Steam-bending Second Stringer Using PVC Pipe

As you saw in the previous post, the wood I used to build a steam box was too thin and split in half on both end caps.  Rather than repair it I decided to build a  new steam box of PVC pipe.  It turns out PVC pipe works very well for this purpose, and saves a lot of time and effort building a wooden steam box for every project.  There was some worry that the pipe would melt or sag but that was not the case.

 After assembling the steamer box using a 5' x 4" PVC pipe with end caps, I ran the steam generator at 212 degrees as a test for over an hour with no ill effects to the pipe.

 Just in case the pipe might sag in the middle, and to keep it from rolling I cut a groove down the middle of a 3' board and  placed it under the pipe.  A block under the front end of the board causes water to flow to the drain hole at the rear end of the pipe, the end where the steam hose connects.

Rather than drill holes in the sides of the pipe and put dowels in to support the stringer, I simply placed several small blocks inside.  The stringer is sitting on the blocks, so that steam can reach all sides.  There is also a block supporting the thermometer--probably not necessary.

The end cap has been screwed in place and the steam generator started.  You might be able to see a small hole in the cap to allow excess steam to escape.

 Condensed water flows to the rear end of the pipe and out a drain hole into a bucket.

Luckily I had a set of very long tongs which were helpful in removing the stringer after steaming for an hour.  The green sponge is to catch a small amount of water that flowed around the side of the end cap.  I decided not to glue the end caps on because I do not know how the heat will effect the glue, and so I can use the same end caps with different lengths of pipe.

While it is still hot, the stringer is quickly clamped onto the form. After a couple days, I'll remove the stringer from the form.  The next step is to cut a new breasthook and attach the stringers to it. Attaching the stringers and breasthook to the boat presents some problems, but I'm starting to work them out.  The original stringers were hand-bent cold, but they extended 8 feet back on to the boat.  Trying to duplicate that bend on the two-to-three foot replacements required steam bending.

Steam-Bending Stringers

Things went fairly well on the first stringer, except for a couple minor hitches.

A little hard to see but here is the bow section of the plans "lofted" onto a piece of poster board.  (I had to tape a small piece in the lower left corner to get the whole thing to fit.)

I forgot to take pictures, but I laid the poster board on a piece of 3/4" plywood and drove a finish nail at each station point.  The station lines are the vertical lines in the drawing, 6" apart.  I then used a thin piece of wood as a "spline" and bent it around the nails to guide my pencil.  I cut out the curve on the plywood and drilled holes for  the clamps.

The steam generator is busy pumping steam into the steamer box.

This is just a meat thermometer.  The temp is exactly 212 degrees. 

Looks like I should have used thicker wood!  This is only 1/2" lumber.  The temp dropped to about 208, then I put some duct tape over the split and got it back up to around 210 for the last few minutes of steaming. 

The split did not cause any problems.  The wood bent very easily around the form.  Here you can see it clamped and ready to set aside for a day or so to cool and pretty-much retain it's shape.  I could put thicker doors on the box for the second stringer, but I think I'll try the PVC pipe method that a lot of people use.  More about that in the next post.

Steam Box: Ready to Begin Repairs Now That Camper is Finished (almost)

I ordered a Steam Bending Kit from Rockler some time ago and finally got around to building the steamer box for it.  The steamer will be used to bend new stringers into the proper shape to fit the bow.

Today I'll get started on "lofting" the small part of the plans for the bow of the boat. 

The next step after that is to build a form for the stringers, which I also hope to start on today.  So far, it looks like the weather will remain perfect for epoxy work for a while, so I hope to get out there and get started very soon.