H23 chain plate bulkhead replacement - material?

[isaksp00]

I just saw yesterday that my stbd chain plate bulkhead failed (again). The first time, the plywood had rotted out; the chain plate and cover had never been sealed properly and water intrusion killed the wood. I had to repair it on the water, by using the main halyard to serve as the stbd stay temporarily. Used butyl tape to seal and this has seemed to work well. I could not find any marine plywood, thus used poplar instead, epoxying and tabbing it into the hull. Use of poplar was a mistake, as the bulkhead (probably yesterday while sailing) split, so the chain plate bolts pulled part of the wood up against the deck liner ceiling. No more sailing this season; we have to pull our boats in about 3 or 4 weeks anyway as the lake is being lowered more than normal for maintenance of the dam and the level will end up too low to use the launch ramps.
So - what was actually used by Hunter - marine plywood? Or regular exterior grade ply? I doubt anyone (even this site) sells a shaped bulkhead as a part. Does anyone know if Hunter has templates for the shape - I can use the remnants of what I remove, but that is a pain as you have to do a lot of damage to the wood to grind it away from the hull. I intend to seal all the edges of the piece with epoxy in any case, so water can not soak in the end grain. Since I will have more time this go around, I will buy some biaxial glass tape for the tabbing, rather than the "standard" tape I had used. How many layers of glass cloth are needed to tab it properly?
Not looking forward to this - grinding out the broken bulkhead and remnants of epoxy (without making the hull thinner) and then doing the glassing is a messy job.

 

[Crazy Dave Condon]

Send a photo so I can see and respond. Maybe I can help

 

[isaksp00]

Here are photos. One shows the bulkhead I installed about 2 yrs ago, made of poplar, that has split where the chain plate bolts go through. I should have realized it would not last, as the grain runs vertically. The piece that was pulled upwards about 1 inch. The other shows how I tabbed it to the hull.
I just bought some 3/4 inch plywood, A grade, 5-ply - I did not buy marine ply (it was like $110 for the smallest sheet, 4 by 8) and did not buy exterior grade (as this bulkhead is inside and I plan to epoxy seal the edges). I intend to look for the area with fewest visible knots, cut out a new bulkhead, epoxy all the edges, and epoxy it to the hull, fillet the joint (as I did before), and then tab it with biaxial 4 inch glass cloth strips. I am thinking 2 layers of glass cloth?
Any improvements? Is the grade of plywood I got strong enough?

 

[Crazy Dave Condon]

I would have told you to bite the bullet and buy the marine grade ply. You are correct about the popular which I consider too soft and the multigrain as in the marine ply is the best as it distributes the load in many directions with the multi layers plus not affected by water as others. The biggest issue with regular ply you will have to stay on top preventing leaks not only with the chain plate but with the hull to deck joint which is more difficult to see. IF you plan to keep that ply then of course two layers of glass but sand it smooth and when laying, purchase a resin roller and use it to get a smooth surface so it will for sure bond to the wood and air bubbles are not in it. My only fear it will separate within itself.
The good thing is you know what you are doing and not afraid to get your hands dirty. You know if I were close, I would be there getting my hands dirty helping you. Please wear goggles and dust mask when sanding glass my friend

If there is a marina near by or a major contractor that requires marine grade ply nearby, see if they have any scrap big enough for your project that they might give to you or sell dirt cheap for scrap they are throwing away.

 

[isaksp00]

Thanks, CDC. I am ordering the biaxial glass cloth. Comes in 4 in wide rolls, 15 oz,, 10 ft long. The length of the wood bulkhead edge that is against the hull is 20 in, so that gives me six 20 in long strips. Would you do 2 or 3 layers of the fiberglass cloth to tab the bulkhead to the hull? I will encase the plywood with epoxy, especially the ends, and have used (and will redo) the chain plates and chain plate covers with butyl, which has done a good job since my earlier work on the bulkheads.

 

[isaksp00]

I cut out the new bulkhead from the 3/4 plywood, and sanded both faces. I still need to sand some of the edges more, to smooth out the cut line from the jigsaw. The photos show both faces and the three sides of edges. The wood looks pretty good, no real knots and no voids in the plys that I can see on each edge. Note that the grain of the faces runs horizontally (perpendicular to the pull from the chainplate). I think that the grains in each ply alternate direction, so there are 4 of the seven plys perpendicular to the pull, and three in line with it.
I am thinking of epoxying a rectangular piece of 3-ply luan (about 1/8 in thick) I have in my scrap pile, a bit larger than the part of the chain plate that bolts to the bulkhead. I'd put it on the side of the bulkhead that faces forward, that is, the side that is harder to see and also where the attachment nuts go. That would make the area of wood surrounding the three bolt holes more like 10 ply, and I'd think would make it less likely for the stress from the bolts shearing to rip the wood. Would you all think that will help?

 

[GGordonWoody]

Peter,

I'm told there is a custom metal shop in Hawley. I might be tempted to cut out both sides and re-do in 3/8" aluminum. Those stays must exert plenty of load on that joint. If you stay with the plywood, you might consider 1/2" thick and then lay with Kevlar on all sides. Can stop a bullet - you won't pull through that!

 

[isaksp00]

I have used that shop - right next to the Ritz theatre, good work, reasonable cost. They welded a cracked stainless tube on my swim ladder.
The stock bulkhead that came with it is 3/4, so I am already thicker than what you suggest. I thought of epoxying in an alum plate, but that seems overkill, since the bulkheads held at least until water destroyed the plys. I intend to block that by 1) epoxy sealing the edges of the plywood and 2) ensuring I seal the chain plate and cover properly with butyl. That is what I did after my 1st repair, and I have not seen any water intrusion.

 

[Brian M H23]

Peter,
I wouldn't bother adding more thickness to the chain plate - the plates themselves should have been engineered to spread the load out. These boats lasted 30 year with their original plywood, and save for rot (I had to replace the one under the cockpit entrance) worked fine. your fix will likely be the strongest thing on the boat!