Primitive Archer
Main Discussion Area => Bows => Topic started by: Onebowonder on August 24, 2016, 01:42:05 pm
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All,
I have a few pieces of pipe straight ERC, but they are only about 2 1/2 to 3 inched in diameter. Very few knots, but there are some. I've sawn the round wood in half on the band-saw. I'm wondering about making the flat middle of the wood into the back of the bow, ...kinda like a backwards bow. I'm thinking to either bamboo back it or sinew back it. Since ERC is most comfortable in compression, I thought this might improve the possibility of the bow tillering out well.
What do y'all think? I've never tried a backwards bow except for green wood survival bows. They don't last very long. Would the idea be likely to work or more likely to blow up in my hands?
OneBow
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ERC, like other junipers has sapwood that is good in tension and heartwood that is good in compression. I would think that by adding a boo baking so the sapwood is the compression side the boo might overpower the belly. This is just a guess on my part. If you have enough heartwood, boo backing might work for that.
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ERC has go compression but the sapwood tension is not that good at all...thats why it needs to be backed
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Id like to see that done Eric, but first chase a ring on the belly below the sapwood. Then do tje bow pyramid style and tiller it to look like a good elyptical bow would resemble, but tiller it from the side that will get the bamboo. Get it bending to the point it looks like it would be a 20 pound bow, then glue on the bamboo backing. That will bump the weight up perfectly to a heavy weight bow. If you tiller the bamboo out to perfextly match the tiller of the erc, you shouldnt have to do anything but mayne a touch of side tiller to bring it around into shape. And if its too heavy, aggressive rounding of the corners will drop it down.
Matter of fact, if its the bit of cedar i think you have, I will try that myself with my half.
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Funny thought. If it develops set, just turn the bow bacwards and shoot it the other way. It would be an erc back boo bow. Then flip it again when it gets set that direction and make it a boo back erc.
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I don't think I had an appreciation for the idea that ERC sap wood was more tension strong than the heart wood. Those few I've made have always failed in tension so I assumed the whole species was weak in tension. I keep coming back to it because the stuff is so light and so pretty, but it continues to frustrate me. Also, it's fairly plentiful around here.
Sleek - This question is in reference to the one I dried and sawed in half that you cut in Oklahoma. It has a REAL HIGH ring count for such a small stave. I don't know about the flipping it around idea. :o It seems the tension side and the compression side could not readily be swapped without destroying the bow. ...but I suspect you might have been joking a bit. :P
OneBow
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If you're going to back it anyway wouldn't it be worth considering taking both pieces and flattening both side and laminate them together, kind of an ERC-ERC-Boo trilam? I'm no bowyer just read a lot on this site and I'm mostly just thinking out loud.
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Eric, i cant recall the ring count, can we get a pic? And, i was only joking about shooting the bow in reverse, a little.... I have done that before.
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Here's a pic of it's cross section. I count right about 50 rings more or less and the radius is well under 2 inches, so for ERC, this seems kind of HIGH to me. I don't know that it mean very much for ERC to have a high ring count. I'm given to understand that it matters somewhat with yew and some other slow growth woods, but not sure it does with ERC, which generally grows like a WEED! I'm sure it means that this tree is nigh as old as I am though. 8)
OneBow
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Eric often times woods break in tension because the compression is so weak the back takes all it can until it goes ka-pow. Frets will usually happen first, but not always. Excessive set is another indicator. Of course you can add about 2500 variables to all that.
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A few years ago a guy brought an all sapwood ERC ELB style bow to my camp-o-rama. I was very surprised how snappy that bow was and it had very little set. I think it was 45# or so.
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No matter what I think a bit of decrowning might be involved from a small diameter stave as this.Belly or back.
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I thought it had more heartwood than that. Still, your idea would work. Just whatever you do, maximize the heartwood in the belly regardless of orientation.
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why not leave the crown if it's weak in tension? it"d be like a natural "trapped" back no?
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Loon, you got that backwards. If its strong in tension a crown is ok. If you crown a tension weak wood you increase strain on it.
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Agree with Ed. Trapping the back or leaving a high crown would be a bad call on tension weak woods like ERC. You would leave a crown or trap the back when you have a wood that is stronger in tension than compression. That comprises most of our bow woods BTW. ERC, and a few others being the exceptions.
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oh
Yeah, that makes sense haha. Then tapering to the belly would make more sense?
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Yep, but narrowing the belly equals widening the back. Decrowning will accomplish that.
