The simple answer: As their names suggest, the primary difference is that RDM masts are narrower in diameter than SDM masts. So much so, their narrowness requires a skinny (RDM) base extension and – in some cases – a shim to ensure a tight boom connection. See photo below.

So why choose an RDM or an SDM mast? Below are two hard, fast rules to keep things simple.

Choose a SDM mast for sails 6.5 and larger. Sails in this size range typically demand masts 460 centimeters and longer. A standard diameter mast offers stiffness and weight savings best matched for these large sails.

Choose an RDM mast for sails 6.4 and smaller. Sails in this size range typically demand masts 430 centimeters or shorter. A reduced diameter mast offers unrivaled durability for the higher winds these sails are commonly used in.

Are There Exceptions to the Rules Above? Yes. Here are two major ones: A few sail makers recommend RDM masts in sail sizes larger than 6.5; riders in surf locations should opt for the durability of RDM masts, even for sails 6.5 and larger.

RDM Masts (skinny masts)
– Virtually unbreakable
– Best for flat water and waves, 12-45 mph winds, and sails 6.4 and smaller
– Primarily available in 310, 340, 370, 400 and 430 cm sizes

SDM Masts (fat masts)
– Stiff, lightweight and durable
– Best for flat water, 2-25 mph wind speeds, and sails 6.5 and larger
– Primarily available in 430, 460, 490 and 520 cm sizes

Other questions? Masts are nuanced, and a vital rig component to squeezing the most fun out of each and every windsurfing session. The above offering is a basic overview. Don’t hesitate to contact our mast experts or call 888 509 4210.


Eddy Patricelli was the editor of WindSurfing magazine from 2001-2007. He has been sailing the Gorge for 20 years. See his best video tip for getting your kid hooked on windsurfing here.

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