Primitive Archer
Main Discussion Area => Bows => Topic started by: Tommy D on May 26, 2020, 07:58:42 am
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Is there any advantage to gluing up multilams in stages - ie. On a trilam for example glue in an inch of reflex, let the glue cure and then blue in another inch of reflex for a total of say 2 inches. I remember reading something about this in one of the TBB’s?
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You might find an advantage if you glued the core and belly lam in 2-3 inches of Deflex, then glued this to the backing laminate in 1-2” reflex. The bow will probably spring back to almost zero deflex after adding the backing layer, but this can help offset some amount of the compression stresses on the bow belly.
Alan
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Super Perry!!
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You might find an advantage if you glued the core and belly lam in 2-3 inches of Deflex, then glued this to the backing laminate in 1-2” reflex. The bow will probably spring back to almost zero deflex after adding the backing layer, but this can help offset some amount of the compression stresses on the bow belly.
Alan
Yes that is the way to do it. :)
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Thanks - will give that a go. Is it a figment if my imagination that somewhere I read (I think TBB) that “Perry Reflex” (don’t all jump on me for using the term!) worked best if each subsequent lam Reflexed the previous lay up. Some sort of multiplier effect.
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I think there is a reference in TBBI, maybe in the "Performance..." chapter about different degrees of deflex/reflex added to different pairs of lams in a glue up.
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That was mostly speculative.
Chris Boyton used to make a bow with a double hickory backing strip glued up in a complete circle and then glued that to two other layers in a a straighter form.
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I remember reading something about this in one of the TBB’s?
I think there is a reference in TBBI, maybe in the "Performance..." chapter
The section on Perry Reflex is in TBB V.3 under the "Bows of the World' chapter, page 91.
Mark
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My mistake. The paragraph I was referring to is the paragraph above the section about Perry reflex on page 91.
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That was mostly speculative.
Chris Boyton used to make a bow with a double hickory backing strip glued up in a complete circle and then glued that to two other layers in a a straighter form.
When you say “speculative” - do you mean that what they were describing in that section of TBB was more theoretical than known fact? I am assuming it had some benefit to Chris Boyton what he was doing or is it really not worth it?
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Perry reflex is generally recognized as an improvement. There is speculation about how/why it works.
One could possibly build two identical bows, one with perry reflex, and one without, to prove it works. But I am not sure how that would be done.
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Can’t believe I haven’t heard of gluing up lams separately to change the forces they exert on each other. :o
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Can’t believe I haven’t heard of gluing up lams separately to change the forces they exert on each other. :o
Can’t tell if that’s sarcasm or not!
Unfortunately I don’t have my copy of TBB with me - but I remember some theory that gluing you lams took the stresses away from the wood and more to the glue line?
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That was mostly speculative.
Chris Boyton used to make a bow with a double hickory backing strip glued up in a complete circle and then glued that to two other layers in a a straighter form.
Been thinking about this ... this seems to be the right way to go if I have a tapered core, a bamboo back and an Ipe belly ... was thinking of gluing the core and bamboo together in reflex and then pulling some of this into a more R/D shape the second round of gluing with a belly lam?
Thoughts?
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I recall Dan Perry commenting in a thread a long time back, that he may have seen the most advantage to having a belly of 2/3 thickness prestressed and glued to the thinner backing. If I understand what is happening correctly, then I would be more inclined to try Alans suggestion.
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Do what Alan suggests.
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Trying to get my head around this...
So one method is starting with reflex and some of it out; the other way is glueing in Deflex and pulling some of that back into reflex.
Let’s say you end up with the same profile ... will there a difference in performance?
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I'm slowly getting the opinion that "pull out" only applies to shape that has been heated in. If you glue in a shape and through tillering and exercise you lose some of that shape I think that's set. If that's the case then the bow that took the most set will probably have the worst performance due to damaged wood.
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Its not about which way you flex the first glue-up, its about how thick the belly/core glue up is when you apply the backing.
Imagine a 10 lam bow. each lam glued in succession. you could make adjustments to side profile with each glue-up and create a very intricate shape to start tillering with, but since a thin lam is not strained much when bent, you would have created very little prestress to help the belly at full draw.
