Primitive Archer
Main Discussion Area => Bows => Topic started by: Philipp A on January 23, 2017, 05:25:16 pm
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Hi All,
I have a question. I have developed the habit (not sure whether it is a good or bad habit) of massaging out the developed set on the bow after I have been shooting it for several hours. I usually do this by having one tip rest on a soft surface (carpet for example) and I end up massaging the back of each half by applying gentle pressure while massaging the limb towards the tip.
The set is almost gone by the time I am done. I am not sure whether I do harm to the bow or whether it is beneficial and I am wondering whether any of you have done this before.
Cheers,
Phil
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Does the bow come back to the same amount of set after shooting? You might be visually removing the set but I doubt you are actually eliminating the set. I don't think you are hurting anything by messaging the bow but I doubt it is actually doing anything.
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Waste of time and you have a better chance of eventually breaking the bow by overdoing the straightening.
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Waste of time and you have a better chance of eventually breaking the bow by overdoing the straightening.
+1
just leave it overnight.
I took some measurements of how a bow recovered a while back. The set reduced over about 2 hours, but the next morning it had recovered even more.
Patience is one of the most valuable tools in bowmaking and one of the hardest to master :laugh:
De
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Yes it comes back to what it was before shooting, but I think it is likely true that it would come back to that overnight without me doing anything. As I said before, likely more a bad habit than anything useful on my end.
Was just wondering whether anyone else has done it.
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I doubt if it realy hurts anything but you might have a slight tendency to go past the set. Sometimes limbs get rubbery when worked back and forth like that.
Set is a complete study in itself. If a bow doesn't recover at all it tends to shoot more like a bow that didn't take any set in the first place. Not to be confused with string follow.
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thanks all for answering. To Badger: what actually happens in set? Is it fibres stretching or does it represent small tears in some of the fibres? has it ever been studied under a microscope or with non destructive testing such as ultra sound or X-rays?
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It is cells being compressed.
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Thanks PatM, would be interesting to see the shape of the compressed cells under microscope. For the amount of set that does not recover after 24 hours, I am wondering whether the cell wall collapses when compressed in some of the cells to cause the permanent set. Are there any scientific studies to this effect?
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Some years back the majority agreed that string follow and set are two different things. Set was defined by the amount of decurve relative to the profile prior to any tillering and after allowing sting follow to relax and recover.
Your massaging will take encourage the string follow to recover, but the set is...well, for lack of a better word, SET.
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Some years back the majority agreed that string follow and set are two different things. Set was defined by the amount of decurve relative to the profile prior to any tillering and after allowing sting follow to relax and recover.
Your massaging will take encourage the string follow to recover, but the set is...well, for lack of a better word, SET.
How they can't be seen as degrees of the same thing is beyond me.
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I consider set and string follow as 2 different things. Set is permanent deformation of the limbs and string follow as temporary, recovers over time.
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That would mean string follow longbows are just a temporary type of bow. ;)
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It's the other way round, isn't it??!
If you pick an unbraced bow off the rack, and it's bent towards the belly the amount it's bent away from a dead straight line is string follow, because that's how much it's following the string. The original stave shape is irrelevant, as it's just a way of describing the shape of the bow, i.e. "it HAS string follow".
Set requires the original stave shape to be known, because set is how far it's bent towards the belly from its original shape due to cell compressjon, i.e. "it's TAKEN set".
You can have a bow with 0" of string follow but 2" of set if the original stave had 2" of reflex but the bow is now dead straight.
You can have a bow with 2" of string follow and 0" of set if the original stave started with 2" of deflex.
You can have a bow with 2" of string follow and 4" of set if the original stave had 2" of reflex and the bow now bends towards the belly 2" from dead straight.
This means that set is the temporary factor, because the cell compression can ease back again after not being used. String follow is a permanent shape to a bow, whether it's just been shot or hasn't been touched for years.
Right?!
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It's really just a matter of wood not being a perfect spring material. All the rest is just semantics explaining the behavior of the material.
The cells get compressed and most of that returns rapidly, a small remainder returns slowly and some never returns. The more you stress the material, the more you skew those percentages. That's really it.
Trying to shoehorn that into fitting bow shapes doesn't alter things.
