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Refitting a new Keel and Repairing/ Reinforcing the Structure

The Keel project was anticipated, to some extent. Cruising with a keel that is nearly 9 feet deep is a challenge in most areas of the NorthEast USA. The tide range is 5 to 7 feet in most places, and most harbors near me are less than 8 fet deep. I knoew that I would want to reduce the draft of the boat some day, but I did not want to compromise performance. A potential problem with the keep stub was identified in the survey as a need to rebed and recaulk the keel. As surveyors go, mine was no worse than others but nevertheless the inspection tools of the trade are akin to stone age tools. Only one surveyor in the Northeast useslong wavelength infrared to identify delaminations, the rest find it perfectly acceptable to tap on the fiberglass with a hammer, and they are pretty good at it, but the tool limits discovery of problems. So, we found the problem when I rebedded the keel.

The project starting with this need to rebed the keel, and may be change the backing plates,The decision to get a new keel was made as we pulled the keel off, given the expense and complexity it only mae sense to change the keel at the same time and complete the work once and for all for the lifespan of the boat. The project steps were numerous but the highlights are listed below:

  • Remove rig
  • Build a cradle to accept and secure the old keel, for shipment.
  • Commission Naval Architects to design new keel
  • Negotiate contracts and agreements with two keel makers, select one.
  • Commission the keel fabrication
  • Receive new keel
  • Build hole template to exact dimensions and locations of new keel's bolts
  • Lift boat and prepare to accept new keel
  • Observe problem hidden under the keel stub where the boat was blocked up
  • Grind out keel stub where the problem was observed
  • Hire Naval Architect to look at the issues and advise on the method for reconstruction
  • Reconstruct the keel stub using vacuum bagging and hand layup
  • Planarize the stub and drill to template
  • Dry fit, caulk, tighten bolts, cure time, torque to specs, fairing, barrier coat, bottom paint.
  • Rig the mast
  • WIth the boat arrived in the yard, a couple of days of heavy rain delayed our removal of the 1,000 lbs mast. Once the mast removed and stored, I ground away the fairiing compound around the keel stub interface, and backed off the bolts with a four foot torque wrench. The boat was lifted with a travelift and blocked up on two foot timbers and stabilized on jack stands. It would stay this way for nearly two months while work was performed.

    The old keel was loaded on a flatbed. It would be replaced by a 13,300 lbs bulb keel which keeps the center of gravity of the boat at the same point, to ensure the righting moment and fore/aft level trim is not affected. The purpose of the project was to reduce draft from 8'8" to 7'0" so the boat could enter shallower waters safely. I avoided the temptation to further reduce draft, as some owners did (5'5" or 6'0" would have compromised the sailing performance too significantly).

    Keel Design: Ed Dubois, Naval Architect, normally tackles much more complex and complete yacht designs than the re-design of my keel. I spoke with Ed over the phone to ask his advice regarding shortening the keel and designing an add-on bulb that would be retrofit to the existing keel. Ed advised against this approach as too much of a compromise in the sailing performance of the boat. Since he was the original designer of the Wauquiez Centurion 49, I am certain he was correct in his assessment. He graciously made available to me the design of a shorter keel, bringing a 6 foot draft. I thought this was too short and that the performance compromise would be too much. I decided to go with a 7foot draft, which meant redesigning another keel. On the plus side, the rudder would not have to be shortened.

    Manufacture of the Keel: After breaking the sand mold, the keel is hanged for two days for cooling.

    Manufacture of the Keel: The sand casting halves are joined and held in place by a steel structure. The threader rods serve two purposes. They attach the keel to the keel stub and they are welded together into a reinforcement frame acting as an armature for the lead, which is strenghtened by the addition of antimony (PbSb alloy) but nevertheless needs support. The frame holding the rods is a template.

    Manufacture of the Keel: Once the mold form is in the mold, a sand casting is set around the mold and coated with proprietary coatings. The sand mold can be separated from the form at the parting line. The result is shown.

    Manufacture of the Keel: The finished product has been ground to comply with the design form, and is now being checked for accuracy by a quality control technician, using control templates built from the CAD drawings. I was very happy with the result and MARS keels program management, communications, and capabilities. I chose them because they had CAD/CAM capabilities and were more than an old fashion casting house. Though my keel would be manually built from CAD drawings, the knowledge and approach, in my opinion, permeate the rest of the company and this shows in their product and customer contacts. They built the keel in a record SIX WEEKS! This was unheard of, I was lucky that they worked so hard on the project and also that times were quite slow in the marine industry at the time..

