Primitive Archer
Main Discussion Area => Bows => Topic started by: sleek on November 11, 2012, 11:34:02 pm
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I have a relatively short 63 inch osage stave that is 2.5 inches wide and has a really high ring count, 21 rings per inch. Chasing a ring will be pointless I think and plan on using the sapwood on this bow as the back of this bow has allot of irregular surfaces full of dips, valleys, and hills that will make chasing a regular ring challenging.
I need this stave to be 40@28. I plan on slightly re-curving the tips for extended draw. Front profile will be the full width of the stave out of the stave for the first 6 inches then taper to a pyramid. The plan is to be able to get more of the stress ( and therefore more draw length ) out the fades than normal with an otherwise normal pyramid profile. I will Eiffel the last 6 inches of the tips and re-curve them to the point of the string almost coming in contact. This will be done with an 8 inch stiff handle.
Any suggestions or cautions I should keep in mind while doing this?
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You should be good I would think. It should turn out just fine.
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Ok bud, but if it breaks, its your fault buddy..... lol...
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I think 2.5" is probably going to be too wide, even with the high ring count. I wouldn't go more than 2" wide but since you lose that extra width for the rest of the pyramid taper, perhaps make the taper almost convex instead of a straight line, allowing for more width through out that taper. With your currently lay out you have plenty of limb length for the draw so I wouldn't worry too much about the design being over stressed, although adding the recurves will decrease your amount of working limb. Unless the recurves are to increase energy storage, I highly doubt they'll be necessary for a 28" draw. Maybe a tiller along will allow us to help you in more detail when building the bow.
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Ok, I will drop down to 2 inches wide, carry that through to 6 inches past the fades then convex the taper. I like that idea. It will be neat looking. The re-curves are for reduced stacking and increase performance. This needs to be the best possible bow it can be, considering its me putting it under the knife...
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While there are certain principles that add to bow performance, dimensionally I feel there are certain guidelines that, if held, will make a bow perform well. The last six inches should taper from 1/2" to 1/4" at the tip and be stiff and have a smooth, not abrupt, taper into those final six inches. Also consider mid limb width, which if it were me making the bow, I'd try and keep under 1.25". If I were you I'd also consider heat treating.
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I dont think I will heat treat due to having the sapwood back, I am trying to keep back tension per square inch down.
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I like ryoons advice...and IMO that's on the long side for me..lol
I'd also chase a ring if it were me and if there is enough heartwood to do so....I've made several osage selfbows with 32nds of an inch rings with no problems
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You could do a backwards bow. Like de-crowning the belly to chase your ring and tillering the sapwood side for wood removal then sinew or rawhide back it.
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Ok bud, but if it breaks, its your fault buddy..... lol...
;D
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Get rid of the sapwood, those rings arent bad. And dont go a fuzz over 1 1/2" wide. Make it parallel 12-13" off the fades, the straight taper to the tips. A 40# bow lets you REALLY cut down on the amount of wood you need. If you leave it 1 3/4"- 2" wide it will be paper thin.
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I was about to argue that there really wasn't any reason not to go ahead and do 2 1/2" at the fades, as performance is barely effected by mass at the fades, and the section of limb right off the fades barely moves anyhow. And at the same time, the section of limb right off the fades is the absolute worst spot to accumulate any set / string follow. For all these reasons, the question in my head is "how wide fades is too wide, before the extra mass starts to out weigh the benefit of low set?". And then thinking again, all that being said, with a 40# @ 28" osage bow, around 63 long with a stiff handle, you definitely don't need even near 2 1/2" wide fades. I just personally wonder whether if it would be a benefit, verses a detriment? - My 2 cents, ;). If it was me, I would leave the fades full wideth, at a straight taper to the tips, and this should be more than enough.
EDIT: Scratch that, don't know what I was even thinking. I would recommend 1 3/4" at the fades, with a pyramid taper to 1/2" at the tips.
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Consider the woods thickness if you leave it that wide. Wide can be a good way to keep set at bay, but if the bow is light in draw and the wood is very thin it will have the opposite effect. Narrow and deeper would be better for sleek in my opinion.
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I agree with Pearl. Get rid of that sap. 1-1/2" wide to midlimb then taper will be plenty of wood for you. Dean
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Consider the woods thickness if you leave it that wide. Wide can be a good way to keep set at bay, but if the bow is light in draw and the wood is very thin it will have the opposite effect. Narrow and deeper would be better for sleek in my opinion.
Ya, 2 1/2" is pretty freakin (ridiculously) wide for a 40# osage bow, on second thought. I've been making too many hackberry bows lately. I would probably go with 1 3/4" at the fades, pyramid taper to the tips at 1/2". I think 1 1/2" fades, or even 1 1/4" would be fine, but 1 3/4" would be easier on set / string follow. Which really ain't gonna be bad either way with this bow?
