I've been thinking of building an ASL. I have a couple questions.
I see there is a trend to adding a fiberglass laminate inside the bow. I'm not looking for a debate as to where in the stack, because from what I have read, there are different opinions.
When estimating the stack height, is the thickness of the fiberglass treated as if it were just like a wood lamination? Should the fiberglass be tapered?
Is the addition of the fiberglass lam just a consideration for flat bamboo, or should it also be considered if using hardwoods or for actionboo?
Keith
I'm confused. Are you talking about adding a fiberglass lamp to the inner core of an otherwise all wood bow or a typical fiberglass wood core bow?
Not a self bow. Typical ASL with at least 2 or 3 wood or boo laminations. Back, Belly fiberglass at 0.050.
If you are making a laminated bow, from what I know there would be no advantage to putting.050 anywhere in the stack other than the back to strengthen a wood or the belly of a compression weak wood. But in doing either you have to be careful not to overpower the opposite side.
I don't know if .050 of fiberglass in the center of the stack would act any differently than .050 of wood. I definitely wouldn't bother tapering it, as tapering ghe wood around it seems like it would have more of a reaction.
I have no experience with this though. The only time I've tried putting glass in the middle of a limb was at the tips to try to make static but maple seemed to work better and was lighter.
This is what I'm asking about:
https://sunsethilllongbowsandleather.blogspot.com/2024/05/the-core-glasswhy-secrecy.html
Keith
Im sure kirkl will jump in here soon if he reads that.
From what I understand from that article the glass is supposed to help with the sheer? To my knowledge(not very vast and often flawed) the neutral planein the center of the limb would have the least amount of sheer right where you would be putting the glass and now there are 2 sheer lines, one on each side of the glass. Additionally you have moved those sheer lines .025 off of limb center where there is the least sheer to an area where there is more sheer force? Another thing to consider is the sheer line is now up against fiberglass(stronger than the wood it would have been up against, so not sure it that would make it harder on the softer wood or not, but seems like 2 softer materials might share the load better than a really strong and weaker material.
As far as stability goes, I hear the best place to put it for stability is as close to the back as possible.
I think your initial question was do you treat it like wood for stack count? If it were me and I was putting it in the center of the limb in the neutral plane, I would. Would I taper it? I wouldn't bother, especially if you are hoping it will add stability at the tips no point making it thinner there. Just my opinion.
Quote from: Watsonjay on July 02, 2026, 11:15:44 PMTo my knowledge(not very vast and often flawed) the neutral planein the center of the limb would have the least amount of sheer
Just the opposite, the neutral plane has the highest shear force and it tapers to zero at the back and belly surfaces. The tension and compression forces are maximum at the back/belly surfaces and taper to zero on the neutral plane.
I just skimmed that novel about putting glass in the centre of the limb stack, but the only thing it would add is some torsional stability and a bunch of weight. It's not a good use of a FG lam at all, IMO.
Mark
If you read that article closely he is talking about a glass backing and no glass on the belly. He uses that core glass to mitigate bamboo compression on the belly side.
In that type of construction I can definitely see an advantage. Bamboo sucks in compression properties.
But.... And it's a big BUTT. We are talking about an ASL design here. There are no stability issues with that design unless you ran an .006 FT and developed a whippy tip.
If You are talking about using glass belly and back on your bow. There is absolutely no advantage to using glass in the core... period... it adds mass weight to a limb design that is typically known for very low preload anyway unless you are using a serious amount of reflex in the form, and a you won't ever get high performance out of those designs until you start getting up around 70#.... Not enough tension on the string to stop the limbs forward travel, and very poor energy transfer to the arrow. The higher draw weights have higher preload, and better performance.
The only time adding glass or composite material to the core is advantageous is in a hybrid design R/d or a recurve limb for stability reasons. And when doing so you would use very thin products like stable core, uniweft, or better yet a bias weave carbon.
The only thing good about that article I can see is that you could print it out and use it to start a fire.
This article really confuses me. He's called glass glass backing and core glass. He says he's trying to replicate a glassed back "feel" and he's controlling where the compression and tension sheer lines are so I dont think he is just backing a bamboo bow? I know Im slow. Sorry
"By adding a core glass to my limb, I am specifically placing the shear forces between tension/stretching and compression exactly where I want them"
Picture pulled from the wall, so what is this strip in between the 1st and 3rd laminate in the new Howard Hill bows?
And another.
Quote from: Kudu Kid on July 03, 2026, 12:47:53 PMAnd another.
Thank you picture helps a lot. So Im guessing yew on belly, then glass, then bamboo, then Ipe?
So from what I've now been told the highest sheer are is in the middle of the limb at the neutral plane. The bamboo glue line isnt near the center so there shouldn't be too much sheer stress but adding the .050 glass and removing.050 of bamboo to compensate would move the sheer line .050 further from the highest stressed area of the neutral plane. Is that the intent of this process or is it to add durability and not show the glass? Seems like you could just use the glass, get rid of the bamboo and put whatever that cover wood is over it, ipe?
