Author Topic: Compression Woods?  (Read 27430 times)

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Offline joachimM

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Re: Compression Woods?
« Reply #75 on: February 27, 2017, 03:00:25 am »
The invitation extends to anyone who can provide that info for a 50lbs or les bow that can shoot a 500 grain arrow faster than 170' per second. Specifically the sode profile and force curve is what i'm really interested in examining.

Greg, read chapters 5, 7 and 8 in TBB4 (design and performance revisited; The mass principle; Flight archery). All your answers lie there.

To boil it down: the easiest way to make such a bow (IMHO) is a broad pyramid bow with pencil-thin nocks (Ishi-pyramid style bow, TBB4 p 125. But there are many ways to skin a cat... The mass principle and thin outer limbs will get you there.

Offline Selfbowman

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Re: Compression Woods?
« Reply #76 on: February 27, 2017, 06:44:03 am »
It might can be done from any wood with proper placement of mass. But here goes on some Osage .69 " long  Total  mass 23-26oz.1-1/2 at fades, 10" handle, 1-1/2to 1-1/4 at mid limb , 1/4-1/8 at tips. 3 in reflex that holds not taking set. Tillered to 50# at 28" will get you there. It's that easy. I don't know what kind of grade that will get ya but the rest of the info you can get on your own. It should not take to many bows.lol   Arvin
« Last Edit: February 27, 2017, 06:50:57 am by Selfbowman »
Well I'll say!!  Osage is king!!

Offline loon

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Re: Compression Woods?
« Reply #77 on: February 27, 2017, 08:57:35 am »
TBB4 p 125
What I hate about the e-book is that I can't find the corresponding page  >:(

Eventually found it though. "A Combined Ishi-Pyramid Bow". The corresponding location number is 275.6...

I'd rather do a stiff handle though
edit: no. unless i changed something requiring a different design (ie a longer bow), but for a mid-length mid-draw length as the book says, slightly bendy is excellent
« Last Edit: March 01, 2017, 06:46:27 pm by loon »

Offline joachimM

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Re: Compression Woods?
« Reply #78 on: February 27, 2017, 11:32:42 am »
TBB4 p 125
I'd rather do a stiff handle though

Why? Just because or do you think there's a good reason that a stiff handle will be better? Put it another way: why change a proven design, and risk making it less good?

Offline gfugal

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Re: Compression Woods?
« Reply #79 on: February 28, 2017, 07:53:27 pm »
Bone? Bone doesn't actually take a lot of bend.  Korean bows have been made with bamboo bellies. Bamboo doesn't really take more set than wood. It wouldn't make a fishing rod if it took set.

If I take data on the elastic modulus for bone, plus ultimate tension and compression strengths (from this 1974 paper http://dx.doi.org/10.1016/0021-9290(74)90018-9), it indicates that bone fails in tension at an elongation of c. 0.8% (which is less than most bow woods), and fails in compression (beyond the yield point) at a compression of nearly 1.2%, which is better than any wood. but it's darn heavy (SG c. 2.0). For its mass, it stores about the same amount of energy (in compression) as good bow woods. Overall, I'd say it's not that good that you should consider it as a belly material, unless you have no wood to work with, like inuit people did.

I see no reason why you'd use bone if horn or even wood is an option.
Do you know what the elastic modulus under compression was for the bone? I can't read the article cause you have to buy it. Do you have it downloaded?
Greg,
No risk, no gain. Expand the mold and try new things.

Offline PatM

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Re: Compression Woods?
« Reply #80 on: February 28, 2017, 08:35:58 pm »
One thing you may want to consider with bone is that it is designed or evolved to be continuously repairing itself from stress.  It degrades under stress and then needs to heal from that.

 Trees and horn  grow and  then don't do much after that.

Offline joachimM

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Re: Compression Woods?
« Reply #81 on: March 01, 2017, 05:15:30 pm »
Quote
Do you know what the elastic modulus under compression was for the bone? I can't read the article cause you have to buy it. Do you have it downloaded?

Sorry. Go to http://sci-hub.bz and enter the doi of the article, start reading!

