repair help on short Hupo sinew backed bow

[wally]

I'm making my first 36" Hupo bow and it was going great.
I put five layers of sinew on and was final tillering. I had only let cure for 2 weeks and the handle was taking too much bend, and instead of stopping I foolishly continued, and the hide glue gave and a section of sinew 1/8 thick (about top 3 layers) seperated from the lower layers, leaving a 6 ins flap hanging. AArgh!
Question. Is it safe to use hide glue to bond it back together, then re tiller it so more limbs bend rather than handle?
Or doI really have to remove all sinew and start again? Grr!
It was looking really good til it seperated and the wood base is intact O/K.
(Please say I can safely repair the lifted section.)

[toomanyknots]

Id think that'd be the safest way to fix it without just redoing the whole sinew. I wouldn't see why you couldn't just glue it back with some good hide glue let it cure then tiller er up.

[gstoneberg]

Wally,

I hope Eric and James Parker weigh in on this.  I haven't done any bows with that much sinew on them, though many with 2-3 layers. 

Did you put all 5 layers of sinew on at once?  I would expect 5 layers applied at one time to take months to fully dry and I would have expected it to fail the minute you started exercising it.  It must be very dry where you are, or it was done in multiple sessions, which is the way I always do more than 2 layers of sinew.  I honestly don't know the answer to your question.  If it were my bow I would try to get hide glue under where it popped off, wrap it again with an ace bandage which I'd remove after a day or 2.  Then I'd let the bow cure for about a month.  However, the set you've taken in the handle is likely there to stay.  If the 5 layers went on at once your bow may gain quite a bit of reflex as the sinew dries.

Again, I'd like to hear what the experts say though.  All I can offer is an opinion, they may have real experience.  Some pictures would help too.

Good luck.

George

[half eye]

Wally,
     I've seen Native American bows that were sinew backed, but that were also transverse wrapped with sinew besides that. Your problem MIGHT be why some of the orignials were done that way. Perhaps it was to prevent the very "lifting" that you experienced. Also did ya notice that even the Eskimo bows were transverse wrapped to position the main cable AND to shape the bow. Just some thoughts on the subject.......I never did a glued sinew bow back so this is just a supposition. But it would seem if you reglued the loose section and then put transverse wraps on that it maybe could not lift any more.
rich

[wally]

Thanks for replies so far. Very helpful.
I put the 5 layers on singly then let dry for 7 days before adding next. I don't think it needed five layers now, but read that hupo bows did have 5 layers.
36" is very short and it needs to bend a lot to get even 22" draw.
I may try regluing lifted part then transverse sinew around handle area. I'll wait for other opinions first.

[Marc St Louis]

Did you wash the back before applying each successive layer?

[loefflerchuck]

I would like to see a picture to help more. I have made a lot of short bows with heavy sinew backings. 5 layers is fine but I have found more than that actualy starts to slow the bow. Depending on where it lifted, you could try to soak the lifted part to stretch the fibers a bit. Try to roughen the sinew below it. Re glue it then wrap it in glued sinew. 7 days is enough time between layers, but I take a hacksaw blade and lightly score the sinew before the next layer. One last thing. The sinew was leg sinew, right? Back sinew may be too oily for such a heavy backing. Now lets see a picture.

[Traxx]

I assume,that with the bow being a short sinewed bow,that You meant to say,it is a Hupa style bow,init?

[Lee Slikkers]

I've never done a sinewed bow but I would wonder just how much good simply re-gluing that sinew down would do?  Most folk's put sinew on for added reflex and obviously for increased draw weight and to keep the back from failing.  I would think that simply gluing it down would only provide a weak bond (one layer of glue to the sinew) compared to it's original intent of layer glued to layer glued to layer, etc, etc.  But maybe I'm missing something?  I'm sure redoing the whole thing is the last thing you really want to do but if it was worth sinewing correctly the first time I think I'd reuse all the sinew and redo it from the ground up.

Good Luck and I hope it comes together for you.

[MWirwicki]

Well, you can't reuse the sinew.  There's really no way that I can imagine to reconstitute it. 

My feeling is that if you do find a way to glue your sinew flap down, the bow back likely won't have the entegrity it should have with multi-layers of sinew.  Part of applying multiple layers of sinew is to create random, interlocking locations of the seams.  If I am visualizing your tear correctly, by laying it back down and glueing it, you will have 3 layers of sinew in a location all with the same seam.  It will always be a vulnerable spot.  That Hupa style, short bow is put under a tremendous amount of tension and even if you wrap around the limbs I predict the repair will again separate at the 3-layered seam.  I agree that transverse wrapping during the initial construction of the bow is likely necessary, especially with 5 layers of sinew.  I don't feel that it will provide a failsafe remedy to the already compromised 3 layer tear. 

As far as removing all of the sinew and starting over with the sinew process, I would hesitate to use the same wooden core.  If the 3 layers of sinew tore, I would think that the core wood suffered some damage, as well.  Rather than putting more time and material into this bow, I think that I would consider it a learning experience and start over.  Like the others mentioned, a picture would be interesting to see.  A picture might help identify what went wrong.  Afterall, you could use a combination of all of the advice in this thread but if you don't identify the original cause of the failure, if not corrected you may be in the same danger on your next attempt. 

[wally]

Thanks for all useful comments. Just to answer a few queries. I didn't wash it between layers just laid more hide glue soaked sinew. It was deer leg sinew.
And yes I meant Hupa style bow.
It seems I may have start again and learn from it, but I might try repair as I've got nothing to lose, and if it fails again I'll start again then.
I'll take a photo soon  so it's clear what happened.
The thought of preparing all that leg sinew again is disheartening
Still I've got to finish it one way or another

[gstoneberg]

Well, you can't reuse the sinew.  There's really no way that I can imagine to reconstitute it. 

I'm sorry, but that is simply not true, provided the sinew is not covered with a finish.  Hide glue is water soluble and when a bow with hide glue is soaked in water the glue dissolves and the sinew releases from the wood.  In time it can be easily removed from the bow, dried and reused.  I have done it, and it works fine. 

I don't see why the piece that has come loose wouldn't continue to work correctly as long as it was wrapped.  Eskimo bows use a sinew cable on their back and they work fine not glued to the bow back, just held in place with a wrap.  However, I would still try to glue it down just to make it more secure.

George

[Marc St Louis]

Not traditional but you can glue the lifted sinew back down with crazy glue.

[wally]

crazy glue?
We don't have that in UK. Is it a 2 part epoxy? What is similar glue?
What advantage over using hide glue again?
It sounds like a good solution though.

[Marc St Louis]

Cyanoacrylate and it will bond the 2 layers without the need to clean them