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Hmmmmm .... yes getting my head around this. Just worried that if I glue the core and belly first into some sort of deflex prestress, I wont be able to pull much reflex into it with the thinner bamboo. I suppose I could glue it up, floor tiller it a bit and then glue on the backing.
Might be over thinking this all!
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I've glued up well over 1/2" Yew with 1/8" boo and bent it on a caul after gluing(while the glue is wet) and it holds the bend well. If I put in 4" of reflex it will hold 3" of it. Basically if you can bend it, the Boo will hold it. With thicker bellies the danger is in the belly breaking while you are trying to bend the reflex in it.
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Might be over thinking this all!
not at all
I could glue it up, floor tiller it a bit and then glue on the backing.
the less belly wood you have to remove in the end, the more effective I think.
If your core and belly are full width when you do the first glue-up, It should be easier to get the deflex bend in the center of the bow. you might need a different jig setup for the first glue-up.
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I've glued up well over 1/2" Yew with 1/8" boo and bent it on a caul after gluing(while the glue is wet) and it holds the bend well. If I put in 4" of reflex it will hold 3" of it. Basically if you can bend it, the Boo will hold it. With thicker bellies the danger is in the belly breaking while you are trying to bend the reflex in it.
This Ipe stuff does not like to bend!!
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This Ipe stuff does not like to bend!!
yes, but if the ipe and the core are 2 different lams they will fit the deflex form easier. using ipe in a perry design well might even require being a trilam.
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This Ipe stuff does not like to bend!!
Does steaming improve this any, or is it unbendable regardless? How thick is the piece you are trying to bend?
Mark
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The consensus on the forum seems that heat and steam do very little to bend Ipe. Kerfing is the only way to go. And even the I have got some pieces less than 2mm thick that do not want to bend severely. Think spring steel. It’s interesting stuff. If I do the thin core and bamboo glue up first I can get some decent shapes as they are thinner. The belly lam is thicker and untapered so will only really do long mild bends. If I glue that to a core then I doubt I will pull much reflex out of it. I have even tried to do a sharp static recurve shape with a piece almost paper thin and it won’t follow the form!!
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Here's a couple of pics. The first is as it's clamped up for the glue to cure. The second is just released from the clamps. You can see how much it's straightened out. I don't think it held as much as I wanted to I will probably have to make a new caul for the next one. This is just a boo backed yew.
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You sure do keep yourself busy!
I cut out a caul today - but only the thinnest of thin Ipe will follow the curve... thinking I am gonna have to learn to splice in tips if I want a profile like that...
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Ok ... not sure if this is right or not ... but it’s gonna be a sorta build- along... with free advice gratefully accepted!
So going with the Alan and Bownarra advice and have glued in 4.5 inches of deflex here with a tapered core and a straight belly lam.
I have not glued the last 14 inches at the tip ends. I figured if you have to kerf Ipe anyways to get a bend/ more severe recurve I would just leave these bits unglued for now.
When it comes out of the hot box I will see how much deflex I can pull out and Reflex/ recurve I can put into the tips.
(https://i.imgur.com/P9sI6lG.jpg)
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I have found that using a caul like that(with a board and a post) seems to concentrate the bend around the post(s). If you use two posts and a clamp in the middle it's the same,in reverse. In order to get a nice even curve you have to cut a curve in a 2x6 or 8 and then clamp it to that. It's too late now but for next time. :D
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I have found that using a caul like that(with a board and a post) seems to concentrate the bend around the post(s).
It certainly does that.
In order to get a nice even curve you have to cut a curve in a 2x6 or 8 and then clamp it to that.
You can also use multiple posts to approximate a smooth curve and get quite close while maintaining a very flexible, adjustable caul set up.
Mark
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Ok back on this project... been reading on another forum (though the link came from here) on Dan Perry’s differentiation of “Perry Reflex” vs glued in Reflex.
http://leatherwall.bowsite.com/tf/lw/thread2.cfm?forum=23&threadid=188683&category=
It seems that the thicker the piece of belly wood you are pulling into reflex the more effect it will have - so long as it all holds together. It’s all about the difference in tension and compression that occurs the further apart these forces are based on the wood thickness... or as best I understood it.
