Post by: Shredd on December 24, 2021, 12:38:38 AM
So far I built 4 sets of these limbs... I am gonna concentrate on the two fastest pair of limbs to take my notes from... Cobra limbs #2018 and #2021... I will look at the notes on the other two bows to know what not to do and what to stay away from...
Today i was gonna start by looking at the info on those two bows and figure out stack heights and what changes I was gonna make to increase the speed on the new limbs... Instead I decided to take limbs #2021 and take them down a few pounds to use on my 20" target riser... That will give me some insight before I start the new limbs... They came in at 48# on a 16" riser and 43.2# on the 20" riser... The target weight is 40 to 41# @ 28"... I began by trapping the last third of the limb which had a slight reflex for about 7 to 8" before the hook... I pulled on the string vertically to check vertical stability... It was very, very slightly unstable... I took a little off at a time checking limb shape at brace and arrow speed... If I start losing arrow speed I would stop the process or take some off the base of the limbs... As you can see by the numbers I did not lose any speed percentage wise and actually may have gained a hair more speed especially with heavier arrows... That is a good thing... Plus the limbs got very stable vertically after the first sanding of two... It's amazing how such a small tweak can make a noticeable difference... Now I know not to mess with the limb section before the hooks with the new limbs... I found it is always better to have a little reflex in that area because to adjust and fine tune, just do a little sanding...
Here are the numbers... It takes lots of notes, time and testing a to make little gains... You gotta be stubborn and half crazy to do this chit... :banghead: :biglaugh: It's my passion...
Post by: Shredd on December 24, 2021, 12:42:36 AM
Post by: Shredd on December 24, 2021, 12:45:08 AM
Post by: Shredd on December 24, 2021, 12:46:45 AM
Post by: Shredd on December 24, 2021, 12:49:16 AM
Post by: Mad Max on December 24, 2021, 07:04:33 AM
How many bows did you make over the years chasing speed?
Post by: Stagmitis on December 24, 2021, 09:26:58 AM
Post by: Flem on December 24, 2021, 09:28:03 AM
Post by: OldRawhide42 on December 24, 2021, 09:58:35 AM
Post by: Shredd on December 24, 2021, 10:55:16 AM
Flem.. Yes..!! Been to many uncharted territories... For me that is what life is all about... Exploring the unbeaten path... You will see in this thread how I use DFC's, where I don't see anyone else going to this level...
Post by: Shredd on December 24, 2021, 11:34:29 AM
First Tip...
** WARNING** No one should take what I say as an absolute... Anyone can make mistakes, be mislead, be wrong or be wrong in their theories... I had a mentor that gave me lots of info on performance... A lot of it was good stuff that I will hold on to but as I learned more and more about bows and how they work I found that there where about a half dozen things that he told me that were blatantly untrue... I tried to reason with him but he is ornery and set in his ways... At that point the student became the teacher and he could not handle that... I am still very grateful for what he taught me but sad that I had to part ways...
Take what I have to offer you, retain it and see if it works for you one day... And if it does not I would appreciate if you came to me and discuss it so we both can learn...
I will share with you that I tell my friends when we do stuff together... " It's all about the mission... Put pride and ego aside... It's all about the mission..." Another wards to accomplish the mission is priority number one, cast pride and ego aside...
Keep an open mind and think out of the box and you will go a long way...
Well that was the philosophical part... :)
Post by: Appalachian Hillbilly on December 24, 2021, 01:52:53 PM
You have my utmost attention! Please continue! Looking forward to learning all I can!
Post by: OldRawhide42 on December 24, 2021, 03:35:30 PM
Post by: Appalachian Hillbilly on December 24, 2021, 03:47:26 PM
If they are unstable when you hang the weight from the bottom,, you get lateral movement in the limb set? String and limbs move to one side or the other?
If they track straight, you are good??
Post by: OldRawhide42 on December 24, 2021, 03:58:13 PM
Post by: Appalachian Hillbilly on December 24, 2021, 04:15:46 PM
Post by: OldRawhide42 on December 24, 2021, 04:45:41 PM
Post by: Shredd on December 24, 2021, 09:10:54 PM
Post by: Appalachian Hillbilly on December 24, 2021, 09:30:26 PM
Post by: Shredd on December 25, 2021, 12:30:09 PM
Hillbilly... It is not so much where the limbs are bending as it is the way the limbs act through the shot cycle (when the string is released)... Floppy limbs may make the bow sensitive to shoot... As you can see in the pic my limbs are bending very nicely but at brace the tips were just a hair floppy...