If it is, would the 050 glass have way better tension strength than the bamboo? Would you have to remove even more bamboo than the .050 to compensate for the extra strength of glass over bamboo. Brain melt!!! Wasn't that the original question. I think I finally understood the original question!!! But do you really even need the glass with the bamboo so far the neutral and sandwiched between that and 2 woods with 2 glue lines
I have no idea what the thickness of the lam of glass is or should be. I am most likely overthinking it. I just read that the bamboo is not what it used to be, thus the need for the extra "help".
I made a couple laminated bows many moons ago and I don't even have them anymore. I have made plenty of self bows, just thought I would try making a nice laminated longbow again.
Nate Steen references Donato Milese in his blog. He is a bowyer in Italy that is committed to building the Hill style bow. He also puts a thin strip of glass in the middle of his stack.
I can see how adding it to the back would possibly give more snap than bamboo, I just dont understand why you would use bamboo too when you have another wood over it. Additionally it seens like you would want it as close to the back as possible with a very thin layer of strong wood to hide it. Can someone explain why you would still put bamboo over it. Just trying to learn not criticism at all. Thank you.
Kirk: "If you read that article closely he is talking about a glass backing and no glass on the belly. He uses that core glass to mitigate bamboo compression on the belly side.
Yes, he does say that as such.
He says: "Well, in today's world of lesser quality bamboo, it helps in an all-bamboo non-glass belly bow to keep the bamboo from collapsing, folding and developing a hinge. But that's not why I do it."
I'm not sure what he might mean by that. It's nonsensical as written. Who is making glass backed bows with no glass on the belly 🤔??? It's a formula for a broken bow. I knew a guy who was trying repeatedly to build board bows with glass backing. They all broke very fast.
I'm sure he is not building glass backed bows with no glass on the belly. And he says "thats not why I do it".
But, IMO his reasons for putting glass down the center to protect the neutral plane from sheer forces don't make sense either. He is correct about the ASL style experiencing stress at the fades but I don't see a center strip of glass being a good solution. He mentions some bowyers using "shims" at the fades and I think he's referring to a power lam which I found is the best solution to fades stress. When coupled with a tip wedge it allows using less forward taper in the overall core and let's the mid area do more work. It also helps prevent excessive string follow.
As Kirk said, throwing a strip of glass into the wood core is just going to add weight. It seems like an answer looking for a question.
That black line in the HHA bow might be stabilcore.
Quote from: Longcruise on July 03, 2026, 02:56:21 PMKirk: "If you read that article closely he is talking about a glass backing and no glass on the belly. He uses that core glass to mitigate bamboo compression on the belly side.
Yes, he does say that as such.
He says: "Well, in today's world of lesser quality bamboo, it helps in an all-bamboo non-glass belly bow to keep the bamboo from collapsing, folding and developing a hinge. But that's not why I do it."
I'm not sure what he might mean by that. It's nonsensical as written. Who is making glass backed bows with no glass on the belly 🤔??? It's a formula for a broken bow. I knew a guy who was trying repeatedly to build board bows with glass backing. They all broke very fast.
I'm sure he is not building glass backed bows with no glass on the belly. And he says "thats not why I do it".
But, IMO his reasons for putting glass down the center to protect the neutral plane from sheer forces don't make sense either. He is correct about the ASL style experiencing stress at the fades but I don't see a center strip of glass being a good solution. He mentions some bowyers using "shims" at the fades and I think he's referring to a power lam which I found is the best solution to fades stress. When coupled with a tip wedge it allows using less forward taper in the overall core and let's the mid area do more work. It also helps prevent excessive string follow.
As Kirk said, throwing a strip of glass into the wood core is just going to add weight. It seems like an answer looking for a question.
That black line in the HHA bow might be stabilcore.
It very well could be stabilcore then instead of fiberglass. So back to my original question, how do you figure this into the stack height?
Quote from: Kudu Kid on July 03, 2026, 04:23:23 PMQuote from: Longcruise on July 03, 2026, 02:56:21 PMKirk: "If you read that article closely he is talking about a glass backing and no glass on the belly. He uses that core glass to mitigate bamboo compression on the belly side.
Yes, he does say that as such.
He says: "Well, in today's world of lesser quality bamboo, it helps in an all-bamboo non-glass belly bow to keep the bamboo from collapsing, folding and developing a hinge. But that's not why I do it."
I'm not sure what he might mean by that. It's nonsensical as written. Who is making glass backed bows with no glass on the belly 🤔??? It's a formula for a broken bow. I knew a guy who was trying repeatedly to build board bows with glass backing. They all broke very fast.
I'm sure he is not building glass backed bows with no glass on the belly. And he says "thats not why I do it".
But, IMO his reasons for putting glass down the center to protect the neutral plane from sheer forces don't make sense either. He is correct about the ASL style experiencing stress at the fades but I don't see a center strip of glass being a good solution. He mentions some bowyers using "shims" at the fades and I think he's referring to a power lam which I found is the best solution to fades stress. When coupled with a tip wedge it allows using less forward taper in the overall core and let's the mid area do more work. It also helps prevent excessive string follow.
