first sinew back -- Advice!

[Bearded.Jake]

Hello all,

I decided to try sinew backing a short piece of juniper I had that came off a bigger stave.  I figured it would be good practice for my first attempt and didn't have and expectations, but its funny now that I've put a bunch of time into it, I really want it to work out!!

it is only 41" long and 1 3/8" wide in the middle tapering out too the tips. I have only put one layer of sinew on and it was a mediocre job. I had a hard time keeping my bundles straight and having some of the ends of sinew strands bunch up. I also have some very small gaps here and there.  Partly I think it was from being rushed because the glue seemed to be setting too fast. I think it was too thick.
 
I am wondering what you all think, and if those issues with the sinew job will not adequately strengthen the bow to keep from breaking. I have put ~45lbs of force on it multiple times tillering already.
There are also a few longitudinal cracks running off at one tip which I have glued with hide glue and clamped. I was planning to wrap both ends with sinew, but wondering if its worth the effort.

Thanks for any help!

sorry I know the photos aren't the best.

[Pat B]

Looks pretty good to me. I use shorter pieces of sinew to fill the bare spots. Once it looks dry and the voids are filled you can sand the sinew surface to make it a bit smoother. Then cover all the sinew with a light coat of glue to flatten out the hairy sinew.

[Bearded.Jake]

Looks pretty good to me. I use shorter pieces of sinew to fill the bare spots. Once it looks dry and the voids are filled you can sand the sinew surface to make it a bit smoother. Then cover all the sinew with a light coat of glue to flatten out the hairy sinew.

Thanks Pat! I really appreciate the advice!

[superdav95]

Looks good to me too.  I do see some cross crossed sinew fibers but should be ok.  Pats advise is good

[Bearded.Jake]

Thanks Superdav!  Glad to have more opinions!  I sanded smooth,  put a little more glue over top and then wrapped the tips today! 

I am hoping the shoulders for the nocks will be big enough once it drys, I used up the last of my glue so couldnt add any more sinew today.

[pierce_schmeichel]

I would personally add one more layer but that single layer will probably work out!
If you do decide to add another layer make sure you wet the sinew on the bow before you put the new stuff on. If you don't wet the surface you will have issues with the sinew delaminating from each other. I wet it by laying some wet paper towels over it for 5 minutes or so and that does the trick. Good luck!!

[Pappy]

Looks good to me and love the sinew nocks. 
 Pappy

[superdav95]

Those turned out nice!   Well done. 

[Bearded.Jake]

sweet, thanks guys! Im excited to get a string on it!

Pierce,  I also would have liked to put another layer on.  But a combination of not having prepared enough sinew and glue and not knowing if the first layer was going to be any good made me stop with just one for now.  The small amount of backset that the sinew did create is mostly gone already from a bit of tillering.  Oh well, if it seems worthwhile later on maybe ill add another layer!  Thanks for the tip about re wetting the sinew!

[uwe]

I wonder why you have problems in having the sinew straight.
Didn' t you put it long enough into cold water or what I do not expect, was the hideglue too hot. In this case the sinew is wrecked.
When I have prepared the sinew for backing , I' m making bundles of pencil thickness, about 8 single  strings and store it between newspaper pages, old magazines.
So it can already get slightly straight until its used.
Other aspect could be that your sinew is still too thick and cannot get straight in combination with too short watering.
Another issue is, which tendons you' re using. Bison is very soft, when pulled out and deer is harder stuff.
Hope this will be useful!
Uwe

[superdav95]

Jake.  Lookin at your unbraced profile now you could add another layer or bundle for each limb on the inner fades out to mid limb or longer depending on what length you got.  I would scuff up you bow a bit before and clean well.  I’ve used various methods for laying down sinew and have landed on my preferred method of a well combed and flattened bundle that has been soaked cleaned of all the little extra bits.  I soak and have them pre measured for weight dry before as well.  This gets me close to same for both limbs.  I do overlap my layers much like I do for composite horn bow build and then place final long layer to cover the overlapping.  I separate my long strands for this.  This has worked very well for me.  I find that doing it this way I get pre weighted bundles that are flatted to the same width as my bow that are laid down in same sequence.  Predictability is the benefit.  I tend to put more at the inners from fades out to about mid limbs then the rest.  Depending on the build and size of bow will determine amount of sinew.  Doing it this way my tiller doesn’t change much and bend still remains good for most part.  Hope this helps. 

[Bearded.Jake]

Thanks guys,  I appreciate the feedback.. an update on the bow: although it was risky and the smart thing to do would have been wait to put more sinew, I began taking some shots after getting a string on it.  I was drawing about 18-19" and the weight was around 35lbs I think.  Alas, the bow exploded into about eight pieces and brought an end to my first sinewing experiment.  As much as I was wanting it to work out, I am glad it wasnt a bow I was hoping to hunt with.

uwe,  I only soaked my bundles in the hot glue, no cold water.. is it better to soak in water first?  Also, I dont think the glue was too hot, the sinew didn't shrivel up or anything.  I was actually worried that I had split my sinew too thin, because by the time I got all the excess stringy bits off most pieces, they were always quite thin. 
I think mainly, I just didnt comb them out well enough before dipping in glue. The sinew was from the legs of whitetail deer.

Superdav,  I definitely should have been more patient and added another layer of sinew.  My first problem I think, was the design of the bow with what I had to work with was not very good. Such a short bow, the recurves should have been shorter perhaps? Or thinned before I put the wrapping on to allow this portion of the bow to do more work? At any rate, Ill keep your advice in mind for my next attempt, thank you!

