I need some help on stack. I am going to build a mid 40s 60 " one piece recurve. I would normally use .260 but end with .002 taper. I have been reading on here about using .001 or parallel for a more stabil limb at lighter poundage.The bow will be semi static the hook without the extra tip reinforcement. 22" riser limbs tapered from fadeout to tip.
The latest off my form is 0.245" stack 0.001" taper with 22" riser gave 40 pretty much spot on.
I think 0.255" or so should get you in the ball park.
I can't help you on stack height. The shape of your limb, and limb pad angle will effect your stack height too.
But... the .001 taper rate will help out torsional stability a lot. Once you get below 40# go to a parallel, and 30# a reverse taper. Nothing worse than building light weight limbs that want to go sideways just looking at them wrong. Kirk
Same form just changing taper 255 might be a bit heavy and use some stable core to.
do you count the .015 stable core in your stack or is it stiffer like carbon. I am having trouble with going from .002 to.001 making the middle and tip .020 and .030 thicker. Better a little heavy than too light.
.stack stays the same just .015 less core lam and stablecore in its place.
I recently got some .019 woven carbon from overseas that can be used like stable core after you ruff it up so far the end effect seems much better than stablecore. I am using it in the trade bow.
Stic, do you have a picture of the woven? How do the edges hold up when you handle it?
The stuff I have has resin already.. from a guy on FB that posts in The Bowyers Corner. Mark Tom in China I think. Even with shipping less money than anything here..
It comes with both sides slick so I had to sand it with 120 grit. I can try to PM you the info if you want.
Please do :thumbsup:
Quote from: Crooked Stic on March 03, 2023, 09:00:50 AM
.stack stays the same just .015 less core lam and stablecore in its place.
I recently got some .019 woven carbon from overseas that can be used like stable core after you ruff it up so far the end effect seems much better than stablecore. I am using it in the trade bow.
Id be interested in where you ordered that .019 bias weave carbon, and the price. I've got some ultra light draw weight limbs that need some extra stability. That might do the trick. Kirk
Kirk if you are on Facebook get on the Bowyers Corner and look for Mark Tom.
$30 per 72"x1.5" Either .19 or .39 thickness- No shipping for 30 pieces or more- About $40 shipping to my addy in Md
He message me today with tracking #. I got 4 1.5 and 4 1.75 plus shipping was 200 to IN.
Thanks Mike.
Just got an email this am from Mark in China. Pretty quick response too.
i'm looking into getting a small order to try this stuff....
Are you putting this closer to the belly or the back for stability? I was thinking of going .030 glass belly and using the carbon against the bell glass for best results. Kirk
I put mine under the front veneer.Only one so far so cant say where it will be best at yet. I can tell quite a bit of difference between that and stablecore just by twisting on the limb This what it is in got a good amount of hook.
(https://i.imgur.com/tuBeog1.jpg)
Got this today. pretty quick this time.
(https://i.imgur.com/FSauzqP.jpg)
Looks great,how thick? JF
Quote from: Crooked Stic on March 17, 2023, 03:51:29 PM
Got this today. pretty quick this time.
(https://i.imgur.com/FSauzqP.jpg)
Can you put on the outside and no glass over it?
How is in terms of consistency of thickness? Sure looks good.
I have had no trouble with it being consistent. My trade bow has it in the limbs and was tiller dead on both ends right out of the form. And a lot more stable than stablecore.8 pieces with shipping from China $200.
Had this, too.
Good consistency.
And, of corse it's WAY better than Stabilcore.
Because this is 45/45 Carbon.
And Stabilcore is just 90/0 Glass.
Do we think srablecore would be better 45/45 ?
I think it would be better for torsional stability.
Quote from: Crooked Stic on March 17, 2023, 07:17:48 PM
I have had no trouble with it being consistent. My trade bow has it in the limbs and was tiller dead on both ends right out of the form. And a lot more stable than stablecore.8 pieces with shipping from China $200.
I just ordered 8 pcs of the 5 mm (.019) myself and will be trying it on some light draw weight static tip RC limbs as soon as I get the stuff. I think I'm going to use the stable core with this stuff, only put the carbon next to the belly glass and stable core towards the back. I think it may do better having that 45/45 towards the belly...... we shall see. I'll mix up the second lay up and see if it makes a difference.