He describes a neat way to get ones head around this with foam pieces...
I am slowly getting my head around this one over gluing up lots of multilams... And how it differs ...
Now ... if I glue two lams into deflex until cured and then pull this one Laminated piece into reflex as per the “Perry Reflex” would this be considered the same principle as a two lam Perry reflex only with 3 lams or would it be better, or would this simply be like a multilam glue up...
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It seems that the thicker the piece of belly wood you are pulling into reflex the more effect it will have.....if I glue two lams into deflex until cured and then pull this one Laminated piece into reflex as per the “Perry Reflex” would this be considered the same principle as a two lam Perry reflex only with 3 lams
this is how I understand it to work from reading Dan's posts, and the recommendations of avcase. ;)
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If I can stick a question in here. Does glued up reflex allow you to get more draw weight from less wood or does it actually improve the springyness of the bow? Or is there such a thing as springyness?
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Dan's theory seems to be the opposite of what everyone else thinks. Not sure his foam evidence holds up with wood.
Of course springiness exists. Compare a bunch of materials.
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If I can stick a question in here. Does glued up reflex allow you to get more draw weight from less wood or does it actually improve the springyness of the bow? Or is there such a thing as springyness?
This is quite the topic, with a lot of different views/theories/understandings of the concept. I don't know if you can get more draw weight but since it supposedly lowers stresses on the belly wood that seems to indicate it is possible. The springyness is usually more a material property than a geometry one, but I'm open to someone convincing me different in this case.
Dan's theory seems to be the opposite of what everyone else thinks. Not sure his foam evidence holds up with wood.
What is his foam evidence? Can you point me to an explanation of that? I don't recall foam being mentioned in the TBB article.
Mark
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What is his foam evidence? Can you point me to an explanation of that? I don't recall foam being mentioned in the TBB article.
Mark
Mark if you read through this post he explains his foam theory http://leatherwall.bowsite.com/tf/lw/thread2.cfm?forum=23&threadid=188683&category=
What he is saying - as I understand it - is that when you bend a thicker piece of foam the outside stretches more and the inside compresses more than a thinner piece - think I Beams here. By gluing this in, you are harnessing this potential energy. This is compared to say a multilam glue up where each thin strip - because it bends much easier - cannot harness or hold that energy. You are able to bend them into whatever shape you like, but they are not being stressed as much in doing so and are therefore not storing so much energy.
One advantage he states - which I can understand in I Beam lingo - is you can get a narrower stronger and therefore lighter limb ...
I haven’t fully wrapped my head around this ... but that’s my take so far...
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Mark if you read through this post he explains his foam theory http://leatherwall.bowsite.com/tf/lw/thread2.cfm?forum=23&threadid=188683&category=
Thanks for that, Tommy. I will go have a read.
EDIT - I have had a read through it. What Dan is talking about with his 'surface travel' concept is really strain as it is defined in mechanics of materials theory in engineering. His explanation is consistent with how Tim Baker describes Perry reflex in TBB V.3.
PatM, Dan's foam explanation holds up for all solid materials, including wood. It is basic mechanics of materials stuff combined with a bit of beam theory. Foam is used as the material because it will tolerate large enough strains for them to be seen by the naked eye, but all solid materials adhere to the same rules.
One thing I am wondering about is Dan describes using very thick pieces of wood for the belly lam, upwards of 3/4" thick for his bows. He also mentions that he likes to be close to finished dimensions when he does the glue up. I can't imagine having a finished bow be over 3/4" thick anywhere on the limb. What wood species and type of bow would that apply to? My last pyramid bow is made from hard maple, draws 40lb@28", the limbs are 2" wide at the fades and the finished thickness is around 0.385" at the fades. Doubling that thickness would make it 8 times stiffer for a draw weight of 320lb@28" (not that the maple would survive that). That seems crazy to me. Even if you halve the width to 1" that leaves you with a 160lb bow.
