Thread: Bilge/engine compartment paint

clean off the paint that is there already, if you do not know what it is then get rid of it .

Clean the Bilge thoroughly , and then apply 2 coats of EVERDURE or similar product( epoxy wood preservative)

a LIGHT SAND BEFORE AND BETWEEN COATS IS ADVISED, THEN AT LEAST 2 COATS OF EPOXY RESIN AGAIN SANDING BETWEEN COATS, a layer of light weight Glass in the engine area would not hurt.

If you want to save a lot of work later , then use a good quality 2-Pack epoxy paint in the bilge , it will last for many years.

my 2 cents worh,

Jeff
vk4

I disagree with the epoxy recommendation. Epoxy has two effective roles in boat building; as an adhesive and as a encapsulation coating technique. Leaving aside the adhesive part of the equation, an assembled hull can't be fully encapsulated, so you're not helping things by dramatically reducing the entry and exit points for moisture. Just painting a surface with epoxy doesn't really help things, in fact can be detrimental, again by limiting moisture paths in and out of the wood, which leads to rot and sprung joints. In other words, since you can't fully encapsulate, moisture will get in and be trapped with limited paths out. The wood will still change dimensions with environmental changes, but with a progressively increasing amount of moisture encased in it.

You have a plank on frame build there, so it should be treated as such. Use a good quality primer (epoxy primers are fine though a little over kill) and the minimum is 2 coats, though 3 or 4 is better, then top coat with your choice of paint. The other side of the coin in this regard is to just varnish the whole thing and this is what I usually do. I'm not alone in this vain, many of the traditional wooden builders (Chris Craft, Thomson, Hacker, etc.) just used varnish. The logic is simple, so you can see what's going on with the planking or structural elements. For example, if you have a leaking fastener, maybe just weeping a tad, under paint you'll never know until the area is starting to rot and the paint starts to lift. If it's varnished, you see a dark spot around the fastener that is "growing" and you'll have a chance to get after the problem before you have to hack out rotten wood.

If it was me, I'd clean with a solvent wash of the wood, then use varnish or if you want color, plain 'ol alkyd based (oil) prime and paint. These aren't very costly, are fairly durable and most importantly flexible enough to tolerate the environmental changes that will occur as moisture content changes within the structure. Some folks like acrylics, but I'm not a fan of these in the bilge. Others like polyurethanes (single or two part), but these tend to be more costly and less flexible than acrylics or alkyds, though they are more durable (if they stay stuck), have higher gloss and gloss retention, these aren't usual considerations in a bilge.

Thankyou for the replies, Jeff and Par. I must say that I like the idea of varnish and being able to see what's going on. My hull isn't plywood planking, its sheet ply on plywood frames with timber longitudinals spaced every 6 inches between chine and keel, is this still regarded as plank on frame? I will get some pictures up tomorrow to explain. The bulk of the work is complete internally, but all the new (10 years old) bulkheads are without limber holes. There are 2 major bulkhead/frames forward of the transom (this comprises the area from the transom to midships), that are the height from the keel to the chines. The full length engine bearers are also bed into the bilge bottom, a foot on either side of the keel. This means that no liquid can travel forward to aft, or port to stbd. I have been thinking about the best way to remedy this.

The engine compartment is quite large, and has 2 large drain bungs through transom. I would like to epoxy resin the bilge of the engine compartment, lay a single sheet of woven cloth down, then resin and leave it clear for inspection purposes of the ply bottom. I would like to keep the engine compartment bilge isolated, so that no sludge etc can contaminate the rest of the hull. The engine compartment would have it's own bilge pump (or two).

I would then like to drill the next frame/bulkhead for limber holes, fit plastic pipe and resin to seal. That way, the rest of the bilge is common. I would then have another bilge pump (or two) in this bilge section. I would varnish all bilge/hull from chines down internally (exempting engine compartment)

This leaves a few more questions, and of course your opinions on my above thoughts?

The engine bearers are approximately 8-10 inches high, this means that any ingress of water to either outboard side of the engine bearers will be trapped. Would you recommend drilling limber holes through the bottoms of these bearers for drainage into the central bilge?

