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 C25 Bulkhead rot

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T O P I C    R E V I E W
n5ama Posted - 09/17/2021 : 21:35:07
My 1987 C25 has a bulkhead with about 4-5” of either rot or black mold/mildew at the bottom that was hidden by the cushion. I’m guessing that the water came from a leak at the chain plate. I haven’t probed for rot but suspect that it is at least damaged if not rotten.

I used butyl tape to bed the shroud plates about a year ago but it seems the water came in through the chain plate cover at the deck level. The first order of business is re-bedding the chain plate entrance.

I’m competent working wood and fiberglas but have never worked with a bulkhead. I guess my first question is, do I need to go to a professional to do this work? My second question is, do I have to replace the entire bulkhead or just cut out the bad section on the bottom and splice/Fiberglas in a patch on what is bad on the bottom? The chain plate is located in the upper area of the bulheads

Thanks in advance for any help.———————————————————————————————————————————————————————-211

19   L A T E S T    R E P L I E S    (Newest First)
Steve Milby Posted - 03/25/2023 : 13:29:42
Happily, I never had to replace my bulkheads, but here are two more links to previous threads on the subject that you'll probably find helpful.,bulkhead
dkharvie Posted - 03/25/2023 : 13:06:17
Thanks Steve, looks straightforward. I wonder if the port side, which is much bigger, will be more difficult. Also, in the video, they're just using bare plywood... I plan on at least staining it.

Originally posted by Steve Milby

Derek, here's a link to a video posted previously in this thread, showing how to replace the starboard side bulkhead. It doesn't look too daunting. I hope it helps.

Steve Milby Posted - 03/24/2023 : 16:21:55
Derek, here's a link to a video posted previously in this thread, showing how to replace the starboard side bulkhead. It doesn't look too daunting. I hope it helps.
dkharvie Posted - 03/24/2023 : 16:02:57
I think my port bulkhead is in much worse shape. There's quite a bit of rot at the bottom as well as all around the chainplate. I don't know much about working with epoxy. Would it be overly difficult to just remove and replace the entire bulkhead with a new piece of marine plywood with teak veneer?

Allmanjoy Posted - 03/17/2022 : 18:41:20
Leon, Thank you. Definitely going to do some practice pieces. Appreciate you taking the time to explain.
Leon Sisson Posted - 03/16/2022 : 19:49:54
Jay C,

Re:  "Did you save the original bulkhead to keep your vessel original?  It seems like a replacement would have been a lot easier,..."

Well, I didn't reuse old bulkhead to keep the boat original in the sense of collectible-car-with-factory-matched-serial-numbers.  More a matter of I like the way that original teak veneer plywood looks after varnishing, and I don't know where to find it new for a price I'd be willing to pay.  Also, what looks difficult to one person may not be for another.
Re:  " have the skill set and understanding of fiberglass/resin work... I fear with my lack of experience..."
Reading books and watching YouTube videos is a good start.  The Gougeon Brothers (WEST System) have produced some excellent books, and videos, on building and repairing boats using their epoxy.  An obviously indispensable (downright unavoidable) step is rolling up one's sleeves and making mistakes while discovering what works and what doesn't.  I might suggest starting with practice pieces which can be sacrificed to lessons learned.  No welder started out making flawless welds; no body man's first crash repair turned out invisible; no woodworker's first project... etc.
Re:  "I fear with my lack of experience removing the bolts and adding fiberglass/resin fill may not be done adequately to handle the loads on those bolts."
For the chain plate bolts, I used the 'drill 2x oversize, epoxy fill, redrill' method.  It's dead simple, and stronger then even new plywood.

