Bamboo backing questions

[chasonhayes]

How do you prepare bamboo for backing? These are questions that I have after hours of reading and watching videos.
1. What is the thickness goal? 1/8"?
2. Do you remove material from both sides or do you only remove material from the inner layers?
3. Do you remove protruding ring material to make it flat with the outer layer?
4. How do you flatten it out? I tried steaming it but that did nothing and it still cracked lengthwise
5. Is it OK to break it in to strips lengthwise so that it lays flat?

I am making a board flat bow 72" long 1 3/4" wide with 8" riser out of a board of very straight grain sapele. I already broke a red oak, a white oak, and a red cedar while tillering. I have been trying to find hickory at a lumber yard nearby but no luck so far. I have a bamboo stand nearby that I can harvest from so makes sense to use it. I don't have any sinew and the only deer I shot this year the processor discarded the carcass even though I asked him for it. I do have a trunk full of raw hides and buck skin from prior years harvest and leather making endeavors. BTW I am a traditional furniture maker so I have wood working skills and tools. My goal is to use what I have on hand rather than buy stuff, hence the wood choices. I also have some nice crape myrtles with 4" diameter trunks on my property. Is that useful for making bows?

[Hamish]

1. Thickness 1/8". There is a difference between how thick flattened boo is when left full width, and what it is once the piece gets trimmed to front shape of the bow. The exposed edge near the tips will appear thicker after trimming.

Many people avoid this by tracing out the shape of the finished limb on the underside of the boo, and pre trimming it, before taking it down to its final thickness. The edges of an ideal trim job, will come to a knife edge, or very close to.

Dean Torges video on the Bamboo backed bow, is probably the best source on how to prepare bamboo.

2. You only remove thickness from the underside

3. For most types of boo, removing the node, will dramatically increase the likelihood of it breaking or pulling a splinter at that point.

4. To flatten, some kind of jointer, hand held electric, or a flat belt sander, is quickest. A knife or handplane can be used but the going will be slow.

I usually bring the slat to its final shape with a handplane, or scraper plane.

5. It is possible to split into strips, a narrow diameter pole of bamboo, so it can be flattened. Most people don't because its a lot more work. You might need to track down a thicker bamboo pole eg 4" dia.

Sapele probably won't be strong enough to resist the compression from the boo. White oak would be my choice of the woods available to you at the moment.

Plenty of guys have made good self bows from crepe myrtle.

[bownarra]

Stop and getting some decent bellywood! Ipe decking boards would be a good place to start.
Sapelle will not make a decent bow. Its not even worth bothering with to try and learn the process.

[Del the cat]

Here's a post from my blog on preparing a bamboo backing strip, but +1 on what bownarra said.
https://bowyersdiary.blogspot.com/2014/11/bamboo-backing-build-along.html
Del

[Eric Krewson]

I think you mean you tried to flatten the arc with steam and your bamboo cracked. To make backing you have to have a bamboo trunk big enough in diameter to cut a slat out of it and remove all the excess material from the inner side to have a flat belly and still have enough width for your backing.

A 4" diameter trunk is about the minimum size for this with larger being much better because your slat will be much flatter on the back.

[PatM]

Hours of reading and video watching should surely have answered all these questions.

[Dances with squirrels]

I make mine 1/8" thick at bow center, that's total thickness to the apex of the arc of the bamboo, not measured along the edge.... and taper it to 1/16" at the tips.... maybe just a hair more.

I too highly recommend Dean Torges' video, Hunting the Bamboo Backed Bow. It answers all of your questions and many more you haven't thought of, yet.

Bowyersedge.com

[Nasr]

Is bow making new to you? If so maybe bamboo backed bows aren’t the way to go. I don’t know much about sapelle but I have used it for risers. I wouldn’t try it for a bow it seemed soft to me but I could be remembering wrong. I have made quite a few bows with white oak and they are really hard to break for me. I think learning about proper grain and growth ring orientation will help you a lot. Also bamboo wouldn’t help with bad tillering. Looking through pictures of proper tiller would benefit a lot more. Red oak is also a good wood I have had a lot of success with. If you are new I would stick to the basics. If you are not new then ignore what I’ve said.

[chasonhayes]

Stop and getting some decent bellywood! Ipe decking boards would be a good place to start.
Sapelle will not make a decent bow. Its not even worth bothering with to try and learn the process.

