Round two for my aft-mast rig...Now an aft-mast mounted, rotating, wing mast
It has been almost two years since my last effort to rig my boat aft-mast and if at first you don't succeed try try again. If you don't recall that last attempt...it overall was a very expensive lesson in how a column behaves when over compressed. This time I trying a bit more:
C O N S E R V A T I V E L Y
I've prepared a drawing attached and am working out final rigging line attachment points. It was rigging lines interacting with the forestay and head sail that helped defeat the first attempt. In my own defense, I was very anxious to get my boat moving again and out of Thailand. These past nearly 2 years have given me time to study a lot more. Here are the major differences.
1. First attempt was 80 ft (25 meters), and this one will be 60 ft (18 meters). Tasker made me two sails. During the sea trials the big one never left the sail locker. If the boat performs to wind, as it was doing in the first sea trials, I may have the big one recut into a spare sail that uses the same size spar in the foot. This spare sail would have a longer leach and come closer to the pilot house. I know that the sail looks a bit funny so high above the pilot house. However, keep in mind that you are viewing this 816 ft2 sail on a 65ft long trimaran. In reality it isn't too far different that the head sail you see on many cats that have tall living areas that sit above the two ama. My living area is below the deck level and the pilot house rises only about 30 inches above deck level. On a cat the living area way higher than that.
2. Keeping my big sail in the locker for now allows me to do something really neat. I can rake the mast forward. Way forward. Preliminarily the angle is set at 13.84 degrees. With this much forward rake the base of the mast is still mounted in the aft position, however, the head of the mast is pretty much near where the original 79 ft beast stood. Looking at some of the other designs that angle is starting to look like copy cat. However, it works. So be it.
3. Unlike the first attempt that required a backspar to achieve the necessary angle to support the mast, raking way forward provides a great back stay angle. This back stay angle positions far more support on the mast than the original 79 foot Bermuda rig that only had the two side stays. Overall, the new mast has a better support angle all the way around.
4. Learning. Yes I'm allowed to learn. The forward side stays as shown in the drawing are mounted at the 30 foot mark. This helps prevent them from being interactive with the forestay and eliminates the previous setup that led to over compression. These two side stays mounted way out on the ama.
5. With no main sail behind the mast I can put lower backstays at the 30 foot mark. However, unlike last time I'm not going to worry them into a 45 degree position behind the mast. I accomplished this with a little gymnastics with a jumper to another stay mid air. Fewer lines in the air. Yeah!
6. I looked long and hard at the side rear backstays I have mounted on the ama. There are two connection points to each ama, and the logical thing is to mount the rear side stay as far back as possible. However, my sailboat is made out of DuraKore which is balsa core. Structurally, I dont' like the idea of pulling off the back end of an ama. In the drawing they are kind of hard to see as they are almost in perfect line with the mast. However, they are 19 feet to the side of the mast and can take lateral loads well. I've drawn them now going up to the mast head. I believe they can be dropped back down to the 45 foot mark, however, have yet to evaluate that.
I'm working off my own spread sheets and brute force going through each calculation. I hired a sail plan designer who does all the force equations and nice fancy curves for Bermuda rigs. All he could give me was a sail plan and the specifications for a Bermuda rig. That is all his program spits out.
I figured out recently that what I am doing is called "Velocity Prediction" and a little finite element analysis. I certainly can tell you honestly that Euclidean geometry and I are the very best of friends since I can quote every angle and force upon the mast based upon wind speeds and sail position. Well nearly any.
7. Since this isn't a Genoa, I can't use a roller furler on the forestay to wrap the sail up neatly. This time round I'm going to have a sock made that draws up the forestay. The idea is for the sail and spar to come up to the forestay. Maybe not the best solution, however, I think it will allow me to contain the sail until it can be brought down to deck level and put away proper. If sailing relatively soon, it can stay right there and the bag will provide UV protection.
My original idea was to turn the sail around the foot. However, unless there are enough crew members to hold the sail in the middle, it doesn't work easily. The local Malaysian sailboat Uranus had 15 crew members aboard and would have no problem. However, I'm not keen on feeding that many crew. Solutions for me need to be one or two people solutions.
8. The spar in the foot of the sail is any area for improvement. During sea trials I noticed too much flex in it. I believe if I can stiffen it up it will help improve overall sail performance. I'm thinking of adding a carbon fiber outer sleeve.
9. Another factor I've been working on is diet. My sailboat is just too heavy. So far I've dropped about 2,000 lbs. The new wing mast with no boom will be about 500 lbs lighter than the old rotating mast with boom. I would like to get her down another 2,000 lbs. However, I'm not trying to win the King's Cup just yet. One obvious weight savings is putting the big outboard, fiberglass sailing tender, and 3 kayaks, and the big sails into storage. I also don't need hurricane storm equipment when I'm not sailing anywhere in those areas.
Any comments about positioning of rigging lines are welcome. Oh..
By the way...Yes the sail does look very small compared to the size of the boat. However, given the squalls and extreme winds in this area it is conservative. Further, the boat is for cruising and not ultra racing. Besides....we may just find out a small crab claw sail is more efficient than a big full batten mainsail.
Phil Maise
It will be about 3 to 4 months before I have the new rig on. Just a small matter of moving from point A to point B. Well it is a distance greater than NYC to Miami and two different countries away.
