Mad Science 101

Disclaimer: I am divorced with no kids. I apparently have too much time on my hands. So…

With winter approaching I was thinking about how best to treat my ash gunwales REALLY well. I plan on taking them off of the hull to access the back side of the wood, and if I have to go that far…Why not jump in feet first into MAD SCIENCE!!!

Here is my idea: I will take a 17 ft piece of schedule 40 PVC pipe, cap one end, install a screw-type cleanout on the other and install a Schraeder valve (refrigeration type) in the plug. The wood goes into the pipe, followed by sufficient Watco to submerge the wood when the pipe is horizontal. Screw the plug in using Teflon tape for a good seal.

Now here is the Mad Science: Using a vacuum pump, I plan to lower the pressure in the pipe (0.5 atmospheres?) to draw air from the wood. Allow to stand over night. And then open the valve, causing the Watco to penetrate more deeply than it would with a simple brushing.

Am I crazy?


Yes, but it’s a good idea.

and people give me all this grief about the effort involved with so called “high maintenance” varnish!

I’m going mad myself lately trying to steam bend mahogany outwales to fit a 1929 Old Town OTCA, so I guess I know where you are coming from.



– Last Updated: Nov-12-07 10:10 PM EST –

And to think I just spent two days removing old (22 years old) discolored oil by sanding.
everything here has 4 coats and took about a week to get it right.

I don't think you will gain anything over a normal application except that the back sides of the wood will be better protected because you took the gunwales off.

It takes 3 or 4 coats with a good rub down after the oil is completely dry each time for me to get the results that I'm satisfied with. Ash is a pretty dense wood and no matter what only the surface will be penetrated. Walnut, Cherry, and softer hardwood (softer than Ash) will take more coats because the oil sinks in deeper and to pores are larger.

Hint. If your boat is stored inside and allowed to are dry after each trip you won't need to do nearly as much maintenance.

Hint #2 On cold damp days oil doesn't dry at all, especally if you watch it.

Also don't cry when you see what's under that gunwale. Usually one coat of oil (if that) and a rough looking cut job on the fabric from the mold.

think about
1. Watco reacts with some plastic materials, as in melts them. Do some tests first.

2. will -5 atmospheres collapse the pipe?

a couple of thoughts
If you are going to the trouble of taking the gunwales off, you could consider using some sort of wood sealer on the back side. There is some sort of penetrating epoxy sealer available, as well as plain epoxy. You could also brush a couple of coats of Minwax wood hardener or something similar on the backside if you didn’t feel like going the epoxy route.

Or you could just decide to have fun and do it your way. :slight_smile:

Mad Science 102
Interesting experiement, but I think you need to use positive pressure rather than creating a vacuum. Wood is commercially treated by using positive pressure to force preservative deep into the wood. Pressure compresses any air in the wood allowing the liquid to penetrate more deeply than short-term submersion. Of course, merely submerging the ash in Watco in your pipe container for about a week would probably work just as well, but what fun is that?


After you have them off…
replace them with aluminum or plastic

Never have to worry about sliding the canoe on and off the roof racks again.

Or better yet, just slit the pipe and use that to replace them.



Some thoughts
Norb: Yep. That first pic pretty much sums up the process.

Seumas: That was 0.5, not 5 atmospheres.

PaddleHB: Releasing the vacuum in effect causes the Watco on the surface of the wood to be pushed in with pressure higher than teh vacuum attained. In effect, positive pressure.

JackL: UUUUUUUUGGGGGGGGGLLLLLLLYYYYYY! Nothing like the feel and look of wood. Look at NT’s pics of his Curtis - Can you imagine the appearance of that boat with vinyl gunwales?


Yes, you are crazy
But I wish I was close enough to come over and help you. This is a very cool idea, and sure beats spending the winter watching TV or sitting in a bar. Call Mythbusters before you start and see if they will sponsor your project!

Consider three or four coats of Armada, which will last longer and save you a bunch of engineering work.

Mike & Charlie…
Yeah, I was planning on rotating the pipe rather than completely filling it. A mechanical means or rotating would be preferable to manually turning it. This idea is starting to get complicated. Maybe I could borrow Conk’s water wheel to do the turning duties?

Which Armada Charlie? They appear to have a bunch of products. I assume that you have had better luck with it than with Watco.


Couldn’t you accomplish the same thing by spinning your PVC contraption at high speed on the end of a long arm. At about 3 or 4 G’s the oil should be easily forced between the fibres of the wood.

I know that, but I figured I would get…
a rise out of someone.

There wasn’t a prettier little canoe on the water than my 13 foot Blakhawk with it’s wood gunnels.

Since we paddle so much, (training and racing) and the boats are constantly being slid on and off the racks, the vinyl or aluminum are my lazy mans choice.



Life Caulk

– Last Updated: Nov-13-07 8:40 PM EST –

Interesting thread, as I'm going to replace my rotted outwales soon. It seems like trying to force a drying oil into the structure of the ash, if at all successful, would only result in the oil oozing from the open pores of the springwood (the less dense part of the growth ring) and creating a mess. I've used Watco on white oak and experienced a similar unsatisfactory result. I am reminded of a time when I pulled the mahogany coaming off of a Pearson Ensign (sailboat) that had been severely neglected. The wood had gone completely gray with nary a trace of varnish left anywhere. I had to really pry them from the fiberglass, checking twice to see if I'd missed some screws somewhere. After finally getting them off, I found some reddish brown rubbery caulking along the joint between wood and FG and lo, the varnish back there looked brand new! I peeled off some of the rubbery stuff and ran down to the boatyard where the salty guys with gnarly tar-stained knuckles looked at each other and said "Yup, Life Calk" and not another word. I've been using it on boats ever since and I plan to run a bead (faired to a fillet) under my new rails where they meet the gelcoat. I usually don't endorse specific products, but when I saw how that stuff stood up to at least ten years of sun and saltwater, I was sold.

Sounds like a good idea
Sounds like a lot of work but it would work. I’ve got to think that those gunwale sections will be curved though, so you’ll probably need to bend your PVC pipe. Yeah, like others have said, to submerge the pieces, that’s gonna require a lot of oil!

Anyway, it reminds me that ages ago I heard that “telephone poles” and old-fashioned wooden bridge pilings are treated with creosote by the same process, except in that case, the container that was used could contain a railroad car-load of timbers!

I am assuming
that teh ash will “relax” after removal from teh hull. Probably not totally straight, but enough to allow insertion into a 4" pipe. But I am starting to have reservations about the amount of Watco needed…

Oh well. This is a January or February project, so I have some time to ruminate upon the details.


Vapor pressure
I don’t know the chemistry of Watco, but I would guess that there are some solvents in there that have pretty low vapor pressures.

I would be a little surprised if you could even get it down to 0.5 atm. You will probably vaporize the more volatile components and just leave the thick gooey oils to not penetrate the wood.

Maybe someone at Rustoleum will give you the mix, then you can look up the vapor pressure of all the solvents at room temperature. Whatever the highest vapor pressure is, that will be the lowest pressure you can achieve in the tube.

All that aside, sounds like fun!

Hmmmm. Vapor pressure…
You may be right. Watco contains mineral spirits, so I might loose them and be left with goo. And I know what Watco is like if you go away for a couple of hours and then try to rub it out.



Nothing like natural materials. Someday people will make that realization.