Primitive Archer
Main Discussion Area => Bows => Topic started by: simson on January 30, 2014, 03:44:07 pm
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This day was a hard day, two failures on HLD bows. One chrysaled badly, the other exploded. I post some pics, because it is interesting.
The first bow is made of sumach. I always searched for this wood, because I knew it has a fantastic greenish color inside. And some weeks ago I got one. This wood is incredible light almost feels like balsa, my stave was only 4 years old, one ring white sap, 3 rings green heartwood. Full diameter at handle, where the hole of the pith can be seen.
The wood dried out very fast and got light, I decided to go as wide as possible and relative long.
The bow came out 50-55# and shot incredible – but only 20 or so arrows (HAHAHA). Then came down every shot. My examination showed the badest chrysaling I ever have seen. They were everywhere not only on the belly, but also in the outer thirds of the backside (cross section). For those who are interested, the bows mass is only 323 grams!
What have I learned: Sumach isn't a bow wood!!!!!!!!!!!!!!
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020307_zps07778550.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020306_zps30886eb8.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020311_zpsa20c2d51.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020308_zpsd732aae1.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020309_zpseb993b32.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020329_zps8078d204.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020331_zps3bac09b2.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020312_zps68017d0d.jpg)
The second one is an elder again, this time more a long bow design (71” ntn). It came from a long, nice, and slight twisted stave. The bow was already done, only some light sanding and finish were to do.
I (idiot!) wanted to know how far it could be bent. Had it on the tree to look at for drawweight, my scale had a mis function, he ld the full draw (30) a second too long – and bang.
This bow was a dream to draw - the smoothest draw! Draw weight was 60 at 28”. Mass is 528grams.
The initial crack is on the back (see pencil point), perpendicular to the limb (upper! > see Del's thread: where do they break?) It exploded with a loud bang and the crack run almost exactly between the first and second growth-ring til it was stopped by the handle wrapping.
What have I learned: Don't play around with a damn digi scale out of order when a bow is drawn!!!!!!
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020316_zpse4ba446b.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020318_zpsb9ffac18.jpg)
the initial crack where the pencil points
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020319_zps31492f4b.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020322_zpsbf57ec1d.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020327_zps1cb1d781.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020326_zps3e097656.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020325_zps6a553c53.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020328_zpsc4da662f.jpg)
(http://i1252.photobucket.com/albums/hh576/orangesimson/1401%20Two%20HLD%20failures/P1020321_zps5fe174ac.jpg)
excuse the excessive photostory
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It sure is beautiful wood. Too bad it doesn't take the stresses of being a bow. It does look like it blew up pretty dramatically, though. ;)
If they gotta blow I prefer a dramatic explosion. ;D
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That's a lot of pieces ;D :( Must be very dry where you are this year,too. RH of around 25% in my shop right now.
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Jeeeesh! Those were some beauties...I know you put a lot into those.
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Id try that sumac one more time with a flat belly before you check it off your list.
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That's too bad man. Even your failure bows look amazing. Did you toast the belly on the sumac?
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Do you know what type of sumac it was from? Staghorn sumac is supposed to be borderline, but I don't know about any other types. I've got tons of the stag horn near my house. The flowers make a great summer drink if you soak them in some water for a while.
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broken or not amazing what you are doing with these bows.
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Broken or detonated?
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Interesting to see that the chrysals go all the way across the limb instead of being confined to the edges.
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Wow I agree and explosion I'm glad you weren't holding it when it went?
DBar
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It sure is beautiful wood. Too bad it doesn't take the stresses of being a bow. It does look like it blew up pretty dramatically, though. ;)
If they gotta blow I prefer a dramatic explosion. ;D
Yeah Pat, I know what you mean. Same for me. They shouldn't go through the back door! ;D
That's a lot of pieces ;D :( Must be very dry where you are this year,too. RH of around 25% in my shop right now.
In my shop always between 45 - max 60%, I have a hygrometer hanging just below my bows!
Id try that sumac one more time with a flat belly before you check it off your list.
Pearlie, I definitely won't do that. Look at the sg or the bow's mass - that is no bow wood, I should have known that.
That's too bad man. Even your failure bows look amazing. Did you toast the belly on the sumac?
No toasting on both bows
Do you know what type of sumac it was from? Staghorn sumac is supposed to be borderline, but I don't know about any other types. I've got tons of the stag horn near my house. The flowers make a great summer drink if you soak them in some water for a while.
