Choosing the Best Foil for you- what to look for in a hydrofoil for surf foiling

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Many customers come into our shop or call us hungry for information about foiling, so we decided to make this post and video to share what we have learned about foil design and construction.  Surf Foiling is new to many and it takes a while to wrap your head around the many variables involved.  Keep in mind that most design features have both pros and cons.  A foil that works great for an expert rider is not always the best foil to learn on.  This page goes over the same information as the video with some added details, so watch the video and read the text for the most in-depth information. 

I have been foiling for close to 3 years now and foil technology has evolved rapidly in that time.  This video was recorded in August 2019 and many foil companies have come out with refined second or third generation foils that are much better than what we first started on.  Foils keep evolving and improving quickly so by the time you are reading this, some of the information may already be outdated, although the general concepts will still apply to understand differences in foil design and construction and we will update the text if new technology becomes available.  Should you wait until the technology improves?  No way, you would be missing out on too much fun!  There are many great options on the market right now, so for those sitting on the fence, don't hesitate, jump in, foiling is awesome and with the new hand wings it opens up all waterways to foiling, no waves needed, just a little wind.

These are some things I learned from personal experience, from talking to my foil crazed friends, and from listening to Eric Antonson's Progression Project podcast foiling series while I'm driving.  If you really want to geek out on foiling, I highly recommend this podcast series:  https://podcasts.apple.com/us/podcast...

A) Foil Design
Let's go over foil design first, starting with the front wing:

1) Surface Area:  The surface area of the front wing is a good indicator of lift the wing will create all else equal.  It is commonly measured as the projected surface area in square centimeters.  If you held a light straight over the wing, the projected area is the area of the shadow projected by the wing.

2) Profile:  Surf Foils generally have a thicker profile which creates more lift at lower speeds and is more forgiving to small changes in the angle of attack.  Foils designed for higher speeds (think kite foil racing) have much thinner profiles.  Thinner profiles generally have less drag, want to go faster and are easier to control at higher speeds but also have less lift at lower speeds, drop off earlier when slowing down, are more sensitive to small changes in the angle of attack and usually take more skill to ride.

3) Wing shape:  high aspect vs. low aspect shape.  This refers to the ratio between the wingspan and the chord (distance between the leading edge and trailing edge of the wing).  High aspect wings are wider and more slender while low aspect wings are more stubby and fuller.  
A glider plane is an example of a very high aspect wing shape with long, slender, thin profile, flat wings.  This wing shape is the most efficient and creates the most amount of lift and the least amount of drag from a given surface area.  It has good control at higher speeds but also drops off the foil earlier when slowing down, is harder to control at lower speeds and can be more directional. The efficiency of high aspect foils makes them great for pumping but they also take more skill to control on a wave.

Low aspect wings are generally easier to use for beginners, easier to control at lower speeds, create more lift at lower speeds and more predictable and forgiving to small changes in angles of attack.

3) Flat wings vs. curved wing shapes
Another thing to consider is the curve of the front wing.  A curved wing has a bit of built-in instability and almost wants to go from one turn into the next, which makes curved wings fun to use for carving in the surf.  The tips of the wings can also give the wing more directional stability (like fins on a board) that make the foil easier to control.  Turned up or down wing tips on the tail wing have the same effect, increasing directional stability. 

A downside of curved wings is a smaller projected surface area as the tips do not create as much upward lift.  A flat wing that creates upward lift even in the tips is more efficient and therefore creates less drag (although winglets can reduce turbulence at the wingtips).

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