Bamboo Self Bow Build-Along

[KenH]

A couple of folks asked me to show the steps I take to make a self bow from a bamboo fence slat.  

1.  Using a belt sander, flatten the 'inside' of the slat to remove the interior ridges from the culm.  The thickness of the 'plank' at this point is the primary determinant of your final draw weight.  You want a plank that is 3/8" to 1/" or more thick

2.  Mark the profile on the 'inside' of the slat, arranging the profile so that either there is a node at the center, or (as I did here) a balance of nodes either side of center.  Here' I've drawn a fairly standard flatbow 1-1/2" wide at the fades and 54" long.  Balancing the node placement gives the 'plank' relatively even bending, the first stage of tillering.
   

3.  Again with the belt sander, taper the plank to the profile shape of the bow.
   

4.  Add the tip overlays.  With bamboo bows, some form of overlay is important because of the straight grain nature of the "grain".  You want something harder than bamboo to take the tension of the string.  Here I've used oak to form an Asian style overlay which of course gets sanded and final shaping.  Since this is a wood-wood joint I've just used TitebondII as the glue.
   

5.  Next put on a string.  It doesn't have to be the finished string, just something that will put the bow under tension.  Now you use your tillering tree and a block sander or electric palm sander to 'fine tune' the tillering, by sanding/scraping away the BACK of the bow, not the belly.  
     

Once you get the final tiller you can finish the bow by painting/staining the back if you choose, or simply apply your usual sealer.  I particularly like Tung oil.  

If you want a palm-filling handle, don't try to glue one on either side of the bow.  Trust me, the glue will break, and that could break the bow.  You can bind a wood or bamboo handle in place, or use something like slices of belt leather glued on, shaped and then wrapped with cord or leather strips.

[BMorv]

That's pretty cool!
How long does it take you to complete one?
Are you concerned with the moisture content of the bamboo?
What's the max draw length on one of these?

[Mad Max]

Thanks Ken
that's pretty cool.

[KenH]

I live in Florida, so moisture content "is what it is.  Bamboo grows locally.  I would not use "green bamboo"  Always use 1-2 year old culms -- mature but not dead.  Max draw length?  I don't build for long draws, but I am working on a cable-backed bamboo bow, like I saw in TBB#1 -- draw length should be out of sight!

[Roy from Pa]

Sweet...

[KenH]

If (sometimes that a BIG word) I have a whole day in my decently cool garage/shop, I can make one of these in a day, easily, or even in a morning.

It does take a couple hours for the glue to dry.  If I had more powerful power tools or different tools it would go faster.

Sanding/grinding the profile, in particular, would be minutes with a bandsaw rather than an hour with my upside down hand-held belt sander with a 40 grit belt.  Sanding/grinding the plank from concave to flat would go a lot faster with a horizontal belt sander with a 36" or 48" blade.

One thing to note on these bows is that you do not want to "compromise" the skin of the bamboo on the belly side -- no cuts or anything like that. Having that intact radiused surface is as important as a good glue job on a wood-glass bow.

[neuse]

Good stuff, thanks for the post.

[inksoup]

cool stuff... thanks for posting.

[KenH]

Just as a followup:

It can be hard to find anyone selling just one or two bamboo fence slats.  I've found two places:

EchoArchery.com -- they sell unworked "backing slats" for $14.50 each

BambooSupply.net -- physical stores in Benecia, CA and Lakeland, FL.  Their 72"x2" slats are $6 each.

With shipping, either place will cost you about $25 for 1-2 slats.  I drove up to Lakeland last time (about an hour) and picked out the ones I wanted; but not everyone can do that.  

If you're interested in a youth/beginner build-along project, you could buy a bundle of slats and make a bunch of bows pretty inexpensively.

If you live in an area (like I do) where 4"-6" diameter bamboo grows, you don't want to harvest this year's culms.  You want culms that are 2-4 years old.  Standing live stems, not dead stems can be harvested and dried horizontally in an unheated space (garage rafters, wall rack, etc.) for a year or so before being split and used.

[Roy from Pa]

Ken, I buy whole bamboo kiln dried poles from a place in Florida. They are about $35.00 a pole. I buy Madake bamboo. Pronounced Mah-dacki. I get 4 to 5 bows from one pole. Call and ask for Jennifer, tell her it's for bow making.

  http://www.beautifulbamboo.com/runningbamboo.php

[wood carver 2]

X2 for Echo Archery.                
Most others won't ship to Canada.
Dave.

[KenH]

Roy -- that place is 3 hours from my house (maybe 45 minutes beyond Bamboo Supply.  I'll give them a try next time I buy bamboo.

[Mad Max]

Ken
why is the outside being used for the belly?

[KenH]

That part of a culm slat is better in compression.  You see bamboo bows made both ways, but the consensus is that they are more efficient and generally "work better" when the unbroken outer skin of the culm is used on the belly rather than the back.  Most of the older Asian cultures which made bamboo bows used them this way.  Granted it's easier to bend a given slat towards the flattened inner side, but it's just not as strong.