today while i was tillering my bamboo backed hickory long bow i had it on the tree and drawn to just about 10" when i heard something ... it sounded like a short but distinct "tink" i let the bow down and took a good look at the limbs but didnt see anything. i looked at the knocks the handle nothing at all showed a crack... i thought that it must just be the fibers settleing.. i continued to tiller without any further sound but there was a hinge developing on the upper limb and i could not get it to go away..
i worked on the bow for quite a while finaly having enough luck that i though i could move on and string the bow..
when i strung the bow i noticed a small "scratch" accross the belly of the bow and up the belly towards the back on one side. i thought that it was a tooling mark so i sanded it out.but when i was excercising the bow the line returned and so did the hinge.
I now can see that the "scratch" is up the belly on the other side of the bow as well .. i can not get this scratch to open up but i fear that its a crack in the belly... has anyone ever had this sort of thing happen to them... i dont want to continue if the bow is lost... if it is cracked is there a way to save the bow...????
the scratch in question is at the point of the knife in the pictures below.
(http://i1020.photobucket.com/albums/af328/mcleodcarpentry/IMG00112-20100824-1446.jpg)
(http://i1020.photobucket.com/albums/af328/mcleodcarpentry/IMG00114-20100824-1447.jpg)
Oh man, bummer. I feel your pain, honestly I do.
I cannot offer advice yet from lack of inexperience, but I've got a crack starting on my upper limb of my Osage bow from not dodging a knot properly, hopefully I can repair it? I got some good advice from these guys on here, they know their stuff.
If anybody can help you....they sure can.
Sorry for your troubles, good luck.
SEMO
I believe it is a fret and one heck of a fret at that. Apparently the boo has overpowered the hickory belly. Is there a hinge at that point?
Post a pic of it drawn to 10".
Isn't that a crysal? Fret the same thing? How thick is the boo?
Yep that's a chrysal or compression fracture. There's a couple more to the right looks like. I have never really seen or heard of one satisfactorily repaired. Your bamboo should be a max of 1/4 (preferably less) of the thickness of the limb and you have to be devilishly careful not to hinge it as you tiller.
that boo looks very thin. She maybe toast. I would suggest that on your next one you do a little more smoothing and finishing on the belly before you put any pressure on it , hard to believe it got that bad with just 10 inchs. Its aways a bummer to learn while you burn.
Grind down the hickory belly to a thin layer, glue on a more compression strong slat and re-tiller the bow.
Very sorry...i like pat B's approach, still i think this one is done :coffee:
if the fret were in the core would it still be death for the bow.. my head is asking if i could ad a lamination and increase the bows draw weight sandwhiching the fret...??
Honestly, that's throwing good money after bad in my opinion. Worth a try if you want to do it but that one would go in the ever-growing "project pile" in my shop. You know, the ones you hate to burn or throw away but really aren't ever going to do anything with :)
I've seen people do it though and it clearly can work.
Just hate to throgh so much time away.. i have several days into this bow.. mostly glue dry time but shaping the handle and all not to mention my only piece of bamboo. ouch. (http://i1020.photobucket.com/albums/af328/mcleodcarpentry/IMG00108-20100824-1300.jpg) (http://i1020.photobucket.com/albums/af328/mcleodcarpentry/IMG00104-20100824-1259.jpg)
That is the reason many of us have learned,the hard way, to shape the handle AFTER the bow is tillered. Seriously. I learned that lesson from Pat B a couple of years ago.
Your question about sandwiching within another lam is exactly what Pat was saying in his post. Seeing that this is your only piece of boo, and with all the work you've put into it it is understandable, but, if you do that be sure to file down the hickory to paper thin before adding another lam of better material.
If you've used titebond glue I know that steam will release the laminations. That way you could reuse the boo on another project.
Just a thought, hope all goes well.
Now this post has presented a few questions from me. Sorry to kind of steer it away from the current topic. My first question is using Tightbond 3 glue myself. It can be steamed and the bond will break loose? I think this could be good for some of the "projects" I have in my shop. I agree about throwing all that time away. I just cannot bring myself to do it.
I have a bamboo backed bamboo that I built about 3 years ago. I was able to shoot it for a season then the bamboo backing developed a spit in the center of the upper limb right in the middle. The bamboo started to lift up. Kind of separate from itself if that makes any sense. Is there anything I can do to repair that. I was thinking 2 ton epoxy then backing it with snake skin. Any thoughts if that will work?
Mac, it is a continuing education, use Pats advice to further your abilities.
Fish, the snake skin is really just decor.
I've made repairs like this a couple of times and all were very successful. You should try to grind all of the fret out but if not super glue it well, let the glue dry and sand smooth before adding the new belly lam. My hunting bow for this year is a 60" osage bendy handle recurve. When I made it 2 years ago it had been off the stump for about 2 months. After a few hundred shots it developed a few frets in one limb(I'm convinced it wasn't cured well enough). I ground the belly flat and added a lam of Argentine osage to it and she is a sweet shooter now. The original bow was 48#@26" and now she is 55#@26".
If you did use TB glue it will release at 150deg(F). TB tech support told me that and I used my heat gun to heat and remove a hickory backing strip.
