Sailing an AeroRig

[Hayden Watson]

Over the years, I have seen several threads reporting the sighting of boats with a very strange unstayed, rotating mast that has rigid fixed booms that extend forward and aft from the mast. The rig is the AeroRig and have all sails connected to and rotating with the mast and the only control line to the hull is the main sheet. On these threads there has been much conjecture and hypothesis on how they work but no firsthand experience. I recently was able to crew on an 85’ steel center boarder on 70-mile transit in wind ranging from 0 to 25 knots so I thought I would provide some first-hand insight into the rig.

On these rigs the main is fairly conventional except for the boom being a solid extension of the mast and rotating with it. The jib on the other hand is not attached to the hull at all. The Jib is self-tacking and attached to the forward end of the boom extending forward from the mast and sheeted to a curved track that is attached to the foreboom just ahead of the mast.

The boat is a custom 85’ steel center board monohull with 7’ draft with board up and 14’ with board down. Displacement is 39 long ton. The air draft is over 85’ and the sails are new this year with the main modified to a Fathead full battened main with a lot of roach. This added 20% more sail area over the previous main to improve light air performance.

My first impression is that this is the easiest to sail boat I have ever been on. Of course the fact that all winches are hydraulic helped in that matter but even when using the winches manually there was very little work to do once the main was up. Trimming consists of setting the draft of the main with the outhaul and the draft of the jib with the jib sheet and the twist with a down-hauler. Once that was done you trim or ease the main sheet to point the whole rig at the wind angle that you are set up for. Main sheet loads are so light that most times the 2-part sheet could be pulled in most of the way by hand. The winch was only required to get the boom to centerline for close hauled course.

 

[Hayden Watson]

Here is another photo of the working side of the mast. The aft winch is for main outhaul, 1st, 2nd, 3rd reef, main halyard, masthead haulyard (for going aloft) and port & starboard running back stays (which were just recently added due to the fathead main requiring the removal of the back stay from end of boom to masthead.) The forward winch is for jib halyard, jib sheet roller furler and down-hauler.
the main boom is about 3' to 4' wide if you include the SS tubing extensions on both side. The fore-boom is wide enough that the owner walked out to the furler while sailing after a rain storm when the tell-tails got stuck to the sail. We were sailing close-hauled so the boom was over the deck and the jib close enough to CL so that he could use it for balance.

 

[Hayden Watson]

Some of the strange aspects of the rig is that it is impossible to get true wind from the masthead wind instrument. all wind is apparent because the transducer rotates with the main and sometimes is more than 130º off the centerline access.

The other is that he cannot have a tri-color mast-head nav light for the same reason. Instead, He needs to use Rule 25. (c) A sailing vessel underway may, in addition to the lights prescribed in Rule 25(a) (bow bi-color), exhibit at or near the top of the mast, where they can best be seen, two all-round lights in a vertical line, the upper being red and the lower green.

To do this, there are three sets of red over green lights mounted in the mast just above the jib head at 120º spacing so that no mater which way the mast is pointed it has all-around red over green.

 

[capta]

Are you going to get around to sharing how well it performed against the equivalent traditional rig?

 

[JohnShannon]

Its a cool idea I think they call it a Balaton rig? The knock is apparently weight although conceptually it is a freestanding mast ( those have been done) with a boom (those have been done) and the only extra bit is the foreboom?

 

[Hayden Watson]

Are you going to get around to sharing how well it performed against the equivalent traditional rig?

Working my way down to that but was waiting for some participation.
Given that the unloaded displacement is is over 87,000 lbs. and that is is equipped for cruising, (just got back from south pacific, I was surprised at how well it did in light air, at least over 5 knots but more about that later. I would sail in 5 knots and make 2.5 - 3 knots close hauled which I would consider to be pretty good and fantastic for such a heavy boat. At 7 knots it felt well powered and over 15 really benefited from the first reef although we did sail for a while in 21 before reefing because the owner was asleep.

 

[Hayden Watson]

When beating to windward, we set the AP to steer a wind apparent angle of 32º with the sails trimmed tight. This allowed us to tack in 90º or less and upwind with two reefs in 15-20 we were making over 7 knots. We might have done better with only a single reef but the reef strop broke earlier due to rotten threads and it was a choice between full fathead or double reef. taking on a beat consists of pressing the "turn" button on the AP and going to the mast to slack one running back and snug the other. (two turns on the winch and hold the button until it slips.) The owner said that this was a "huge" increase in the work to tack because before the fathead he never left the cockpit or did anything besides pressing the button.

 

[Hayden Watson]

When steering a course not hard on the wind but still windward of a broad reach, we left the trim unchanged and kept the AP set at 32º apparent. We would steer the boat with the main sheet. If you want to go farther off the wind, ease the boom out and the apparent wind would change due to the rotating of the mast and the AP would turn farther off the wind. We had about 45º to 50º of steering just using the main sheet with the sails trimmed to perfection. Very bizarre.

