TriloBoat Talk: Rigged for Success: LOM/Ljungstrom + Quick-Rig Booms

MUSTELID's LOM Main and Ljungstrom Foresail

Live life as if everything is rigged in your favor.

-- Rumi

Rigged for Success:
LOM/Ljungstrom + Quick-Rig Booms

I'd like to share a suite of ideas toward a family of lesser known rigs for smaller vessels that I think show a great deal of promise. Part historical, part convergent evolution, part innovation, the result is a simple but versatile, robust rig that can be DIYed at low cost.

Leg o' Mutton (LOM) Sails

This tasty moniker simply means a triangular sail. They're commonly used for headsails (jibs, staysails, etc.), mains (often called Bermudan sails) and drivers (small sails set far aft).

Ljungstrom Rig (2 x LOM)

Ljungstrom Rig uses a pair of LOMs, joined along their luffs and set on a free-standing, rotating mast. No booms were used to avoid troublesome impacts with crew.

This configuration works similar to twin head sails off the wind. From a beam reach on up, the sails are doubled over to one side and sheeted as one.

Pros:

Light, inexpensive spares and gear.
Quick set/reef, roller un/furling via the mast.
Sailing off-wind, one side can be jibed for 'instant' 50% reef.
Sail area aloft catches higher, upper wind-flows.
Low Center of Effort (CE).
Twin sails tend to center down the wind.
Potential for hands-free operation.
Sail steering is straightforward (haul to the side you wish to sail).
UV resistant fabric along luff and foot eliminate sail covers.
Boomstrike is eliminated.

Cons:

Lack of a boom makes spreading sail difficult (especially on narrow hulls).
No clew outhaul or vang options.

One more con I'll mention... compared to stayed, headsail LOM rigs, there is no gain from slot effect. I don't list it, however, as stayed vs. unstayed rigs generate their own lengthy pro/con lists which don't add much to this discussion.

Adding a Boom

The addition of a boom set under a loose-footed LOM allows spreading, a clew out-haul and vang, addressing the main cons.

Interestingly, this approach was taken by both the Sea Pearl 21 (adventurously sailed by Stephen and Ginny Ladd, among others), and is marketed as Holopuni Quick-Rig (by Holopuni Canoes). Convergent evolution?

Both of these designs lead their clew outhauls via track along the top of the boom and sheets to the end of the boom. When the sail is reefed, the upward pull of the clew at mid-boom is resisted by the end positioned on the mast and the downward pull of the sheets at boom's end.

As a sail's belly is blown full, pulling the clew strongly toward the tack, the boom resists in compression. If it is deflected from straight by the perpendicular pull of the clew between mast and sheet lands, that strength plummets. Usual solution? A heavy boom or one made with exotic materials.

Hmm.

What if we oppose sheet and clew tensions by having them meet at the same point? They cancel out, unloading the mid-boom! The clew outhaul - led to boom's end, then turned back toward the mast to the clew completes the picture. A rope grommet - travelling along the boom - is the perfect attachment point... simple, cheap and DIY.

Principle parts of the rigging...
This platform and 'collar' are primitive but functional

How We Go About It

Rotating Mast and Gear

In our small-ish boats, we went with a thumb-sized dowel protruding from the rounded bottom of the mast. This is inserted into a hole in its step - a fixed plate of thick HMD (cutting board plastic). This secures the foot but it allows it to rotate with very little friction. The upper partners are simply a loose-fit, fixed square around the mast. The distance between step and partners should be between 10% (minimum) and 15+% (healthy) of the mast's overall length for adequate cantilever.

A gate can swivel open to free one face for raising/lowering or close and lock to contain it. 'Box' sides at the step hold the foot in place for lowering. A pin led through one side and into a corresponding hole in the lower mast prevents rotation against high winds or rock and roll.

Each boom requires an arrangement that fixes their height above the partners, yet allows the mast to rotate independently.

Our solution is a platform affixed to the mast with a collar from boom's mast end, around the mast, set above the platform... the collar is not so loose as to slip below the platform, but not so tight as to grip the mast.

Booms

Booms can be quite light, subject to sea trials.

Each has a rope grommet loosely fit around them (it shouldn't bind when pulled at a flat angle).

