Intro: Bow Stabilizer From Bamboo
Bamboo doesn't quite have the rigidity per weight that carbon fiber does, but by my calculations it comes much closer to carbon fiber than steel and aluminum (at the same diameter and weight, a steel tube will suffer from 3.3X the same deflection in a cantilever than carbon fiber; aluminum 3.2X; while bamboo will be only 1.5X). And bamboo is much cheaper, and stands up to dings better, since for the same weight, the wall thickness is greater. In our region, it can be a weed, and you can sometimes get loads of it for free on Craigslist. And it looks really good.
For those who don't want to read details, here are the instructions in a nutshell: (a) cut bamboo to size; (b) run 5/16-24 bolt through dowel; epoxy inside bow-end of bamboo; (c) put segments of pipe, held in place with drawer liner, around other end or attach a 1/4-20 bolt on that end for commercial weights.
I was making a stabilizer for a target recurve, and I wanted it long: about 32". I used a nice piece of dry 1 1/8" outer diameter bamboo. For hunting, I'd want a shorter piece.
There are two ways of making the stabilizer take on weights. One way is for it to simply have a bolt with some standard 1/4-20 thread on the outer end for commercial weights to screw on. I will discuss how to do that. The other way is what I actually did, which was simply to attach segments of PVC or aluminum tube on the end, with some vibration dampening friction-fit.
- Bamboo stave, at least 1" diameter
- 5/16-24 bolt or segment of threaded rod, approx. 2.5" long
- washer with outer diameter roughly matching the bamboo
- dowel of outer diameter as close to the inner diameter of the bamboo as you can make it, approx. 1.5" long
- enough rigid epoxy (e.g., JB Weld) to fill the gap between dowel and inside of bamboo
- tubing, steel pipe or PVC pipe/conduit with inner diameter somewhat bigger than the bamboo
- drawer-liner material
- 1/4-20 bolt or segment of threaded rod, approx 2.5" long
- another dowel piece of about same size (unless the bamboo is significantly narrower there)
- another washer
- more epoxy
Step 1: Choose and Cut Bamboo
Choose a piece of bamboo that is as straight as you can get it over the required length. Ensure that there are no splits. Longer stabilizers may need to be thicker for more rigidity. I went with 1 1/8" outer diameter at around 32" in length.
At the bow end, you want about 1.5"-2" of straight bamboo segment without septa (the septa are the joints) for the dowel that will hold the bolt. At the outer end, you will want the same if you go for the commercial weights, or about 4" if you go for the weights made from pipe (and if you do that, you will have less effective length, so you may want to cut longer). If the bamboo tapers in one direction, the wider end should be the bow end.
Bamboo is a kind of tubing, and I generally cut tubing by taping a wide strip of paper around where the cut line is and to the tube, and then I use a hacksaw (or for cardboard tubes, box cutters), trying to go all the way around before cutting through. Use fine teeth on bamboo not to cause the bamboo to split, and be gentle.
Step 2: Prepare Bow-end Insert
Choose a 1.5-2" length of dowel that fits as closely as possible inside the bow end of the bamboo. If you have a lathe, you can do a great job here. Otherwise, you'll fill the space with epoxy.
Standard stabilizer thread on the bow end is 5/16"-24. Drill a hole down the dowel for a 5/16"-24 bolt which will stick out the right distance for your bow's thread.
The hole I drilled came out crooked--I think it may have shifted in my home-made drill-press vise--but it doesn't matter too much, since one can compensate later by gluing in at an angle.
Then glue bolt into hole. I foolishly put super glue in the hole and got the thread dirty and had a lot of work with acetone to clean it. Better move would have been to just let a bit of glue work its way up along the bolt with capillary action, or just glue the bolt's head in place. Many options here.
Then test fit inside the bamboo, checking how to make the whole stabilizer as straight along the bolt as possible. I used a toothpick to help fill the gap.
Step 3: Glue in Bow-end Insert
Use a rigid epoxy to glue in the bow-end insert. You want the bolt as much as possible along the axis of the bamboo. Because bamboo isn't as straight as manufactured materials, you may need to angle it in the hole to get it along the main axis, because the end segment may not be straight.
While you're at it, cover the cut end of bamboo with epoxy (I really should have done it for both ends, but didn't think of it) to prevent it from sucking up moisture in the future. (The outside of the bamboo is covered with a natural wax, so it should be somewhat water resistant.)
And glue on a washer to cover the end neatly and protect the bamboo end (I used a fiberglass one, as I got a lot of them cheap once).
Step 4: Commercial Weights Option: Adapter
Repeat Steps 2 and 3 with a 1/4-20 bolt at the other end to fit commercial weights (at least, I think that's their thread--I don't actually own any). And you're done if you're going for commercial weights.
Step 5: DIY Weights Option: Making a Weight
Experiment as the weight you need. I tried no weight as well as a 4 oz section of aluminum tube, but I think what I will go with is a 2 oz section of 1.25" nominal SCH-40 PVC conduit. This conduit weighs about .6 oz per inch, so I cut a little over a 3 section. I wrapped the end of the bamboo two-ply thick with a strip of drawer liner, and threaded the conduit onto the bamboo.
I haven't tried the final version, but when I used the 4 oz aluminum version, with a single ply of drawer liner, I had great vibration suppression, and the bow was noticeably quieter. But it was a little too heavy.
You can trim off the extra drawer liner.
There are many other options for DIY weights.