After having owned the Balz Pro 799 and 899 I recently switched to the MEDUSA PRO 869.

Overall I'm quite happy with it as this front wing is doing amazingly well for its size. However I had a few occasions where I suddenly crashed, without any clear reason. When this happened I was going in a straight line, half-wind course, standing straight above my board (so no angle to the water surface) at some 30+ km/h. A descent speed but nothing spectacular. It felt like the front wing instead of creating lift, suddenly switched to creating a dive-motion, causing me from a glide to a sudden nose-dive+crash.

By the way I never experienced anything like this on my previous 799 and 899 front wings.

Anyone an idea of what is happening here? Any similar findings? Or maybe a tip how to solve this?

The SABFoil gear I use:
Mast - M83K
CARBON RAIL PLATE - CP02K with Q01K quick release system
Fuselage - F703K
FRONT WING - MEDUSA PRO 869
Stabilizer - S399

Britfoil360 said..

rkolijn said..
After having owned the Balz Pro 799 and 899 I recently switched to the MEDUSA PRO 869.

Overall I'm quite happy with it as this front wing is doing amazingly well for its size. However I had a few occasions where I suddenly crashed, without any clear reason. When this happened I was going in a straight line, half-wind course, standing straight above my board (so no angle to the water surface) at some 30+ km/h. A descent speed but nothing spectacular. It felt like the front wing instead of creating lift, suddenly switched to creating a dive-motion, causing me from a glide to a sudden nose-dive+crash.

By the way I never experienced anything like this on my previous 799 and 899 front wings.

Anyone an idea of what is happening here? Any similar findings? Or maybe a tip how to solve this?

The SABFoil gear I use:
Mast - M83K
CARBON RAIL PLATE - CP02K with Q01K quick release system
Fuselage - F703K
FRONT WING - MEDUSA PRO 869
Stabilizer - S399

When I first started using the W1000 I had a similar experience and found that putting a 0.5 shimm on the rear stabiliser sorted it out and it has never happened since .

That's the standard -0.5 degrees shim of SABFoil you refer to, right? As I also read that some people were using positive shimming (by reversing a standard Sabfoil -0.5 shim)

I'll try so for my next session. Thanks.

Not unusual with glossy masts, make sure you clean the foil with window cleaner just before you hit the water and then don't touch it. Any greasy finger prints on the foil will help aid ventilation at higher speeds. Race sanding the mast to a nice matt finish really helps too.


Your new wing is probably a bit quicker and your now in the world where kitefoilers struggle with ventilation, above 25 knots and things get interesting, some foils are just more prone to it than others. So first try giving the foil a really good clean, and see if it makes a difference. I clean my foil before every session.

Here is my take on ventilation. The front wing creates a low pressure area on the upper surface, it is virtually sucked up creating lift, this is how an aerofoil works. The larger the camber of the upper surface the lower the pressure and greater the lift.
But, this low pressure can also suck air downwards along the mast and onto the front wing, instant crash. Pushing a higher camber wing at speed with a dirty or poorly designed mast means plenty of ventilation.
Some masts ventilate more than others, Naish have tried to address it in their new HM mast by narrowing the chord of the mast then widening it just before the fuselage, hopeful of the air leaving the mast before getting to the wing.
Aircraft have used wing fences in the past to help avoid the issue.