Pat, if he grinds the belly to remove the fret, how far should he grind into the core wood? Just enough to clear the fret? Almost to the glue seam? What would you suggest?
Stan
What I did a few years ago was to grind down(what was)the belly to about 1/8" or so and added a 1/8" belly slat.
On my most recent bow the frets were shallow so I sanded just enough to remove the frets and make it flat for good gluing then added the osage slats. These were tapered(a gift)but not precisely. After re-tillering this bow the osage belly slat is very small. The glue line adds a lot of draw weight. I used Urac for this bow.
You have to take each situation and figure what would work best. On another bow I removed the hickory backing with heat and threw away the fretted belly and added a new belly under the hickory backing. Each situation is different.
Ahhhh, the information age. This is sweet. years ago if i had been building bows and had a problem like this i wouldnt have known anyone that could help. (i dont know anyone in my hometown that builds) today i can come here to a place where people have already had these problems and have solved them. thank you all ... steam sounds like it would have been the way to go but i used epoxy on this bow. my form has 4" of reflex and i was worried about my favorite glue, TB2, maybe the next bow i will go back to it. tomorrow i will begin sanding the hickory belly off this bow and see where we go from there. i have a narrow slat of ipe that may substitute for the hickory if not i have more hickory maybe both...hmmmm???
With boo on the back, I'd opt for that ipe over the hickory any day. Remember, hickory is weak in compression, especially against bamboo (as you found out). Best of luck!
How thick is that boo?
The ipe would be better!
width of bow at fret. (http://i1020.photobucket.com/albums/af328/mcleodcarpentry/IMG00130-20100828-1256.jpg)
thickness of laminations at fret (http://i1020.photobucket.com/albums/af328/mcleodcarpentry/IMG00129-20100828-1256.jpg)
Your bamboo is way too thick.
When I make a bamboo backed bow I make every edge 1/16" thick. That is, if you look at the backing from the side you will see only a 1/16" tall edge. It will be the same edge thickness from the handle to the tip.
By keeping this thin edge you will naturally taper the bamboo thickness from where you start the taper to the tip and won't overpower your core wood.
What you have is what I call a "hickory bellied bamboo bow" instead of a "bamboo backed hickory bow". Made a few of these myself when I was trying to get the poundage down and ran out of belly wood because I left the bamboo to thick.
Here is how thick your bamboo should be for a backing. The osage core to the pencil line is 7/16" thick, the bamboo is 1/16" thick on the edge.
(http://img.photobucket.com/albums/v181/ekrewson/bow%20making/bbobackingthickness.jpg)
Eric. Is that bamboo backing, facing me in the picture ground flat? No nodes?
Is that a laminated boo? I am using a "full" piece of bamboo. is there a difference in its strength? i have not sanded off the nodes either. It seems if anything it would be stronger as a laminate..?
Nope, just plain old bamboo, nodes and all and rind intact. The bamboo in picture is the thin strip below the osage. The bow is 1 1/4" wide
Here is the where this bamboo came from, the corner of my shop, little green in this picture.
(http://img.photobucket.com/albums/v181/ekrewson/bow%20making/bamboostash.jpg)
Man I need to have my eyes checks. All I see is a piece of osage with a pencil line on the top of the picture, and what looks to be a piece of hickory grained wood on the bottom. I know I am loosing it, but I sure don't see any rind or bamboo there.
Its bamboo, you can see the power fibers on the edge, just left of the pencil mark about a half inch.
Backed off a little for this shot of my glue-up to prove it is indeed bamboo, just properly thinned bamboo. This type of bamboo keeps a green hue on the rind but had a beautiful caramel color after the rind is scraped off.
(http://img.photobucket.com/albums/v181/ekrewson/bow%20making/bambooglueuphandle.jpg)
Now I see it. I apologize if I offended you Eric, never doubted it was not bamboo. I just saw it as wood grain. Thanks for the picture and as always, great work.
No offense taken in the least, I just like to show off my stuff.
And I am so glad that you do. Anyone would/should be honored to have one of your bows. When does mine go out???? :bigsmyl: :pray: :pray: :pray:
Boy that put a halt to this thread real quick. I was only saying, not asking, that your equipment is top notch Eric. I learn from you on every post you participate in.
Eric,
could you post a pic of your bows profile up close at the node. I am amazed that your boo is so thin.. i dont beleave that i have the skill or the tools to make such a thin lamination. other than the lamination thicknes your boo looks the same as mine.. (http://i1020.photobucket.com/albums/af328/mcleodcarpentry/IMG00106-20100824-1300.jpg) is there a reference table that has some general wood characteristics such as compresion and shear or reflex strength?
I have a 6X48 belt sander and use 36 grit sandpaper to do my final thinning on a bamboo slat.
Before I had the 6X48 I used a elcheapo delta 4X36 to do the same thinning.
Don't understand your picture request. I space the nodes as evenly as I can on the top and bottom limb. I don't make allowances for nodes as far as limb profile goes.
My profile is about the same bow to bow. 1 1/4" wide to just past mid limb and then tapered to slightly narrower than 1/2" nocks.