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Home , Block (sailing), Cleat (nautical), Crab claw sail, Extra (sailing), Jib, Mast (sailing)

Rigging Documentation and Sea Trials of Philip Maise's - Mounted Semi-Double Crab Claw Rig

Dates: November 29th – December 3th , 2010

Location: South China Sea …. to

Winds: 0 Knots to 11 Knots

Seas: Calm to light depending upon day and time

Boat: Philip Maise's 65ft

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 1 Small 2 Sea Anchors 4 1 Piano, Full Size Oven, Tools, and Misc.

Sails and Placement: Small Crab Claw 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 .

Test Objectives: Video self . Identify weaknesses in 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 insufficient for any testing. However, we still raised the sail and spent most of the day adjusting multi-blocks to control the 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 line which pulls the sail up out of the 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 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 , 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 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 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 out and easing the sail. i.e. The exact opposite of what you might expect based upon your experience with a conventional 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 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 support for the mast since we were mainly flying the sail on the starboard side.

We raised the sail again, and now the sail 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 /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 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 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 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 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 we stood watching a very large water spout that appeared to be less then 10 miles away. A water spout is essentially a 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. We had moved the spilling line down to 30 ft, we attached the old spilling line to the port ama, and we had a new forestay at the 67 ft mark attached to the port ama

We were humming along nicely ignoring the looming black clouds when a sudden and dramatic wind shift moved the sail from starboard to port.

Well you probably can guess what occurred after that. Mother nature gave me a swift kick in the pants and told me to think about the problem of supporting and aft-mast a little better. I'm pleased to report to you that this gentle push has helped show me how to support an aft-mast a lot better.

Lessons Learned

Lesson Learned #1 – Focus on mast support at 4:30 and 7:30 o'clock.

I knew these areas were very important, however, I couldn't mount chain plates on the boat in these two areas since the very back corners of my two ama couldn't take the load and the would be in the way of my wind generators. In the first sea trial I had devised something I called a “running forward stay” to close the gap in support. These are the horizontal looking lines you might see in one of my pictures. This running forward stay helped mast stability under sail. However, the problem with this running stay is it subtracted strength from the two lines it pulled together.

The light bulb to provide better support in these two areas came on just yesterday. The solution is to use two back spars instead of one. With two back spars, I could have led lines directly down to the 4:30 and 7:30 o'clock and then distributed the load over to the chain plates located at 3 o'clock 5:45 o'clock 6:15 o'clock and 9 o'clock. Mast support directly behind the mast would still be possible via these spars by splitting the stay coming down from the mast into two. This is very much the same split stay arrangement in mono-hulls.

Lesson Learned #2 – Build an aft-mast with mast fittings from scratch, don't recycle.

I elected to go with the aft-mast configuration after I already had the mast and its fittings well into production. I also switched from wire rigging to high-tech Dyneema after fittings were in production. This meant I had two weaknesses in the mast when it went to sea. The mast was too tall for the application and should have been cut down from 82 feet high to 68 feet high. This change would have eliminated most of the unstayed weight above my 67 foot mark. When the wind shift occurred the old spilling line was helping to stay that high weight, however, it was located only on the port ama. Therefore, when the wind shifted and pushed the mast to port, it didn't help support that weight. In fact, I had prestressed that stay which meant when the wind shift occurred, it was doubly counterproductive. The interface of the mast fittings, as well as the angles they came off the mast were set for a center rig. Yes I knew this was a problem, however, time was really against me and I wanted to get the mast up and boat back on the water.

Lesson Learned #3 – Integrate rigging hardware and customize fittings. Now before anyone jumps down my throat and claims it is impossible to support a mast without wire rigging, please let me point out that rigging has been supporting masts for centuries. Further I elected Dyneema rigging after seeing how strong it was and learning I wouldn't have to worry about it corroding. I had already learned during the first set of tests that the thimbles shops were offering me were woefully inadequate for the application. For this reason I had many reinforced thimbles custom made for me. What I didn't consider, and partly had no ability to do after the fact, was to integrate reinforced thimbles into mast fittings and deck chain plates. What I ended up having to do is open up a standard thimble and pass it through the hole of the mast fitting or chain plate. Also when I wanted to join two thimbles together, one of them had to be standard. What I learned was this approach may initially work, however, while at sea, the standard thimbles can still be crushed under the loads, or worse yet they can be turned around and spit out. This leads to premature chaffing of the lines. Therefore, taking care to make chain plates, and mast fittings in combination with rope terminations is key.

