wood shrink outside

I spoke with a canoe maker and was told that his canoes, with wood gunwales, should not be stored outide over winter. Ideally, they should not be stored outside at all. Fair enough.

What about other wooden parts? My royalex canoe has one wooden part, a yolk. I had to refinish it after many years of outdoor storage just recently. This is to be expected. It’s occurred to me though, that if wood gunwales expand and contract causing problems (as the canoe maker mentioned), I wonder if similar problems would be caused by wood yolks/thwarts expanding and contracting. How 'bout a wood seat? Should it be left on or taken inside for the winter. If taken off, its ability to act as a thwart and maintain the shape of the canoe is lost.

not the same problem
Royalex canoes with wooden gunwales can develop “cold cracks” that originate at the holes in the hull that the screws securing the gunwales go through. When canoe builders mount gunwales these holes are drilled just large enough for the screws to go through.

Royalex shrinks in the cold and expands in the heat to a significant degree, much more than wood. As a result, the hull will shrink in the cold relative to the gunwales which are in a sense now too long for the boat. The gunwale screws can exert enough force at the sides of the holes penetrating the hull material to initiate a crack. The effect of differential expansion is greatest toward the ends of the gunwales so cold cracks most commonly occur near the stems, although they can occur elsewhere.

Having said that, many have stored wood-trimmed Royalex boats in unheated environments in cold climates without removing gunwale screws and without sustaining cold cracks.

I can’t see how differential expansion would have any similar effect on seat frames or thwarts. But canoes stored outdoors in humid climates where there is a lot of morning condensation could sustain accelerated deterioration of wooden thwart and seat frame ends. Any moisture inside an inverted hull tends to run down and collect in the narrow gap between the thwart ends and the hull and then seep into the gap between the inwale and the thwart end. This can cause rot since the end grain of ash is good at wicking in moisture.

Best thing to do is to take out your thwarts and seats and treat the ends where the grain is exposed. Even quality canoe makers do not always pay sufficient attention to these areas. I seal the ends with epoxy but a decent marine varnish or polyurethane will do. Many use oil but it is not as durable.

thanks for the reply

– Last Updated: Sep-12-15 10:27 AM EST –

what about wood gunwales on a non-royalex canoe? If I had a kevlar or fiberglass canoe, could it be stored outside (provided things like sun exposure, etc. were addressed) year-round in a humid summer/freezing winter environment? Would expansion/contraction be issues?

before we had a boat barn we had to store outside. Boats of all construction… over a dozen of them

And I store my wood canvas boats outside by the lake in the summer Inverted… no rot after 20 years but the thwart ends are sealed.

Varnish is your friend


– Last Updated: Sep-16-15 10:45 PM EST –

I spoke to another canoe manufacturer, and he confirmed that wood shrink is only an issue on royalex boats. In light of this, unfortunately I think that I'll probably go with aluminum anyway, since it would be more durable than wood outside. I say "unfortunately" since slotted wood gunwales look great. As for varnish, I'd imagine that I'd have to sand and re-coat every year, just like anyone with a wooden boat would have to do.

uh no
not every year. Five coats of varnish are what you apply…you only have to reapply in scuffed areas. PS. up here in Maine we have lots of all wood boats. Most are not mass produced and many live outside all year.

The term you wanted was not wood shrink but differential expansion and contraction. Wood and other materials have different rates of expansion and contraction and there is where you get the potential for stress where the two are bonded.

I used the term “shrink” because I have had wood items that have permanently changed shape as a result of humidity fluctuations. I was mistaken though. Items to which this has happened will expand and contract, but in worst cases, remain a little larger than their original size permanently.

How often do people in Maine re-varnish?

Have no idea as I am not everyone
but my wood canvas boats have a lot of coats of varnish. I do it every four or five years and only where needed. Not all areas get wear so some of the varnish is original from 1996.

It probably depends on the wood though. I have cherry and spruce gunwales.

varnish over epoxy
I built two wooden sea kayaks. Although I painted the hulls the decks were bright finished with varnish. Those boats were stored indoors. I had them for 5 or 6 years before I saw any need to touch up the varnish finish. Storing them outdoors might well have made a difference.

I have bright finished the rails on a number of my flat water canoes. These days, rather than using varnish alone, I will first apply a clear, low viscosity epoxy and then marine varnish over that. I believe the epoxy seals the wood better and makes for a more durable finish. I have no real proof of this, but I have read the same opinion voiced by folks who frequent the wooden boat forums. I don’t usually bright finish the rails of whitewater boats as they are too subject to getting scratched but I will sometimes bright finish thwarts or seat frames and hangers.

Not Main, but here…
It all depends on how it’s stored and how it’s used. My poling canoes get a lot of wear on the finish especially on the top of the thwarts and seats, partly because of the extra poles riding in the boat during use. I have to re-varnish that wood once a year or so. The thwart and seat frame ends and bottoms are protected from wear and from UV, so they don’t need to be done nearly as often.

My canoes that only get paddled can go several years between touch-ups. Even the one that gets stored outside (under cover and upside down). Don’t remember how many years I had my last Malecite (5? 6? More?), but I only had to varnish the rails a couple times (spar varnish), and the seats & thwarts - never. Of course - it didn’t get used as much or as hard.

Something else just occurred to me. I slide my canoe onto the roof rack of my car. Would doing this destroy wood gunwales?

Any abrasion…
…will wear through the varnish. Then it will be wearing on exposed wood. That exposed wood, if left untreated, will also be subject to water intrusion and uv damage. They won’t fall apart overnight, but their life will be shortened. I don’t slide my wood gunwales. Instead, I set them on from the side. If I’m using racks with no soft pads, I slit one side of short sections of pool noodle and slip them over the gunwales for protection.

I slide too

– Last Updated: Sep-18-15 10:16 AM EST –

and I use short lengths of clear PVC tubing slid over the gunwales where the gunwale meets the bar ( or loadstop or gunwale bracket)

Abrasion happens more during transport from wind buffeting.

You can also use pool noodle but that wont last as long.

I havent had any wear from loading though my bars are round.. You can cover with carpet if you are concerned..

Yeah, carpet works great
Sliding the boat up on the rack is harmless to wood gunwales if the bars are covered with carpet.

Someone else said that wear on the wood is worse during transport, and I’ve found that to be true (I found out when the carpet covering had shifted at one of the contact points). That’s another good reason to use some kind of padding, and/or a support system that helps minimize boat movement.

Overall, it only takes some minor precautions, in terms of your roof rack use, to keep your wood gunwales in good shape.