Yachting World

  • Digital Edition

Yachting World cover

The foiling phenomenon – how sailing boats got up on foils to go ever-faster

Matthew Sheahan

  • Matthew Sheahan
  • July 20, 2015

The biggest revolution to hit watersports has been foiling, but how did it start and what are the issues involved? Matthew Sheahan investigates

foil moth sailboat

Here’s a challenge. Design a way to support the weight of five saloon cars on a plate the size of your desk on the water. That was the task that faced America’s Cup designers in their bid to make the new breed of foiling America’s Cup boats fly.

If that’s a bit tough, here’s an alternative. Support a 70kg person and their boat in the water on a plank the size of a cricket bat. This one is much easier, the GCSE of hydrodynamics by comparison, with plenty of examples as to how it can be done thanks to the proliferation of foiling Moths around the world.

Getting boats to fly above the water surface is simple in theory, but tricky in practice and has challenged designers for over a century, but in the last decade one class appears to have cracked it.

On the face of it, International Moths on hydrofoils are sailing’s answer to the unicycle. But Moth sailors are far from being trick cyclists, there is a serious side to all this. A foiling Moth will reach 14 knots upwind and 20 knots downwind in just ten knots of wind, and in 20 knots of breeze they’ll be cranking along at 17 knots upwind and 25-30 knots down.

The International Moth has done more than any class to raise the profile of sailing hydrofoils. Photo: Thierry Martinez/Sea&Co

The International Moth has done more than any class to raise the profile of sailing hydrofoils. Photo: Thierry Martinez/Sea&Co

Whether you’ve seen the pictures or experienced the ghost-like whistle followed by the eerie vacuum that trails behind as they come slicing past, it is clear the Moth fleet has done much to publicise the thrill, grace and speed of sailing hydrofoils. The rapid growth of the class has also shown us that foiling is not just for pioneers and record breakers, but that despite several failed attempts in the past to bring it to the masses, this time there just might be a future in foiling.

Another reason why this particular class has exerted so much influence in sailing and spawned a new cycle of design is that Moths can race as a fleet round a course, foiling upwind and down. Although there are plenty of other boats that foil, most have a limited sailing repertoire and need specific conditions to fly. A Moth can fly on all points of sail and is capable of tacking and gybing too.

This has been one of the biggest steps forwards and has helped to boost recent interest from designers and sailors for other potential foiling projects.

Foiling, it’s a drag

At high speed, drag and seakeeping become big issues aboard any vessel, particularly offshore monohulls, and while yacht design has made some big steps forward since the days of hauling half the ocean behind in a pair of breaking quarter waves, there are other issues holding back performance.

Razor-straight wakes ironed flat by beamy after sections are clearly a step forward. Yet the problem for monohulls is that, as they slam and crash their way into the waves, keeping the structure in one piece is a big challenge. Rising above the water’s surface not only reduces drag, but might help to reduce structural risks and make handling at speed easier.

Typical resistance curve showing the rapid reduction in drag once a vessel gets airborne

Typical resistance curve showing the rapid reduction in drag once a vessel gets airborne

Forty years ago it looked as though offshore foiling was about to make a breakthrough. David Keiper took the concept cruising in the 1970s with his trimaran Williwaw (see below), in which he clocked up a staggering 20,000 miles cruising the South Pacific. A decade later, French sailing legend Eric Tabarly broke the schooner Atlantic’s west to east transatlantic record set by Charlie Barr in his foiling trimaran Paul-Ricard.

Yet despite such feats, offshore foiling stalled. Tripping up at speed and keeping the boat in one piece when it touches back down have been the main concerns. And while neither of these two pioneers suffered such a fate, there are plenty of wince-inducing reminders of how it can all go pear-shaped.

But today foiling is more popular than ever. The French tri-foiler and former world record holder L’Hydroptère was the first sailing boat to break through the 50-knot barrier. Since then, a new world record has been set by Paul Larsen’s Sailrocket, another foiler, albeit an extreme one, which owes its success to a recent breakthrough in hydrodynamics.

L'Hydroptère, former speed record holder foiling. Photo: Christophe Launay

L’Hydroptère, former speed record holder. Photo: Christophe Launay

Both share a longer-term view of taking foiling offshore. So does the British foiling cat project C-Fly with its canard configuration.

Meanwhile, the America’s Cup cats are trying to scorch around an inshore racecourse on foils that have no moving control surfaces. It’s a big ask of a high-speed boat and there have been spectacular crashes.

Then there’s SYZ&Co, the 35ft foiling cat on Lake Geneva, the new L’Hydroptère.ch, as well as the hull-less Mirabaud LX. These are just a few of the better known foiling projects, but plenty of others are experimenting with hydrofoils in subtler, more discreet ways – and not just racers and record-breakers.

Foils not just for the few

Cruising catamaran manufacturers Catana launched a 59ft luxury cruising cat that has curved daggerboards that the builders claim produce half a tonne of lift at ten knots. The Dynamic Stability System (DSS), which uses a hydrofoil in the horizontal plane, doesn’t aim to raise the boat out of the water, but instead uses hydrodynamic lift to improve its performance – although the new Quant 23, claimed to be the first foiling keelboat, uses the DSS is a new and thrilling way.

Quant 23, claimed to be the first foiling keelboat

Quant 23, claimed to be the first foiling keelboat

And then there are those who seek to bring the thrills of hydrofoils to the average sailor. In quick succession there have been a couple of 36ft Infiniti multihulls, the Flying Phantom, the Gunboat foiling 40ft G4 and the Formula Whisper foiling catamaran, possibly the first foiler designed for club sailors. There has even been a first Foiling Week in July 2014, where a number of different foiling boats strutted their stuff.

Foiling is in vogue and capturing people’s imagination. But apart from the Moth sensation, why is foiling so popular now and where is this all leading?

Material advances

As is so often the case, the answer lies in the development of new materials and techniques. Weight and strength is at the heart of the issue and carbon has once again played a big part.

While foiling clearly appears to reduce the wave-making drag considerably, there is no free lunch. Lift and drag go hand in hand and what happens beneath the surface can sometimes wipe out any benefit above. For example, tilting a foil at a large angle of attack may create lift, but there will often be a large amount of drag too.

“You don’t fly for the beauty of it,” says aeronautical engineer Joseph Ozanne, Oracle’s lead wing designer for the two previous America’s Cup cycles. “People forget that to generate sufficient lift to raise an entire boat can mean introducing a lot of drag. Just because you’re flying doesn’t mean you’re suddenly more efficient or faster.”

Josephe Ozanne, who worked for Oracle duing the last two America's Cups

Josephe Ozanne, who worked for Oracle duing the last two America’s Cups

To test this, put your hand horizontally outside a car window while it’s going along and rotate it gradually. Initially, with a small angle of attack, your hand will want to rise, but as you twist your palm further, the force pulling it backwards increases significantly.

It’s the same with foils; you can generate lift at high angles of attack, but you won’t necessarily be going any quicker simply because you’ve lifted out of the water.

30kg all up

As a generalisation, less weight means less vertical force is required, which means small angles of attack, which in turn means low drag. From here it’s easy to see how modern materials and the dramatic reduction in the all-up weight of modern boats has helped to make hydrofoils more feasible. Taken to extremes, a modern Moth weighs just 30kg all-up, less than half the weight of its crew.

But the theory doesn’t work for all lightweight, powerful boats; there is a limit.

“Back in 2006 when we were designing Mike Golding’s Gamesa, we looked into the possibility of a fully foiling Open 60,” reveals designer Merfyn Owen. “An Open 60 is a pretty powerful boat and when you compare the sail area:displacement ratio with that of a Moth there appears to be evidence that a foiling 60 could work.

“The trouble is that, unlike a dinghy where the crew generates huge righting moment when compared to the weight of the boat by sitting it out, on an Open 60 the rules on stability prevent you from generating enough righting moment to get the boat fully up on its foils. The Open 60 also has a wide draggy hull compared with a Moth with lots of wetted surface area that holds you back.”

So if an Open 60 would struggle to get up, the prospect for other large foiling monohull keelboats is looking doubtful.

 SYZ&Co cants its daggerboards to vary the amount of side force and vertical lift

SYZ&Co cants its daggerboards to vary the amount of side force and vertical lift

Multihulls, on the other hand, are lighter for the same length and sail area and can generate huge amounts of righting moment without putting on weight, thanks to their wide beam. This makes them better suited to hydrofoils. But there are other problems to overcome and several key configurations to consider.

