windward trampoline.

If you were racing, you could use a longer tiller extension and fit toe-straps to maximise the advantage.

Beating our way back up the harbour, we demonstrated the windward ability of the Astus 20.5 by sailing straight past a 15m (49ft) monohull.

Creature comforts aboard the Astus 20.5

David Harding has been testing boats for decades and is also a sailing photographer

Above decks the Astus offers a vast amount of sitting and lounging space thanks to the trampolines.

Down below, the hull’s narrow beam makes things cosy but you still find a seat either side, space for a chemical toilet under the aft end of the berth and a fair amount of stowage beneath and to either side of the companionway.

The centreboard is offset to port to leave the middle of the boat clear.

The finish is simple and uncomplicated, largely to save weight. There would be plenty of scope to fit a slide-out galley and devise lightweight stowage solutions to make better use of the space.

Astus 20.5: the test verdict

More than anything else, this boat is tremendous fun.

She feels taut and responsive to sail. I found that it took an hour or so to begin to find her sweet spots, but after that she just makes you want to sail her.

She inspires confidence and is easy to handle, too. In most conditions you could manage perfectly well single-handed and for cruising you won’t need more than two.

The Astus 20.5 has less accommodation than a monohull of similar size

Then there’s the speed. No matter whether or not you’re in a hurry to get anywhere, it’s easier to slow down in a fast boat than to speed up in a slow one.

Speed is fun in itself, and it’s hard not to enjoy sailing straight past a monohull more than twice your length.

Niggles are relatively few.

I thought the rudder blade could do with a touch more balance and I wasn’t sure that the fixed end of the 2:1 jib sheet was quite far enough aft on deck.

Other than that, it all works.

Hardware is mostly from Harken and the spars are by Sélden, so there’s no skimping in these departments.

Would she suit you and your crew?

The Astus 20.5 will attract attention. Several people stopped for a chat and to admire her back in Northney having seen her on the water.

If you’re a dinghy sailor moving up but not ready to slow down, this is a good choice.

Just as much interest is coming from big-boat sailors moving down or wanting a second, smaller boat that still has a good cruising range. Few boats of this size go so fast with so little effort.

The Astus 20.5 is ideal for exploring harbours, estuaries and rivers

As for the inevitable monohull-versus-multihull debate, there are trailable, family-friendly boats of this size with one hull that sail very nicely.

I have clocked over 12 knots in one or two, but only under spinnaker, with good sailors on board and not for sustained periods.

As long as you’re prepared to accept that sailing regularly at double-figure speeds means sacrificing some interior volume, the Astus could suit you perfectly. And for exploring harbours and estuaries, camper-cruising and nudging into the beach, it’s absolutely ideal.

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The complete list of trimarans.

There is no single trimaran that is best for everyone. Where some prefer luxury cruisers for long trips with family and friends, others might opt for a high performance racing tri for thrilling rides at breakneck speeds. With the recent spike in trimaran popularity, these days there is a perfect tri for every sailor. So to help prospective trimaran owners decide which boat is just right for them, we here at WindRider have put together a comprehensive list of the best trimarans on the market today! Read through for simple at-a-glance trimaran comparisons of boats both big and small, exhilarating and relaxing, and for all price points.

Jump to a specific sailing trimaran: Neel Weta Corsair WindRider Dragonfly Catri Astus Hobie Sea Pearl Farrier Sea Cart Multi 23 Triak SeaRail Warren Lightcraft Diam Radikal Challenger

Known for their award-winning luxury trimarans, NEEL is based in La Rochelle, the capital city of sailing in France. NEEL trimarans are built for fast cruising with an average cruising speed of about 10 knots, and are even configured to facilitate that sustained speed under motor propulsion. The NEEL 45 was notably named Cruising World’s Most Innovative Vessel in 2013, and by all accounts is an easy-to-sail, high performance boat that is just plain fun.

At a glance:

Models: NEEL 45, 65

Length: 45’ – 65’

Cost: $$$$$

Use: Luxury cruiser

A fan favorite, Weta trimarans are fast, stable, and remarkably easy to rig. This single-sailor tri has a capacity of up to three, and the ease with which it can be transported and stored makes this a great, versatile boat for beginners. The Weta was named Sailing World’s 2010 Boat of the Year, and one ride is enough to know why: simply put, the Weta is an absolute ton of fun to sail regardless of skill level.

Models: Weta

Length: 14’5”

Cost: $$ $$$

The high-end Corsair trimaran definitely holds its own in the categories of versatility, performance, and convenience. Boasting a rigging time of 30 minutes from trailer to sailor , the Corsair 42 – whose convenient folding amas makes trailering possible – is a simple option even for single sailors, though cabin space is suitable for two adults. These boats are wicked fast, capable of reaching speeds of 20+ knots, and were made for skilled sailors seeking solid construction and high performance vessels, not for beginners.