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We know wood is 8x stronger in depth as opposed to width. Making a bow too wide will result in more set. Especially osage because it will be paper thin at 2" wide and 40#.
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Making a bow too wide will result in more set.
No.
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Ok
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Ok
2" wide fades with a pyramid taper is not too wide. The pyramid design is an efficient and low set design. Yes it is wider than you absolutely need, but it will not induce set from the fades being 1/2" wider. In fact it would reduce set, which is why I would go with about 1 3/4" personally.
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Right on.
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Please explain why a 63" 40# osage bow pyramid bow with 2" at the fades and 1/2" at the tips would in anyway have more set than the same exact bow, but with 1 1/2" fades. This is what your saying. How does that make any sense in any way. :o
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Chase a ring to get your back. 1.5" to mid limb, straight taper to 3/8" nocks. I don't consider 63" for a 28" draw as short for Osage. Close to ideal if the back is in good shape. Just finished a month or so ago, a 63" Osage bow with thin rings. 27" draw. 45 #. Just about the dimensions I've described. I did not flip the tips as it was made for a 13 year old boy. He will draw about 23 - 24" for a few years, so stack was not a concern. I left the last 6 inches stiff which made for a smooth draw and release. Just my 2 cents worth.
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Please explain why a 63" 40# osage bow pyramid bow with 2" at the fades and 1/2" at the tips would in anyway have more set than the same exact bow, but with 1 1/2" fades. This is what your saying. How does that make any sense in any way. :o
As I said before we all know wood is approx. 8x stronger in depth than it is in width.
What bow do you think would take on more set? A bow 1/4" thick by 2" wide or a bow 1 1/2" wide by say 1/2" thick? Both bows are pulling 40@28.
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Please explain why a 63" 40# osage bow pyramid bow with 2" at the fades and 1/2" at the tips would in anyway have more set than the same exact bow, but with 1 1/2" fades. This is what your saying. How does that make any sense in any way. :o
As I said before we all know wood is approx. 8x stronger in depth than it is in width.
What bow do you think would take on more set? A bow 1/4" thick by 2" wide or a bow 1 1/2" wide by say 1/2" thick? Both bows are pulling 40@28.
So.... narrower and thicker = less set, and wider and thinner = more set.... I don't know what you've been smokin,... but I guess I've been smoking it too for suggesting 2 1/2" wide fades on a 40# 63" osage bow... so I say were even. ;)
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i think his point is is that if you make it TOO thin you wind up with not enough wood taking compression where as a bow that has more wood in thickness would be able to take the compression better. theres a balance i think and if its say 1/4 inch or even 3/16in then its got too little wood, idk if im right or wrong but thats my thoughts.
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sleek, check out this post of mine with a couple osage bows I made last year. Might give you a good idea of the dimensions you need, especially comparing what you want to the wider bow that I made since it's about the same length and just ten pounds heavier. Your bow will be lighter but you'll also need that width since you're losing some working limb and stressing it a little more due to the recurves.
ttp://www.primitivearcher.com/smf/index.php/topic,27644.msg368851.html#msg368851
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http://www.primitivearcher.com/smf/index.php/topic,27644.msg368851.html#msg368851
Fixed your link for ya.
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Please explain why a 63" 40# osage bow pyramid bow with 2" at the fades and 1/2" at the tips would in anyway have more set than the same exact bow, but with 1 1/2" fades. This is what your saying. How does that make any sense in any way. :o
Let me take a stab at it. The issue is that it's WAY easier to mess up a thin bow. There's a point where it really is not worth trying and for me and osage it's around 2". Other than that, the physics is the same. Your 2" wide bow might be around 5/16ths inch thick or less. Your 1.5" bow will be around a half inch thick. Since removing thickness reduces weight very quickly, the thin limbed bow will be much more likely to take set because each session of wood removal will be a greater percentage of thickness. Consequently each scrape will have more effect and it's easier to remove too much. For this same reason tillering kids bows is hard. If the wood was consistent, there was a formula and we could precision mill the wood ... the thin bow would be no different than the thicker bow.
My personal opinion is that osage bows over an inch and a half wide feel sluggish to me. I've never made a pyramid osage bow though.
Hope that makes sense.
George
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hmmmm... i might have to think on that one awhile but it does make sense
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Well, I've been wrong before. ;D But, it is what I believe in this case.
George
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While cutting the front profile out on the band saw, i found a hidden rotten knot in the heart wood. It is such a location at the fade that chasing a ring under the sap would put the rotten knot into the back of the bow. But If I leave it sapwood backed then the knot may mostly come out if not all together during tillering. So the sapwood will stay on this bow.
