A common term that you hear when discussing handling characteristics of race cars is the distinction between sprung and unsprung weight, that is to say the difference between the mass of the car that is suspended by the suspension, and the wheels and chassis that are not.

For a foiling windsurfer, by analogy, we can assume that the sprung weight is the rider and the unsprung weight would be pretty much everything else: the foil, the fuselage, the mast, board, sails, booms, and rig, etc. I'm no engineer, but I'm naturally curious, and I know there are those on these forums with better understanding of these issues than me.

Which brings me to my question: all things being equal in terms of design, shape, and rigidity, is there a significant advantage to be had in using lighter carbon fiber components in the foil/fuselage/mast assembly as compared to the heavier aluminum assemblies?

I realize there are of course issues with regards to stiffness and torsional rigidity, but putting those aside, is there a performance advantage in saving a few ounces in terms of component weight? Interestingly, when I look online at most of the foil company websites, the weight of the components is rarely mentioned.

Unless we're talking multiple pounds, can't imagine it making much difference. Granted less mass is going to accelerate faster, power to weight ratio etc., but a few ounces ?, don't think I could detect any difference.

Definitely noticeable in the rig and front of the board. In the foil itself? Not so much unless you are carrying it.

Isn't it all about rotational inertia? Mass close to the pivot point doesn't matter much, but further from the mast its effects are amplified by leverage. Think of the skinny kid out at the end of a seesaw balancing the fat kid closer in

From the Starboard Foils site.......
Aluminium V8 Mast Set
The stiffest and heaviest mast option.
A heavy mast helps to sink the foil for more stability before take-off

There are some true blue spin doctors working for Starboard. This guy had a future as a politician!
Makes me feel good about my old Manta mast, it's stiff, but also the heaviest in the world.
Manta were onto a winner there!

"by analogy, we can assume that the sprung weight is the rider and the unsprung weight would be pretty much everything else:" Well, on a fin maybe. On a foil I'd say that sprung weight is the foil itself and unsprung is everything else.

Opposite. If we use the race car analogy, I think the unsprung weight is the front wing since it is the only thing pushing UP (like car tires). The sprung weight is everything else, which is pushing DOWN (like the rest of the car).

Unsprung would be anything rigidly mounted to the foil: ie the board and rig.
The only sprung weight is the rider.

I agree.. I'm thinking unsprung weight can be only referred to moving or spinning parts.. of which there are none when foiling.

I have once read on the dutch forums that 1kg of board weight equals roughly 10kgs of rider weight when using a fin. I dont know what assumptions the engineer in question who made the calculations did to make that claim though.

On the other hand, rig weight makes way more of a massive difference in practice than rider weight. Trying to get a 10kg heavier board to fly is much much harder than getting a 10kg heavier rider to fly. Ofcourse this example is extreme, but I can easily feel the difference between different constructions in terms of early flight.