Sealing wood with oil

How feasible is it to consider sealing wood with tung oil or something similar, for fresh water use exclusively? Would such a system work if combined with substantial external chines or stringers, especially at the waterline, that would be easily replaceable? The boat in question will never go very fast, but is intended to last a long while. The reason I am asking this is to ensure that subsequent maintenance and repairs can be carried out without resorting to chemicals such as epoxy or fiberglass, or boatyards. I am especially interested in hearing from the professional builders here,whose opinions, from my reading of the threads, are to the point.
And a Merry Christmas and Happy Hanukah to all.

 

Big Guy
I have never tried oils around a fresh water environment, I did, however, go through "a phase" with maintaining otherwise varnished surfaces above the water line. It required constant vigilance. The oil would wash away quickly. A single sail would require another application. Now, I am talking about a sail from East Coast to Bermuda or to the Caribbean, but still you had to stay on top of it. That was above the water line. I can't see it working below. On the positive side...it was actually pleasant to apply. The most effective type I found was an oil extracted from pine tar from Norway...Geez it smelled great and made me feel ever so salty applying it.;?)

 

I'm sort of urged on by the thousands of years BE (Before Epoxy) that sailors (not that I consider myself a sailor yet) used to build wooden boats and seal the hulls to at least some level of waterproofness. If it's not a word, it should be! The oil should, in theory, penetrate the cells of the wood, and then repel the water, shouldn't it? On one thread I found, and lost, on another board, someone was talking about applying RV roof sealant below the waterline, the thick, black, mastic stuff. The thread indicated the builder had at least two years of maintenance-free sailing with that. I'm not a fan of simply going with different chamicals, so I wanted to ask about the oil...

 

In my travels I've seen all kinds of coatings. For example, in Northern Brazil fishermen burn tires over their upturned boats. The black gunk adheres pretty good and coats the bottoms.

 

Have to coat all surfaces exposed to water. Inside and out. I don't like the smell of Channel # 7 - Burnt Rubber. At least they stop the fastest on the sand.

 

Yeah, Richard, traction is everything. But the concept is interesting. Gonzo, do you think that the carbonized rubber would protect the wood? If they're smaller boats, I imagine they'd be hauled every day, which might affect the protection offered. What about if they were left in the water?
How about pine tar? It's not good for living things, but it might work like the rubber, and seal the wood with a semi-flexible, water repelling barrier...

 

I've used traditional oil finishes many times and on some craft it's the only thing appropriate. Typical oil coatings require reapplication several times a year in weather deck uses to maintain the finish. I've never seen it used below the waterline, but if used they would, I'd think, need renewal much more often. If coating the bottom of you boat every month with an oil mixture is what you're interested in, then go for it. Frankly the effort, time and costs would quickly pay for a harder and more durable coating, like paint.

Glass or other reinforcement set in epoxy provides an excellent abrasion resistant coating. This is the real reason for it's use, because the ability to keep water out is more a structure engineering job, then the application of a thin, water tight coating. Many thousands of boats has remained water tight without the use of epoxy and reinforcements, because of good design. Cloth set in epoxy can stave off many years of abuse, before planking replacement is needed.

The real trick to long life is seamanship. Fixing dings, scratches, checks and the like shortly after they occur is the way to keep a wooden structure alive. The coatings, no mater what is used, will become breached. This is what happens to every boat, if used, even with very reasonable and careful skippers. If the coatings (paint, epoxy, oil, or whatever) get a nick, water gets in, promoting rot to form or little wood eating beasties to move in and make a buffet out of you keel, planking or wherever. Keeping after these coating breaches is the fine art of good seamanship. No different then wiping the morning dew off the brightwork, before it has a chance to magnify the suns rays and kill some varnish under that spot or washing sails or dock lines.

 

Par...
Thanks. I wasn't aware that an oil coating would require so much work. When you say paint below the waterline, are you talking about the epoxy/urethane brews? Could you go to a hard, exterior enamel or something similar? I'm competent to do part-ship work, but major stuff is beyond my (current) scope. I'm a fast learner, though...

 

Nordic work and pleasure boats are routinely oiled. However, their standard of beauty is very different from the USA. Their boats have black stains all over.

 

By coincidence, most common water rot of wood, is the color black. I know this for a fact as our Hacker reproduction speed boat has a crack in the epoxy finish. Black color is rapidly covering one side of the hull. Black hides wood rot in the ST. Lawrence River.

 

So it sounds as if oiling isn't practical. Too bad. I like the idea - all natural, no allergies, no rashes, no breathing masks... is there any positive to oiling that anybody is aware of?

 

Oils produce alergies too. The ones that are fungicidal are toxic.

 

I use an old formula for an oil finish, but is purely intended as a brightwork coating. There are some tried and true heavy body coatings that could be used on the bottom, though most contain petroleum products and would not be recommended by the authorities.

Roofing tar, the petroleum based stuff, would make a very good bottom coating, but you'd likely run afoul of the environmental police, if they were to get wind of it, which would be rather easy for some time after application. It stays gooie for a long time and would make a real mess of a trailer and anything else it touched. I wouldn't recommend it, but it would work okay.

Oil based paints aren't real hard, but are better then acrylic. Epoxy paint is next in hardness, but more difficult to apply a nice finish, for the average backyard builder. The same goes for the single and two part poly's and they're even harder to get a good finish with as a shade tree builder, though it is the hardest of the bunch.

If you follow the instructions on the can, especially in regard to the additives, a poly job could be very nice. On the other hand, if you screw up the mixture or are working in less then ideal conditions, then you could end up with a finish only a mother could love. Ideal conditions are temperature/humidity/ dust/particulate controlled booth with the needed lung/skin saving equipment.

 

I didn't know that oil finishes could be hyperallergenic. I was mostly thinking of tung oil. From what I've read, historically, the Chinese used it to waterproof (?) their boats. I was considering an alternative. I am profoundly interested in conserving the environment, and I wouldn't use something that did damage. With regard to the paints, would a matte finish oil based paint, say in an off-white, work on the topsides? It would hide any unfairness, wouldn't it?

 

Big Guy Have you thought about, boiled Linseed oil, thinned well with Real Turpentine, you have to use real turpintine not Turpomin, which is some times sold as being the same, smells like pine trees, Just be sure to keep all rags etc. in a air tight container, or soak in a bucket of water when done, as this mix has been known to spontaeously combust, when drying. I have used this for a lot of things, and am quite happy with results.