Another lay up I'd like to try is using this stuff on the back instead of glass over stable core. The total composite thickness would be .034 with the carbon and stable core.... This could be used on limbs up to 55-60# me thinks.... Kirk
I would be interested in trying on the back and belly, no glass on a Longbow. Just for curiosity and looks
Quote from: B-JS on March 18, 2023, 02:01:51 AM
Had this, too.
Good consistency.
And, of corse it's WAY better than Stabilcore.
Because this is 45/45 Carbon.
And Stabilcore is just 90/0 Glass.
Hi sorry can you explain the 45/45 and the 90/0 ? For me please ! :help:
Kirk why do you think it will be best towards the belly?
Jeff being only .019 with no glass might not be enough actually just the twill adds no stiffness just stability. You can get 6 ply .050 with uni. On the front and just twill on the belly and get by with no glass. Think that is what Widow does on their carbon limbs.
90 is in the limb with fibers running the length of the limb and fibers woven in across the limb at 90 degrees. I am thinking the other is also layed up 90 then cut at a 45 to get the strips and when glued in the limb lay at 45. Pull up1 some pics of a black widow carbon limb and see the 45.
Quote from: Jeff Freeman on March 18, 2023, 12:39:46 PM
I would be interested in trying on the back and belly, no glass on a Longbow. Just for curiosity and looks
You want to be very careful putting carbon on the belly side of a bow limb. You can get away with it on some D shape long bow designs that the over all limb flexes and distributes the load more evenly. And even on some mild R/D long bow designs. Typically uni carbon is used for this on a deep core design.....
But... on hybrid R/D long bows where the working limb is shorter, or on recurve limbs.....The Belly side carbon will often separate and shear the bond. Even using rock hard maple as a belly lam. The stuff doesn't compress, and the maple does.... Then it buckles the carbon after the bond is compromised. and BOOM! Thar she blows mate!.... They are time bombs... Ya never know when they are going to let go...And they always blow after the belly carbon buckles...
On the other hand .....it makes for some great explosive limb failures worth getting on video. :biglaugh:
As far as putting this stuff on the back of a limb with no glass... I think you'd find it will work just fine. I've built bow limbs with 2 layers of stable core alone on the back and it wasn't purdy , but was successful... I don't know whether it would hold up under compression on the belly side though...Never tried that.
I'm going to try this new .019 stuff on the back over stable core for a total of .034 composite backing. I'll bet does well for 35-55# limbs.....
But i'm thinking the lighter weight recurves might get better stability with a slight separation between the carbon and the stable core......I'll try it both ways. Carbon next to the belly under .030 glass, and stable core towards the back. The switch it up on the next lay up...
The reason i think the stability might be better with the carbon towards the belly comes from past experience building single and double carbon bows. If you could put it on the belly itself without building a bomb, THAT will give you serious torsional strength.... But i'm not going back down that expensive rabbit hole again... Been there... done that... Too expensive to be replacing on warranty.... It's not a matter of IF they will blow.... Its just a matter of when... Need glass on the belly for longevity and fine tuning your limbs draw weight and balance... You cant sand that carbon for adjustment. It is... What it is...
Big outfits that mass produce double carbon limbs have to match them up as close as possible, and send them out the door praying they make it until the warranty expires, or the customer hangs it on his wall instead of shooting it a lot... They are all time bombs...
That's about 10 cents worth of my opinion... Take it or leave it...... Kirk
You got to keep the uni off the belly. The only reason I use carbon is for stability Front and belly .020 or the 019 over glass. Thinking Widow uses 6 ply front no glass and 2 ply twill belly no glass. The 6 ply has uni and twill.
Quote from: Crooked Stic on March 21, 2023, 10:05:29 PM
You got to keep the uni off the belly. The only reason I use carbon is for stability Front and belly .020 or the 019 over glass. Thinking Widow uses 6 ply front no glass and 2 ply twill belly no glass. The 6 ply has uni and twill.