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Post by: Mad Max on December 25, 2021, 01:07:29 PM
Here is a good picture of unstable at 1st brace off the form
the left limb is stronger and it's not braced high enough, needs tiller and braced higher.
If you grab the string and push it to the left the left limb will lay on the string and the right limb will bend more.
This bow was fine and stable after I finished the tiller
(https://i.imgur.com/U7QkjWf.jpg)
Post by: Appalachian Hillbilly on December 25, 2021, 02:16:12 PM
How much faster do they make it?
Post by: Mad Max on December 25, 2021, 03:23:12 PM
Let's stay on the Topic of Cobra limbs
Post by: Shredd on December 26, 2021, 12:02:51 PM
Post by: Shredd on December 26, 2021, 12:07:02 PM
Post by: Shredd on December 26, 2021, 12:26:51 PM
Post by: Flem on December 26, 2021, 12:35:05 PM
Post by: Shredd on December 26, 2021, 12:40:48 PM
Sorry... I tried to increase the size of the pics to make more readable... Maybe good ol' Roy can lend a hand...
Post by: Mad Max on December 26, 2021, 12:57:05 PM
Post by: OldRawhide42 on December 26, 2021, 01:40:53 PM
Post by: Shredd on December 26, 2021, 03:02:46 PM
Post by: Shredd on December 26, 2021, 03:06:32 PM
Anything I post on here is open for discussion... Do some of you have thoughts on floppy and vertically unstable limbs and shootability??
Do any of you experienced bowyers have any opinion on floppy, vertically unstable limbs??? I am repeating the question because you all may have been busy with Christmas stuff...
Post by: Appalachian Hillbilly on December 27, 2021, 06:34:26 AM
pardon my ignorance.
Post by: Shredd on December 27, 2021, 08:29:37 AM
Post by: Shredd on December 27, 2021, 10:17:03 PM
When you are comparing two sets of limbs of the same design and you want a smooth draw... It is simple... Just go by the numbers... Big in the beginning of the draw and small at the end... If you want performance it is more of a balancing act... You want an optimal curve on the DFC graph... It's all about how those limbs are gonna unfurl during the shot cycle to transfer their energy to that arrow... I think it is about keeping a nice even pressure on that arrow during the whole shot cycle... I believe a straight limbed bow will have most of the pressure on the arrow at the beginning or the shot cycle...
Below is a DFC of those big oversize hooked recurve limbs... I drew a line on the graph from the first to last point... A lot of people say that space between the line and the curve is stored energy... I am not sure I believe that... And if it is stored energy they did not do the best job at delivering it to the arrow... I know of a few bows with a lot flatter DFC that goes just as fast or faster than one of these type bows... Granted they are fast but going by the theory that the DFC shows almost twice as much stored energy you would think it would be a whole lot faster...
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Post by: mmattockx on December 28, 2021, 11:27:30 AM
As a general rule a bow with higher numbers in the beginning of the DFC (10") and low numbers at the end of the DFC (28") is usually the faster bow...
This is why compounds are the kings of speed, they draw very heavy at the start and then drop off at the end for easy holding at anchor. Their DFC's are hugely pumped up with that high early weight for lots of energy storage and the limbs are super short and stout for minimal energy loss during the shot.
I drew a line on the graph from the first to last point... A lot of people say that space between the line and the curve is stored energy... I am not sure I believe that...
The area under the DFC curve down to the x-axis is indeed the energy stored. The big hook recurves lose out by needing heavy outer limbs to keep stability and through a lot of noise and vibration eating up energy during the shot.
Mark
Post by: Longcruise on December 28, 2021, 11:37:46 AM
Quote
The area under the DFC curve down to the x-axis is indeed the energy stored. The big hook recurves lose out by needing heavy outer limbs to keep stability and through a lot of noise and vibration eating up energy during the shot.
I agree. However, it's easy to doubt that since there are other effects that can influence the dynamics such as hysteresis, weight of the limb material and (not certain on this one) location of the neutral plane.
Post by: Appalachian Hillbilly on December 28, 2021, 12:58:46 PM
How do you quantify or translate DFC to speed or efficiency? Could the are under the curve between the linear blue line be efficiency loss?