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interesting discussion for sure. I am still however curious what actually happens within the cells for the bow to take on permanent string follow / set.
In fibre glass for example if you end up over compressing the fibres you end up "buckling" the fibres which would show up as little waves on the compression side. I am familiar with this from some fibre glass components.
It appears that buckling failure in wood is similar based on the article enclosed below (see section Strength of Wood):
https://www.doitpoms.ac.uk/tlplib/wood/printall.php
I am wondering whether set/string follow is simply a partial buckling failure that is not sufficient to cause a complete compression failure of the bow. That would assume that further damage is stopped when a balance is reached between the draw length of the bow and the reduced distance the bow has to be drawn under load due to the partial compression failure (the bow is softer).
If my theory is correct this would mean that a bow with some string follow / set would have a reduced draw weight at the same draw length when compared to its original fully tillered shape before string follow has "set" in.
Let me know whether I am totally out to lunch with my thinking on this.
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Some years back the majority agreed that string follow and set are two different things. Set was defined by the amount of decurve relative to the profile prior to any tillering and after allowing sting follow to relax and recover.
Your massaging will take encourage the string follow to recover, but the set is...well, for lack of a better word, SET.
How they can't be seen as degrees of the same thing is beyond me.
My hypothesis is that the set is permanent damage to the structure of the fiber. String follow is temporary loss of elasticity that recovers in a period of time.
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You are correct it does reduce the draw weight. If you ever take the time to monitor how much draw weight you can loose it will scare you. A bow with a lot of set might have lost over 20# in the building process not from removing wood but from exercising it in an over stressed state. Exercising a bow to get wood removal to register is often doing nothing but collapsing wood cells. That is why it is a good idea to go down 1" at a time at full draw weight If you are picking up inches just by working it you have a problem.
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Set is really fascinating. The set that is important is any recovery that is slower than your arrow. You can't measure set when a bow is at full draw but you can identify it and quantify it through a series of tests. If you unstring a bow and it has 2" of set it might really have 4" when the bow is at full draw. Set recovery starts slowing down as soon as you release the string. It might take a bow 2 seconds to recover the first 1/2" 10 min for the next 1/2" and 1 hour for the last 1/2" and then maybe a little more by the next day. The recovery actually starts during the shot sequence but anything slower than the arrow you loose out on.
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Hi Badger, interesting observations. I have never thought of it in terms of set recovery during the shooting sequence. I guess based on your observation a bow that feels springy should also have less set during the draw sequence in comparison to one that feels like a noodle. I am also wondering whether hardwoods that have tight year rings are more susceptible to set than the ones with wider growth rings? Any observations on which bow woods are more susceptible to set than others?
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Well, folks are out to redefine archery terms again. I won't even bother to say which terms or which people. But you each know whether you are using a long-held definition that is in many of the old books, or are using what you have heard people use, or are just saying what you like to think the word means.
Here's another thing many of you are prognosticating on without reference or deference to the knowledge of those who came before: ALL the early writers on bows, beginning at least as early as Roger Aschem, were insistent that a bow should NEVER be bent backward and that doing so in the hope of repairing set only made the bow less strong and more likely to break.
But we DO like to think we know things and that others have no experience or knowledge that ranks with ours.
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Reply to asharrow:
The reason for myself posting the subject was because I was seeking advice on whether this is harmful to the bow or not. You clearly are indicating that it is. So taking your advice (and that of others) it will be a good idea not to continue doing it. My bows have not suffered because of this habit (yet), so I guess I have asked the question in a timely fashion. I definitely appreciate your feedback!
Having said this, I don't think there is anything wrong in asking a question, having a general discussion about set, string follow and what actually happens in the wood during that process.
Having curiosity is something that has served me well and it is the only way to further knowledge, either through the wisdom and experience of others or by experimenting yourself and seeing what goes right and what goes wrong and to educate yourself and to become better at whatever you set your mind to do.
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This discussion reminds me of something Badger wrote recently... "If we have to exercise the bow to register changes, we are actually damaging the wood. We don't want the wood to have any memory of ever being bent if possible."
He was talking about tillering, but I think it applies here as well. I do a lot of origami and it makes me think of how paper has memory. Once you crease paper, it never forgets that crease. In bow making, it's like set happens when the wood is stressed too much and as a result it gets "creased." Just like paper, wood never forgets that.
