Primitive Archer
Main Discussion Area => Bows => Topic started by: toomanyknots on November 27, 2010, 01:06:34 pm
-
Ya, before you say no, I made two bows. Both red oak. Same exact dimensions. One unbacked, one backed with linen. The unbacked one came out at 45# at 26". The linen backed came out at 65# at 26". Big difference. I thought that I've read on some threads that linen backing won't affect weight or tiller?
-
Did you check the draw weight before you backed it to see if it actually gained weight? I am not saying it didn't, but the difference may have been in the wood's density or something? I don't know. I have backed bows with linen after I tillered them, and the weight did not change. But that is just my experience.
-
also check the limb thickness with a dial or better yet digital caliper
i'll bet the heavier bow has a little thicker limbs too,especialy if all other demensions are equal
-
Dimensions are exact to a 32nd of an inch. (way it looks on the tape anyway, I don't have access to either a dial or a caliper or I definitely would check it.) I use a jig for consistent thickness and a "jig" of sorts, if you can call it that, for width. Both pieces of wood looked identical, same thickness of rings, same color, exc...
"I have backed bows with linen after I tillered them, and the weight did not change. But that is just my experience."
Ya, I can second that. I just linen backed a "ambush style" bow after tillering, and it did not raise the weight. (I think, it was supposed to come out at 55#, and came out at 55# anyway, but I didn't weight it before I backed it). This time applied the backing before bending it at all. I think that just how the belly is said to compress and get set, and in effect become permanently compressed, I bet you the back of the wood also gets permanently stretched out a bit. So maybe the linen stopped it from stretching, and forced all the bend to be compression, thus raising the weight from forcing the belly to compress more than it would normally?
-
1/32 is over 31 thousandths of an inch which sounds even less critical, but in tillering, each scrape of a good blade takes off just a couple thousandths. And how many of us have had a tiller go off because of just a few too many licks scraping, huh?
Yeah, I use a dial caliper when roughing in the limbs. I hate working with fractions, they make me fractious! I too used to think same dimensions made same draw weight bows, especially when I was working with dimensional hickory lumber. Fact is, some pieces of wood are more dense than others and some pieces even from the same tree are better than others. Every bow is a puzzle unto itself.
The real test is to make the bow, finish it out, check the draw weight, shoot it in for a few hundred arrows, check weight again...and then back it with linen and check your draw weight.
-
As JW said, all it was is the difference in densities of the wood,. Ive mad a lot of red oak bows and found that if you take a heavy thich ringed board and a thin ringed red oak, that is less dense, cut to the same dimensions, when done the thick ringed bow will be heavier everytime. Other species as well. More dense = heavier bows if made correctly.
-
Yep unless you make a bow of a certain weight and THEN back it, it's all speculation....
-
"Yep unless you make a bow of a certain weight and THEN back it, it's all speculation...."
I guess, but isn't 20#s a bit of a big difference for just density? Doesn't it make sence that not allowing the back to stretch would make the belly have to do all the work to bend, compressing the belly more then it normally is, thus making it a heavier bow? I think if I tillered and then backed it it would not have any difference since the back was already stretched out. Since linen is in fact doing like 0% work anyway.
"Ive mad a lot of red oak bows and found that if you take a heavy thich ringed board and a thin ringed red oak, that is less dense, cut to the same dimensions, when done the thick ringed bow will be heavier everytime."
You have got a difference bigger than 5# for the same dimensions? Cause I havent? I sure have not got a 20# difference.
-
"I think if I tillered and then backed it it would have not difference since the back was already stretched out. Since linen is in fact doing like 0% work anyway"
Have you read the TBB's yet? The back is already stretched out? No! The back stretches when the bow is bent. So unless you applied the linen while the bow was at full draw the the linen would still be taking tension forces.
In the 2 different bows you have of the same dimension, where they taken from different boards? There can be density differences, MC differences too. What about ring size? How comparable are they? When you add up density, MC, and the fact that miniscule amounts of thickness variation can affect draw weight it's likely it's not the linen.