Foiling configurations

The first issue is how much foil surface area you need to lift the boat. This varies with speed: the faster you go, the less you need. Early foil design used ladder-type racks of foils which lifted out of the water as the boat went faster, reducing the number of immersed foils as the speed increased. But this comes with a big drag penalty at slow speeds.

Surface-piercing configurations, where the foils are angled in a V shape, also find their own natural ride height depending on the speed. As the boat accelerates, the foils generate more lift, raising the boat, which in turn reduces the amount of foil in the water until equilibrium is achieved. The boat finds its own ride height automatically, with no moving parts required.

Print

The configuration works in a similar manner with heel. As the boat heels to one side, more foil is immersed on the leeward side – and less to windward – which helps to right the boat. This inherent stability makes the surface-piercing configuration a popular one – it can be seen on boats like L’Hydroptère . But the problem comes at slow speeds when the high drag of the fully immersed foils hampers performance.

Fully submerged foils, where the lifting part of the arrangement is a horizontal foil mounted under the water at the bottom of a vertical strut, offer the lowest drag, but they have to incorporate an additional element to control the ride height. In other words, the foil has to change its lift characteristics depending on speed.

Print

To do this, the horizontal foil has a moving element on its trailing edge like an aircraft’s elevator. In the case of the Moth, this elevator is connected mechanically to a ride height sensor, a wand that skims across the water’s surface. The lower the boat is travelling above the water, the more the elevator is deployed, creating more lift. But as the boat accelerates the lift increases and it starts to rise. The wand then takes up a different angle from the water’s surface and reduces the deflection of the elevator, reducing the lift.

Apart from the difficulty of following the sea’s surface in big waves, the problem for most sailing boats, especially keelboats, is that this configuration doesn’t provide any athwartships stability. The Moth stays upright because its crew hikes to windward. The same is true for other dinghies and cats that use crew weight for righting moment. On monohulls it’s difficult to make the configuration work.

‘C’, ‘L’ and ‘S’ foils

But not everyone wants to fly. In recent years there has been a great deal of development in foils with complex shapes from ‘C’ shapes, to ‘L’ and ‘S’ shapes and now ‘S’ foils with winglets. Generally speaking, these foils are less concerned with flying and more with the balance between generating sideways lift to drive you upwind and vertical lift to reduce displacement. Much of this development work took place in the former ORMA 60 multihulls.

“By canting the leeward daggerboard you can change the balance between lateral and vertical lift,” explains Vincent Lauriot-Prévost of designers VPLP, experts in high-performance multihulls and some of the world’s more extreme designs such as USA-17 and L’Hydroptère.

“When you’re sailing upwind, side force from the daggerboard is very important, as it is in any boat, but as you sail freer and faster you need less foil to create the required side force. Normally you would lift the board to reduce the drag, but if you leave it down and then cant it in towards the centreline, you create some vertical lift which then helps to reduce the displacement of the boat.

“Another way to achieve a similar effect is to have a curved daggerboard. A simple ‘C’ shape provides more vertical lift the further it is pushed down. The next stage of development was then to try ‘S’ shaped boards which, again, vary the distribution of lift and side force depending on where the boards are set.”

Speed record graph

Although more expensive to build than straight boards, curved daggerboards have the advantage that they do not need complex canting mechanisms. Some classes and rules ban the latter so this is an alternative approach.

“Our ORMA 60 design Gitana II, which won the Route du Rhum in 2006, would see a reduction in displacement of 40 per cent at 20 knots,” says Lauriot Prévost. “At 26-28 knots the displacement would reduce to 70-75 per cent for a boat that weighs 6.5 tonnes fully loaded.”

This puts the issue of displacement reduction into perspective for cruising boats. Half a tonne of lift at ten knots from a curved daggerboard might sound a lot, but when the boat displaces 22 tonnes loaded, the displacement reduction is just over two per cent. While this may still have a beneficial effect on performance, it becomes easier to see that the future for cruising hydrofoils is not so clear cut.

Screen shot 2015-07-22 at 10.03.16

Changes to trim, stability and displacement through subtle alterations in the alignment of foils is also a growing trend in the Open 60s and now the Volvo 65. Angling the keel pin up at its forward end by a few degrees provides a positive angle of attack on the keel fin when canted out to windward. When swung out to one side, the fin acts like an aircraft’s wing and helps to support the boat, although the lift also tends to reduce the effective righting moment.

Nevertheless, according to at least one top designer, the effort is worth it. He says: “There are some other performance details involved with this that I can’t speak about!”

Foils of the future

Where is the current craving for foils taking us? One of the biggest foiling experiments at present is in the America’s Cup. With their notoriously big budgets, Cup campaigns are well-known to accelerate the development of ideas that can eventually trickle down. What kind of technology breakthrough will wingmasted cats on foils provide?

The answer is not a simple one as the AC72s used in the 2013 Cup were never originally intended to foil. A loophole in the rule, exploited by the New Zealand team and deemed legal by the jury, sent teams off exploring the possibilities, but with little scope to control the foils themselves as no moving parts are allowed.

In the 2013 America's Cup, the Kiwis exploited a loophole in the rule to get their catamaran foiling

In the 2013 America’s Cup, the Kiwis exploited a loophole in the rule to put their catamaran on foils

“The Kiwis look good on foils, they are stable in pitch and heave and their foils appear to be reliable. But this will all come at a cost: drag,” said Oracle’s Joseph Ozanne at the time. “Less pitch stability, as our boats had, can reduce drag, but it makes the boat very tricky to sail. We did a lot of wheelies when we were learning to sail our boat. Regulating flight height is a nightmare.

“Modern aircraft are designed to be more unstable to improve manoeuvrability and also to reduce drag, but they have systems that keep them under control. We are not allowed these systems, so it’s the crew that have the control. So the key foiling lessons from the Cup could be learning about foil shapes and how to handle instability.”

For Sailrocket II’s foil designer Chris Hornzee-Jones, another aeronautical engineer, hydrofoiling means speed. Having set a new world record at 64.54 knots and broken into new territory, Hornzee-Jones believes this is just the beginning.

Chris Hornzee-Jones, Sailrocket's foil designer

Chris Hornzee-Jones, Sailrocket’s foil designer

“I’m convinced we can get to 70-75 knots with subtle developments to this foil,” he declares. “Beyond that it becomes progressively harder, but the fact that powered craft on foils have achieved 80-100 knots confirms that there are foil shapes that will work at this speed. I think it may be difficult to get a single foil to perform over the entire speed range. We already use two on Sailrocket. Nevertheless, I do see over 80 knots as possible.”

The lessons learnt in this new speed territory could also have implications at far slower speeds and for much less extreme boats.

“Thick foils like the one we developed are good structurally,” says Hornzee-Jones. “Creating a foil that ventilates at low speeds means that at, say, 20 knots you are already into low drag.”

Like a gearbox and engine combination that allows you to engage top gear at 20mph and accelerate though to 100mph without changing gear, versatile, vice-less foils could indeed transform the behaviour of our boats in the future. Add to that the possibility of active control using sophisticated, compact and efficient electronics and new possibilities emerge.

Opening our minds

Although the average cruising monohull may not want to get up and flying, efficient low-drag stabiliser foils, for example, controlled by a tiny chip, could make the notoriously rolly tradewind conditions on a transatlantic a more comfortable and efficient affair.

Vincent Lauriot-Prévost

Vincent Lauriot-Prévost

“Foiling Moths have opened people’s minds,” says Vincent Lauriot-Prévost. “The future will depend on having good control of efficient foils. We will need to change camber profiles effectively and develop automatic trim regulation. But, we must also think weight, otherwise the systems won’t work.”

Perhaps it is no surprise that after more than 70 years of sailing development at the leading edge of the sport, many are still scratching their heads at how to make such a promising concept work for the rest of us.

If you enjoyed this….

Yachting World is the world’s leading magazine for bluewater cruisers and offshore sailors. Every month we have inspirational adventures and practical features to help you realise your sailing dreams. Build your knowledge with a subscription delivered to your door. See our latest offers and save at least 30% off the cover price.