    Manufacture of the Keel: Pouring the lead. The lead flows out of the chute pipe in the front of the keel. The alloy being antimony 3% and lead, the melting point is lower than the lead melting point of 327C, as the eutectic temperature is reached at 17% antimony (251C).  It is about In any case, the energy needed to heat the 13,286 pounds of lead to say about 314 C, plus some margin for cooling (say 340C) is about 73kWH or 250000 BTU without taking heat loss in account. It is surprisingly a small amount of energy, this explains why the furnace is of a reasonable size. These guys have poured keels up to 100,000 lbs.

    Manufacture of the Keel: MARS KEELS is a top quality supplier who built the keel custom to the design specs. The first step in manufacture is the form. The form is created with sections of  aluminium closely fitted on sections of plywood which correspond to the cross sections of the keel in the CAD system. The sections are stacked at the distances required by the drawing as control points to create the 3D pattern, and the sheet of plywood on the center defines the parting line of the mold.

    The new keel arrives. But more work to come, major work.

    After we lifted the boat off the blocks, I noticed a crack on the bottom of the keel stub. The yard and I thought it would suffice to fill the crack and slap the keel on, but that some grinding was needed to ensure that the crack was filled properly. What was thought to be a minor cracked proved to be extensive water penetration damage to th epolyester structure. The laminate of the hull ad disconnected from the internal bilge laminates. Three days of fiberglass grinding and meeling ensued. The picture above shows the grinding half done. Additional grinding would take place to feather the layup on four separate days. The work filled about 80 gallons of debris. A tent around the boat protected the rest of the yard from nuisance dust.

    After grinding the outside surfaces the inside of the mast step was hollowed of its filler. The mast rests on the suface above and the filler had crept due to the 50,000 lbs compression of the mast. The attachment bolt for the keel was loose and this was a root cause. Failure to tiighten the bolt every couple of years is critical, and/or a grounding may have caused some damage as well. The boat showed its age, with some fatigues problems. I doubt the keel would have fallen off for another five or ten years, but the boat is now like new.

    Inserted in the compression well below the mast step, these high density electrical boards have a compression strength of 10,000psi and are highly immune to water problems. They would provide direct transfer of compression loads to the keel instead of transferring the loads to the floor timber below the mast step. The naval architecture firm of Martin, Ottaway, Hemmen & Dolan was consulted and was very helpful in discussing possible solutions. Rick van Hemmen seems to know his trade well.

    After the first six layers of mast compression material was cemented with expoxy and microfibers fill, the interior of the mast compression well was built up and the boards were taped, Approximately 1/4 inch of fiberglass build up alone could hold the mast loads. Additional boards were added to complete the full height. Notice the discoloration of the glass on the side of the keel stub, and the peeled fiberglass which extended actually two feet from the keel stub .

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    This was an interesting project, but tough on the body and the mind.. and the wallet.But this boat is bigger, better, and tougher, than any new boat built for the price invested. An important consideration when in the middle of the atlantic.

    Fiberglass doctors at work. THere were four of us, including me. We wore protective clothing of course, but only when we had to since the heat was in the 90s. Extra slow cure epoxy would be used, and we would start around 7AM to prevent exothermic reaction from runing away. We did this for four days using te vacuum bagging as seen above. The supplies involve peel ply, blanket, and film, as well as two manifolds and a strong vacuum pump. Sealtape is a wonderful material that kept the air from leaking in. The bag vacuum reached 20 to 26 mm Hg. A vacuum regulator was not used.

    Prior to starting this path I did a lot of research on materials and techniques. The key important take aways are:

  • Epoxy has good or better adhesion strength as a secondary bond to polyester, as does polyester
  • Expoxy laminates have slightly better compressive strength.
  • Vinyester has better water resistance than polyester, but nothing beats epoxy.
  • Cracking a fatigue are less of a problem with epoxy as it is more flexible , less briddle
  • Vacuum Bagging brings higher density of fibers, by about 30%.
  • Using Vacuum Bagging was critical since the construction technique call for unidirectional glass on the bottom of the keel stub, and the more fibers, the more strength on this critcal structure.

    Epoxy has major drawbacks:: It takes a long time to cure and you can't build up layers fast. There is a reason people use vinylester to build boats cheaply, and epoxy /multiaxial laminates to build wind turbine blades. In fact, much of my laminate schedule was derived from wind turbine research from the 70s, and of course cleared with the architect. The price for strength is materials cost and labor costs, but it was important to maximize the strength achieved by the repair in the given available thickness.