Models: Pulse 600, Sprint 750 MKII, Dash 750 MKII, Corsair 28, Cruze 970, Corsair 37, Corsair 42

Length: 19’8” – 37’

Cost: $$$$ $

Use: Sports cruisers

Built for the sailor who wants to maximize the joys of sailing while minimizing any hassle, WindRider trimarans are notoriously fast, very safe, and a blast to sail from start to finish. With several models that can hold between 1 and 6 riders, including adaptive designs to allow participation from sailors of all levels of mobility, there’s something to suit every sailor’s needs. The WindRider 17, an exhilarating ride perfect for families or camper sailors, has been known to reach speeds of up to 20mph. This easy day sailor goes from trailer to sailing in under 30 minutes and is sure to fit in perfectly with whatever adventures you have planned.

Models: WR 16, 17, Tango, Rave V

Length: 10’11” – 18’3”

Cost: $ $$$$

Use: Day sailor

The Danish-built Dragonfly trimarans come in a variety of models ranging from 25’ – 35’, all known for their spry performance, comfortable ride, and ease of use. Every model comes equipped with the unique “SwingWing” feature, a motorized system that can unfold the amas even while the boat is already underway – making it accessible to marinas and slips, and even makes trailering possible. Perfect for those who don’t want to sacrifice their comfort for high performance, the Dragonfly can breeze along at 13 knots while remaining one of the quietest compact cruisers out there.

Models: Dragonfly 25, 28, 32, 35, 1200

Length: 25’ – 39’

Designed for both safe cruising as well as for high speed racing, Catri trimarans will make your day. Especially noteworthy is the Catri 25, a stable yet wildly fast foiling trimaran with accommodations for up to 6 people. With profiles optimized for speeds of 25+ knots when foiling, this is no beginner’s sailboat. The special attention paid to stability in the foil design allows the Catri to be a single sailor vessel, even at foiling speed, with no special physical abilities. Whether you’re taking a small crew for longer rides at shuddering speeds or bringing the whole family along for a shorter, but still thrilling sail, the Catri is truly one of a kind.

Models: Catri 25

Length: 25’

Use: Cruiser/racer

A popular brand of trimaran in Europe, Astus has recently made its way to the US market to the delight of sailors on this side of the pond. Designed to offer maximum pleasure with minimum hassle, all models of Astus trimarans are fast to set up, quick on the water, inherently stable, and always a joy to sail. Their outriggers are mounted on telescopic tubes for easy stowage and towing, and can even be extended and retracted on the water for access to narrow passageways and monohull slips in marinas. With models in all sizes and price points, Astus trimarans are a great option for any sailor.

Models: Astus 16.5, 18.2, 20.2, 22, 24

Cabin: Some models

Length: 16’ – 24’

Use: Sport cruisers

HOBIE ADVENTURE ISLAND

Great for beginners and adventurers alike, the Hobie Mirage Adventure Island series is nothing if not just plain fun. With the option to use as a kayak or as a very basic trimaran, the Hobie is transportable, versatile, unintimidating, lightweight, and wonderfully affordable. The pedal system known as “Mirage Drive” allows a person to pedal the kayak using their legs for an extra kick of movement in slow winds. Amas tuck close to the main hull for docking or car-topping, adding serious ease and convenience to the exhilarating experience of the Hobie.

Models: Hobie Mirage Adventure Island, Mirage Tandem Island

Length: 16’7” – 18’6”

Use: Convertible kayak/trimarans

Best known for its use in camp cruising excursions, the Sea Pearl offers a roomy main hull and particular ability to sail in very shallow waters, making beaching and launching a breeze. The lightweight Sea Pearl trimaran is easy to tow, and the larger-than-expected cabin opens this vessel up for overnight adventures with plenty of storage space. The simple design makes the Sea Pearl notoriously low maintenance, and the ease it takes to rig and sail it add to the overall delight of owning this boat.

Models: Sea Pearl

Length: 21’

Use: Camper cruiser

Quick, lightweight, roomy, and trailerable, Farrier trimarans are made for versatility to fit every sailor’s needs. Different Farrier models are available in plan or kit boat form for those who appreciate building their boat themselves, but of course, also as the full production sail-away boat for the rest of us. Single-handed rigging and launching takes under 10 minutes from start to finish, minimizing hassle and getting you on the water fast. All non-racing Farrier designs use a minimum wind capsize speed of 30 knots or more to ensure safety for all those aboard. Add the roomy cabin and high speed capabilities to the equation and you’ve got a boat that is great fun for everyone.

Models: F-22, 24, 25, 82, 27, 28, 31, 9A, 9AX, 9R, 32, 33, 33R, 33ST, 36, 39, 41, 44R

Length: 23’ – 39’4”

Cost: $$$ $$

Use: Sport cruisers/racers

One of the biggest names in the game, SeaCart is internationally noted for its high performance trimarans that far exceed expectations for a production boat of its size. The SeaCart trimaran performs as brilliantly off the water as it does on with its super-light and efficient harbor folding system, making light work of trailering. Notoriously easy to manage and maintain, the SeaCart 26 One Design is the ultimate day racing trimaran, designed for both course and inshore/coastal distance racing. Absolutely worth the international buzz it has garnered, the SeaCart is a thrill from beginning to end.

