View Full Version : Sagging Mizzen Repairs?
12-09-2003, 03:29 PM
Wooden Boat Masters,
I beg your thoughts on my latest challenge.
Well, I decided to tackle a "little" rebuild of some cockpit rot on Erica (32' Atkin Eric Ketch) only to find that it had been repaired at least once before badly. The plywood panels rotted, but that seems straightforward. The real challenge that has me stumped is how the Mizzen has set in the cockpit.
Just under the base of the mizzen are 4 oak beams, 2" x 3" or so running athwart (sp?) the ship. These beams sit on shelfs bolted to the frames, and are also bolted together. In eyeballing the situation, it appears the beams have sagged about 1/2 to 3/4" due to the weight of the mizzen and/or tensioning of the shrouds. The beams sagged enough that they now rest on the Port fuel tank. This likely opened gaps up in the cockpit and probably led to the water intrusions & rot I'm fixing. In addition, the deck beams around the cockpit are showing cracks where bronze tensioning bolts lead from the beam to the cockpit floor, so I doubt they are bearing any stress.
My first thought is to, ah, carefully, jack the mast up, then reinforce these 4 mizzen support beams with some stainless or bronze or aluminum angle iron. I don't think I can get the beams out or replaced without a lot of tearing and splinters, and we're in a slip, not a yard. Anyway, anyone dealt with this sort of creep in a old boat? Is it better to reinforce as-is to prevent further sag, then rebuild, or should I try to get things back in the right places first?
hmm..have photos, but have to post somewheres
thanks for ideas,
12-09-2003, 03:47 PM
whoops - meant ideas on fixing rather than posting photos (although I'll have a crack at that shutterbug site - thanks!)
I knew that, I just want to see pictures of Erica :D
12-09-2003, 06:50 PM
So, the mizzen was stepped on the cockpit floor with no compression post underneath? Sounds weak, so maybe I missed something. But if that's the case, install a compression post under the mast onto something solid to spread out the load. You might have to build something here, a long footprint, if she's a fin-keeler with no real structure underneath. If there is keel or deadwood under there, no problem.
Otherwise perhaps you can just double the timbers and not tighten the shrouds so much, but even so it's only a matter of time until it sags again.
12-09-2003, 07:12 PM
what Dave said. It doesn't sound like your boat was designed for a mizzen?
12-10-2003, 04:30 AM
What they both said. But you might try a screw jack under there for a few months, giving it another turn every week or so, and see if you can jack those beams up a bit before putting in a permanent compression post. But s-l-o-w and steady is the watchword.
12-10-2003, 06:11 AM
I faced something like this on the first boat I lived aboard - a 35' Garden ketch. Tried improve at first but eventually - at the mooring and all hand tools - removed and replaced all of the bridge deck and beams, most of the cockpit beams and all of the cockpit sole. I could not put a compression post straight down under the mizzen step as would run into the prop shaft. I really beefed up the frames under the step from the original three 2x2's to eight, giving 4" total depth.
From what you say about the tanks, that might not be an option for you unless you land the lower course of frames on something that comes up on the inboard side of the tanks. If you do that, make sure that the verticle timber lands on something that's spread over several frames.
The mizzen should not be too highly loaded anyway.
12-10-2003, 08:40 AM
I think the answer to your problem depends on how much trouble you want to go to, really, as evidenced by Mr. Ian's comments.
You could rebuild the entire structure. That would certainly fix the problem, especially if you did a neat trick I saw with antique beam repair guys and routed out a hole in the center of the beams and dropped in epoxy encapsd in steel rebar. I've seen 12x12 and larger timbers over 100 years old fixed this way, it is essentially invisible (since you can do it on the unseen side) and its really simple to boot. For smaller timbers you could just use smaller rebar. The idea is to get the steel in there to prevent bending moment, and use the epoxy a a load transfer medium.
