Post by: kennym on February 09, 2025, 06:22:35 PM
You like to sand back or belly or both ?
Post by: Crooked Stic on February 09, 2025, 06:47:11 PM
Post by: kennym on February 09, 2025, 07:14:53 PM
My stack math must suck lately... :biglaugh:
Post by: Crooked Stic on February 09, 2025, 07:54:25 PM
Post by: Kirkll on February 09, 2025, 11:20:56 PM
I’ve taken as much as 12 pounds off limbs before and they lasted many years. I’ve got a bow I’ve used personally for almost 15 years that I put .022 clear glass over . 012 veneers , over carbon that is still going strong and I bet I have 30,000 arrows through that 57 bow….
Btw…. Don’t be afraid to narrow up a width profile. Even on a recurve design you would be surprised how narrow you can make these and still maintain stability if your design isn’t too radical. Your limb shape and limb thickness is what determines stability. Not width….On light weight glass limb bows, use a parallel lam, or even a reverse taper to keep the thickness at the base of the curl. Either that or use a bias weave carbon on the back to help hold it straight.
I regularly use 80 grit to tiller my bows and Lower draw weight to within a couple pounds of target wt. Then finish sand them…. I sand both belly and back evenly myself. I try and hit draw weight about 5 pounds over target weight on rough profile draw check.
Now heavy draw weight bows over 60-70 # I use thicker glass, but using .040 glass in the 60-70 # range I limit the sanding to minimal tillering adjustments.
Post by: kennym on February 21, 2025, 08:41:18 PM
I slowly and carefully got her down to my target weight . She pretty quick too for 44@28
Post by: Roy from Pa on February 22, 2025, 02:30:08 PM
Post by: Watsonjay on February 22, 2025, 02:33:00 PM
Post by: kennym on February 22, 2025, 03:17:03 PM
Didn't happen wifout pichers....
Ain't got no finish on it or even done finish sanding... :biglaugh:
Post by: Roy from Pa on February 22, 2025, 03:25:06 PM
Didn't happen wifout pichers....
Ain't got no finish on it or even done finish sanding... :biglaugh:
So what's yer point Spanky?:)
Post by: Watsonjay on February 22, 2025, 03:40:09 PM
Post by: kennym on February 22, 2025, 04:31:50 PM
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Post by: Watsonjay on February 22, 2025, 05:00:34 PM
This all ya get for now :biglaugh:that is pretty!!!
Post by: mmattockx on February 22, 2025, 07:17:19 PM
In some of the reading I’ve done it said glass was better at tension than compression, so if im not trapping I usually start on the back. Im here to learn if Im doing it wrong though.
Almost every material we use is better in tension than compression and fibreglass is no exception. Trapping the back and/or sanding the back glass first is the best way to go if you don't want to narrow the whole limb like Kirk was suggesting.
Mark
Post by: Joni on February 28, 2025, 12:44:33 PM
How much you can safely sand glass depends on the draw weight and limb design. It’s actually a lot more than you would think. A 50# bow will hold up fine with .030 glass belly and back. So if you are using .040 glass you could sand as much as .010 belly and back if you are accurately doing it.
I’ve taken as much as 12 pounds off limbs before and they lasted many years. I’ve got a bow I’ve used personally for almost 15 years that I put .022 clear glass over . 012 veneers , over carbon that is still going strong and I bet I have 30,000 arrows through that 57 bow….
Btw…. Don’t be afraid to narrow up a width profile. Even on a recurve design you would be surprised how narrow you can make these and still maintain stability if your design isn’t too radical. Your limb shape and limb thickness is what determines stability. Not width….On light weight glass limb bows, use a parallel lam, or even a reverse taper to keep the thickness at the base of the curl. Either that or use a bias weave carbon on the back to help hold it straight.
I regularly use 80 grit to tiller my bows and Lower draw weight to within a couple pounds of target wt. Then finish sand them…. I sand both belly and back evenly myself. I try and hit draw weight about 5 pounds over target weight on rough profile draw check.
Now heavy draw weight bows over 60-70 # I use thicker glass, but using .040 glass in the 60-70 # range I limit the sanding to minimal tillering adjustments.
Thanks for the info! I´ll try this later.
Post by: kennym on February 28, 2025, 12:52:24 PM
Post by: Kirkll on February 28, 2025, 08:18:06 PM
Update on the Phoenix (rebuilt repeatedly) , she done and shoots great, made weight I was after but had to let my hair grow out so I could pull it out... :laughing:
Isn't that something.... Sometimes these just go smooth as silk and you walk right through it. Other times the damn things fight you every inch of the way.
