Primitive Archer
Main Discussion Area => Horn Bows => Topic started by: BowEd on March 18, 2017, 10:45:52 am
-
Making another composite bow here.Going with less thickness of a core by 1/16" and more composites.Increasing the composites thicknesses.Thickness wise the dimensions of bow are all the same as the thicker core bow in the end yet.Close to same profile and length too.Same overall mass weight too.I'm wondering and will find out soon too after sinew cures how much overall poundage difference there might be between the two.With the wooden core being the stiffest component on a horn bow,and the horn and sinew being more elastic.Wonder what the difference if any the final result will be.Might be a pretty vague question to ask but just wondering if there are any thoughts about this out there.I'm using the same .70 density core material too.
I figure it to be a little more elastic.Maybe not as much poundage.If not I intend to just add more sinew.There's always that option I figure.I guess in a nut shell I'm asking how much value does a thicker core have in the poundage of a horn bow?Also does a more dense core if it is elastic enough to seem stronger?Wondering about durability here also.Even though it is in the neutral plane.
-
If the bow is the same thickness, but greater ratio of composite material to wood, than theoretically it would be less poundage since the Sinew and Horn tend to be less stiff. but they are more elastic so it should be able to bend further and handle stress better. If it was already well within its limits then i would keep more wood. If you wanted higher poundage plus good stress capabilities maybe you should keep the same wood thickness but also inceease the amount of composite material, thus making it thicker than before.
-
I have never made a composite bow but enjoy other peoples builds and working to build one at some point but I enjoy Adams book so I was doing a little reading & here is my my interpretation for what it's worth & somebody can correct me if I'm wrong but isn't the core material pretty much along the neutral plane and the vast majority of the tention & compretion work is handled by the horn & sinew so just Ruffly thinking wouldn't it actualy bee more poundage with the increase in horn/sinew I'm sure there is a better exsplanation but sence you brought it up it will be a good opportunity to learn !
-
Good opposing analogies.Making bows sometimes goes against logic.I'l let it cure to find out.Thanks for the opinions.
-
My understanding is that the thicker core material is what gives you additional draw weight. Even though it is in that neutral plane, it still gives you the thickness required for a high draw weight
-
Yes you may be right.You've been reading the new book you acquired Aaron?
-
Not yet, but I've still been doing some homework. ;) There's a composite in my future, just gotta get ready first
-
Cool!!!Look forward to it.
-
Now if you put Antler or Bone on the belly it should increase with poundge. Its stiffness is around 18 Gpa which is higher than most woods (surprisingly most Ipe is stiffer than most Bone) than it should increase the poundage for the same thickness. However, Bone/Antler isn't nearly as elastic as horn but it should be more elastic than most woods.
This is all theory, as i've never tried it myself. Redhand has built some antler bows and is doing a build along now. It sure is interesting and I would love to see more people test this out.
-
Here's some eye pics of project.I'll post a different thread when finished.Pictures of the increased reflex as it goes.Goal with this one is to hit my draw weight at 28" maybe 29" after curing with very little tillering done.I'm sure some tweaking here and there will be required yet though.First after the horn was applied.
(http://i920.photobucket.com/albums/ad41/Beadman1/DSCN1496_zps2q2wg0po.jpg) (http://s920.photobucket.com/user/Beadman1/media/DSCN1496_zps2q2wg0po.jpg.html)
(http://i920.photobucket.com/albums/ad41/Beadman1/DSCN1493_zpsqjcgmqyc.jpg) (http://s920.photobucket.com/user/Beadman1/media/DSCN1493_zpsqjcgmqyc.jpg.html)
First sinewing done Feb.24,2017/390 grains
(http://i920.photobucket.com/albums/ad41/Beadman1/DSCN1505_zpslepyidzm.jpg) (http://s920.photobucket.com/user/Beadman1/media/DSCN1505_zpslepyidzm.jpg.html)
3 days later 2nd sinewing/565 grains
(http://i920.photobucket.com/albums/ad41/Beadman1/DSCN1512_zps0e5hqvko.jpg) (http://s920.photobucket.com/user/Beadman1/media/DSCN1512_zps0e5hqvko.jpg.html)
Around a week later the 3rd sinewing/around 200 grains
(http://i920.photobucket.com/albums/ad41/Beadman1/DSCN1531_zpsdlsf8an0.jpg) (http://s920.photobucket.com/user/Beadman1/media/DSCN1531_zpsdlsf8an0.jpg.html)
Around a week later the string removed for a bit already.I've noticed the sinew is able to pull on this one easier with the thinner core and a hint as to whether it will be the same draw weight.The sinew is soft yet though really and not cured.