Thanks for the feed back. You sound like a man with a great deal of experience. I apologize for my ignorance but I love learning and understanding.
                                  Osage Orange                       White Oak                 Sapele
Janka Hardness:         2,620 lbf                               1350                          1,410
Modulus of Rupture:   18,650 lbf/in2                      14,830                       15,930
Elastic Modulus:         1,689,000 lbf/in2                  1,762,000                 1,746,000
Crushing Strength:    9,380 lbf/in2                          7,370                         8,750

These numbers are from the wood database and the material properties for Sapele as far as I can tell are closer to Osage Orange than white Oak. So please tell me what it is I am missing about Sapele that makes it worthless as a bow?
Again I would rather use what I have and I do have more white oak and a ton of ERC, so I don't really want to go by any Brazilian Beech flooring if I can avoid it. It might be an option after I have obtained some skills though.

[Morgan]

I know nothing about sapele, but the wood database isn’t the best resource on whether a particular wood will make a bow. Bows are subject to stresses that can’t be easily quantified and put into a check box like structural lumber. Best option is to try it and see, only problem is that if there is a failure and if you are inexperienced you may not be able to easily tell if the failure is the wood species fault. Conversely you can make a bow out of a hickory sapling that breaks all kinds of “rules” and not break. That is not from skill just very tough wood.

[Flntknp17]

I have made several dozen bamboo backed bows out of at least ten woods.....one of them being sapele, which I played with a couple times.....with poor results.  In every case, the sapele fretted and crushed on the belly even after I thinned the bamboo to the maximum extent possible (which should help to alleviate fretting).

Some research and speaking with a fellow in England who has used sapele successfully a few times leads me to the conclusion that there are either two woods being sold as "sapele", or the heartwood and the sapwood have very different properties.  He agreed.  Some wood sold as sapele is extremely dense and works fine for a bow, maybe not as well as ipe, but it does work fine and doesn't fret.  Other wood sold as sapele is much less dense and appears to be essentially identical to mahogany in how it works and even smells; it is too soft for a belly wood on a bamboo backed bow for sure.....as my two total failures would indicate.  In both cases, the bow fretted before I even got it to brace height during tillering.

My honest recommendation would be to get a hickory board, or even rock maple if you can find a dense one.  Hickory and maple are my two favorite woods to back with boo since osage lumber is not always easy to find and ipe produces dust that can be toxic and I work in a small shop. 

A bamboo backed hickory board bow is about as bomb-proof as bows get.

I used a 6" x 48" belt sander and a bandsaw to thin and flatten my bamboo.  As you noted, 1/8" on the edge will work, but I like the edges a little thinner since the middle will be a little thicker.

Matt

[chasonhayes]

Thanks. I stopped by the lumber yard and dropped $30 on 12bf of rough cut hickory with a straight grain and no knots. I will get started on it this weekend. Should I back it with an 1/8" reversed strip of hickory or should I go with the bamboo?

[Nasr]

if the hickory is straight grained and clean i wouldnt back it with anything. Unless i was trying to add glued in reflex throughout the whole limb. I have however seen some Bamboo backed hickory.

[Flntknp17]

Thanks. I stopped by the lumber yard and dropped $30 on 12bf of rough cut hickory with a straight grain and no knots. I will get started on it this weekend. Should I back it with an 1/8" reversed strip of hickory or should I go with the bamboo?

I absolutely LOVE bamboo backed hickory bows.  Yes, it is true that if the hickory board stave has good grain, you don't need a backing.....but if you use a bamboo backing, you can pull the bow into reflex while the glue is drying and then you can typically finish with a bow that maintains net reflex even after being totally shot it in.  Backing isn't required, but I like it on these BBH bows because of the ability to add reflex, and the extreme durability the boo provides.

Matt

[Eric Krewson]

I made a few bamboo backed hickory bows, mostly in repairs to awfully tillered hickory bows that I saw some of the folks at tournaments carrying. They would show me their bow knowing I was a bow maker and ask what I thought. Being an honest guy I would tell them straight up that their bow had issues, their next question would be "can you fix it".

Being casual friends with these folk I would say yes and take the bow home with me an bamboo back it, looking back I should have kept my mouth shut. Reworking these awful bows took more time than it took to make a new one but the bamboo backing definitely made a silk purse out of a sows ear and made some high performing bows.