Yes , that is staghorn sumac. Don't know what to do with that spectacular colored wood, but as said no bowwood
Broken or detonated?
As said, the sumac chrysaled badly, the elder exploded with bang like a gun shot
Interesting to see that the chrysals go all the way across the limb instead of being confined to the edges.
Yes, that are my thoughts too. Good, you are pointing again on this. Also the elder bow with the initial crack in middle of the back. Wouldn't we expect a failure on the ridges bellyside? I think even that damaged bows are an argument for the HLD. I don't give up, I have some staves left which are suitable for HLD.
ALL:
Thanks for your thoughts and response!
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Yes the failures are the important ones! They tell you for sure what you only surmised before.
The chrysals are the most interesting to me. Yes they go right across (great!) but they appear from the photos to be worst at the edges? Am I right here? The tension break is also a good thing in my eyes it shows that the wood is being made to work properly with reference to it's properties. As in bows normally fail in compression due to (most) woods being stronger in tension. To be fair I haven't done many bend trsts with elder but I would presume its a tension strong wood. On a side note have you ever hada compression fracture with elder?
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Too bad about the bows.
My take on this design is that, although interesting, it is not a viable method of making a reliable wood bow. Sure you may get some that will survive, for awhile, but unless you are using wood that has a very high elastic modulus then the bow is sure to develop problems, sooner or later.
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Real shame, gorgeous bow... but we're just gluttons for punishment ;D
Del
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Too bad about the bows.
My take on this design is that, although interesting, it is not a viable method of making a reliable wood bow. Sure you may get some that will survive, for awhile, but unless you are using wood that has a very high elastic modulus then the bow is sure to develop problems, sooner or later.
I haven't built any HLD's so, what do I know, ...but nothing that I see in the work presented here would lead me to conclude that HLD is not a viable method for making a reliable wood bow. I know you have a very high degree of bowyer expertise, and I do not mean to call that into question. I'm just curious, - - - What are you seeing here that causes you to suggest that? It just seems like a very broad leap to a very distant conclusion.
OneBow
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I concur with Marc, but boy I don't want argue my feelings. I completely respect Simons work just as much as Marcs. But I have my own feeling on high and low points working and HLD bows. I think Simon needs to trademark that "HLD" term btw!
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I'm still getting my head around this whole concept of hollow limb design - it blew my mind when I first saw it on here... seemed so counterintuitive to have so much compression force acting on two narrow ridges of belly, but I kinda get it now that the force is absorbed by the flattening out of the bow's cross section.
Could one explanation for these failures be that the walls of the HLD weren't sufficiently thin to allow enough of this flattening out effect?
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Both these woods are low density, and probably not very elastic. I wouldn't throw out HLD as a viable option based on failures with these wood types. It is probably a design that favors highly elastic woods, considering that there are additional force vectors (not simply compression and tension) which factor substantially in this design.
Gabe
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Both these woods are low density, and probably not very elastic. I wouldn't throw out HLD as a viable option based on failures with these wood types. It is probably a design that favors highly elastic woods, considering that there are additional force vectors (not simply compression and tension) which factor substantially in this design.
Gabe
+1
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Thanks for sharing these failures rather than just sweeping them under the rug. I am surprised to see members dissing the hld design because a non-bow wood and borderline bow wood blew up on you.
I always enjoy your bows simson. I am working on my first HLD, and of course it is from a highly reflexed low-density bow-wood, cascara. working towards brace now, and it is quite clear the design allows a stiffer limb with less mass. It is also clear it is going to take study and practice to properly execute. Just as a square limb cross-section has an optimal width vs. thickness for given bow length, weight and wood type, so does the HLD have a optimum, but it is more of a wall thickness vs limb depth relationship you are working out.
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Some guys obviously didn't read my first post. To say it clear:
The sumac gave up because it was a high stressed no-bowwood.
The elder blew up because I had it at 30" for some seconds while struggling with the scale, it was tillered to 28" but had potential for more.
Yes the failures are the important ones! They tell you for sure what you only surmised before.
The chrysals are the most interesting to me. Yes they go right across (great!) but they appear from the photos to be worst at the edges? Am I right here? The tension break is also a good thing in my eyes it shows that the wood is being made to work properly with reference to it's properties. As in bows normally fail in compression due to (most) woods being stronger in tension. To be fair I haven't done many bend trsts with elder but I would presume its a tension strong wood. On a side note have you ever hada compression fracture with elder?