As Kirk said, throwing a strip of glass into the wood core is just going to add weight. It seems like an answer looking for a question.
That black line in the HHA bow might be stabilcore.
It very well could be stabilcore then instead of fiberglass. So back to my original question, how do you figure this into the stack height?
Im getting ready to experiment with a limb design and will be using stabilcore and am just going to figure it jn like normal wood. It is pretty thin like 015.
To answer your original question. If you decide to use glass in the core your stack height will not change with glass also running belly and back.
Stable core IS glass. It's a 45/45 woven glass that runs about .015 in thickness.
Why run .050 glass belly and back? Are you building 80# plus limbs? You are fine with .040 glass up to 70#. Over that is where I switch to .050.
Yup... the fade shims = power lams. But most guys do not run those up the belly ramps. I run mine on the back of a 20" riser, and the total length of the power lam is 30".
But I don't build those straight profile spears when unstrung. My ASL has about 3" of back set and weren't popular with the HH club members. Mine do not have any hand shock and shoot the arrows too fast. They like their spears.
Quote from: Watsonjay on July 03, 2026, 01:31:59 PMIf it is, would the 050 glass have way better tension strength than the bamboo?
Yes, FG is much stronger and stiffer than bamboo in both tension and compression.
Quote from: Watsonjay on July 03, 2026, 01:31:59 PMBut do you really even need the glass with the bamboo so far the neutral and sandwiched between that and 2 woods with 2 glue lines
I don't understand your concern about the glue lines. Properly glued they are as strong as the wood they are glued to and will not cause any problems.
Quote from: Kirkll on July 03, 2026, 10:59:22 AMIf you read that article closely he is talking about a glass backing and no glass on the belly. He uses that core glass to mitigate bamboo compression on the belly side.
That seems an extremely inefficient way to make a bow limb. Assuming you wanted decent performance out of it, anyway.
Mark
" That seems an extremely inefficient way to make a bow limb. Assuming you wanted decent performance out of it, anyway."
Getting Decent performance in that type of design is tough to do with no back set or reflex in the bow. But... with the use of long power lams, tip wedges, and the right taper rates it can be improved a lot.
Quote from: Kirkll on July 04, 2026, 12:11:03 PMGetting Decent performance in that type of design is tough to do with no back set or reflex in the bow. But... with the use of long power lams, tip wedges, and the right taper rates it can be improved a lot.
I'm not talking about the ASL design itself, I was talking about putting a glass lam mid stack instead of on the outer surfaces of the limb. The ASL is what it is in terms of performance, this is just making it worse than it needs to be.
Mark
Quote from: mmattockx on July 05, 2026, 09:34:30 AMQuote from: Kirkll on July 04, 2026, 12:11:03 PMGetting Decent performance in that type of design is tough to do with no back set or reflex in the bow. But... with the use of long power lams, tip wedges, and the right taper rates it can be improved a lot.
I'm not talking about the ASL design itself, I was talking about putting a glass lam mid stack instead of on the outer surfaces of the limb. The ASL is what it is in terms of performance, this is just making it worse than it needs to be.
Mark
Yup....kinda like putting lipstick on a pig.
well, a customer lately showed me his glass backed all bamboo bow :biglaugh: with a thgin strip of carbon towards the belly. well, that of course does not make a lot of sense imho, it has nothing to do with the original all bamboo bow, its a glass backed and carbon bellied bow with a useless strip of bamboo on the belly,.....
I still dont see the benefit
The benefit to having glass under the wood belly is to minimize set-that's all- I build quite a few bows like this
Quote from: Stagmitis on July 14, 2026, 06:27:21 PMThe benefit to having glass under the wood belly is to minimize set-that's all- I build quite a few bows like this
Now that right there makes sense to me... :thumbsup:
Not say that doesn't work, but it still doesn't make sense to me. The wood on the belly side of the glass still has to compress just as much as it is still bending as much, so would the cells of the wood still remember that compression and have set? Can someone please dumb it down for me how this functions. Seems as if the glass were on the outside it would work. Sorry for my slowness.
Quote from: Watsonjay on July 15, 2026, 08:51:39 AMNot say that doesn't work, but it still doesn't make sense to me. The wood on the belly side of the glass still has to compress just as much as it is still bending as much, so would the cells of the wood still remember that compression and have set? Can someone please dumb it down for me how this functions. Seems as if the glass were on the outside it would work. Sorry for my slowness.
You are correct. Having a FG lam under the wood belly lam will help reduce set, but it's far more efficient to just put the FG on the belly in the first place.
Mark
Mark when you get close to the performance of an all glass bow with the look and beauty of a Selfbow I think it's pretty cool. Clear glass over a wood belly doesn't come close and you lose speed with clear anyway 😎
WatsonJ I hear you:)
I'm not an engineer and can't explain it either-but having built many with the glass under the belly and without I can tell you I would not have reached speeds in the low 170's without it.