Primitive Archer
Main Discussion Area => Bows => Topic started by: wally on May 01, 2011, 06:57:55 am
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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.)
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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.
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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
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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
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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.
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Did you wash the back before applying each successive layer?
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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.
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I assume,that with the bow being a short sinewed bow,that You meant to say,it is a Hupa style bow,init?
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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.
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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.
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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
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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
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Not traditional but you can glue the lifted sinew back down with crazy glue.
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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.
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Cyanoacrylate and it will bond the 2 layers without the need to clean them
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I agree with George. It's not rocket science. The more I work with sinew the more I realise this. I also reuse sinew from a broken bow. Soak it for a long time then use a comb to brush it out. First I would try and fix it though. I have never used crazy glue on sinew. It may work but sounds scary. You said you wash each layer of sinew before gluing? ??? Just lightly score with a hacksaw for better bonding.
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Here is pic.
First answer question Loefflerchuck. Some one asked me if I washed sinew before each layer but I said I didn't, in fact I'm not sure what they meant.
I'm going for a repair job.
Marc says cyanoacrylate glue is best to use, other say stick to hide glue?
I have nothing against using modern glues although instinct say use natural.
Any opinions
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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.
George
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Thanks for the tip, George. We learn something new all of the time with this hobby of ours. I'll have to try that!
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No problem Matt, and I really hope you don't have to remove sinew that way. It means a bow didn't work or broke and it's painful after all that work sinewing. On the other hand, bows protected by sinew are very durable if protected from moisture. I normally back them with snakeskin them to make them more weatherproof.
Wally, seeing your picture makes me more concerned. I thought the sinew just lifted, but it appears that one end has come completely loose, so it no longer has continuity. I'm anxious to hear Marc and the others with more experience comment. I'm in a bit of a quandary as to your best approach now. I wonder if you need to not only glue that piece down, but also add a little sinew over the top to tie it in?
George
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Not a good picture but it does look to me like it is not connected on the rignt side. How could that happen to a full 3 layers unless the sinew was not staggered? If it was just lifted I would say easy fix. Some Hupa bows had a solid rawhide wrap for a handle that would further strengthen this fix
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Yes it doesn't look good. The sinew was staggered and at the end that is free you can see the layering with some long and short pieces.
It first lifted by remaining in place, while the bow and first 2 layers seperated and bent more, then finally virtually broke free. It was still loosely tagged at that point but I easily freed it so it was completely loose.
I'm assuming that that layer was the weakest bonded, either through my bad mix of hide glue and water,or not so well placed on?
I'm still thinking that if I glue the flap down and cover it with more sinew, then transverse sinew it on top of that, about the handle area, and finally tiller the limbs down slightly so they take more bend?
At 19" it was pulling 48lb so I think it can come down more?
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First of all I didn't say the crazy glue was best to use, I said you can use it. It can be useful where the sinew has lifted but not enough that you can get in there and clean it properly for the repair. In this case it has lifted clear and you have access to the lower layer for cleaning. I would tug a bit on the sinew that has lifted to see if the rest of it will pull off. If it does so easily then it may be best to remove that layer completely and redo it. You would hate to repair that part just to have another section start to lift as you start tillering again. Obviously if you were in the process of tillering then you must not have a finish on the bow yet so re-using the sinew should not be a problem
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Marc has a good point. See if that whole layer wants to pull free. If it does. Redo the top 3 layers. You can doo em all at once to save time. If not. Soak the loose flap, reglue. layer more on top and wrap.
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Thats a very big lift up. You can fix and rap, most short bows were rap after tillering in places the whole way to prevent just this. The only problem this fixing a place of lifted so big the wood may not be reflex the way the rest of the bow will be. 7 Day between layers is fine as long as you don't flex the limbs between layers. I wait say 10 days reflex a few times between layers. Don't reflex to far are put unwanted stress on your limbs remember it's not tillered.
When finished I'd let it dry say 2 weeks before you finish the tiller. Then after since it's so short I rap with sinew at interments say every 2 inch's. Just to be safe. But you don't have to. Theres no hurry between layers or you might have the problems you have now. Plus I say 3 layers would be plenty. But take what I say with a grain of salt I've never made a bow that short. But I have seen 2 real plains bows and they were sinewed and then rapped and these rappings looked really heavy.
Like GSTONEBERG said it's a lot of work but with water and a hair dryer or the sun you can save all your sinew. It sucks but I've done it. Personally I'd re sinew like it said thats no small separation.