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Phil, was your bow wood dry? Jawge
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Hi Badger, interesting observations. I have never thought of it in terms of set recovery during the shooting sequence. I guess based on your observation a bow that feels springy should also have less set during the draw sequence in comparison to one that feels like a noodle. I am also wondering whether hardwoods that have tight year rings are more susceptible to set than the ones with wider growth rings? Any observations on which bow woods are more susceptible to set than others?
I could never identify a feature about wood that would take more or less set. Here is some more to confuse you. Some set isn't really even set. Sometimes the forward reflex we put in just doesn't hold and appears to have taken set. I think the best indicator is the less recovery after unstringing the better. Not stating this as a positive fact, it just appears this way to me after doing some tests.
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I think Korean bows take probably the most temporary string follow of all bows. But they are horn and sinew... a lot of sinew. They probably suffer from a lot of hysteresis - draw weight drops the more you hold at full draw? I think an overstrained wood/sinew bow would act similarly.
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I am wondering whether set/string follow is simply a partial buckling failure that is not sufficient to cause a complete compression failure of the bow.
My take on it is that all wood cells are not created equal. weaker cells yield and loose stiffness before the stronger, and a higher percentage of stronger cells makes for better wood.
wood typically being stronger in tension than compression, makes the stretching of cells on the back of the bow less critical, but different designs do maximize the benefits of the work done in tension.
I am also wondering whether hardwoods that have tight year rings are more susceptible to set than the ones with wider growth rings?
early/late wood ratio in a ring is commonly said to be more important than the ring count it's self.
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Some years back the majority agreed that string follow and set are two different things. Set was defined by the amount of decurve relative to the profile prior to any tillering and after allowing sting follow to relax and recover.
Your massaging will take encourage the string follow to recover, but the set is...well, for lack of a better word, SET.
How they can't be seen as degrees of the same thing is beyond me.
My hypothesis is that the set is permanent damage to the structure of the fiber. String follow is temporary loss of elasticity that recovers in a period of time.
That's why I said degrees of the same thing. Permanent damage is complete loss of elasticity, temporary is just that and the rest is undamaged elasticity.
Why hasn't there been a petition for string follow longbows to be called "set longbows"?
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To George: yes my wood was dry (9%). The bow actually doesn't have a lot of set (less than 1" when recovered). I just gotten into the habit of massaging the limbs after shooting....which I won't do anymore based on the feedback received :)
To upstatenybowyer: I think what you are stating based on Badger's quote rings true with me as well...
To willie: I use HHB for my bows which is a diffuse porous wood, so the early / late wood ratio should not be deciding factor. I do know however that the wood has to be absolutely dry to prevent set. I think when I do get more set it is typically when I am not patient enough when tillering and overdrawing the bow before it is ready.
To Badger: yes you did indeed confuse me more :). Your quote: "I think the best indicator is the less recovery after unstringing the better" maybe you can elaborate a bit more
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Phil, I don't think bending it backwards is a good idea either.
Regarding set and string follow...they are cousins.
This is how I see it.
String follow is when the bow appears to be strung when it is not.
Set is when the bow moves from its starting point when it was a stave.
Here's an example.
A stave starts with 3 in. of reflex. After tillering it retains 1 inch of reflex so it does not follow the string but it does have 2 in. of set.
Jawge
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Reply to asharrow:
...Having said this, I don't think there is anything wrong in asking a question, having a general discussion about set, string follow and what actually happens in the wood during that process.
Having curiosity is something that has served me well and it is the only way to further knowledge, either through the wisdom and experience of others or by experimenting yourself and seeing what goes right and what goes wrong and to educate yourself and to become better at whatever you set your mind to do.
Absolutely right.
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Jawge has it exactly right. The centuries old definitions.
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Yep Jawges definition is how I view it also. As far as bending it backwards, not usually a good idea especially if you go to far, a little I guess might not hurt but not worth the chance to me. I have seen several bow broken from folks unknowingly trying to string the backwards. :) The belly is like a badly violated back and you don't want that. ;)
Pappy
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Jawge said exactly what I said, essentially word for word. But I'm glad somebody got it right... ::)
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Pretty much, Willis, except for set being temporary. I didn't say that.