Mike, the chrysals go around the ridge, think on a cross section - the fractures appears on the entire belly and the outer third of the limbs. And yes I'm with you elder is a tension strong wood and very elastic. I never had compression fractures with elder.
Too bad about the bows.
My take on this design is that, although interesting, it is not a viable method of making a reliable wood bow. Sure you may get some that will survive, for awhile, but unless you are using wood that has a very high elastic modulus then the bow is sure to develop problems, sooner or later.
I'm convinced this is a great design to save mass and it has other properties too. Meanwhile I have made at least twenty bows, some still in my possession and still in use. They are very fast and save. But we should work on that and share the experiences.
I'm waiting on your HLD.
I concur with Marc, but boy I don't want argue my feelings. I completely respect Simons work just as much as Marcs. But I have my own feeling on high and low points working and HLD bows. I think Simon needs to trademark that "HLD" term btw!
.... trademark .... LOL 8)
I'm still getting my head around this whole concept of hollow limb design - it blew my mind when I first saw it on here... seemed so counterintuitive to have so much compression force acting on two narrow ridges of belly, but I kinda get it now that the force is absorbed by the flattening out of the bow's cross section.
Could one explanation for these failures be that the walls of the HLD weren't sufficiently thin to allow enough of this flattening out effect?
examined the bow (the pieces) once more - I don't think so Smokedancer!
Both these woods are low density, and probably not very elastic. I wouldn't throw out HLD as a viable option based on failures with these wood types. It is probably a design that favors highly elastic woods, considering that there are additional force vectors (not simply compression and tension) which factor substantially in this design.
Gabe
Sorry Gabe, but especially elder is a very elstic wood.
Thanks for sharing these failures rather than just sweeping them under the rug. I am surprised to see members dissing the hld design because a non-bow wood and borderline bow wood blew up on you.
I always enjoy your bows simson. I am working on my first HLD, and of course it is from a highly reflexed low-density bow-wood, cascara. working towards brace now, and it is quite clear the design allows a stiffer limb with less mass. It is also clear it is going to take study and practice to properly execute. Just as a square limb cross-section has an optimal width vs. thickness for given bow length, weight and wood type, so does the HLD have a optimum, but it is more of a wall thickness vs limb depth relationship you are working out.
YES
Oh man Carson!
I can't wait to see your HLD!!!!!
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I heat-treated an Ironwood bow several years ago that had wide limbs. The heat did a very odd thing to the wood, it made the belly concave to the point that it was very similar to your hollow limb bow. The first time I braced the bow one of the limbs split right in half from handle down to very nearly the tip.
Your Elder bow, even if held at full draw for several seconds would not have exploded unless there was something wrong with it. I've lent, sold, given away bows tillered to 28" that were drawn well past that 28" yet they didn't explode.
I'm not saying that you simply cannot get a working bow using this method, I just wouldn't trust it if I had to go out and put meat on the table or defend my people.
Just out of curiosity, was it the top limb that exploded? :)
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That top bow was beautiful. Hopefully you can get one to hold up. Good luck
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Man, that is a bummer Simson. Those were looking sharp. I been wondering, have you ever tried a reverse HLD with the hollow side toward the back? You got me thinking on it.
Like when a tape measure will fold over one way but not at all the other way. I wonder if a ring could be chased on a sapling from the center of the tree toward the outside of the tree and end up with one ring in a reverse HLD and then tapered somehow to the tips. Ever thought on this?
I am probably nutty as squirrel poop.
Thanks for the awesome bows you make, Marco.
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Thank you for posting these Simon. Very thought provoking. Some of the damage is what I expected, but yet not quite. The tension failure looks exactly like I had envisioned it would. That is to say showing a tension load across the entire outer surface of the limb. The chrysals on the other one are not where I thought they would be. To be more specific, I expected them across the entire inside surface, but not on the outside. It would appear that at some point the compression load is a little higher on the outer thirds. Your HLD appears to be pretty close to a half pipe cross section. I wonder if a less extreme profile would have faired better, but still maintained some energy storage advantages. For instance, say the cut away profile were only a third of a pipe instead of a half pipe. Just sort of thinking out loud here. Sorry for the ramblings. Josh
Edit...scratch all that. After closer scrutiny, I can see I need to study on this a lot more.