Damic Design

Swift Hydrofoils

Damic Design specialises in design and manufacturing of Moths and Hydrofoils for the International Moth Class. While Moth sailing is our passion, our main objective is to offer the fastest, most developed and best built boats and foils on the market.

Our involvement in the class started in 2004, exposing us to the world of Moth hydrofoiling technology since the early days. The initial period was quite experimental, but also fun and educational as it allowed us to learn and develop our design ideas. We made a lot of foils in this phase with the most successful being the Macita that won the 2013 World Championship. While this foil is not on offer anymore, it certainly paved the way for the foils we make today.

In particular, the Swift range which consists of a number of sizes, each with different lift and control characteristics designed to ensure optimal performance over a wide range of sailing conditions. This range has now grown to include: Two rudders hydrofoils (Small and Medium), three mainfoils (Super Small, Small and Large) and our super thin HM carbon verticals.

The Swift Hydrofoil range is a refined product line with the foils now in their 3rd generation of improvements. We are constantly looking to make gains that we first test, and then bring into production.

What this means for you is that every product in the range is on trend and offers performance improvements for your boat without the need to upgrade the entire platform. While this range is sold with our Swift Moths, it is also available to Bieker, Exocet and Mach 2 owners that are looking for a fast upgrade option. Our foils placed 7 out of the top 10 at Perth Worlds, won 2023 NSW and Australian Nationals and also got 2nd in the Waymouth Pre-Worlds regatta. Furthermore, all Damic Design foils are made in Australia and are constructed from solid carbon fibre, from market leading supplier, Toray. While this increases production costs we believe it is warranted as it insures superior quality and perfomance on what we consider as the most important part of the boat. We are also proud to be the only foil manufacturer that is solely focused on foil development and directly involved in design, testing and manufacturing of all of our products. That means that every foil that leaves our workshop has been hand finished by the designer and Moth sailor that truly understands the product and what is required to make it go fast!

Swift Mainfoils

foil moth sailboat

Swift Super Small (v2)

Our latest hydrofoil, specifically designed for light sailors or as a strong wind foil. It features an innovative tip and bulb design that are optimised for reducing drag when going fast.

$3,350 AUD + GST

foil moth sailboat

Swift Small (v3)

The ultimate all round medium wind foil, that has been winning regattas since the initial release. It is known for having great control features with a very wide performance window.

foil moth sailboat

Swift Large (v2)

Excellent high lift foil that can be carried up range thanks to its thin section and very efficient profile. This foil is a proven race winner and a must for heavy sailors or light wind venues.

Swift Rudderfoils

foil moth sailboat

Swift Small Rudder (v1)

The Small rudder is based on the same theory as our Medium. It is a high aspect low drag shape designed to minimise drag and maximise lift offering great glide though ability for ease of foil tacking. Unlike other small rudders, ours still makes foil tacking a breeze while being tiny in size and super fast.

$2,200 AUD + GST

foil moth sailboat

Swift Medium Rudder (v3)

Our Medium rudder is a well proven design that is a result of many years of development. Its short cord makes it very low drag however it generates plenty of lift thanks to its high aspect ratio. This foil will help make your foiling tacks easy and repeatable. $2,200 AUD + GST

Swift Verticals

foil moth sailboat

Swift HM Rudder Vertical (v3)

The v3 is our latest design to date. It further improves on the original v1/v2 designs with changes in the bottom 1/4 of the section. It is designed to be on the absolute limit of the materials to insure the ultimate performance from reduction in drag coefficient. It also includes a number of design features that combat the “all too common” rudder wash out problems. Made from pre/preg solid High Modulus carbon fibre construction, it is thermally stable and ultra stiff.

$4,100 AUD + GST

foil moth sailboat

Swift HM Main Vertical (v1)

This is the thinnest main vertical on the market which offers significant reduction in drag by simply being smaller to reducing skin friction and displacement. Made from solid High Modulus carbon fibre construction, it is thermally stable and ultra stiff. Includes pushrod and bellcrank kit.

$4,500 AUD + GST

foil moth sailboat

AOA Templates

These angle of attack measuring templates, are designed to fit our range of Swift main and rudder hydrofoils. With the help of this device, you will be able to determine the all important foil angle relative to waterline. $45 AUD + GST

foil moth sailboat

Swift Vertical Covers

Tailor made to suit Swift HM Main verticals and HM Rudder Verticals. These premium quality covers are Australian made using quality Dimension Polyant sailcloth. They features marine canvas outer skin and felt lining inside. $120 AUD + GST

foil moth sailboat

Swift Horizontal Covers

Suitable for Swift Super Small, Small and Large horizontal hydrofoils. These premium quality covers are Australian made using quality Dimension Polyant sailcloth. They features marine canvas outer skin, felt lining inside and Velcro closure to protect the trailing edges. $110 AUD + GST

Foiling Moth

The MIT Sailing Pavilion has a Foiling Moth that uses wing-like foils to lift the hull out of the water. This 11 foot, 65 pound dinghy "flies" above the water is only sailed by the most advanced sailors. Learning to sail the moth means spending a lot of time swimming since the boat does not stay upright in the water on its own. The boat is very fragile if used improperly and may result in injury if the sailor is not alert.

  • 1 Requirements to Sail
  • 2 Safety For You (& The Boat)
  • 3 Rigging the Foiling Moth
  • 4 Derigging Notes
  • 5 Sailing Basics
  • 6 Tuning Basics

Requirements to Sail

  • Must have full membership (Normal Sailing Card)
  • Must have Helmsman rating
  • Must have permission from Sailing Master Fran Charles or Varsity Sailing Coach Matt Lindblad
  • Buddy system: Must sail with moth-qualified buddy that is also motorboat capable
  • Recommendation - on breezier days, 3 people buddy systems are more ideal
  • May choose to sail moth without chase boat

Safety For You (& The Boat)

  • Don’t hang on to the tiller extension if you lose control or crash - it snaps over the wing easily.
  • Do hold on the main sheet in a crash, if reasonable - the boat can easily sail 100 feet on its own (sometimes still foiling).
  • Think of an exit strategy for any potential crash (especially if it’s windy). Try to get yourself clear of the boat so that you don’t hurt yourself or the boat.
  • Don’t step on the hull, except the chine (corner).
  • Do step on the centerboard (right next to the hull) to right the boat after a capsize - it’s much stronger than the hull.
  • Watch out for the trailing (back edges) of the foils, and the ends - they are sharp.
  • Watch out for the wand if swimming around the bow - it’s difficult to see in the water, pretty long, and very fragile.
  • Watch out for falling off the wing through the sail (it has torn before), try to let yourself down carefully.
  • Be extra mindful of traffic - that can be the scariest part when you’re first getting up. Purposefully crashing to windward and using your body to slow down can be an effective stopping method sometimes.
  • Be extra mindful of being smooth with the tiller, especially as you move your body around the boat. Since the boat goes so fast and the rudder is long, the rudder cassette and pin get very loaded up when there are erratic rudder movements. These sort of movements also can make you crash…

Rigging the Foiling Moth

Rough sequence:

  • Make sure the line going across the back from wingbar to wingbar is very tight. This keeps load off of the wingbar joints.
  • Check that the battens are snug (use a metric allen key from shop to adjust tensioners)
  • put together mast, slide into luff pocket, put on cambers
  • KA Sail Rigging Video
  • Make sure the shrouds and forestay are properly seated in the ends of the “star” spreaders. Also make sure the shaft collars are set so that the star is roughly horizontal and symmetric port/stbd.
  • pull up rig, place onto mast step, then tighten forestay pretty tight and tie off
  • attach cunningham
  • rig up boom (attach gooseneck first, make sure outhaul not tangled with downhaul)
  • make sure vang all the way loose, attach clew of sail to boom and then attach outhaul
  • can either get someone to help lift, or flip boat over with trolley and then carefully lift trolley off
  • Double check the pin and ring for the main foil, and make sure the bolt on the barrel adjuster is not bent. Side note -- DO NOT STEP ON THE BARREL ADJUSTER.
  • Make sure the tiller is lead through the bungee. This keeps the tiller centered if you let go, and also makes it harder to move the tiller too erratically.
  • The holes should be reopened to let the pressure equalize once the boat has been in the water for a few minutes. This can easily be done on the dock or while the boat is capsized to port.
  • A good rule of thumb for setting up the main foil ride height is that the horizontal flap should have a slight negative angle of attack when the wand is fully extended. This is ~5-7mm of pushrod showing
  • Slide then tip the boat into the water, being careful of the wand and linkages. Try to lift the boat when tipping it upright instead of rotating it about the wingbar on the dock.