Lesson Learned #4 – When using Dyneema Rigging Use Longer Bars Tension on my rig was less then tension possible if I had used wire rigging for two reasons. Firstly I was working with a rather flexible mast that could fairly easily develop an S shape curve if I tensioned one side too much. Secondly, the Dyneema lines stretched more each time I encountered more and more severe sea conditions. It was either that or Dyneema lines are subject to long term creep when under load. If the later is the case then upon arrival at port the tension should be reduced while sitting in harbor, then reapplied just before going back out to sea. What all this has to do with spreader bar length is you should consider Dyneema line as being far more flexible then wire rigging and adjust spreader arm length to help the mast stay in column. I already knew after my first initial tests of this problem and had returned to the shop that made my spreader bars. I asked them to make me longer ones to fit into the existing sockets already mounted to the mast, however, the running the shop claimed it was not possible. Personally I think the guy was just miffed that I didn't buy his total package of mast, rigging hardware, and rigging wire.

To a large extent I think it was exactly this issue that was the leading cause of the mast failure. The mast broke at the 28ft mark which is just 2 feet below where the spreader bar was located. This indicates to me that I didn't have a failure in the main rigging cables, I had a failure in the diamond stays to keep the mast in column. After failure I inspected all the rigging cables and found them all excellent condition. I admit I was telling people the reason you saw so many rigging lines, was I essentially had redundant rigging. This unfortunately true only to a certain extent. The diamond stays were not redundant and as I previous stated the spreader bar length was most likely inadequate.

Lesson Learned #5 – Prestretch Dyneema Lines Initially I envisioned being able to calculate the exact length of each Dyneema line I needed and neatly splicing these lines around thimbles and everything would look very neat and simple. However, manufacturers of Dyneema lines are supplying them as they come off the spinning machines without making an attempt to prestretch. As a result you get more then you paid for. This may sound initially good until you find yourself continually going around your boat and retensioning lines again and again. Not splicing the lines around the thimbles allowed me to retie knots and make the lines shorter. I then used a multi-line tensioning system that wrapped around two thimbles that were relatively close together. This allowed me to pull on the smaller lines and get purchase in drawing in the larger line. At sea I could wait for the waves to pound the rig and take in the slack each time. I've given this area some thought and think I have come up with a way for anyone with a winch and some smaller line with a known breaking strength to stress lines to 50% of their breaking strength before using.

Areas to work on for future mast design.

Redesign Issue #1 – Back Spar Mathmatics One thing I have yet to tell you about the postmortem is the accident victim was found with a broken back spar. I think the odds are rather remote that the back spar broke first, however, I still have a lingering question whether my back spar was the butler that did it in the library with the candlestick holder. You see, the mathematics involved in answering this question are quite complex.

What is the optimum back spar length, position of the mast, and angle to the horizon.

As you can see from this equation we are dealing at least three variables. A fourth variable is back spar diameter and strength. A longer back spar may push loads farther back, allowing for better mast support, however, in turn the spar must be bigger and stronger.

Further, now that I am firmly convinced I need two back spars, what angles should they be to the mast?

Redesign Issue #2 – Manufacture of Integrated Rigging Fittings and Lines Again as I already pointed out the sailing industry is providing woefully inadequate solutions to utilize high-tech high-tension rigging lines. I'm undoubtedly going to have to have these all custom made and given this is now the second time around I am beginning to feel an obligation to help others with this type of solution. I'm not the only out there that is frustrated with the current supply chain. Therefore, this time around I'm considering setting up a firm to supply tested and integrated solutions to others.

Redesign Issue #3 – Mast Design In general I was very happy with the previous mast design. It was light, flexible, and tapered to my exact specification. However, with this opportunity to rethink and reconsider options, I'm putting everything back on the table again. What material, what shape, what support? Should I pick up a mast from one of these racing boats, or should I build from scratch? I do love a project!

Redesign Issue #4 – Spilling Line Automation? The spilling line if utilized would have reduced the sail area exposed to that wind gust. However, it wasn't employed because we simply had no time to respond. This sounds to me like a perfect time to think of a way to automate a response. It is pretty easy to measure rig load and integrate an electric winch to keep that tension at a set amount. With an automated spilling system your rig would adjust itself to variable wind conditions and change the exposed sail area for you.

Summary and Overall conclusions:

#1 – The small crab claw sail demonstrated it could pull the heavily loaded trimaran to the wind and self-tack. #2 – When going to the wind the CE should be moved backward, and when going downwind it should be moved forward. #3 – The combination halyard/forestay tension needs to be very tight when pinching the wind to shape the sail into a letter closer to a J. When on a beam reach a looser tension is better so the sail provides more lift and shapes itself closer to the letter C #4 – An aft-mast needs to be purpose built with purpose built mast fittings designed for the angles and rigging involved. #5 – Look at rigging and rigging lines on an integrated basis and have them custom built. #6 – Longer spreader bars are better when the rig is lightly tensioned. #7 – Two back spars are better than one.

Personal Note: One thing I have yet to mention is that after 2 hours in high seas recovering my lines and blocks I must have been fairly tired when I got back aboard. I promptly slipped on the deck landed on a winch and broke 4 ribs. I'm planning on keeping the boat in Miri while I recover and want to travel home for the holidays as soon as I can fly.

If you are interested in helping me with the boat's next transformation, I am all ears.

Philip Maise Miri Malaysia pbmaise AT yahoo DOT com