(http://i920.photobucket.com/albums/ad41/Beadman1/DSCN1536_zpsv8qvchsx.jpg) (http://s920.photobucket.com/user/Beadman1/media/DSCN1536_zpsv8qvchsx.jpg.html)
A look at the back
(http://i920.photobucket.com/albums/ad41/Beadman1/DSCN1540_zpssefyb6zi.jpg) (http://s920.photobucket.com/user/Beadman1/media/DSCN1540_zpssefyb6zi.jpg.html)
Since I've put the stringer back on to fully cure.It's been a total of just over 3 weeks from first sinewing now.It's very smooth.Could of sized it once to show better[not a very good pic] but it looks like one matrix of sinew and glue already.The strands are'nt very distinguishable looking at it.
-
Yes gfugal I think you are right.Bone and antler are stiffer but not as elastic though.Denser wood can be used too but not as elastic again.
-
Hey Ed sense you used the same core wood on both and I know you didn't tiller the core but what wood your ruff guess be on the core only draw weight differences between the 2 I'm just curious I know it's not scientific but you have a good feel for weight ?
-
Very cool Ed, what is the core wood? Did you groove the horn and core before glue up? What glue did you use?
-
That's some crazy reflex you have there :o. I hope it strings good for you. It should bend pretty good if it has that much composite material. What draw are you going for?
-
Ritch....Actually I tillered the core to brace...that's it... like the other.I want a nice even bend reflected when reverse bracing.The actual draw weight I could not say.It was'nt much that's for sure.Under 20#'s I'm sure @ 28".A hint of poundage would be to say it was 5/16" at the fade thickness and tapered from there.1/4" mid limb and so on.The previous one was 1/16" thicker overall and probably come closer to a 20# bow at 28".
Aaron H....The core is hickory again.Shagbark.Very thin ringed.No I did not groove the core or the horn on this one.To glue the horn onto the core I used smooth on epoxy...I know I know not hide glue???It can be used of course.Smooth on is not given it's proper due far as I'm concerned as far as taking a bend if put on thin enough but not dry jointed.Others have used it too in these profiles.Plus it cures within 24 hours too and is virtually bullet proof to enviornmental influences.It can be done also according to the directions on the can to be more heat resistant too.2 partsA to 1 partB then heat cured 2 hours@ 250 degrees will withstand temps up to 217 degrees F.The rest of the bow is sinew and hide glue.A pic as to how I applied the horn to core.
(http://i920.photobucket.com/albums/ad41/Beadman1/DSCN1492_zpsvglsmkzn.jpg) (http://s920.photobucket.com/user/Beadman1/media/DSCN1492_zpsvglsmkzn.jpg.html)
The horn is tapered first before glueing up.I then heat bend the horn first to fit right up the fades to the belly of the handle first using a traced out profile of the curve transferred to a piece of pine.C clamped first then inner tube wrapped the rest of the way.It's best to wrap the bow with saran wrap first before wrapping with the inner tube to save your inner tube wrapping.I'm told and believe it to be true putting the horn on in a fairly flat profile especially these longer working limbs.Each limb might have around 14" working limb.So that the sheer forces are lateral along the limb.Reducing chances of delamination.These things I take their word for and sorta understand and so far nothing has come apart.
This bow is not going to be under the stress of reflex that a Turkish horn bow would be either but in the past I've tested these to be right up there performance wise.
-
gfugal.....I actually fibbed a little in my opening paragraph.This bow is 2" shorter than the one before.Soooo I figured it to be 5#'s stronger then too at 28".Thus probably equalizing itself out in draw weight to the previous one at the same thickness.
Your right though there is no reason why a good compression strong wood could'nt be used here.Personally I'd go with osage.I know more bout that wood then ipe.I've heard you've got to almost have a perfect piece of ipe..no pins etc. to hold up.Osage is much more versatile or forgiving to me.