Now, that being said I would encourage you to experiement more. But just make sure you stay to the scientific method as much as possible, otherwise any conclusions you make are nebulous at best. I would say make the bows from the same board. Measure MC's and use a digital caliper to ensure thickness measurements are the same. I'm all for you rocking the bow making world and would love to see you change long held assumptions but if that's your goal there must be integrity in testing.
-
"The back is already stretched out? No! The back stretches when the bow is bent."
??? The belly in an all wood bow is not the only place that does work, as you know, so why would it be the only place that takes set. What you under look is that after tillering the back HAS stretched a bit, into "tension" set, as the belly has crushed into "compression" set. Why would you think the back wouldn't stretch?
"Have you read the TBB's yet?"
Yes, but that doesn't have anything to do with what I'm saying. I think you just don't understand what I'm saying.
"There can be density differences, MC differences too. What about ring size? How comparable are they?"
See my second post. Also, can anyone attest to having a bow with the same wood and dimensions come out any different than around 5#s?
"Now, that being said I would encourage you to experiement more. But just make sure you stay to the scientific method as much as possible, otherwise any conclusions you make are nebulous at best. "
lol :) I know, I know, I really just thought this was crazy and should share it with yall. So ther ya go. :)
-
"The belly in an all wood would is not the only place that does work, as you know, so why would it be the onlyplace that takes set. What you under look is that after tillering the back HAS stretched a bit, into "tension" set, as the belly has crushed into "compression" set. Why would you think the back wouldn't stretch?"
Do you build a lot of bows that take a lot of set? Sure the back retains SOME memory. But by your argument if I tiller a bow and THEN back it with a slat of wood without inducing reflex I won't raise draw weight because the back is already stretched. That is what you are essentially saying. That linen adds weight but only on a pretillerd bow. See what I"M saying?
"Yes, but that doesn't have anything to do with what I'm saying. I think you just don't understand what I'm saying."
The TBB's cover everything that you have brought. How wood works and takes strain, how backings affect performance, how recurves work. Unfortunately for a dunce like me it took Many Many Many readings to adbsorb a fraction of the information they contain.
It IS crazy and thank you for sharing. Now we can try to figure out WHY it's doing it.
-
I have made ash bows taken from right next to each other in the tree ,made identical limbs as measured with a digital vernier and had more than 5# difference,I have measured limbs on the same bow with digital calipers extremely accurately to see if I can avoid set and still one limb is well out. Wood is very variable over small distances within one tree, it appears, to me anyway...... I only made one linen backed bow, TBB said it makes bows unbreakable...mine exploded and clean snapped accross the linen back.!!!
-
Wood is a natural material, and 2 staves, even from the same tree, with the same dimensions, will NOT make the same bow. Linen backing, unlike sinew, does not add draw weight. Same as rawhide. It only provides insurance against breaking.
-
How could you know that the DW increase is not the result of glue/back wood composite ::) which could move the normal plane a bit to the back and then you have a bit more belly to do more work.
-
I have had Osage/Hickory and especially Hackberry out of sister stave come out with way different weights at the same dimension's .That is why I always leave them thick when I rough them out before starting the tiller process. Never used Lenin so just guessing,but I would say
no. :)
Pappy
-
@NTD
"The TBB's cover everything that you have brought."
This from volume 4 of the bowyers bible:
"Combed linen will allow the impossible: putting woods back after too much has been removed. A 30lb bow can become a 60
pounder. Not much thickness is needed either. About 1/16" on a typical limb will do."
"Do you build a lot of bows that take a lot of set?"
No, every bow I've ever built has 0 set because I'm perfect. ???
"The TBB's cover everything that you have brought. How wood works and takes strain, how backings affect performance, how recurves work."
