Repairing aft bulkhead and cross beam

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wwaites
Posts: 4
Joined: Tue August 11th, 2020, 8:33 pm
Location: Granton
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Repairing aft bulkhead and cross beam

Post by wwaites »

Hi all!

After pandemic delays, Hale Kai is now ashore at Granton and I've set about getting to the bottom of the rot that afflicts Golden Hinds where the bridge and main decks meet the aft bulkhead. It looks like a relatively major repair because of poorly done prior attempts at repair. The port side, in the wet locker is in worse shape than the starboard side by the chart table.

Cutting away the bad bits of bulkhead exposed the cross beam that runs the whole way across, under the companionway. It is damaged at the extremities. At some point, someone with good intentions but questionable judgement fitted a substantial Henderson bilge pump directly under the companionway. To do this, they cut out a significant part of the middle of the beam, weakening it.

The best plan at this point, though I am very much open to suggestions, seems to be as follows:
  1. Clean up the beam as much as possible, including removing the fibreglass that covers the aft part in the cockpit locker and pilot berth. The fibreglass has already separated there in the pilot berth so is doing nothing useful.
  2. Saturate the wood with two part clear penetrating epoxy sealer (CPES) both on the surface and by drilling holes.
  3. Laminate in 25mm iroko to fill in the gap in the middle.
  4. Possibly cut a slot straight down the middle and glue in an L- or T-shaped piece of 6mm thick aluminium
  5. Sister 25mm iroko plank on both fore and aft faces, epoxy and bolt through
I think that #4 is probably only feasible if the beam is actually straight, I suspect it is slightly curved upwards by about about a centimetre at the centre. I'll verify this with a laser level today.

It's still an open question whether to replace the entirety of the aft bulkheads or just sections. Less than 50% of the ply seems to be sound.

Much of the problem at the deck interface seems to come from the fibreglass covering the bulkhead not really being joined to the fibreglass covering the deck to make a watertight seal. Instead it seems like these were done separately and the joint is made with some kind of structural sealant which has deteriorated over the years.

Well. Those are the plans for the summer anyways. Thoughts and suggestions very welcome!
wwaites
Posts: 4
Joined: Tue August 11th, 2020, 8:33 pm
Location: Granton
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Re: Repairing aft bulkhead and cross beam

Post by wwaites »

Well. The starboard side of the beam is now completely accessible.

The end, where it meets the hull has a gap forward of a few mm that was filled with some sort of filler of unknown kind. The aft side touches the hull. There had been a similar substance on the front of the beam where it was against the glassed face of the bulkhead. The filler is grey and had the consistency of mud. Does anyone know what it is or was? In any event it's gone now.

The small gap may be purposeful to allow the hull to flex slightly. The mast is off now and it could be that with the pressure of the rigging it would close up. Current thinking is to fill it with an elastic substance, perhaps sikaflex, to allow some compression but not leave a void. That is, if the gap is there by design.

I can't seem to upload photos here, but I've put a photo of what I'm talking about here: https://halekai.uk/gallery/aft-bulkhead ... am-gap.png
Some of the grey mud is still visible on the left immediately above the fibreglass of the deck as well.
wwaites
Posts: 4
Joined: Tue August 11th, 2020, 8:33 pm
Location: Granton
Contact:

Re: Repairing aft bulkhead and cross beam

Post by wwaites »

I didn't realise that it had been a year since my previous message. The short version is that the cabin and parts of the deck were rebuilt in time to dismantle the tent because of the high winds that we get here starting in November or December. The longer story is...

The plan went more or less as I said. Scarfed in a trapezoid of iroko to repair the transverse beam and give it some stability, saturate it with CPES and some filler where needed. Then, for no real reason other than we happened to have some carbon fibre around that was just about the right width cover it with that. Yes, this is a Golden Hind with carbon fibre reinforcement ;)

Image
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Next was entirely removing the bulkheads themselves and making new ones. I did the starboard side with the method of joggle sticks, which worked very well. My friend, who is an extremely talented engineer, reasoned that if he were building a boat, the port side should be symmetrical and used my work as a template. That left some gaps to fill when fitting it but the error was not fatal.

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The bulkheads fit and tabbed to the hull with fibreglass, a sister of iroko fixed with adhesive and coach bolts makes for a nice look. There is a second sister, in three sections, behind, so the old beam is essentially sandwiched. I think this should be plenty strong.

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Outside, a layer of fibreglass, this time joined to the bridge deck. It is a mystery why the bridge deck was originally not joined in a watertight way to the cabin. I wish I could ask Terry Erskine. The companionway frame is reclaimed teak that used to lie on the bridge deck. The step has been built up after this picture was taken (so that water doesn't go into the cabin under the washboards) but I don't seem to have a recent enough picture of that.

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That was a big job. Now all of the others that are necessary to make Hale Kai properly seaworthy again that I would have thought were big seem small in comparison.
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