Maybe I will add some pics of it drawn and braced before it broke if anyone is interested at all.

Cheers

[superdav95]

Always here to help where I can.  I assume this was a wood failure and not a sinew issue???   The sinew will somewhat protect a compromised back but should not be solely relied upon to save the bow or make up entirely for bad wood.  Sinew can only do so much.  In fact I’ve found that the core wood has to be of sufficient strength and quality to handle the stresses placed on it by adding sinew to its back.  Sinew is obviously more elastic and forgiving to some other backing for sure but still adds stresses that we’re not there before.  Sinew works best in conjunction with a good belly that’s good in compression strength (the best being horn).  Even softer woods like yew and junipers can be great in compression and benefits from sinew.  I always try to put the “neutral plane” within the limb at a point that falls within core wood and not my glue line.  To explain my reason may be longer winded answer but essentially the weak point within the limb most likley is the glue line.  So doing a half thickness of sinew to wood (depending on the wood) may put neutral plane right at the glue line and cause a delaminating to occur.  In your case here I believe your wood failed and not necessarily the sinew.  I could be wrong but sinew is quite strong and less likley the culprit.  Think of it as a bow enhancement.  The bow wood has to be good still to survive tiller, brace and shoot in.   How well this is done and the quality of the bow wood varies wildly and can be shown in set or explosion.  The sinew may very well save a somewhat compromised back of an otherwise good belly wood bow but can’t save a a bow that is destined to fail if that makes any sense.  lol.  I would soak you sinew and salvage it for next one.  Comb it really well and get it good and clean.  In my salvage of failed sinew projects I comb the sinew very thing to almost a single layer getting fibers good and straight on a boards to let dry.  It will curl up a bit but that’s fine.  I aim for about the thickness of backstrap from deer.  When dry I will weight it all and separate into matching lengths piles.  I then put into ziplock bags till I use it.  There is no one way on this stuff but I’ve found this method works for me and works with my ocd brain.  Best of luck keep us posted. 

[Doug509]

Can I Hi-jack?
I'm starting my first sinew backing and as I pound and pull tendons into strips of sinew I have a few questions.  After pulling into 1-2mm wide strips do you then wash in soap to remove fat or oil?  Soak in water and scrape and clean with the back of a knife or comb?  Or do I just pull sinew and keep it dry until backing the bow?  Just how anal do I need to be in preparation?  Dave mentioned he preferred method of a well combed and flattened bundle that has been soaked cleaned of all the little extra bits then dried flat until ready to use.

Prepping the bow.  I'm sizing with a hacksaw blade to create lengthwise grooves.  clean with Acetone then lay down 3 layers of hide glue.

When ready to back the bow.  Do we wet the sinew in water, then hide glue then lay straight as possible only overlapping the ends vs crossing strands in a random woven pattern
thanks

[superdav95]

Can I Hi-jack?
I'm starting my first sinew backing and as I pound and pull tendons into strips of sinew I have a few questions.  After pulling into 1-2mm wide strips do you then wash in soap to remove fat or oil?  Soak in water and scrape and clean with the back of a knife or comb?  Or do I just pull sinew and keep it dry until backing the bow?  Just how anal do I need to be in preparation?  Dave mentioned he preferred method of a well combed and flattened bundle that has been soaked cleaned of all the little extra bits then dried flat until ready to use.

Prepping the bow.  I'm sizing with a hacksaw blade to create lengthwise grooves.  clean with Acetone then lay down 3 layers of hide glue.

When ready to back the bow.  Do we wet the sinew in water, then hide glue then lay straight as possible only overlapping the ends vs crossing strands in a random woven pattern
thanks

Hey Doug.   In my previous post about I was specifically speaking of salvaged sinew only when soaking it and flattened bundles and letting dry for next project.  Hope that clarifies.  As for what you’re doing now I would separate your pounded bundles of sinew into as fine a threads as you can get.  I use my fingernail or thumbnail to strip the length of the strands of as much of the extra little bits I can.  This is time consuming for sure but is the best way I’ve found as I separate into corresponding piles of similar length bundles.  I keep doing this till I get a sufficient amount ready to go for my project.  I do use metal pull combs or a board with a bunch of finish nails hammered in as a stiff comb.  I’ll also use a wire brush too.  Dog combs work good too.  I do this all dry.  Then I weight it all and separate it into planned bundles for each limb.  Others have had good success with laying tiny little bundle of about 10 single strands and staggering them.  I have done this on a few but personally found the measured flattened bundles in a sequence of planned layers the best.  Anyway once you get your fibers all dry worked and separated and measured this is when you soak and clean with mild dish soap like dawn.  I soak my measured bundles all day while I get the bow sized with 5-10% very thin hide glue.  I also heat up my surface with radiant heat and make sure the fine grooves are clean of debris.  I do not use acetone on my sinew bows.  It’s just me but don’t want anything to interfere with my sizing coats.  I also do at least 8-10 size coats generally.  I did have a yew bow a while back that needed 12 coats. It finally shined up and was good to go.   The reason for the very thin hide glue is to penetrate deep into the open pours of heated wood.  If thick glue is used for sizing the adhesive quality won’t be as deep.  Overlapping sinew bundles is a good idea.  Use you long strand layer for final layer to tie it all together and cover over any overlaps.  Hope this helps.