 

[Hayden Watson]

Its a cool idea I think they call it a Balaton rig? The knock is apparently weight although conceptually it is a freestanding mast ( those have been done) with a boom (those have been done) and the only extra bit is the foreboom?

All components of the rig are carbon fiber so I am not sure how much heavier it would be than any other freestanding rig of similar size. I think about the freedoms. The boat was very stiff but what do you expect from an 85' steel cruiser. I was told that the delivery skipper had a couple of knock downs coming across the Pacific but he put in one reef and never changed it all the way across. I think it was more a matter of not easing the main sheet than anything else. That was with the old main and the first reef on that sail was the same area as a double reef in the new.

 

[FastOlson]

Thanks!!
I have often wondered just what the 'sailing experience' was like on those.

 

[Hayden Watson]

Thanks!!
I have often wondered just what the 'sailing experience' was like on those.

I was very impressed with the ease of getting good performance. So simple. Just point and shoot.

 

[Hayden Watson]

Where the AeroRig gets interesting is when the true wind goes aft of the beam.

6 years ago, wanted to see the world with his wife and 3 young boys. Not liking plane flights and hotels they figured that a cruising sailboat was just the ticket, but his only previous sailing experience was in a Snark at Scout Camp as a kid. He ended up settling on the AeroRig because he was told that it was dead simple to sail which it is. He bought the boat in Sidney Australia and after working on it in the hard for a few months he launched it and the broker and surveyor in the purchase agreed to go out with him on a daysail to show him how everything worked. After that, he and family headed north and cruised the west coast of AU the first year before heading north to the tropics. They cruised pretty much full time for four years before coming back to the States.
All of that time he used the same basic tactic. Trim the sails so that they have about 18” of depth at the foot and set the AP at 32º and ease the main sheet until the jib tell tails fly.

After the boom gets to 45º, set the AP to 90º apparent and square the booms to the wind.
That give the boat a range of about 45º true down to 210º true.

Yep, that is correct, he can sail 30º by the lee but even at that the apparent wind angle is still at 90º. After that you might just as well jibe because it looks really silly with the main boom 45º of the bow and the jib boom 45º off the stern.

In 20,000 or so miles he very rarely sailed with the wind more than 90º apparent on the wind instrument.
The biggest challenge that I had when sailing was trying to figure out which way the wind was blowing.

 

[Will Gilmore]

Thanks for sharing. I found your posts extremely interesting and fun to read.

By the way, unless you're sitting still, all masthead wind is apparent. I can see the rotating mast presenting a problem for instrument displays, since the measured angle is relative to the mounting base.

A cruising couple with three boys, sounds like my family, growing up.

-Will (Dragonfly)

 

[Davidasailor26]

How does it perform early in that transition from 32 degrees apparent to 90? It seems like at 90 degrees apparent you’d be relying on the sails purely for drag, no lift at all. I wonder if it would perform better continuing to ease the mainsheet to extend the 32 degree envelope to deeper true wind angles?

 

[Hayden Watson]

Thanks for sharing. I found your posts extremely interesting and fun to read.

By the way, unless you're sitting still, all masthead wind is apparent. I can see the rotating mast presenting a problem for instrument displays, since the measured angle is relative to the mounting base.

A cruising couple with three boys, sounds like my family, growing up.

-Will (Dragonfly)

Very true that all masthead readings are apparent but with a little electronic trigometric magic the gauge spits out a true wind direction and true wind speed. On this boat, that part of the display is completely bogus for both. I don't think that it is truly possible to understand how turned around you get with the whole wind apparent to a rotating mast from a fixed perspective aboard a boat moving relative to current and wind thing can be unless you are on the boat.

If you look at the photos, the boat has a full cockpit enclosure and while the visibility out to the water is actually quite good given that the rigid dodger has all tempered glass windshields with wipers, the view up is very limited. You cannot see the sails at all from inside the enclosure and because the boom is so high you cannot really even see it unless you are standing all the way forward on the companionway steps.
So for the most part, the only indication you have of wind direction is the wind instrument but its reference to so something that you cannot see. It can be very strange discombobulating.

Here you are happily sailing along on a 90º apparent wind angle to port in 15 knots apparent wind speed making 7+ knots of boat speed from inside the enclosure and life is great!

Then you step outside to look out to starboard and see whitecaps and rollers rushing headlong at your LEE SIDE and realize that the wind is actually coming from 45º aft of the starboard beam which causes a total freak out because ALL of your sailor's spidy senses suddenly tell your that a complete accidental jibe in 20+ knots true with far and away the biggest mainsail you have ever seen in real live is SHOULD HAPPEN, IS GOING TO HAPPEN, WE ARE ALL GOING TO DIE....

Then in a calmer, more rational moment, you look at the rig and see that the main boom is way out over the foredeck at an angle of less than 45º off the bow and the jib furler is just above the primary winches. After some deep breathing to lower the adrenalin you say “Uh, Skipper, do you think that maybe we should jibe???

