“Hey guys my boat is sinking”

Brewer 12.8 Centerboard System Failure

Michael Smolek, Hawk

February, 2017

 

Warning:  For you boat owners with centerboard Brewers, I strongly recommend that you take a careful look at the stainless steel tube and plate system that contains the c/b pendant.  Pay particular attention to the underwater section that is attached to the front of the c/b well.  If your system is like my 1984 Brewer 12.8, it is buried under the cabin table cabinetry, down in a narrow section of the bilge between the water tanks.  It is barely visible, much less accessible in an emergency.  Until recently, I had really tried to ignore it because I couldn’t see it very well, and I didn’t understand how it was constructed.  That changed in a dramatic way recently when re-launching Hawk after a year-long refit of (almost) everything underwater.    The stainless steel tube system for raising and lowering the c/b was not part of the original refit plans, because my thought process was:  well its’ been good for over 30 years, so it is probably fine.   Mistake #1.     

(Note: This SS pendant tube assembly is not to be confused with the vertical fiberglass tube located in the engine compartment which houses the c/b stop line that sets the fully-extended depth limit of the c/b.    BTW, it is important that this stop line be in place because if not the board can be extended too far and can damage the front of the board where it hits the forward end of the centerboard trunk.  This is one of the reasons that I had to remove the board; to repair previous board damage from not having a stop line rigged when I purchased the boat.)

Rushing Waters—WTF!   After the marina crew lowered the boat into the water for the first time after the refit, the distinct sound of lots and lots of water rushing in got my attention immediately.  A quick check revealed that none of the seacocks, stuffing box, transducer and sea chest that I had worked on was the source of the waterfall sounds. “ WTF! Hey guys my boat is sinking!”   A frantic hand search into the bowels of the bilge under the table quickly revealed that the flood water was coming from around the SS c/b tube, where it joins the front of the c/b well.  If the boat had been at sea  or even in a slip and had not been  still in the travel lift slip, I am convinced it would have sunk because of the problem of reaching the source of the leak, the amount of water flooding in and the difficulty of stopping or substantially stemming the flow.  The water quickly outpaced the bilge pump and the water had almost reached the bottom of the engine pan in the few minutes that it took for the travel lift crew to re-start the travel lift, pull the straps back up to the boat and get the keel out of the water.  We discovered that the SS c/b pendant tube had completely separated from the SS vertical plate at the weld, at the point where the assembly bolts to the front of the fiberglass c/b trunk. 

Disclaimer: While I assume that the system for raising and lowering the c/b on the Brewer 12.8 and 44s is pretty much the same, I don’t know that for sure.  I have number 7 of the original production run of these boats (Hull #240), so perhaps the factory made improvements in the c/b systems of the later 12.8s and 44s, but I don’t know anything about that.   I know that some Brewers have a separate access hatch above the point where the tube attaches to the c/b trunk while mine is completely under the table cabinet.   I will describe how mine is put together and you can decide if it is relevant to your own Brewer.    (I do know that there was work done on the c/b itself by some previous owner; such as bulges added on the sides of the board to limit the well-known board flopping/thumping.   Also the original SS pad pendant attachment fitting on the top of the board had been removed and replaced with a simple and reliable hole drilled through the lifting arm of the board for the pendant.)

Diagram

Diagram left by a previous owner in the ships papers (Thank you!!)

 

Detailed diagram

Detailed diagram left by a previous owner (Thank you again!!)

Description: The stainless steel c/b pendant tube is in two sections with a joint that is enclosed in hose with two hose clamps.  The joint is located inside the table cabinetry, hiding behind a drawer.  There is a straight vertical section of tubing that extends down from the overhead.   This upper section meets up with the lower section of the tube which has a large-radius 90 degree curve that turns horizontally to the front of the centerboard well where it is held in place by several plates, one welded to the end of the tube.   Separating the two tube sections requires removing the hose clamps, sliding the hose up or down.  Presumably the connection point between the two tubes is above the water line, but I haven’t verified this.  Since most of the lower section of the tube system is well below the waterline, disassembly of the lower section must be done when out of the water.  It is not possible to really work on the lower section of the system without getting the table out of the way somehow (chainsaw?).  The table cabinet has to be disconnected and, unless the mast is out of the boat, secured over head .  This involves removing several devilish U-bolts that attaches the tube to the inside of the table cabinet and unscrewing the table from the cabin sole and tying it up, somewhat out of the way.    You are then working down through small holes in the sole.

