|Not much riggin' up there!|
Free standing masts have been around a long time.
Bullet points in favor:
- Simple - Easy to rig and maintain.
- Inexpensive - No shrouds, stays, chainplates, spreaders, turnbuckles or swages... reduced shackles and tangs.
- Works well in a very broad range of conditions - Not just a light weather rig.
- Low windage - Rigging adds drag.
- Quiet in a blow - No shrieking rigging.
- May be raised and lowered with relative ease - Lots less weight and stuff to deal with.
- Spill gusts and ease their impact - Willow vs. oak.
- Impervious to jibes - You don't clobber the shrouds with the boom, possibly bringing the whole shebang down.
- Have few parts to fail - Reduces the odds of failure.
- Don't generate high stresses - Doesn't generate the crane effect, which torques the hull.
- May be temporarily stayed with standing or running stays and shrouds - Can't temporarily unstay a stayed rig.
Disadvantages don't warrant bullet points. Not as fast to windward. Period.
The usual response I hear is, "Well yes, but carbon fiber masts are expensive!" Carbon WHAT? Come on... the Chinese have been sailing unstayed rigs for millennia made from that exotic material, wood. You know... that stuff that grows on trees.
All in all, for a KISS boat, free standing rigs deserve a good, close look.
|SLACKTIDE's forward tabernacle before installation... |
Hinge pin goes thwartships, high and aft.
Note tripod formed by box and struts.
Adequate, but struts could've landed yet further forward for greater support.
And, as long as you've a free standing mast, you may as well mount it in a tabernacle.
If you look it up, wade down the list of meanings until you hit the nautical one. From my Kindle OED:
A partly open socket or double post on a sailing boat's deck into which a mast is fixed, with a pivot near the top so that the mast can be lowered to pass under bridges.
Or, I might add, to perform maintenance, add masthead toys, sit out a really big blow or 'borrow' the mast for some other purpose (sea anchor, skids, lever, etc.).
Basically, the tabernacle forms a box, open on one side. A pin, near the top, passes through a hinge, strongly mounted to the mast. One of many stop mechanisms fixes the foot of the mast in place. When the stop is released, you can lower the mast.
A free standing mast needs a certain amount of bury, that is, a percentage of the distance from hinge (or partners) to footstop, divided by overall mast length. The range is a minimum of 10% to an ample 15%. More doesn't hurt, and gives better leverage for raising/lowering. With enough leverage and a counter-weight butt, this can be a one handed job.
Of course, the tabernacle needs to be adequately supported... I still haven't found a rule-of-thumb for this, but, if we're gonna go hell for stout, this is the place! The more support we can bring to bear, the merrier.
The tabernacle must deliver adequate re-enforcement at the hinge, as well as below. I like to bolt to bulkheads, and the more the merrier. Solid, triangulated struts can be used, if not enough bulkhead is available, splayed to the sides and either fore or aft to form a tripod (or double up struts to forma a quintapod?). The less free standing tabernacle, the happier I am.
Timber tabernacle posts are inexpensive, simple and can also be more freestanding, in their own right, than simple plate. Their bury (I think) can be calculated as if it were a solid mast - from masthead to foot of tabernacle, with the uppermost structural support as the 'hinge'. They can be minimally secured at foot and 'partners' (where they pass through a deck), but I'm always happiest when they're bolted to along a bulkhead.
I like the total cross section of tabernacle timbers to be greater than that of the mast by a goodly margin. I also like to tie them together with a back plate to help equalize mast stress-loads between the timbers. On the s'brd tack, say, the port post would bear all the stress, if not bound to the s'brd post. In that case, both would share the load on either tack. A removable front-plate, fixed once the mast is erect, further strengthens the whole shebang.
Welded metal tabernacles have some advantages. They're not as bulky, clearing the view. Struts are very strong, reducing the need for post bury along a bulkhead. A deck plate at the bottom gives landing to the struts and a broad footprint for leverage and spreading out psi from stress loading. They're very handy where little or no bulkhead exists, and you don't want the mast or posts intruding below-decks. Still, don't get crazy. If you can't arrange a solid tabernacle, reconsider whether it should be stayed, after all.
Anke and I, with no special gear, usually dry out for raising. We use one mast as a crane for the other, and raise as high as we can. One of us (the short one) will be out on the beach with a line to the masthead, while the other, taller and dumber, strains and puffs it the last of the way up. As Tall and Dumb ages, I may add counter-weights or mechanical advantage. Lowering is just the reverse.
Bonus free standing mast story:
One fine autumn day, we were sculling LUNA across Salisbury Sound in a flat calm. The sound is open to the Gulf of Alaska at its northwest end, and tapers down to narrows in the south. Low mountains flank it on three sides, high mountains to the north.
