Primitive Archer
Main Discussion Area => Bows => Topic started by: bushboy on October 23, 2016, 05:38:58 pm
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I'm currently working on a bow that have around 50 arrows through it and it's holding it's profile well.i braced it and let it sweat for 5 hours.unbraced it's profile changed by 1-3/4",ten minutes later the profile. Was almost back to where it started.having noticed this before but not to such a degree.thoughts,bush!
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Here's. The bow,heavy heat treated elm.
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seems to be reasonable,, the answer is in how the bow is shooting,,
I will add that is why I like to have a chrono,,
takes a bit of the guess work out,, I can test the cast after sweating and see show it is doing,, if it has reasonable cast,, and the profile is stable,,,I feel like the bow is ok,,
I dont know if 50 arrows is going to give you the whole story,, but its a good start,,, it might shift a bit after 1000 arrows,, depending on the design,,
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Shoots well,willow. Leaf design.
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String follow or set, as long as its not over a certain amount, no biggy. The bow shoots well, no worry. :) My last bow took about 2" of set and 1" of string follow.
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side question. are there woods that inherently take more set or is it always just due to tillering
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First question...yes. Second question....no. Some woods have more compression elasticity than others. You simply account for that in the design. Narrow the back relative to the belly as an example. Tempering will also harden the belly up so that it is forcing the back to do more work, lessening the strain on the belly and thereby Lessing the set.
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Thats not too bad considering the amount of reflex you have in the bow. I have found a bow that doesn't recover after sitting for a while will actually perform better than a bow with the same profile that does recover. Recovery is an indicator of hysterisis in the bow. Thats one of the reasons I cut way back on the amount of reflex I build into the bows.
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Badger,, I keep thinking bout that,, I have a bow that does not recover,, it has string follow, but nice cast,, until you said that I wasl totally confused,, :)
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Badger,, I keep thinking bout that,, I have a bow that does not recover,, it has string follow, but nice cast,, until you said that I wasl totally confused,, :)
Brad, I know you have been at this long time as I have. It took about 15 years or more before I realized this. The recovery actually starts the minute you let go of the string but it is much slower than the arrow so you don't get any benefit from it. So if a bow has 1 1/2" and recovers after 1/2 hour it might actually have 3" at the moment you take the shot.
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Post more pics of that bow, it looks awesome! And upload them somewhere else, they're too small here..
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Badger,, I keep thinking bout that,, I have a bow that does not recover,, it has string follow, but nice cast,, until you said that I wasl totally confused,, :)
Brad, I know you have been at this long time as I have. It took about 15 years or more before I realized this. The recovery actually starts the minute you let go of the string but it is much slower than the arrow so you don't get any benefit from it. So if a bow has 1 1/2" and recovers after 1/2 hour it might actually have 3" at the moment you take the shot.
I love this statement
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Badger,, I keep thinking bout that,, I have a bow that does not recover,, it has string follow, but nice cast,, until you said that I wasl totally confused,, :)
Brad, I know you have been at this long time as I have. It took about 15 years or more before I realized this. The recovery actually starts the minute you let go of the string but it is much slower than the arrow so you don't get any benefit from it. So if a bow has 1 1/2" and recovers after 1/2 hour it might actually have 3" at the moment you take the shot.
A person should be able to see that on a bow using a poundage tester.
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Hysteresis? :\ So.. does that mean slightly "overbuilt" bows may perform better?
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Hysteresis? :\ So.. does that mean slightly "overbuilt" bows may perform better?
I might not consider what you consider overbuilt. If a bow takes set and was properly tillered it is either too wet or under built for the design we are using. We used to hear that a good bow was 90% broke. I think a good bow is only about 70% broke. We enter the plastic range long before we enter the rupture phase. We want to keep the bow in the elastic range.
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Badger,, I keep thinking bout that,, I have a bow that does not recover,, it has string follow, but nice cast,, until you said that I wasl totally confused,, :)
Brad, I know you have been at this long time as I have. It took about 15 years or more before I realized this. The recovery actually starts the minute you let go of the string but it is much slower than the arrow so you don't get any benefit from it. So if a bow has 1 1/2" and recovers after 1/2 hour it might actually have 3" at the moment you take the shot.
Every once in a while someone says something that just seems right. This is one of those. Thanks Badger
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That doesn't mean it is right.