So you are saying you use this directly on the belly and back directly over the .040 glass? If so, how do you adjust draw weight , and balance your limbs without sanding? Width profile and trapping only?
If I want the carbon look yes front and back and I put it over .030 core tuff. Only had one recurve had to adjust the tiller and got enough off the corners to take care of it.
If you are going for stability only put it under veneers .⁵
This discussion has me thinking that for stability only, maybe putting the hex close to the neutral plane would be a good choice. I've been putting stabilcore on the belly side. Some say they put it on the back side.
I've a gone from what I've heard. It goes on the back or one under the back. Not the belly, because it doesn't like compression. Unless it's the proper carbon. IDK about the belly. I put some stabil core on the back 🔙 under .030 glass and I did get some better speed. But I also used 1 laminations of syntactic foam. I was to chicken shit to do both laminations. So one was maple on the belly. Now I wished I would have done both foam. And .040 on the belly. It was in the 190s fps. This was on a 62" hybrid. I called it, Project X. JF
Quote from: Longcruise on March 22, 2023, 04:43:33 PM
This discussion has me thinking that for stability only, maybe putting the hex close to the neutral plane would be a good choice. I've been putting stabilcore on the belly side. Some say they put it on the back side.
When I use it, I always put stabilkore in the center of the stack for rotational stability and would do the same with the twill carbon. The center of the limb seems like a good place to minimize rotation. Just what works for me.
My thinking that putting Stabil-kore next to the belly glass or veneer (because It's so flimsy)would work better because you are compressing it. :dunno:
To be truthful I have not seen a case where I thought stablecore has done that much good.
Torsional stability is very difficult to measure from one bow to the next. Where you really start noticing difference is in RC bows under 40 @ 28... under 35 pounds it's even more pronounced as the limbs get thinner at the base of the curl .
For me the thickness that things start getting squirrelly is getting below .190 at the base of the curl. On light weight bows I'll use par lams or even reverse taper to keep that thickness.
I'm hoping this cost effective 45/45 bias will mitigate this. Once you start using a reverse taper, it changes your limb dynamics a lot and it bends closer to the fades....
We shall see.... Kirk
Quote from: Mad Max on March 22, 2023, 06:47:28 PM
My thinking that putting Stabil-kore next to the belly glass or veneer (because It's so flimsy)would work better because you are compressing it. :dunno:
That is my thinking too....and it should be amplified with 45/45 carbon weave. But this China carbon is different material than I've used in the past.
I got a bit more info from the supplier in China regarding this 45/45 bias carbon. There are only two layers of carbon in the .019 thickness. Both being bias. I'm uncertain whether this is a pre preg material or not, but all the lay ups that I had built at CST and other west coast carbon manufacturers used pre preg material and the thickness was about .0065 per layer. So getting a .019 thickness would require 3 layers. I ordered quite a bit of. "XOX" lay up which was 45/uni/45 that measured about .021 . But...... I had a tough time keeping that stuff directly on the belly of a recurve limbs and hybrid limbs both. even used over glass I had shearing issues due to compression.
I won't be using this stuff on the belly surface myself. Not worth the heart break. I'll put it directly under .030 belly glass and see how it does for added stability.
Kirk
:thumbsup:
What exactly is prepeg
Quote from: Crooked Stic on March 27, 2023, 05:16:15 PM
What exactly is prepeg
Here ya go Mike.... This is the most common material used laying up carbon sheets...... the problem is.... Every roll is a wee bit different, and can cause quite a bit of difference in strength.... So unless you are buying large quantities, or the whole roll at a time. Every time you have some made it's a different strength.
The aerospace industry has standards that must be met. But if the material is a bit stronger than the minimum, that's fine.... As bowyers we require more consistency than that to hit our draw weights constantly.
As a custom bowyer buying small quantities of carbon, building just a few sets of carbon limbs here and there is a nightmare. You end up building 2-3 sets for every bow to hit your draw weight perfectly, and hope you can sell the other ones down the road.
I suppose if you are just building bows and selling them as-is , your exact draw weight doesn't bother you much. Build em, mark the weight, and sell the product.
