Deck-stepped and keel-stepped masts perform the same basic job, but the way the spar is supported at deck level changes the mast structure, installation method and some of the information needed when planning repairs or replacement.
The basic difference
Deck-stepped mast
The mast heel sits on a mast step at deck or coachroof level. Compression loads are transferred into the supporting structure beneath the step.
Keel-stepped mast
The spar passes through the deck or partners and continues down to a step lower in the yacht, commonly on or near the keel structure.
Different mast length
A keel-stepped replacement mast is longer below deck. Do not use an above-deck measurement as the complete mast length.
Different interfaces
The partners, deck seal, wedges/chocks and lower mast arrangement become part of the replacement specification on a keel-stepped rig.
What changes for maintenance and inspection?
Deck-stepped spars make the mast heel and deck step easy to access once the mast is unstepped. Keel-stepped spars also require inspection around the partners and the below-deck section, where moisture, movement or hidden fittings may be present.
What changes for replacement?
Which is better?
There is no universal answer. Yacht structure, original design, interior arrangement, rig geometry and the intended loads all matter. For replacement work, the priority is to reproduce or properly engineer the required interfaces rather than to change stepping arrangement casually.
Replacing a deck- or keel-stepped mast?
Send photographs of the heel, deck/partners and the yacht's current mast arrangement together with the mast ID and overall dimensions.