myth busters: special home edition

The Myth:
That you can successfully steam bend timber at home, using little more than an old brake fluid drum, a weed burner and the draw bar that’s waiting to be welded into your boat's new trailer!


Up till now we’ve managed to bend all the timber onto the boat using only brute force and sheer ignorance. It’s mostly worked; we’ve only broken a few stringers. And a couple of pieces of ply on that over ambitious reverse curve in the bow.

But when we had a quick try with the top outer gunwale we realised there was no way we were going to get it on. It’s Fijian Kauri 35mm by 18mm, and it curves in both directions. A bit of research told us that others either cut it in two or slowly bent it round tightening it a bit every day. Neither of these appealed to us.

Steam bending has always seemed like the next frontier of boat building to me. Like it was a bit beyond us, in the realm of serious boat builders. We did a bit of reading, but I doubted that we’d cobble together something that would work. Even if we managed to get the steam going, whether we’d get that tight curve in the timber would be another thing.

Come Saturday morning, here’s what we had sitting on the drive.

It took us a while to get things working. Once the water in the drum was boiling, we found you need a decent incline on the chamber to get the steam coming through. The chamber had to be hot before we could do anything, so at the start we hurried it up with the gas torch and a heat gun ;o) .

The temperature measured at the far end of the chamber.

Seeing this is myth busters, at this stage I’d say:

There’s a 3% chance we’re going to create a massive explosion and just blow everything up.
There’s a 40% chance we just make the wood warm and wet.
A 25% chance we scorch and burn it.
A 10% chance it works out successfully.
A 20% chance of Zac seriously burning his hands.
And a 2% chance we actually get to go sailing before Christmas.

Yes! After about an hour we got a nice steady supply of steam.

We decided to put a practice piece first (although it was difficult to sacrifice a nice piece of Fijian kauri).

Dad stokes the fire.

After 35 minutes we pulled the practice piece out. It bent round very easily, although it was thinner. The problem was all this black stuff from the inside of the steel section.

We drew rags back and forth through the chamber to try and clean it. We also cable tied these bits of hose to the timber to try and keep it from sitting on the surface.

Here's the piece sitting ready to go in. You can also see our scarf cutting jig, each gunwale has one join in them.

Having the chamber at this temperature worked really well. We steamed them for about 45-50 minutes each. They say you have 5 seconds once the timber comes out to get the shape in it, and that was definitely the case for us. You could still move it a bit as it cooled, but it was only easy for the first few seconds.

That time limit makes things fairly intense! We still had to apply plenty of brute force. And it was quite frantic getting the clamps on as well as protective blocks of wood.

Here's a vid of the last piece going on. This was by far the calmest (least yelling) and most successful. You can see how we get the bend in it as soon as we pull it out, as we carry it down (this was rehearsed, several times).

In the end it worked remarably well. The plan now is to leave the clamps on for a couple of days while the timber realigns. We'll have to take them off while we glue the deck on, and then glue and screw them on the following day.

This myth is proven!