Trad Gang
Main Boards => The Bowyer's Bench => Topic started by: Shredd on April 23, 2022, 01:19:24 PM
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Just stumbled across this and thought to share it with you guys... If you want to improve performance of a bow you might consider applying one of these techniques or principles to your limbs... Anyway, some food for thought...
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Did you forget something, Shredd? :dunno:
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Like what?? :wavey: :)
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And my name's not 'Shedd'... :laughing:
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????
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Methinks Shredd has forgotten to post a link.
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:laughing: :biglaugh: :laughing: LMAO..!!! :laughing: :biglaugh: :laughing:
Methinks you be right... I worked a long hard week and I am half dead today...
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Here she Be...
https://www.youtube.com/watch?v=D4LjkuyE-yg
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Thnx Shredd, I’ll watch it tonite.
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Fixed! :bigsmyl:
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You guys are awesome... Don't know what I would do without Y'all... :thumbsup:
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If you want to improve performance of a bow you might consider applying one of these techniques or principles to your limbs...
That was a good explanation of prestressing concrete structures. This is essentially what I am doing with my Perry reflex lam bows. I prestress the belly into tension in the unbraced position so that it sees a lower maximum compression stress at full draw. I'm not sure how applicable it is to FG lam bows but the technique could be used on the cores of HH or ASL bows to minimize how much set they take.
Mark
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Shredd - Interesting explanation of prestressed concrete beams. :thumbsup: Altho the function of beams is different than that of springs -bow limbs- it seems the same principles and forces are at work in both. I think Max was applying the principle of prestressing in his recent “Extreme Bow Reflexology” build-alongs e.g. see, All Fired Up. I mean 9-10” of reflex in a 48” bow is mind-bending, to me at least. Now that’s preload!
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I prestressed quite a few of my later longbows. Glued the lams up to the belly glass on a separate form and then glued to the reg form with the back glass. I’d I have to go back on my records as I have not made a bow in 5-6 years for the actual process. It was based on Fred Anderson’s style of bow building in his books snd research. Not a new Theory as it was being done years ago.
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I prestressed quite a few of my later longbows. Glued the lams up to the belly glass on a separate form and then glued to the reg form with the back glass.
What shape were the first form and the second form?
Mark
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:dunno: :laughing:
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If you Google Harold Groves, I believe he was a pioneer in pre-stressing, dynastress I think he called it.
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The pre stress in a bow limb using fiberglass or even wood is already being done by shaping the reflex in the form.
After watching this engineer explain the theory of a Post tension concrete floor or beam, it makes a guy wonder if you could run some piano wire in the core of a limb and adjust the tension after the bow was laid up.
This would sure add some strength to a straight ASL design, but I have no idea how it could be done effectively. I’ve built a lot of PT decks on parking structures and built 4-5 story buildings on them. So i I understand the concept….. but… I seriously doubt it could be incorporated into a bow limb.
Kirk
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The pre stress in a bow limb using fiberglass or even wood is already being done by shaping the reflex in the form.
You don't get much in the way of induced strain in a FG bow because the lams are too thin and flexible. In an all wood bow you can generate enough strain to be significant if it is done right. This is what Perry reflex does.
Mark
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Came across this on Fred Anderson’s builds.
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The pre stress in a bow limb using fiberglass or even wood is already being done by shaping the reflex in the form.
You don't get much in the way of induced strain in a FG bow because the lams are too thin and flexible. In an all wood bow you can generate enough strain to be significant if it is done right. This is what Perry reflex does.
Mark
I watched a few old videos and read some material about how Howard Hill was playing with a type of Perry reflex design. In these experiments they were reflexing the wood lams and gluing them up first. Then they would flatten them back out straight when the put the glass on the bow pre stressing the wood.
I can see how this would add both tension and relieve compression doing this..... But if you put the reflex in the lams and glass putting them in the form in a reflex shape.... and straighten the limb out when you are stringing it, it produces more tension at brace. The induced strain is applied as you string the bow in the form of "Pre load" at brace.
