Adventure 40 Rig

As I write, we are closing in on revealing the Adventure 40 design, but before we get overwhelmed by all the cool details in the renderings, and the resulting discussion, Maxime and I think it’s important to finish writing about the specification that drove the design—we gotta know where we were heading to understand if we got there.

We have already covered:

• Hull
• Steering and rudder
• Keel draft and shape
• Keel construction

So that leaves the rig. Let’s dig in.

Overlap or Not?

The last time we went through the process with the boat that Erik de Jong designed, we ended up with a masthead sloop with a non-overlapping (blade) jib, which, in turn, allowed the chainplates to be placed outboard on the side of the hull, which:

1. Simplifies the engineering.
2. Reduces the compression on the rig, which allows for a slightly lighter section.
3. Gets rid of the pretty much inevitable leaks around inboard metal chainplates on a fibreglass boat.

However, there are also tradeoffs with that option:

1. When we get rid of overlap, the mast must get taller so as to have enough sail area.
2. Low-overlap “blade” type sails are:
   1. Harder to trim well.
   2. Reduce visibility to leeward.
   3. Don’t roller reef or furl well.
   4. To maintain decent trim as the wind speed changes, they must either be reefed or the jib sheet block continuously moved.
3. When bearing off to a reach, the crew must re-reeve the jib sheet outside the shrouds to get a decent set.

The Effect of Mast Height

The worst of these problems is the first. Increasing mast height has a surprisingly large negative effect on pitching moment, which, in turn, makes the boat slower and less comfortable upwind, whether sailing or motoring.

For example, Maxime and Pascal—they analyzed these issues before Pascal left the project—calculated that a meter of increased mast height on the Adventure 40 would be the same as putting 140 kg (308 lbs) on the bow.

Think about that for a moment. That’s like two medium-sized people up forward, which, on a boat this size, is really noticeable, and not in a good way.

Wait, it gets worse. Not only does pitching moment get worse as mast height goes up, but stability goes down as the boat becomes more tender, and so she must be reefed earlier, particularly since the centre of effort of the rig moves upward with mast height.

But if we just cut sail area willy nilly to deal with the problem, we end up with an under-canvassed slug that’s no fun to sail and ends up pushing her crew into motoring a lot.

So what to do?

The Carbon Option

One way to have a tall mast, decent stability, and low pitching moment is to fit a carbon mast. Not only is the material way lighter for a given strength and stiffness, but carbon also allows the mast designer to decrease the wall thickness in the higher parts of the mast, further moving down the centre of gravity.

No question, carbon masts are a whopping performance win and I’m a huge fan, having owned and sailed with one for 16 years.

That said, carbon is just plain wrong for the A40. Here’s why:

• A big jump in expense. I would guess around US$20,000, when compared to a production aluminum mast.
• Every carbon mast is in effect a custom mast, since good ones are laid up by hand, making consistent quality control much more difficult.
• In my experience, carbon mast builders will insist on using rod rigging—a lot of reasons, but one is that shroud termination is easier.

That’s all bad enough, but the bigger problem is the fragility of carbon masts. The A40 is an offshore cruising boat that will frequent places with, shall we say, rather agricultural boatyards, with probably no professional riggers in sight.

We just don’t want to be messing with a carbon rig where, for example, just giving it a good hard knock with a crane or dropping it off the sawhorses after unstepping could write it off.

Wait, it gets worse. The biggest drawback of carbon, that I have never seen mentioned anywhere but is still very real, is damage ambiguity:

A robustly-engineered aluminum mast that has experienced either of those assaults is generally either dented and/or broken, or fine. A five-minute inspection, will, in most cases, tell us if it needs replacing or not.

Not so carbon. For example, dropping it or a lightning strike can do damage that only a skilled technician, probably flown in from the mast builder and equipped with ultrasound scanning, can accurately assess.

And, worse still, that damage might be done when we were not present to see it happen, perhaps by a careless boatyard while moving our mast to a storage rack, so we might never know…until things end badly at sea.

And the last thing an A40 owner needs is to be dealing with rod rigging, where, once it’s on the ground, even a careless foot can bend it, requiring replacement that can only be done by a skilled technician using specialized equipment that is only available in big sailing centres.

The Adventure 40 is supposed to be easy to maintain, even in remote places, and carbon masts are anything but.

