clothespin scarf

[Lee Winstone]

Hi folks, can anyone out there supply information on scarphing top section of solid douglas fir mast. I need to make a jig to cut clothespin scarf and as yet been unable to obtain any info. Anything on methods of cutting, aligning, gluing etc. would be most appreciated. thanks Lee.

[Ian McColgin]

Ahoy Lee,

I use hand tools, no jig.

On what's possibly a half-baked theory, I like the male end pointed up - something about if the glue line fails at the surface, water will still roll off. And I prefer a 12:1 bevel, though I helped a friend put in an 8:1 for a new spot near the spreaders of his main mast and it seems to work fine.

I've made the male end in two different ways. One uses a sort of follow it by eye guide of two hinged V's apexes tacked diametrically opposed at the top of the male end and ends held in place by a couple of vertical bits tacked to the outside of the opposing legs. I like a japanese pull saw for ripping as it starts the oblique cut easily and I can follow the upper and lower legs by eye.

I've also started with graduated cuts across the grain, careful to keep the sets parallel to each other, and then knocking the excess off with a slick.

Once some wood is removed, I plane it carefully to exact fit. It helps to make what I call a parallel guage for this - simply a cross member a bit longer than mast diameter and two bits normal to it. Rather like a squared up U. Even though as you get more to the pointy end one leg must rest well down the bevel than the other, and you have to tick it back and forth, it gives a fast easy way to measure that you're planing the two surfaces in sync.

Once the male end in made and just right, it can be used to mark the female end. It is most handy to cut out the female end before you fully round the spar - better yet before you even eight-side it, as you are then cutting a V into a nice square chunk. Even so, it's likely too large and the stick too big to do in a band saw and no circular blade will get to the inside apex. So again, the japanese pull saw.

Small aside - I imagine you know how to make an eight-siding gauge with either 5-7-5 or 7-10-7 porportions but in case not, you could use the paralleling guide or something similar with shorter legs. The distance between the two legs is divided into either 17 or 24 segments. I make these for the job. If the spar's greatest diameter is let us say 10" I's space the legs 10-5/8" (17 5/8" units) apart allowing for convenient scribe points (chisel finished nail end) to be placed 3-1/8" from each leg and leaving the spacing (5)(5/8) - (7)(/5/8) -(5)(5/8). The porportions remain constant even though the gauge the gauge is slanted across the work and the gauge will accomodate any taper you want to put in. Whatever's convenient.

Most of the trim inside the V will be done with a set of rasps and files. I use carbon paper, blue side facing the female surfaces, and gently tap it against the male side to mark the parts that need to come down.

Before gluing I plane off a bit of the feather end of the male part of the V, leaving a roughly 1/8" flat. This gives a nice guide hole to bore for what looks like a stopwater, which is structurally pointless here. It really gives the space needed for just the right fit.

Not counting making the blank for the new part of the spar, this process takes me about 6 hours, perhaps a little less.

G'luck

Ian

[Lee Winstone]

Hi Ian, thankyou for your comprehensive instructions on scarfing. I certainly have more confidence in tackling the project now. One thing I probably should have mentioned is that on my Tahiti Ketch the original main mast was keel stepped. The previous owner converted it to deck stepped with a galv pipe compression post to keel. There are no backstays, fixed or running (gaff rig). The aft shrouds are only about a foot back from heel of mast which concerns me. With jib, staysail and main hoisted in a following sea I am always worried that mast may fall forward with all that pressure due to the very slight angle of the rear shrouds. I have heard that if they are positioned any further aft they will interfere with the gaff when running. This is one of the reasons that I wish to scarf extra length onto mast to return it to original design of keel stepped mast. In your experience, do you think deck stepped mast without backstays is a reasonable rig for gaff? I still need to scarf mast as I wish to run cutter rig and need the extra length for jib and extended bowsprit. Your input would be greatly appreciated. Kind regards Lee.

[Ian McColgin]

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

[Ian McColgin]

Ahoy Lee,

Added thought on staying: Usually the aft lowers should come in about at the throat and, as you play with your rig with some professional help adding a staysail inside the jib, this is a grand spot for the staysail stay to land. These stays cannot bother the gaff with full sail, though they could limit your travel when reefed. On schooners where I confronted this problem, I didn't worry much as the leeward shrouds go slack anyway.

By the way, that gaff can get well out with sail twist and you'll want the spreaders hinged such that they can move fore and aft without stressing the base. The spreaders must not be overlong. Imagine a straight line chainplate to mast tang. If more than half the spreader is inboard of where that line intersects the spreader, the geometry is such that the shortest distance, which the rig will assume under tension, is the correct allignment. This, by the way, is also important for the dolphin striker if you have one, except that should be free to move athwartships.

Wait a minute. The bit about spreader length. That's how I learned and always assumed but I don't know that for an empiracle fact. Perhaps Brion would comment.

Any way, fear not pulling the lowers back a little if it makes you feel good.

If you're adding mast height, consider designing for a topsail. This is going to tower above the jib stay tang. Whether part of the single pole or seperate as a top mast, it should be light and disposable. Let it fail first. It helps the topmast or topmast section to build in a bit of foreward bow to be straightened when the topsail is set, thus giving nice leach tension.

G'luck

Ian

[osteoderm]

A friend and client of mine has a natty Tahiti ketch whose rig might bear description in this thread.
The main mast is of his own manufacture; hollow laminated (birdmouth) Douglas Fir, set in a burly galvanized tabernacle on deck. There is no topmast, but he carries a standing yard for a brailing forecourse. No spreaders, no runningbacks. The fore and aft lowers attach at the throat halyard crane. The aft-led uppers attach at the peak halyard/jibstay attachment point. The standing rigging is old-school: spliced galvanized with leathered softeyes over thumbs aloft and hardeyes to galvanized/painted turnbuckles alow.
He has similarly wondered aloud at the prospect of an extended bowsprit and extended polemast/topmast to set a flying jib/jibtop/masthead gennie. However, as it stands, the mast and rigging have seen a few thousand offshore miles in the North Atlantic and Carib without incident or complaint.