-
Here's a pic of tip alignment.I adjusted this while tillering it to brace first so I did'nt need to fuss with that while tillering but still may need a tweak or so we'll see.
(http://i920.photobucket.com/albums/ad41/Beadman1/DSCN1537_zpsdkfve3nc.jpg) (http://s920.photobucket.com/user/Beadman1/media/DSCN1537_zpsdkfve3nc.jpg.html)
-
I'll get a string on her gfugal.....lol.
-
That's a sharp looking bow Ed. I have one in my future but....
Do you think the extra physical weight of the thicker composite components will negate any of the potential benefits.
-
Nope.If made right what your questioning is pretty much a myth.
-
Interesting to hear others thoughts on the subject but all that determines poundage is the overall thickness. The varying ratios of the three materials would change things very little. However it would be a bad idea to go too thin on the wood as that is what gives the bow its shape and lateral rigidity. The ideal is to have the total thickness evenly divided by the three materials to make best use of their different properties.
-
Interesting to hear others thoughts on the subject but all that determines poundage is the overall thickness. The varying ratios of the three materials would change things very little. However it would be a bad idea to go too thin on the wood as that is what gives the bow its shape and lateral rigidity. The ideal is to have the total thickness evenly divided by the three materials to make best use of their different properties.
My thoughts too. poundage doesn't come from the core, but from the distance the working portions (sinew back and horn belly) are from the neutral plane, hence thickness. If the core is too thick (strain>1.5% - the backing does hold down splinters so it tolerates higher strain than unbacked bows), it will break just like a normal bow, no matter how much sinew and horn you have. If it's too thin, it will tend to twist when put under high strain.
You could add some sinew to increase thickness and hence poundage, but in the end you might end up with a sluggish bow as the first 2 layers of sinew are close to being dead but heavy mass.
It's good to experiment and question existing designs. However, most of the time there's a good reason for a particular design.
-
Thanks for the answer Mike I couldn't wrap my brain around the ratio vs strength but it makes sense for draw weight I was confusing weight vs performance which would be another whole thread but a interesting one thanks for posting learning a lot here Ed ! (=)
-
Thanks fellas.Great comments.Overall thickness/staying within the design....that all makes sense for ease of final tillering.Too much horn makes it more unstable or a bit wonky I call it.Can only imagine at the moment what it's like making an all horn/horn sinew bow.This current bow is close to the 1/3,1/3,1/3 ratio yet of components with the core being a shade more ratio wise.Overall thickness is the same as previous bow but like said 2" shorter overall.Overall mass comparing to the last one is the same too but like said again can depend a lot on what component having the most mass for poundage for performance.Horn versus core mostly.Keeping the ratio within reason is good.Crowning the sinew will help with performance.Tapering components before sinewing to put the most material where it is needed and bend the way it should is a bit like self bow making to refer to.I guess I just wanted to stir the pot a little on this thread.Maybe others considering making a horn bow will learn a little.Seems the only way to learn making these bows right is Adam Karpowiczes book mostly.Most people who make these type bows are accomplished bow makers referring themselves to that book and a lot of people don't have it.
They are fun to make but are not quite like the ease of roughing out a stave to a bow and making a fat 3/8" line along the side for a taper that's for sure like said again but really don't require any more sophisticated type tools or equipment,but some are just different that's all.Making calculated measurements of each component etc.Making these makes a person think quite abit more about different forces going on etc. too.In the end getting a deeper understanding of bow making IMO.
-
joachimM....The koreans at times use rather thin layers of sinew.Total of 2mm at most.Mostly on bamboo though?Reflexed from the handle etc.
I've done some extensive testing with the previous bow I made and it does shoot comparitively right up there with other horn bows listed in Adams' testing list.Using FF string though of 2gpp.Curious to see if any at all difference there is with this one.
I should apologize to Pat B probably but not sure if what he stated was meant about the ratios of components or the lengths of bows getting sinew depleteing performance.In the past it was discussed extensively that longer bows up to 64" did'nt benefit from sinewing.I've proven here if put where it works it does enhance performance.
-
Ed, you have raised a very interesting question, and as I have not yet built a horn and sinew wood core bow, I cannot offer any specific recommendations based on experience.
