Rudder design rejuvenates Pearson 40Jan 1, 2003
To the editor: A 20-year-old production boat of mine was greatly improved recently, all because of a few conspiring circumstances: an active owners association, a great naval architect and a disaster at sea.
The impetus for this project came from the ache in my arms after a long day of sailing in strong breezes near my home in St. Pete Beach, Fla. My arms were sore from fighting the wheel on my Pearson 40, Passion, a 20-year-old production design from the Pearson Yacht Corporation and the design board of Bill Shaw. The Pearson 40 has an unbalanced rudder hung on a partial skeg.
The stern of the Pearson 40 is fairly pinched, due to the IOR handicapping rule that was in vogue at the time the boat was designed. I found that this pinched stern and associated "bustle," forward of the rudderpost, unfortunately decreases the effectiveness of the rudder, especially when the boat is heeled or in rough water. This loss in rudder effectiveness, when coupled with the unbalanced rudder profile, dramatically increases the turning load on the wheel, making for long, arm-tiring stints at the helm in heavy weather. No amount of reefing or sail-trim adjustments could relieve the loads. This problem was particularly annoying for me, since my three previous boats were all designed and built with balanced spade rudders, allowing for very light wheel loads in almost all conditions.
In addition to the impact on humans, the difficulty in steering also proved to be a major problem for the wheel-mounted autopilot. In any condition other than light winds and calm seas, the autopilot was unable to steer successfully. I knew that in the long term, I would never be happy with the steering of the Pearson 40. My dilemma was that I really love the Pearson 40 in every other way and did not want to sell it. I knew that there had to be a better way. The solution came when I read an Ocean Navigator article on offshore hull design, by naval architect Roger Marshall (Issue 107 July/August 2000). Marshall included a section on rudders. I liked what he had to say, so I contacted him, and we began a discussion on the feasibility of designing a new rudder for the Pearson 40. The initial discussions started in September 2000 and were proceeding very gradually, since I was not planning on the rudder change until at least mid-2001. An unexpected event changed my plans, however.
Denny Thompson was cruising his Pearson 40, Dream Catcher, back to Seattle after competing in the Victoria to Maui race, when he was knocked down, apparently by a rogue wave. The knockdown caused a failure in Dream Catcher's rudder that allowed the rudder blade to rotate freely around the rudderpost. Thompson sailed the final 1000 nm back to Seattle with a jury-rigged rudder. During that time, all remnants of the original rudder and part of the skeg disappeared.
Suddenly there was an urgent need for a new rudder for Dream Catcher. Thompson posted his story on the Pearson 40 owners' website (www.pearson40.org) and immediately received offers of assistance from multiple owners. I shared my idea for a new and improved Pearson 40 rudder with him. Thompson's recent experience hand steering Dream Catcher to Maui convinced him that the steering loads on the Pearson 40 were excessive. In his words, "We all felt like Popeye with swollen wrists and forearms from steering for 16 days with the heavy rudder." He was very interested in improving the steering performance. I now had an ally in my quest for a kinder and gentler Pearson 40.
In order to get started on a new rudder design, Marshall needed pictures, dimensions and patterns of the existing rudder's profile and sections. Since Dream Catcher's rudder was at the bottom of the Pacific and my boat was still in the water, we needed to find help from someone who could quickly pattern an existing rudder. Back to the owners' website and enter Ray Crowdis, owner of the Pearson 40 Forever Island in St. John, New Brunswick. Crowdis had recently pulled Forever Island for the winter and just so happened to have removed his rudder so he could perform some minor repairs over the winter. Crowdis was more than happy to provide all of the patterns and measurements we needed. We now had all the information Marshall needed to start his design and engineering work.
