apple pie construction showing stitch and glue method of boatbuilding

making a Steam Box to Bend Wood

During my SCAMP Sailboat build, I found that the gunwales were too stiff to bend so I made a temporary wood bending steamer. I did not buy anything special but used stuff I had around the shop.

Being a pack-rat just sometimes, pays off!

Making the wood bending steamer kettle

This is where the water will be boiled to make steam.

2 coffee cans

I had a few empty coffee cans around. I got my tin snips out and cut the rim off both of them. It was surprisingly hard to do.


slots in top of one canhole for pipe

I cut a series of slots in the edge of the can that will be the top can of the wood bending steamer kettle.

I had found a 3 foot pipe that would work. It was the handle of a long dead broom. Quite light metal but strong enough for this project. I cut the top hanging hoop and the bottom threaded bit with a hacksaw.

I also found a length of metal conduit that would have worked just as well but it was heavier.

I used a nail and made a series of holes and cut between the holes with wire cutters to make my opening. It's at the bottom edge of the can. I tried cutting it with snips and scissors but the hole is too small for that. I pushed the pipe in and it fit reasonably well.

Finally I made a larger hole in the very bottom of the can. This is where I will fill with water.

2 coffee cans together

I tapped the 2 cans together. The one with the slots fit inside the other one. The fit is actually quite snug. It helps to get them together if a few of the slots cut in the edge are slightly longer than the rest.

The filling hole is just visible on the top of the can.

I've pushed the pipe several inches in the can so it does not accidently fall out.


Making the steam box

The next step was making the actual steam box where the wood sits.

dryer pipe

I had some old expandable aluminium dryer pipes in the back of the shed and the 2 pieces were long enough once expanded to fit my wood. I could have made the steam box from boards I think, or maybe even from heavy duty aluminium foil.

There was actually a short bit of pipe in one of the tube and that made it easier to connect them. I cut a couple of slits in one pipe and just slid it inside the pipe.

I flattened the back end of one of the pipe but left a small opening to drain water and extra steam.


plug

I went in the wood junk pile and found a cut off end of 2x6. This was large enough to cut the front plug of the pipe. I used the band saw at an angle to get an angled edge.

Cutting a hole with a spade bit was simple. It is just a bit larger than the diameter of the pipe so it can slip in easily.


Putting the wood bending steamer together.

I had all my pieces now. I needed to test the kettle.

The steam box needed to be insulated so I stole a few of the rattier towels from the house and used that to wrap the steam box. There was also some fiberglass loose insulation and I wrapped the pipe with it and tied aluminium foil to hold that together.

To get a better seal, I went around with a foil tape left over from a furnace replacement project many years ago, and taped all the connections. I taped the 2 cans together, the pipe to can seam and the 2 dryer vent pipes. I also kept enough tape out to plug the filling hole and to seal the pipe to wooden plug seam.

steam testfilling the can

The fire in the stove was burning well so I put some water in the can and put it on the stove. I needed to check that I could get some steam going. I had not put the pipe in the steam box yet because I wanted to check that there would be enough steam.

The water came to a boil quickly enough but did not produce enough steam to do the job. I needed more heat.

Wood bending steamer up and running

hot platelots of steam

Back to the house to borrow the hot plate. I had bought this small induction hot plate. Canadian Tire had them on sale at half price and I wanted to try induction cooking. This only works on pots that are magnetic but the coffee can was, so I knew it would heat.

Because the hotplate does not actually get hot I was able to wrap the top of the can with a towel to help insulate it.

It took a few minutes to start generating steam but once it was going there was lots. I put the end of the pipe in the wooden plug and taped the seams as well as I could. In just a few minutes the dryer pipe was very hot and I started seeing steam come out of the end.

whole setup

This is the whole set up. on the right the boiler sitting on the hotplate and that sitting on a workhorse. The pipe is wrapped in aluminium foil. The red and green sections are the steam box wrapped in towels and a couple of scarves to insulate them. The left is the end of the pipe. I placed the set up on a long piece of plywood so that I could have a slope to drain any water that condensed.

It's pretty much McGivered together but it actually worked quite well.


whole setup

I allowed the Ash to sit in the wood bending steamer for about an hour. It was softened by then and I was able to clamp it to the side of the boat to cool and dry in shape. The wood started stiffening as I was clamping the end so there is not a huge working time.

Thicker wood might have taken longer.

When I took the wood out of the steamer it was completely dry. Steam is not wet strangely enough. It is only wet when the water condenses and is no longer steam. The whole apparatus got quite hot but nothing got wet and I had very little condensation.

There is the potential for nasty burns. Not only is steam quite dangerous but the pipe and vent pipe also got very hot to touch. I used gloves to handle the wood and the steamer.


Did it Work?

The wood bending steamer worked very wellf and was cheap and easy to make. The good guys win again. I now will finish bending my wood and dismantle the steamer since I only built this for temporary use.



email me if you find mistakes, I'll fix them and we'll all benefit: Christine