Primitive Archer
Main Discussion Area => Bows => Topic started by: 2nocks on July 12, 2020, 12:09:42 pm
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Hi guys !
New to PA, please forgive the long-ish post. Hopefully some of the details won't put everyone to sleep.
Probably way out of my league in terms of (my lack of) skill here, but there's one little bow in the British Museum I've been trying to replicate. It's a tiny 34.5" extremely recurved almost U-shape little yew wood bow beautifully decorated in porcupine quills. There's no recurve in the tips and all the (un-braced) recurve is mid-limb.The final braced and full-drawn shape of this bow is a bit of a mystery (to me) although the sinew build-up at the nocks would suggest it might have been quite heavily drawn back and they didn't want the string to slip off. I'm guessing about 1/3 - 1/2 thickness of the bow is the sinew. I'd have loved to post some 'non-failure' results, but as we all know that's not how things go in the land of bow making, so please if any of you have some advice please feel free to chime in.
I did two light courses of sinew and knee/floor tillered it to even out the limbs out. Then I did 3 more layers of sinew to bring it in to a more U-shape reflex. I can't even get a string on it yet or brace it. But I began the tillering by bending it over my knee and re-checking the flex of each limb, I started to thin it down and bring it closer to final dimensions. I've been going very gentle and slowly with this bow and definitely haven't pushed it or pulled on it more than what I feel the wood can handle (and never more than in the 2nd pic). but I noticed a spot flexing/ working way more on one limb. And then also noticed the sinew beginning to lift or fail in that spot. A closer look reveals two strands of sinew that are lifting but also little hairline fissures branching off that indicate a more serious failure. I'm kind of surprised, because I haven't heard any sounds or cracking or anything to make me believe the wood failed underneath in tension and there are no signs of compression fretting or fatigue (with good yew can this even happen?)
Is this game over ? Or can sinew failure like this be recovered ? It's just at the beginning of failing, so I haven't creased or hinged or fatigued the wood, but is it best to tear it down, recycle the sinew, look for wood core failure and start over ? I didn't think sinew ever failed without a wood core failure underneath.
Any help or shared experiences would be greatly appreciated.
Thanks !
-Jonathan
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I have had sinew do that,, when I did not have the glue thick enough,, usually when the sinew glues really well it wont lift a strand,,, I am just guessing,, it could be core failure,, it would not take that long to take off the sinew and see if there is a problem,, if no problem with the core then your sinew application might be improved,,
also I have had different quality of sinew,, if you can break a small strand in your hand,, it might not be the best,,
maybe it rotted a bit before drying or some unknown,,again I am just guessing,,\\
you could sinew wrap over that,, using more glue,, or put another layer on the whole bow,, I hate so say this but I think taking it off and starting over would have the highest rate of success,, Im sure others will chime in,, and you can find a solution that will work for you,,
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I'm not very experienced with the use of sinew, but that induced reflex looks like one hell of an ask even for yew.
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I'm not very experienced with the use of sinew, but that induced reflex looks like one hell of an ask even for yew.
That was my thought too. Sure is a pretty bend though :)
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If Perry reflex is real, why can a wood and sinew bow not be reflexed to a ridiculous degree? If it doesn't "feel" compression force until it's bent back to its original presumably flatter shape.
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If Perry reflex is real, why can a wood and sinew bow not be reflexed to a ridiculous degree? If it doesn't "feel" compression force until it's bent back to its original presumably flatter shape.
Hmmmmm, give me an hour or so ;D ;D
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Thanks for the replies so far.
After reading what Perry reflex is I think this would qualify. I didn't use blocks at the tips or clamp the grip down, but more like Turkish or Korean bows I pulled the tips together with string while the sinew was still wet and drying.
I'm leaning towards a bad glue up or lack of knowledge and experience in sinewing. I had read that if you use too thick a glue then it can give you cracks and scary sounds as the crystalline structure of a heavily glued-up bow shatters apart. So pretty sure I steered more towards a thinner solution of glue to try and avoid this. Today also have new delaminating at the edges on the tips between layers 2 and 3 of sinew. I can now see this might be putting some lift pressure on the layer of sinew as the wrapped edge is flexing around the bend. Though I seem to remember may other types of sinew bows doing this and not having any difficulty.