Models: SeaCart 26

Length: 26’

A high performance racer class, the Multi 23 is a lightweight, powerful trimaran known for its wicked speed of up to 25 knots. Multi trimarans of both available configurations were designed to give beach cat thrills and speed without any of the stability or seaworthy concerns. Open ocean sailing is no issue for the Multi’s big bows, which do their job to keep her stable. Built for sailors with a need for speed, the Multi makes a perfect weekend boat for racers, especially those with a taste for boat camping.

Models: Multi 23

Length: 23’

Another dual outrigger sailing kayak/canoe design, the Triak trimaran was designed to be effortless and fun, especially for beginners. Paddle the kayak with sails furled, use the foot pedals for an extra kick of momentum, or sail with just the mainsail – the only boat in its class to feature an asymmetrical spinnaker – for exhilarating speeds and a blast on the water. Car-top the Triak anywhere for a quick sail or plan for a week long expedition, but always count on having a great time on this easy little boat.

Models: Triak

Length: 18’

Use: Convertible kayak/trimaran

SeaRail trimarans are known for being affordable, light weight, trailerable trimarans that offer the perfect combination of exciting and relaxing experiences to a wide range of sailors. Whether it’s day sailing with your family, resort or camper sailing, SeaRail trimarans are ideal leisure vessels. Leave the hassle to the other boats – the SeaRail takes you from trailer to sailor in 15 minutes. But don’t let its reputation as a leisure tri fool you: if speed is what you want, rest assured that the SeaRail can deliver that as well.

Models: SeaRail 19

WARREN LIGHTCRAFT

Warren Lightcraft trimarans , another example of a convertible kayak-to-sailboat option, are known for their aesthetically pleasing designs that are also, as the name implies, very light for simple transportation and ease of use. Convert the kayak into a fast, high performance sailboat in just minutes, fly around on the waves all day long, then simply car-top the 68lb Warren for a maximum enjoyment, low-hassle day on the water. Perfect for sailors and paddlers of all skill levels, the Warren Lightcraft is the best of both worlds and an absolute joy to sail.

Models: Warren Lightcraft

Length: 15’6”

Built strictly with racing in mind, the Diam 24 is a light, powerful one-design class trimaran and a notoriously exceptional performer. Boasting blistering speeds of up to 30 knots, Diam trimarans are not intended for beginners. For racers who crave the very best in terms of intense speeds, smooth handling and impeccable performance, the Diam is the red-hot one-design racing tri for you.

Models: Diam 24

Length: 24’

For the sailor who prefers the finer things in life, the Radikal 26 delivers. Perfect for bringing the whole family out for a day on the water, this high performance, trailerable sailing trimaran strikes the most luxurious balance between quicksilver speeds and a smooth, comfortable ride. The Radikal 26 trimaran is as convenient to transport and set up as it is pleasant to sail, with a folding system that minimizes rigging hassle and also makes this a trailerable tri. Built for a fast and comfortable sail rather than a hold-onto-your-seats thrill, one-the-water safety and overall pleasure makes the Radikal 26 what it is.

Models: Radikal 26

Use: Sport cruiser

A solidly-built, single-handed trimaran, the Challenger also doubles as an adaptive design – meaning it is made to accommodate sailors of all levels of physical mobility. Best suited to lakes, the Challenger is a very safe, seaworthy boat for sailors of all ages and experience levels. Add to this the ease of owning, transporting and maintaining the Challenger trimaran and what you get is a simple, fun sailboat perfect both for beginners and those seeking a cheap thrill alike.

Models: Challenger

At a glance comparison:


Astus 16.5, 18.2, 20.2, 22, 24	16’ – 24’	Sport cruiser	Some models
Catri 25	25’	Cruiser/racer	Y
Challenger	-	Day sailor	N
Pulse 600, Sprint 750 MKII, Dash 750 MKII, Cruze 970, Corsair 28, 37, 42	19’8” – 37’	Sport cruisers	Y
Diam 24	24’	Racer	N
Dragonfly 25, 28, 32, 35, 1200	25’ – 39’	Luxury cruiser	Y
F-22, 24, 25, 82, 27, 28, 31, 9A, 9AX, 9R, 32, 33, 33R, 33ST, 36, 39, 41, 44R	23’ – 39’ 4”	Sport cruisers/racers	Y
Mirage Island, Mirage Tandem Island	16’7” – 18’6”	Convertible kayak/trimarans	N
Multi 23	22’	Racer	Y
NEEL 45, 65	44’ – 65’	Luxury cruiser	Y
Radikal 26	26’	Sport cruiser	Y
Sea Pearl	21’	Camper cruiser	Y
SeaCart 26	26’	Racer	Y
SeaRail 19	18’	Day sailor	N
Triak	18’	Convertible kayak/trimaran	N
Warren Lightcraft	15’6”	Convertible kayak/trimaran	N
Weta	14’5”	Racer	N
WR 16, 17, Tango, Rave V	10’11” – 18’3”	Day sailor	N

Did we miss one? Let us know. Tell us what you sail and what you like about each boat in the comments below.