It would sure be a lot easier to do it that way.
https://www.fibreglast.com/category/PrePreg_Fabrics?gclid=CjwKCAjw_YShBhAiEiwAMomsEOidQf0kLQ9NLyVAM-2nEKbin9oHqL18ITFd5BjKBiHVDpQxxtJzkhoCIDIQAvD_BwE
If you are getting the stuff from Mark Tom it is already laid up and shinny both sides and it needs sanding before glue. He said use 180 I used 120 what smooth on recommends. And measured it inseveral spots and was .019.
Here is some interesting carbon weave material info.
Plain Weave. The simplest carbon fiber weave is known as a plain weave. The plain weave is formed by crossing tows in a one-over, one-under pattern, creating the checkerboard seen on many woven fabrics. These materials are strong and highly stable, but they are not very pliable. Plain woven carbon fiber is best for components that are flat or only slightly contoured.
Twill Weave. Like the plain weave, the twill weave comes from passing tows in an even over/under pattern. However, rather than passing over a single tow, each strand passes over multiple tows, then under the same number of tows. This is typically done in a two-over, two-under pattern, but 4 x 4 twills are also common. In either case, the resulting pattern appears to form rows of rectangles proceeding diagonally up the fabric. Twill weaves are more formable than plain weaves, so they can be used with more complex shapes. However, this means that they are not as stiff and stable as plain weaves.
After reading this, it makes me wonder if the compression characteristics are different using this Twill weave, and possibly more user friendly on the belly side of the bow. I've always use the plain bias weave in the past with one layer of uni in the center. XOX = 45/45 / Uni / 45/45 plain weave. One of the better lay ups we used was XOXF with a layer of glass in the matrix assembly. This allowed you to run it through a drum sander to get exact thickness specs and sand the glass.
Just a bit more info on carbon if you are interested. Kirk
https://prepregs.com/prepreg-carbon-fiber/#:~:text=Prepreg%20Carbon%20Fiber%20Applications%20Prepreg%20materials%20are%20easy,and%20resistance%20to%20both%20chemicals%20and%20extreme%20temperatures.
Rosewood has a 6 ply twill that has uni. Pretty sure that is what Widow uses on the front and the two ply twill on the belly. No glass.
That doesn't surprise me that Black Widow would use it belly and back. They stamp out large quantiles of limbs and dont need to sweat actual draw weight on each set they build. Mix and match, and out the door...
Mark Tom got back to me on the product he uses, and it is "pre preg" material. But I haven't got any specifications yet on the carbon weave type... Still fishing for that info... Kirk
T has may be prepeg hen I am confused. The stuff Mark Tom has may be prepend before he lays it up but you have to add glue when you use it.
Quote from: Crooked Stic on March 31, 2023, 11:14:18 AM
T has may be prepeg hen I am confused. The stuff Mark Tom has may be prepend before he lays it up but you have to add glue when you use it.
I think you are miss informed on how pre impregnated carbon lay ups are done Mike.... That is the beauty of this material. It's pre impregnated with epoxy resin and doesn't need any resin while assembled....only needs to be air bagged or pressed and cooked....
Check this out....
https://www.easycomposites.co.uk/learning/introduction-to-out-of-autoclave-prepreg-carbon-fibre
Of course what we get from manufacturers is already cured, and we need to use epoxy to put them together. The pre preg itself could not be used in a bow form easily. The temps needed to cure pre preg carbon exceed our standard 160 degrees by quite a bit, and is cured at higher temps than the fiberglass is.
You could find other videos showing how flat lay ups are done and different curing methods, autoclaves, and ovens used... it's pretty fascinating.... Kirk
Now I am clear. Sometimes$50 words don't Pentwater this brain
Quote from: Crooked Stic on March 31, 2023, 08:02:53 PM
Now I am clear. Sometimes$50 words don't Pentwater this brain
I'm surprised you didn't get into the carbon limb prototype craze that went on in the bowyers gallery on POA years ago Mike. There were several guys on that forum that were seriously well versed on carbon products. Had a few that actually laid up their own sheets with cloth and poured their own micro spheres for foam cores..... That was a talented group of innovative bowyers... it was sad to see it fade away like it did..... but..... there was some wild and crazy guys on that forum too..... Kirk