I've noticed that some of it is temporary after unstringing but most remains.
Jawge
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Good discussion. All I know is that after building maybe 30 all wooden bows I only have a few that haven't taken some set. Two were osage and the other is sinew backed. Being as careful as I can and going as slow as I can my white wood selfbows all take at least some set.
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Good discussion. All I know is that after building maybe 30 all wooden bows I only have a few that haven't taken some set. Two were osage and the other is sinew backed. Being as careful as I can and going as slow as I can my white wood selfbows all take at least some set.
All wood bows will take some set, I think the challenge for a bowyer is to do his best to keep it under as much control as he can. There are several tecniques you can use that can help you to monitor it as you go along. The most basic thing we can do it to not ask too much from a design, make sure the bow is wide enough and make sure we have enough bending limb and that the bow is long enough for the draw length. Keeping moisture under control is another big factor. Patience is another one. If someone gets impatient because scraping wood isn't dropping weight fast enough the tendency is to pull it further to make the change register. If I have 50# say at 20" I may have to check it 5 or 6 times scraping it inbetween each scrape just to get it to 21". Patience is the biggest most important tool we have.
Someone asked me to elaborate on the statement that I prefer no recovery or as little as possible. Recovery of set doesn't ahppen at the same speed. It doesn't just creep forward at say 2" per hour. It starts off fast and slows down. You might recover a full inch when you unstring it before you can even put the bow against a wal to check it, less than 1 second. The second 1" might take a full hour. If the bow doesn't recover at all chances are you are not suffering as much hysterisis durring the shot. Kind of like what you see is what you get.
Another one is when we use heat to reflex a bow. Sometimes we keep almost all of it and sometimes we might only keep 1/2 of it. It might be set and it might be that the reflex we put in just didn't hold. The difference is that belly fibers may not have ben crushed at all it mmight just be that the compression bend we put in the back of the bow pulled back out and doesn't really hurt a thing besides loosing some of the reflex we wanted.
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Thank you all very much for the responses, it is much appreciated. It has been definitely educational and I am looking forward to learning more about the mechanical properties of wood from all of you. I have also found several interesting scientific articles in this regard and hope to be able to get a better understanding of the compression failure mechanism in wood of which string follow and set seems to be a mild form of it. One of the articles I have read is called "Compression failure mechanism in small scale timber specimens".
It describes it as follows:
Under a compression load parallel to the grain, small clear-wood specimens undergo four main deformation steps: linear elastic (a), incipient kinking (b), transient kinking (c) and steady-state kinking (d). The incipient kinking is the plastic shearing and buckling of the fibres, localised close to the resin canal region where the fibres are misaligned [I am assuming this is where string follow / set happens]. The transient kinking phase is defined as the unification of all the incipient kinking areas in a unique kinkband that goes through the entire width of the specimen and starts when the peak stress is reached. This step is also characterised by a decrease in the stress, which eventually reaches a plateau when the fibres inside the kinkband can no longer rotate (lock-up angle). The process that takes place during this step is a broadening of the kinkband at a constant stress level (steady-state kinking).
The Swedish article has many illustrations and was primarily written to further the understanding of failure modes in glulam beams.
Cheers,
Phil
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thanks for posting that quote, and good luck with your search for better understanding.
in the article you cited earlier https://www.doitpoms.ac.uk/tlplib/wood/printall.php (https://www.doitpoms.ac.uk/tlplib/wood/printall.php)
The structure of wood (I)
Cell wall schematic
Further cells are aligned parallel to the cell shown. The middle layer is the thickest and most important, and the orientation of the cellulose microfibrils is significant. The orientation of the microfibrils has only been shown for this layer. The cell wall is approximately 50% cellulose fibrils. To toughen the structure, the fibrils are aligned at 10 to 30° to the tree trunk axis in the middle layer of the cell wall.
Microfibril angle might be a factor worth noting, and if you uncover pertinent info related to set, would you be kind enough to pass it along with a follow up post?
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That may explain why chrysals typically run at angles rather than straight across.
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Phil, I don't think bending it backwards is a good idea either.
Regarding set and string follow...they are cousins.
This is how I see it.
String follow is when the bow appears to be strung when it is not.
Set is when the bow moves from its starting point when it was a stave.
