October 24, 2013 at 3:04 am #68805
Looking for some advice on a bulkhead repair job.
At some stage a bad leak on the port forward bulkhead has resulted in most of the plywood around the chainplate rotting away. In other words all the plywood from the hull and extending inwards past the fibreglass tabbing from the hull – about 4 inches – no longer exists. I discovered this after removing the port cabinets for re-varnishing.
I have two options – replace the entire bulkhead or replace part of it. I am trying to avoid having to replace the entire bulkhead as you all know what that entails.
My thoughts are to keep the fibreglass tabs as they as they line up with the chain plate (and they are well bonded to the hull), and replace the section of the bulkhead that has rotted away. The replacement plywood piece would be inserted between the tabs and glued in place. Additional mechanical fasteners through the tabbing would be added to improve mechanical bonding to the replaced bulkhead.
On the section where it joins the existing bulkhead I would add pins to increase the mechanical bond.
Considering that this situation has been there for a while, and that it has survived a Pacific crossing in this condition, I am assuming that my repair would be better than what I had.
Appreciate any comments / advice.
October 24, 2013 at 6:48 am #80235
I think the fix you have in mind would be fine, but you will have a very hard time inserting the new piece in as you described. I think if you cut back some of the tabbing on one side and leave a good 1/2″ still protruding from the hull and shorten the top of the new piece you could possibly jam the new piece in with healthy gobs of thickened epoxy. Don’t forget to “whet out” all the glued surfaces with un-thickened epoxy first and make sure the top of the new piece is coated also in case of future leaks. You can use some thickened epoxy to fair out some replacement of the tabbing you removed, but course some fiberglass mat replacement to the tab would be the best thing, although if it’s lasted this long no doubt the rest of the bulkhead is still doing it’s job. Not sure how you could possibly pin the new piece and still get it in but I wouldn’t worry about that side if it’s all contained in the locker. Make sure it’s full of thickened epoxy as is up against the hull and use a 2″ strip of say 1/2″ thick solid teak, or any decent hardwood to cover bulkhead to bulkhead joint possibly on both sides. You can screw, glue and bung that in for a clean look.
Not sure I made that clear, I hope I did. Good luck.
October 24, 2013 at 8:20 am #80236
Just as a matter of interest, replacing the bulkhead is not an option – it is wider than the companionway.
All good advice, and my course of action will be very much as you have described. The “pins” will not be required as I will cover the joint from the inside of the forepeak locker with a wide strip of hard wood.
When all the structural work is complete I plan to cover the bulkhead with “thin-ply”. Basically a teak veneer bonded to a thin backing that comes in sheet sizes of 2400x1200mm – just enough to cover both sides.
October 24, 2013 at 1:30 pm #80237
I agree with Ken, including that “some fiberglass mat replacement to the tab
would be the best thing.” As for the overlapping strip at the joint, I’m not
sure 2″ is wide enough. I’d prefer to see it 4″ or even 6″ wide, glued and
Silverheels, P-424 #17
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October 24, 2013 at 3:01 pm #80238
This is unfortunate indeed. Chainplate leaks are a continual problem and need to be addressed as soon as they are discovered. In addition to wood rot, water on and under the chainplate can cause crevice corrosion. I assume that you’ve removed the chainplate and inspected. There are a number of ways to caulk the chainplates such that water doesn’t get through the deck. This is best covered in a different thread. I use lap sealant for my chainplates. It never hardens so it doesn’t crack if the chainplates move a bit.
The load of the chainplate is supposed to be distrubuted across the entire bulkhead. No matter how much adhesive you use, you’ll never be able to attach a section of bulkhead with only glue. I think you should look at sistering the bulkhead where the seam is. After inserting a replacement piece, lap a piece over the seam and glue and fasten it down as best you can on both faces. You could use pressure-treated plywood, but glue won’t stick to newly manufactured pressure-treated panels. If they are a few years old, the pressure treating compound evaporates sufficiently for glue to stick. Marine-plywood might be a better choice.