For the numerous #10 screws, years of the hull working (flexing & squirming), and water damage had already done some of the hole oversizing — in some spots rot did a lot of oversizing.  I cleaned out the holes using a Dremel with a burr bit to remove what was left of weakened fibers while trying to keep track of where the original hole center was.  In a few spots I applied an 'L' of masking tape and drew right angle lines centered on the old fastener.
For damaged wood expected to handle high loads, I first wet out the enlarged holes with slightly diluted epoxy.  On those and holes in good wood, I then wet the holes with undiluted epoxy.  For the filler, I mix in as much milled fiberglass (precision manufactured lint) as I can get to flow through a syringe with tip cut/drilled wide.  I do all two or three of these applications without waiting for the epoxy to cure, which produces a strong primary chemical bond between batches.  The wood will continue to absorb resin as it's being applied, so I usually leave a slight convex crown on the final fill to reduce the chance of ending up under filled.  Hardware bolt patterns are preserved by maintaining at least two original location and diameter holes to locate the part, which is used as a drilling jig for the filled holes.
Remove excess epoxy before it fully cures.  With experience one learns which removal tools work best at what stage of partial cure.  Acetone soaked paper towels, razor sharp knife or chisel, Surform style rasp, (re)drill holes, various Dremel bits, hand and power sanding, disk grinder, etc.
When in doubt, mix smaller batches using a slower hardener, but never deviate from the epoxy manufacturer's specified mixing ratios.  Thorough mixing is crucial.  I use a cordless drill and a spare Allen key for small batches (headless nail bent 90° works too), a propeller-style paint mixer for larger batches.  Be cautious about pouring thick cross sections brewed with fast hardeners in hot weather.  Metal (cool, not sun baked) acts as a heat sink, solid fiberglass less so, wood and foam are thermal insulators.  If a mixed batch of epoxy starts to overheat, or thicken and gel, stop applying and dump it!  The chemical reactions during early stages of cure are quite exothermic and accelerated by heat.  By the time the container feels uncomfortably warm, it's in thermal runaway.  Overheated mixed resin can foam (boil), smoke, even catch fire.  Of the various recommended personal protection equipment (PPE), non-permeable gloves are the most essential.  Don't let mixed resin contact skin.  If it does, wash it off ASAP!
Now dive in and repair something!
Allmanjoy Posted - 03/15/2022 : 02:41:55
That's really impressive. Did you save the original bulkhead to keep your vessel original? It seems like a replacement would have been a lot easier, but I can understand you making the repair. Clearly you have the skill set and understanding of fiberglass/resin work. I've watched boat works youtube channel and have a fiberglass repair book from practical sailor, but I haven't ventured down the path of doing repairs yet. I fear with my lack of experience removing the bolts and adding fiberglass/resin fill may not be done adequately to handle the loads on those bolts. So I am tempted to just replace. I really appreciate the pictures and the use of a jack to remove the bulkhead. I think I may be inspired to repair the original.
Leon Sisson Posted - 03/13/2022 : 13:08:40
On Repairing Catalina Plywood Bulkheads

Like some of yours, my Catalina plywood bulkheads had water damage, particularly at the bottom edge.  Rather than section or replace the bulkheads, I repaired them using epoxy.
Since I also planned to varnish the teak veneer, I started by removing whatever the original finish was (water soluble wax based stain maybe?).  After several disappointing attempts with acetone and mineral spirits, water — with or without a bit of simple Green cleaner — and lots of paper towels turned out to be the best method of washing out the old stain.
The most prevalent damage to my bulkheads was delamination of the plys near the water damaged edges, small pockets of rot around a few screw holes, and some delaminating veneer below the chainplates.

First, I gathered up every clamp I could find, a roll of wax paper, a couple 10cc or 20cc syringes (WEST brand), acetone, a steak knife I didn't care about ruining, and of course my ever ready WEST epoxy mixing supplies.
I started with small batches of epoxy diluted with about 25% to 50% acetone to encourage penetration and saturation.  I used the knife to gently spread the plywood layers, which helped determine the extent of the delamination, and aided getting the epoxy filled syringe tip in between all layers.  Once the thinned epoxy was running out all over and making a mess, I switched to unthinned epoxy.  Keeping in mind there was only one chance to get this right, I applied more than enough epoxy to fill the gaps.
I clamped the oozing mess together using wax paper, flat scraps of wood, putty spreaders, and whatever else was handy to distribute clamping force and keep the plywood surface flat while the epoxy cured.

(No such thing as too many clamps.)
Where delamination blisters didn't extend to the plywood edges, I used a razor knife to make narrow slits in the veneer parallel to the grain, through which I then injected thinned epoxy.  Where clamps couldn't reach directly, I used scraps of thick cabinet making plywood laminated with Formica or equivalent, backed with lumber, held with my largest clamps.

To fill pockets of rot at screw holes, after first saturating the holes with thinned, then unthinned epoxy, I used epoxy thickened with glass fibers, with tape on one surface to keep it from running while it cured.  I then then redrilled to clearance diameter for the screws.  I was able to reused all the original holes in the boat.  However, I wouldn't hesitate to drill new holes nearby if the old ones weren't usable.
Once all that cured, there was lots of sanding, varnishing, sanding, varnishing,...
A hydraulic jack was helpful in lifting the deck a fraction of an inch to get the bulkheads out and back in.

Although not visible in the photo above, I routed wiring inside the compression post for mast lights, VHF coax, and solar panels.
I've used this procedure on two Catalinas, about eight bulkheads and similar panels.  A couple years later, I'm still satisfied with the results.
Allmanjoy Posted - 03/12/2022 : 15:51:46
I'm working on the same issue this season. I'm thinking about doing a core of the West Marine plastic lumber ( ) for the core and then a two pieces of teak veneer on the front/back for aesthetics. The starboard side is what's damaged. Seems a previous owner tightened down on the lower bolts and punched through on two of them. I thought about cutting the lower part out and doing some form of support on either side with resin to hold it all together, but I really don't know the structural strength of that fix. Thoughts?
Voyager Posted - 09/26/2021 : 20:05:36
It’s amazing what you can do with faux color and gel stains these days. They could have closely matched teak grain using marine plywood with some of the newer finishes. Perhaps they’ll eventually find a teak veneer to cover the bulkhead.
n5ama Posted - 09/26/2021 : 05:24:44
Wow, i watched the video! Those guys appeared to just replace the bulkhead with a raw piece of marine plywood, no finish, veneer or anything to help cosmetics. They went to all that trouble and they should have dry fitted it, pulled it out and at least sanded and put some paint on the thing.