I like to talk about things. I also like to think about things. Aside from other things, this can be a good place for people from all over the world to think openly about things. Nothing I have ever posted has ever contradicted anything that of the authors of the bowyers bible has wrote. Yet you still refer me to it like I need to go reread it to "correct" myself or something? Calling my post on paleoplanet dogma was as well disgustingly irritating, as it proved you didn't even take the time to read it before putting me down. I suspect to inflate your own ego regarding knowledge on the subject matter, WITHOUT first acquiring knowledge of the subject matter. Telling me to shut up and be quiet was nice too. If you don't understand something in my post or it is beyond you, then please don't take your frustration out on me, as I have did no such thing to you.
-
I have always assumed, without testing, that adding a layer or two of linen will add a pound or two to draw weight. Regardless, the main reason I back with linen is for insurance. I guess there are a couple variables to consider when using this material; for instance, the amount of glue (usually TB II) and number of layers. A couple years ago when I was making a lot of hickory-backed bows I noticed that on the occasion of a bow breaking it was never at the glue line but rather in the wood. Secondly, I've learned that when I apply linen (or rawhide, silk, etc.) that there is a moisture content in this polymer glue which can be absorbed back into the wood. In addition, because I first soak the linen, or leather, or whatever in water to make it more flexible and pliable, I'm deliberately exposing my dried, seasoned, wooden stave to new moisture. I"m convinced I've had at least one (hickory) bow develop set in a limb after I applied a couple layers of linen and failed to allow the wood to return to a low mc level before starting final tillering.
-
Toomany- Two questions, first being what sort of linen did you use? You mentioned over on PP that you really stretched the backing out before applying. If it's a low stretch material already, it ight have had some effect- kinda like the silk backings people used to talk about. Second question, can we see some pictures :)? Alot of variables and it's easier to show than explain. Not to mention red oak boards are unreliable jerks. But that's just my opinion O:)
-
False dogma, TooMany! You have made several unfounded, untested claims that if gone unanswered pose the chance of becoming the False dogma that was being discussed. You keep bringing up the combed linen ARE YOU USING COMBED LINEN? You are taking my comments from PP entirely out of their context and you know that. It's certainly your right to take offense but none was intended and Tom saw it that way as well. Have a great day TooMany! I'm bowing out.
-
"first being what sort of linen did you use"
Linen fabric from Jo Anns Fabrics.
"Second question, can we see some pictures"
My sd card on my camera is fried, :( sorry, I would love to if it wasn't.
"You have made several unfounded, untested claims that if gone unanswered pose the chance of becoming the False dogma that was being discussed."
Specify.
"You keep bringing up the combed linen ARE YOU USING COMBED LINEN?"
No, I'm pretty sure on the paleoplanet post I made clear it was linen fabric. This is around the tenth time you didn't read what I wrote. I am sure you are only looking for something to prove some point you don't even have.
"False dogma, TooMany! You have made several unfounded, untested claims that if gone unanswered pose the chance of becoming the False dogma that was being discussed."
Thats insane logic. How can a publically open debatable subject be dogma? I explained how backing a bow with a nonworking non stretching material could raise weight. If I made any claim you sure did not challenge it? All you did was call it dogma and tell me to shut up and be quiet, that in no way challenges anything I said. It just starts crap like this. Ironically I was challenging an idea that is very widely held to be true in the online community. I believe that is the definition of dogma. It doesn't matter anymore anyway as I deleted that thread before I got banned from paleoplanet for defending myself from nothing but a "UNFOUNDED CLAIM" about myself.
"Alot of variables and it's easier to show than explain."
True. I agree I would need to cancel out alot of those to be able to make a convincing argument either way. Which has not been done yet. So right now we will have to be satisfied with what we currently know, which is alot... Since saying anything that is not widely accept seems to stir up more than I want to stir up sometimes, I'm gonna stick with the basics:
1) Lets see what is widely accepted about all wood bows and how they work. A typical all wood bow's stress is divided between the back and the belly. The back is under tension and the belly under compression stress. The back stretches and the belly compresses. The most stressed points are the top most part of the back, which is under the most tension, and the top most part of the belly is compressed is under the most compression stress. I mean "top" as the most outside part, stress gradually decreasing until the middle point between the back and the belly is reached.