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No, but until someone comes along with something that seems righter. it'll do ;D ;D ;D
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That doesn't mean it is right.
Pat, I actually tested it. It was somewhat by accident that I discovered this. A real pain in the ass to test so I won't ever test it again but I feel it told me what I needed to know.
recovery of set happens in stages. lets say a bow has 3" of set, the first 1/2" might recover in 1/10 of a second the second 1/2" might take 3 seconds, the third 30 seconds, each phase will take longer. Any phase slower than the arrow is hysterisis.
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TBB V material right here.
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Badger....So what your saying is you think immediate checking of degree of reflex after shooting does not mean what the arrow is getting.
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That doesn't mean it is right.
Pat, I actually tested it. It was somewhat by accident that I discovered this. A real pain in the ass to test so I won't ever test it again but I feel it told me what I needed to know.
recovery of set happens in stages. lets say a bow has 3" of set, the first 1/2" might recover in 1/10 of a second the second 1/2" might take 3 seconds, the third 30 seconds, each phase will take longer. Any phase slower than the arrow is hysterisis.
Describe your test.
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Pat I love your :) attitude,
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That doesn't mean it is right.
Pat, I actually tested it. It was somewhat by accident that I discovered this. A real pain in the ass to test so I won't ever test it again but I feel it told me what I needed to know.
recovery of set happens in stages. lets say a bow has 3" of set, the first 1/2" might recover in 1/10 of a second the second 1/2" might take 3 seconds, the third 30 seconds, each phase will take longer. Any phase slower than the arrow is hysterisis.
Describe your test.
Several premises in invoved, A fiberglass bow and an all wood bow have 1 major difference. This is hysterisis, Fiberglass bows have less than 2%. Because of this you can work out the virtual mass on a fiberglass bow by carefully calculating stored energy, chronoing the bow and determining the efficiency. Once you know the virtual mass you can easily extrapolate expected speeds of different arrow weights with pretty good accuracy. This does not hold true for a bow with hsyterisis because hysterisis is also time sensitive, the faster the arrow leaves the bow the more hysterisis it will have. This makes it almost impossible to really apply a meaningful virtual mass to a wooden bow. About the closest we can get is to check the efficiency of an extremely heavy arrow and go from there. What I found by testing bows prior to taking set at shorter draw lengths that hysterisis was almost non existent and I could accurately establish a virtual mass and extrapolate arrow speeds just like with fiberglass bows. As the bow was drawn out further and started to take even small amounts of set this method would quickly collapse. I don't want to go into a lot of detail because it is more writing than I feel like doing but this is the basic method I used to test it.
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Love it.
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Quite the process,compromises,and attention to detail of materials taking huge amounts of time invested.Doing this with many different types of bows had to take even more time,and as accurately as can be done I would say given the type of materials used.More than most will do and many have benefited from your research.Even FG bow makers too.
Still making and shooting a broke in primitive bow that took very little hard set from tillering[under an inch] and shows very little soft set[under an inch] after being shot a couple of hours are and have always been the priority.Reducing the amount of noticable hysterisis a bow has.Showing me the limbs are not stressed and will stand the test of time.Just like over by you.I have the luxury of shooting with a couple of bow makers here especially one that does quite extensive testing himself.
There are definitely designs in primitive bows that will out shoot common FG bows here,but if their designs are made properly they still can get the upper hand over a longer stretches of time is what we've found just because of their practically 0 hysterisis materials.Not very noticable but still noticable.Even then some FG bows designed to the edge can and will fly apart or delaminate a bit with a fly apart on the horizon....lol.
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I really don't see how that proves that the bow might have three inches of set during the shot process.
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I really don't see how that proves that the bow might have three inches of set during the shot process.
Pat, the 3" is not a hard number, it simply shows that a bow has more set than we see when we unbrace it.
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I'm currently working on a bow that have around 50 arrows through it and it's holding it's profile well.i braced it and let it sweat for 5 hours.unbraced it's profile changed by 1-3/4",ten minutes later the profile. Was almost back to where it started.having noticed this before but not to such a degree.thoughts,bush!
Have you made any other bows from this same wood source?
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I'm currently working on a bow that have around 50 arrows through it and it's holding it's profile well.i braced it and let it sweat for 5 hours.unbraced it's profile changed by 1-3/4",ten minutes later the profile. Was almost back to where it started.having noticed this before but not to such a degree.thoughts,bush!