One thing that Dan seems to not understand is the idea of gluing two thinner lams into a deflex shape, then pulling that assembly into reflex during a second glue up with the backing lam. He says that wouldn't be the same as pulling a single piece belly lam into reflex as he does, when it actually would accomplish exactly the same thing. He seems to think that having a glue line in the first assembly somehow renders the response of the glued up pieces to be different than bending a single piece of wood. As long as the glue is as strong as the wood is (which is typically the case for the glues we use) then there is no difference in the end.
Mark
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I got the impression when I read it was that the 3/4" was just for the glue up and then he tillered it down to whatever thickness. I've noticed that when I used a thicker belly I get more reflex gain as I tiller. I'm not sure if that's what he was after or not. Something you may answer is about the reflex gain. Basically I think that all that is happening is that when you glue them together, reflex them, and then release them the forces balance out. As you tiller, the belly gets thinner and weaker and the back starts to win the tug of war. Presto, reflex gain. What I'm wondering is would the results be the same to if you used a thinner belly and just reflexed it more at glue up. Hope you can follow that.
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I got the impression when I read it was that the 3/4" was just for the glue up and then he tillered it down to whatever thickness.
Hmm. If that is what he is doing then he is gaining nothing over just gluing up with the finished thickness in the first place. Strain is proportional to the distance from the neutral axis, so if you bend a 3/4" thick piece and then tiller it down to 1/2" thickness that surface will see the same strain as if you just bent a 1/2" thick piece to the same radius to start with.
The only possible gain with Dan's method is the neutral axis shift as the belly lam is removed during tillering. I can't say if that affects anything or not without looking at it in more detail, but it is possible it could affect the final result. My gut feel is that it makes no difference.
Basically I think that all that is happening is that when you glue them together, reflex them, and then release them the forces balance out. As you tiller, the belly gets thinner and weaker and the back starts to win the tug of war. Presto, reflex gain.
That is correct.
What I'm wondering is would the results be the same to if you used a thinner belly and just reflexed it more at glue up. Hope you can follow that.
Should be the same in the end, based on the engineering principles I mentioned. The strain a material sees is only dependent on the deflection it sees, not how that deflection is achieved.
Since we are talking about gluing in reflex, how much spring back do you typically see with your boo/yew bows (or whatever you are using these days)?
Mark
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If you are talking about springback when I take it off the caul after the epoxy has cured it depends on the thickness of the belly again.
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If you are talking about springback when I take it off the caul after the epoxy has cured it depends on the thickness of the belly again.
What kind of range do you see? I'm just trying to get a feel for how much to plan for in future cauls.
Mark
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About an inch
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one thing that might come into play when making comparisons, is the stiffness of the backing relative to the stiffness of the core.
It is not specifically stated in this thread, but I think Tommy D has been using boo over ipe, while Don is relating to his experience with boo over yew.
I could well imagine that a bamboo backing, glued in perry reflex, would cause a boo/yew bow to go into more reflex as it is tillered, than a comparable boo/ipe bow.
Since Don's basic question is how he might utilize perry reflex better in his application. Might there be ways to evaluate relative stiffness's when considering how much reflex to glue in? (or in the case of a pre-glued deflexed core, how much deflex to glue in to the core?
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I guess we stole Tommy's thread. Sorry Tommy. Thinking about this I was wondering about Ipe. Since it's so hard to bend would it even lend itself to glued in reflex. Especially if you tried gluing deflex in two belly lams and then tried to reflex that piece. Would it even go. I should try some Ipe so I can at least have some knowledge about it.
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One thing that Dan seems to not understand is the idea of gluing two thinner lams into a deflex shape, then pulling that assembly into reflex during a second glue up with the backing lam. He says that wouldn't be the same as pulling a single piece belly lam into reflex as he does, when it actually would accomplish exactly the same thing.
I did some more looking at this and I want to be more accurate with what I said. While it is correct to say that gluing in deflex, then reflexing that assembly into a new glue up induces the same strains as reflexing a solid piece of wood by the same amount, that is not completely accurate because the final strains in the glued up belly lams are not the same as the strains in the solid belly piece.