So we jibe in 20 knots with the biggest darn sail I can imagine and think I think .
So, what do we need to do? I am told to take one or two wraps on the main sheet winch and pull in the main sheet until the apparent wind gets to 170º and prepare for a big ease. I remenber that the main sheet is just a 2-part system and mentally prepare for RELLY BAD rope burns. The boat is then turned through the eye of the wind and I watch the boom swing through about 50º arc ready to ease the sheet to lessen the impact. It hits the end with a bump and I smoothly give it 3’ and think “I should have only used 1 wrap”. Easiest jibe I can remember! With the jib balancing the main, it becomes a non-issue.

 

[Hayden Watson]

How does it perform early in that transition from 32 degrees apparent to 90? It seems like at 90 degrees apparent you’d be relying on the sails purely for drag, no lift at all. I wonder if it would perform better continuing to ease the mainsheet to extend the 32 degree envelope to deeper true wind angles?

I am glad someone asked this. Until now, for the owner, it was just a matter of how far out the boom was. The sails were always trimmed the same ie, tight. After the boom was out to 45º from centerline, he would switch to setting the AP to 90º apparent which would square the booms to the wind. He then trimmed to the course he wanted. It is very strange to steer with the main sheet but that is how it works on this boat. He still had the sails very flat so they were just a drag element at this time and might as well be a barn door.
I suggested changing the trim of the sails when we went to 90ºA so that they were getting shape and working like a foil instead of a barn door. I eased the main out haul so that we had about 4' of draft with a lot of leading edge curvature so that all of the tell tails were streaming. I then eased the jib to about 3' of draft but this created a lot of twist. so that only the bottom tell tails streamed. I then tensioned the down-hauler, which is a line that pulls the clew toward the front of the boom and by playing with the sheet and down-hauler, I was able to get a very full shape that had lots of draft with little twist and all tell-tails streaming. The leading edge of both sails was 90º to the boom instead of 30º in the upwind mode. After these changes we saw about 1 knot improvement in boat speed in 7 knots of wind.
I use this very full trim on my boat in very light air when close hauled to create more power so that I can keep sailing in light stuff that would stall the boat otherwise. On my boat I need to steer a lower course in this trim and realize that the lift vector is lower and the drag vector is greater but it is better to move than to stand still. The same happens on the AeroRig but because that big bad old drag vector can be rotated until is is aligned with the boat centerline, it is a WIN-WIN!
We ended up using the same full trim when close hauled in wind under 6 knots to get the boat moving but needed to set the AP to 45º.

 

[shemandr]

Your description reminds me of a balanced rudder. Is that a good comparison?
I once saw one of these rigs in Nantucket. It was on a boat that had just completed a trans-Atlantic. Mom, Dad, and 2 small kids. The kids were having a ball at the dock crawling all over the rig.
The rig seemed kind of lunky but I enjoyed reading your account of it in actual use.

 

[Davidasailor26]

I suggested changing the trim of the sails when we went to 90ºA so that they were getting shape and working like a foil instead of a barn door. I eased the main out haul so that we had about 4' of draft with a lot of leading edge curvature so that all of the tell tails were streaming. I then eased the jib to about 3' of draft but this created a lot of twist. so that only the bottom tell tails streamed. I then tensioned the down-hauler, which is a line that pulls the clew toward the front of the boom and by playing with the sheet and down-hauler, I was able to get a very full shape that had lots of draft with little twist and all tell-tails streaming. The leading edge of both sails was 90º to the boom instead of 30º in the upwind mode. After these changes we saw about 1 knot improvement in boat speed in 7 knots of wind.

Makes sense. Trimming it out so that the leading edge is perpendicular to the boom, and the boom perpendicular to the wind sounds like the way you’d trim a symmetrical spinnaker on a pole. Gives some lift instead of pure drag.

 

[Hayden Watson]

Your description reminds me of a balanced rudder. Is that a good comparison?
I once saw one of these rigs in Nantucket. It was on a boat that had just completed a trans-Atlantic. Mom, Dad, and 2 small kids. The kids were having a ball at the dock crawling all over the rig.
The rig seemed kind of lunky but I enjoyed reading your account of it in actual use.

the balance on the rudder is the perfect analysis. The only time he has had any excitement with a jib was one that he needed to do in a storm when some damage to the jib sheet car forced him to sail without the jib. That one was as expected rather "fun". Still no real drama because the rig is very flexible and automatically bleeds off excess power by bending and there are no shrouds to hit. When the boom hit the end of the main sheet, he lost control of the line and the boom played out until the main flagged. He then needed to crank back in a hundred odd feet of sheet. I am sure that his index finger was exhausted from pushing the button SO LONG!!!
It looks clunky because of the large cross section but given that it is all carbon fiber, I suspect that it does not weigh nearly as much as it appears.

 

[Hayden Watson]

One other interesting aspect of the AeroRig is that if you get hit with an unexpected squall, you can cast off the main sheet and let the main flag which completely depowers the rig. This can even be done on a dead run because the mast is capable of rotating about 270º. You need to take it back in the same direction because that is about the limit of the wiring inside.