Author Topic: Bamboo in high stress designs?...  (Read 1816 times)

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Offline toomanyknots

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Bamboo in high stress designs?...
« on: June 06, 2013, 12:28:21 am »
Just wondering what everybody's take is on this. I mean short heavy reflexed bows. Not too short. I just had an experience with a bamboo backed r/d which was about 60" ntn, it was probably going to be around 65 - 70 @ 28" I think. Lots of reflex in the outer limbs. It was looking beautiful, but than it popped a splinter. Long story short, there is now a bunch of r/d bow pieces all over my little work room. (my ipe seems like it likes to splinter and break apart too, hmmm.) Anyway, I feel like the high I was getting from making these bamboo backed bows is now over, since I now know that bamboo is not invincible natural fiberglass,  ;D. After researching the net a bit, it seems "bamboo lifted a splinter" is a very common topic on bow building forums. I am wondering exactly how durable a bamboo backing can be, and how it weighs up to say, hickory. I love me some good hickory, more than any other backing I think. I just made a 65# @ 28" bamboo backed ipe longbow, so it is at least holding at weights and designs like that for me. I believe I have "moso" bamboo, but am not 1000 percent sure of course. Apparently neither is the supplier when I called today. He said it could be tonkin or moso. I thought tonkin was more expensive and smaller, what I bought was 8 foot long 2 inch wide planks, 25 for 125.00. I would post a link, but it is against the rules to post links to places that aren't advertisers on primitivearcher I think. Is moso cheaper and more common? I have heard moso is not super great, and tonkin in actually the best? Is this true? As a side note, I did sand and scrape the bamboo on that r/d more than normal, so that might of had something to do with it.
"The way of heaven is like the bending of a bow-
 the upper part is pressed down,
 the lower part is raised up,
 the part that has too much is reduced,
 the part that has too little is increased."

- Tao Te Ching, 77, A new translation by Victor H. Mair

Offline PatM

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Re: Bamboo in high stress designs?...
« Reply #1 on: June 06, 2013, 01:43:59 am »
Moso is the standard type of bamboo that is milled and sold as 'two inch wide strips. It is well known for popping splinters.
 Google some images of 'power fibers and you will see the difference between some of the types.
 The only thing that Moso has in common with Tonkin is low node profile.

Offline Gordon

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Re: Bamboo in high stress designs?...
« Reply #2 on: June 06, 2013, 02:33:38 am »
If it's 2 inches wide, it is not Tonkin. I've had splinters lift with Tonkin backing so it is not invincible either.
Gordon

mikekeswick

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Re: Bamboo in high stress designs?...
« Reply #3 on: June 06, 2013, 04:17:30 am »
I've used mozo bamboo many, many times and never had a single problem with it. There is NO way he is selling proper tonkin cane - for a start he doesn't even know what it is and I guarantee you he would know if it was tonkin. Tonkin doesn't grow to large diameters and has much wider spacing between the nodes. A lot of nonsense is talked about tonkin being the only bamboo to use....remember that it is very dense stuff so you need to make it work. In a way it's similar to using high density woods - sure they take compression well but if you don't design the bow appropriately then you will end up with a slow, overbuilt lump!
Don't worry about your ipe - that's normal

Offline toomanyknots

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Re: Bamboo in high stress designs?...
« Reply #4 on: June 06, 2013, 10:19:30 am »
I've used mozo bamboo many, many times and never had a single problem with it. There is NO way he is selling proper tonkin cane - for a start he doesn't even know what it is and I guarantee you he would know if it was tonkin. Tonkin doesn't grow to large diameters and has much wider spacing between the nodes. A lot of nonsense is talked about tonkin being the only bamboo to use....remember that it is very dense stuff so you need to make it work. In a way it's similar to using high density woods - sure they take compression well but if you don't design the bow appropriately then you will end up with a slow, overbuilt lump!
Don't worry about your ipe - that's normal

Well if that is normal for ipe, it seems very brittle and dry, and I am not sure I love ipe that much. The ipe I got doesn't seem to be super fantastic in compression either, I would take a piece of crappy osage cut from my neck of the woods anyday over a piece of this ipe I got. Surprisingly, I am having alot of success with hickory as a belly wood,  ;D. Nothing about bows is making any sense to me anymore, except that there is no absolutes in bow making I am finding.
« Last Edit: June 06, 2013, 10:24:52 am by toomanyknots »
"The way of heaven is like the bending of a bow-
 the upper part is pressed down,
 the lower part is raised up,
 the part that has too much is reduced,
 the part that has too little is increased."

- Tao Te Ching, 77, A new translation by Victor H. Mair