Under a good amount of light I can see another similar little hairline crack developing in the sinew -though nothing lifting yet. What concerns me is that these cracks appear to go really deep into the whole thickness of all 5 layers of sinew. If it were just little shattering cracks on the surface I could chalk it up as the glue stretching more than it's 8-10% at the very outer layer of sinew and keep going. But it appears these cracks are setting up very deep into the sinew even into the base layers where the stretch shouldn't be hitting it's limit yet.
For those that might be curious I'll post a pic of the original in the museum - unfortunately it's an old grainy pic.
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Could it be the glue that cracked? If too much glue is used the glue can crack and if that is the case I don't think it is a real problem. I don't know why the wood would crack under the sinew/glue backing.
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I have had sinew do that,, when I did not have the glue thick enough,, usually when the sinew glues really well it wont lift a strand,,, I am just guessing,, it could be core failure,, it would not take that long to take off the sinew and see if there is a problem,, if no problem with the core then your sinew application might be improved,,
also I have had different quality of sinew,, if you can break a small strand in your hand,, it might not be the best,,
maybe it rotted a bit before drying or some unknown,
-I can pretty much rule out bad or rotten sinew. It was good quality fresh Elk leg tendons, and I cannot break a small fibre with my hands.
-I really don't think this is wood core tension failure yet. I haven't even pulled on the bow past neutral where the wood was at in it's natural resting state as a lightly recurved bow stave branch.
-maybe your suggestion that the glue wasn't thick enough. it is showing some signs of delaminating between the sinew layers and coming off in parchment paper light sheets. I may have erred too much on the side of thin glue after reading stories online about thick glue cracking too much under stress. though my pot of glue was like light syrup and when cooled set up as sticky to the touch when fingers dipped in glue and gelatine when cooled in the pot. So wasn't water thin either.
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I took me a while I did some too thin, and some too thick,, but it seems erring on the side or too thick really did no damage,,im sure there is a point where it would,, but I have not experienced that, I think its a matter of getting the right amount of glue on the sinew,, not squezing out to much,,,,and keeping the glue warm but not too hot,, aot of variables that are hard to explain,, also I think sizing in between layers is good,,,, but have no proof of that,,
I think where too much glue might happen is some have tried to add glue after the fact to fill gaps and such,, and that might cause it to crack,, I just try not to squeeze it out to much,,,I just lay it on the bow and dont touch it after its laid down or try to move it,,, if the glue is right thickness it will just stay there,, and if the sinew is soft from being in the glue,, or soaking in water,, I soak mine in water,,, but it will work either way,, I just squeez out the water put in glue and lay it on,,
I think it sure would not hurt to put some on a scrap piece of wood, one glue thin, and one glue too thick and see which one works the best,,
I will add that in an effort to reduce weight or mass of the sinew,, I did thin my glue quite a bit, and thats when I had the failures,,,I hit the point of diminishing return ,,, (W
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It really is quite simple :)
25 - 30% glue for the first two courses.
20 - 25% for the last layers.
Weigh the dried glue, weigh the water mix :)
No need to experiment :)
All that is happening here is the glue cracking.
Carry on :)
However your outer limbs are far too stiff and the bow is hinging at the spot you marked out.
Yes any yew can chrysal......no doubt about it and yours isn't going to be far from it unless you fix the hinge first and get the mid outer limbs bending.
Don't expect much on the drawlength side of things either, maybe 18 19 inch at max. It won't shoot very well because it is sooooo sahort.
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However your outer limbs are far too stiff and the bow is hinging at the spot you marked out.
Yes any yew can chrysal......no doubt about it and yours isn't going to be far from it unless you fix the hinge first and get the mid outer limbs bending.
Don't expect much on the drawlength side of things either, maybe 18 19 inch at max. It won't shoot very well because it is sooooo sahort.
Thanks for this advice.
My first thought was that the bow was starting to hinge at the spot the sinew cracked, because the sinew cracked. and if I tiller in consequence of this then I'd be building a bow and trying to match the tiller of the other limb in consequence of this defective crack (rather than say repair or redo faulty sinew).
Glad to hear I should carry on and these are probably just normal glue cracks.
Could I trouble you to venture a guess as to whether you think the recurve in the outer mid limb should be tillered to the point where the recurve section bends to almost flat ? and if the tips should bend back as well ? Should this bow look more like a D bow when strung ?
I thought the bow in the museum looked a little rigid or stiff in the tips. In the photo it almost looks like the mid-limb is tillered thinner than the tips. but the dimensions are 13mm at grip, 10mm mid limb, and 8.5 at tip. The ratio of sinew is a bit unknown and I have no clue if the tips were super bendy or super rigid. The only clue is that the top specimen is damaged and the wood is completely rotted away near the grip and holding together purely by the sinew. So it looks heavily sinewed almost like a horn bow.
