The choice between a fat (SDM) or skinny (RDM) masts remains a big source of debate in the windsurfing community. Mast diameter affects far more than just compatibility of your equipment! The change in this core element of your rig heavily affects the handling and characteristic of your sails. Because of that, choosing the right one can make a difference between a better or worse windsurfing experience. But how to know which mast diameter to choose?
More manoeuvrable and forgiving than SDM
Better suited for stronger winds (flexes to ease off gusts)
Curves more under downhaul, lowering centre of effort
Much more durable than SDM
Lower low-end power due to flatter sail profile
Less immediate transfer of power
Slightly heavier than SDM, especially in bigger sizes (>6.0m²)
Stiffer and more sensitive than RDM
Better suited for early planing in low winds
Stiffer, provides more support for bigger sails
Lighter than RDM, especially with big sails (>6.0m²)
Generally thought to work better with camber rotators
A lot less forgiving than RDM, harder to control
A lot less durable (less impact and bend resistance)
Can suffer from heat damage when used with cambers (rare)
Conclusion: which mast diameter to choose?
Anyone from a beginner to a freestyle champion can benefit from using a sail that feels lighter and better in the hand. That’s why at Poole Windsurfing we exclusively use RDM masts on all our sails. The lightness of the sail makes it much easier to intuitively learn the best positioning and control. In general, if you use sails smaller than 6.0m² and you’re not into racing, RDM is the way to go.
As for SDM, it definitely still have a place on the market. However, they certainly have fallen from being the dominant standard to more of a niche market. Similarly to the seat harness, SDM is now mostly found on large, cambered rigs. Optimised for maximum performance, they are a lot trickier and less convenient to handle. Hence the recommendation: don’t buy SDM masts unless you really know you need them.