All You Need To Know About Foils And Masts For WingSurfing

When I was recently searching for a wing hydrofoil set, I discovered many foils and masts on the market. As a windsurf veteran I know how much gear matters for fun and performance. So, I did some research to find out what’s the best buy and why. Here is a summary of what I found.

So, what are need to knows to buy the perfect wing, hydrofoil and mast? Hydrofoils for wing surfing come in many shapes and sizes. Depending on your skill level you might want, or need, different foil features. Beginners, for example, benefit from a large main foil that provides stability at low speeds, and a low take off speed.

A hydro foil is built up from: a main foil for lifting power, a stabilizer foil, a mast to connect them to the board and a fuselage to connect these three parts. The geometry of the setup determines its gliding characteristics while wing surfing it. Shapes and structures of the individual parts provide the wing surfer with typical features like high speed, stability or good carving ability.

Where to find what in this blog

During my research for essential knowledge to buy the best hydrofoil for wing surfing, I learned a lot. In this blog I try to chop all the info in to practical, easy to understand, bite-sized chunks. You find info about the working of the hydro foil parts. This helps to understand why you have a main and stabilizer foil, the fuselage and of course the mast.

The blog continues by explaining the different types of shapes of the parts and the geometry of the foil setup. This helps to comprehend what certain features, like drop-down wing tips or a forward wing placement, do for you as a wing foiler. For those who like to get in to the more technical details, I have inserted links to web pages that provide technical explanations.

Hydro Foils

The foil is the ‘under water wing’ that provides lift power. It’s shape forces the water that flows over it, to take a longer trajectory than the water flowing underneath. That way, the foil creates lower pressure above it, so it is ‘sucked’ upward. Just like the wing of an airplane.

As the foil lifts the board with the rider out of the water, the hydrodynamic resistance decreases enormously. The board is no longer displacing water while moving forward after all. Now the hydrofoil wing surfer needs only a fraction of the forward propulsion by wind power that a normal surfer or sailor would need.

For wing surfing the characteristic setup for a foil consists of a mast or strut, a main or lifting foil, a stabilizing foil and a fuselage that connects these three. As mentioned all these parts have specific shapes to provide the wing surfer with features.

Mast, Fuselage, Main Wing and Stabilizer Wing of a Wing Surf Hydro Foil

I will continue this blog by explaining about the different parts. After that I will dig in to the geometry of the parts combined in a setup a little further.

Foil sizes

The size, or better the surface of the foil (in cm²) has an important effect on the amount of lift it produces. If two foils with the exact same shape are moving at the same speed, the one with the largest size will produce the most lift.

For beginners a relatively large foil is nice. A larger surface helps creating a relatively low  that the takeoff speed. That way the beginner wing surfer requires less wing skills to generate speed for the take off. The takeoff speed is the speed at which the board with the surfer is lifted out of the water. The upward lifting force becomes larger than the weight of the board and surfer combined.

During my lessons I was using a 1800 cm² main foil as this was recommended by my instructor. For persons with a bodyweight between 65kg-90kg this seemed fine.

In my blog Hydrofoil Board Wing And Parts Explained For Fast Learning, I provide an overview description of the total gear package a hydrofoil wing surfer needs. There I already mentioned the difference between different ways to measure surface. Like you can see on the Gong Website < https://www.gong-galaxy.com/en/product/gong-wing-foil-allvator-rise-alu/ > they mention 3 measures of area for the same foil:

  • the Projected area: 1844 cm²
  • the Upper surface area: 2137 cm²
  • the Felt surface: 2100 cm²

So make sure you compare ‘apples with apples’ when you choose.

Hydro foil characteristics and what they do for you

Before I say more about individual foil features, it is important realize how complex the interplay of foil performance factors is. The final characteristic of a complete hydrofoil, is the result of the cooperation of a very complex set of individual features.

So, individual aspects, and their contribution to the whole can be explained. And that is useful to understand what to look for when buying or renting. But the eventual performance of a complete set is always the result of many aspects. So reading manufacturers descriptions, and even better, testing a foil before buying is always a very good idea.

Example:

Your car might have a stronger engine than mine. So, you could conclude that your car is faster. But if my car has special winter tyers, that provide good grip on snow, and your car doesn’t, than who will be faster on a snow covered circuit? Hard to say right? What if my windshield wipers don’t deal well with snow and yours are great at it? While you have four wheel drive with traction control and I only have rear wheel drive? Does the circuit have a lot of sharp corners?