Derigging Notes

  • The pin that holds the star spreader to the mast stays with the spreader because we have two different masts.
  • The rudder pin stays in the rudder to prevent the rotating white plastic piece from spinning.
  • Make sure you remove the tape from the breather holes.
  • If you need to drain, derig first, then flip it upside down and lift the bow up so it drains out the back. Every once in a while put the bow back down to let air in
  • http://www.mach2boats.com/the-mach2/service-and-maintenance
  • The Mach 2 has small drain holes in each bulkhead. These little holes allow water to flow through the boat so it can be emptied via the bung holes in each tank. This image should make it easier for Mach 2 sailors to empty any water that may get into the boat. Note: The red circles are the drain holes

Sailing Basics

  • Stay on your feet! When not up foiling and hiking, try keeping your feet underneath you; half crouching/sitting is good as you’ll have to adjust your weight a lot as you get the balance of the boat at low speed.
  • To get foiling, sail on a reach. A pretty tight reach is usually best but once there is a lot of breeze there is a wide range of angles that will work. Give the main a nice ease, and once the boat starts to heel to windward, bear off a bit and let the boat power up. Once it starts to pop up onto the foils and accelerate, you will need to trim in the mainsheet a good amount because the apparent wind starts to move forward.
  • Keep the rig on top of you! Like a windsurfer. Always have windward heel - if you get too flat, or heeled to leeward, ease the main until the boat comes back on top of you. Hiking helps too, but the rig can generate a lot of power so the mainsheet is most important.
  • Upwind: pinch to depower, foot to power up.
  • Downwind: sail to a run to depower, up to a reach to power up.
  • Be active in the straps! It can be necessary to move in through a lull or if you stall the sail.
  • Sit forward! Further than you might think - just behind where the wing starts to curve (just behind the control lines on the trampoline).
  • The moth class has made some basic tutorials with Nathan Outteridge https://www.youtube.com/playlist?list=PLCFOdEqGeu5CYFzz51JhpQ4ubz6qHiQs7

Tuning Basics

  • Vang is good - it is especially hard to see from on the boat, so use it. And then use more. And probably even more.
  • Keep a moderate amount of cunningham on at all times so that the camber inducers in the sail remain on the mast. This is maybe a bit more than finger tight?
  • If the cambers do come off while sailing, you can sail a little bit if needed but it’s best to fix it ASAP so that the sail doesn’t get damaged. This can be done back at the dock or with help from the motorboat, or swimming with the boat capsized with a bit more effort.
  • Outhaul - loose until it gets breezy.
  • The Mach2 likes to sail a little “bow-down” (partially due to hydrodynamics with the fixed part of the main horizontal, partially due to aero drag on the wings). With our foil setup this usually means the first indication you are riding too high is ventilation on the rudder horizontal. Upwind this is on the leeward tip since you are heeling far to windward, and downwind the first warnings are often just some funny noises or occasional brief loss of steering.
  • Approx 2 rotations of the barrel adjuster is a rough range, but you should play around with it so that the boat is about the same height on each tack (look down at the marks on the daggerboard vertical)
  • Usually the stbd side (lower) adjustment is about right for going downwind
  • If boat kind of pops up quickly and then stalls (often in marginal foiling breeze), this most likely means there isn’t enough rudder lift. Twist the rudder so the bolt moves forward in the slot.
  • Occasionally check that the ride height adjuster is wound correctly and not tangled

Navigation menu

Personal tools.

  • View source
  • View history
  • Sailing Team
  • Lynx 16' Catboat
  • Learn-to-Sail
  • Windsurfing
  • Recent Changes
  • What links here
  • Related changes
  • Special pages
  • Printable version
  • Permanent link
  • Page information
  • This page was last modified on 8 July 2016, at 11:45.
  • This page has been accessed 40,365 times.
  • Privacy policy
  • About MITNA
  • Disclaimers

Bieker Boats

  • Naval Architecture & Engineering
  • Detail Design & Production Support

Bieker Boats

PERFORMANCE MARINE CRAFT

  • Bieker Moth

The hull is a comparatively high volume displacement shape, with a rocker profile for easy low ride handling and un-sticky takeoff characteristics.

The platform concept minimises aerodynamic drag and heeling moment, with minimal tramp area. Stiff single piece wing beams located in rebated deck sockets maximise effective beam when heeled to windward through a curved, high angled shape.

The boat has been designed with a deck-sweeping rig in mind. Building on recent trends in the class, the layout allows for a long deck/sail seal. A concealed control system and control line configuration makes for a clean deck layout. For backward compatibility the boat has also been designed to use a conventional full-height rig.

The foils have been engineered to be as stiff and long as modern materials and production processes allow. The boat can fly higher out of the water, and has a larger vertical range to deal with both deceleration during foiling tacks and larger waves downwind. With 3D printed titanium components, the foil section thicknesses have been reduced for minimum drag at sailing altitude. Our horizontals are aggressively high aspect with low wetted area.

The Bieker Moth is built in New Zealand by Mackay Boats.

foil moth sailboat

  • Moth Records
  • Rules and Documents
  • Meetings and Reports
  • Netherlands
  • New Zealand
  • Switzerland
  • United Arab Emirates

About the Boat

The international Moth Class is the fastest one Person Dinghy in the World.

IMCA – Committee

Shaun ritson / chief measurer, graeme southerland and franco greggi / executive committee.

Sponsored by

The Worldwide Leader in Sailmaking

  • Sail Care & Repair
  • Sailing Gear
  • Sail Finder
  • Custom Sails
  • One Design Sails
  • Flying Sails
  • New Sail Quote
  • 3Di Technology
  • Helix Technology
  • Sail Design
  • NPL RENEW Sustainable Sailcloth
  • Sailcloth & Material Guide
  • Polo Shirts
  • Sweaters & Cardigans
  • Sweatshirts & Hoodies
  • Accessories
  • Mid & Baselayers
  • Deckwear & Footwear
  • Luggage & Accessories
  • Spring Summer '24
  • Sailor Jackets
  • Maserati X North Sails
  • NS x Slowear
  • Sailor Jacket
  • Sustainability
  • North Sails Blog
  • Sail Like A Girl
  • Icon Sailor Jacket
  • Our Locations
  • North SUP Boards
  • North Foils
  • North Kiteboarding
  • North Windsurfing

SAIL FINDER

SAILING GEAR

COLLECTIONS & COLLAB

COLLECTIONS

WE ARE NORTH SAILS

ACTION SPORTS

Popular Search Terms

Collections

Sorry, no results for ""

How to Rig a Foiling Moth

How to rig a foiling moth in 20 steps, dan neri gets ready to sail this singlehanded foiler.

foil moth sailboat

When I first set up my Moth, I broke a lot of stuff. Since then I’ve learned what to do (and what not to do) and in what order. First, bring everything to the beach. Set the foils off to the side, safely out of the way of the boat and any spectators.

Rig sail and spreaders

foil moth sailboat

Step the mast

Note: My boat has an adjustable headstay, so I can step the mast with the headstay adjustment at its loosest setting. If you have a fixed headstay, you’ll need to use a longer temporary headstay.

foil moth sailboat

Install blades

capsize moth on beach

Final adjustments

foil moth sailboat

20. Go find your hat if you are bald, and your cheapest sunglasses. Take off the foil covers. Ready to go sailing!

Read Moth Newbie: Dan Neri Learns to Foil

FEATURED STORIES

How to care for your foul weather gear, npl renew faq, flying sails 101.

