Rigging Documentation and Sea Trials of Philip Maise's Aft-Mast Mounted Semi-Double Crab Claw Rig
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Rigging Documentation and Sea Trials of Philip Maise's Aft-Mast Mounted Semi-Double Crab Claw Rig Dates: November 29th – December 3th , 2010 Location: South China Sea ….Singapore to Brunei Winds: 0 Knots to 11 Knots Seas: Calm to light depending upon day and time Boat: Philip Maise's 65ft Trimaran Loading: 2 Crew including master/owner 7 Tenders 150 HP engine Dingy Engine 2800 Liters of fuel and water 80 Liters of Oil 4 Month supply of food 3 Large Anchors 1 Small 2 Sea Anchors 4 Sails 1 Piano, Full Size Oven, Tools, and Misc. Sails and Placement: Small Crab Claw Sail No. 1 with attachment at the 67ft mark. Comment About Loading....The trimaran was fully loaded for long term cruising. Test results were not skewed by emptying the boat. Test Objectives: Video self tacking. Identify weaknesses in rigging Deck hard ware Tension Rigging . Upwind Testing Disclaimer: This documentation is not intended to be used by anyone to modify or build their own sail boat. Test Results and Comments; I'm very pleased to report that in summary testing went very well. I learned vital information regarding the combined functionality of the boat, sail, rigging, and mast. I'm excited about the prospect of taking this knowledge to the next level to incorporate what I learned into an even better combination. November 29 th , 2010 We had very light winds insufficient for any testing. However, we still raised the sail and spent most of the day adjusting multi-blocks to control the spar in the sail. Near dusk a squall hit and we pulled up on the spilling line to reduce the exposed sail area. The flex in the mast was unacceptable when we pulled on the spilling line, so we decided to drop the sail and motored overnight. The spilling line is a line used to lift the lower spar in the sail up high into the air to decrease the amount of exposed sail area. In essence it is a reefing line which pulls the sail up out of the wind instead of down out of the wind. Upon reflection we figured out that it wasn't a good idea to have the spilling line come all the way down from the 80ft mark. Further, it wasn't a good idea to pull the other end of the spilling line on the same side that the sail was flying. Three forces all pulled the top of the mast to the starboard side. The sail itself, the spilling line, and the spilling line control line. November 30 th , 2010 Winds were slightly better and we were able to shoot a video of the boat making windward progress, and self-tacking without changing lines or engine assistance. At the time we were traveling less then 3 knots under sail. It can't be described as being a fast racing tack, however, the perfect low stress tack for a short handed big cruising boat like mine. Here is the link. http://www.youtube.com/watch?v=4JSH1s6aGEQ Much of the day was again spent working on the down haul lines. I was reluctant to simply take a stand and say...”Here is where I am going to drill into my deck.” In the late afternoon I went up the mast, checked on rigging, and added a new block at the 30 foot mark for a relocated spilling line. The control line for the new spilling line was brought down to the base of the mast. In this way we believe we drastically reduced the bending load upon the mast caused by the spilling line. Since the sail mainly flew on the starboard side, the old spilling line was tied off to a cleat on the port ama. That evening the winds dropped to zero. We motored with the sail still raised. The spar in the sleeve of the foot of the sail helped prevent the sail from flapping. December 1 st , 2010 Much of the day was spent motor-sailing with the winds coming around at various angles. Overall, the light winds were providing about 1 to 2 knots increase in the overall speed. The sail is remarkably well behaved when motor sailing with winds that are variable in both direction and speed. We didn't need to do anything with the lines when the winds changed and still received a boost in speed even though the winds sometimes came from starboard, port, front, or back. No change in sail trim or touching a line was required. This said, we did some experiments with trimming the sail. Our tentative conclusion was that sailing close to the wind required letting the boom out and easing the sail. i.e. The exact opposite of what you might expect based upon your experience with a conventional jib sail. One thing we were noticing is that sail shape was rather poor unless we moved fairly far off the wind. The sail was just not filling nicely. Initially we were concluding that the sail was just not good to the wind. However, I later realized that on the previous round of tests I moved the center of effort, CE, forward to get the boat to sail downwind. Therefore, late in the afternoon we dropped the sail for two reasons. The first reason was to move the halyard down from the 67 ft mark to the 50 ft mark. The second reason was to change the line for the tack so it could be longer and we could move the CE back. so we motored with the sail still raised attempted to motor while the sail was up. I also took up a line to attach a fixed line from the 67 ft mark to the foredeck. The reason for this was the sail when flown from 50 ft instead of 67 ft would not provide the forward mast support. The new fixed line running from the 67 ft mark to the foredeck was attached to a cleat on the port ama. The reason for this was to provide extra support for the mast since we were mainly flying the sail on the starboard side. We raised the sail again, and now the sail head came right up against the mast at the 50 foot mark. Windward sail shape was still poor till we finally realized what was going on. We had failed to provide adequate tension in the combination forestay/halyard. Since the sail head was already at the top of the mast we accomplished this by tightening the line attached to the tack. It just so happens there is a very conveniently placed electric winch to accomplish this with on my boat. It is my Maxwell windlass. Once we finally tightened this line we could finally deduce what was hindering sail shape The overall shape of the crab claw sail when flown is a cone turned horizontal. Think of each cross sectional area it like the letter C. A loose leading edge allowed the sail to curl and create a C shape where in the top of the C shape was hindering both performance and sail shape. Applying a lot of tension to the leading edge caused the overall sail shape to have a cross sectional area more like the letter J. After making these changes we found windward performance was markedly improved. Lets stick a moment longer looking at the shapes of the letters C and J. Obviously for more lifting effect it is better to fly the sail with the letter C. The upper part of the C catches the wind and pulls the boat upward and out of the water. However, this is only good for beam reaching and down-winding. When trying to pinch to the wind it is better to have a very tight leading edge and a cross section more like the letter J. December 2 nd and 3rd , 2010 Winds were mostly light and from behind. It would have been nice to have tried out the bigger crab claw sail that was designed to fly from the 67 foot mark. However, until I fully tested the smaller sail under all conditions it would have to wait in its bag. We kept autopilot on as we motored and ignored what the wind angle was. The sail made numerous accidental gibes, however, we failed to notice these and had to look up at the sail to see which tack it was flying on. No wonder a previous crew member complained there was almost nothing to do while aboard my boat. With the heavy rains we were receiving these two days, I would think she would have been grateful to be able to stay inside and read a book. Shorthanded crewing is an unfortunate fact of life for most cruising boats and this design is working well in those regards. December 4rth , 2010 Morning conditions should have put more fear and caution into us. I have posted a video on you-tube. http://www.youtube.com/watch?v=XAVFh2heetA The morning observed skies were unstable to say the least. Off our starboard bow we stood watching a very large water spout that appeared to be less then 10 miles away. A water spout is essentially a tornado over the water and I have seen now six of these in South East Asian waters. In one storm outside of Singapore I saw two at the same time. Later in the afternoon, when very dark clouds formed in front of us, we paid them little heed. We were feeling pretty safe with just the small crab claw sail up flying at the 50ft mark.