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Tips on Sailing a Small Trimaran

Part 1 adjusting & setting sails + boat trim .

Builders of the W17 will one day appreciate to know how to sail their boat to advantage, so after spending a few seasons putting over 1200 nautical miles on my own W17R, here is what I can share. Even if one might claim I’m biased, I can honestly report that ‘Magic’ is one of the most satisfying boats I’ve ever sailed, providing a blend of performance excitement with dryness & comfort that is rare to find. It’s no secret that I personally enjoy ‘a sense of high efficiency’ in any boat, so here is what I have learned to date about how to achieve that on this boat. I share this broadly as I’m confident much of it can also help owners of other small sailboats to get more out of their chosen craft. Having said that, I’m confident that some passionate duo of 30 year-olds with 20 years of racing behind them will find even faster ways to propel this boat, but when this happens, I just hope they will share their secrets ;-) In the meantime, here’s what I have so far.

To some, much of this exposes nothing surprising but I still think it’s worth spelling out - for those either ‘a little rusty’ or more particularly for those into trimarans for the first time. Keep in mind that what is described here is about ‘ efficient sailing’ - ie: how to get the most out of your boat. Of course, one could ignore such performance gains and just laze around on this very stable boat, simply playing the control lines for safety reasons – but that is not what drives this article. This is about sailing efficiency & performance , requiring a little more attention and effort than just a social sail might inspire.

Before getting into boat trim etc, let’s chat about SAILS ... sail shape to be precise. Novice sailors are too often seen with poorly set sails. ‘Sails’ are your engine and poorly set ones are like running with only half of your cylinders firing. Should you notice that in your car, you’d head straight to a garage, yet when sailing, many seem to just accept the status quo . Let’s try to change that and expand your sailing pleasure.

We must first note that our power comes not only from the wind. Its interactive force is also significantly affected by boat speed and direction so let’s think of it as ‘air movement relative to the boat’ (or for many, the apparent wind ). Take a simple example. Upwind, our boat speed will add to the air speed, whereas downwind it will deduct from it. This will also significantly affect the direction the air actually impinges on the sails. This in turn affects its drive, required sail shape and its ideal trim relative to this moving air. But more on this later.

Although most modern sails have their leading edge attached to either a wire (foresails), furler track (reefable foresails) or to a mast slot (via rope or slides) for the mainsail, sail loads are still principally transferred to the spars and boat by their 3 corners, so the tension adjustment of each is critical for optimum performance. Here are these 3 key attachments (see sketch).

(In the mainsheet photo to the right, note the small net of poly-mesh that catches the W17 traveler control line P&S to prevent it dragging in the water! Simple to make & install, hooked to track brackets & quickly removable).

Sail tension & shape

As a general principle, the stronger the wind, the tighter you need to set most adjusting lines. Primarily, wind travels horizontally over the water so the flow of the moving air requires that we look at the section of our sails in a horizontal plane, but as wind speed is greater at more height above the water surface, we also need to allow for that when trimming our sails. Sails are designed, cut, sewn and set, to give some camber to their horizontal shape …. much like the upper surface of a plane wing. Slower planes need more camber than fast ones … and so it is with sails. So a higher wind (or a faster boat - like many multihulls), needs a sail with less horizontal camber than in a lower wind or for a slower monohull.** This also means that the slower air down by the boat or boom, can accept more sail camber than higher up. This often appears to be ignored by many casual sailors and even some sailmakers, as I too often see sails that are made and set too flat low down for my personal preference. So particularly with full-length battens, a very tight outhaul along the boom is seldom required even for a fast boat, unless the wind is really howling (see next paragraph). However, higher up the sail, wind speed is faster so we need to reduce the camber and with a non-flexible wingmast, this can typically only be done by the sailmaker (using good panel design and stretch-resistant materials), though it can certainly be helped with stiffer, tighter, full length battens. I often add tows of UNI carbon fiber to the after half of full-length battens that are frequently too flexible there and it’s proven to be well worth the effort.

** (This is one important reason that multihulls needs sails made by makers who are experienced with multihulls. Also, as a wing-mast is very stiff fore & aft, the correctly matched mainsail will have an almost straight luff, with only the tack (fwd. low corner) cut back a little, so when the foot is pulled forward, this helps give more fullness, forward and low down).

IF you find your topping lift is always catching in your battens, once the mainsail is up, you can either unclip it at the boom end and temporarily clip it near the mast (ok for small boats), or you can use a light tension cord from the forward boom or gooseneck area and clip it to the topping lift just above the boom to prevent it from flying aft .. but this retainer is best set up without tension that could adversely affect sail shape.

Leech lines (down inside the rear seam) are another thing. Personally, I never tighten mine … but leave them in their sleeve just to add a little ‘body’ to the rear edge Tightening a leech line typically curls the leech to windward, forming a brake or partially stalled sail. Even if the leech is loose and flapping, that’s better than a fixed curl in my opinion. Better to think of the flapping like a sculling oar moving the air aft. Yes, a tensioned leech line will cut the noise, but it will also slow the boat.