Offline Springbuck

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Re: Compression Woods?
« Reply #82 on: March 01, 2017, 05:23:46 pm »
Basically, those are not the qualities I would look for in a bow. I want both high MOR and MOE: such bow would (for the same bow mass) require more force to be pulled (hence storing more energy per drawn inch) AND be allowed to be drawn far. And you want this not only in tension, but also in compression.


Exactly.  This is what stiffness is all about.  Some of those woods they listed ARE stiff, elastic, and rupture resistant,, like osage, but most woods are "pick any two" kind of deal.

Offline willie

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Re: Compression Woods?
« Reply #83 on: March 01, 2017, 05:45:02 pm »
Quote
Go to http://sci-hub.bz and enter the doi of the article, start reading

 :) :) :)

Offline Springbuck

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Re: Compression Woods?
« Reply #84 on: March 01, 2017, 05:49:14 pm »
"Regardless, you gave me an idea for the Next Generation Bowsubmerge the surfaces that will become the back of the bow in vinegar for 1 week."

I hope you are kidding, but ni case not.... yes, bone is a composite material, with heavily calcified tissue and collagenated tissue all mixed in together on a MOLECULAR scale.  You can't remove either by scraping, you can only expose more of the same, which is both types mixed in.  The spongy part is trabecular bone,  and the hard, solid part is cortical bone, and they are different structures laid down by the bone cells (called osteoblasts) but are mostly made of the same materials.


Offline Springbuck

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Re: Compression Woods?
« Reply #85 on: March 01, 2017, 06:44:03 pm »
Greg, only a few die-hards that I know of willingly reject other woods besides osage and yew.  Almost everybody on this site hold.....preferences?  at the worst.  I'll tell you what, though, osage acts basically like it WANTS to be a bow.....

I don't fault you at ALL for your quest for knowledge.  As I said elsewhere i did it myself.  I'm like a big 4 year old and always have to ask "why?".  It's the ADHD, man!

     BUT, I can also add that much of what I wanted to know was being told to me by some of the old timers way back then.  The issue was they would tell me, but never tell me why.  Regardless, much of it was simply correct and I could learn why as easily by following their advice as by questioning it.  I'm not scolding, I promise. and, i still love theoretical and didactic learning.  We've all done one little thing that nobody else has, but it's mostly a method, not so much a major tweak of the final product.

  Most of my own quest and questions went like this, "I wonder why they say you can't just do it like this.?.......BLAM!  Oh, that's why!   Hmmmm...."  But, I say, never stop!

  Hang around a while and we'll have this whole conversation again next year.

 

Offline loon

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Re: Compression Woods?
« Reply #86 on: March 01, 2017, 06:50:26 pm »
TBB4 p 125
I'd rather do a stiff handle though

Why? Just because or do you think there's a good reason that a stiff handle will be better? Put it another way: why change a proven design, and risk making it less good?
Yeah, but it's only drawn 23".. 23*2=46, and total handle area is 8, so 54 minimum for a stiff handle bow, and it's 59 1/4" ntn. But it's still very fast at that draw length.


lol, all this osage worshipping, it still breaks if you don't chase the ring properly? more than hickory. And no one seems to think it can make a good bow 50" long with 32" draw length, if sinew backed, while bamboo apparently can.. (i know it's a grass)
« Last Edit: March 01, 2017, 06:56:24 pm by loon »

Limbit

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Re: Compression Woods?
« Reply #87 on: March 01, 2017, 11:11:40 pm »
I am not sure anyone is still interested in considering the bone option due to the weight of the bone, but if you are interested in where the idea came from, you can look at the video below on how to construct an asiatic composite bow by Jeffery Schmidt and John McPherson on youtube part 3 when they are discussing belly material. Antler, ribs and bone are mentioned as usable replacements for horn, but again, it is doubtful they would work as well as horn as mentioned by others comments on this thread. However, it is worth noting that it isn't a far-fetched idea. https://www.youtube.com/watch?v=h2Ehd1FXsVk

Offline joachimM

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Re: Compression Woods?
« Reply #88 on: March 02, 2017, 01:40:36 am »
loon,
You can only convince people that its possible to make a good 50" bow drawing 32" by actually making it. If you think so, you gotta start making shavings.