What follows is an edited compilation of discussions relating to deck beam problems from the public-list server.
The mast sits mainly on the after part of the beam and usually twists back leaving a depression on the deck behind the mast. That's one way to tell it you have a problem, or the start of one. Not being able to use the door to the hanging locker to close off the forepeak is another. The glue that Whitby used to laminate the beams gives up over time and the beam itself delaminates causing it to crack [sometimes dramatically] and happens mostly to boats that are raced hard in heavy weather with excessive amounts of sail. But the beam can crack even in a "cruised only" boat once the glue gives up.
Pre liner boats
I'm not a structural engineer, but I'd bet that a combination of the two plates epoxied to the beam and through-bolted to each other will provide plenty of strength. Bruce Rankin developed this fix and I have great faith in his engineering abilities. This cure has been done on well over 100 boats, and no part of the procedure is technically demanding, just a little messy at times.
Jack the beam into position using a house jack or the like,through the opening in the floor to bear on the keel (not the floor). You could squirt some epoxy between the delaminated pieces before jacking up the beam, if you want. I can't see how it would hurt. If the beam has deflected to the point where it takes days to gradually get the beam back into position, relaminating the wood may not be an option. It must be correspondingly jacked when installed, you can drill the holes through the beam with the brace in final position.
I suggest getting the plates cut by The Washington Aluminum Company. . The plates are made from 6061 grade aluminum and are cut using a computerized water jet cutting process and therefore a very even cut. I installed them, and found that I had to do some "final fit" like rounding edges and corners.
This was done easily with a 3" belt sander (others have used a 3 ½ inch angle grinder, which also can be used to cut off bolts). They have the exact template on file for the Alberg Fix. It took three days for them to ship to me here in Chicago. The number there is 410-242-1000. Dial extension 301 and ask for Kirk. No point in reinventing the wheel here. Cost was $257 including shipping to Chicago. (Update, in early 2005 the price was reported as $295.)
The plates are 3/8" and I coated the beam with West System Epoxy with 407 to increase the bond before bolting everything together while the epoxy was still wet. I use the two-part West System etching solution on the aluminum to improve the bond with the epoxy.
Some installations use a series of through bolts through the new plate;some just use the existing bolts (the holes) on either end of the beam-usually going up one size in diameter. Predrill one of the plates off the boat. This will prevent 'dimpling' which can diminish the flush fit. prepare the surface of the wood beam and score the aluminum plates to take a good coat of West epoxy prior to clamping. Our hole placement was determined by guestimation.. I placed the majority of the bolts through the center of the beam (high and low). Using a drill press to predrill the first plate makes an effective template when later using a hand drill to run through the existing beam to the second plate. Make sure that there is clearance from the top of the plate to the underside of the deck, to avoid deck cracking when the beam flexes under load. That space can later be filled with silicone caulking.
I ran out to the edge of the plate as far as I could and still get the drill to go through . Important equipment was the 14" drill bit, brand name "The Aggressor." Total of 10 holes and bolts. I used 1/4 inch stainless steel bolts with hex nuts. Using cap nuts makes for a more finished look, but the bolts will have to be cut off after installation. Using bolts also makes convenient studs to mount wire straps on. Others have used 6 inch shouldered bolts, but the thread needed to be run down an extra 1/4 inch or so. If you are going to cut off the bolts, run a regular nut down the thread first, so if the thread gets buggered, taking the nut off will straighten it out.
This procedure covers up the numbers on the main beam required for documented boats, They will need to be permanently etched into the new aluminum.
Boats with liners
I am in the process of repairing the mast step on #499, built 1972. I believe there is a metal support beam imbedded in glass, but it is nearly on line with the aft edge of the forward hatch. Down below, this would be the very edge of the v-berth, it should look like a two to four inch bulkhead that spans the ceiling between the head area(port side) and the foul weather gear locker (starboard side). Take a look at the photos of the deck opened up at the mast step: http://alberg30.org/maintenance/HullDeck/MastStepDeckRepairs/ While routing around, I encountered no metal support beam, so it must be right at the edge of the hatch.
Like my boat, I suspect you have compression at the mast step, a symptom wholey un-affected by the integrity of the support beam. What's causing your mast to sink is compressed or damaged core. Bear in mind that the only reason I attempted to fix this problem was because the doors down below where getting stuck because the ceiling was sinking. I believe that the mast step has enough strength, even with the damaged core to support the mast under reasonable tension. Having routed out quite a large area, I can tell you that the damaged area was really very small, maybe 12"x 8".
If the deck isn't compressed that much, I'd leave it for a while. I waited over a year to repair mine. After removing the mast and making the repair, the deck sprang right back into place. Truly amazing. Consult anyone of the maintenance manuals for repair options. The most recent version has several articles discussing repairs from the top down, the bottom up, etc. Anyone who discounts the strength of the deck, even with damaged core, should don a pair of safety glasses and watch you try to cut into the deck. Its a serious job, and even ruined core has plenty of strength.
If I had to do it again, I might consider repairing from the liner side up, it would leave the deck intact and save some cosmetic work.
We did at one time have wet core material in the vicinity of the mast step. The original owner had drilled two holes in the deck, one for the mast wiring and one for the antena cable . These were not sealed properly and you know the result. Also water entered the core from the forward hatch hinges. About 5 years ago I repaired the area by opening the holes in the deck to about 1 1/4 " Dia. I only enlarged the holes at the deck level, I did not drill thru to the liner. I also removed the hatch and cut away the deck under the hinges. Then using homemade tools, 3/16" and 1/4" Dia. rod 1 foot long bent sharply at one end and ground to a sharp chisel point I was able to reach between the deck and liner a remove the damaged core. Then using a chalking tube I filled void with epoxy thickened with high density filler. The hinges completely covered the repair so there was no cosmetic work to be done. On the liner under the hinges I epoxyed stainless backup plate for added strength.
The holes I repaired by making bronze tubes approx. 5/8' O.D. x 1/2" I.D. long enough to reach from the liner to 1" above the deck. At the deck level 1' from the end there is a 1 1/4" dia. flange that hides the hole. These I epoxyed in place. Also the top ends of tubes have external pipe threads so they can be capped off during winter storage .
Issues
The only time you need worry about stainless/aluminum corossion to any degree is when the parts are in contact with saltwater, usually, hopefully, that's outside the boat. To minimize this I always use a sealant, caulking, when assembling aluminum parts with stainless bolts on the exterior of the boat.
Corrosion due to dissimilar metals will occur any time the metals are in contact; the corrosion will simply happen more slowly in a dry(er) environment. There are several things you can do, none of them good--like use nylon washers and bushings to separate the metals, or use a corrosion inhibitor. In any case, the aluminum will corrode visibly first. The stainless will also corrode--but you will have trouble seeing it.
Well, there has to be some moisture (or something equivalent) for the ion transfer that results in the corrosion. I think that if you keep the beam dry, you won't have any significant problems. Painting it will also help, as well as make it look better.
People who have contributed:
- Joe Tokarz, #499 "One Less Traveled"
- Tom Swift, #222
- Dan Sternglass, Watcher of the Skies, #201
- Mike Lehman, #505
- Mike Grosh, #220