To further keep the leech as flat as possible, I favor having multihull sails reinforced with a wide doubler in that area and always buy mine that way. As this also retards leech stretching, adding years of useful life, I find this particularly valuable for a multihull, when almost ALL the sail tension is applied down the leech from the mainsheet. No other part of a multihull main is stressed more.

So shapewise , do all you can to have the leech almost flat and when going upwind, parallel to the centerline of the boat. It may be a little freer to leeward, but never to windward, unless for some bizarre reason, you really DO want to stall the sail and seriously cut your speed.

In order to achieve adequate fullness down low with short-footed foresails , one can benefit significantly in light to medium winds by rigging a mikelin , a line that takes the horizontal sheet tension off the sailcloth at the foot. This will be fully explained in Sailing Tips Part 2 .

Setting Sails

Now hook the Cunningham tackle into the eyelet that needs to be about 200mm above the boom and tension the luff . (If your sail does not have this eyelet, get one added, along with the necessary sailcloth reinforcement).

Except for very light wind sailing, the luff will require to be fairly tight … enough to remove any horizontal wrinkles near the luff rope plus a little more, as the wind will blow-out most small vertical wrinkles. Because of inevitable friction at the masthead sheave, it’s worth initially tightening the Cunningham really hard to get most of the stretch out of the halyard that’s ideally inside the mast. Then, the tension can be eased off a little to suit the weather – still tight in high winds but eased off a little in light weather to allow some horizontal ‘speed wrinkles'. Normally, with ‘a bendy mast’, one might adjust this Cunningham more often to suit conditions, but with a sail set behind a non-flexing wingmast, it has far less effect on the overall result, as the first 200mm of the aerofoil camber near the luff is now created ‘solid’ by the mast itself, so is automatically wrinkle free.

The final mainsail adjustment is with the outhaul . With the fully-battened W17 rig, this primarily adjusts the camber in the lower part of the sail … so needs to be set accordingly. I have found it seldom needs to be tight as the lower part of most sails are already cut rather flat … typically too flat for me. Later in this article, there is a table giving my suggested sail camber for different winds. This gives 8% camber for 25 kts which for most small boats is a STRONG wind. If the foot is 2.4m, this means a camber of 192mm, meaning that the outhaul is correct for that wind when you can push out the lowest batten nearly 200mm from the boom. But at only 5kts of wind or less … a mere zephyr, we are looking for 16% camber, or 390mm (!) of flex in the very lowest batten at the boom. As your apparent (interactive) wind may be higher than this, the camber can be reduced accordingly, but could still be more than we typically see, and I’ll stand by my recommendation until it’s proven to be too much. (Camber will need to be progressively less higher up though, as the chord will be shorter and the wind speed higher).

(Slower boats, be they multihulls or monos, will sail more often with their wind aft of the beam and in such cases, will generally benefit from the addition of a kicking-strap (also called ‘kicker’ or ‘boom-vang’) that pulls the boom down with a tackle between a point on the boom and the base of the mast to keep the mainsail leech straighter, significantly reducing rolling and improving mainsail-drive efficiency when sailing 'off the wind'. Multihulls, especially those with a wide mainsheet track like the W17 have no need of this equipment as they seldom sail with apparent wind aft of the beam, and even if they do, their mainsheet effectively does the job when combined with a wide traveler that’s used correctly).

A word about Booms

It’s been my experience that sails without booms can only be perfectly set and controlled when the clew is close to the deck and led to a point that provides adjustment both fore and aft as well as athwartship. This applies to both main and foresails. As the mainsail typically carries the most sail, a boom is essential for high efficiency in all directions, whereas one commonly accepts to compromise for foresails that are smaller. However, jibs with booms can still give that extra control and even rotating camber-booms (inside large sleeves), have shown better overall performance if you can suffer their inconvenience due to no longer being ‘roller furlable’. Mainsails without booms only work well in a close-hauled tight position and cannot be recommended for overall efficiency. Boomless mainsails put high loads on their battens when eased off, so sails can soon go out-of-shape. Even for small pleasure boats, they allow far too much twist and camber, causing the boat to oscillate dangerously downwind, and to be frank, I am not convinced that a large, multi-sheave-block hanging from a clew that is now free to swing fore-and-aft as well as sideways, is any less dangerous than a boom that can more readily be grabbed to check its passage across the boat. Sorry, but for me, it’s just too much of a compromise on efficiency. Anyway, I also use my boom for other important things, such as a core for rolling up my mainsail and …. well, even for drying clothes or supporting a sun or rain cover while at anchor ;-)

And performance-wise, race classes that allow both boom or boomless rigs, often end up giving the boats different handicaps, as in moderate winds and above, boats with booms have typically proven to be both faster and safer.

Now to the Jib .

If the jib luff is long (say from the mast head), there will always be a certain ‘sag’ from the straight line. Although this is best kept to a minimum (by a stiff mast or backstays), the amount of remaining sag must be recorded and the sailmaker informed, so that this same amount is removed from the jib luff … otherwise the foresail will always be too full. This is generally more apparent with larger foresails such as a genoa.