  • Refresh page

facebook

  • CLASSIFIEDS
  • NEWSLETTERS
  • SUBMIT NEWS

Pantaenius 2022 - SAIL & POWER 2 MPU AUS

How to home-build a Moth - James Sainsbury's step-by-step guide!

foil moth sailboat

Related Articles

foil moth sailboat

  • AROUND THE SAILING WORLD
  • BOAT OF THE YEAR
  • Email Newsletters
  • Best Marine Electronics & Technology
  • America’s Cup
  • St. Petersburg
  • Caribbean Championship
  • Boating Safety

Sailing World logo

Bladerider Moth Sailboat

  • By Alan Block
  • Updated: August 21, 2007

foil moth sailboat

Even the staunchest keelboat devotee can’t help but be intrigued by them. They don’t have a trapeze, and they’ve only got one little sail, yet they sail at twice the true wind speed. They’re monohulls, but they move faster than a Tornado cat, sailing upwind as fast as 13 knots, downwind close to 30 knots. Jumping out of the water on ultra-light carbon foils in a 5-knot breeze, they’ll smoke almost anything else powered by sails.

They’re International Moths, and if Andrew “Amac” McDougall of Bladerider International has his way, they just may change the world of singlehanded dinghy sailing forever.

Ironically, the Moth class that has spawned the most groundbreaking development in hydrofoil technology is one of the ancient ones. Len Morris built his 11-foot Olive near Melbourne, Australia, in 1928. A year later, Joel Van Sant built a Moth in Elizabeth, New Jersey, to almost the same proportions. In both locations the small catboats were a hit, and numbers grew steadily due to the low cost of building such small, simple dinghies.

The class spread from the U.S. to Europe and from Australia to New Zealand, with huge design variations from fleet to fleet. Various national classes modified their rules slightly to encourage international competition, and with the International Yacht Racing Union’s acceptance of the class in 1972, the International Moth Class was born. The openness of the Class Rule, the first sentence of which reads, “the intention of these class rules is to give the designer and builder the fullest liberty in design and construction,” has resulted in much innovation and a variety of designs, including skiff Moths, pram Moths, scow Moths, skinny tube Moths, dinghy Moths, and now foiling Moths (which can be skiff Moths or scow Moths).

In 1999, Australian Dr. Ian Ward opened a can of worms that would change the class more profoundly than any prior development. Ward fitted horizontal hydrofoils to the bottom of the centerboard and rudder of a Moth and he found that the foils lifted the boat out of the water with ease. Catamaran and trimarans had already proven that three T-shaped foils worked, but conventional wisdom held that a dinghy with two foils would be far too unstable to be sailable. Ward quickly found out that the conventional wisdom was wrong, but devising a system to maintain ride height and control would take more time. Brothers John and Garth Ilett created and refined such a system in 2000 using a surface-sending wand to control the main foil’s lift.

Amidst intense intra-class squabbling, Rohan Veal used the Iletts’ creation to win the 2004 Moth World Championship with eight firsts in eight races. In one race, he beat the second place boat by ten minutes. With non-foiling, or “low riding,” Moths quickly approaching obsolescence, the biggest obstacle to competitive Moth sailors became obtaining their own foiling moths. The Iletts’ Fastacraft and a handful of other small, custom boatbuilders just couldn’t keep up with demand for their carefully constructed, all-carbon dinghies. That’s where McDougall came in.

A longtime Moth sailor, McDougall built his first Moth more than three decades ago. In early 2005, he purchases one of the Iletts’ foiling Moths and immediately knew that it was something special, a sailing experience that shouldn’t be constrained by the limited resources of a few custom builders. McDougall scraped up the money for his own Moth design/build business and set to work improving and simplifying existing designs and components to allow faster fabrication and shorter build times. He spent four months on the design of the foils, performing flow analysis and even writing his own foil-creating software. Once he completed the basic boat design, McDougall recruited Veal to help develop and market the boats, signed a partnership with composite specialist McConaghy Boats, and Bladerider International was born.

There are a handful of foiling Moths in the U.S., but the first two production Bladeriders landed here in April via air freight in boxes weighing about 100 pounds. Detroit sailor Bora Gulari bought the second U.S. boat, and in June he took me out for three days of “flight school.” I came late to sailing and started in big keelboats, so I lack the balance and quick reaction time with which lifelong dinghy sailors are blessed. I weigh around 220 pounds, a third bigger than most competitive Mothies, so in a way, I’m the ideal person to test the Bladerider. McDougall’s vision is not to create one more International Moth, it’s to bring the foiling experience beyond the aerospace engineers and tinkerer/athletes to the average sailor–someone just like me. Twenty minutes on the Bladerider taught me that I’ll never win a Moth World Championship, but I experienced a sensation totally new to me, something that could revolutionize the small boat world.

On the first day, moderate winds on a flat Lake St. Clair provided plenty of power, as Gulari proved less than 20 yards from the entrance to Bayview YC when he launched onto the foils and accelerated to 12 knots, upwind. When he turned down to a reach, our Sea Ray could hardly keep up. After a few minutes, I jumped into the water to take my turn. The first thing that struck me was the boom, in the head. The next was the incredible narrowness of the tiny hull. Dwarfed by large, trampoline-covered carbon wings, the 12-inch wide hull resembles a slab-sided torpedo. The designer realized that the hull would spend most of its time in the air, so he downsized it accordingly. The hull is covered with the most aggressive non-skid I’ve ever encountered, and as tippy as the boat is, that’s a good thing. The racks are works of art: clear-coated carbon sculptures covered with Dacron tramps, their width provides massive righting moment to counter the power from the big, windsurfer-inspired sail that sleeves over a thin-walled carbon mast.

Once I got moving, the instability vanished, even before I lifted free of the water. The foils generate substantial lift and stability at slow speeds, giving the pencil-thin hull the feel of a wide boat. Simple sail controls allowed me to concentrate on placing my body where Gulari told me, although the oversized mainsheet made easing the sail a bit stickier than it should have been. It’s a physical boat that requires lots of balance, and the small loads and efficient controls should be attractive to female and youth sailors.

A puff hit, and I practiced the dinghy mantra, “ease, hike, trim.” Hiking on the wing, I trimmed the sail and lifted almost imperceptibly out of the water. Another puff lifted me completely clear, and things went strangely silent. As a Melges 24 sailor, I’m used to going fast, but that speed is always accompanied by spray, vibration, and the sounds of crashing through waves. Speed on a Moth is completely different–drama free, peaceful, almost trance-inducing. Reality broke into my reverie when I let the boat heel too far to leeward. The boat crashed back into the water, and I hit the shrouds.

For days afterwards, my bruises would remind me of just how fast I’d been going.My test sail was like nothing I’d ever experienced on the water. In twenty minutes, the Bladerider opened my eyes to the possibilities of foilborne sailing. Foils have already invigorated the International Moth Class, with membership growth at a ten-year high, but it’s not just the IMCA that Bladerider is trying to revolutionize. McDougall’s operation currently builds three to four boats per week, but to goal is to double that output.

Priced at $14,000, the Bladerider isn’t cheap, but it provides an utterly new experience. Gliding above the water at double digit speeds, the only sound a faint hiss from the foils, you’ll be transformed. Going back to your loud, sloppy, slow, surface-bound craft might just be unthinkable.

For more about the Bladerider Moth, go to www.bladerider.com.au/

  • More: foiling , McConaghy , moth , Sailboats
  • More Sailboats

ClubSwan 28 rendering

Nautor Swan Has A New Pocket Rocket

Pogo RC Visuel

Pogo Launches its Latest Coastal Rocket

The Storm 18

A Deeper Dive Into the Storm 18

foil moth sailboat

2024 Boat of the Year Best Recreational Racer: Z24

Cole Brauer wins second place in the Global Sailing Challenge

Brauer Sails into Hearts, Minds and History

The J/V66 "Numbers"

Anticipation and Temptation

Christina and Justin Wolfe

America’s Offshore Couple

2023 Jobson Junior All-Stars

Jobson All-Star Juniors 2024: The Fast Generation

Sailing World logo

  • Digital Edition
  • Customer Service
  • Privacy Policy
  • Cruising World
  • Sailing World
  • Salt Water Sportsman
  • Sport Fishing
  • Wakeboarding

Classic Moth Boat Association

  • Constitution & By-Laws
  • Measurement Rules
  • Vintage Measurement Rules
  • Racing Divisions
  • General Racing Tips
  • S Curb Jibe
  • Improve Your Starts
  • Sailing Glossary
  • Racing Rules
  • This is How I Do It
  • Roll Tank Deck System
  • Dorr Willey Project
  • Charles & Paul Doing It Right
  • Little Mae Too Plans 1943
  • Louis Pillon Plans
  • Cole Super-Moth Plans
  • Some Building Tips
  • Some Material Sources
  • Europe to Europa
  • Wax On or Off
  • Sail Cleaning Tips
  • Dotan Rudder
  • Simple Knots

foil moth sailboat

Rudder Blades & Centerboards

How to build rudder blades & centerboards - by j.r. watson.

