This is the part that allows you to lift our the water and fly over the surface.
Hydro foils work in a very similar way to an aeroplane.
There is a front wing, fuselage and rear wing. The rear wing is known as the stabiliser. Hydrofoil work due to the same aero dynamic laws as aeroplane wings. The from wing creates lift, the fuselage and rear wing create stability.
There are many different types and shapes of hydrofoil for wing foiling.
Starter Hydro Foil kit
To start you will need a big thick stable hydro foil. The front wing area should be between 1600 cm2 and 2100 cm2. As with the board you will quickly progress above the performance these offer so its good if you can find a second hand one. Look for mast size of around 70 cm made with aluminium. Advance set ups are all carbon fibre offering important stiffness and weight advantages but when beginning this is not as important as stability and ease of lift.
The hydro foils normally come in three or four pieces all held together with bolts. If you have an all aluminium set up take great care with the steel screws rusting into the aluminium. Release them often and apply a grease or other non oxidising cream. Trying to remove rusted in bolts is tricky.
Hydro foils parts are not interchangeable from one brand to another. So a front wing from one brand will not fit the fuselage from another brand. Even be careful to check within brand interchangeability.
The mast is the vertical section that attaches the front wing, fuselage and stabiliser to the board. The key element in this piece is stiffness. At first it will probably be aluminium and a little flexible. As you progress the stiffer the better so that all your inputs are translated straight into the foils. Stiffness also reduces any cavitation or vibration at higher speeds and offers a more stable base when changing foot position.
These connect the front wing and stabiliser with an attachment point for the mast. Made from Carbon or Aluminium. Not too impactful on overall performance.
This is the part that has the biggest impact on how the hydro foil performs. There are many different options.
They perform in the same way as aeroplanes. If you think of the type of aeroplanes people take lessons in they have short fat wings that offer good low speed lift and stability with also low speed stalling.
The same is true for a beginner hydro foil. Beginners will need a thick short wing with greater distance from the leading edge to trailing edge, known as the Chord. Area around 1800 cm2. These foils offer low take off speed, low flying speeds and greater stability.
As you advance you will look for more efficient faster foils. These will be less stable and require a faster speed to get you up and out the water. Once up and flying they will be easier to keep going and glide further.
Depending on what sort of conditions you want to wing foil in is a big factor on deciding the foil you should chose.
The most efficient foils are the high aspect foils. These have an aspect ratio (chord to width ratio) of around 9 to 1. Think of glider wings. The have great glide characteristics but are harder to turn, less stable and harder to get out of the water. Once up and riding they are very efficient and can even surf open ocean swells. Great for what is known as down winding. This is following the swell downwind on windy days with high seas.
If you want to surf steeper waves you will need a less high aspect foil. Thinner and wider than the beginner wing but not high aspect.
To find out more you can consult other wing foilers, manufacturers websites or on line user reviews. This is a big subject that is still progressing.
Stabiliser or Rear Wing
The main function of the rear wing is to keep things stable. It is a wing shape but upside down. It actually pushes downwards to stop the front wing lifting you out of the water too much as speed increases. The size and shape do have a big influence on the overall performance. Smaller thinners stabilisers are much faster but give less stability. As you progress less stability allows for easier turning and faster speeds with less drag resistance.
Other foil parts
For most aluminium masts there is a base that screws onto the mast that lets you attach it to the board. There is also an upper part that allows attachment of the fuselage. These are normally left attached. Remember to periodically loosen the screws and grease to avoid rusting.