Do you have doubts about your boat’s mast? We will help you

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“Aluminum or carbon shaft?” We were talking about this for a good half hour just back from vacation in the newsroom.“Carbon all the life, for stiffness and performance,” said Luca, our editor!“Mah, aluminum costs less though,” replied Eugenio, his deputy (who is from Liguria).

Tree – Better this way or that way?

We realized, however, that the question is being asked by many people. And it’s not just bar talk. Because to each technical solution, to each form, to any design parameter correspond very specific peculiar characteristics.

In this article we answer three of the cruise passenger’s doubts about the tree. Doubts that come up when he has to choose among the various options in the market.


Doubt no. 1 – Crosses in line or quartered?

The trend for years now has been to simplify maneuvers. And in this regard, so-called quartered spreaders (angled toward the stern) have undoubtedly brought great advantages. First of which is avoiding the use of flying shrouds and in some cases even the backstay (this is the case with the new Sun Odyssey 350, the Solaris 40 ST and theOceanis 37.1).

Tree - 1
Tree. Crosses in line or quartered?

Less maneuvering to do in the tack, easier genoa passage over the other tack, gybes in strong winds no longer heart-pounding. The wheelhouses also move aft, gaining more space and scope for larger deckhouses and consequently even more XXL volume below deck.

The operation of this configuration is both simple and ingenious. The high shrouds allow the spreaders to pull the head towards the stern and push the central part of the mast towards the bow, while the diagonals support it towards the stern and prevent it from reversing its curvature. This creates a balance of forces that stabilizes the “pole” and keeps it from pumping on the wave.

However, there are trade-offs: first, the profile must be over-dimensioned and consequently heavier than what could be adopted for an in-line spreader mast equipped with steering wheels and stay. In the flush stern, you also cannot let go of the mainsail much.

This seems like a minor detail, but on an Atlantic crossing on the trade wind route this is a not insignificant limitation. But perhaps the most critical aspect lies in the difficulty of adjusting the rigging.

In fact, the mast needs a very pronounced pre-bend (the longitudinal curvature), with the head going toward the stern and the middle part sticking out toward the bow. With this set-up, when you cock the backstay to decrease the catenary, the masthead tends to sag and as a result the high shrouds go bando and the forestay instead of tensioning is likely to let go.

Ideally, the mast should be fitted with a bowstring tensioner, as is customary on the more pulled racing boats. Which is unthinkable on a boat intended for cruising. In short, one must pay attention to adjustments and consider that this type of configuration is less simple in use than one thinks.


Doubt no. 2 – Shaft on deck or through?

The major differences between a mast that rests on the deck and one on the bottom of the hull (usually on a wooden heel integrated with the coping) lie in the adjustment of the profile and its sizing.

Because it is constrained at two points (coaming and foot) rather than on one, like the one resting on the deck, the through-shaft allows easier adjustment of curvature (pre-bend) and tilt on the longitudinal axis (rake). It can also be smaller in cross section and therefore lighter and thinner, resulting in less wind resistance and a smaller shadow area on the mainsail.

In terms of safety, if the deck foot coupling and the internal strut that distributes the compressive load are well designed and fabricated, there is no reason to prefer one over the other.

Paradoxically, in the event of a dismasting, the mast resting on deck produces less damage than a through mast. The latter, moreover, is subject to the passage of water that penetrates inside the profile and ends up in the bilge. But for this problem there are now several effective solutions to block water ingress.


Doubt no. 3 – Carbon or aluminum shaft?

If the aluminum shaft has not yet been supplanted by the carbon one, it is only because of economics. As much as black fiber is less expensive today than it used to be, the price gap is in fact still quite high.

tree
Carbon shaft or aluminum shaft?

While an aluminum profile originates from a drawing die and thus has quick and easy reproducibility, a carbon profile is made manually. And this contributes to raising its production costs.

Its construction is far more refined; in fact, strength can be better calibrated by applying more material (i.e., fiber reinforcements) where it is needed and less where loads are less.

And this allows, in addition to a better weight/stiffness ratio, a smoother curvature. But the advantages that can steer the choice in favor of carbon are not only about performance, but also about comfort when sailing. Saving 30-40 % of the weight of the profile allows the center of gravity to be lowered to the benefit of rolling, pitching, and not least skidding.

During a test we carried out on twin 12-meter boats rigged with different masts, the first in carbon and the second in aluminum, we were able to verify that that 80-kg difference in profile determines a quite different reaction to heeling: with 18 knots of real wind, on the boat rigged with an aluminum mast we had to give it a coat of reefing, while the other was still sailing with full canvas and mainsail a bit off.

Equally pronounced was the difference in behavior both upwind and downwind in rough seas: the boat equipped with the carbon mast passes the wave more smoothly and rolls less. Regarding the problem of carbon’s high attractiveness of lightning, the experience of the now thousands of boats around the world suggests that we should suspend judgment. This was also said at the time of the first aluminum shafts.


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