Arne wrote:
Flat or cambered for deep sea voyaging?
Time for a revival of this old topic.
Nowadays, it doesn’t seem to be controversial to put camber in junksails meant for coastal cruising. However, from time to time the question about flat versus cambered sails still appears when the matter of ocean travelling is up. The boat of the month is currently Chris Gamble’s 34’ schooner. He chose to go for flat sails and seems to be happy with that.
Now, today, Asmat Downey reports that he has returned from a big Atlantic tour in his Wylo 32, Branwen, schooner-rigged with cambered panel sails.
For the sake of science, would you Asmat be so kind and answer these two questions (apart from writing a good story for the Magazine)?
1. Did you during the voyages have any problems which were specifically connected to having camber in the sails?
2. If you were to repeat your voyage with the same boat, and knowing what you know now, would you make the new sails flat or with camber in them?
Anyway, welcome back!
Arne
Let's be clear about this, Arne. Deep sea voyaging per se is not the thing that determines whether camber is a good thing or not. It's where on those deep seas that you are voyaging, and whether you have an engine.
Chris Gamble was on a simple mission, to get from Europe to NZ. This is a voyage where downwind sailing is going to predominate, with trades except for the first bit down to Spain, Panama to Galapagos and Tonga to NZ. He had a good seagoing boat with an engine. His decision to use flat sails was the right one. But now, consider an engineless junk doing the same trip. Considerable windward ability is needed to get through the passes on the leeward side of the atolls against the outflow, for example. Considerable windward ability plus a lot of patience is needed to sail from Panama to Galapagos without an engine. And then there's the ITCZ. By its very nature, it's easy to sail into the middle, but hard to sail out of the other side. An engineless junk will need full camber; a junk with an engine will do better to motor-sail through the fickle, light or non-existent headwinds, whether the sails are cambered or not. A small efficient diesel plus a large tank of fuel is a key component of a stress-free cruising boat.
Now consider my final two ocean voyages: singlehanded from NZ to Alaska, and from Canada to NZ. The first with a fantail-pattern sail - fanned planform, very high peaked yard, straight battens, some sewn-in camber particularly in the lower panels; the second with the sail salvaged from my failed attempt at a wingsail - low peaked yard, battens with a single hinge, flat cut sail.
The first voyage is one in which windward work predominates. Indeed, many American sailors view it with such trepidation that they will not attempt it in their bermudan-rigged boats. I had no difficulties with windward ability, but it was hard physical work. Why? Because of the high peaked yard and the associated high loadings in the YHP and LHP. Not as hard as sailing a bermudan-rigged boat on the same passage would have been, but harder work than sailing a junk rigged boat needs to be. I build my sails strongly, and this sail was made from Haywards cloth, so breakdown of the cloth around the throat area did not happen, as it did in Fantail's first sail. This was due largely to the cyclical diagonal loadings that occur in the throat area of a high peaked sail - not an issue in a lightly used coastal cruising boat, but needs to be taken seriously and guarded against in an ocean cruiser, with plenty of reinforcing patches.
The second voyage also contains plenty of windward work, but is more of a mixed bag. Some camber is certainly desirable, though. The physical work was very much less demanding, with the low peaked yard. This matters a lot, with an ageing singlehanded crew. I made the voyage quite fast, because I was able to keep up with sail changes without exhausting myself. I had been challenged to get to NZ in time for Annie's 60th birthday party, and only missed by a week, due to strong winds and washing machine seas off Tonga that made me need a rest, not through lack of windward ability.
Do you see, Arne? That last ounce of windward ability, so important in racing and for having fun while sailing around Stavanger Fjord, is only occasionally of very great value in ocean cruising, and can be substituted with a turn of the engine start key. 24/7 ease of sailing matters more. A small crew has limited stamina, and an exhausted crew makes bad decisions. A docile rig with little camber is better for motor-sailing, too, and that matters more when cruising in tidal conditions than it does in Stavanger Fjord.
It was the experiences of those two voyages that were - not a road to Damascus conversion, exactly, but more a crystallisation of my thoughts, when it came to deciding what kind of rig to put on Weaverbird. The similarities with Tystie's present rig show that there is a clear line of development, yet they are not all that similar when you look closely.
To list the main points of Weaverbird's sail design:
- 45˚ yard angle - less than H&M and Arne's planforms, more than Van Loan's (from memory) and a yard that is shorter than the battens.
- parallelogram lower panels, just like all JR planforms except the totally fanned ones.
- Longer luff lengths on the upper panels, so that the fanning effect is much less distinct a feature than on H&M and Arne's planforms, but is still there.
- Two hinges in all the battens, but with the angle of articulation reducing from 20˚ to 10˚ in the top batten (for reliability of articulation).
- A minimal amount of barrel-cut camber in the lower panels - 45mm of round, in a chord of 3360mm. It's hard to get a deep camber with hinges alone, and this addition of a little camber in the panels increases camber from 6% to 9%.
Would I put Weaverbird's rig on an ocean cruising boat? Yes, absolutely. In two seasons, of four full-time months each and a total of 3300 miles, it's proved sound and reliable in all kinds of conditions. Just as much, and perhaps even more to the point for cruising is that it's as effortless and thought free a manner of sailing as is possible. Arne's postings on his rigs are often about how you need to do "thus" and "thus" to the YHP and THP and LHP and HKP to get them to set well. My YHP is redundant under full sail, and only lightly taken in when deeply reefed. My LHP (no THP necessary) can be easily taken in with one hand whilst steering with the other. The sail sets well, with little tweaking and conscious thought on my part. Why? Mostly because of the yard angle and its shorter length, and the particular shape of the upper panels, and not because of depth of camber, or the way in which camber is added. This is what truly matters when ocean cruising. On a dark moonless squally night, being able to reefing and unreef, and knowing that your sail is well set even though you can't actually see it, is worth more than that last ounce of windward ability.