Well, it looks like they fixed the problem. I also looks like the gal had a lot more savvy than the guy on what to do. Thanks for the link Bruce!
Voyager Posted - 09/21/2021 : 17:46:25
Agreed Tom, Emily's not bad. In that case, the should have used a thinner piece of plywood and sandwiched sheets of teak ply over that, or some veneer. Seemed like they were more concerned about getting the chainplate reattached and securing the mast and shroud than worrying about the cosmetics.Not sure if they’re a one-off or if they plan on rehabilitating the boat over time.
n5ama Posted - 09/21/2021 : 15:34:49
Wow, i watched the video! Those guys appeared to just replace the bulkhead with a raw piece of marine plywood, no finish, veneer or anything to help cosmetics. They went to all that trouble and they should have dry fitted it, pulled it out and at least sanded and put some paint on the thing.

Well, it looks like they fixed the problem. I also looks like the gal had a lot more savvy than the guy on what to do. Thanks for the link Bruce!
Voyager Posted - 09/21/2021 : 14:38:33
Sounds like you’ve got plenty of experience with your method so that’s the best way to go. Lots of folks use butyl tape successfully for sealing their deck fittings. I was kind of surprised that the YouTubers had a problem, but water intrusion is very tough to stop.
n5ama Posted - 09/21/2021 : 06:09:36
Good morning Captain Bruce,

Thanks for the YouTube link. I will definitely watch it but I’m not inclined to replace the entire bulkhead because of a cosmetic 6”x3” hole far away from the chain plate and easily accessed. Ive never worked with a bulkhead using the poly resin, but I have used it several times on severely damaged wood with great results. Sealing it up so the uncured resin doesn’t leak out is the key. Any little holes below your pour point and the stuff leaks like water for the first 1.5 minutes after mixing. If you time it right and wait about one minute before pouring it in, you have a good chance it will flow to the low points before jelling and then turning solid. I normally do several small pours before dumping in a large volume.

My flat barrier will have a little texture on it to better attach a piece of teak veneer. I plan to do the same area on the other bulkhead just for the match. I will have plenty because the smallest piece of veneer I’m able to get is huge compared to what I actually need for the repair. I do have a hardwood supplier that might have a smaller piece of solid teak that I can either resaw or mill thin enough to not look bad. I would like it to be no thicker than 3/16”. I’ll probably have to joint several pieces to make up the width. I just don’t know what they have on hand and I’ve never milled teak.

The first thing I did after discovering the rotted spot was to place a bunch of butyl tape under both chain plate covers. We don’t get that cold down here so I don’t know what happened to that seal job. I sealed everything that went through the hull when I bought the boat about a year ago but I guess I didn’t do a good enough job sealing the port side.

Voyager Posted - 09/20/2021 : 16:03:44
Funny you should ask, a YouTube popped up in my channel about this very situation. See
The owners, Emily and Matt decided that the bulkhead was so far gone they’d just go ahead and replace it using marine-grade plywood. A lot of tugging, unscrewing and cursing later and they got the old one out.
They used the old one as a template for the replacement. Of course, none of the holes aligned perfectly. They redrilled the holes using a round rasp.
Finally, they used butyl tape to seal the chainplate. It worked well in the warmer weather but leaked during the winter. They decided to use 4200 sealer afterwards.
I liked the video as they seemed to be learning about how awesome C25s are, although they’re a little rough around the edges at the moment.
Voyager Posted - 09/19/2021 : 21:17:21
Tom, if the location is normally out of sight behind the cushion, then filling the wood with plastic is a great solution. It’ll never rot again.
But if you’re ever going to see the area, maybe you should invest in a small piece of 1/4” teak plywood that you can lay over top of the poly, then fit it into the cutout in the bulkhead?
n5ama Posted - 09/18/2021 : 21:46:39
Hi Leon, thanks for the reply! The rot area is limited to a 3”x6” spot on the bulkhead near seat cushion and about 8” below the lowest chain plate mounting bolt. The rot doesn’t extend through the bulkhead into the head side of the bulkhead but it’s rotten there. I plan to remove all the soft wood I can from that area, dry it out and put a flat damn against the bulkhead and pour enough low viscosity polyurethane resin in there to saturate the remaining soft parts and fill the space resulting in a much stronger. This stuff jells in about 1.5 minutes and turns out a very hard/dense plastic in 15 minutes.

Leon Sisson Posted - 09/18/2021 : 11:57:28

I think bulkhead water damage caused by leaking chainplates is not unusual on Catalina 25s.  I repaired mine by saturating the delaminating plywood with epoxy.  At fastener holes in the plywood, I drilled oversize, filled with thickened epoxy, then redrilled to original size and location.  I can provide additional details and pics later if needed.

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