Back To Overlap

The other obvious way to keep the mast shorter but still have enough sail area is to increase jib overlap, but that only works well to about 120%. After that sails get hard to tack, don’t furl or reef well, and are generally a pain in the neck to deal with.

The other problem with overlapping headsails is that, to be efficient upwind, they need to be quite low cut, and that gets us back into many of the problems of blade jibs.

On the other hand, once we crack off on a reach, a high-cut sail becomes way more efficient, because the leech hooks less, and also reefs and furls way better. And, better yet, high-cut sails work way better than low-cut ones when poled out downwind.

The Best Answer

So is there a solution to most all of these problems? Yup, the cutter rig:

1. The jib topsail (yankee jib) is high cut, so a great reaching and running sail.
2. The staysail fills the gap under the jib topsail for efficiency upwind.
3. The combination of the staysail and modestly-overlapped jib topsail give us as much area as a substantially-overlapped single headsail, but without the problems.
4. A properly setup cutter is surprisingly fast, particularly in swell offshore.
5. A double-reefed mainsail and staysail with the jib topsail rolled up, makes a snug and efficient heavy-weather rig.
6. The staysail stay is the very best place to set a storm jib, and it’s much easier to make the change from a staysail than from an overlapping genoa.
7. If the stay is made roller furling, the staysail can be used partially rolled when heaved-to.

Of course, like anything around boats, the cutter rig has drawbacks:

Runners

The biggest of those is the requirement for running backstays to oppose the staysail stay loads and the need to tend them on every tack.

But that can be got around by simply moving the anchor points for the runners forward, so they can both stay on while the boat is going to windward. Our previous boat (McCurdy and Rhodes 56) is rigged that way and it works great. In my opinion, this option works better than having the anchor point way aft so that the runners can stay on at all times once the main is deeply reefed.

Ease of Tacking

The other issue that those new to cutters worry about is tacking two headsails, particularly if shorthanded, and getting the jib top through the smaller slot forward of the staysail. But once you know the trick, which is to leave the staysail sheeted on the old tack (backed) until the jib-top slides across and is sheeted home on the new side, all is good.

That said, there is no question that a cutter takes longer to tack than a sloop, but those who really worry about that can have the best of both worlds by making the staysail stay removable and setting a traditional overlapped genoa when inshore.

Light Air Sails

So is there no other situation where the sloop with an overlapping genoa bests a cutter?

Well, there used to be one: on a broad reach, when the staysail is no longer effective and has been rolled up on the cutter, the sloop with a big overlapping genoa will be able to show more area, although some of that is offset by the poor sheeting angle and shorter J measurement on the sloop.

But that was before the advent of large light-air sails—code sails, asymmetric spinnakers, gennakers, or whatever else we want to call them—made easy to use by being set on removable roller furlers, either top-down for spinnakers (or sock) or bottom-up for gennakers, which more than make up for lost reaching area on a cutter.

Bow Sprit

Wait, it gets better. The Adventure 40 will have a reasonable-length bowsprit for setting these sails, which makes them even more efficient, and has the added advantage that in settled weather the light-air sail can be left in place on its furler, ready for immediate and easy deployment.

There is also another benefit of the French team assuming while designing the A40 that performance-oriented owners will fit light-air reaching and downwind sails: They can get away with a bit less sail area and, therefore, a bit shorter mast than was previously required for decent performance off the wind.

That said, I would not like to see this carried to extremes. See Further Reading for more of my thoughts on optimal sail area for cruising boats.

Inboard Chainplates

All that’s pretty convincing, but it does leave us with a large fly in the ointment, which is that, on a cutter, we are going to need to move the chainplates inboard for decent pointing ability, with all the attendant drawbacks I listed at the beginning of the article.

That said, I’m sure the engineering can be dealt with. After all, most boats have inboard chainplates these days.

And Z-Spars, who Maxime and Pascal consulted on all of this, opined that the increased weight of section required by the greater compression generated by inboard chainplates was far less of a negative to pitching moment and sail carrying capacity than the higher mast necessitated by sheeting the largest jib inside the shrouds.

So that leaves us with the almost inevitable leaks resulting from the different physical characteristics of stainless steel and fibreglass.

To solve that, I’m hoping the boat can be built with composite chainplates, since they can be bonded in and so never leak, and also can be engineered and built to last pretty much forever, rather than the 20-year or so removal, inspection, and often replacement cycle that is required with stainless-steel chainplates.