Here's an example.
A stave starts with 3 in. of reflex. After tillering it retains 1 inch of reflex so it does not follow the string but it does have 2 in. of set.
Jawge
Essentially what I was saying.
My definition of string follow is what Steve describes as the limbs recovering after you unstring the bow. All bows have that, some more than others
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To Willie: I found this article on the impact of MFA (microfibril angle) on compressive strength in wood and it is negatively correlated. Please see article link below:
https://www.researchgate.net/profile/Paulo_Ricardo_Gherardi_Hein/publication/262745273_Relationships_between_microfibril_angle_modulus_of_elasticity_and_compressive_strength_in_Eucalyptus_wood/links/00b7d539af9b26a7ac000000/Relationships-between-microfibril-angle-modulus-of-elasticity-and-compressive-strength-in-Eucalyptus-wood.pdf
Next step for me is to find an article on the applicable MFA for the different types of bow wood :)
Cheers,
Phil
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to willie: found another interesting article on MFA:
http://www.intechopen.com/books/cellulose-fundamental-aspects/cellulose-microfibril-angle-in-wood-and-its-dynamic-mechanical-significance
Cheers,
Phil
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PS to my last post: you can also download that article on MFA as a pdf file. It is much more readable that way.
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thanks for the links, looks like good reading after work tonite.
there was a discussion a while back about MFA a while back.
http://www.primitivearcher.com/smf/index.php/topic,55682.0.html
sure would be nice for a bowyer to be able to inspect his materiel, and see the actual microfibrill angle of any given piece.
a paper that might interest Yew guys http://e-collection.library.ethz.ch/eserv/eth:30567/eth-30567-02.pdf (http://e-collection.library.ethz.ch/eserv/eth:30567/eth-30567-02.pdf)
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Thanks willie, I have read the article and I and I think it warrants further discussion as to the impact of > MFA on "springiness" of the wood (I have no idea and his sample size of 1 is of course not scientific which he readily admits).
In the scientific articles to which I have provided the links to, it indicates that > MFA = less compression strength and stiffness (negatively correlated) and also has all the other negative traits he listed (moisture uptake, shrinkage, > checking etc). The idea of making a thicker bow due to the reduced stiffness and compression strength of juvenile wood when using saplings (or using the first 20-30 growth rings in mature wood) might have merit if it were to increase the "springiness" of the wood.
I think what would counteract that is that the radius of the growth rings would be tighter in those first 30 growth rings and would produce a more heavily crowned bow.
Interesting discussion for sure and I am interested to hear what your opinion and that of others is on this topic.
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Philip, I wish I knew how to read those charts. When you talk about springiness in the wood it is actually very definable. You have work in and work out as you do in any spring minus hysteresis. The Hysteresis can vary greatly from bow to bow and wood to wood depending on how well the bow was made and how dry the wood is. A dry piece of wood has very little hysteresis until it has been over stressed. Almost all woods are just about equal in springiness as long as they are working within their elastic limits and are equally dry.
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I have noticed set acting differently in hardwoods and softwoods. Some larch I have tillered recently seems to take set early on, but recovers from more set than I am used to in hardwoods. Of course designs utilizing compression wood for the belly exhibit this trait even more so. The merit for differing woods depends on your intended use, I suppose. At the one extreme, Badgers preference for a bow that takes some set, (but doesn't go through a recovery process), might be what works well for his flight shooting. On the other hand, the bow shown below is a compression wood belly, and needs to recover after a sustained full draw.
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This website has something interesting to say in the comments about Osage ww.wood-database.com/osage-orange/, sorry but even though it doesn't appear to be a commercial site you will have to fill in the rest of the link. I especially like the comment American French ::)
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At the time it was given that moniker the French still had designs on making America theirs. lol
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So I'll apologize up front for this. I haven't read any of the many comments so maybe it's already been mentioned, but...
There's gotta be all kinds of jokes about massaging your stick. >:D
Sorry, couldn't help myself.
Tattoo Dave
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So I'll apologize up front for this. I haven't read any of the many comments so maybe it's already been mentioned, but...
There's gotta be all kinds of jokes about massaging your stick. >:D
Sorry, couldn't help myself.
Tattoo Dave
Maybe so but not on this board, not unless you want to remain a member that is