Mast step truss, inevitably:(

Bob McGovern
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Location: Wyoming, USA

Re: Mast step truss, inevitably:(

Post by Bob McGovern » Wed Sep 03, 2014 3:27 pm

Not sure exactly what the truss is sitting on, Mark. Could be lead ballast; probably just another 5" of thickened polyester resin. The second resin pour, if you like, wouldn't have offered much if anything in structural or compressive strength. It seems like Albin used it to provide lateral support to the truss and (naively!) to isolate the mild steel from water. Which never works. :| There is a hose (limber tube?) poured into the resin, intended to transfer water from the V berth area down to the general bilge compartment. The truss itself is capped with FRP. What could go wrong?

It's a sailboat. Water will get everywhere, Albin -- including every part of the bilge, including down the sides of that encapsulated mild steel truss -- and now it is stuck there.

So yeah -- we'll need to replace the lateral stability function of the poured resin. Not difficult to achieve with epoxied wedges and fore-and-aft thru bolting. The laminates at the keel/hull transition are a full 1" thick and you can brace to them with every confidence. There will need to be positive drainage from the truss compartment, and some air circulation/inspection access wouldn't hurt matters going forward.

Every boat, old or new, production or custom, has a few real head-scratching features. The really big issues others have documented or I've found thus far with the Albin Ballad are the steel mast step truss; the un-tabbed main bulkheads; and the genoa track backing. We are attempting to address all three at once, which is a handful. But once sorted I think the boat will be good for another 40 years of reliable service. :)

MarkRyan1981
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Joined: Fri Oct 12, 2012 7:47 am

Re: Mast step truss, inevitably:(

Post by MarkRyan1981 » Wed Sep 03, 2014 3:41 pm

They got some many things right on the Ballad, I suppose they were bound to get some stuff plain wrong. I will wait until you have made good your repair sir, and then if our inspections give me any doubt, I will look at following your lead (and hopefully instructions :) ).

As the risk of taking this slightly off topic - is there a thread for the untabbed main bulkheads? Is this the issue of the bulkheads not being connected to the deck?

Bob McGovern
Posts: 281
Joined: Fri Oct 26, 2012 3:08 am
Location: Wyoming, USA

Re: Mast step truss, inevitably:(

Post by Bob McGovern » Wed Sep 03, 2014 4:28 pm

MarkRyan1981 wrote: As the risk of taking this slightly off topic - is there a thread for the untabbed main bulkheads? Is this the issue of the bulkheads not being connected to the deck?
Yes -- and you started it!;)

http://www.balladklubben.se/balladexcha ... f=8&t=3451

Albin used a fairly common production build method of glassing tabs to the hull, then bolting the bulkheads to the (one-sided) tabbing. Over time, the bolt heads compress into the plywood, or water intrusion causes the plywood to delaminate around the bolts, and the bulkheads can either tear loose or lever the tabbing off the hull. Generally such tabbing is chopped strand mat attached to the hull liner laminate, which is coarse roving. Not the best arrangement.

Quite a lot of additional strength can be gained by gluing the bulkheads to the tabs with epoxy or polyurethane adhesive (not polyester resin). Even more can be gained by doing that & then fully tabbing the opposite face to the hull for most or all of its perimeter -- what the person in your original post refers to as 'top hat' tabbing . Prevents the levering effect. Also supplies a much better bearing surface for the through bolts when reinstalled. Some of the smaller bulkheads & settee backs on our boat were tabbed direct to the hull, on one or both faces. For whatever reason, the main bulkheads were just bolted.

Tying the deck overhead to the bulkheads is my own personal fetish & may not even happen. It is mostly an issue if you lead halyards aft to the cockpit, which can cause the deck to pump like a diaphram. Various bracket and tie rod solutions offer & may be easier than tabbing.

I've nearly got the bulkheads ready to tab back in, as soon as the stbd side deck is skinned this weekend. :P Had to replace one piece of the big bulkhead, where either the head or chainplate leaked & rotted out the bolted area. The plan is thickened epoxy between bulkheads and original tabbing, with the bolts massively waxed & acting as clamps. Then we pop out the bolts (we hope!), tab the salon side of the bulkheads to the hull with lots of 6"w biaxial tape, and rebolt with large washers under the bolt heads. Most of the ugly will be hidden by furniture.

If your plywood looks undamaged, I bet you could get away with a 2 hour upgrade that would solve much of the problem. Some minor furniture disassembly will reveal most or all of the bulkhead bolts. If you pull those, put large SS fender washers under the heads (perhaps with a dab of thick epoxy on the bulkhead side of the washer, to fill any plywood dents), reinstall, and use Nylock aircraft nuts on the V-berth side, much peace of mind would be gained with minimal mess or disruption. When I was grinding a couple thru-hull penetrations where the head fittings used to be, the grinder's vibration made a half dozen conventional nuts unscrew themselves and fall off. These were bulkhead and chainplate fasteners ... kind of a big deal. :shock: Not something you want shaking loose in the Medway.