We fix a pinch cleat for the clew outhaul at the boom's mast end, pinch horn down (10deg) toward the distal end. This allows the line to ride over the non-pinch horn (up and toward the mast), under control hands-free as it pays out while furling.

A ring seized to the distal end of the boom turns the outhaul back toward the grommet.

The outhaul leads from its cleat, through the grommet (helps control a slack outhaul) to the turning ring, and back to the grommet. We fix it to the grommet's upper side, allowing a tail which is tied to the clew. We prefer little play between clew and grommet.

The sheet is fixed to the grommet's lower side and led to deck level. A turning device (multiple or travelling for an improved lead?) leads it toward a clear, handy to the crew. We prefer enough friction on the cleat to hold in steady wind but ease in heavy gusts... no lock hitch.

Sails

We used light nylon fabric to build flat-cut sails. These are responsive, and furl neatly around the slightly tapered masts. They are stretchy enough to take on some belly (camber) when full of wind.

Downside is that camber can't be flattened easily in high winds. But reefing is so easy, we can reduce power that way.

For 2xLOMs we screwed the webbed luffs to the mast, but are now considering a pocket for easier installation and removal. Others have found that a simple lanyard from tack to mast is sufficient for furling.

Handling the Ljungstrom

We set the Ljungstrom sail well forward, where it can pull us bow down the wind.

We don't typically vang our sails to flatten them. Instead, we vary the sheet leads and/or reef a little more than we might. This avoids extra gear, handling and the heavier booms required. Personal call, however.

Furled Set Up

When furled, the sail is snugly wrapped around the mast. The boom(s), if any, are vertical. Sheets are left slack and hanging. One clew outhaul is marline-hitched once or twice along the mast, securing all the bits, then made fast at its pinch cleat (low).

Setting Sail

Unhitch the outhaul, then refasten to its cleat. Uncoil sheets and lead aft to their cleats. Both outhaul and sheets will go slack as the sail is unrolled. Unpin mast if locked.

Depending on wind, you might wish to round up. For downwind departures, you may have to work in stages, trimming sheets as you go.

Unroll the sail by rotating the mast (we prefer 'righty-tighty; lefty-loosey' as standard... we do this by hand, but various rope windings are possible).

Once unfurled as far as desired, haul the outhaul(s) for the curve you wish, then make fast. Trim sheets and fall off to heading. Backing sail is easy and effective. If you wish to open the sails, do so.

On the Wind

Here the sails are overlapped and are sheeted as one (outer one generally the focus of our attention). They handle pretty much as any boomed LOM.

Off the Wind

Sailing off the wind, the sail is typically balanced like a delta kite. All things being equal, it want s to hold the bow centered downwind. More belly is often a good trade-off against more area.

To steer using sail, haul the sheet on the side toward which you wish to turn (easy, now!). This shortens its force vector and directs it to that side. The opposite sail, now relatively stronger and with a longer lever-arm, works to rotate the hull that-away. Like the reins of a horse!

In a heavy gust, you have a 50% reef at hand. You can jibe one sail (lapping one over the other) or let it fly (this can be harder to retrieve... get a wide angle). But if this comes up, consider roller reefing ASAP. Consider that, in high winds, you don't have to set them wing and wing... they sail well as one.

Odd Situations

If a sudden squall has invited letting both sails fly (they're trailing down the wind from the bow), calmly roller reef until you can bring them in and under control.

If such a situation has reversed their usual sides, don't panic... just hand the sheets around the mast, or refasten them for a fair lead and carry on. The sails won't care.

The whole mast, sails and all, can be furled, hitched up and let over as a sea-anchor.

All in All

We found these LOM/Ljungstrom + Quick-Rig Booms to be simple, cheap, versatile and powerful. Each piece is DIY-able from scavenged materials. Nothing about them couldn't be made in the field, at a pinch.

The lightness of the spars is a BIG advantage, especially as we age. The masts should be manageable for as long as we're likely to be able to row.

In researching the history of the rig, the few who have used it are soberly impressed by its virtues. It is not the fastest rig out there, but its no slouch, and pays its way with easy handling and quick reefing.

I'm hoping to see more of these on the water in the coming years!