I think what we really would like to see, is not necessarily Draw Weight Curves, but a "map" of the energy being released into the arrow per inch upon release, then draw a correlation between the two.
Post by: mmattockx on December 28, 2021, 02:06:58 PM
How do you quantify or translate DFC to speed or efficiency?
There is no way to that I know of (not that that means much overall...). All the DFC gives you is the energy stored and how smooth the draw cycle is. Efficiency not only depends on how much energy the bow wastes due to excess limb weight and vibration, but also the weight of the arrow. Heavy arrows increase bow efficiency because they absorb more of the energy in the shot, leaving less behind in the limbs to be wasted.
I think you can get some idea of the inherent bow efficiency separate from the arrow weight by working with dry fire speeds, but I have not looked at them yet and am not that familiar with them. The flight shooters care a great deal about this because it is very important with their light arrows.
Mark
Post by: Stagmitis on December 28, 2021, 05:08:14 PM
Post by: Buemaker on December 28, 2021, 07:16:43 PM
Post by: Buemaker on December 28, 2021, 08:01:35 PM
https://dryadbows.com/wp-content/uploads/2021/04/connie-Defining-Bow-Performance-Dryad.pdf
Post by: Shredd on December 28, 2021, 10:29:44 PM
On the hex 8 dfc that I posted... I don't think it is the exact same bow but the DFC should be very similar... In Tradlab there is a border bow doing 189 @ 10gpp my bow does 188 with a lot less pronounced DFC... If you wanna say that the extra weight on the limbs is holding it back then why at 11 gpp that bow is not making any gains over my bow?? If it was a better design with all that stored energy it should be picking up speed when the arrow weight goes up when compared to my bow...
Another example... My buddy has a 50 lb. Mild R/D bow... I have a 41 lb. R/D bow... His stored energy is way more than mine just for the fact it is 50 lb... With a 410 gr. arrow his does 172 fps and mine does 183 fps... That is nine lb. lighter and 11 fps faster... To match his bow in speed I would have to build a 36 lb. bow... Where is all this stored energy?? When looking for speed, to me stored energy is somewhat a myth and I don't concern myself too much with it... I feel what you should really concern yourself with is what the chrony says, how your limbs are bending, learning what the DFC is trying to tell you and finding some kind of balance with the DFC... You are trying to build a Bruce Lee not a line backer...
Good stuff Bue... You aint sidetracking nuttin...
Stag... Grossly over weight limbs are a no-no... But slightly heavier limbs don't matter too much...
Hillbilly... A map of energy into the arrow would be tits...
Post by: Mad Max on December 29, 2021, 08:26:08 AM
Your bow it the fastest one on there. :)
Post by: Shredd on December 29, 2021, 08:48:19 AM
https://www.thetradlab.com/bordercvxw
Post by: Mad Max on December 29, 2021, 08:55:37 AM
Post by: Shredd on December 29, 2021, 09:14:38 AM
https://www.thetradlab.com/uuukhavx
Post by: mmattockx on December 29, 2021, 10:41:58 AM
Where is all this stored energy?? When looking for speed, to me stored energy is somewhat a myth and I don't concern myself too much with it...
Stored energy isn't a myth as such, it is a real thing we can measure. But it isn't as important as the other details, like you say. Your Bruce Lee instead of a linebacker idea is right on I think. I have read other people talking about how changing pad angles on a takedown to change the initial string tension can significantly affect the vibration levels and speed. It is a complex system with a bunch of interconnected variables that performance can be very sensitive to.
Mark
Post by: Mark R on December 29, 2021, 02:39:55 PM
Post by: Mad Max on December 29, 2021, 03:09:21 PM
Do you what the limbs are made of?
You don't see any wood in the stack, it's all black
Post by: mmattockx on December 29, 2021, 06:25:51 PM
Do you what the limbs are made of?
You don't see any wood in the stack, it's all black
According to Uuka those limbs are all carbon layers with no core of any type, wood or foam.
Mark
Post by: Shredd on December 29, 2021, 07:17:46 PM
Post by: Mad Max on December 29, 2021, 07:37:47 PM
I will get started :tongue:
Post by: Stagmitis on December 29, 2021, 07:54:07 PM
Post by: Flem on December 30, 2021, 09:52:31 AM
Be like shooting a metal bow, but lighter :tongue:
Post by: Buemaker on December 30, 2021, 10:33:02 AM
Speed test Uhkka vs WW and Hoyt.
