mast step

[Dan Irvine]

The compression post on my boat project ends at the cabin overhead. The cabin overhead is about 1 1/4" thick. I propose to construct my mast step from stainless sheet or cast bronze. In the interests of keeping weight down I propose to have a hardwood spacer and through bolt the step to the plate on top of the compression post. Is this acceptable or should the spacer between the mast step and the top of the post be metal? Waddayathink?

[Jack Heinlen]

If I'm seeing this, I think a hard mahogany, or teak, or even white oak would be fine. Teak would be nice because you could just let it weather.

[Dan Irvine]

Thanks Jack. The wood spacer would be not exposed to the weather at all. It would fit between the bottom of the mast step and be throughbolted to the plate on top of the compression post, soooo I take it I should be able to use any really hard wood? What about grain orientation to prevent squishing, cracking etc?

[Jack Heinlen]

I guess I'm not seeing this yet. I imagined a thin stainless or bronze step to accept the butt of the spar, and wood fitted between that and the cabin top to take up the shape of the top. But now it seems your plan would fully encase the wood. In a sort of box?

Something you might want to consider--and someone else here will have more experience with epoxy in compression--is fillng the box with structurally enhanced epoxy. Meaning epoxy thickened with a structural filler. Tough stuff, and no worry of rot.

Say some more, maybe we can get the ball rolling, things are kind of slow around here just now.

[Ian McColgin]

Dan, you plan is fine and standard. If the plate at the top of your compression post and the plate at the step are similar size, which they must be to through bolt, then you could slice the wood so's the grain is verticle for a bit more strength. This exposes huge endgrain and could lead to water intrusion and rot unless you super seal it. If you make it of oak, just keep flooding it from both ends with CPES and you'll end up with a cellulous/epoxy composit that will hold up fine.

But simpler would be to use some common physically hard (but not necessarily hardwood hard) wood like pine laid with the grain horizontal. That also will have abundant compression resistance.

G'luck

[JimD]

Originally posted by Jack Heinlen:
I guess I'm not seeing this yet. I imagined a thin stainless or bronze step to accept the butt of the spar, and wood fitted between that and the cabin top to take up the shape of the top. But now it seems your plan would fully encase the wood. In a sort of box?

Something you might want to consider--and someone else here will have more experience with epoxy in compression--is fillng the box with structurally enhanced epoxy. Meaning epoxy thickened with a structural filler. Tough stuff, and no worry of rot.

Say some more, maybe we can get the ball rolling, things are kind of slow around here just now.I'm not quite seeing it either, but like Ian says next you mightn't need the most expensive wood. How big is the boat and how much compression are we talking about? I built up a 6" wooden step base on my cabin top with just 3 layers of ordinary 2X4 studs, epoxied and painted. But small boat, not much compression to worry about, works just fine
jim

[Dan Irvine]

Boat: Archer inspired cutter LOD 32' LOA 43' about 20,000 lbs (ya I know) mast 6X8 box section 46' tall laminated hollow with 4" plug at bottom. As the mast has never been stood up and the builder I inherited this from installed the compression post, I need to cut the cabin top and insert a spacer in the opening to sit the mast step on, then through bolt the whole shebang. Overkill runs in my family so I was going to make a mold and cast the spacer and step in bronze but I would like to save the weight. I was leary of using wood for this spacer because of the compression factor but I will await your replies.