Thoughts on best way to repair this wood rot?

[vwkevin]

I found some pretty nasty, rotted wood during a fuel tank swap last weekend. It is located in the back compartment on a 1968 Islander 34. Anybody know the best way to repair this before the new tank goes in? I assume it should be cut out and replaced with fresh wood, but do I need to have any structural concerns or anything while the rotted wood is out? What type of wood should I be getting at Home Depot for this repair? Would I just fiberglass the seam between old and replaced wood or do I need to epoxy coat it and use thickened epoxy or something like that? Also, I grabbed some brush on Rustoleum gloss protective enamel while at the store. I assume that's a bad thing to coat the pictured compartment with after the repair, right? Sorry for all the questions - my knowledge of wood repair is unfortunately non-existent.

Tools I have - jigsaw, oscillating tool, drill, other basics. I also bought some bondo wood rot treatment, but now I'm thinking I should just fix it properly.

Thanks everyone!

[coopec43]

I am not all familiar with the Islander 34 so that maybe explains why the photo does not make any sense to me. Where's the rotted wood?

I would only ever use epoxy over the timber/glass (after giving the fiberglass a coarse sanding) I'd "round" the corners of the timber before glassing if you can.

[psk125]

What Coopec said. Possibly having a seam in the repair makes it sound like you may be looking to replace the darkened part of the big plywood sheet shown in your picture. What does it do? What are the bolted-on straps for? A seam there may make no difference, or may need to be watertight - we don't know. Home Depot is probably not the place to procure boat wood. Marine plywood is not in the inventory at any of them around here.

[Chotu]

We need a lot more information than that. What is that bulkhead? Is it something that separates a stern locker? The engine room? What are those stainless tabs screwed to it? Do they go to the rigging?

Do you not go to Home Depot for any wood for this project. You’ll be doing it again in a couple years if you do.

[1affiah]

https://www.homedepot.com/p/AB-Marin...6540/202084532

Well, actually they do, at least here in Spring Hill, FL. but for that application I would look at exterior plywood. Pay special attention to sealing the end grain with epoxy before installing.

[jimbunyard]

To do it right you're going to need at least a 4 1/2" angle grinder and some coarse (16-40 grit) discs. As well as good eye, lung and skin protection. Good polyester resin and glass is fine for this application, but epoxy adheres better to both wood and fiberglass.

If you're going to use wood, for longevity the best for this application is properly dried, treated 3/4" plywood. If you're in a hurry this option is likely not available, since 'proper' drying of most Home Depot-style treated 3/4 plywood takes at least a month.

If you can in anyway afford it, the best material for this application would be 3/4" coosaboard. If you're in a boating area you might be able to find some one who has a piece large enough for your project; looks to me like a 3' x 2' piece might do the trick. If you're in my area, I'm pretty sure I have a piece that would suffice...

If you have to use wood, pull out all the rotten wood, saving anything you can to help make a pattern to cut the new panel from. If you can't save enough for that, make a pattern with cardboard; it's generally easier to use two or more pieces, cutting them to fit specific sections and then taping them all together for the final complete pattern.

When you've gotten all (or as much as you can) of the rotted wood out, don your safety gear and get in there and grind about a 4-6" wide swath where the new bulkhead will be situated, removing any old tabbing and/or gelcoat or filler that held the old bulkhead in place. When the grinding is done, vacuum up the mess and make your pattern.

When you've made the pattern and cut the piece to fit well enough (doesn't have to be perfect, a little gap is actually better), I like to glass the panel before installing it; you can do a better job with it out in the open than in the vertical enclosed spaces of the inside of the boat.

Once the panel is glassed, mount it in place with some resin thickened to peanut butter consistency, smoothing the juncture (filet) to allow even tabbing; two layers of the same cloth you coated the bulkhead with, 4 and 6 inches wide.

After everything's done, paint it with whatever paint you deem appropriate. If you're not using something that will chemically bond with fresh resin, it's best to wait at least a week for the resin to fully cure.

It ain't rocket science, but it does help to approach it in a methodical, patient way. You can probably find some good videos on youtube, but beware of those advising shortcuts deviating from manufacturers instructions, at least until you've gained some experience...

[Franziska]

Get rid of all the rotten stuff at first.
Then you have two options, of which one is unconventional.

First option cut out the wood area, feather all edges from the outside and glue a new wooden panel with matching feathered edges in with epoxy.
Flatten all transitions between old and new panel & glass over with epoxy from both sides.

Option two, get rid of rotten parts, close any hole temporarily with MDF or plywood in a way that it's flush with the outside.Before closing tape over the surface facing the inside of the hole and, to keep it DIY and simple, brush some washing up liquid as release agent on this surface.
Than lay up a solid laminate with biaxial glass on the inside.
Make sure to use epoxy for this, as it's got by far better bonding abilities than polyester.
Once you layup has cured, remove temporary mold. Wash from outside, sand add another layer, or two of glass from the outside.
Let it cure and finish the surface.

If you use method one make sure any surfaces facing the new tank are properly sealed against new rot. My guess is that condensation or a tank leak caused your rot.

[Stu Jackson]

I know it's expensive, but if for only a part of that bulkhead (whatever it is or does) could be starboard then covered with the suggested fg. I don't know if epoxy adheres to starboard. Just thinking outside the box of possible alternatives to wood. Good luck.

[chowdan]

Definitely give us more information about what this area is.

From the looks, it appears some wood was tabbed in on the left side of the photo. Is this the area your looking to rebuild?

If you go with homedepot wood use their marine grade stuff and if they dont have that, use exterior grade plywood. The glue used in interior ply is not waterproof, while exterior is.

Regardless, your new piece you'll want to cover it with epoxy, and as others have said, make sure the edges are throughly saturated.

Use cardboard, or if you have access to doorskin, use 5hat and hot glue to get your template.

As for fitting, if tabbing into the hull, leave a small gap and use biaxial or if there is no sharp turns use woven roving. If theres a sharp turn between two surfaces use thickened epoxy and the back of a plastic spoon to round it out and create a smooth transition. I'd personally use biaxial as I find it's easier to work with. Tab it in 4-6inches on the hull side.

Just make sure your surfaces are smooth, clean and free of contaminants.

Really not a hard process, just time consuming

[Steve Bean]

Do remove all rotted wood, but before replacing it, do some treatment to kill remaining spores of the fungus that causes rot. They are too small to see and will lurk quietly until conditions of moisture and temperature allow them to resume their destructive work. To learn how to kill the fungus, read "Chemotherapy for rot" on the internet by Dave Carnell. If you want to use plywood, find out exactly what the differences are between exterior and "marine" plywood. The glue is the same. The price is very, very different. If you're not building a hull, do you need marine plywood?

[GordMay]

Originally Posted by Stu Jackson

I know it's expensive, but if for only a part of that bulkhead (whatever it is or does) could be starboard then covered with the suggested fg. I don't know if epoxy adheres to starboard. Just thinking outside the box of possible alternatives to wood. Good luck.

NOTHING wants to stick to StarBoard, nor any HDPE.
Some form of surface preparation (typically, sanding & cleaning then flaming) is needed to achieve significant bond strength on low energy surfaces, such as polyethylene, with most adhesives.
From KING: “... It is preferable to mechanically fasten or weld King StarBoard®, but when an adhesive is necessary you can use a product called Lord 7542-AB, or 3M’s Scotch-Weld DP-8005, or Chem-Set™ 6105 Polyolefin Bonder.
We do not represent these products, make any claims about their abilities or accept liability for them...”
➥ https://www.kingplastic.com/using-ad...g-starboard-2/