Having played around with backings and given some thought to the nature of composite constructions, I would like to bring to the discussion a few questions that might be pertinent to arriving at an answer to your question. Of course, as always, the devil is in the details, and as these considerations may not be complete, any additional design considerations would be welcomed.
The 1/3 - 1/3 - 1/3 layup seems like a good point of departure for comparing successive bows of similar designs, but is does raise the question of whether the sinew and horn need to be applied in equal amounts of thickness. Why not 1/3 - 2/5 -1/5 ?, or whatever ratios the back and belly are best capable of? Does the sinew and horn have the same stiffness and elasticity?, there by only adding thickness and poundage to the bow without shifting the strains in the core?
Presuming that your hickory is both lighter in mass and stiffer than either the horn or the sinew, why would the core for the composite you describe, be best served by tillering to twenty pounds? Is that how thin it needed to be for your design to flex the full range from reflexed to full draw? Why would you not want it to be as thick/strong as possible, as long as it was capable of bending the full range without taking undue set?
-
Willie the 1/3rds rule isn't set in stone but a good starting point.
If you go thinner with the horn the bow will acquire more string follow. If you go thicker then the bow will be more resilient and keep its pretillered profile better.
If you go too thin with the core then the bow will be less easy to stabilise. Thicker and you run the risk of it breaking.
Sinew thicker than 2/3mm isn't necessary. Thinner = broken bow.
Sinew/horn have similar resistances to bending.
The core and horn have to be exactly dimensioned before sinewing or else you will have 'built in' weak/stiff spots that cannot be fixed. Ed's way of pretillering the core is a good idea as it will eliminate this. However you want to be very careful and not pull it far at all.
-
willie.....Those are all good questions and Mike is all together right.I won't be afraid to pull this bow to 29" and will more then likely tiller it to that also.A few things I paid attention to constructing these bows is from 3 books really.First of course Adam Karpowiczes book.The other 2 volume 1 and 4 of the TBB series books.Tim Baker and Steve Gardners findings are fully engaged here.The degree of % of depth the surface works on a bow.Degree of work certain sections of the limb length doing work.Just deducting common denominator facts and applying them.Attention to mass weight.Inspiration can come from many places.That seems to be the key.I will leave that up to you.
Nothing wrong with different degrees of thickness of components.Mike explained the up and down side of them.Going 25/50/25 sinew/core/horn will work fine too.No specific well rounded numbers either because through tillering horn or sinew thickness can change to a small degree also.The thing is to use composites on shorter bows with extreme reflex to get the most out of the composites.The balance that horn and sinew have to each other is unique.Otherwise like said the mass weight will negate the efforts if going for performance if applied the full length of longer bows.Really no reason for that in my mind.
More detailed measuring/weighing is required.Lately I've been writing info on paper for future referral.I will be able to tell you exactly how much each component mass weighs when shooting the bow in.What starting mass weights are.The whole nine yards.Like I said earlier more detailed but to me worth it because of the strain these bows will be under.Getting the most you dare from the components within reason.This goes for all materials really.Even self bows.
Horn bows are just fascinating bows to me.Equaling and out shooting their modern counter parts is what tickles me,and just plain works of art in my mind.After all it is the Primitive Archer site right?I hope you sometime try your hand at some.I've got a lot of unchartered waters with them to discover myself.Making self and sinewed bows before hand is very helpful.It's not for everybody that's for sure.Never a dull moment though making these if the inspiration is there.I hope this helps you.
-
thanks for sharing your experience, Mike
working knowledge trumps theory in my book, after all primitives did not have to know "why" to make it work. ;)
-
Well willie seems the asians were at the fore front of a lot of it.Other cultures too just from necessity.Lacking father to son apprenticing written info is the only thing a person can do to learn.Lucky it was documented and shared.A person's gotta start somewhere and aquiring knowledge of the whys and why nots is essential too even before beginning.
-
So that makes sense that the core stiffness wouldn't matter as much since the outer fibers are the ones that do most of the work. But surely the core is stressed still. If it wasn't then it wouldn't be so important to have a blemish free prime wood core, or we could use a knotty piece of pine. So that tells me it is stressed at least to some degree, and if that's true its stiffness will have some factor. Maybe not as large as I was thinking but still present right? or is there something else I'm missing.