Post by: Flem on December 30, 2021, 11:05:02 AM
Post by: Shredd on December 30, 2021, 02:59:49 PM
I would like to share with you what is in my head about making a better performing bow... All these terms like dynamic efficiency, stored energy ect.ect. are all nice and dandy but to me they seem after the fact... After you make a bow you can do all the math and say it has this and that... Can these things help to build a faster bow?? I don't know... Maybe they can... The only thing I am concerned with is how fast that arrow is leaving that bow... After that you can move the wedges to get a bow that stacks a little sooner or draw a little smoother for desired shootability but you will lose some speed... That is something that I have not messed with yet... When I have a job of making a faster bow I am not looking at it as an olympic shooter, a engineer with blue prints, a mathematician ect. ect... I look at it as a bowyer with a hunk of wood and glass in front of me and the previous bow I made and it's DFC... I look at the speed of the bow, how the bow is bending and the DFC... I say to myself, how can I increase the speed or what numbers do I need on that DFC to increase the speed and how am I gonna go about getting the desired numbers I want to increase it's speed...
If anyone out there can educate me on how to make a faster bow using those other terms describing a bows performance, I am all ears...
Post by: Appalachian Hillbilly on December 30, 2021, 08:58:27 PM
I look at bows and think of things like what angle is more effecient at pulling on the string and how does this correlate to what arc the tip travels in? Bows with tips that travel in a long arc, short arc or straight up and down similar to a short limb compound....
Post by: Shredd on December 30, 2021, 11:48:57 PM
As for arc of limb bending I gave it some thought from time to time... That's about it... For the most part keep your bows over 62"... On longer bows like 68" you should probably go with shorter, snappier limbs... Make sure you have a consistent bend throughout the limb except about the last 4 to 5 " which should be relatively stiff...
These are my guide lines for a decent performing bow...
Remember that every bow is different and may not jive with my guidelines... You got to experiment and find out what works for that design...
Post by: Longcruise on December 31, 2021, 02:07:05 PM
My formula is very similar to yours except for the power lam.
Post by: Shredd on December 31, 2021, 02:33:56 PM
Post by: Longcruise on December 31, 2021, 05:35:16 PM
Post by: Shredd on December 31, 2021, 07:29:25 PM
Post by: Bvas on January 02, 2022, 03:32:57 PM
I like a fast bow, and would love to “chase the speed”. But I have neither the time or budget to validate an attempt. And to be honest, I am content knowing my bows are faster than all of the vintage production recurves I own.
These are some of my thoughts(which you may have already had).
A fast moving arrow requires a fast moving string. Constant acceleration to the stop would probably be optimal. I believe this is why you want limbs to more gain weight early in the draw cycle.
To reach maximum string speed requires the limb tips going from point A(full draw) to point B(braced) as quick as possible. There are only two ways to accomplish this.
1. Get the tips moving as fast as possible.
2. Get the distance from A to B as short as possible. This can be done two ways. Get the two points closer together or reduce the arc traveled between the two points.
Sorry I don’t have any great wisdom on how to accomplish this. Just a hillbilly spewing some of the random thoughts that go thru my head.
Post by: Buemaker on January 02, 2022, 04:31:06 PM
2. Get the distance from A to B as short as possible. This can be done two ways. Get the two points closer together or reduce the arc traveled between the two points.
Sorry I don’t have any great wisdom on how to accomplish this. Just a hillbilly spewing some of the random thoughts that go thru my head.
This is my thinking on this. I guess we could call it short limb travel. I think one way to obtain this is by using thin longer fadeout wedges and stiffer or stiff tips. Bue square head engineer.
Post by: kennym on January 02, 2022, 04:51:20 PM
I agree with this, if you stiffen at riser and tips, you bend limb more/most in midlimb. When arrow is released, the midlimb is doing the work and as it straightens, the tip moves forward faster.
At least that is the way I see it in my mind's blurry eye... :biglaugh:
Post by: Mad Max on January 02, 2022, 05:12:14 PM
. When arrow is released, the midlimb is doing the work and as it straightens, the tip moves forward faster.
I agree with this
Post by: Shredd on January 02, 2022, 08:12:59 PM
I will post something when I make my final decision... Sorry for dragging my feet... I got a bit of stuff goin on...