Marshall warned me early on that any design we came up with would be only a best guess, since he did not have the hull design plans or any hard data to work from. I developed a great deal of trust in Marshall's instincts, so I was willing to accept that risk. Over a period of weeks, Marshall and I spent several hours on the phone and the Internet exchanging ideas, defining goals and passing sketches back and forth. Thompson also participated in those discussions, providing valuable input based upon his thousands of offshore miles at the helm of Dream Catcher. We agreed to a set of design parameters:
· A partially balanced blade profile to reduce wheel/steering loads;
· A significantly stronger internal rudder structure;
· A design that required no hull shape modifications;
· Engineering that could reuse as many existing components quadrant, stuffing box, etc. as possible.
With agreement on the design parameters, Marshall went off to work his magic (black art is how he described it). Several weeks later, a set of full-sized plans for the rudder blade and internal structure arrived.
One advantage I had for this project is that I live in the St. Petersburg, Fla., area. For years, St. Petersburg has been a hotbed of boat design and construction with the likes of Morgan, Irwin, Kiwi, Caliber, Watkins, Island Packet, Precision and many other well-known builders/ designers located here. Consequently, there are many knowledgeable and experienced local suppliers and fabricators for marine products. With Marshall's plans in hand, I contacted two local marine fabricators: one to build the rudder's internal, stainless steel reinforcing structure and required bearings, and one to build the epoxy and fiberglass rudder blade. Several meetings were held with all participants, including Thompson via telephone, to discuss and engineer all of the components, select appropriate materials, and walk through how they would be assembled and installed. These meetings turned out to be one of the most important aspects of the entire project, since the details could be drawn out on paper, and any ideas and concerns could be discussed and resolved prior to construction.
It was during these meetings that a new and significantly stronger lower rudder-bearing design was developed. A design reference point was established for all component dimensions. Material selection was made, and a project plan with dates was agreed to. Shortly thereafter, construction began, and six weeks later two new rudders were ready for installation. It was time to put all design and construction efforts to the test. I hauled my boat and began replacing my rudder.
Removal of the steering cables and quadrant came first, followed by removal of the old rudder blade. Once again, the Pearson 40 owners' website proved invaluable. As Crowdis removed his rudder, he photographed the process and wrote a description of the steps. He posted those photos and text on the owners' website and I was able to see exactly what was required. A process that might have taken me a day or more by trial and error ended up taking less than 30 minutes. After removing the appropriate filler and fasteners, the old rudder was carefully lowered out of the boat.
Installation of the new rudder was very simple, since the design reused most of the original components. The only hull modification required was a slight adjustment to the bottom of the skeg to accommodate the new, lower rudder-bearing design. This was accomplished in less than an hour. Once the skeg modifications were completed, the rudder was ready to be inserted in the hull and dry-fit to check that everything fit properly and was aligned correctly. Thanks to careful design and construction, the rudder fit perfectly and was ready for final installation. This was accomplished the second day with minimal effort. The key was to insure that the rudder was fitted perfectly vertically in the boat. This was accomplished by leveling the boat on the jack-stands using a standard construction level across the toerails. (Exact fore-and-aft leveling was not necessary
because a partial skeg at the stern served as a guide in this direction; furthermore, for-and-aft alignment is less crucial than athwartships.) The rudder assembly was then inserted in the boat and placed on blocks. The rudder blade was leveled vertically using the same construction level, this time placing it on the trailing edge of the rudder blade. Once the rudder was leveled, the lower bearing was fastened to the skeg with bronze bolts. Thickened epoxy was injected between the bearing and the skeg and around the lower bearing to fix its position. We allowed the epoxy to harden overnight. On the third day, the rest of the steering components were cleaned, lubricated, reassembled and adjusted. Day four was spent fairing and painting, adding flexible flaps to cover the skeg-to-rudder gap, and adding a "crab-pot deflector" forward of the rudder's leading edge.
By the fifth day, the project was complete, the Pearson 40 "Mark II" was born, and it was time for sea trials.