Typically, the jib tack is lashed to the lower thimble of the forestay on the W17. With time, the sail can change a little – stretching with use, but sometimes even shrinking with age. So this lower attachment may need adjusting after a few seasons use … with the tack lashing effectively becoming a Jib Cunningham. Tensioning the luff of any sail will pull the fullness forward, but when sailing, this fullness will be moved aft by air pressure and friction over the sail surface, so keep a constant eye on your actual sail camber. While the point of maximum camber can be allowed to move to 45% back on a mainsail sailing in moderate to strong wind, it should be more forward on the jib, more like 35%. If it’s too far back, try tensioning the Cunningham. With old tired sails, it will generally mean a visit to the sail loft.

Unless there is a jib boom, the jib ‘ outhaul’ is the actual jib sheet and it’s important that the sheet lead blocks are set at the right location so that tension is initially roughly equal on the leech and the foot. If not, then one can move the jib-sheet blocks or, often easier for a W17, raise or lower the jib by changing the length of the upper wire strop to the mast hound beak and adjusting the lower tack-strop to suit.

The jib sheeting must be adjustable for different conditions, so let’s consider what can be done beyond the basic sheeting adjustment. Some boats have their jib sheet leads on a track that can be moved fore & aft, or even a little inboard or outboard. Moving the lead more forward, will move the tension from the foot to the leech ... allowing more camber for lighter winds. Moving it rearward, will tension the foot but ease the leech, helping to avoid mainsail back-winding or spilling excess wind in heavy conditions.

But the W17 system is simpler and lighter with no tracks required. First, after the leeward sheet is set, the normally idle weather sheet can be slightly tensioned to pull the jib clew closer to the mast for a finer sheeting angle … even down to 10 deg can be useful on some close-winded boats.

(A supplementary line that adds side tension to change the load direction of the primary one is generally called ‘a Barber Hauler ’, so in this case, the weather sheet is being used as a Barber Hauler) .

Also, as the W17 sheet has 2-parts, the standing part can be pulled down under a small hook mounted about 200-250 mm forward of the normally attached position ( see above photo of jib sheet ). This will add tension to the leech without adding as much to the foot … so permitting a little more camber in the sail for lighter winds. Using the ‘telltales’ will help to guide the ideal sheeting … something that will be discussed in Part 3 .

But now, what if the wind is very light … say under 5kts and we are looking for that 16% camber?

We can achieve more camber if we just slacken off the jib sheets completely, but then the leech is also slack and the sheeting angle is so large that there’s no upwind drive or ‘slot-effect’ with the main. So what to do?

This is where a mikelin can really help. There will be more on this in Part 2 , but basically, it is a horizontal line that is added to take the foot tension of the foresail. (See Part 2 for photos & more explanation).

Take note that small boats of all types, particularly those under 6m (20ft), will need to use the movable weight of crew members to constantly modify the heel and trim in order to sail at the highest efficiency.

First and foremost for a trimaran, it’s important to never sail the boat on three hulls! When sailed very light, a few trimarans with high amas (high dihedral for the aka beams) can actually be balanced just on the central hull with the amas clear of the water. This is faster in light wind and my old Buccaneer was like this. However, the high dihedral meant the boat heeled a lot more to find its float stability so losing valuable sail drive, even if offering a boat-rig that spilled wind gusts more automatically. (High dihedral also makes a boat very skittish and ‘flip-flop’ at anchor). Later designed boats generally avoid this, but require that the movable weight (crew) is always conscious of the heel and ready to move from windward to leeward should the wind not be enough to get the windward ama (float) out of the water. At the same time, the crew should be ready to move back to windward if they see a darkening of the water to windward, indicating an imminent wind gust. Ideally, the windward ama should be just above the water surface and if the ama bottom shape is correctly engineered, clipping a few wave tops will be silent and smooth, so of little concern. But if your windward ama annoyingly slaps, you may need to heel your boat more to gain clearance. Although the helmsman might help with this adjustment of heel, the main weight movement should be one of the principal duties of the crew when there is one.

NOTE: The asterisk against the words ‘deep as practical*’ needs clarifying. When sailing in steep waves that are very close (as often found on a large and windy lake) ... the practical limit can be exceeded when wave tops start to come over the foredeck …. so a balance will be required between good bow depth and required forward freeboard. Allow me to also diverse here and get a certain message across. This is a point I like to emphasize, both when sailing and designing.

A boat is required to be supported by upward forces that match its weight. IF going fast enough, some of that can come from dynamic lift , as offered by planing surfaces or foils. However, most of the time, its weight is supported purely by hull buoyancy, so now it’s for the designer AND later, the sailor, to decide just where is the best location for that buoyancy to give the least resistance to forward motion ? If there is little chance for dynamic lift, I have observed that getting more buoyancy up forward will lower forward resistance, especially if added deep below the waterline and not at the surface. So either the designer can work this into his design, or the sailor can move forward to achieve something similar, keeping in mind that every cubic centimeter added forward (where the waterline is narrow) will be a cubic centimeter less to support aft where the boat is generally much wider. If the designer and sailor work together on this, the improved results are significant. But with any design that’s light enough to be heeled and trimmed with manpower, the sailor needs to decide where best to get his buoyancy from, and then adjust crew positions to suit. The gains are measurable.