Agree that the recurve needs to be tillered out to avoid hinging at that spot thanks for pointing this out !
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If you don't mind could you keep us posted as to the results? Even if it fails. Well, actually, especially if it fails.
I'm still thinkin' PatM. Trying to understand sinew makes my brain hurt. :D
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.. Yes of course I'll definitely keep this thread up to date with results - even if it fails !
:)
I'd love to at least get this thing strung up before it breaks.
I have no problem if it shoots poorly or if it only get a 16- 18" draw -actually that would be a fantastic success !
I'd love to see what a more experience builder can do with this.
Happy to share more info if ever anyone is interested.
These were collected by Captain Vancouver in the 1790's. The origin or location, however, is a bit unclear.
I can also pretty safely stylistically link these two bows to another two bows in the Smithsonian collection, but by then -the Wilkes expedition- a hundred years later they had lost the extreme U-shape recurve.
Edited Sorry I'm wrong on that date -It was Captain Vancouver in 1790's and Cook in 1770's - these bows do indeed come from Vancouver 1790's
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I have some bows that draw 20 inches and they shoot well at close range with the right arrow,, I think it will shoot well at the 18 inches,, you not gonna win the olympics with it,, but for what it is ,, it should shoot nice,,
and probably pretty far with a light 18 inch arrow,, it may take you more than one try to get a shooter,, buts thats normal when learning a new skill set,,
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For comparison,
The closest thing to it that I could find on the PA forum, was a little horn bow almost 35" bow posted by Chuck Loeffler in 2012
Here's the link >> (not sure if I'm allowed to post a link) but it's to this forum and I'm not trying to advertise anything. Mods please remove or chime in if this is not allowed. But pretty sure he's talking about the lower bow on the rack, but the top bow in the pic looks like a very similar shape to this U-shape yew bow from the coast. maybe my tiller should aim in this direction though.
http://204.57.114.190/smf/index.php?topic=35859.0
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This is a bit off topic but in 1792 Capt Vancouver was in the waters in front of my house. This made me wonder if it was a local bow. I looked up his life and in the 1770's he was on Capt Cook's ship. I would think that anything collected on a trip would be credited to the Captain but I'm not sure. I couldn't find out in what capacity Vancouver was serving on Cook's ship in order to get credit for collecting the bows. Have to find out where Cook went on his 1770 trip.
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This is a bit off topic but in 1792 Capt Vancouver was in the waters in front of my house. This made me wonder if it was a local bow. I looked up his life and in the 1770's he was on Capt Cook's ship. I would think that anything collected on a trip would be credited to the Captain but I'm not sure. I couldn't find out in what capacity Vancouver was serving on Cook's ship in order to get credit for collecting the bows. Have to find out where Cook went on his 1770 trip.
This is very on topic !
I didn't know Vancouver served on Cook's ship. Thanks for digging that out.
My previous post was wrong on the date (I had confused it with Cook 1770's) . -these bows are indeed attributed to Captain Vancouver on his 1790's voyage.
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Wikipedia has a pretty detailed account. Vancouver's 1792 trip would put those bows in my general area. I've never seen any bows at all from this area. I don't know if there are any in the provincial museum. I'll have to look and see what I can find. I doubt if any have survived as it's very wet here and things rot in a few years.
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He came by way of Australia and made North American landfall in California and explored to Alaska. The bows could have come from anywhere. His "A Voyage of Discovery to the North Pacific Ocean and Round the World in the Years 1790-95" covers the whole trip in three volumes. I suppose there is a possibility that he commented on where he got the bows.
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He came by way of Australia and made North American landfall in California and explored to Alaska. The bows could have come from anywhere. His "A Voyage of Discovery to the North Pacific Ocean and Round the World in the Years 1790-95" covers the whole trip in three volumes. I suppose there is a possibility that he commented on where he got the bows.