    A completed vacuum bagging operation. The first day laid a schedule extending from two feet portside of the keelstub to two feet starboardside. Two layers of 18oz unidirectional, high strength S Glass, and two layers of Biax, spanned the whole width of the repair in one continuous strip. THe strips were overlapped for forward and aft strength. Unidirectional additional layers were placed on the bottom of the keel stub. The SGlass Unidirectional fabric provided fore and aft flexural stiffness in addition to the keel itself. The Biaxial fabric belt wrapping around the stub provided the athwartship torsional strength.

    The laminate schedule: a half inch of biax added to the floor timber, which wraps around to the back of the timber and the keel stub. Afterwards, a high density epoxy milled fibers filler was used to adhere a slab of one inch thick G10 epoxy to the floor timber. The mast load is spread over a very large area, as the garolite board has a 55,000 psi compressive strength and huge flexural strength measured in mega-psi. The mast step is well secured in the G10 board using machine screws after drilling and tapping the G10 Garolite. Note the hole in the center, for socket and extensions access to the forwardmost keel bolt most inconveniently located below the mast! Yes, the Centurion 49 does have a keel bolt below the mast.

    In order to further increase stength of the keel stub I added a schedule of reinforcements in the bilge area, including the floor timber on which the mast rests, and the forward bilge area subject to the highest keel loads and mast loads especially in extreme wind and sea situations. By using epoxy, further waterproofing would be achieved to ensure bilge water did not cause long term problems. THe backing plates previously found on the boat were only 1/4 inch in thickness, this proved very inadequate and slight creeping and distortion of the plates occured. The new plates, one inch thick 316 stainless, would allow the estimated rod load of 20,000 lbs to be distributed over many square inches, creating compressive strength of less than one tenth the compressive strength of the fiberglass.laminate.

    Thirty jackstands were used to support the vessel while the keelstub was exposed for laminating and other repairs. Low load on the stands meant we did not risk damaging the boat for the last weeks where I needed access to the whole length of the stub to set its planarity.

     

    After the yard and I completed the vacuum bagging operation, I completed the rest of the keelstub by hand laminating anywhere from a half inch to three quarters of an inch of fiberglass on the stub. The end result was wider than the old stub, but the keel was wider as well. Several days were spent measuring angles and planarity of the new surface. The keel had to be perfectly aligned fore and aft, and also vertically, in order for the boat to perform as designed. The markings above, after the few days of hand layup, show the alignment marks, and the new hole location. I had no problems with the accuracy of the holes because a template had been built to match the new keelbolts. This template was used to drill the new holes. I ended up doing some grinding to fine tune the alignment, but it was very minor. The travelift was able to lower the boat right on the keelbolts after two minor adjustments to the keel alighment.

    Ready for the mast.

    After this picture was taken, sealant was applied to the new keel and the travelift lowered theboat to within a quarter inch of the keel. The next step was to torque all the bolts to spec. I did so with one of the yard owners, and the keel came up snug to the stub. A final torquing moved only five or ten degrees. This was a clear indication that we stretched the bolts to spec torque, but that the laminate was not yielding under compression.

    Three people were employed in the caulking operation, as well as I. The travelift operator sporadically, one carpenter and two people spreading the caulk. When the keel was torqued and brought to the interface, the excess caulk was cleaned up by two people.

    Multiple thin layers of fairing compound helps minimise turbulence. Since I used to race, I have a distaste for rough bottoms.

    CREDITS:
    Such a project would not have been possible without help from many great friends.

    Yann LeCun, Larry Jackel, and Alan Deeken who helped me bring the boat up the coast. Larry who helped in a number of ways on repairs.

    John Strauss who bought my C&C40 and helped me on numerous occasions in the refit.

    Seb Granier, Bob Malkemes, Gennady Malinsky, Larry Jackel, who dove head first to help me regularly with a number of projects from bottom paint stripping to wiring and fiberglassing.

    Bill Lockwood, who runs the best yard in New Jersey, and his crew of brothers, sisters, and employees. Simply they are the best machine operators, welders, fiberglass experts, machinists, storekeepers, and office workers, the nicest and most competent yard crew I have run into.

    Mike for his help in finding supplies.

    My family who supported me in doing this project.

    Rick van Hemmen, Naval Architect, for excellent consultations on the repairs

    Ed Dubois, Naval Architect for a superbly designed boat from 1991, and his help with the new keel, and willingness to do it, eventhough much larger designs are being contracted by his firm. Michael Benakis, the engineer who designed the new keel, for producing a great looking design that seems to work well

    Mars Keels, and especially Kevin Milne, for exceptionally short production time and good project management

     

     

    After a typical fiberglass workday. This is why I would prefer to avoid doing a project like this again, and why I have utmost respect for those who do this work for a living...