Needless to say, after all of the effort (and money), I was dying to see how the new rudder worked. The first indications of the new rudder's performance came while motoring Passion from the yard to her regular dock. Under power, steering was performed with fingertip effort and the turning radius was less than a boat length. Wow! But the true test was going to be sailing. The following weekend provided 15- to 20-knot winds on the Gulf. Those were the exact conditions that convinced me to change the rudder in the first place. With 18 to 26 knots of apparent wind, a reef in the main and a 110 percent jib, I could steer the boat with two fingers. The tracking was arrow-straight, and while I don't have any hard data to prove this, I was sure that the boat was significantly faster (Thompson agrees). I couldn't believe it. I was suddenly sailing an entirely different boat. I was expecting an improvement, but I never expected that a relatively small rudder change would make such an incredible difference. The final test of the new rudder came when I used the old autopilot for the first time. Just as the case was for me, the autopilot, which originally seemed under-powered and incompetent, suddenly became exceptionally accurate and capable of steering the Pearson 40 in all but heavy, quartering seas. Fantastic!
Was it worth all the time, effort and money? You bet. Instead of paying for a whole new boat that handled the way I wanted, I got the improvements I demanded and gave my Pearson 40 a new lease on life for a small fraction of the cost. Would I do it again? In a heartbeat!
In a project like this, the devil is truly in the details. The keys to our success were: the team of people involved
Marshall, the fabricators and the three boat owners, careful planning and good communications. Marshall's vast sailing and design experience, in everything from 12 meters with the Courageous group to cruising designs of all sizes, both designing on his own and with Sparkman & Stephens, resulted in a winner.
Based upon the experiences on Dream Catcher and Passion, Crowdis decided to modify Forever Island's existing rudder to match the new rudder-blade design and has had similar improvements in steering and performance. The owners' association is now working with the largest supplier of replacement rudders, Foss Foam in Willistin, Fla., to offer a standard replacement Mark II rudder for the Pearson 40 so that more Pearson 40 owners will have access to the benefits derived from the efforts of the team.
An experienced racer, Chip Lawson started sailing on the Great Lakes at age 11. He hopes to move aboard Passion soon and head for the Pacific.
Roger Marshall comments on this project:
In this project there was very little information to start with, other than the fact that the boat was hard to steer. Chip Lawson and I had a lot of conversations that gradually eliminated various reasons that could cause the helm to be heavy. There are many potential reasons for a heavy helm; some are not quite so obvious. For example, moving the mast can significantly affect the helm. Moving it aft increases weather helm and moving it forward reduces weather helm. The first job was to eliminate factors outside the rudder that could be causing helm problems.
Lawson and I talked many times, and gradually I eliminated many factors. For example, the rudder did not have a lot of rake, so its heaviness was not introduced as Lawson turned the helm. Rudders with a lot of rake tend to get heavier as the boat is turned. Adjusting the sail trim did not alleviate the heaviness, and I asked Lawson about the location of his mast. It had been moved around without much change in the helm condition. Apparently the heaviness was present under every condition of sailing, downwind and up. This told me that the rudder was probably the problem.
The rudder blade was entirely aft of the stock, with a half-skeg in front of it. Because the stern was "sucked up" just above the rudder in order to meet the old IOR girth measurements, I felt that flow over the top of the rudder would be fairly turbulent and the blade would be somewhat ineffective in heavy winds. The problem was to increase rudder area lower down in non-turbulent water, balance the rudder by putting some of its area in front of the stock and make the whole thing fit without changing the boat.
I drew up a blade shape, based on the patterns that Lawson sent me, and pondered it for a while. To my eye, in spite of all the calculations, estimating and design work, I felt there was too much blade in front of the stock and changed it to lessen the area. I sent this to Lawson.
Even then I felt that the area in front of the stock, given the large half-skeg above it, was too much. After discussing it with Lawson we reduced this area slightly and voila! It worked. For future rudders, I would keep the smaller area in front of the rudder blade and possibly increase the trailing edge across the chord length by an inch or two, to introduce just a little more feel to the helm.
I am really pleased that the project worked out well and that an older, well-cared-for boat got a new lease on life. Chip Lawson is a knowledgeable owner who could answer my many questions. His eager participation contributed greatly to the entire project and helped make it work out splendidly.
Yacht designer, freelance writer and photographer Roger Marshall is based in Jamestown, R.I.Edit Module