All I try to say is the more features coming in to play, the harder predicting a performance will get. So the info in this blog is the result of my pre buying research. I tried to learn as much as possible to give a good understanding of what to look for and why. ‘Try before you buy’ is my motto, and the above example is meant to explain why.

Size or surface of the hydrofoil:

Foils for wing surfing are offered in a broad range of surface sizes. Just looking at the website of Starboard, Naish and Cabrinha gives an indication. Here foils are offered with sizes between 1050 cm² and 2400 cm².

An example of the 1050 cm² foil is the Naish Jet Complete. The Starboard S type comes in sizes between 1200 and 2400 cm². F One produces several hydrofoils. I tested the Gravity 1800 FCT .

The Starboard website explains ‘the smaller the size the faster the speed’. Doing some research on the Naish website made me aware of the fact that another variable is important when choosing a hydrofoil surface: your body weight. For example they mention the Jet 1050 being ideal for riders 120-170 lbs.

A heavier rider needs more upward lift from the foil to take off. Thus a larger surface can be needed. The same can be found on the Gong-Galaxy website. Here the smaller surfaced models are described as ‘for riders under 75kg’. Whereas larger surfaced foils are described as ‘for riders over 75kg’.

Foils Aspect Ratio

The aspect ratio is the ratio of it’s sizes in different dimensions. For a wing that is the ration of it’s length and it’s mean chord, (or width for dummies). So, a long, narrow wing has a high aspect ratio. On the contrary, a short, wide wing has a low aspect ratio.

Aspect Ratio Has Effect On Speed And Drag

According to Wikipedia < https://en.wikipedia.org/wiki/Lift-to-drag_ratio >  higher aspect ratio gives a lower lift to drag ratio. That would mean an advantage for speed. Applied to hydro foil wings a quick glance at the Starboard website teaches that their X-type foil is 4 knots faster than other wings, all other things equal. They say the X- wing is fast as a result of the higher aspect ratio (among other things).

The same can be see when comparing F-Ones Gravity and Phantom wings. The Phantom Carbon 1280 scores a 100% on their own speed indicator and has an aspect ratio of 5.9, whereas the Gravity 1200 Carbon scores a 90% on speed. It has an 3.9 aspect ratio. Larger models come with more aspect ratio to maintain the glide and avoid unnecessary drag.

Aspect Ratio Has Effect On Maneuverability

The higher the aspect ratio the higher the moment of inertia that has to be overcome. When rolling < https://en.wikipedia.org/wiki/Slow_roll_(aeronautics) >, that’s means moving around an axis, in this case the fuselage, a longer wing gives a higher moment because of the longer moment arm (freely translated from Wikipedia).

If we compare F-one’s Phantom carbon 1280 and Gravity 1200 Carbon scores again, we see a 100% score on carving for the Gravity with the 3,9 aspect ratio. The Phantom with the 5.9 aspect ratio is designed to be faster, but it’s maneuverability, or in this case it’s carving, only scores 85%. The website describes at the technical specification section that the smaller Phantom models “take advantage of their more compact shape to offer high-end maneuverability..”.

Leading Edge of the Main Foil

Apart from the aspect ratio there are other features influencing the foils’ performance. The leading edge design is one of them.

From the Starboard website I learned the following. Sweeping leading edge lets the wing carve and react smoothly. And a rounded leading edge and a more symmetrical shape blends speed, control, stability and stall-resistance. Despite searching various manufacturers websites I couldn’t find more (while using the search term “edge” in the foil descriptions. Searching on a bit for leading edge. For those who want to read more about wing design in generals, and the different types of leading edges I refer to Wikipedia.

Foil Profile

The profile of the foil is the last shape feature I researched. Like an airplane wing, the foil is designed to create lift when the wing moves forward through water. The profile plays an important role here. When moving forward through the water the water molecules are forced to flow either under or  over the wing. The profile is designed to force the molecules that go over the wing to travel faster because their trajectory is longer. Their fellows flowing under the wing travel a shorter distance to its end, where they meet again.

This, of course, is a very simplified representation of reality leaving stuff like drag coefficients out. If you really want to dig in to the physics and formulas this blog might be a good start.

Types Of Foil Profiles

Thin profiles are characteristic for speed oriented wings like the Starboard X Type. In the range of foils offered on the website, the X types is described as the one with the thinnest profile. This unleashes the next level in speed according to the manufacturer.

Of course I researched websites of other brands, to find more info about profile thickness. I haven’t yet found other one-fold descriptions of a clear linear relationship between profile thickness and additional riding characteristics. Most brands describe profile in a sense that it has a V shape or a double concave. Also profile features like drop-down wing tips that act like thruster fins can be found. All describe these features to explain why the foil possesses features like good carving or stable riding performance.

