Bamboo Recurve Build Along

By Sam Harper

Making the form

The first form I made was from a 2x6 I liberated from a construction site pile of garbage. Sticking with tradition, I also liberated this 2x6 and 2x8 from a pile of garbage at a construction site.

***EDIT***

This 2x6 actually turned out to be a 2x8, which resulted in me having too much deflex in this bow. I was perplexed why this bow turned out to have too much deflex when my original two recurves didn't. I just found out today (July 2, 2013). Mystery solved. So anyway, if you decide to do this build along, use a 2x6, and you shouldn't have too much deflex like I did.

It was easier this time, though. You see, my brother-in-law’s brother is building a new house, and since my brother-in-law is working on it, I just told him what I needed, and he helped me find it.

It’s really important not to get a board that’s warped. Mine was not warped lengthwise, but it was a little warped widthwise.

I planned on cutting that 2x8 in half and gluing it to the ends so I’d have enough room for my recurve, but as you can imagine, with my 2x6 being warped that way, it would’ve resulted in my tips being misaligned. To fix that, I used my brother-in-law’s table saw to square off the edges of the board.

This picture shows a cross section of the board. The area in red was removed by the table saw. I’m exaggerating the amount of warp in my board so you can see why I needed to run this through the table saw. I suppose a jointer would’ve worked, too. If the board had really been as warped as this picture shows, I probably wouldn’t use it.

I did the same thing with the 2x8. Although it wasn’t noticeably warped, I figured it couldn’t hurt. I took these pieces home, cut the 2x8 in half, and glued it to both ends of the 2x6.

Fate would have it that my 2x6 was already 64” long when I got it, which is about what I wanted it to be anyway. So I didn’t have to cut it to length. My original form was 64.5”, but this’ll work.

Once the glue (i.e. Titebond III) was dry, I drew my shape. I drew a line 2 inches from the end and 2 inches from the bottom. Then I placed my great big ole salad bowl lid to where it was tangent to both of those lines, and I drew around it. That's going to be my recurve.

The salad bowl lid has a diameter of almost 13 inches.

Next, I found the center of the form and made a mark at the top, 3.5 inches on either side. I used my aluminum yard stick to draw a line from that mark to the tangent of the circle I drew with the salad bowl lid.

I did the same thing on the other end, then I cut it out with the bandsaw. That was not easy because the whole thing was kind of heavy. It would've been easier with a lovely assistant who could hold one end of it. I cut off the top 5 inches of those 2x8's first, which helped.

When you cut out those curves, you should at least try to cut one out perfectly rather than cutting slices down to the line and taking it out piece by piece. The reason is because you're going to need one of those cut outs to pre-bend your bamboo backing.

I also cut out the bottom corners. Although I'm going to use the rubber band method of glue up for this bow, the rubber bands just aren't strong enough to get a good glue line in the curve area, so I'm going to use clamps there. It's easier to use clamps with those corners cut off.

Now that I've got the form cut out, I used the belt sander to round out the handle area and smooth out the limb area.

You might wonder how I keep everything squared. Well, I'm just careful, and it may not be perfect. It is important to get a smooth transition between the straight part of the limb and the curve. Once I get the limb straightened out with the belt sander, I used a drill press with a sanding drum attachment to perfect the curves.

You may not be able to get everything perfectly smooth using the belt sander and the drill press. But what you can do is grind a lam of bamboo or whatever and glue it to the form. That will smooth out any bumps or imperfections. I managed to get mine pretty smooth, so I'm not going to worry about that.

The final step is to drill holes in it, put dowels through the holes, and make some rubber bands. Then the form will be finished. To get free rubber bands, all you have to do is go to any bike shop and say, "Do you have any inner tubes you're throwing away?" Inevitably, there'll be somebody who doesn't mind sticking his hand in the garbage and getting you an inner tube. One inner tube is way more than enough. I'm using a ten speed inner tube and cutting them about 1/2" wide.

I drilled 3/8" holes 1" from the top and spaced 1" apart. Then I stuck 3/8" dowels in there that were anywhere from 3" to 3.5" long. Then I hung the rubber bands from the dowels.

My original form had them going all the way around the curves, but after discovering that I'd have to use clamps there, I decided it wasn't necessary. It's still useful, though, if you want to glue a lamination to your form to even out the bumps.

With my set up, I stretch the rubber bands straight across, and they barely make it without breaking. If you happen to have fatter inner tubes, you can criss cross them to get more stretch.

I have mixed feelings about the inner tube method. On the one hand, they give you even pressure, and you can vary the pressure by putting more rubber bands on there. It also prevents the lams from sliding around during glue up. On the other hand, if you put too many rubber bands on there, there's nowhere for the glue to go when it gets squeezed out. Sometimes, it'll pop through the plastic wrap and glue your bow to the form. Another option, I suppose, is to make a two-sided form and use the fire hose method.

And that's it. The form is done.

to be continued...

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