Ahoy Lee,
You may want to either get a professional opinion from Brion or a local pro, or perhaps dare to open a copy of Skene's Elements of Yacht Design to check some mast scantlings. A keel stepped mast can be built more lightly than deck stepped and thus you'll want to consider if the mast is too slight in it's deck stepped configuration. Probably it's ok as it was most likely over-built anyway but worth the check.
If the mast is robust enough to be deck stepped you have some choises. I think you want running backstays in any case. They help tension the head stay and will take some of the wobble out of the masthead in a jumpy sea, both on and off the wind. The sail will help keep the mast up when on the wind but especially in a sea, there's a lot of motion at the truck if you've only shrouds. And running backs will ameliorate downwind dread.
Pros and cons of each. Keel stepped is stronger and stiffer as the mast is held at both butt and partners. This may or may not be a good thing.
Keel stepped has a somewhat greater chance of surviving a rigging failure, especially, depending on the stay that fails, you can alter course fast enough to take the strain off. But you really should be inspecting the rig often enough that you note problems before they are breakage. Most rigging failures that actually happen are preventable.
Rigging failures that happen far off-shore on well-maintained boats happen in such dire circumstances that I think there's little difference deck or keel stepped. If you have a catastrophic roll-over that's taking your rig apart anyway, perhaps it's better to not have such a big hole in the coachroof or deck. But then maybe the tabernacle would make a hole. Who knows? If you've lost the rig, is it easier to jury rig with the option of keel stepping whatever you make. And if so, what's to prevent you from removing whatever may be left of the tabernacle and reopening the partners?
As you may be guessing, I don't hold much with simply deck stepped for a cruising boat. To get the full virtue of deck stepping, a tabernacle of sufficient height that you can step and strike the mast floating in a calm is worth the work especially if your cruising involves low bridges, long canal trips like across Europe, or maintenance .
Deck-stepping should eliminate any overhead leaks at the partners.
With today's rigging, there is no reason deck-stepped cannot be as ultimatly seaworthy in the long run. So, your decision, if not forced by the mast's scantlings, is just that, a choise. All my own boats, most obviously my current 6 ton catboat, wewre keel stepped. But my previous boat, Granuaile, 20 ton 55 foot Marco Polo three masted schooner, was planned to convert to tabernacle-deck stepping in a planned major rebuild, sadly thwarted by her loss dragging her mooring into the breakwater in a peculiarly vitriolic northeaster. Marmalade, my catboat, has a hugely heavy solid stick and even were it hollow, an essentially unstayed mast needs deep planting.
I think that with the weight of a solid spar, if that's what you have, and gaff rig, I'd do keel stepped because that's probably too heavy to handle from a tabernacle anyway and keel stepped is cleaner from an engineering point of view and more elegant emotionally.
I take it this is a solid spar but either way, you'll likely be adding a both ends if you go keel stepped and just the top if staying deck stepped as you probably can and should carry a bit more taper aloft. I can't really address this and it's a most important point to get right so again, Brion or someone like him or Skene's if you're brave. Key thing is to design the whole mast as it should be and then figure out how much to add at one or both ends.
G'luck
Ian
|