If I want a foil for playing in the surf I look for easy rolling and turning. As a beginner I first want a foil that provides low takeoff speeds and a stable ride at low speeds. It seems that these features can be combined relatively good. Compromises have to be made more radical when the rider wants pure speed. I saw descriptions mentioning that the designs for pure speed had sacrifices in the area of lift and low speed stability performance. 

I think this is the part where the dynamics of many variables working together become very complex. From here I feel I need to rely on a little thrust in the manufacturers description, testing and asking other riders for user feedback. I hope to once write a blog about a few foils tested by me. But for now, this is what I have to work with. I hope it was helpful to you too.

Aluminum or Carbon

The last aspect of hydrofoils I researched is the materials used for construction. Aluminum and carbon seem the two dominant candidates for masts and fuselages. Wings are often made of carbon. They are also built in fiberglass around an injected foam core. Some brands, like F-One describe the use of a special coating over the main wing construction to protect it from damage.

Some brands offer the same model in two construction types. Example is the F-One Gravity 1800. It is offered as a FCM edition. That is fiberglass around a foam core. And a carbon edition. The carbon editions use the same aluminum mast. The main wing, fuselage and stabilizer wing are constructed of carbon.

Differences Between Aluminum and Carbon

The first thing that caught my eye was the huge differences in pricing. Carbon edition seems to be much more expensive. For example I found a US website offering the same wing in both construction types. (Just for the record, I have no connection to this business nor do I receive any commissions.) The aluminum edition costs $1149.- . That is the price for a complete pack including 2 main wings, a fuselage, a mast and a stabilizer wing.

The Gravity 1800 carbon edition costs $1159,- , but as far as I understand, that is the price for 1 main wing delivered with 2 fuselages. The price for an aluminum mast set is roughly one third of the price at which its carbon sibling is offered.

So, what is the huge advantage off the carbon editions? As a windsurfer I tested the same board type in carbon and more economic versions. The carbon edition was lighter and more stiff. Clearly outperforming its sibling. Carbon is used in many fields of sports to manufacture high performance gear. It’s used for the construction of racing bikes, wind surfboards and other gear where stiffness and weight have impact on performance.

For hydrofoils this seems the case too. Carbon is used in foil parts to make them as light and resistant. Of course, because of typical features of the material it can not be used for all parts. Screws for example are made out of metals. To learn more about the exact differences between aluminum and carbon you can visit this blog that I consulted for research.

What Is a Hydrofoil Mast?

The mast of a hydrofoil is the aluminum or carbon piece that connects the board to the fuselage. It creates space between the foil wings and the board. This space enables the rider to glide over the water surface.

The mast is connected to the fuselage. The fuselage is the horizontal piece that holds both the main wing and the stabilizer wing of the foil in place. Together they form the foil. A connector piece and a few strong screws are required to connect the mast to the board.

Wind Foil Mast Length

I researched the websites from several wing hydrofoil brands to find info about mast length and it’s effect on riding. A quick search already shows that most brands offer masts in different lengths.

Starboard for example offers their carbon mast set in lengths from 72 up to 102cm. The aluminum mast set is available in both a 72cm or the 82cm edition. Other brands show similar mast lengths.

Wing Foil Mast Length For Beginners

Experts blogs that I consulted agree that for beginners a short, 80 cm for example, mast is recommended. Gong Galaxy states this explicitly on their web page. Shorter masts enable beginners with a faster pumping motion. They are easier to balance too. Another advantage is that the foil is less deep in the water. So, the beginner can practice in water that is less deep, without crashing the expensive foil in the bottom. A too short mast, on the contrary, will quickly be limiting according to the Srokacompany’s. Therefore they recommend a 80 cm mast for beginners.

Wing Foil Mast Length For Advanced Riders

The same Gong website recommends longer masts for more experienced riders. Longer mast give more clearance to the water. According to the BluePlanetSurf blog this helps more experienced riders making sharper turns. During a sharper turn the board is more on it’s side. So more clearance is helpful to not let the rail hit the water.

Although this article is about surf foiling it seems easy to understand that the same goes for riding a wind foil. Especially in waves. That is another advantage of a longer mast for advanced riders. Small waves are more likely to pass under the board, if the mast provides more clearance from the water surface.

Wind Foil Mast Shape and Construction

Wind foil masts can be constructed in several ways. Carbon and aluminum are the main materials used. Some brands, like Naish use a foam filled aluminum construction.