DC > Yeah actually reading those journal notes (and some of the journal entries of his fellow crew members) indicates that bows and arrows were popular barter items with the crew of the HMS Discovery - Vancouver's ship. I thought it would be super cool if I could actually find the day or the record in his journal that he likely traded for the Miwok bow or the Yurok bow (?) which are two other highly identifiable bows in the collection by their hook and bent tab nocks. And then go digging for a journal entry that mentions the other 3 bows. But the journal is so littered with entries that mention trading for hunting gear and tackle, (considered by the crew as a sign of peace and willingness to trade, when the weapons were laid on the ground in front of them), but what's more amazing is actually how come only 5 of these bows ended up in museum collections in England. The likelihood that most of them were given away as gifts to friends or noblemen men and their kids to play with is actually a theory that's been floated around. Vancouver's crew must have also been well fed. Because when you read Captain Cook's account of their bartering 20ish years earlier, they were always hungry for venison and dried fish and mentioned that they traded copper items and fish hooks to obtain (better) food.
My best guess (but I'd love to be shown or told otherwise!) is that these particular two bow came from the area of Port Discovery / Puget Sound and might be Clallam (Klallam) of origin.
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very cool,,
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Could it be the glue that cracked? If too much glue is used the glue can crack and if that is the case I don't think it is a real problem. I don't know why the wood would crack under the sinew/glue backing.
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I probably need glasses but I'm having difficulty seeing the problem😕
Been a while since I posted much here but I do remember a thread by Pat M. I think that was about wrapping and then heating sinew to squeeze out excess glue and get a glassy surface.
Maybe you could scrape a bit down into sinew, apply a thick sizing coat of glue, apply a new sinew layer and then give the wrap and heat method a try.
Might help if you really think it's not right as is.
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The photo of the museum bows is not the best, but on the middle bow it looks like the tips are sinew past the wood. That and the rest of the shape would mean these bows were picked up in the San Francisco bay area and are Miwok origen. A frontprofile would help. Were the bows 1.5-" wide? These bows would have picked up more reflex than they once had from being unstrung that long on a thin wood frame under the sinew. If it were not from the Vancouver expedition I would say it must be a interior horn bow. You mention porcupine quillwork? That puts it in the Northern plains/plateau area where horn was used.? I have never heard of quillwork on west coast bows.
Your asking a lot out of a wood bow. The reflex profile is one for horn. I hear the Perry reflex theory, but the sinew gives the wood a permanent deformity with that much reflex so it is still under a bit more compression that without. The wood is not acting as a stabilizing core as in a composite horn bow, but as a belly and core. Horn can handle around 5x more compression than wood. Not to mention it is going to be pretty unstable when it's braced.
You did a great job on the bow. That much sinew and reflex you need to make sure your glue is the best and there is no contamination between layers and properly sized for each. I would not attempt this bow with wood belly
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The photo of the museum bows is not the best, but on the middle bow (referring to bow "Van 6") it looks like the tips are sinew past the wood. That and the rest of the shape would mean these bows were picked up in the San Francisco bay area and are Miwok origen. A frontprofile would help. Were the bows 1.5-" wide? These bows would have picked up more reflex than they once had from being unstrung that long on a thin wood frame under the sinew. If it were not from the Vancouver expedition I would say it must be a interior horn bow. You mention porcupine quillwork? That puts it in the Northern plains/plateau area where horn was used.? I have never heard of quillwork on west coast bows.
Just going to try and provide some more details and reply to a few questions that were raised here - because I am glad @ leofflerchuck points out some anomalies with the quill work and shares more his experience with west coast and plains bows.
- I've got another grainy pic of a front profile that I'll post here. >> Yes the bow at the grip is exactly 1.5" wide (x 13.5 mm thick)*not sure if this includes the leather thong or if the leather was subtracted. I’m guessing subtracted. . Mid-limb it goes down to 1 3/8" (x 10mm thick) and at the tips it's 9/16" (x 8.5mm thick)
- I'm glad you point out that quill work on a west coast bow would be quite an anomaly. And that a bow of this profile should probably be in horn. These are things that have been mystifying me, but I admit I never even considered that it may be of Northern plains/plateau origin because it was definitely picked up in the Vancouver expedition. But that's not to say it couldn't have been traded west to the coast or that the coastal people made a wooden copy of a horn bow (of inferior quality) to pawn to the English for things of more value to them. Or maybe the plains people made an inferior copy of a horn bow to trade to the coastal people who then passed it off to Vancouver.
-You raise a good point though, what's this yew wood bow doing with quills and the profile of a horn bow, allegedly from the region of Puget Sound ?
