Osage and Bamboo Back had a splinter in it> Is it done for?

[ecounter]

Was shooting my Osage and Bamboo backed bow I completed a while back and a strip of a splinter of the bamboo split off the face.  It's not that deep about  9 inches long right on the curve and .75mm at the widest. after removing the splinter it it still pulls to length 28 @ 50#, no cracking noise.  I don't have enough experience with bamboo backing to know if its still going to function.  Love some input.
Thanks in advanced.

[bownarra]

A difficult one to answer.
1st thing do not pull it in this state!
If I really loved the bow and had to fix it - I would take a fine rasp, coarse file, scrapers and reduce the entire back. Removing the outer 'skin' of the boo and then sinew back to get the weight back to that of the original.
Rawhide would work too but you will lose a fair bit of weight reducing the boo to a safe state - hence why I'd use sinew. You can keep the weight as is and make it 100% tension safe.
This is the problem with boo....it can be great and last as long as anything else but sometimes it will lift splinters unexpectedly.

[Del the cat]

As it is entirely longitudinal you could chisel out the splinter fading it into a node at either end and then let in a strip of similar boo, glued with a suitable glue (TBiii etc). A lot of work to get it to fit perfectly, but it can be done.
Here's a post showing where I did something similar... it failed because the glue was a bad batch of Cascamite. I subsequently re did the repair successfully. It was a heavy bow 120# (the problem in the boo can be seen in the previous post on the blog)
https://bowyersdiary.blogspot.com/2020/05/not-my-best-work.html
Del

[Flntknp17]

I have a couple of boo backed bows that have done similar things.....since the crack does not run off the edge, my instinct says it'll be fine if you run some super thin CA glue in it and then bind at the nodes to prevent additional splitting.  Just my $0.02

[Eric Krewson]

I have ground off most the bamboo on a splintered back leaving just enough not to get into the old glue line and glued a new bamboo backing. Of course this requires a complete retillering and a poundage drop.

I suspect you could fill the void with superglue and fine sawdust and get by but I have never gone this route so am only guessing. That would be my first move, if this fix doesn't hold up you could always re-back the bow with new bamboo.

All the bows I re-backed with new bamboo were ones I made for other folk that popped a splinter on the back, because I always stood behind my bows I fixed them for them, all the bows I fixed many years ago are still shooting today.

Here are some pictures of my last replacement backing.

Grinding off the old bamboo, I use a belt sander.



All the old bamboo removed to right above the glue line.



New backing glued on in a reflex, removing the excess glue buggers.



This shows how much of the old bamboo I left.



Done, this is Chad Weavers bow.



The handle already had the finish on it, this picture is before I applied finish to the rest of the bow.



I ground off the old tip overlays while removing the bamboo and replaced them with new ones.

[Hamish]

Plenty of good advice from the fellas, I think they all would be successful options.

Here's my version.

If you still have the splinter and it is in one piece I would glue it back down, from where it came from. I would use urea formaldehyde, to give you your best chance of it not lifting again. (If you don't have the original splinter, I'd do as Del suggests.)

For double measure I would bind both ends of the splinter with silk thread, and then soak some CA glue, or epoxy to set the binding.

You could of course go the whole hog like Eric. He is the absolute master of bow repair. That is a lot of work, but if its an absolute favorite, it might be worth it. That being said you can make a really nice bow, you could probably make a new one, just as good, if not better.

[Gimlis Ghost]

Well I have no experience with bamboo , other that a bamboo fishing rid I had decades ago.
What I'm wondering though is just how likely it is that a splinter that narrow and in line with the grain would cause a failure?

Many Asian bows were tightly wrapped with bark or other materials to seal them. IIRC Ishi would tightly wind sinew around any suspect areas of his bows to prevent spliting or splinters raising up.

That is a certainly a fine looking bow, but as I heard recently "if you want to hear God laugh tell him you have a plan".

[bownarra]

The Asian bows were not tightly wrapped with birch bark they had a layer laid down over the back to cover the sinew. The bellies were often left bare as the horn needs no protection from moisture. The bark has nothing to do with structural protection.

The other thing to mention about the bow is that it appears to be tillered a bit 'funny' - too much bend inner limb right where your splinter raised.
Trying to do a fix on just the boo isn't going to fix the problem of WHY the splinter raised. I suspect it was because the bow is bending too hard there and not because the boo had a flaw. you will also have a weak limb with that section of the boo missing (indeed it is likely that limb was a shade weak to begin with).
Removing the boo and retillering is the way to go if you want it to last. the fixes mentioned won't stop the ends of the splinter lifting.
There are quick fixes and fixes that last!

[Eric Krewson]

More about my bamboo replacement and why I went this route; The bow has already been tillered and had even limb taper so gluing in very even reflex is easy, I probably spent 1/2 hour prepping the bamboo, 15 minutes gluing it on, 1/2 hour cleaning up the excess glue and sanding the bow, 1 hour gluing on new overlays and shaping them and probably 4 hours dropping the poundage, fine tuning the tiller and shooting the bow in. Of course applying stain and finish took a couple of days but my actual work was less than 1/2 hour, the rest was watching paint dry.

If I had started with scratch components to replace the bow it would have taken me a week or more.

[Gimlis Ghost]

The Asian bows were not tightly wrapped with birch bark they had a layer laid down over the back to cover the sinew. The bellies were often left bare as the horn needs no protection from moisture. The bark has nothing to do with structural protection.

Perhaps I should have said "Eurasian" as in birch bark wrapped Finn-Ugric laminated multi layer wooden bows and the Scythian bows wrapped entirely in a crisscrossing web of sinew.
The Ugric Birch wrappoing may have been intended only to offer minumum protection against rain reaching the fish glue and sinew bindings but It might have helped hold down any splinters that formed.

I've recently seen images of a Chinese bow sectioned for examination after it broke at the sinew wrapped grip. Glue applied during manufacture had partly filled in a deep lengthwise crack in the Bamboo layer present when that layer was cut . The bower seems not to have been concerned by the deep crack when making the bow, and apparently it lasted many years in service.
The crack in the bamboo doesn't seem to be the cause of the failure at the grip, rather it was excessive drying and shrinkage of the Elm build out.
https://atarn.org/chinese/visible_bow/visible.htm

[ecounter]

Thanks for the replies.  Bownarra that’s for pointing out the tiller and bend on inner limb.  Looks like I’ll repair w new boo and tiller outer limbs for more bend overall.

[Marc St Louis]

The other thing to mention about the bow is that it appears to be tillered a bit 'funny' - too much bend inner limb right where your splinter raised.
Trying to do a fix on just the boo isn't going to fix the problem of WHY the splinter raised. I suspect it was because the bow is bending too hard there and not because the boo had a flaw. you will also have a weak limb with that section of the boo missing (indeed it is likely that limb was a shade weak to begin with).
Removing the boo and retillering is the way to go if you want it to last. the fixes mentioned won't stop the ends of the splinter lifting.
There are quick fixes and fixes that last!

That is what I thought as well when I saw the braced pic