We were making for Neva Strait, the strong-current passage near the south end. We were hustling to catch a fair current... miss it and we'd have to wait for fair wind or the next tide.
Anke was below, making lunch. I had all sail set to catch the occaisional zephyr. We'd made good time, and now, approaching Neva's entrance, we had plenty to spare.
I heard a rumble behind me. I glanced over my shoulder, expecting maybe one of the big ferries? What I saw was water being blown to spray by a wind bearing down on us. YIKES! Willawaw!!
I threw the helm over, shouting "Hang ON" to Anke. The boat had barely begun to turn (not much steerageway at a knot and a half), when a furious burst of wind jumped us.
We were still in line with the assault as both sails caught and filled. I felt LUNA's stern rise, the whole aft end levering from the water. With a splintery CRA-ACK, the foremast gave, breaking in two, just above the hinge!
"HOLY MOTHER OF FREAKING PEARL!! We've been dismasted!", I bleated, the wheels of my brain burning rubber. Rounding quickly under the full main, I steered off, a bit, to let the foremast fall alongside us (don't want em' falling on deck or self!), dragging from its haulyard and sheets.
After that first gust (how many knots of wind was that? No sea state to judge it by!), the wind settled down to a bit shy of 20 knots. We dropped the main and tightened the mizzen, holding the bow into the wind and slowing drift.
[LUNA is a cat-schooner with what we referred to as fores'l, main and mizzen. The latter is a little 'dandy', a.k.a. 'spanker' mounted on the stern, but those terms just don't fly in Alaska, nor with Anke, for that matter.]
A fisher friend had been approaching (Neva's a busy place) when the mast went down, and asked if he could help. We asked him to stand by until we got an anchor down. Backing the main, we were able to crab our way to the side, where - fortunately - the bottom is sandy. We dropped the hook, checked for holding, then waved him on, gulped our lunch and came up with a plan.
First, we hauled the broken butt aboard. Released the haulyard of the still set fores'l and clawed the battens uphill and onto the deck, panel by panel, untying their parrels as they came aboard .Once the lug was aboard and detached, we bundled the sail on deck and brought the upper end of the mast aboard.
[Batten parrels are short, standing lines that tie to the forward end of a batten, pass aft around the mast and retie to the same batten; they keep the sail in close to the mast and can be climbed like ratlines.]
Next, we removed the broken stub from the tabernacle, and detached its hinge hardware. This is just a large metal strap, bent over double, then drilled and counter-sunk for heavy screws. The whole shebang is served with nylon line to back up the screws and pad the mast in its tabernacle. We transferred it to the mast remnant, the correct distance up to provide bury, screwing and serving in place.
We set it across the tabernacle and reinserted the hinge pin, then raised it. This was a little tricky and fail-dangerous. We're bouncing around at anchor instead of our usual dry-out. Anke can't help at all, except to counter-weight the base, and pin the foot once it's up. I'm straining myself purple, alone, to raise the (mercifully) shortened mast without letting it slew off to one side (a 24 foot lever prying at our tabernacle!). Lucky I din't bust sumpin'.
But we got it up. Next trick-in-a-row was to re-rig the sail bundle (re-attach haulyard, lead through lazyjacks and fix them in position, re-tie batten parrels. Reattach the sheets and done!
Finally, we look up and around... HEY! Tides still fair... this whole mess only took an hour and a half! What're we waiting for? Up anchor and sails, wing 'n' wong in a fair breeze, one panel reefed on the shortened foremast.
Try that with your fancy, high-tech, marconi, witch-to-weather rig!
|Free standing freedom|
There's a little preamble to this story. We had recently replaced the old, trolling pole foremast, which had become pocked with exterior soft spots.
A friend had offered that we take a tree off his property (rather than the standing dead we usually harvest from the Tongass). It was a rushed search among young, living trees... we prefer trees that have gotten a late start in shaded understory. They grow slowly and densely ringed.
We found a nice, straight one, but the grain turned out to be wide. I've heard 9+ annular rings to the inch is optimal... this was about 5. A hidden flaw pushed us a couple of yards up the butt, leaving it on the thin side. Finally, it had only seasoned for a couple of months. Green (wet) wood is much weaker than dry wood, and spruce seems to have a wider difference than most. It takes about a year 'on the hoof' to get a standing mast dry.
So. Three strikes against the foremast. The full value main - to windward, having less bury and partially blanketing the fores'l - stood firm.
Conclusion? We're still perfectly happy with free standing masts, but are holding ourselves to their rules-of-thumb!