When sailing upwind, thrust is created by gently deflecting the air over a slightly curved surface of the sail and accelerating the retained air flow off the leech. But it needs to be gently corralled into the sail and held close to it without separation that would cause eddies and drag, so at the entry (luff), the wingmast and sail is pointing almost directly into the apparent wind. From this point, sail curvature will start to perform its magic. Test have shown that, IF the air flow can follow the foil surface, a camber of 1/6 th the chord creates a very effective thrust, but this is too much for higher air speeds as the air breaks away from the surface. 1/10 th or even less camber is then required (see table below),

One way to think about this is to consider that the forward driving force is a product of camber x air speed – but only UP TO the point that the air flow can stay on the sail surface. High air speed will require LESS camber to achieve this. From my own observations, here are some suggested sail camber values as needed to match the apparent wind.

Pressure on sails (lbs/sqft = 0.0012 x C x v 2 ) [v = ft/sec C=1.2 or if in knots, P ~= 0.004 x V 2

Apparent Wind (kts) 5 10 15 20 25 30 35 40

Suggested Sail Camber %: 16 14 12 10 08 06 04 02

or: Chord/Camber Ratio ( C/C ) 6.2 7.1 8.3 10 12.5 16.7 25 50

Pressure (@C = 1.2) lbs/sqft 0.1 0.4 0.9 1.6 2.5 3.6 4.9 6.4

How wind force is applied to the boat will depend in good part on the angle the leech area makes relative to the boat. This in turn will depend on the mainsheet tension and how effectively it is sheeted. As the sail is let out for reaching, a wide mainsheet track can keep the leech area flatter for more effective drive. Without a wide track one can lose some of that, as one will see the boom lift up, allowing the leech to spill air off to leeward instead of driving the boat forward. (Typically, boats with narrower mainsheet sheeting, must add a boom vang to apply the necessary down-force on the boom to keep the leech flat).

Once again, the leech ‘tell-tale’ can add a visual factor to the air flow … see Part 3 .

Sailing Downwind

Typically, multihulls are almost never sailed directly downwind, but on the W17 I’ve observed that with sails winged out to each side, the speed in medium winds is ‘pretty good’, so only by racing identical boats against each other can one really see if it’s still slower than the more generally acknowledged tacking-down-wind with multiple gybes . Meanwhile though, here’s a rough guide.

To tack downwind at an assumed 35 degrees off the straight downwind line on each gybe, you will need to travel approximately 22% faster to cover the extra distance. (Or approx. 42% faster average if at 45 degrees off-wind, and that means making 8.5kts instead of 6). Significant differences ... but sometimes feasible.

Although personally, on my W17 in moderate wind (say 5 to 8 kts), I’ve found it quite efficient to go ‘wing-on-wing’ straight downwind as noted above, in both lighter and heavier winds I found tacking downwind does work best. In the case of very light winds, it helps to create a higher apparent wind to keep you moving (say at 140/220 deg), while in heavier winds, it gives you the ability to steer up and over waves to lower the risk of sticking the bow under, (something that can happen if you go straight downwind at high speed), as well as enable sailing in the fastest water of a wave , something I will discuss more in Part 4 of this series.

============================================================

Continued in Parts 2, 3 & 4 that address :

Part 2: Tacking, Sail Camber, Wing Masts & more

Part 3: Tell-Tales, Airflow and related efficiencies

Part 4: Sailing Downwind and In Waves

"New articles, comments and references will be added periodically as new questions are answered and other info comes in relative to this subject, so you're invited to revisit and participate." —webmaster

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The new "Mini Trimaran" as it is being called (for now) is an evolution of our work in small multihulls over the years. It combines elements of the successful Expedition Sailing Canoe and the " kayak trimaran " named 'Spongebob' into a new vessel. Hull #1 was cut out as a CNC kit in July 2020 and is now in the process of going through sea trials. Click here for Construction Photos of hull #1 You can get a sneak peak of the builders guide here .

Features of hull #1 included a roller furling mainsail and headsail for easy reefing and a boom for superior sail control. For Hull #2 we went back to a non rotating mast with slab reefing and single line reefing instead. The amas retract into the center crossbeams to reduce the overall beam for trailering without having to demount the amas. A stern cockpit with a large kayak style cockpit coaming can be used with a spray skirt. Steering is accomplished with foot pedal controls or a tiller. The boat can also be sailed from the center cockpit and there is optional space to install a hobie mirage drive in the center cockpit. Ample storage for a full expedition load. The center cockpit is flanked by a pair of "wing decks" which are large enough for sleeping aboard with a bivy or cockpit tent. A leeboard is controlled with lines running to the aft cockpit. The hull incorporates an integral spray chine above the water line to increase cockpit comfort while maintaining a narrow waterline beam of 19 1/2"

Length: 18’ 6” Sailing Beam: 11’ Trailering Beam: 6’ 8-3/4” Working Sail: 100 sqft Optional Spinnaker: 80 sqft Empty weight: ~290lbs Gear/water capacity: 150lbs Full Load Displacement: 620lbs (solo) PPI: 117lbs (pounds per 1” immersion Ama buoyancy: 275lbs

Above: Hull #1 freshly painted. April 2021

Latest News: Plans and a CNC kit for this design are coming soon. Hull #1 and 2 are currently in testing and prototyping phases and we look forward to improving the design of the rigging and kit for future builders.