When the centerboard of my Searunner trimaran broke in the middle of a windy race around the Black Hole, the question I kept asking was "why now, after working fine all of this time, and when we were leading the race?"

"Guess it just wore out" was my excuse to myself. This centerboard was built of laminated layers of plywood, resulting in a thickness of 2". It was then covered with two lavers of 6-oz woven fiberglass fabric. It was a deep and wide board with a lot of area, and like any rudder or centerboard on a boat that is sailed hard, it was exposed to a fair amount of stress.

The answer to "why now - while leading the race?" could have been fate. But there is a more scientific answer. Extensive laboratory testing at Gougeon Brothers, Inc. defines why the centerboard failed. Understanding why can help us design and construct components that will perform more efficiently and last much longer.

The plywood centerboard did, in fact, wear out - or more accurately - it failed from rolling shear fatigue. Fatigue cracks in a material result from repeated (cyclic) stress. Fatigue is a reality of all structures and materials, and eventually culminates in structural failure. Repeated loading and unloading or even worse, loading one way and then the ' other(reverse axial), rapidly reduces a material's physical integrity and accelerates degradation. The higher the load is as a percentage of the material's ultimate strength, the more rapid is the deterioration.

Some materials have a greater fatigue life than others. Ounce per ounce, wood is capable of operating at a much higher percentage of its ultimate stress level than most other materials. That is why such wonderfully efficient structures can be built with wood. However, plywood is not a good choice for cantilevered structures such as rudder blades and centerboards. This is because plywood is susceptible to rolling shear, shearing forces that roll the structural fibers across the grain.. Plywood's unidirectional wood fibers are laid in alternating layers, approximately half of them are oriented 90 degrees to the axis of the loads. Like a bundle of soda straws, which resist bending moments quite well one way, they simply lack cross-grain strength laterally and can roll against one another and fail under relatively low stress, especially in a cyclic environment. Therefore, when anticipated loads are primarily unidirectional, it is ideal to use a material with good unidirectional strength. Since only half of plywood's wood fiber is used to advantage, a plywood rudder blade or centerboard going from tack to tack (reverse axial loads) will fatigue much more rapidly than one built as described in this article.

If you were to look at the end of the board, say a fish's view of a centerboard or rudder blade, you'd view its cross section. A section that has a faired airfoil shape is preferred over one that is flat with parallel sides. This is because the airfoil shape produces lift when moving through the water, thereby counteracting the sideward forces exerted by the sail rig. A flat section produces less lift and at a great expense of drag, slowing the boat and making it more difficult to steer.

Selection of a proper camber and section can be a subject of great theoretical debate. One can become intimidated with technical terms such as thickness distribution, Reynolds number, boundary layer, and so on. These terms do relate to the subject, however, for the builder/ sailor whose boat floats forlornly in need of rudder blade the following will do just fine. In fact, the best designers and builders will be hard-pressed to do better. An excellent choice for most craft, is a realistically accurate and fair NACA (National Advisory Committee for Aeronautics) 0012 airfoil, where maximum board thickness is 12% of the fore/aft length (chord length). Maximum thickness is located about 30% of the chord length measured from the leading edge (see sketch). The dimensions used to establish a specific shape (called offsets) are given in the appendix of The Theory of Wing Sections*. See the foil-owing article, How to loft Airfoil Sections. From offsets make a good drawing of half the section on transfer paper.

foil moth sailboat

Construction

Buy flat-grained 2'x6s or 2'x8s, and then rip them to the designed board thickness. Turn every other ripping end-for-end to neutralize the effects of any grain that does not run exactly parallel to the blank, and to reduce tendencies to warp or twist (see sketch). Rotating the rippings 90 degrees to expose vertical grain will permit easier shaping with a plane. The last trick is to rip the end pieces of the nose and tail in half. Bonding with a couple of layers of glass tape between keeps the fine edge of the tail from splitting too easily and offers a precise centerline.

foil moth sailboat

First, tack the 1/8"-thick plywood template that describes the cross section shape to the blank's ends. This is sawn from the impression made when traced with the transfer paper you originally drew it on. The key to producing an accurate and symmetrical board is maintaining of a systematic removal of material from one side, then from the other. To do this, mark the shape to be removed, stick to straight-line shapes (see sketch). Use a smoothing plane to remove the wood. After planing to the guide lines on one side, flip the blank over and plane the same shape on the other side. The procedure is similar to producing a round shape from a square by first forming an octagon, and then flattening the resulting eight comers to produce a 16-sided shape and refining that until very minute flat surfaces. Fifty-grit sandpaper bonded with 3M brand feathering disc adhesive to a 1/2"-thick by ll'x4.5"-wide plywood sanding block is a good tool to use for fairing this out.

Reinforcing the Blade

Now you should decide if the board needs reinforcement. Your board requires reinforcement if the chord thickness is at or below 4/o of the unsupported span. The unsupported span of a dagerboard or centerboard is that measurement from where it exits the hull, to its tip when fully lowered. The unsupported span of the rudder blade is that distance from the rudder case to the tip. If it is a non-retracting blade, measure from the waterline to the tip. So, if the board extends 48" below the bottom of the hull and is 2" thick, .04", it should be reinforced for strength and stiffness.

If the board needs reinforcement, graphite fibers are a good choice as the strain-to-failure values of wood and graphite fiber are quite similar, hence they enhance each others performance. The high-modulus qualities of the graphite fibers provide stiffness. The addition of graphite will efficiently increase stiffness and ultimate strength. Don't be intimidated by the high-tech qualities of graphite fibers, they are easy to work with.

The amount of reinforcement needed is usually figured at 101/o chord thickness. Using the same board for our example, the board is 2" thick, then 10% equals .20" total reinforcement,.10" per side. Graphite fiber tows are .01" thick, so 10 tows per side should give the necessary reinforcement to do the job.

The graphite fibers will be laid into a channel that is routed into the shaped board (see sketch). The specific depth of the channel is determined by the above rule. Make the channel a little deeper than what's required (1/16") so you won't be sanding the graphite fibers.

foil moth sailboat

Take a one-inch-square stick to serve as a router guide. It's best to bevel the edge of the channel to reduce stress concentration. A rabbet plane serves best for this task. A layer of 6-oz fiberglass cloth is laid in the channel first (@ serves as an interface between the wood and graphite fiber), followed by the schedule of graphite. You can complete the entire bonding operation for a side in one session. Try to do the other side the next day. Finally, fair the reinforcement area with WEST SYSTEM brand epoxy and a low-density filler.

A layer of 6-oz woven-glass fabric should then be bonded to the faired board to improve the cross-grain strength and abrasion resistance. The radius of the leading edge should be about a 1% radius of the chord length, and may not permit the fiberglass fabric to lie flat around the radius. In that event, cut a strip of woven glass fabric on the bias (which will lie around a tighter radius) and bond it around the leading edge.

It is better to leave the trailing edge slightly squared rather than razor sharp. This will cause less drag and the centerboard will be less vulnerable to damage. Flatten the trailing edge to 1/16 or 1/8 of an inch on small boards, and closer to 1/4 of an inch on larger boards.

Axle Installation

Any board, no matter how stiff, will deflect. To prevent the axle hole that the centerboard pivots on from binding when deflection occurs, make the hole somewhat larger than the pin diameter. The perimeter of the axle hole should be thoroughly protected with fiberglass, as exposed end grain can absorb moisture.

foil moth sailboat

You can bond control lines for centerboards and rudders-in-place by wetting a slightly oversized hole (about 1.5" to 2" deep) with epoxy/404 @gh-Density filler mixture. It helps to mark the hole's depth on the rope with vinyl electricians tape to serve as a guide. Then, after soaking that end of the rope to be bonded in epoxy for a minute or so, shove it in the full depth of the hole.

Centerboards and rudder blades are often overlooked components that are of vital impedance to a boat's performance. Built correctly, they will reliably operate with the efficiency of a fish's fin, and you should note a measurable improvement in the quality of pointing and steering of your wind ship.