The bow is wood and not horn. Some early sources like the museum catalogue and a few early academic papers that detail these two little U-shape bows say it's cedar - but I think in the 1800 and 1900's the English might have just called or thought any west coast wooded bow to be made of cedar. But a good friend of mine (and bowyer) drew / surveyed this bow in the 70's or 80's and said he thought the wood is yew. I've never handled it first hand. I'm working off of his photos and drawings. Not sure I would know what to look for to tell the difference between (incensed) cedar and yew anyway as I've never worked with cedar. Is it more yellowish lighter colour than the deep aged reddish hue of yew ?
I don't want to bore anyone with more details about the research and history of these two bows, but if anyone is interested just PM me or if there is more general interest or curiosity just ask me to post more info here. I'd be happy to share what I've found. For now I'll put up the other grainy pics cus they do show the wood and they do show the quills.
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I also have some results to share and post.
yesterday was my first day wrestling with this thing and actually getting a string on it.
I was tricked by the sinew. I have two other west coast bows that pull aprox 55 and 60 lbs at 18" draw
(18" is my preferred draw) and this little sinew bow felt like it was 70-80lbs trying to just wrestle it to get the string on. So I thought I had plenty of margin to tiller from there. But once the string was on and it curved over to the other side the way it should be braced it softened up much to my surprise and disappointment like a springy noodle. Way too much for my liking. and by the time I tillered the rest of the bow to avoid the potential hinging spot that I had originally flagged in one of the earlier photos with the yellow circle, it was too late for this to be a heavy puncher. Overall, I'm about 1mm under dimension at the grip and 0.5 mm thinner than the original mid-limb. Which is too bad cus after all this effort, I would have loved this bow to be about 10-15 # heavier. It also feels sluggish and slow, but probably cus it has more sinew than it needs. If I were to do a second attempt I'd give it less sinew and more wood. and not be scared into thinking the yew can't handle compression in this extreme recurve design at thicker ratios of wood to sinew. So far this isn't showing signs of fatigue - though if I were to shoot 100 times at 20" draw, which I might attempt after learning what I can about it at 16-18" first.. then maybe I would start to see some chrysals.
There are no compression frets or signs of failure and I did end up with a working shooter. So I guess that's a small success worth celebrating and improving upon the next time.
@ loefflerchuck - I now see what you mean by totally unstable in brace position !
here's my results.
Fresh strung in the morning and after use for about 10-15 shots:
16# 10"
20# 12"
24# 14"
28# 16"
32# 18"
it also picked up a fair bit of 'set', whereas I was building it with about 20" spread between the tips (thinking it would relax or set to 22-23" it has now set to 26". perhaps the originals reflexed more over disuse and time, but I'm also thinking a thicker wood might have kept it's shape more.
*edit > tried longer draws and it'll pull 38-40# at 20-20.5" Arrows are pretty zippy (no chronograph to actually measure) but I'm starting to see penetration in the target similar to depths that I see with my heavier bows. So at least potentially this little thing can deliver. Thanks to a kind member who pointed out that I should try with a shorter / lighter arrow :)
I think this bow would be a screamer with a bit more meat on it's bones. And about 15# heavier.
Worth trying to make again.
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Very cool!! Shoot the heck out of it while you're building a replacement and see if it chrysals. Report back here ;D ;D ;D
PS The belly seems quite flat. I'm wondering if that's why you're not seeing chrysals----yet?
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I'm not bored. Thanks for the extra photos. The top photo, the second from the bottom is a sinew knocked bay area bow probably incense cedar. That indeed looks like plaited quillwork. I'm sure it could have come from Puget Sound. I don't think I've never seen these bows. I know Vancouver picked up the only surviving sinew backed Chumash bow. Probably of juniper from southern California. I'm not sure if he picked up any bows further south of that, but he worked his way up the coast and we owe him a thanks for collecting these treasures for us to study today. Keep in mind this was a time before firearms were in use by natives in the west and thus probably the peak of bow and arrow technology.
myself and others would tell you that 5" of reflex + or _ depending on length is optimal. More than that has diminishing returns on performance. Overworked wood gets limp, or in the desert here brittle.
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maybe the profile of that bow was not all about performance
but somehting to do with the bow maker showing what he was able do,,
but until I could see some chronograph test,, I would not really know if going to that much reflex had any bennefit,,
going past the 5 inches might not gain any performance, but it sure was pretty and that might be part of it,, I think,,,,but just guessing,,
I have never made or had a chance to shoot a bow like that,, but sometimes I think they did stuff for a reason that is not apparent,,,,something important to the bow maker or archer,,