Post by: Cherry Tree on January 02, 2022, 11:16:24 PM
Post by: Shredd on January 03, 2022, 12:01:10 AM
Post by: Cherry Tree on January 03, 2022, 09:05:48 AM
Post by: Buemaker on January 03, 2022, 09:19:47 AM
Post by: Cherry Tree on January 12, 2022, 06:34:29 PM
Post by: Shredd on January 12, 2022, 11:30:42 PM
A year or so ago the boys were laughing at me, saying there was a flat spot in my limbs... There was no flat... It is an optical illusion... I opted for a performing limb over of a graceful curved limb... The results 188 - 190 fps vs 180 or slower... I think people get hung up on the way things are supposed to look vs the potential of what the limbs can do... Maybe they go for the look that sells more bows... But then they might want that smoother drawing, slower shooting, quieter bow... I think you could probably get the same feel and quietness out of some optimally performing limbs just by using a heavier arrow... Below is a pic of the limbs with the so-called flat spot...
I have not messed too much with different lengths... A 64 to 65" bow seems to be a good standard length so I generally go with that... You could probably make about 15 to 20 different bows out of one bow design by varying length, width and tapers... Even though I have learned a lot in 3 years of intense, totally dedicated bow building I feel I have just scratched the surface and there is so much more to learn...
The bow below has the best DFC numbers on any bow that I have ever built... High tension at brace and super smooth to draw...
Post by: Appalachian Hillbilly on January 13, 2022, 07:24:11 AM
Post by: Shredd on January 13, 2022, 07:46:00 AM
Here is a pic of typical recurve... Notice how the outer half of the limb has a gradual curve that gets tighter and tighter as you get near the tips... The bow looks great unstrung and at brace with nice flowing curves.. But look what happens at full draw... To me, not so pretty... all the bend is in first half of the limb... Most of the recurves I see are designed this way... I could be wrong and be missing out on something but most of these bows look like they are super smooth drawing but lack in performance of what they could have with a larger working portion of limb...
Post by: Shredd on January 13, 2022, 08:30:04 AM
Post by: Appalachian Hillbilly on January 13, 2022, 09:51:28 AM
How do you thicken or stiffen just the tips on a recurve without adding the extra curl?
If you add a short piece of lam in the stack at the end, how do you keep it in the stack and not squirt out the end? Or do you run a reverse taper core?
Post by: Shredd on January 13, 2022, 10:03:55 AM
Stop your curve and wedge where you want the limb to stop bending... On my bow I went from a large radius straight to a small radius... It's not gradual like a french curve like you see on most recurves..
Post by: Mad Max on January 13, 2022, 10:07:23 AM
you could make your wedge stick out (longer than the stack) and let it bump up against a nail to keep it from squirting out
Post by: Mad Max on January 13, 2022, 10:21:18 AM
(https://i.imgur.com/Bf1vOKG.jpg)
You can see all the limb is working--18-1/2" working limb
(https://i.imgur.com/E1f34iz.jpg)
(https://i.imgur.com/SpJL3cD.jpg)
Post by: Arlo on January 20, 2022, 09:15:13 PM
Anything I post on here is open for discussion... Do some of you have thoughts on floppy and vertically unstable limbs and shootability??
Do any of you experienced bowyers have any opinion on floppy, vertically unstable limbs??? I am repeating the question because you all may have been busy with Christmas stuff...
Absolutely...There are a lot of bows on the market being built that are borderline what i consider "vertically unstable" Grabbing the string in one hand and the riser in the other you can easily move the string up and down moving both limbs. Another test is standing the bow on the lower limb tip vertically and push the top limb tip down with your hand. It easily wiggles both limbs causing limb bulge....
With all this said, vertically unstable bows can still be very high in performance, but squirrely too....They are very sensitive to finger placement and release consistency. Take this unstable bow, and bring it to full draw... then rock your finger pressure high and low a bit.... You will notice more a lot more movement in the limbs with a vertically unstable bow.
next thing to ask is .... What determines a limb design that is vertically unstable vs a rock solid one? That answer is very long, and many options and opinions, but it starts with geometry...... Was that helpful?
Post by: Shredd on January 20, 2022, 09:39:39 PM
Post by: OldRawhide42 on January 21, 2022, 02:25:01 PM