MarkRyan1981
Posts: 165
Joined: Fri Oct 12, 2012 7:47 am

Re: Mast step truss, inevitably:(

Post by MarkRyan1981 » Wed Sep 03, 2014 4:51 pm

Gosh, that was some time ago! A cracking response then and now. I suppose glueing the bulkheads back to the tabs would require their removal and given my limited facilities and time I'd like to avoid that. So I could potentially remote the bolts (guessing not wise with the rig up!?), 'top hat' the other side of the bulkhead, through bolt the whole affair with SS fender washers, Nylock nuts and a dab of that beautiful stuff epoxy on the plywood side and we will be safe as houses? I read your answer here http://www.balladklubben.se/balladexcha ... f=8&t=3471 with keen interest - my late father was a shipwright, I am not (IT manager), so it makes for interesting reading!

And once again, when it comes to the mast step (apologies, I've somewhat hijacked the thread :oops: ), I will follow your progress and look to emulate your solution (so long as your mast stays pointing in the right direction :))

MarkRyan1981
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Joined: Fri Oct 12, 2012 7:47 am

Re: Mast step truss, inevitably:(

Post by MarkRyan1981 » Thu Sep 11, 2014 3:58 pm

Any updates Bob? :D

Bob McGovern
Posts: 281
Joined: Fri Oct 26, 2012 3:08 am
Location: Wyoming, USA

Re: Mast step truss, inevitably:(

Post by Bob McGovern » Thu Sep 11, 2014 4:44 pm

Whew. Second side deck is re-skinned, just ahead of the snow tonight. :cry: Working overhead like that is not especially difficult -- but it is slow, and tiring. I'll post some updates in the Photos section here under the "Rebuilding Fionn" subject heading. Very happy with the first bulkhead glue-ins; the rest will need to wait until Sunday, if it warms up a little.

MarkRyan1981
Posts: 165
Joined: Fri Oct 12, 2012 7:47 am

Re: Mast step truss, inevitably:(

Post by MarkRyan1981 » Fri Sep 12, 2014 8:14 am

Ah I saw on your thread you had stripped the underneath of the side deck where the genoa track ran, pretty extreme stuff. I look forward to seeing the photos!

MarkRyan1981
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Joined: Fri Oct 12, 2012 7:47 am

Re: Mast step truss, inevitably:(

Post by MarkRyan1981 » Mon Sep 15, 2014 10:35 am

Funny old question, any chance you could take some photos of the 'hole' left by the truss now you have removed it? Did you end up removing the small bulkhead aft of the truss :)

Cheers Bob, hope the weather has warmed up some!

Bob McGovern
Posts: 281
Joined: Fri Oct 26, 2012 3:08 am
Location: Wyoming, USA

Re: Mast step truss, inevitably:(

Post by Bob McGovern » Mon Sep 15, 2014 3:57 pm

Sure, I'll snap a couple photos of the cavity today. I did cut out the thin bulkhead between the truss and the main bilge, mostly because it made the demolition work much simpler. if removed with care, you could just glass the partition back into place later. We'll likely fashion a new one from phenolic, using the old for a pattern.

Later: photo may not be helpful. It was getting a bit late in the day for good pictures. Post is in the way but needs to stay there for the moment, sadly. Anyway, the dark patch at the bottom of the well is where the truss foot sat; I think that's several inches of solid resin beneath it. Truss thru-bolts to the floors/bulkhead where indicated. Was a bit surprised and amused, when drilling thru that bulkhead yesterday, to find the center of it is metal -- looks like steel, maybe 4-6mm, maybe mild (magnetic). No sign of rust, anyway. And rather a nice thing to bolt your re-habbed bulkhead thru.;)

Image

MarkRyan1981
Posts: 165
Joined: Fri Oct 12, 2012 7:47 am

Re: Mast step truss, inevitably:(

Post by MarkRyan1981 » Tue Sep 16, 2014 8:06 am

Thanks for the photo, I suppose the resin that surrounded the foot was bonded firmly to the hull so needed grinding back until you got to the fibreglass? What did you use to chop out the sole with? My first guess would be angle grinder, but those edges look too straight - circular saw (or a very steady hand!)? So that bulkhead has a center of steel - they certainly built the boats heavily and you feel that when you sail her!

What will you do with the sole once you have put the new mast truss back in? Use the chopped out piece as a template to fibreglass up a new insert and then glass it in?

This may be an exciting job for next year, I need some of that rare commodity of time!

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