RDM vs SDM - Reduced Diameter vs Standard Diameter Masts

Summary

Masts come in 2 base diameter types: SDM, and RDM. Mast extensions need to be compatible with the mast type. Buy a SDM extension for standard diameter masts. Buy a RDM extension for reduced diameter masts.

SDM - Standard Diameter Masts

SDM standard diameter masts are the original style masts. Starting around 1990 they were manufactured using a semi organized industry standard.

SDM masts use SDM mast extensions and SDM boom heads.

SDM masts are lighter because the walls are thinner. Race and freeride sails over 6.0m should use SDM masts.

RDM - Reduced Diameter Masts

RDM reduced diameter masts are designed for smaller sails, thicker mast walls, and stronger construction for wave sailing. The smaller diameter helps make rigging your sails easier. Sail handling is easier - especially water starting.

Recommendation

Start out with RDM masts and extensions, especially for learning. RDM masts and extensions for sails under 6.0m.

If you are buying your first mast - buy RDM and look for masts with a carbon content between 40-80%.

Free-race and race sails should use standard diameter masts.