  • Jozset Bodig, Ph.D., Benjamin A Jayne Ph.D., Mechanics of Wood and Wood Composites, Van Nostrand Reinhold Co., New York (1982)
  • Johnston, Ken, Some 7houghts on Rudder Sections, Multihulls Magazine (Jan /Feb 1980)
  • Eck Bransford, Everything You Ever Wanted To Know About 505 Fins.
  • Lindsay, Mark, Centerboards and Rudders, Yacht Racing/Cruising Magazine (April 1981)
  • Abbott and Doenhoff, Theory of Wing Sections, Dover Publications, Inc. New York (1959). How to Loft Airfoil Sections - by J.R. Watson
  • Airfoils are cambered sections that are designed to produce lift (with minimum drag) as they operate in a fluid (air or water). Certain sections produce the most lift with the least amount of drag for a given condition.

When a designer chooses a foil section for a particular design, that section is often not produced to a close tolerance. I sailed on a boat that was noted for its erratic steering: the problem boiled down to an asymmetrical rudder. Operation of the airfoil section translates into measurable performance and handling benefits.

Whether you are going to build an airfoil from scratch or fair an existing foil with a template, you have to establish the section profile accurately.

Airfoil sections of all NACA (National Advisory Committee for Aeronautics) families are obtained from dimensions off the centerline from specific station points. Station points begin at zero at the nose. The stations are spaced more closely in the forward third of the foil section's chord length. @ area carries more shape, thus requiring more reference points to define it.

Chord line is defined as the straight line connecting the leading and trailing edges (or centerline). Station locations are expressed as a percentage, measured from the forward #0 station, of the chord line. Chord thickness is described as a percentage of chord line, measured in half breadths at a particular station.

foil moth sailboat

Durable Edges for Centerboards & Flip Up Rudders - by Jim Derck

When centerboards and flip up rudders drag across the bottom, the first fiberglass to abrade away is usually the leading edge at the bottom. This exposes the end grain of the wood, allowing water to be absorbed the length of the centerboard or rudder. The wood then expands, cracking the fiberglass along the leading edge and causing more problems. When it is time to repair the tip, it usually takes a long time to dry the wood for an effective repair.

To isolate the end grain before applying the fiberglass, cut diagonally from the leading edge to the bottom, apply several coats of epoxy to both pieces and bond the tip back on. In the future, if the fiberglass cloth abrades away and the wood gets wet, it is quick to dry out the short length of end grain prior to making the repair.

Here is a technique for fiberglass covering that has proved over the years to provide a long lasting trailing edge. When rebuilding an existing blade or before applying fiberglass cloth to a new blade, plane a flat on the trailing edge about 1/8"-wide (wider for large rudders and centerboards). When applying the fiberglass cloth, position the rudder or centerboard horizontally so the leading edge is up. Drape the fiberglass over the foil and trim so that it extends 1/2" past the trailing edge. If you make a full-scale drawing of the trailing edge of your board or rudder, you will get a better idea of exactly how much fiberglass cloth to leave.

After the fabric is wet out, use an #807 syringe to apply epoxy thickened to a non-sag mix with 406 Colloidal Silica to fill the gap between the two layers of fiberglass cloth.

Squeegee out excess epoxy and align the trailing edge so that it is straight. If necessary, clamp a plastic covered straight edge in place to make the fabric conform to the shape of the trailing edge. After the epoxy cures, do the final shaping with a sander or sandpaper and a block of wood. Use caution, the edge can be very sharp!

foil moth sailboat

Notes to the Chart

  • The values listed beneath the NACA numbers are the distances + and - to the foil surface from the centerline in % of chord.
  • Cut values for 0012 and 0018 in half to get 0006 and 0009. Double 0015 to get 0030. Halve 0006 to get 0003.
  • It's conventional to make the chord 5% longer than you really want, and then slice off the last 5% to a blunt edge after laying out the foil profile. Example: you want a 20-inch chord rudder. Calculate profile based on 21 inches, leaving off last 5% or 1-inch when laying out.
  • The nose of a NACA 00-- foil is always circular. Fair this in by eye as best you can using a compass or template or some sort (bottom of McDonald's coffee cup). This radius can be generated by the formula referred to above. (I'm still not talking.)
  • The thickness of a NACA foil is always greatest at 30% of the chord from the nose.

This is not the last word on foils by any means but I hope to save YOU the time, energy and frustration involved in finding out The Real Foil Story Without Studying Fluid Dynamics Full Time.

Personally, I'd rather go sailing!

Building a Moth

Member links.

  • Mid-Atlantic Musings
  • Europe Dinghy Moth
  • John Shelley's Moth Boat
  • Blackberry Boatworks
  • Earwigoagin
  • The Madmothist
  • Classic Moth Boat Facebook Page

Upcoming Events

foil moth sailboat

A Wildcard Enters “The Masked Singer” Season 11 on TV Theme Night — and Heidi Montag and Spencer Pratt Stop By

Group C's Clock, Lizard and Poodle Moth also returned to the stage on Wednesday's episode

Warning: This article contains spoilers for season 11 of The Masked Singer .

The Masked Singer got meta with TV Theme Night on Wednesday.

Judges  Ken Jeong ,  Jenny McCarthy , Rita Ora and  Robin Thicke kicked off the episode by covering the Gilligan’s Island theme song in character.

From there, Group C dove into sharing their favorite TV show theme songs, beginning with Clock .

“In my life, I’ve had my fair share of ups and downs, just like any good TV series,” Clock said in her clue package. “I’ve laughed and I’ve cried.”

Related: 20 of the Wildest Rules You Didn't Know Contestants Have to Follow on 'The Masked Singer'

The Mississippi River Trail and a motor also popped up in the package.

“Even though my marriages didn’t work out, something great came from those relationships, my beautiful children,” Clock continued.

Clock covered the Good Times theme song and then Jill Whelan from The Love Boat brought out an additional clue for the time teller: a cruise ship.

“Love and boat, two things that combine to make a hit, something I know firsthand,” Clock explained.

Debbie Allen , Janet Jackson and Stephanie Mills arose as guesses for Clock.

Poodle Moth fluttered to the stage next.

“In my life, I was raised to know one thing: sometimes the ones you love most leave without so much as a letter,” Poodle Moth said in her clue package. “My dad left a hole in my heart that I never have filled. I’d send him letters that are always returned to sender.”

A cat postcard, the drama and tragedy masks and fireflies appeared in the clue package, too.

“I’ve learned to use my talents to help other kids who are looking for their answers just like I was,” Poodle Moth concluded.

The dog-insect hybrid belted the theme song from The Hills , Natasha Bedingfield ’s “Unwritten.” Accordingly, The Hills alums Heidi Montag and Spencer Pratt introduced Poodle Moth’s extra clue: the Gilmore Girls theme song.

“I have a very special connection to Gilmore Girls that hits very close to home,” Poodle Moth said.

The judges thought Poodle Moth might be Connie Britton or Gilmore Girls stars Lauren Graham or Melissa McCarthy .

Afterward, Lizard slithered his way to the stage.

“As a little Lizard, I loved cartoons so much that I spent all my days drawing them,” Lizard explained in his clue package which also included cowboy boots and a doll of Lizard. “I got so good, I was offered a dream job at a huge animation studio. Yeah, The Mouse was chasing this lizard pretty hard.”

Lizard explained that he ultimately turned down the job in favor of being a performer and “my dad was shook.” Eventually, Lizard became “one of the most recognizable reptiles on the planet,” he claimed.

Lizard put his spin on “Scooby-Doo, Where Are You?” from Scooby-Doo, Where Are You?

Related: The Masked Singer Season 11 Reveals: See All the Celebrities Who Have Been Unmasked

“It’s the smoothest I have ever, ever heard,” Ora, 33, said. “I have never heard Scooby-Doo that swaggy.”

A real dog came out for Lizard’s additional clue. “A dog actually helped me reach an even bigger audience,” Lizard shared.

Michael Bivens, Ray J and Sisqó arose as possibilities for Lizard.

Wildcard contestant Sir Lion took a stab at entering the competition.

“I come from a well-known pride, but never took it for granted,” Sir Lion said in his clue package. “I jumped through hoops to become a ringleader in Hollywood, rubbing elbows with everyone from Tom Cruise to Tom Hanks . But in show business, the higher you climb, the harder you fall.”