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Yep, but narrowing the belly equals widening the back. Decrowning will accomplish that.
Exactly. But, with bamboo being glued on as is his plan, he just needs to get the back flat, and have as much heartwood on the belly as possible. Ring orientation wont matter.
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I think i would keep sleeks half , sorry sleek😋, and i would try and get 2 slats of heartwood and glue up a tri lam with boo or maple and go a slight d/r
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There ya go with bubs idea but if bamboo is involved with red cedar in a combo the cedar needs to be flat[maybe with maple] to compensate against the bamboo and the bamboo can be crowned.Toast the bamboo first too.Just a wild mean thought....ha ha.
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Onebowonder....One thing about the end of that stave there.The heartwood will be variable all through out that stave.In and out of the sapwood along it's length.Some places more than others.No harm in it though.Just so you know that already.
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That aughta make it look cool if it comes through the belly.
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I say saw off the back near to right down the middle and belly side so you get just a little trapped belly, flip the tips slightly, and sinew the snot out of the back so it regains it's crown. I think it would be a beauty with the sapwood sides and red belly.
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So, weak at the back means the back is less stiff, not more brittle?
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A back has to be strong in tension, a belly in compression. It may just be semantics but I don't think brittle is a good description. Stiffness, I think, just determines how much wood you're going to need. For example Yew bends very easily, so you need more of it to reach a certain draw weight. Ocean Spray ,on the other hand, is like a steel bar and you need a lot less to reach the same draw weight. I often wonder if stiffness is just a function of SG???
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I think brittle is a pretty good description for some woods. Mostly from a tension standpoint. Black Cherry, I would describe as brittle. The back can at some point just snap like a candy cane. Some woods can be heavy and yet lack elasticity. If it is lacking it in tension, then it can seem brittle. Live Oak, based on my limited experience with it. If lacking in compression, then it tends to take more set. Hackberry I would put in the last category, though it can be greatly improved compression wise by heat tempering.
I think the key is either starting with a wood that has a good balance between compression and tension elasticity, Osage as an example, or bringing those things into balance thru design and modification (tempering, trapping etc..).
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So, weak at the back means the back is less stiff, not more brittle?
It means too stiff, and as a result, more brittle.
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Slimbob, you mentioned black cherry and bow in the same paragraph. My hair is actually standing on my neck and back of my arms remebering the pain. I had a black cherry bow backed with silk. It blew on me at full draw. I wasnt wearing a shirt. The flying limb struck me in the left nipple. I actually thought it was ripped off it hurt so bad.
I will pee on an electric fence before I ever pick up another piece of black cherry.
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The most violent break I have had was with Black Cherry as well. A buddy of mine was watching as I drew it back and BLAMM! Shrapnel everywhere. I short drew everything for months after that.
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I've had black cherry chrysal on the belly on a 4" resting reflex sinewed bow.64" long to boot.It took thousands of shots for them to appear but they did.Overall though I feel black cherry in a less stressful design tillered properly is safe and would make another myself sometime.
To me from my experience black cherry and cedar both are brittle cousins,but if made properly with just a little reflex and enough length they are impressive to me and very sweet to shoot.I've had my episodes with red cedar too....lol.
Onebowonder.....I will stick my neck out and seriously tell you my thoughts all cedar blowing hard hat jokes aside.I feel if you decrown[which needs to be done] & back that cedar stick the denser or thicker the material[bamboo] used for a backing the flatter the belly I would make.The thinner and less dense the backing[maple] the more shallow D shape you can make the belly.Balancing the back to belly with the forces.Really though I'd make the belly flat with either backing......lol.The less decisions making a bow the better I say.2" wide and 68" long with just a few or couple inches of reflex that's all.Even D tillered bendy handle too but I'd eliptical tiller it myself.Even that long of a bow with the light mass cedar has no hand shock should be evident at all.It should live a long time too.
Now the other backing...mother natures FG...sinew!!!I'd decrown your stave/taper your limbs/reverse brace it slightly[just a couple of inches] and sinew it with a 1/16th inch thick dried layer of tapered sinew crowning it some.It's worth a try that's for sure.I did'nt read how long your cedar stick was though.
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My grandsons Father has an Eastern Red Cedar bow that is acked with Bamboo Brian Melton made, I think back around 2006. 55# at 28" and he is still shooting it. It is nothing but a simple rijid handle, flat belly bow.
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Thanx for all the great suggestions! After reading them, I'm more inclined to just decrown and flatten the sapwood side and put the boo on that side...
OneBow