Rob, I've experienced the same thing on a couple of elm bows I made recently. Both were heavily heat treated with a fair amount of reflex added in. Set after tillering was about average but the bows seemed to follow the string a bit much after
each shooting session of 50 or so arrows. Both recovered back to the same amount of reflex that they held prior to the shooting session within 10 to 30 minutes after unstringing depending upon how long they were braced. What I noticed
about these bows is that they didn't snap back to their original profile right at the time of unstringing like the better shooting bows I have seem to do. I'm thinking this is something in the property of this batch of elm.
Could be my workmanship or the design at play though. :o
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Same here Greg. Every once in a while you run into an elm that is snappy. I wish I knew the characteristics ahead of time. Hardness doesn't seem to matter.
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Thats not too bad considering the amount of reflex you have in the bow. I have found a bow that doesn't recover after sitting for a while will actually perform better than a bow with the same profile that does recover. Recovery is an indicator of hysterisis in the bow. Thats one of the reasons I cut way back on the amount of reflex I build into the bows.
Does that simply mean that bow which has less set, is better? As it of course should be. Does the same profile means profile right after shooting (unstringing) or after resting a day? So, is (side profile) recovering similar variable as set right after shooting? The bow, which has less set after shooting is better than bow which has more reflex after recovering but less right after shooting?
This phenomenon is viscoelasticity.
en wikipedia.org/wiki/Viscoelasticity
Maybe different wood species has different viscoelasticity "coeffiecient"?
And maybe we should define term "set" better. Is it set right after shooting (unstringing) or after resting an hour, a day, etc.? Is set just inaccurate estimate of hysteresis of the bow? This is very interesting but also quite challenging topic!
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Thats not too bad considering the amount of reflex you have in the bow. I have found a bow that doesn't recover after sitting for a while will actually perform better than a bow with the same profile that does recover. Recovery is an indicator of hysterisis in the bow. Thats one of the reasons I cut way back on the amount of reflex I build into the bows.
Does that simply mean that bow which has less set, is better? As it of course should be. Does the same profile means profile right after shooting (unstringing) or after resting a day? So, is (side profile) recovering similar variable as set right after shooting? The bow, which has less set after shooting is better than bow which has more reflex after recovering but less right after shooting?
Tuomo, set is what you see the instant you unstring the bow, in reality it is probably about double what you actually see. The bottom line is string tension at brace after the bow has been taken to full draw a few times, that tells all you need to know.
This phenomenon is viscoelasticity.
en wikipedia.org/wiki/Viscoelasticity
Maybe different wood species has different viscoelasticity "coeffiecient"?
And maybe we should define term "set" better. Is it set right after shooting (unstringing) or after resting an hour, a day, etc.? Is set just inaccurate estimate of hysteresis of the bow? This is very interesting but also quite challenging topic!
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Very interesting read. Thanks!
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Thanks for the replies!interesting stuff!this is one half of a stave of a small tree(the other half is not finished).this bow had deflex right off the saw and also had a quite low bend resistance,but after recurving, set back handle and a heavy heating it pick up quite a bit of draw weight.it's short @ 55" ttt and around 35#@24",made for my cousin chery and only weighs 12.5 oz.yesterday,braced and 10 arrows it followed the string 1"and back to the original profile of 4-1/4" in front of the handle in short order.
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Very nice, I like that willow leaf profile bushy
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no matter what the set "looks like",, for me the bottom line is how does it perform,, its nice to learn bout this too,,
if you have same weight and draw bows and one holds 3 inche reflex, and it shoots the same as a bow with 1 inch follow,, the above discussion puts light on why this could be,, but still for me the performance of the bow tells the real story for me,,
yes I look at the set and how it recovers too,, but how it shoots is the most important to me,,
if you have not shot it through a chrono,, or flight tested it,, the look of the bow may not tell you what you need or want to know,, :) or the profile may mislead you to think it is shooting better than it might be,,, or it may be shooting better than you thought,,especially if it has a bit of follow,,
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Nice looking bow, glad it came out to suite you. :) I like a bow to hold reflex of course but mostly because they seem to be smoother to draw and less stack at the end with the early string tension. Other than that a little string follow don't mean you haven't built a good bow. :) Of course set and string follow are 2 different things and a lot of set isn't good. ;) I always like them to return to profile after a rest but what I really look at is where they are as soon as it is unstrung. :) Nice thread. :)
Pappy