I took all the advice on here into consideration and made the profile thus... 1.5 out the fades for the first 8 inches then tapers down to the last 6 inches where it is at 3/4 inch where it then tapers down to 3/8 at the tips. Ryoon, it looks allot like your first bow in that link you sent. Thanks all for the help, I hope to get a good tiller out of this one and some decent performance.
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i think his point is is that if you make it TOO thin you wind up with not enough wood taking compression where as a bow that has more wood in thickness would be able to take the compression better. theres a balance i think and if its say 1/4 inch or even 3/16in then its got too little wood, idk if im right or wrong but thats my thoughts.
Winner-winner chicken dinner. Congrats ionicmuffun. Thanks for reading my post.
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i think his point is is that if you make it TOO thin you wind up with not enough wood taking compression where as a bow that has more wood in thickness would be able to take the compression better. theres a balance i think and if its say 1/4 inch or even 3/16in then its got too little wood, idk if im right or wrong but thats my thoughts.
I understand what he is saying, I just don't agreed with it. I have made bows under 1/4" thick before. You know those 1/4" red oak pieces that are 4' long and 4" wide? I play with those all the time. This bow is less than 1/4" thick, with a 7" brace height and a 30" draw:
(http://i1203.photobucket.com/albums/bb392/toomany7/hunnic%20bow/hunnic1.jpg)
(http://i1203.photobucket.com/albums/bb392/toomany7/hunnic%20bow/hunnicb.jpg)
(http://i1203.photobucket.com/albums/bb392/toomany7/hunnic%20bow/hunnicj.jpg)
It may have about 1 1/2" set, but considering that it has less than 30" working limb for a 30" draw, I would not say that is that bad. The bow has one thin layer of sinew with tb3, which did not add any reflex to the bow at all. Previously, when I had tried the same exact design, but a little narrower, and a little thicker, all I ended up with was chrysals, set, and wasted sinew galore. This bow was like 4" wide at the fades, and 1 1/2" where the levers attached. So there is an example right there proving you wrong. I have made better examples without sinew but I don't have pictures nor do I have the bows anymore.
I really didn't intend to get into an in depth discussion, my specific point is that adding 1/2" to the fades of a 1 1/2" wide osage bow would never in a million years cause set. That is just crazy talk to me. Osage is great in compression and all adding 1/2" to the fades would do is distribute the compression a bit more in the limb section right off the fades. Which obviously, osage doesn't even need it, so this argument is just pointless. Either way, I've said my peace, I'm done. I'm sorry for going off topic in your thread sleek, I look forward to seeing that beautiful fulldraw.
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No worries. I don't mind intense descusions on my postings. Its relevant anyway. my thought on it is/was that its an issue of psi. If the pressure stays the same and you increase the inches, then you have decreased the amount of pressure per inch resulting in less stress. And I thought less stress ment less set. But I am watching all this with an opened mind. Not affraid to learn something today :)
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Its the 8:1 (approx) strength ratio that interrupts that thought sleek. Thats what all this stemmed from. There are good reasons you hear guys on here (who know) say they had to leave the thickness alone and start tillering the sides. Its not for a change of pace, its because the bow is getting thin and they need to maintain that thickness, so they head to the sides to finish tillering the bow. Im not telling you how to build your bow. I simply stated my opinion and why I thought so. I should have known better than to not hire a lawyer.
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The thickness of a bow determines how far the bow will bend. Each thickness has a tolerable bend radius that it can take without taking set. A limb that is 1/2" thick will have a larger bend radius than a limb that is 1/4" thick. If they are bent the same way then the 1/4" thick piece will be under less stress and take less set. The reason we don't make our bows super wide so they don't take set is because the extra width uses more mass for the same amount of force. This is where the 8:1 strength ratio comes into play and why the mass principle makes optimal bows. If we are able to tiller the bow so that it's thickness is enough so that it doesn't take set or takes very little, then we can reduce the width and have a bow which is has the optimal mass to do the work asked of it. I see no reason why a bow would "need" thickness.
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I think its a good discussion as I have never considered Pearl Drums premise. Whether the wide vs. thin vs. set thing applies here doesn't matter to me if I learn something that may be important in the future.
Personally I want my fades to move a little, in the same way I want a D-bow handle to move, SOME. I'm always worried about set in the handle of a D-bow but I can't just make it wider because it HAS to move, SOME. So I need to be a better bowyer, not an engineer.
With a short, stiff handled bow I want my fades moving, SOME, so if I made them wider I have to make them thinner. And as has been stated, thinning is a sensative procedure--a few extra strokes of the scraper and I've made a weaker bow--set.
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Now this is a conversation worth having. Ryoon and PD, this has really got me thinking. I never understood the side tillering thing and thought it was for laminates. Because this is a very good topic I am going to open a new one for it. When belly and side tillering is needed.