What happens in the deflex glue up is the belly surface sees a small amount of compression due to bending the deflex into the thinner lams. This compression strain counteracts the tension strain induced by bending in reflex in the second glue up. The net result is that the belly ends up with the tension from the reflex glue up less the compression from the deflex glue up. Because the reflex glue up is done with a thicker belly lam than the deflex glue up you can still get significant tension into the belly surface but not as much as if you reflex a single piece belly.
Offsetting this effect is that you can pull more total reflex into the second glue up when starting with the deflexed belly lam assembly, for any given final side profile.
I guess we stole Tommy's thread. Sorry Tommy.
It seems we did. If OP wants, we can take this to a new thread and leave his thread to his questions specifically.
Mark
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Keep going ... I am learning all sorts of interesting things ... it why I started the thread...
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I guess we stole Tommy's thread. Sorry Tommy. Thinking about this I was wondering about Ipe. Since it's so hard to bend would it even lend itself to glued in reflex. Especially if you tried gluing deflex in two belly lams and then tried to reflex that piece. Would it even go. I should try some Ipe so I can at least have some knowledge about it.
So I have gone a new direction slightly ... I decided to recurve the tips first. Then pull in deflex with a core lam. Then pull reflex in with the bamboo back. I cut a kerf into my belly lam on the tips and glued in some recurved tips. I put one “wedge” in the left. I did this on a caul I have made.. I cannot get these as sharp as I would like. I have used yew and Osage before - Ipe is different. To me it feels a little like if you were comparing steels - you have steel that has springiness but will still bend once you go beyond it’s “springiness” before breaking - and then you have steels that are springy but when they reach their limit they just break. Ipe is like the later. That’s the closest comparison I can give.
Now I have pulled in some deflex and glued in my tapered core lam. It’s also “Ipe” but I think it’s a poorer quality Ipe. I know that Ipe is actually a fairly generic term. The piece I am using for cores has made a few bows but I would rather use it up as cores than the nicer dark stuff Ipe I have.
So this it’s what I have now...
(https://i.imgur.com/tyTyI4H.jpg)
When it’s cured I will adjust the caul and pull in some reflex with the bamboo...
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Very ambitious design you have going Tommy. Will be watching with interest.
Keep going ... I am learning all sorts of interesting things ... it why I started the thread...
Perry reflex threads always seem to generate discussion, maybe because it is a concept that all of us are trying to understand better. Sometimes I think it can be simply described as a way to make the back work harder, similar to trapping.
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I like it because that initial reflex gain hides some of the set that I know is going to come later :-[ :-[ :( :(
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I like it because that initial reflex gain hides some of the set that I know is going to come later :-[ :-[ :( :(
You mean like if a tree falls in a forest and there is no one there to hear it did it really make a noise?! 😂😂
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Sometimes I think it can be simply described as a way to make the back work harder, similar to trapping.
Plus getting some work out of the material near the neutral axis that normally contributes very little to the performance of the bow. Perry reflex mostly transfers some of the initial belly strain into the core material that normally doesn't work very hard, making it almost like getting something for nothing.
I like it because that initial reflex gain hides some of the set that I know is going to come later :-[ :-[ :( :(
;D ;D
I wish I didn't understand what you mean by that.
Mark
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Plus getting some work out of the material near the neutral axis that normally contributes very little to the performance of the bow. Perry reflex mostly transfers some of the initial belly strain into the core material that normally doesn't work very hard, making it almost like getting something for nothing.
Mark, that's the part that went over my head. I remember perhaps an earlier thread or somewhere in TBB, a similar explanation akin to "the energy is stored in/at? the glueline."
Is there any way to quantify or even make just a ball park estimate of how much energy can be redistrubuted to midsections that would otherwise have normally expected strains?
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Mark, that's the part that went over my head. I remember perhaps an earlier thread or somewhere in TBB, a similar explanation akin to "the energy is stored in/at? the glueline."
Is there any way to quantify or even make just a ball park estimate of how much energy can be redistrubuted to midsections that would otherwise have normally expected strains?
Tim Baker describes it that way in TBB V3.