-
gfugal...Yes of course.With any of these type stressful designs a good flawless core is required though.As are the other components.It does'nt make any sense to make a bow with materials with flaws in them in these type designs.
A less strained one possibly so.To walk that fine line is up to the bow maker.
-
greg makes a good point, about the work done in the core. just because work is concentrated at the outer surfaces, a fair percentage of the work is done as you get closer to the center. much of the finessing done getting a bow to it's best potential means that all parts of the limb would be well served to be optimized.
Understanding theory may not be necessary to inherit knowledge, but understanding whats going on sure helps lowering the experimentation curve. I am all for learning both. Sometimes there are factors that we overlook in our theorizing. Experience or history can often show, that the best is yet to be re-found.
BTW, is the flight record for the Turkish bow that has stood since sometime in antiquity, considered to be fact or myth?
-
I don't know about the Turkish distance record.I've read some shots were not recorded.So who knows.Understanding their language describing things takes a little time.I'd say Adam has got a handle on that info.In fact he's testing bows right now on the atarn web site.
Core is important for sure.A dense elastic one with good glueing qualities would be my choice.Others may say different.Maple has been a go to core material for quite some time.I would say if you can't make a bow out of the core or it take the bend needed from a flat profile then your taking a chance using it is another way to look at it too.
-
one aspect considering stress in the core, is the shear forces that come into play. typically with a self bow, tension and compression limitations at the surfaces demand very good wood selection, and govern the designs and materiel selections. As a point of interest, there was recently a bow posted that had a hidden flaw in the limb that resulted in a unexpected failure. A cursory examination of the accompanying photo, looked to me, to be non-typical for a tension or compression failure. It would not surprise me if that bow failed in shear, at the central flaw, resulting in a weak spot that ultimately induced the total limb failure.
Shear failures are also often seen when a glued handle "pops off".
what reading I have done on composites, often mentions the need for careful core selection, leading me to believe that shear limitations often dictate in composite designs. this makes sense, as the sinew and horn is selected for their exceptional tension and compression qualities, asking the core to handle more shear stress that attends more radical bend radii.
I have often wondered if the preference for maple is on account of its diffuse porus qualities. It does seem reasonable that a shear force could be easily localized on the spring growth portion of a ring porus wood, especially if it were flat sawn, making it a poor choice.
-
Yes the sheer forces going on need to be accounted for although if constructed properly not a problem,but proper construction won't override poor quality.
Yes your right about maples' diffuse porus qualities making it a good choice for glueing.Using ring porus with large early growth would not be my choice especially flat sawn.
I've been getting away with using hickory on mine.Very fine ringed.Early wood like dots.Flat sawn.Time will tell if I get away with it.So far it has.
-
Willie - you are dead right it is a sheering force that the core feels, as it is on the neutral plane (give or take). If the sinew is too thin then the core starts to feel tension and will fail everytime....don't ask me how I know this!
Maple is indeed chosen for it diffuse porous properties, ring porous woods are likely to fail along the earlywood layers, or at the very least each earlywood layer is a 'built in' weakness. Maple will of course also handle being steam bent into a pretty extreme shape and glues very well. A good core wood will have all these properties.
People have used ash (and other ring porous woods) for cores on less stressed bow designs, however if you are going to use a ring porous wood then it is a very good idea to use it 1/4 sawn therefore 'homogenizing' it compared to flatsawn. The only issue with doing this is that wood is stiffer laterally with a flat sawn piece compared to 1/4 sawn. Flat sawn will make the bow quite a bit easier to stabilize - this is a major factor and becomes apparent when you first brace a bow.
-
Making another composite bow here.Going with less thickness of a core by 1/16" and more composites.
just curious why you are changing the proportions on this bow.? Are the working limbs bending to a tighter radius than the earlier bow, or are you shoooting for a lesser stringfollow? or better performance?.......
-
Those are some excellent example Beadman. I really like your bows. I need to attempt one of these.
-
I did'nt give strict heed to a few of the rules making a bow like this with materials and design,but it has worked.Like with any bow time and usage is the ultimate truth extractor....Ha Ha Ha.
I think your bows are a work of art to be truthful.I need to sometime try an all horn or an all antler bow too.All these type bows seem to be the meaning of patience in primitive archery.