Look at that Boot Hill Express shape on the Big Foot weekend thread. I have built absolut replicas of Howard Hill long bows you could not tell the difference between them after they were strung. But there is a HUGE difference in performance.... not a little bit.... a LOT of difference with no hand shock either.
But..... The Howard Hill fan club turned up their noses to my design because of the shape of it unstrung.... Go figure. :dunno: :dunno:
Kirk
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Came across this on Fred Anderson’s builds.
Cool. Are these FG or wood bows being discussed?
I watched a few old videos and read some material about how Howard Hill was playing with a type of Perry reflex design. In these experiments they were reflexing the wood lams and gluing them up first. Then they would flatten them back out straight when the put the glass on the bow pre stressing the wood.
This is what I mentioned above for reducing the strain on the core and minimizing set.
I can see how this would add both tension and relieve compression doing this..... But if you put the reflex in the lams and glass putting them in the form in a reflex shape.... and straighten the limb out when you are stringing it, it produces more tension at brace. The induced strain is applied as you string the bow in the form of "Pre load" at brace.
This is not prestressing the components as such, but it does generate a lot more string tension at brace, as you say. I can believe what you say about your reflexed HH design, I think high string tension at brace is a good thing for stopping the limbs fast and it really pumps up the F/D curve and energy storage.
But..... The Howard Hill fan club turned up their noses to my design because of the shape of it unstrung.... Go figure. :dunno: :dunno:
People are fickle; they often choose tradition over performance. This applies to everyone on this forum, as well. Anyone interested in truly maximum bow performance shoots a compound. It is the modern solution to the question of how to best launch an arrow. And yet every last one of us doesn't choose a compound because we like traditional bows for other reasons.
Mark
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Mark. Eloquently stated for everyone. Some birds are multi color and others are black, green, but they all fly.!! Well said my friend. There is no right or wrong, only your own decisions.
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People are fickle; they often choose tradition over performance. This applies to everyone on this forum, as well. Anyone interested in truly maximum bow performance shoots a compound. It is the modern solution to the question of how to best launch an arrow. And yet every last one of us doesn't choose a compound because we like traditional bows for other reasons.
I can wrap my head around tradition, and respect the different opinions on that subject. But i disagree about traditional archers not being concerned with arrow trajectory, and kinetic energy. Higher performance traditional bows used for hunting provide a flatter trajectory, they hit harder, and are very quiet.
Good example would be the phone call i recieved this morning. This guy wants to lower his draw weight to something more comfortable, but still shoot his 512 grain arrows at a high 170's low 180's. and keep his trajectory the same as he was getting with a heavier bow..... This can be accomplished with a higher performance bow.
I get these kind of customers all the time wanting lower draw weight with good power....There are a lot of them too.
Kirk
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I can wrap my head around tradition, and respect the different opinions on that subject. But i disagree about traditional archers not being concerned with arrow trajectory, and kinetic energy.
I didn't say we aren't concerned with the performance of our bows, we do care. But that's not the absolute maximum performance possible with modern technology and design. We think a bow that shoots in the 180fps range is good, compounds shoot in the 300+fps range. With skill and good equipment compounds are good for hunting well past 60yds. How far can you reliably take game with a trad bow?
Mark
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No argument there at all brother... I was one of them for a lot of years and took elk with a compound bow at 80-90 yards a few times 300 fps 444 grain arrows..... But..... It's more like rifle hunting when you start shooting long distance, with the disadvantage of that 1.5 second flying time reaching the animal... It wasn't archery hunting any more to me.
I'm late to the game as a traditional archer. But Once i got the traditional bug and shortened up my game to close encounters, it was a lot more fun. But i can kill an elk at 40 yards with a good flat shooting 55# bow with 544 grain arrows, and blow right through them. Kirk
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But..... It's more like rifle hunting when you start shooting long distance
I agree with that. I've shot a buddy's compound a couple times and it feels way more like shooting a firearm than a bow. It's interesting for a few minutes then it gets boring once I start drilling arrows on top of one another shot after shot. It just feels like there is no character there at all.
Mark
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You have to tension the core and glue the back glass on at the same time, then you have to glue the belly on it in the form
Glass bow
Having a great time at the classic