It should be possible to calculate the strains for each step of the construction process at each surface of the belly and back lams to see what is going on. I have no feel for how much energy can be stored there, I suspect it will depend on the shear strength of the glue and possibly the wood itself. The other limit will be the back in tension. It doesn't get the same reduction in stresses that the belly does (unless the back is the same thickness as the belly lam and that is not how it is normally done) and will eventually end up being the failure point as reflex is increased, similar to what happens if you trap a limb too much.
I would think that 10-20% of the total energy is not a crazy estimate for what the inner wood can contribute.
I need to do some experimenting with scrap wood, gluing up lams and seeing what happens with the reflexing and how it all reacts to being pulled and pushed then glued into position before I glue up a bow for real. There's no point in wasting good wood yet until I have a better handle on how it all works.
Mark
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Tim Baker describes it that way in TBB V3.
It doesn't get the same reduction in stresses that the belly does (unless the back is the same thickness as the belly lam and that is not how it is normally done) and will eventually end up being the failure point as reflex is increased, similar to what happens if you trap a limb too .
Remind me why we wouldn’t use a back the same thickness as the belly lam in this sort of glue up?
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Remind me why we wouldn’t use a back the same thickness as the belly lam in this sort of glue up?
It is because most woods are several times stronger in tension than compression. Similar to trapping, Perry reflex adds stress to the back in order to reduce the stresses on the belly (along with getting some work out of the core wood).
For same wood bows (all lams the same material) Dan Perry recommends the belly lam be 2/3 of the stack and the back 1/3. For combinations with a much stronger back than belly he recommends the belly lam be 3/4 or more of the stack depending on the wood combination.
Mark
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(https://i.imgur.com/HC1mCge.jpg)
Right ... enough theory ... where do I start with this thing!!
Have I created a monster!!!!
Not quite sure where to begin! The bow is 70 inches around the curve so I could take some of the tips off and shorten it if I struggle to get a string on ... it will definitely be a recurve if I leave them as is but my tips are fairly narrow - though they are lined up!!
Was thinking of starting to tiller from the outer limbs first on a long string and see if I can brace her but I think the strings will pop off...
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String alignment will be key on that one Tommy.
I've had lots of problems getting the weight on my RD's. Go slow, meaning 4-5 scrapes tops and then exercise to full draw weight and look it over. Out around 18-20" mine have a tendency to relax or something. Not sure how to describe it but you will all of a sudden get the the bow going from 20" out to 24"(approx) without any scraping. In my case I think it's set but just be aware that it may happen.
Use your eyes a lot. Look for areas in the belly that are getting thin. Compare side to side looking for the same thing.
Make a tracing of it on something and check for set regularly. It's easy to do when you're on the long string but a PITA once it's braced because you have to unbrace it every time but do it. A quick check for set is to measure the reflex. If the reflex is dropping you're getting set.
For the first little while when tillering you may gain some reflex. Keep track of that so you can watch for set.
Did I say go slow ;) By that I don't mean take lots of coffee breaks. Look it over very critically. Watch for those thin spots. These things will hinge in an instant.
Good luck
PS it looks very cool ;)
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Right ... enough theory ... where do I start with this thing!!
Have I created a monster!!!!
That thing almost looks like a Duo-Flex profile if the recurves work a decent amount. Good luck with the tillering.
Out around 18-20" mine have a tendency to relax or something. Not sure how to describe it but you will all of a sudden get the the bow going from 20" out to 24"(approx) without any scraping. In my case I think it's set but just be aware that it may happen.
Where does the set tend to occur?
Mark
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Just inside mid limb for me. It has crossed my mind that when I have the bow in the vice for scraping that the mid limb is the highest part because of the reflex. I've wondered if I'm scraping harder mid limb because of that. I try to keep that in mind but my mind ain't what it used to be. ;D
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Here is a question for those who have built a number of Perry reflex bows. Have you done an FDC and what does early draw look like with the bending force coming from the internal stresses in the limb rather than the belly and back surfaces?