Video from first Sea Trials in Jan. 2021. We were very pleased with the performance and look forward to further testing the rigging and design in preparation for releasing plans and kits for this design. You can note in the video that the boat is being sailed totally empty so the bow rides a bit high.

Hull #1 made the trip to the 2021 B&B Messabout and we had a chance to test here out.

Hull #2 was completed and launched in January 2022. Changes to the design include adding some legroom to the aft cabin, and including space for a hobie mirage drive well in the center cockpit. Hull #2 does not have a roller furling mainsail but instead more traditional slab reefing. A Core Sound 17 mainsail is now the primary working sail and a furling code zero is again used for light air and an off the wind boost.

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Astus 20.5 Sailing Trimaran

A small and simple trimaran that makes sailing simple and fun!

Astus Makes Owning A Small Tri Easy. Here's How:

Cheaper Dockage

The Astus 20.5 has telescopic beams which means that it can easily be collapsed to a narrower width. This makes finding a slip or moorage both easy and affordable. The bottoms of the hulls stay the bottom of the hulls when folded, unlike Corsair's folding design, so you needn't worry about a scum line after being left in the water while folded. Many marinas have shallow, close to shore, slips available at discount as they are hard to rent. The Astus 20.5 can easily be docked at a slip suited for a boat as small as a Potter or Compac!

Safety First

Trimarans are very stable boats making it less likely for crew to trip or fall. The Astus 20.5 is unsinkable with multiple buoyant chambers. The 20.5 is a coastal weekender that is ready to make memories that will last a lifetime without the risk involved with sailing a monohull or catamaran!

Performance Focused

Trimarans are fast. The Astus 20.5 is designed and built to make it fast and responsive. With a centerboard and artisanally designed chines, this boat is designed to be driven hard on any point of sail and canvassed to provide all the power you could need to beat the weather or your fellow club mates.

Easy to Transport

The Astus 20.5 is both lightweight and easy to collapse which makes this boat a dream to transport. You can tow this boat with a Subaru Outback and many other small cars! The lightweight construction of the boat will allow this boat to be pulled by even the lightest weight cars on the road. The amas can be collapsed with 1 person, on the water, in only a few minutes and without any tools!

Easy to Rig

The French are at the bleeding edge of quality and technology in the sailing industry. In addition to this, they are also not known for being the biggest statured people, on average. This means Astus needed to design an easy way to step the mast and with an optional mast stepping rig, you can easily step the mast of this boat (on land or on water) with only 1 person in no time flat!

Fun for the Whole Family

The biggest issue with a small sailboat is...it is small, there's no room for kids to be kids. The Astus 20.5 solves this problem with its nearly 300 square feet of deck area! In addition to the large deck space, there is a small cabin capable of sleeping a family of 4 if needed or for the kids to escape the elements on an overly sunny or rainy day.

Specs	Astus 20.5
Length Overall	19 ft 6 in
Beam Folded	8 ft 2 in
Beam Unfolded	14 ft 9 in
Max Capacity	1250 lbs
Mainsail Sail Area	161 sqft (Leisure) / 183 sqft (Sport)
Jib Sail Area	65 sqft (Leisure) / 75 sqft (Sport)
Gennaker Sail Area	215 sqft (Leisure) / 258 sqft (Sport)
European Safety Rating	C - 5 people / D - 7 People
Displacement	1100 lbs
Draft	10 in (Board Up) / 48 in (Board Down)
Mast Height	26 ft
Max Outboard HP	6 hp

What Are the Members of the Press Saying?

Mers & Bateaux
Bateaux.com
Voilee & Moteur (Boat & Motor)
Boating Business
Boat Industry Magazine

The Astus 20.5, designed by legendary French design firm VPLP, is the most practical small trimaran on the market.

This boat is capable of racing with larger boats, daysailing with the family and even camp sailing (coastal raiding)! The 20.5 is easy to rig, easy to dock; is essentially a beach tri with a cabin!

With enough capacity to carry and comfortably sail with the whole family the Astus 20.5 is the trimaran that checks all of the boxes and at a lower price point than a 22.5!

Shipping is not included in the price of this boat. Estimated shipping to anywhere in the USA is $4000-7000. Call to get your quote today! 410-705-5026

MAKE YOUR BOAT YOUR OWN

The options and accessories below are sure improve and enhance your time on the water!

We are working to add these options to our site. Please be patient. For any questions about Astus, please call 410-705-5026 or email us at [email protected]