Slot Rig?

Another option to get the chainplates out on the rail is the slot rig, that has become popular lately in France and is being used by Boréal on their new-generation boats, where the jib sheets run inside the upper shrouds (V1s).

Maxime and I did discuss this option briefly, but he pointed out that we could not get the overlap we need, particularly on a high-cut jib topsail (to keep the mast a reasonable height), without sweeping the spreaders a long way back, which is a bad idea on an offshore boat, particularly one that will make long offwind passages in the trades, where by far the best rig is main out on one side and jib topsail on the other.

Sailing hot angles with an asymmetric spinnaker may be fun for short periods but, trust me, it will get old after 20 days of constant tending on, say, a trade-winds trans-Atlantic with big breeze and swell, particularly with just two people aboard.

The other thing to realize about the slot rig is that the boats so equipped are generally not true cutters with high-clew jib topsails, but rather sloops with staysails that are used alone in heavy weather. So we lose many of the cutter benefits I listed above.

And the final and worst problem with the slot rig is that the jib sheet needs to be moved outside the upper shrouds every time we bear off, and back inside when we come on the wind—trust me, that will get old in a hurry.

Fractional Rig?

Z-Spars also suggested that the rig might benefit from moving the headstay down, say 50 cm (20 inches), from the head, perhaps in conjunction with a slight amount of spreader sweepback (no more than 10 degrees).

The benefits of this move to a slightly-fractional rig are compelling:

1. The mast can be tuned with a bit of prebend balanced against the spreaders and shrouds, which makes it more stable in a seaway.
2. Increasing backstay tension as the wind comes up bends the mast and flattens the main even more than it does on a masthead boat.
3. Doing this right can obviate the need for twin lower shrouds (D1s)—particularly on a boat with runners—which saves a lot of construction cost and aggravation as well as allowing the main to be let further out when sailing dead downwind. (If spreader sweepback is modest, it’s the aft lowers that tend to be the limiting factor.)
4. Moving the headstay down, but leaving the spinnaker halyard at the top of the mast, separates light air sails from the headstay, even more than a bowsprit alone would.

The drawbacks of fractional rigs is that they are more difficult to tune well, and require more skill to get the best out of, as well as a back stay adjuster (preferably hydraulic).

That said, given that the A40 will be a standard boat, it should be easy to provide a guide, much like the one available for our J/109, that will make her pretty easy to tune.

A lot of variables on fractional rigs, which the French team are still investigating before making a final call, probably in conjunction with whichever builder and mast manufacturer are selected.

Summary

Lots of detail here, so let’s take a look at what we ended up with for the Adventure 40 rig:

• Cutter rigged.
• Aluminum spars, preferably anodized rather than painted.
• High-cut roller-furling jib top (yankee) of no more than 20% overlap—that last part was from me, the great overlap hater.
• Inboard chainplates to allow the jib topsail to sheet properly.
• Running backstays, hopefully terminated at the deck well forward—I’m not sure Maxime is as big a fan of that idea as I am, and he’s the boss.
• Staysail that sheets inboard of shrouds and will only be used, as is typical with cutters, until the apparent wind gets to about 90° aft of the bow.
• Staysail will be hanked on as standard but owners can add roller furling if desired—we will have to figure out covers for the hanks to stop them chafing the jib topsail when tacking.
• Staysail stay will be removable as standard, for those owners who wish to sail the boat as a sloop, but still have the stay ready to go for a storm jib.
• Fixed bow sprit for light-air sails.
• Possibly a slightly-fractional rig with slightly-sweptback spreaders—this one is still being investigated and won’t be finalized for a while.

It’s interesting to note that the French team independently came down heavily in favour of the above solution in a technical paper they shared with me last November, and I’m a cutter fan based on well over 100,000 miles of sailing one inshore and offshore, so this solution is well supported by theory and experience.

Further Reading

I have not delved deeply into all the details behind every decision because I have already covered that stuff in past articles:

• Three articles on the benefits of the cutter rig and how to set one up right (lots of the benefits I just touched on above explained in more depth)
• Sloop, cutter, or solent, which is best?
• How much sail area is right?
• Carbon masts
• Why a lot of spreader sweepback is a bad idea
• More on composite chainplates

Comments

So what do you think? Please leave a comment. That said, please have at least a scan through the articles linked to above before doing so. A lot of questions and concerns are already covered there.