Independent guide: Mast step and compression repairs are structural. Use an experienced shipwright or rigger.
Quick answer
The mast pushes down with a force several times the boat's displacement when the rig is tensioned and sailing. The mast step — on the keel for a keel-stepped mast, or on deck over a compression post for a deck-stepped mast — carries that force into the hull. Steps corrode when bilge water sits against aluminium and stainless, and compression posts can rot, crush or lose their bond. Inspect them whenever the mast comes out.
Common problems
| Problem | Where | Signs |
|---|---|---|
| Heel corrosion | Keel-stepped | White powder, pitting, loose heel fitting |
| Step plate corrosion | Keel-stepped | Wasting of plate and fasteners |
| Compression post rot or crush | Deck-stepped | Sagging deck, slack rig |
| Bulkhead delamination | Either | Cracking, movement, sticking doors |
| Floor or grid damage | Keel-stepped | Cracks in the structure around the step |
Inspection and repair
With the mast out, the heel casting and step can be removed, cleaned and examined. Compression posts can be checked for moisture and movement. Repairs range from replacing a heel casting and fasteners to rebuilding a post or bonding in new structure. See mast-out rig service.
Related
Frequently asked questions
What are the signs of a failing compression post?
A deck that sags or cracks around the mast base, a rig that keeps going slack, doors near the mast bulkhead that start to stick, water staining or rot at the post base, and crazing in the headliner around the post.