-
Talk earlier on this thread was about how much work a core is doing.Think it was gfugal.I look at it this way.When 10% thickness of the limb on the outside[a backing] does 50% of the work yes the core is doing 50% of the work[one reason too for a decent ring on self bows] and 25% thickness of the limb on the outside[a backing] is doing over 80% of the work yes the core is dong around 20% of the work too along with the sheer forces discussed.Quite a load off it already.With 35% thickness of the limb thickness[a backing] on the outside it is doing close to 100% of the work but the sheer forces strain will still be the same the way I understand it.Engineering minds come up with these findings of which I don't argue their point.The asians/indians/turks and other cultures figured this out long before PHD diplomas were handed out through trial and error I imagine.
That's why the 1/3,1/3,1/3 ratio of components they've shown are ideal for horn/wood/sinew bow composites.This is old hat to those who have been making these but for someone new to it not and it's an explaination why it works so well.It does not mean though that is written in stone like Mike said but a good starting point.It can be 25%/50%/25% ratio too with very good results.
-
there seem to be many different composit designs out there, some with shorter working limbs than others. Wouldn't a shorter working limb have to bend into a tighter radius?, and consequently need to have a higher proportion of sinew/horn to wood?
seems like longer and easier bends could use more wood, although the trick might be to properly balance the sinew to the horn strengthwise, so that the wood remains centered about the neutral axis of the entire limb?
-
Willie, yes you see this actually, when examining cross-sections of different designs across the length of the limb.
But also bear in mind that moisture content management also makes a huge difference. Both horn and sinew strongly increase their stiffness from 12% MC (which is way too high for sinew-horn bows) to 4%. In my climate (temperate humid) I can hardly get to below 12% MC without a hotbox or similar.
-
waterbuffalo horn, from a buildalong at
http://paleoplanet69529.yuku.com/topic/57441/Turkish-Bow-4-Year-Journey
the horn appears to be twice as thick as the sinew. I do not have adams book, so I cannot look it up for myself, but does he mention the relative strengths and working strain limits of the various horns and sinews?
-
joachimM is right I feel to a degree.Depending on what a person can live with.Most times actual turkish horn bows are sealed with layers of finish and paint and guilding also slowing the infiltration of moisture.Adam talks of using them in rain storms with no ill effect.Just part of the landscape owning one you have to put up with using natural materials.Mike lives in England and owns many.Very humid there.Although it can take twice as long to lose moisture as acquiring it in them.Horn is affected only in half the degree with moisture as sinew and glue will be so it's resiliency is better.
Putting the bow back into a say 7% to 8% MC warm setting over a period of a week from a few days of shooting[braced throughout] it would return itself to original profile it took after tillering.
willie...As far as different strengths of horn goes I believe he mostly was satisfied with water buffalo horns' strength and use.Some very early bows made from ibex horn.He talked of cow horn being too thin,twisted and having delamination problems of which I've seen for myself.Gemsbok horn is ok too if you can find some thick and wide enough.I have myself here.Sheep or possibly goat horn done by a few fellas on here make great horn sinew bows from it.Works of art.Chuck,Goat,and Redhand has one going too.I feel it could function in a horn/wood/sinew construction.Bahleen I would like to try also.I'm sure it's a lot denser then wood and could be used.
Sinew of most types is good as far as strength goes he feels.He preferred moose leg sinew.Did'nt like any backstrap as it being too course and hard.I feel Pat M's method of wrapping and heating helps eliviate this.Actually sinew will shorten when it swells.To dry and shrink to that state.I've used beef backstrap,buffalo backstrap,elk leg the most of,moose leg,and deer leg and backstrap.All are strong enough to use.As long as the grains of weight add up to being what you need.I have not used ostrich.Getting rid of the grease is the thing to watch out for using any.
I would say that the bow you saw with thicker horn depending on proflle of course would still have to have enough sinew on it to a thickness to stop any chance of splintering yet.
I can say in truth I shot the previous bow I made close to every day for close to 4 months straight for sure 6 to 8 hours a day bracing times in misty rainy days too[then unbraced overnight] with maybe 1/4" of set showing to the next day.With one full day of rest it was right back to original profile when first tillered.That's being stored inside the house then too inbetween shooting.Very little stress shown on these for the amount of reflex it held.Resilient.