Access

Access to the c/b tube with the table removed and after a sawzaw made it slightly larger.

The aft end of the lower curved tube section is welded to a 3½” x 5” SS plate (3/16” thick) with six holes, three along each side, which mounts to another matching SS  3/16” plate which in turn is bolted thru the fiberglass c/b trunk ( Figure 2.)  The match plate has six ¼ inch studs welded in place facing forward for the 6 holes that go through the holes in the plate that is welded to the lower curved tube section .  Between the two plates was a 1/8” rubber/neoprene gasket and caulking.    There are sheaves/rollers for the centerboard pendant mounted on the plate of the lower curved tube section (sheave box). The bottom sheave, which takes most of the load, is approximately 2” in diameter and the upper sheave is smaller.

Sheave 

Sheave box with 2 inch bottom sheave and a smaller upper sheave.  This sheave box extends into the c/b trunk.

The match plate has a small vertical rectangular hole (1 5/8” horizontal x  3 ¼” vertical) in the center through which the sheaves that are mounted on the lower curved tube plate fit.   In addition to the studs pointing forward, the match plate also has six countersunk holes (two along each side and one at the top and bottom) which are used to thru-bolt it aft onto the fiberglass c/b well.  Between the match plate and the irregular surface of the fiberglass c/b well was a fairing layer that provides a precise seal and alignment surface between the rough c/b well and the match plate. Although it looked like another gasket, it wasn’t, so don’t try prying it off or hitting it with a chisel and hammer (Mistake #2).  

The tube of the lower curved section and the plate had separated at the weld because of 30+ years of corrosion.   A small 45 degree gusset had been welded to the bottom of the plate and tube, but that had also corroded and failed.    The photoshow the corroded condition of the end of the tube which we cut from the longer curved tube in our first attempt at repair.  The SS pins holding the sheaves in place were also discovered to be over 50% corroded.

 

Parts

The nuts that attach the match plate to the boat are on the inside of the c/b trunk and access is through the ca. 1 5/8” x 3 ¼” hole in the match plate and the comparable hole in the fiberglass c/b trunk.  This is a good thing and a bad thing.  The good news is that the c/b does not have to be removed to work on the SS pendant system and it can all be reached from inside the boat.  So you do not have to work under the boat and try to reach to the top of the c/b well, which is probably impossible anyway.   But the bad part is also that the SS tubing system has to be dismantled from inside the boat, working down in a narrow bilge on your hands and knees with a very heavy table cabinet dangling overhead.    It was not much fun removing the six 30+ year old SS nuts on the flat-head slotted countersunk bolts slathered with 3M 5200, working through the small hole, on your hands and knees.   We had to bend a box end wrench in order to reach into the narrow hole and hold the nuts on the inside of the c/b trunk.  It is almost impossible for more than one person to work in the confined bilge space, but with some contortions it was possible on a limited basis and, at times necessary, to have four hands to apply the force needed to get the system disassembled.   Yachting is such fun.

Yet another Mistake: Our initial attempt was to repair the curved tube-to-plate weld joint.  This turned out to be a mistake.  We cut off two inches of the heavily corroded SS tubing, added two inches back and re-welded it to the plate.  We noted that the SS of the plate and hardware for the turning blocks was degraded but thought it was still structurally sound.  We re-installed the repaired plate and tube and tried launching the boat again only to discover that there were very tiny pin hole leaks in the metal plate that wept.  The plates were metallic Swiss cheese.   We probably should have guessed this because it is a prime location for anaerobic crevice corrosion.   Out came the boat again.  We began calling it boat dipping, rather than launching.  Because of the uncertain condition of all of the underwater SS metal we decided to replace the entire lower section of the system.