You could repair the problem and add some strength. This would take less effort overall. You could remove the mizzen, sink some screw eyes in those timbers and jack them up slowly till they conform, then you could just slather on a goodly amount of pine tar and screw down long 1/4" plates of the metal of your choice, but bronze being the best for corrosion, to hold and strengthen the beams. Or you could do the epoxy encapsd steel rebar thing too.
You could remove the fuel tank, clearing out the area beneath the beams in question, then using screw jacks to level her up without having to remove the mizzen. Once in the right place, you could lay in some metal or black locust backing, depending on your preference, to hold her in place.
So you have a lot of choices. Really it all depends on how you want to handle it. Personally, if my mizzen was resting on a fuel tank I would move the fuel tank permanently and put in a compression post under it, or a significantly sized and cambered metal support beneath it which was braced and attached to at least 2 frames if not more.
12-10-2003, 01:41 PM
Thanks for the input!
The Eric design was for a ketch with a cutter alternate, and Erica's built to W. Atkin's plans: so there's no mizz. compression post below because the engine is just below the cockpit. I was trying to assess if it's possible to put some support between the cockpit and keel, but there is a lot of mechanicals down there with exhaust, fuel tanks, strainer et al, and no real place to stick a compression post.
I'd replace the beams and all that but *man* that is a can of worms I don't want to open yet, heck, I'm trying to avoid removing the miz.mast! Down side of California slips is one can't really do much (visible) work while in the water, so should I start pulling up deck, removing mast..I'll be on the hard in an environmentally controlled area at about $40/day. Right now I'm hiding under the boat covers!
ok, no pictures available here at work, but I will upload some tonight. For a small view, check my profile, I've got a photo of Erica there.
12-10-2003, 11:52 PM
Is the mizzen directly above the engine, or just above the transmission or the driveshaft? I'm wondering if you can make some sort of brace that splits and comes back together:
12-11-2003, 10:56 AM
Shoot, my advanced graphic didn't make the translation. But you probably get the idea.
My thought too Dave, I got your idea. ;)
12-11-2003, 12:48 PM
If you need a stealthy installation to keep the neighbors happy, you could have a steel brace welded up to whatever shape you need to clear all the other parts, and pop it into place in one fell swoop.
12-12-2003, 06:38 AM
Better a wooden structure for three reasons:
More consistant structure with the rest of the boat; and
If you're actually good enough to make a pattern for a steel piece, you can do the same in wood but with wood if you've a wee error you can trim.
It is hard to work in a marina where they have rules against real people. We once had a complaint about spreading sanding dust on a neighboring boat. The problem was, we'd not been doing any work on the boat the days in question, which the complainer knew perfectly well since they lived aboard also. We were off at day jobs. Took a lot to get them to realize it was that yellow pollin we get in the spring.
12-12-2003, 10:22 AM
based on the suggestions, all good, I'm probably going to put some metal around the beams since it's got a better strength to volume ratio which works in the tight confines of the area under the cockpit.
Unfortunately the base of the mizzen is dead centered over the ol' Sabb 2G #2 cylinder, limiting the compression post options. The double-ended hull positions the big mechanical lumps forward, and there's about a 4' prop shaft to reach the sternpost. (another repair pending...but that's a whole 'nother post)
ok, I really apologize for not getting some photos up for clarity but it's Friday finally...
12-12-2003, 10:39 AM
I've reinforced a mast step by sandwiching the original wood with steel. I can't figure out how this could be done without unstepping the mast, however. If it has sagged to the top of the fuel tank, it should be at least allowed to return to a proper shape first.
12-19-2003, 07:12 AM
What a neat boat! I bet if you spent less time contemplating the bottom of your beer mug you'd bust out that mizzen in no time.... :D
[ 12-19-2003, 08:16 AM: Message edited by: jkoutras ]
12-19-2003, 07:20 PM
Ok, great suggestions and for those not tired or bored with this thread I've posted photos finally online:
so you can see what I'm dealing with
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