2) Now lets think about what is widely accepted about backed bows and how they work. It is said that some backings are strong, and some weak. Some backings it is said you cannot use on a compression weak wood, like sinew. As the backing could overpower the belly, hense chrysals. Now why would you get chrysals? If you bent the bow normally without the sinew, it would not of got chyrysals? But because you put the sinew on, it got chyrsals. Now how does that work?
I think from a backing not allowing a bows back to stretch, that all the work in then forced to be done in the form of compression. A bows back does stretch when drawn. If it can't stretch, then that is just the more the belly has crush to bend. Your basically crushing the entire bow. This is why, as tim baker mentioned in preformance and design, flax due to it's resistence to stretching can very easily overpower a bow. Because that is what your doing. Your crushing the entire bow. This makes alot of sense if you think about it. It just appears logical to me that this would raise the weight of a bow, thought I lack the ability to explain why forcing a bow to work only in compression raises the weight. But it does. Although it is slightly crazy NTD that you yell at me about how I need to go read the bowyers bible, and somehow ignore where tim baker in the end of design and preformance revisited volime four, where he talks about backings states exactly what I am saying,...
"Combed Linen will allow the cliched impossible: putting wood back on after too much has been removed. A 30lb bow can become a 60 pounder. Not much thickness is needed either. About 1/16" of combed flax on a typical limb will do."
...Although thats crazy, it is even more crazy that you would up and not even read or try to understand anything in my post and yet still continue with your feeble claims, such as calling my post dogma. Please show me an unfounded claim in my point. Please show me dogma that I posted above me. Show me the dogma above. Show me how some unquestionable, religiously held belief (this is the definition of dogma if you didn't know that) can be drawn forth from an opinion? That logic would be insane.
-
I would agree that simple linen cloth backing where only half the actual fibres are linear is not going to add much if anything to a bows weight.
On the other hand a combed flax backing in any noticeable degree of thickness is essentially going to be like adding a reconstituted bamboo backing. That has to add weight. It's too stiff and dense a material when in a matrix to not do otherwise.
If you added a thin layer of linen phenolic to a bow it will raise the weight and a well laid on Flax backing must do the same since you are basically making phenolic in situ.
-
well i was gonna stay out of this,but you know me and that wouldnt be like me would it >:D
no i aint gonna say any thing negative or the like
what i will say is this
toomanyknots: do you have enough of that same fabric for another bow?if so then i would have to say
make another bow start to finish with out the backing,check the finished draw weight at the finsihed draw length
now after this has been done and recorded,apply the backing to the bow in the same fashion as previously on the other bow.
once the backing is dried recheck the draw weight at the same length and record trhe results.
then you and us will know for sure.
now you said it raised it 20# correct.if this is true can you get me the fabric brand name/style and sku and i will get some from my local Jo Ann fabrics
cause thats a serious increase in weight if its correct.
even if you dant make this bow,give me the fabric info and i will make one anc try it ;)
peace,
tim
-
I have backed several finished bows with linen. The draw weight gain was not all that noticable. Several years ago I used raw flax to add about 15# to a bow and it was thick! The draw weight went up but the performance stayed the same or went down, it was a real dog. Steve
-
Sailorday brings us back to heart of scientific discovery....duplication of results. There will always be exceptions and erratic results, but if it can be duplicated then it can be proven.
-
Scott, logic seems to suggest that by further twisting and tightening the cable would increase the weight and the cast. I plan on finding out this winter by making one with artifical sinew. Have you seen this web-site?
www.primitiveways.com/cordage_backed_bow.html
-
The article by Callahan mentioned documents a radical increase in cast after adding the backing cordage.
-
There was a young man from California that used to come here about 10 years ago. He made a cable backed bow using Linen for the cable, I think he used Hickory for the bow. Can't remember his name but his dad used to build bows as well and his name was Mark, the name might come to me yet. From what I remember he used small blocks to raise the cable off the back of the bow and this method would raise the draw weight considerably