New lower tube

New lower tube and plate attached to the front of the c/b trunk.  We added gussets to the top and bottom on the plate to tube joint for strength.  

Improvements:  When making up the new plate and tube, we added a gusset on the top and bottom of the tube to support the weld on the plate.  This welded connection between the plate and tube is subject to loads all the time that the board is up in the trunk or partially deployed.   The significant force that it takes to keep the board up in the c/b well exerts substantial loads on the entire system.  In a violent sea the dynamic forces exerted on the system holding up the board must be significant.   The heavily tensioned pendant is trying to straighten out the curved tubing, so the plate-to-tube weld is under tension at the bottom and compression at the top of the weld.  The added gussets on top and bottom help address this asymmetrical loading of the welded joint.  I believe there to be minimal side loading, so I didn’t feel that additional gussets on the sides would provide any benefit.

Curved tube

Curved tube attached by a U-bolt assembly to the mast base to counteract tension of the pendant.  I added an extra piece of curved oversized tubing as a saddle over the pendant tube to spread out the load vs point loading at the U-bolt.

To counteract the force of the pendant trying to straighten out the lower tube, and to reduce upward loading of the welded joint, there is a U-bolt assembly on my boat anchored to the nearby mast step to a point on the radius of the curved tube. This U-bolt assembly keeps the force of the c/b pendant from straightening out the curved tube when the pendant is under tension (which is most of the time).   I didn’t like the fact that the U-bolt put a single point load on the tube, so we made up a larger diameter curved SS saddle that fits over the outside top of the tube to distribute the load over a much larger area of the curve, rather than at a single point. 

Conclusions:  So there is now a brand new lower plate and tube section and match plate on Hawk that doesn’t make waterfall sounds, leak or weep.    It is not entirely clear why the tube assembly decided to give up at this time, but I am so glad it took that opportunity while still in the travel lift slip.   The failure at this point in time is probably related to the forces exerted on the system getting the heavy board out and reinstalled during the refit, but it was a sinking waiting to happen.  

 Before I purchased Hawk in 2014, it lived its years in the waters of south Florida and the Bahamas, a pretty severe corrosive environment.   Other boats may not have the same level of degradation,   however, I would advise that Brewer c/b boat owners take a careful look at the c/b pendant tube, particularly where it attaches to the plate at the front of the c/b trunk.  If you see corrosion or evidence of leakage, I would seriously think about removing and thoroughly examining the lower tube assembly.   Unfortunately removal is not an easy task at all.    The c/b tube on my boat was not connected to the bonding system and this has been remedied.  (In fact,  a check with a silver/silver chloride reference electrode confirmed that only the bronze seacocks are connected to the bonding system.)

I would suggest that you also consider how you might stop water from coming in if the joint begins to leak.  If there is a total separation at sea, I am not sure how to slow or stop the flow.    Perhaps underwater epoxy would help stem the rising tide, but the movement and forces of the board pendant under tension inside the tube in a seaway would probably make achieving a good seal very difficult.    The first thing I would do would be to lower the board completely  taking the load off the pendant tubing system and then try to effect a temporary seal.    After my experience, and despite a new assembly, I intend to keep underwater epoxy nearby.    

Acknowledgements: Fortunately when the system broke I was at a tiny boatyard with a small staff of highly skilled craftsmen, located between Annapolis and Solomons Island, the two premier sailing centers in the Chesapeake. I can’t imagine how bad it could have gotten if this had happened at a remote location.   I only have good things to say about the staff of Flag Harbor Marine Service (John Little, owner). There was also a local welder/artisan/sailor (Joe Wysong)  who dropped everything in order to first repair the old tube, then fabricate a complete new  plate and tube and match plate;  all at an incredibly reasonable cost.