Carbon mast can be more stiff. Depending on the grade of carbon used, and the layup, both side and torsional stiffness and strength can be great. This gives a more direct feeling while riding the foil. The longer the mast is, the more important stiffness becomes. If the mast lacks stiffness it can give a limp or wobbly  feeling. Carbon mast can be hollow. Load-bearing I-beams can be applied for maximum strength and stiffness. They run down the length of the mast segregating the hollow space inside.

Wing Foil Mast Connector

There are several standard connection systems on the market. Some brands manufacture their masts in a way they can connect to more than one system. Naish Aluminum Masts, for example, are available as Direct Connect as well as Deep Tuttle and Abracadabra Connection Systems.

The system used determines the way the mast is connected to the board. Because of the huge forces that are working on the connection, it needs to be strong. Important here is that, the longer the mast, the longer the distance vector. Thus, the larger the torque force on the connecting system.

Different systems use different top plates. They are used as connectors between mast and board. The top plate is connected to the board, often by four screws. It also is connected to the mast. This can be done by inserting the mast in a special custom fit opening that fits neatly around the top shape of the mast. Screws are used to pull the mast strongly in to it. Some masts, like the carbon masts by Starboard, have the top plate fused with the mast to form one monolithic carbon piece.

Wing hydrofoil Fuselage Function

The fuselage of a hydrofoil is the part that connects the main wing with the mast and the stabilizer wing. Apart from connecting parts the fuselage has a function in setting up the geometry of the foil. That way it has impact on the gliding characteristics. The fuselage also determines how far the front wing is placed forward. This also has an effect on turning, speed and upwind / downwind performance.

Wing hydrofoil Fuselage Geometry Or SetUp

The length of the fuselage has an effect on the gliding characteristics of the complete hydrofoil it is part of. According to BluePlanetSurf < https://www.blueplanetsurf.com/blogs/news/choosing-the-best-hydrofoil-for-foil-surfing/ >, the longer the fuselage the easier the pitch can be controlled. Making it easier to glide at a steady altitude. A shorter fuselage enables shorter turns and easier pumping. Longer fuselages with a more forward placement of the front wing are used for speed setups. An example is the Starboard Race Plus.

This fuselage is also supplied with different angle spacers that are used for alternating the setup. These are also called adjustment wedges as you can see in this shop. The angle at which the stabilizer and front wing glide through the water impact the acceleration and level of control at high speeds. More angle gives more lift. Less angle gives more speed according to Starboard.

The more parallel the wings are setup, the better the performance on these to variables. Of course, this can have an negative impact on other variables that are more important for beginners. For beginners it is recommended to keep the factory geometry.

What is a Wing Hydrofoil Fuselage Made Off?

A quick search showed me that aluminum is the material of choice for most brands when it comes to fuselages. Starboard describes that the extra weight of aluminum over carbon, is not a disadvantage when it comes to fuselages. Because of the specific construction features, aluminum beat carbon in their repeatedly testing program. Here advanced mechanical engineering knowledge is required to explain the exception to the rule that carbon is more stiff.

Wing Hydrofoil Stabilizer Wings

As the inserted links show, I have read quite a lot of hydrofoil product descriptions writing this article. I noticed that most spend way more text describing the main wings features. The stabilizer wing seems to be designed to support the main wings performance. They often come as a recommended counterpart with the main wing in a set.

The surface of the foils stabilizer wing, also known as tail wing, is much smaller that it main counterpart. The stabilizer wing surfaces I saw during my research where between 250 and 450 cm².  I noticed that the same stabilizer wing is used in a pair with very different main wings. For example, Starboard offers the RAZR 250 in a pair with the S-Type, E-type and X-type. The same tail wing used with main wings in sizes between 1100cm² and 2400cm².

It’s only the Ocean Surf Wing set that forms the exception. Here both the 2000 and the 2400cm² main wings are paired with the Wave270 tail wing. Other brands, like F-one seem to have a little more variation in their stabilizer wing collection. Nevertheless they also use the same stabilizer for more than one main wing size.

Screws For Wind Foil Mast and Fuselage Connection

Screws are necessary to assemble a wing hydrofoil. These connections must be made:

  • The top plate to the board. Usually 4 very strong screw with a 30mm length;
  • The top plate to the mast (unless the are fused with the mast like mentioned above);
  • The fuselage to the mast of the foil;
  • The front wing to the fuselage of the foil;
  • The stabilizer to the fuselage of the foil.

Luckily most brands that I checked, include the required screws for assembly in the mast or foil set pack. Also, in case you loose a few, many brands offer screw packs on their website for replacements or backup. An example is the screw set that Gong Galaxy offers.

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