The clue package displayed an anchor, an air balloon with Jerry Seinfeld and 30 Rockefeller Plaza as well. “I’ve landed on my feet no matter what this town throws my way,” Sir Lion resolved.

Lizard tackled Married… with Children 's theme song, “Love and Marriage.”

Season 3’s T-Rex gave Sir Lion a bone that read “co-star” for his extra clue. “I wasn’t in the cartoon, but I’ve costarred on a different show with Betty Rubble,” Sir Lion said.

The panel suspected Andy Cohen , Anderson Cooper and Ryan Seacrest might be under the Sir Lion outfit.

Related: Where to Watch Every Season of The Masked Singer

Host Nick Cannon  asked the judges and studio audience to vote on their favorite performance of the night and the two competitors at the bottom would face off in the Smackdown. Cannon, 43, announced that it would be Lizard and Sir Lion going head to head.

Lizard and Sir Lion each offered up a rendition of The Masked Singer ’s theme song, “Who Are You?” by The Who .

The judges ultimately chose Lizard to move forward in the competition, leaving Sir Lion to unmask. When Sir Lion popped out from under the furry man, TV host Billy Bush appeared.

McCarthy, 51, gasped, “I had no idea you sing like this!”

Never miss a story — sign up for  PEOPLE's free daily newsletter  to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories. The Masked Singer  airs Wednesdays at 8 p.m. ET on Fox.

For more People news, make sure to sign up for our newsletter!

Read the original article on People .

Michael Becker / FOX Clock and Lizard on 'The Masked Singer' season 11

COMMENTS

  1. MACH2 Boats

    The Mach2 - Championship Winning Foiling Moth. 36.6 Ned Goss Is this a world record speed for a dinghy? Ned Goss in a 18-25 knot Charleston sea breeze hit a peak speed of 36.5 knots, with a 10 sec average of 35.9 knots in his MACH2.

  2. Waszp

    As a development class, the International Moth has been a hotbed of foiling innovations over the past few years. Matthew Sheahan reports on a new accessible one-design version Waszp on display at ...

  3. Moth (dinghy)

    The Moth is a small development class of sailing dinghy.Originally a small, fast home-built sailing boat designed to plane, since 2000 it has become an expensive and largely commercially produced boat designed to hydroplane on foils though many are still built at home, typically at much lower cost.. The pre-hydrofoil design Moths are still sailed and raced, but are far slower than their foiled ...

  4. MACH2 Boats

    When you purchase a MACH2.6 Moth it includes the following: stunning carbon fibre clear coated hull, high modulus carbon foils (2.4/2.41), hi modulus 40mm mast, ... KA MSH5.4 deck sweeper sail, all rigging ropes and fittings, trolley, foil covers, boat cover, wing tramps with foot straps and; wooden indoor storage box (option to upgrade to a ...

  5. INTERNATIONAL MOTH SPEED GUIDE

    Max vang should be achieved in 15 knots and max cunningham in 18 knots. The Moth gets overpowered quickly, and from 18 knots upwards a softer tip or different sail is required. North's LA and DS designs have a slight variation in the luff rounds to cover the range, with the DS being aimed at 14 knots true wind speed.

  6. WASZP

    Product description. The WASZP project was conceived in 2010 and put into production in June 2016 by Andrew McDougall, designer of the world beating Mach 2 foiling Moth. The Moth is a racing boat with very few rules and therefore has developed into a boat that is beautiful to sail on the water, but not the answer to everyone's requirements ...

  7. Swift Moth

    This Swift is a joint venture between Damic Design and our building partners to create what we believe is the fastest and best built International Moth on the market. We have neatly 20 years of experience in the class which has helped immensely with the design and development of the platform. The end result is a boat that is easy to sail, looks ...

  8. 10 Fantastic Foiling Boats

    7. 600ff Inspired by the foiling International Moths, Linton Jenkins of Full Force Boats had the bright idea to build a foiling version of the singlehanded trapezing class, the RS600. The demand came from sailors who were too heavy for the International Moth (which we'd say has an ideal weight of 60-80kg).

  9. The foiling phenomenon, the history of foils

    "An Open 60 is a pretty powerful boat and when you compare the sail area:displacement ratio with that of a Moth there appears to be evidence that a foiling 60 could work.

  10. Sailing hydrofoil

    A sailing hydrofoil, hydrofoil sailboat, or hydrosail is a sailboat with wing-like foils mounted under the hull. ... Andy Paterson of Bloodaxe boats on the Isle of Wight is widely considered to have developed the first functional foiling Moth, though his boat had three foils in a tripod arrangement.

  11. Hydrofoils

    Swift Hydrofoils. Damic Design specialises in design and manufacturing of Moths and Hydrofoils for the International Moth Class. While Moth sailing is our passion, our main objective is to offer the fastest, most developed and best built boats and foils on the market. Our involvement in the class started in 2004, exposing us to the world of ...

  12. Foiling Moth

    The Foiling Moth appears to fly when the hull is out of the water. The MIT Sailing Pavilion has a Foiling Moth that uses wing-like foils to lift the hull out of the water. This 11 foot, 65 pound dinghy "flies" above the water is only sailed by the most advanced sailors. Learning to sail the moth means spending a lot of time swimming since the ...

  13. Moths to the Flame

    The International Moth remains the pinnacle of small-boat foiling, with devotees committed to "the progression". By Chris Museler Updated: June 8, 2020

  14. Bieker Moth

    The boat can fly higher out of the water, and has a larger vertical range to deal with both deceleration during foiling tacks and larger waves downwind. With 3D printed titanium components, the foil section thicknesses have been reduced for minimum drag at sailing altitude. Our horizontals are aggressively high aspect with low wetted area.

  15. The Foiling Moth Class

    Current National and four-time European Champion Chris Rashley tells us why you should try Moth sailing.From foil tacking to control systems, Chris gives som...

  16. International Moth Class Association

    About the Boat. The international Moth Class is the fastest one Person Dinghy in the World. Key Facts: Maximum Length: 3.355 m; Maximum Beam: 2.250 m; Total Weight: Unrestricted (~ 35-40 Kg) Maximum Sail Area: 8.25 m² ; Optimum Skipper Weight: 60-80 Kg. IMCA - Committee

  17. Foiling is Becoming a Sailing Style For All

    With the TF10, big-boat multihull foiling is now available to amateurs as well as pros. ... In point of fact, the monohull Moth class was the first to create a production foiler with the Mach 2. The Waszp soon followed, a simplified, budget version (at $11,000, half the price of a Mach 2) that has sold several hundred since its launch in 2016. ...

  18. Full Scale Measurements on a Hydrofoil International Moth

    a speed range between 2 and 14 fps. The heavy displacement is most realistic for the low speed data, while at higher speeds the foil lift unloads the hull and makes the lighter displacement data more appropriate. For speed above 14 fps (8 knots) the boat should be fully foilborne.

  19. How to Rig a Foiling Moth

    15. Pull the gearing to the middle of the range. 16. Attach the ride height uphaul/gearing cap. 17. Pull a little tension onto the wand shockcord. 18. Use a stiff ruler to check the foil flap gap with the ride height adjustment barrel control line in the middle of its range.

  20. How to home-build a Moth

    Wet out a piece of 200g plain weave on the board, wet the top of the deck foam and lay foam board on top on top of the plain weave. Wet the bottom of the foam and lay 200g biax on that. Lay Peel Ply on top of all the exposed carbon and then vacuum bag it. Test fit the deck again to make sure it is still a good fit.

  21. Moth Sailboat, Bladerider Moth

    Priced at $14,000, the Bladerider isn't cheap, but it provides an utterly new experience. Gliding above the water at double digit speeds, the only sound a faint hiss from the foils, you'll be ...

  22. How to Build Rudder Blades & Centerboards

    Cut values for 0012 and 0018 in half to get 0006 and 0009. Double 0015 to get 0030. Halve 0006 to get 0003. It's conventional to make the chord 5% longer than you really want, and then slice off the last 5% to a blunt edge after laying out the foil profile. Example: you want a 20-inch chord rudder.

  23. A Wildcard Enters "The Masked Singer" Season 11 on TV Theme Night

    Group C's Clock, Lizard and Poodle Moth also returned to the stage on Wednesday's episode Warning: This article contains spoilers for season 11 of The Masked Singer. The Masked Singer got meta ...