Mark
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(https://media0.giphy.com/media/VGDuYkRCBcGGV6qQxA/giphy.gif?cid=4d1e4f291809877c585a8d2b54b2b7aba504b48794ad7c99&rid=giphy.gif)
Broke my tillering tree! But I thought I would try my GIFF skills to elicit some tillering advise for anyone with suggestions as to where to start removing wood - whilst I fix the tillering tree!
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I'm pretty sure that early draw weight comes from more than just internal stresses. String shortening due to recurves for one. Limb shape possibly for another. Telling one from the other could be difficult.
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(https://media0.giphy.com/media/VGDuYkRCBcGGV6qQxA/giphy.gif?cid=4d1e4f291809877c585a8d2b54b2b7aba504b48794ad7c99&rid=giphy.gif)
Broke my tillering tree! But I thought I would try my GIFF skills to elicit some tillering advise for anyone with suggestions as to where to start removing wood - whilst I fix the tillering tree!
I'm not sure. The left limb may be bending more. Can you pull it with just one hand on the handle?
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I'm pretty sure that early draw weight comes from more than just internal stresses. String shortening due to recurves for one. Limb shape possibly for another. Telling one from the other could be difficult.
In a Perry reflex bow much of the early weight will come from the internal stresses and some back tension as the belly surface doesn't see actual compression forces until it is drawn back past whatever position it was reflexed from into the glue up. For instance, if I deflex the belly lams and glue them up with 6" of deflex, then pull that assembly into 3" of reflex when I glue the back on (assume these are final numbers after spring back has occurred), the belly surface won't see any compression until the bow is braced past 6". If you braced it right at 6" the surface of the belly lams would have zero stress, either compression or tension and would be contributing nothing to the string tension. All the force the string is seeing would be coming from the internal stresses in the limb and tension stress on the back.
Tommy, I agree with DC, it looks like the left limb is bending a bit more. The bend doesn't look bad to my eye, maybe the inner limbs are bending a touch too much and you might want to get the mid limbs bending just a bit more. The recurves look like they are uncoiling pretty well.
Mark
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Ok I will fix the tillering tree and resume work in the morning! Thanks for all the help.
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(https://media0.giphy.com/media/H3NkBI7ZX85QSFeR6O/giphy.gif?cid=4d1e4f29407d6fd1b5081c644c99a1f4d01ab2dc16e76414&rid=giphy.gif)
Cleaned things up a little. Pulling 60lbs which is my target. I can see the left limb still a bit stiff. Can’t decide if optical illusion or slight hinge developing on the right straight out of the fade?
The transition on the recurves already quite thin - won’t touch those for now I don’t think.
Should I leave everything on the tip side of the recurve for now?
String still seems aligned... but I’ve never tillered this much recurve so any suggestions welcome.
At what point does one consider a short string? When would one file string grooves?
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the gif is cool, I can "explode" it into the components. looking at giphy.gif.048 It does seem like the fade area over your left knee is bending more, and not sure if the other limb is too stiff, it looks as good as the rest, (except as noted above your knee)
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I think I would try bracing it. Is you hand on the handle? It looks a little to the(my) left to me. I also see a bit too much bend by your knee. I'd leave that area for now.
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I wasn’t quite sure what you meant about the left limb? Yes my hand is on the handle. But I haven’t glued the handle on yet. That part is thicker because of a power lam and also I left my belly and core lams thicker. Will try brace it tomorrow
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(https://i.imgur.com/TLYeHOs.jpg)
Ok so I’ve filed some string grooves ...
and strung it!
(https://media2.giphy.com/media/LmxdV2Xq9MwBiznpgk/giphy.gif?cid=4d1e4f29627f0cd92fd68bc9f2043e22836fece2aa9e1025&rid=giphy.gif)
But the string pops off when I pull it...
I have to say these recurves are making me a bit nervous... anyone have a string pop off in the shot? What happens? What’s it like if it does? I am beginning to think I am a straight limb guy!!!
Close up of the grooves and alignment ...
(https://i.imgur.com/64qBk0s.jpg)
Here is a short GIF of why the string wants to pop off. Seems one limb tip has a weak side. I can see that I thinned this side more then the other side at the deflex/reflex transition.
