Bending Gunwales

[Patricks Dad]

We're beginning to think about bending our gunwales now that our hull is glassed. The steamer we built for the stems isn't really a good fit for gunwales.

Has anyone done or considered the following:

Build a cheap aluminum rain gutter with both ends capped and sealed (say 6 feet long or so).

Prop it up on a stiff wire stand and put a camp stove (or 2) under it to boil water.

Fill the gutter with water and boil the ends of the gunwale material in the water rather than steam them.

Clamp to a form as generally recommended.

Is there a reason to steam rather than boil? (not hot enough?)

Would appreciate any thoughts (we're using cherry for our gunwales).

thanks!

[Its Me]

my $.02

I would be hesitant to direct fire thin aluminum for what may be an hour os so. That just seems like a lot of heat in a localized area.

I like the idea of using two heat sources, but I would use two cheap wal-mart steam kettles instead of applying direct fire to the aluminum gutter.

Editted to replace "down spout" with "gutter".

[Glen Smith]

That's what I was thinking also. The aluminium might melt before the wood has been boiled long enough. Also, supporting the trough with wire while manipulating 18 foot long lengths of wood in there with 12 feet hanging out the end could be dicey. I also believe steam will produce more heat than boiling water. Boiled wood must be left to dry for about one week before being glued. Steamed wood should dry overnight.

[davidb54321]

The biggest problem with boiling will be that the wood will take longer to dry out. Ok if you are not in a hurry to apply any finish.

[Patricks Dad]

Thanks for the thoughts. I'm no rush to get the gunwales to dry but hadn't thought about melting the gutter (now I'm curious - I might have to try boiling some water just to see what happens - with good thought toward supporting everything so it's not flimsy).

One other thought I had relating to boiling that might be a reason to NOT do it is clarity of the water. I woud think that if the water isn't pure, it might stain the wood in the areas that are boiled). Another reason to stick with Steam I guess.


Follow-up question: Do you steam and bend before or after shaping (e.g., cutting scuppers, beveling or tapering)?

[Glen Smith]

Maybe boiling would wash out some of the tannin and change the wood color.

Do all the shaping before bending. You will have less wood to bend and shaping it will be easier while it is a straight stick.

[KARKAUAI]

Have you considered using a heat gun instead? I found the whole steam thing pretty unsatisfactory, and the heat gun thing pretty easy. You just have to keep the gun moving to avoid scorching the wood. I might consider making a form to bend it on since you don't want to get too much heat on the hull. My gunwales were 1/2" x 2 1/2" and only required heating the last 4 ft. at the bow and stern. I clamped the gunwale to the hull up to the point where it didn't want to bend, then heated it right on the hull with a piece of 1/4" plywood between the hull and the gunwale to keep the heat off the hull. Worked great.

[Sid at Algonquin]

Good day;

I would not be concerned about melting the aluminum downspout as long as your water supply is constant. I have boiled many paper cups filled with water using a propane torch applied directly to the cup. As long as there is water above the flame line the cup will not burn.

Your Boy Scout son should know about boiling water in paper bags. That was always a fun camp competition when I was a Scout leader.

Sid

[Peter Kotowych]

What about wrapping the ends of the gunnels in wet towels for 24 hrs or so.
Then maybe use Kent's hot air gun?

Penetang Pete

[Jeff in Pembroke]

Hi Patrick's Dad,

I think your steambox might work better that you think. On my Redbird I steamed the last 3' - 4' of the ends of my outer gunnels - the bow end of the port (left) gunnel and the stern end of the starboard (right) gunnel initially. The other ends I didn't steam. When the wood was flexible I clamped the gunnels to the hull and bent the steamed ends. I also put a pencil mark on the gunnel and adjacent hull as a reference point. After the wood had dried for 2 days, I removed the gunnels, steamed the other ends, clamped the gunnels to the hull again and bent the other ends. The pencil marks ensured the proper location of the gunnels on the hull. After the wood had dried, I epoxied one gunnel on the hull. As the gunnels were a bit longer than the hull, I was able to trim and fit the second gunnel quite precisely to the first at the bow and stern ends before epoxying it on.
My inner gunnels were scuppered for most of their length and tapered at the ends. I was able to fit them easily without steaming. I epoxied these in as well - no screws.
They held up well through one season of fairly vigourous tripping - the second season starts soon (I hope!).

Hope this helps,

Jeff

[JimND]

Like Kent, I try to do things as simply as possible as long as I get the same results. I use a heat gun much more than I steam, simply because it is easier and faster, and it works, usually. Kent's warning about keeping the gun moving will avoid burning the wood, but I also wet my wood before heating, for a couple reasons. The wood is usually too dry to heat up good without burning and because the lignins need some moisture to become elastic. On gunwales, you could either lay them in the gutter and let them soak for 15-30 minutes, or just lay them out on some concrete and spray them with water a few times over a 30-60 minute period and allow them to soak up the water. This way the water will allow the wood to bend and the heat will evaporate much of the water in the process. Use one of the mentioned methods to avoid putting heat directly on your hull though as it can burn and/or weaken your epoxy. That is good advice even if steaming since steam is well over 200 degrees F. Whatever method you use, let the wood dry for at least a week or more before finishing it. Generally, I leave it for a couple weeks just to make sure I don't trap any excess moisture.