I just had my chaninplates out for inspection last winter but I can’t remember exactly what’s in there. You might have sufficient access to the forward part of the bulkhead by removing the cabinet doors. If not, with care and a lot of work, you should be able to disassemble the cabinet front in the forward cabin to gain access to the forward face of the bulkhead. It would be a lot more work to disassemble the main cabin cabinet front. You should be able to gain sufficient access without doing that.
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October 24, 2013 at 7:13 pm #80239
Thanks for the responses and advice.
This weekend is the first long weekend when summer kicks off in New Zealand and most yachties head off for three days of sailing in the hauraki Gulf.
In the meantime I will have three days to sort this out.
Rich, I like the idea of sistering in the new plywood. I had some sheets of marine ply that were on the plan list for a hard dodger, but that will have to wait.
The repair job is formulating, and with the tidbits of good advice my approach will be along the following lines.
I am going to try and keep the existing fibreglass hull tabs as they are well bonded to the hull and I would rely on them rather than adding more glasswork to replace them. I will try and insert the new ply between them.
The current bulkhead is 20mm thick, and I will strip it back leaving a piece that is 10mm thick for about 6 inches or more. This will form the base for a scarf joint.
The first piece of 9mm marine ply will be inserted between the hull and butted against the bulkhead.
The second piece of 9mm ply will then be inserted between the tabbing on the hull and overlap the first joint to complete the scarf joint on the existing bulkhead.
Tor, On the inside of the forward cabinet, running the length of the joint plus, the overlapping strip – 6 inches wide – will complete the joint.
Since I will be replacing the teak veneer, a few fasterners through the joint and hull tabs will do the rest.
That is the plan, and adjustments will no doubt follow.
The chainplate, on first inspection looks good – no pit corrosion. Need to check for cracks. It may just be better to replace them with longer ones – next weekend!
Will post pics later.
October 25, 2013 at 12:04 am #80240
Sounds like you have a great plan using two different pieces of ply, I have no doubt it will be a satisfactory job. 🙂
August 4, 2018 at 8:33 pm #224348
I hate resurrect an old thread but I was wondering how this repair was finally done. Unfortunately I’m facing the exact same thing that you had to and will probably attack it the same way you proposed. Any insight would be appreciated.
August 13, 2018 at 4:35 am #224352
Apologies for the late reply.
I tried to dig out all the rotten wood between the tabbings which were attached to the hull with the plan of inserting new wood and using the existing tabbings for strength. It was very difficult digging out the old wood with the long tabs all the way to the hull and on hindsight, I would retain some of the tab it as it can be used to hold the new bulkhead pieces in place. I used a Black & Decker B/DKA900E powerfile belt sander to clear the old wood.
I did not replace the entire bulkhead. Just removed the rotten area and replaced with two pieces of 9mm marine ply. Any modern marine ply would be better and stronger than the plywood used. If I recall, the 9mm sheets were staggered (bulkhead side) and I bolted them to the existing bulkhead. Did this between the existing tabbings and the two 9mm sheets as well
Thereafter it was a matter of tabbing in the new pieces and fairing off. I also sealed off the top so that any water that does spill from the overflow pipe (should it not go to the deck) would not penetrate the new bulkhead.
Note that the bulkhead does not go hard against the hull. Use a piece of foam to provide a spacing.
You will also have to to open up the cupboard in the forepeak to add the tabbing to the “front” of the bulkhead.
The fairing off is because I added a new piece of veneer over the whole works.
I have some photo’s tucked away and will dig around and send then to you.
August 16, 2018 at 3:06 pm #224357
Sounds much like what I planned. I intend on removing the tabbing from the aft side of the rotted part of the bulkhead, cutting out the bad wood and like you using two pieces of staggered 1/2″ marine ply screwed and glassed to the old good wood. I’m planning on routing 4-6 inches for the offset. I will glass the forward side in with thickened epoxy to the old cleaned up tabbing then re-tab the aft side of the bulkhead with new glass. Once everything is in, I plan to fill in the myriad of no longer used drilled holes in the bulkhead and veneer the aft side of the bulkhead. During the glassing process, the holes in the forward side of the tabbing will be filled with thickened epoxy and when I install the new chainplate, I’ll just re-drill a complete set of new holes.
Tearout begins tonight.
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