Warm tropical waters provide less lift and tropical air creates less wing power. That is why floatier boards, bigger wings and bigger foils are generally preferred in the North.
A longer MAST length (~80-90cm) is great for going fast, popping jumps and surface clearance in messy chop.
A shorter (~60-75cm) mast is less daunting for beginners, has less resistance on take-off, more clearance over shallow banks, make touchdowns easier, but breaches more readily.
Longer FUSELAGE (~60-70cm) will smooth out changes in pitch in exchange for a wider turning arc and better pumping. Shorter fuse (~50-60cm) has less resistance and tighter turns.
More FRONT FOIL span equals better glide. A 900-1000mm span is good for Darwin. A thicker profile foil lifts earlier and can be forcefully pumped on to foil by alternately pushing with the front, then the rear foot. High aspect foils require a higher board speed for take-off and a delicate, higher cadence pumping technique.
Higher aspect foils will go upwind better, especially paired with a longer stiffer mast, longer fuse, and a small, slim profile, high aspect STABILISER. A smaller stab also goes faster. Start with one that is fairly big and downsize as you improve.
Changing a stabiliser is the cheapest way to alter the characteristics of a hydrofoil. Shims can be added to the stabiliser to create less lift and a higher top speed due to less drag.
Aspect Ratio = (span in cm)2 / area in sq.cm
Angle of Incidence = angle of the front wing and stabiliser relative to the fuselage. This is a fixed geometry but shims can be added to flatten the stab angle.
Angle of Attack = the angle between the centre line of the foil and the flow of the body of water across its surface. This changes constantly due to your movement on the board, going different speeds, cranking on the wing, wind gusts, moving through a tidal run, wind chop, etc
More speed equals more lift, and more effort is required on the front foot to maintain a flat Angle of Attack which prevents the foil breaching the surface.
FRONT FOIL EXAMPLES
<This description refers to the top two foils in the image below>
The original HS1850 (2020), an early Armstrong release, and the MA1475 (2023) have similar lift and stability. The thicker profile 1850 lifts sooner whilst the thinner 1475 goes faster and has better glide due to a bigger span.
<This description refers to the third and fourth foils in the image>
The HA1125 v1 (2021) and the HA980 v2 (2024) both have an aspect ratio around 10.0. They experience similar low-end lift and top speeds but the v2 series provide improved pitch stability, breach recovery, steady lift and easier turning.
These user-friendly improvements were a result of advances in foil design, notably concave sections on the trailing edge. The newer foil profile varies incrementally along the wingspan to optimize water flow and keep lift consistent at various bank angles.
<This description refers to the bottom foil in the image>
The DWP (downwind performance) series was released at a similar time (2024) to the HA high aspect v2. The DWP930 has a very high aspect ratio of 13.0 and is designed for open ocean sup foil racing.
A reduced chord and deeper concave allow the foil to match the speed of deep water long wavelength swells. The design works well for wing foiling but it is technical to handle having a span of 110cm.
In summary, all foils will work but there are advantages to lighter weight, rigid construction and modern design. And in Darwin, Go Big.