Not sure where to try and correct this ... I know the tip bends to the weak side ... so supposed to take material off the strong side... just not sure where? And whether to work on balancing the other limb first...
(https://media2.giphy.com/media/WPu6aRKdqCKlMJI8XC/giphy.gif?cid=4d1e4f29caa6d25440d9e16e4e36d04fbe32b77b7465a955&rid=giphy.gif)
(http://)
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I find it is better to manually torque the twist the opposite way rather than trying to thin one edge. Clamp in a vice at the handle to do this.
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Hi Pat that twist develops in the draw... at brace height everything seems lined up. Is it still worth torquing in this situation?
I guess I could try and deepen the string groove on the weak side...
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Yes, you need to torque it as you bend it. The wood needs to be "trained".
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Yes, you need to torque it as you bend it. The wood needs to be "trained".
Sounds like my dog! Ok will give it a go!
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Deepened the string groove on the weak side and did some “limb training” ... alignment seems to be holding better now... it’s pulling 55# at about 20inches.
I think the bottom limb a little stiff... and the top limb bends more close to the handle... will look again tomorrow ...
(https://media3.giphy.com/media/Lq5fJtaPEGueVMbPaK/giphy.gif?cid=4d1e4f29483ff5f2f83c6beda903ba13da509eaac8248633&rid=giphy.gif)
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Yup I agree, bottom is stiff. I like these gifs. I've got a bow looks very much like that, in the corner of shame. It keeps twisting off too
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I like these gifs. I've got a bow looks very much like that, in the corner of shame. It keeps twisting off too
Do you ever shoot it?
If all else fails I can always cut the tips off and glue in shot short static recurves I think!
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Never got it to half draw. One tip starts to go sideways. You're doing better that me. It's maple backed Yew. Just under an inch wide at the widest.
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Just under an inch wide at the widest.
Wow that’s narrow. I can see how it would keep flipping. I have it so I can put a few arrows through at a short draw.
Fair bit of hand shock!
Wondering if I can sort of hollow out the recurves - sort of widen the string grooves. Thinking this might be a good way to loose some mass but not affect their stability... It’s just a thought at this stage.
Still need to balance this tiller. It’s taken about an inch of set so far...
(https://media2.giphy.com/media/Q8Tld6ZVho61NVodjK/giphy.gif?cid=4d1e4f2979f8495ee59276a68a968c8aeb25b11a27bc2747&rid=giphy.gif)
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Well done!
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Tempted to take an inch or two off the tips - trying to figure out how to lose some of the hand shock. I can keep thinning the limbs but worried about stability. It’s a learning curve for sure - but starting to like the good old R/D more and more!!
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(https://i.imgur.com/3eaimdE.jpg)
(https://i.imgur.com/A6GbFt3.jpg)
Back on this bow. It’s a trilam. Bent some deflex in and then pulled in the reflex. The outer tips were kerfed to get the Ipe to bend. I am not sure what style one would call it! It’s a bit long I think at 66” nock to nock unbraced. But the piece of wood was 71” to start so that’s all in the bend. I know the left limb still a bit stiff and I struggled initially to keep the string on the recurve but it seems fine now. Have shot it a fair bit at short draw.
Trying to decide whether I carry on or take something off the tips. Kinda where the string loops are in the unbraced picture. Sort of a zero backset.
Would this increase or decrease the speed at the same poundage? A mass vs backset thing. I know it would prob be a better bow to carry strung all day.
A part of me feels finish it as is; I’ve come this far. It’s been a lesson. But I don’t love how long and unwieldy it is?
Thoughts much appreciated
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I tend to like reflex and as long as you can still string it I would leave it. If you pike it you will gain some draw weight but you will lose some speed I think but the only time I did that I reduced the DW that I'd gained by piking so that may have been the cause of the speed loss.
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Well you sure do make some nice recurves! I am thinking now I will make it for a friend. I only draw 26/27 inches. I have a friend with a 30/31 inch draw - I think at that sort of draw length it might start making sense
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Work up to that DL step by step watching for the limbs twisting off.