I had a bow i built with an English walnut riser and an I-beam that came out beautiful. but i had a lot of micro checks in that wood for some reason. I'd get everything filled and sealed up looking good, spray the finish, Then find another micro crack or check.... I sprayed that riser 4 times before i finally got a decent finished product....Dad burn thing kicked my arse! :banghead: :banghead: :banghead:
So i can relate Kenny.... Sometimes you get da lion.... Sometimes da lion get you... I had teeth marks all over my arse on that bow.... :dunno: :dunno: :o :o
Post by: mmattockx on February 28, 2025, 11:02:01 PM
Update on the Phoenix (rebuilt repeatedly) , she done and shoots great, made weight I was after but had to let my hair grow out so I could pull it out... :laughing:
Good news. Now where are the full pics?
Mark
Post by: Crooked Stic on February 28, 2025, 11:04:05 PM
Post by: Roy from Pa on March 01, 2025, 07:27:27 AM
Post by: Stagmitis on March 01, 2025, 07:38:33 AM
Post by: Crooked Stic on March 01, 2025, 12:55:48 PM
Post by: Kirkll on March 01, 2025, 11:30:06 PM
Post by: onetone on March 03, 2025, 11:06:33 PM
Vegh Sipahi Test 03 in the Search box.
http://www.youtube.com/watch?v=bz-at6YluwM
Post by: Kirkll on March 04, 2025, 12:17:39 PM
Can’t get the link to work. This short video is instructive regarding how narrow limbs can be and remain stable, which glass, belly or back is most likely to fail, etc. Go to YT and enter:
Vegh Sipahi Test 03 in the Search box.
http://www.youtube.com/watch?v=bz-at6YluwM
What's your point here? All that shows is a guy bending and twisting a light weight glass limb until it failed.
Post by: onetone on March 09, 2025, 11:39:27 PM
The bow in the demo is a glass/wood laminate. There was mention made in this thread that limbs can be made quite narrow and remain stable. This bow is a good example of that, in that the limbs are about 1 - 1 1/8" wide, yet it will be stable when braced, even with the significant reflex and the resultant preload, built into the design.
It is interesting that the failure in the glass laminate occurred on the back of the bow and not the belly, when it was catastrophically stressed. I have heard it said that the compression loads are greater in a bow limb than are the tension forces, yet it was the back that failed.
Maybe an engineer in trad gang can offer some insight?
Post by: Kirkll on March 10, 2025, 10:36:10 AM
The amazing thing is that even with those Scylla overlays on the tips, that they perform as well as they do with so much tip weight. The working portion of the limbs come right off the fades and seem to use a reverse taper.
Theoretically… you shouldn’t be able to even keep a string on one of these things… it just blows my mind….
I think there are a few bowyers that have sucsessfully built these Asian designs that are members here. Maybe they could explain the dynamics on how it works…. Not this kid….. Kirk
Post by: mmattockx on March 10, 2025, 10:40:28 AM
It is interesting that the failure in the glass laminate occurred on the back of the bow and not the belly, when it was catastrophically stressed. I have heard it said that the compression loads are greater in a bow limb than are the tension forces, yet it was the back that failed.
Maybe an engineer in trad gang can offer some insight?
I noticed the back lam peeling apart as well. The forces on the tension and compression sides are always the same, as they have to balance. Assuming you have a rectangular limb cross section (ie - not trapped in any way) the stresses are also the same in the lams on both the back and belly. What normally happens is the compression side fails first by buckling when the core material and/or adhesive can no longer hold the belly lam in place and it pulls away from the core.
I can't say why the back failed first in this case, but I can say that isn't a narrow limb in my world. Narrow is defined by the width:thickness ratio and that limb looked to have a ratio similar to most typical recurve limbs. It is possible that the back failed first because the thin limb allowed a massive deflection without overloading the core materials, but that is speculation. I can say that the beam equations used to define bending stresses and strains stop being valid at extremely high deflections, so that may be the story in this case.
If you want to see what I would define as a 'narrow' limb, look at Howard Hill style bows or English long bows where the thickness is often half the width or more.
Mark
Post by: Kirkll on March 10, 2025, 11:03:24 AM
But the Asian designs that have a huge amount of reflex in the unstrung profile are the ones that mystify me how they can remain stable. Some of those horn bows are a complete circle unstrung, and just stringing them up without them twisting blows my mind….. look at some of those horse bows they used centuries ago….
Kirk
Post by: onetone on March 10, 2025, 12:37:57 PM
I have learned through experience that the brace height is critical to the longitudinal stability of these bows. Set too low and one of the limbs will collapse against the string when shot. Set too high and of course arrow speed drops off.
Post by: mmattockx on March 10, 2025, 04:04:03 PM
But the Asian designs that have a huge amount of reflex in the unstrung profile are the ones that mystify me how they can remain stable. Some of those horn bows are a complete circle unstrung, and just stringing them up without them twisting blows my mind….. look at some of those horse bows they used centuries ago….
Yes, they seem sketchy in the extreme. I know how people string them now but it seems unlikely that ancient archers carried around a peg board just to get the string on their bow every morning.
Mark
Post by: Buemaker on March 10, 2025, 05:35:05 PM
Post by: Buemaker on March 10, 2025, 06:28:13 PM