I am happy to varnish engine bearers forward of the engine compartment, but what should I use to protect the bearers in the engine compartment? Varnish also or epoxy?

Any particular type of Varnish? Will generic marine grade varnish suffice? And how many coats would you recommend?

One more question- I need to do some carpentry and replace horizontal beams that run from the gunwhales at midships, across to the main cabin uprights. I also need to make some new beams to support ply flooring etc. What kind of timber would I make these from? Ideally i'd like something I can purchase from the local hardware store (Bunnings). I assume I can't use pine, but what is something that I can work with easily (not hardwood) and generic?

Thanks again!

Chris

Would Tasmanian Oak be suitable? Also, for fastening of beams/supports etc, I intend to epoxy glue and screw, should I use stainless or brass self tapping wood screws?

Chris

I still stick with my first post regards the epoxy resin , in the bilge area,, AS PAR said " this will encapsulate the ply, " This is what it is intended to do, IN THIS AREA you should , as it will be subject to OIL, FUEL & hot water , at various times and need as much protection as you can give it.

Although PAR says you can use less durable paints , and yes you can, I always over build ,and tend to use the best products I can afford, ( sorry PAR I don't agree ).

Tassie Oak ,is classed as hardwood by the industry, , but I would look at HOOP PINE < , Celery top Pine, nothing at BUNNIES is suitable.

Jeff
vk4

Unless the plywood (or any wood) is fully encapsulated (end grain especially, all sides, all edges, all cutouts and notches) you wouldn't be best advised to coat with epoxy. Again, epoxy is only effective if the wood or plywood (which is planking, just really big pieces of it) is completely coated. Anything less than this, permits water to get into the wood or plywood, with limited avenues of escape, which starts rot. In other words, painting a surface with epoxy is well, painting, just with a really costly stuff, that will trap moisture, which is unlike real paint.

I run into this regularly. A boat recently came in, much like yours, a plywood over frame build from the 70's. It was well built with good materials, but the latest owner decided to coat the cockpit sole (floor) with epoxy to "seal" it. 5 years later, it had soft spots and was in my yard. He did a good job of coating the plywood, but the edges of the sole (end grain) and the underside, where just as they were previously, painted (which is okay) and moisture got into it, couldn't get out and rot formed around all the frame notches cut into the plywood, along the sides of the cockpit. The repair was a full encapsulated replacement piece of plywood (notches and all), which will not rot, because moisture can't get in.

So, you can use epoxy as paint if you want, but it doesn't act like paint and issues can crop up if moisture gets under the sheathing or coating. In a bilge, this is highly likely, so do so with warning.

If you want to improve the toughness of the bilge, use a relatively thick coating of paint (at least 3 coats of primer and top coat). I agree, you should use as good of quality products as you can, but LPU's (two part polyurethanes) tend to be a little less flexible then necessary on unencapsulated wood. This is why I recommend single part paints in this situation. These paints can move and stretch (and breath) as the wood changes dimensions with environmental shifts. The alkyds seem best suited in this regard, though not as tough as the single part polyurethanes, more flexible. This said, the latest acrylics also are quite good and much easier to apply and clean up. Use the highest gloss you can, as these are more moisture resistant then flat or semi gloss. If you want a flat or semi gloss finish, paint with super high gloss first, then top coat this with a flat or semi gloss.

Jeff if you reread my previous post, I never said "this will encapsulate" just by coating a single surface. Encapsulation is just as the word suggests, fully entombing or embalming the whole piece. Again, anything less then full encapsulation means, the wood isn't sealed and it will pick up moisture, through those uncoated areas. This is fine if it can get out again, but partly coating with a hard plastic shell (epoxy), limits the ability of moisture to get out, which leads (again) to rot.

On the sole I mentioned and just replaced, the old piece was removed whole (mostly) and used as a template. The new piece was cut and coated with 3 coats of epoxy, on every edges, sides, notch, etc. Screw holes were drilled slightly over size and coated, so that when the fastener was installed, the threads wouldn't rip out the epoxy coating inside the hole. I could have "bonded" the fasteners, but on a straight plank on frame build, this wasn't necessary as none of the other fasteners where bonded. The fasteners did receive a dot of polysulfide under the head as they were "run home" just to insure a seal.